x
Our website uses cookies. By using the website you agree ot its use. More information can be found in our privacy policy.

Conferences

For a simple text search, enter your search term here. Multiple words may be found by combining them with AND and OR. The text in this field will be matched with items' contents, title and description.

  • *ALE_STRUCTURED_FSI The New S-ALE FSI Solver

    Hao Chen (Ansys Livermore)

    The LS-DYNA® Structured ALE solver is developed in 2015. It is faster and more stable; uses less memory and storage; its input format is cleaner and much less confusing. It has been well received by users studying behavior of fluids, and especially their interaction with structures. During the past two years, the author worked on a new fluid-structure interaction (FSI) package dedicated to be used with S-ALE solver. The objective is to shorten the running time, stop leakage, and make the input deck user friendly. In this paper this new FSI package, together with its keyword -- *ALE_STRUCTURED_FSI is introduced.

  • *MAT GAS MIXTURE, a new gas mixture model for airbag applications

    Lars Olovsson - LSTC

    Recent efforts to model fully coupled CFD-airbag processes have motivated the implementation of a gas mixture model in LS-DYNA. The new model, *MAT GAS MIXTURE, allows the mixing of up to eight different gases. It is designed to conserve the total energy of the system. Kinetic energy dissipated in the ALE advection process is automatically transformed into heat. The article serves as a description of the gas mixture model and of the accompanying keyword commands.

  • *MAT_4A_MICROMEC – Theory and Application notes

    P. Reithofer, A. Fertschej, B. Hirschmann, B. Jilka, 4a engineering GmbH;, A. Erhart, S. Hartmann, DYNAmore GmbH

    Nowadays a great number of short and long fiber reinforced thermoplastics play a decisive role in the automotive industry to ensure affordable lightweight design and availability in large quantities. As seen in the last German LS-DYNA® Conference 2016, there is a strong industry interest to consider the manufacturing process induced local anisotropy in crash and general dynamic simulations.

  • *MAT_PAPER and *MAT_COHESIVE_PAPER: Two New Models for Paperboard Materials

    Jesper Karlsson, Mikael Schill 1 (DYNAmore Nordic), Johan Tryding (Tetra Pak)

    We here present two new material models for the modeling of paperboard materials. The main motivation for the models is to accurately simulate the production of food and beverage containers for the packaging industry. The main material, *MAT_PAPER, is an orthotropic elastoplastic model that supports both solid and shell elements. In conjunction, an elastoplastic cohesive material, *MAT_COHESIVE_PAPER, is introduced to simulate delamination. Simulations of bending and creasing of paperboard using these new materials, performed in collaboration with Tetra Pak, has shown good correlation with experimental results

  • 2D to 3D ALE Mapping

    Nicolas Aquelet - Livermore Software Technology Corporation, Mhamed Souli - Laboratoire de Mecanique de Lille

    A 2D MMALE (Multi-Material Arbitrary Lagrange Euler) code was implemented in LS-DYNA®. Like the 3D MMALE already available each 2D computational cycle is divided in two steps. First a multi-material version of the two-dimensional shell formulations solves the physical problem on quadrangle meshes during the Lagrangian step. The 2D shell formulations are plane strain and area-weighted axisymmetric. An advection step adapted to the 2D shell approaches follows to control the mesh motion. 2D ALE data of the last cycle can be mapped on 3D ALE mesh. Data are stored in a file defined on the command line after the prompt “map=”. This file is read for the 3D model with the same command line.

  • 3-Dimensional Forming of Thick Plates - A Comparison of Deep Drawing and an Approach of Rolling and Bending within a Single Process

    Manuel Bojahr, Hannes Prommer, Ralf Tschullik, Patrick Kaeding - University of Rostock

    A variety of industries require certain 3-dimensional formed thick plates, for example in shipbuilding for shell plates. Nowadays the production of curved ship plates is mainly based on the experience of the worker and is performed manually. The results are good and sufficient for the heretofore use in industry, taking into account that the number of curved plates with the same geometry is quite small. Moreover thick plates with a variable thickness are used for instance as so called longitudinal profiles for bridge building. Currently the combination of curved plates with variable thickness does not meet a wide range of applications. But it has high potential in future. In modern shipbuilding this kind of plates offers special applications with a broad scope, e.g. reduction of weight. Renewable energies are another huge market in future. Today, wind turbines are mostly made of glass or carbon fiber. The manufacturing process leads to high precision and quality of the final product. Nevertheless, this fabrication method of rotor blades is very cost intensive and its production technology is not the best in terms of recyclability. In addition to its good reusability, the handling of steel is well known and its fabrication is inexpensive. Due to these facts an idea of rotor blades to be produced from steel arose. However, when desiring a huge output of a product with the same geometry a manual approach is inappropriate. A new process should be repeatable and within a certain accuracy. Deep drawing of the product is a natural choice but is not used for thick plates of enlarged sizes until now. This paper presents a comparison of deep drawing and a new approach. The developed process is based on a superposition of flat rolling and 3-dimensional bending. A major advantage of combining these steps is the opportunity to deliver formed plates with a variable thickness. This paper presents numerical simulations of deep drawing and rolling processes. The results are compared in terms of practicability for the production of rotor blades.

  • 3D Numerical Simulations of Penetration of Oil-Well Perforator into Concrete Targets

    Qiankun Jin, Zheng Shigui, Gary Ding, Yianjun, Cui Binggui - Beijing Engineering Software Technology Co., Ltd.

    The oil-well perforator and its interaction with concrete targets are simulated with fluid-structure coupling algorithm and the new mesh motion option of the multi-material ALE formulation of LS-DYNA[1] in Version 960. Comparison of the simulation results to the experimental test data has been conducted. The simulation results show good correlation with data in tests and indicate that LS-DYNA can be used as an engineering tool to help in the prediction of perforation depth.

  • 4a impetus - efficient evaluation of material cards for non-reinforced and reinforced thermoplastics

    Peter Reithofer, Martin Fritz, Reinhard Hafellner - 4a engineering GmbH

    LS-DYNA© has included plenty of material cards, each of them offering different scalability and complexity to describe the behavior of non- reinforced thermoplastics. The consideration of the strain rate behavior is included in many material cards, e.g. in the well known MAT_PICEWISE_LINEAR_PLASTICITY. More complex material models can also handle varying compression and tension behavior as well as unloading by using damage functions. One of the recent development results is MAT-SAMP-1 by Du Bois, Kolling, Feucht and Haufe. This specially developed material model for polymers includes a yield surface out of different loading cases and a damage function for better description of unloading. For better use of the above mentioned models a huge amount of tests have to be carried out, to determine the material parameters and to represent the thermoplastic characteristics in crashworthiness simulations. 4a impetus builds up an efficient and reliable process, starting with realistic tests and finally ending up with a validated material card. Recent developments of new test methods for 4a Impetus are presented, that satisfy the needs of complex material models as well as the expectations with regard to easy and favorable testing. Limits and opportunities of different test methods and material card implementations are shown and compared to each other especially focused on typical polymer behavior. Finally the influence of fiber reinforcement is discussed and solutions to determine material parameters by using micro mechanic models (4a MicroMec) are shown.

  • 4a impetus - efficient evaluation of material cards for non-reinforced and reinforced thermoplastics

    Peter Reithofer, Martin Fritz, Reinhard Hafellner - 4a engineering GmbH

    LS-DYNA© has included plenty of material cards, each of them offering different scalability and complexity to describe the behavior of non- reinforced thermoplastics. The consideration of the strain rate behavior is included in many material cards, e.g. in the well known MAT_PICEWISE_LINEAR_PLASTICITY. More complex material models can also handle varying compression and tension behavior as well as unloading by using damage functions. One of the recent development results is MAT-SAMP-1 by Du Bois, Kolling, Feucht and Haufe. This specially developed material model for polymers includes a yield surface out of different loading cases and a damage function for better description of unloading. For better use of the above mentioned models a huge amount of tests have to be carried out, to determine the material parameters and to represent the thermoplastic characteristics in crashworthiness simulations. 4a impetus builds up an efficient and reliable process, starting with realistic tests and finally ending up with a validated material card. Recent developments of new test methods for 4a Impetus are presented, that satisfy the needs of complex material models as well as the expectations with regard to easy and favorable testing. Limits and opportunities of different test methods and material card implementations are shown and compared to each other especially focused on typical polymer behavior. Finally the influence of fiber reinforcement is discussed and solutions to determine material parameters by using micro mechanic models (4a MicroMec) are shown.

  • 10th International LS-DYNA® Users Conference 2008
  • 18 Wheel Truck Dynamic and Durability Analysis using Virtual Proving Ground

    Ramesh Edara, Shan Shih - ArvinMeritor Inc., Nasser Tamini, Tim Palmer, Arthur Tang - Engineering Technology Associates

    Virtual proving ground (VPG) simulations have been popular with passenger vehicles. VPG uses LS-DYNA® based non-linear contact Finite Element analysis (FEA) to estimate fully analytical road loads and to predict structural components durability with PG road surfaces and tire represented as Finite elements. Heavy vehicle industry has not used these tools extensively in the past due to the complexity of heavy vehicle systems and especially due to the higher number of tires in the vehicle compared to the passenger car. The higher number tires in the heavy vehicle requires more computational analysis duration compared to the passenger car. However due to the recent advancements in computer hardware, virtual proving ground simulations can be used for heavy vehicles. In this study we have used virtual proving ground based simulation studies to predict the durability performance of a trailer suspension frame, tractor suspension frame and combination of both frames with 18 wheel on a given PG event. The virtual proving ground was also used to predict the stress, strain time histories, spindle loads and the component fatigue life for the given PG event.

  • “Forming to Crash” Simulation in Full Vehicle Models

    Janka Cafolla, Roger W. Hall, David P. Norman, Iain J. McGregor - Corus Automotive

    Improving the accuracy of virtual prototypes helps to shorten product development times and reduces the number of physical prototypes required. One way in which the accuracy of crash analysis can be improved is to include the effects of forming in the material properties. Corus has developed a three-step “Forming to Crash” process to account for formed properties in crash analysis during both concept and detailed vehicle design stages. The first step uses a selection procedure to identify the parts most sensitive to the inclusion of formed properties. The second step uses an approximate “Forming to Crash” method to rapidly estimate the formed properties and reduce the time taken to conduct the analysis during concept design. The third step links a detailed forming analysis to a crash analysis to provide a full “Forming to Crash” technique for use during detailed design development. This three-step process is used by Corus to support customers in the application of advanced high strength steels. Introduction The process of forming a component changes the properties of the material being used. This is generally ignored in the design and validation process of automotive structures even though the changes in material strength and thickness may be substantial. Finite Element tools are now able to predict the as-formed material properties and use these in subsequent crash analysis. However, although the forming effects on the performance of individual components have been reported in the literature [1][2][3][4][5][6][7][8], there are few papers reporting the consequence of including formed properties in full vehicle models [9][10]. This paper presents Corus developed procedures, which are used to include the results of forming simulations in the full vehicle crash model. Corus “Forming to Crash” Three-Step Process A vehicle body structure consists of hundreds of formed components. A detailed analysis of the stamping process can take between 5 to 10 days per part to complete. In order to minimise the time taken for vehicle analysis, it is therefore important to understand which components in the vehicle body structure are sensitive to forming and how the formed properties affect the vehicle crash performance. The identification of the key parts in which to include formed properties is the first stage of a “Forming to Crash” (F2C) three-step process, which has been developed by Corus.

  • A 3D Discontinuous Galerkin Finite Element Method with the Bond-Based Peridynamics Model for Dynamic Brittle Failure Analysis

    W. Hu, B. Ren, C.T. Wu, Y. Guo, J. Wu (LSTC)

    Peridynamics is a new nonlocal theory that provides the ability to represent displacement discontinuities in a continuum body without explicitly modelling the crack surface. In this paper, an explicit dynamics implementation of the bond-based peridynamics formulation is presented to simulate the dynamic fracture process in 3D elastic solid. Based on the variational theory, the Discontinuous Galerkin (DG) approach is utilized to formulate the classic peridynamics governing equation. As a result, the spatial integration can be carried out through finite element approach to enforce the boundary conditions, constraints, contacts as well as to handle the non-uniform mesh in the engineering practices. The classic material parameters, such as the elastic modulus and fracture energy release rate are employed for the determination of material response and failure in brittle material. Several numerical benchmarks are conducted to invest the convergence and mesh sensitivity of simulations of dynamic crack propagation process with different refinements. The results demonstrate that the proposed peridynamics formulation can capture the 3D dynamic crack process in brittle material effectively and accurately including multi-crack nucleation, propagation and branching.

  • A 6 Year-Old Pediatric Finite Element Model for Simulating Pedestrian Impacts

    Yunzhu Meng, Costin D. Untaroiu (Virginia Tech, virginia Tech-Wake Forest Center for Injury Biomechanics), Berkan Guleyupoglu, Bharath Koya, Scott Gayzik (Wake Forest University School of Medicine, Virginia Tech-Wake Forest Center for Injury Biomechanics)

    In addition to adult pedestrian protection, child pedestrian protection continues to be an important issue in vehicle crash safety. However, with exception of a child headform impact test, all other subsystem tests are designed for prediction of adult pedestrian injuries. The development of a computational child model could be a better alternative that characterizes the whole-body response of vehicle–pedestrian interactions and assesses the pedestrian injuries. Several pediatric pedestrian models have been developed but these existing models have several inherent limitations due to lack of biomaterial data. In this study, an advanced and computationally efficient finite element (FE) model corresponding to a six-year-old (6YO) pedestrian child was developed in LS-DYNA. The model was developed by morphing an existing GHBMC 5th percentile female pedestrian model to a 6-year old child geometry reported in literature. Material properties were applied based upon previously published studies. The standing posture has been used as specified in the EuroNCAP testing protocol. Component validations with simple impactor tests and a full-body validation in a car-to-pedestrian collision (CPC) were performed in LS-DYNA. Overall, the results of the model showed a reasonable correlation to the test data in component validations. The child pedestrian model showed also numerical stability under a typical CPC configuration. In addition, the most common injuries observed in pedestrian accidents including fractures of lower limb bones and ruptures of knee ligaments were predicted by the model. The child model will be further validated and then used by safety researchers in the design of front ends of new vehicles in order to increase pedestrian protection of children.

  • A Benchmark Study of CAE Sensor Modeling Using LS-DYNA

    C. C. Chou, P. Chen, J. Le - Passive Safety R&A, Ford Motor Company, Nasser Tamini - ETA

    This paper presents results from a benchmark study of CAE sensor modeling using LS-DYNA. Using the VPG translator, a sensor model was converted from a calibrated RADIOSS model into LS-DYNA input formats for frontal impact simulations carried out in this study. Since two codes have different material laws, element library and functionalities, those deemed to be as closed to RADIOSS were chosen in the translation process. For those that could not be translated directly into LS-DYNA, best engineering judgment was made in selection of appropriate LS- DYNA parameters. Three different frontal impact modes, namely, rigid barrier, pole, and Thatcham offset are simulated in this study. In frontal rigid barrier mode, both 90o barrier and 30o angular impacts are considered. Signals at nine (9) locations were monitored including two sensor signals obtained at the front crash sensor (FCS) and Restraint Control Module (RCM) locations. The quality of CAE data was evaluated using an assessment tool to give objective ratings for comparing results between LS-DYNA and RADIOSS. Sensor signals generated from LS-DYNA were compared with both the RADIOSS and test results. However, only the comparisons with RADIOSS results are presented. By comparing the ratings, LS-DYNA results were, generally speaking, comparable with RADIOSS’ counterparts. Observation of some high frequency response at the onset of acceleration time history obtained at the front crash sensor location at the early stage of this study was improved by LSTC. The study also pointed out areas, i.e. angular and Thatcham impacts, where the LS-DYNA model requires further improvement in the future

  • A Brief Look at *MAT_NONLOCAL: A Possible Cure for Erosion Illness?

    Leonard Schwer - Schwer Engineering & Consulting Services

    The computational mechanics literature dealing with damage and failure is filled with work addressing what is termed mesh regularization techniques. These various techniques seek to eliminate, or minimize, the numerical artifact of strain localization. LS-DYNA® provides a technique for attempting to regularize meshes with damage and failure via the keyword *MAT_NONLOCAL. The non-local implementation in LS-DYNA is based on the work of Pijaudier-Cabot and Bazant (1987). The non-local treatment basically attempts to average damage/failure values of neighboring elements to minimize the mesh dependency of the results.

  • A Brittle Damage Model: Implementation into LS-DYNA and Application to Normal Plate-on-Plate Impact

    Martin N. Raftenberg - U.S. Army Research Laboratory

    A brittle damage model developed by M. A. Grinfeld was implemented in the LS-DYNA finite element code and applied to the simulation of normal plate-on-plate impact. The model introduces a state variable measure of damage that evolves in proportion to the elastic strain energy. The model degrades the elastic shear modulus in proportion to the state variable’s current level. The implementation procedure by means of the LS-DYNA user- material interface is described. In a simulation of normal plate-on-plate impact, the model produced a gradient in elastic properties within the initially homogeneous target, and this gradient led to a partial reflection of the unloading wave. For a range of values for the material constants introduced by the damage model, the target’s free-surface velocity showed a gradual increase over time following the arrival of the initial compressive shock. This observation is discussed in light of the phenomenon of failure waves.

  • A Cohesive Element Model for Large-Scale Crash Analyses in LS-DYNA ®

    Johan Kolstø Sønstabø, David Morin, Magnus Langseth (SIMLab and CASA)

    In a recent study the cohesive element model *MAT_240 was evaluated for macroscopic modelling of two different Flow-Drill Screw (FDS) connections in large-scale analyses [1]. The study showed that *MAT_240 does not have sufficient flexibility to describe the macroscopic behaviour of the connections. In particular, the force level and initial stiffness in mixed-mode loadings were severely over-estimated. The lack of flexibility to control the mixed-mode behaviour was also pointed out by Sommer and Maier [2], who investigated self-piercing rivet connections. This paper presents a new cohesive element model for use in LS-DYNA. The model is based on *MAT_240, presented by Marzi, et al. [3], with added flexibility to control the behaviour under mixed-mode loadings.

  • A Cohesive Model for Ice and its Verification with Tensile Splitting Tests

    H. Herrnring, L. Kellner, J. M. Kubiczek, S. Ehlers (TUHH)

    Ships and offshore structures operating in areas such as the Arctic have to be designed to withstand ice induced loads, e.g. from ice floe impact. This is mostly done with empirical methods, which have several drawbacks, e.g. they only give upper estimates of global loads. Numerical simulations of ice interaction are a desirable remedy, but their accuracy is currently limited if the material model doesn’t account for fracture processes. One approach is to use an elastic bulk material model along with the cohesive zone method (CZM) to model all inelastic deformation, i.e. fracture. Here, this approach is applied to simulate tensile splitting tests. The focus is on parameter identification and numerical instabilities for fine discretizations.

  • A COMPARATIVE REVIEW OF DAMAGE AND FAILURE MODELS AND A TABULATED GENERALIZATION

    P.A. Du Bois - Consulting Engineer, Germany, S. Kolling, M. Feucht - DaimlerChrysler AG, Germany, A. Haufe - Dynamore GmbH, Germany

    Reliable prediction of damage and failure in structural parts is a major challenge posed in engineering mechanics. Although solid material models predicting the deformation behaviour of a structure are increasingly available, reliable prediction of failure remains still open. With SAMP (a Semi-Analytical Model for Polymers), a general and flexible plasticity model is available in LS-DYNA since version 971. Although originally developed for plastics, the plasticity formulation in SAMP is generally applicable to materials that exhibit permanent deformation, such as thermoplastics, crushable foam, soil and metals. In this paper, we present a generalized damage and failure procedure that has been implemented in SAMP and will be available in LS-DYNA soon. In particular, important effects such as triaxiality, strain rate dependency, regularization and non-proportional loading are considered in SAMP. All required physical material parameters are provided in a user-friendly tabulated way. It is shown that our formalism includes many different damage and failure models as special cases, such as the well-known formulations by Johnson-Cook, Chaboche, Lemaitre and Gurson among others.

  • A Comparative Study of Modeling Approaches for External Structures in Mine Blast Simulations of an Armored Military Vehicle

    İsmet Kutlay ODACI, Samet Emre YILMAZ, İlker KURTOĞLU

    External structures are known to be critical in ensuring the protection of occupants in military vehicles during mine blast events. There are variety of modelling approaches that can be employed to represent external structures in mine blast simulations of armored military vehicles. This study aims to present an accurate configuration considering the modelling efforts and tight project schedules by comparing different modeling techniques applied to external structures, such as add-on armor plates and other external subsystem components. A whole vehicle finite element model is utilized for an on-going research and development project to evaluate the effectiveness of these modeling approaches by comparing simulation results with live fire test data of Hybrid III dummy and plastic deformations of the hull structure. The findings emphasize that the modelling approach of not only primary protective structures but also other external components significantly contributes to better representation of the tests. Configurations featuring accurately modeled external structures demonstrate improved accuracy in occupant safety assessment. The outcomes of the study contribute to enhancing the efficiency and reliability of the conceptual design phase by providing faster and relatively reliable finite element solutions, specifically in terms of representing external structures in the simulations.

  • A Comparative Study of the Hexahedral Elements in LS-DYNA for Crashworthiness Simulation

    S. E. Hoque, S. Scheiblhofer, S. Ucsnik (LKR Leichtmetallkompetenzzentrum Ranshofen)

    The mesh behaviour and convergence rate of six hexahedral element formulations in LS-DYNA were investigated by means of crashworthiness simulation. The element formulations are: constant stress solid element (ELFORM 1), fully integrated S/R (Selective Reduced) solid element (ELFORM 2), fully integrated S/R solid element with reduced transverse shear locking (ELFORM -1 and ELFORM -2), 20-noded serendipity element (ELFORM 23), and 27-noded fully integrated S/R quadratic solid element (ELFORM 24). FE-simulations of the axial crushing of aluminium profiles were set up with these element formulations. The convergence rate of each element formulation was investigated by varying the mesh resolution. For validating the simulation results, four extruded profiles with rectangular hollow cross-sections were experimentally tested under quasi-static axial crushing load. On that basis, the performance of each element formulation was investigated in terms of their convergence rate, accuracy, and computational cost to elaborate an approach for future tasks. Finally, various aspects which should be considered while using these element formulations for this class of problem are discussed.

  • A COMPARISON BETWEEN EXPERIMENTAL TESTING AND NUMERICAL SIMULATIONS OF IMPACT LOADING ON ALUMINUM AND MAGNESIUM STEERING WHEEL ARMATURES

    William J. Altenhof - The University of Windsor, William D. Ames - K.S. Centoco Limited

    In the present automotive industry, all corporations are focusing on developing automobiles which are light weight, fuel efficient, conform to a level of safety outlined by government regulations, and are available to the consumer at a reasonable cost. The automobile industry has placed a significant amount of time and research funding into developing vehicles which can meet these requirements. K.S. Centoco Ltd., a steering wheel manufacturer, located in Windsor, Ontario, Canada, has developed a testing machine to investigate collisions occurring with steering wheels. This machine considers several experimental parameters in impact testing while providing a large amount of information to be obtained in an experiment. Experimental testing was conducted on a four spoke steering wheel armature which is manufactured from a magnesium alloy. In an effort to compare the structural worthiness of magnesium and aluminum alloys in an impact situation, the identical armature was fabricated from a proprietary aluminum alloy and impact experiments were also conducted with the geometrically identical aluminum armature. Numerical simulation of the experimental process has also been conducted using LS-DYNA. Detailed four spoke steering wheel armature finite element models (employing both magnesium and aluminum alloys) have been developed and simulated under similar conditions which were conducted experimentally. Comparisons between experimental tests at six different impact situations with collisions between the steering wheel armature and a rigid plate are presented in this paper. As well, comparison of the finite element model is considered by investigating changes in the element formulation associated with the armature. The experimental and numerical observations indicate that the predictive capabilities of the aluminum material model are better developed than the magnesium material model. In addition, selection of the finite element formulation significantly affects the numerical results.

  • A Comparison between Three Different Blast Methods in LS-DYNA: LBE, MM-ALE, Coupling of LBE and MM-ALE

    Z. S. Tabatabaei (PhD Candidate, Missouri University of Science and Technology), J. S. Volz (Assistant Professor, Missouri University of Science and Technology)

    A previous experimental test was modeled in LS-DYNA®. Three different methods of simulation were performed. These methods are empirical blast method, arbitrary Lagrangian Eulerian (ALE) method, and coupling of Lagrangian and ALE method. Free field pressure history recorded from experimental test was compared with the first method. Peak pressure for all these three methods were compared together and discussion of results is provided. Keyword: Blast, Lagrangian (LAG), Load Blast Enhanced (LBE), Multi-Material Arbitrary Lagrangian Eulerian (MM- ALE), LS-DYNA

  • A Comparison between Three Air Blast Simulation Techniques in LS-DYNA

    H. Bento Rebelo, C. Cismasiu (Universidade NOVA de Lisboa)

    When simulating structures subjected to the effects of blast loading, one might resort to three different methods of simulation. These methods are the empirical blast method, also known as Load Blast Enhanced (LBE), the Arbitrary Lagrangian Eulerian (ALE) method, and a coupling method that allows the application of empirical blast loads on air domain simulated with the ALE formulation. Furthermore, for the ALE method, both a mapping technique, that allows the mapping of data from 2D ALE simulations to 2D and 3D ALE meshes, and a complete 3D ALE simulation could be performed. In order to verify and compare the efficiency and accuracy of these air blast methods, an air blast loading on a reinforced concrete slab is modelled. Additionally, mesh convergence studies of 2D and 3D ALE simulations are performed.

  • A Comparison between two Methods of Head Impact Reconstruction

    Arghavan Talebanpour, Lloyd Smith, School of mechanical and material engineering Washington State University

    Reconstructing head impacts using computational models is an important tool in understanding brain injury mechanisms. Head impacts are often reconstructed by impacting an Anthropomorphic Test Device (ATD) with an object of interest. The head accelerations are measured and applied to a biofidelic finite element model. Little work has been done, however, to determine how the ATD accelerations applied to a numeric model approximate the brain response an actual impact. The following considered head impacts from a solid sports ball. The brain response of a biofidelic model was compared in two scenarios: accelerations were applied to the model from an impacted by a ball; the head-ball impact was simulated directly in LS-DYNA® with the same speed, direction, and location as occurred with the ATD.

  • A Comparison of Damage and Failure Models for the Failure Prediction of Dual-Phase Steels

    F. Andrade (DYNAmore); M. Feucht (Daimler)

    The aim of this contribution is the comparison of different damage failure models that are available in LS-DYNA. In particular, the focus is concentrated on the failure prediction of dual-phase steels which are largely used in the automotive industry. Typically, such alloys provide a good compromise between ductility and strength for which this kind of material is also often used in safety relevant components. Examples are parts of B-pillars, side rails and cross members, i.e., parts that may be subjected to intensive loadings in a high speed car crash scenario. In contrast to some other usual alloys, dual-phase steels are often reasonably isotropic and well described by J2-based plasticity. This allows the use of simple and very efficient material formulations (e.g., *MAT_024 in LS-DYNA [1]) without excessively losing accuracy in crash simulations. Despite the fact that the elastoplastic behavior of such alloys can be generally well captured by simple plasticity models, the fracture behavior in practical applications still demands the consideration of several effects like stress state dependence, nonlinear paths, material instability, spurious mesh dependence, among others. Therefore, we consider three different damage/failure models available in LS-DYNA in order to calibrate the fracture behavior of a typical dual-phase steel: (a) the GISSMO damage/failure model [1–3]; (b) the Gurson-Tvergaard-Nedlemann model [4, 5] and the Cockcroft-Latham failure model as implemented in *MAT_135 in LS-DYNA [1, 6]. We will shed some light on the differences among these models and verify their ability in reproducing experimental data on the coupon level for different stress states. The goal is to understand the advantages and limitations of each model concerning the prediction of failure. A detailed discussion will then follow the results obtained with the three models.

  • A Comparison of Isotropic (*MAT_224) and Anisotropic (*MAT_264) Material Models in High Velocity Ballistic Impact Simulations

    Sean Haight, Cing-Dao “Steve” Kan (Center for Collision Safety and Analysis (CCSA)), Paul Du Bois (Consulting Engineer)

    To improve the modeling of metals in high velocity impacts, there have been many developments in constitutive material modeling for LS-DYNA ® . One such advancement is the development of the Tabulated Johnson-Cook material model (*MAT_224). *MAT_224 is a tabulated material model with strain rate and temperature dependency. Additionally, this model includes a failure criteria as a function of triaxiality, Lode parameter, temperature, strain rate and element size. This model has been used successfully in the simulation of numerous materials in high velocity ballistic impact load cases. One drawback to the original Tabulated Johnson-Cook material model is that it is implemented with von Mises isotropic plasticity. Therefore, this material model is not ideal for simulating metals that are anisotropic or asymmetric. Subsequently, an anisotropic and asymmetric version of the Tabulated Johnson-Cook model was developed to simulate these materials. The *MAT_264 material model maintains all the capabilities of the *MAT_224 model, but it adds the ability to define the material response in the 0-degree, 45-degree, 90-degree and thickness directions. Additionally, it allows for directional tension-compression asymmetry in the material. Strain rate dependency, temperature dependency, and the failure model are retained from the Tabulated Johnson-Cook model. By using a previously developed failure model and limited material specimen testing, an industrial material characterization was developed for a 6.35 mm thick Ti-6Al-4V rolled plate. Specimen testing of this titanium alloy plate reveals that this material exhibits some anisotropy and asymmetry. NASA cylindrical ballistic tests were simulated with both the *MAT_224 and *MAT_264 material models. First, the isotropic implementation of the *MAT_264 material model is compared to the *MAT_224 model. Second, the anisotropic implementation of the *MAT_264 model is compared to the isotropic *MAT_224 model. Multiple impact velocities are simulated and the resulting exit velocities, internal energies and eroded internal energies are used to compare each material model.

  • A Comparison of Monolithic and Layered-Plate Configurations for Containment

    Thomas J. Vasko, PhD, PE (Central Connecticut State University, New Britain)

    Jet-engine fan, compressor, and turbine blades require containment cases to ensure that any released blade fragments are contained within the engine and do not penetrate the case, where they can damage critical engine components or penetrate the passenger cabin. To determine the centrifugal strength of turbomachinery rotors, disk-burst tests are performed in vertical-axis spin pits that require containment cases to ensure the safety of the surrounding test area. In these applications, the containment cases are sized to determine the minimum thickness the case must have in order to contain all rotating-part fragments. The current study compares a monolithic plate with various layered-plate configurations to assess containment capability as determined by the perforation velocity, the lowest projectile velocity that completely penetrates the target. The targets include a monolithic plate and several layered-plate configurations with and without gaps. The projectile is a rigid sphere that impacts the target normal to the surface. The target plates are made of titanium-6Al-4V that is modeled using the MAT_TABULATED_JOHNSON_COOK (MAT_224) constitutive model in LS-DYNA ® . This is an elastic viscoplastic material model with strain rate and temperature-dependent stress versus strain curves. In addition, plastic failure strain is defined as a function of triaxiality and Lode parameter, strain rate, temperature, and element size. Results of the study can be used to determine the optimum containment-case configuration for a variety of high-speed rotating components.

  • A Comparison of recent Damage and Failure Models for Steel Materials in Crashworthiness Application in LS-DYNA

    Dr. André Haufe (Dynamore GmbH), Frieder Neukamm, Dr. Markus Feucht (Daimler AG), Paul DuBois (Consultant), Dr. Thomas Borvall (ERAB)

    With increasing requirements on crashworthiness, and light-weight car body structures being a central issue in the future of automotive development, the use of high strength steel grades has become wide-spread in modern vehicles. Since these materials all too often show significantly lower ductility than conventional steels, it is of great importance to precisely predict their failure in crash loading conditions. Hence constitutive models in crashworthiness applications need to be able to correctly predict damage and failure mechanisms. These aforementioned, enhanced models are regularly based on a larger number of variables that define the loading history based on stress or strain measures and on accumulated plastic strain and damage variables more or less accurate. Moreover, these models may require initialization with locally computed history properties prior to a crashworthiness simulation in order to predict the subsequent loading response correctly. Furthermore it should be mentioned that orthotropic properties of steel sheets play a major role in the forming process. Hence one may expect that orthotropic behaviour in damage accumulation may also be a major mechanism when failure prediction along the forming-to-crash process chain is evaluated. It is therefore of great importance to not only evaluate the many available models in LS-DYNA based on their performance achieved in crash loading scenarios but also take the production step with mapping of history data into account. The present paper will focus on the different models available in LS-DYNA, e.g. Gurson, Johnson-Cook, GISSMO etc. and discuss the advantages and disadvantages in application, calibration and predictive performance in the light of the producibility-to-servicability simulation chain.

  • A Complementary Experimental and Modeling Approach for the Characterization of Maple and Ash Wood Material Properties for Bat/Ball Impact Modeling in LS-DYNA

    Joshua Fortin-Smith, James Sherwood, Patrick Drane (University of Massachussets), David Kretschmann (U.S. Forest Products Laboratory)

    To assist in developing LS-DYNA finite element models of wood baseball bats that can be used to explore the relationship between bat profile and bat durability, an experimental program was conducted to characterize the mechanical behavior of maple and ash woods for the range of densities used to make major-league quality baseball bats. The test program included four-point bend testing to determine the elastic moduli and breaking strength and Charpy impact testing to determine strain to failure as a function of strain rate. The MAT_WOOD material was used to describe the mechanical behavior of the wood, and the input parameters were calibrated by comparing the results of LS-DYNA finite element simulations of the Charpy tests to the experimental test data. This paper describes the experimental characterization program, summarizes the material parameters and presents a comparison of the finite element simulations of the Charpy testing and bat/ball impacts to experimental results.

  • A Comprehensive Study on the Performance of Implicit LS-DYNA

    Y.-Y. Lin (Hewlett-Packard Company)

    This work addresses four aspects of Implicit LS-DYNA’s performance. First, Implicit LS-DYNA’s scalability is characterized on multicore platforms. Second, the effectiveness of the GPU implementation is examined. Third, the effect of memory configuration on performance and information on how to configure optimal memory size for a system are presented. And fourth, the performance of out-of-core solutions is discussed.

  • A Computational and Experimental Analysis of Ballistic Impact to Sheet Metal Aircraft Structures

    Matti J. Loikkanen - Boeing Commercial Airplanes, Murat Buyuk, Cing-Dao (Steve) Kan - The George Washington University, Nick Meng - SGI

    The ballistic resistance of 2024-T3 and 2024-T351 alloy aluminum flat plates to aircraft engine fragments is evaluated experimentally. Gas and powder gun tests are performed to determine the ballistic speed limit of a spherical steel bullet representing the engine fragment with a diameter of 0.5 inch. The rectangular flat aluminum specimens are prepared as 12 x 12 inch and with three different thickness combinations of 1/16”, 1/8” and 1⁄4”. A normal impact scenario is considered in terms of the orientation of the specimens to the impacting projectile. A computational model is constructed using Johnson-Cook (J-C) material model considering the thermo-viscoplastic behavior of the material with an accumulated damage and an equation of state model. The experimental model was implemented in LS-DYNA to simulate impact tests and validate the ballistic limit findings with a comparison for the failure mechanisms. Under these controlled geometries, controlled impact conditions, and characterized materials with well- defined material properties, experimental damage characteristics are used to determine the essential failure parameters in the material model.

  • A constitutive equation for the aging of elastomer and application to dummy impact programs

    William W. Feng, John O. Hallquist, Christoph Maurath - Livermore Software Technology Corp

    A constitutive equation for chronorheologically simple materials that describes the aging and viscoelastic behaviors of elastomer is presented. A simulated numerical uniaxial relaxation test of a material at various aging stages has been performed. The simulated experimental results demonstrate the chronorheological effect and are used further to determine the material property functions in the constitutive equation. A test of an elastomer at various aging stages has been performed. It demonstrated the same effect as the simulated numerical example. The applications of this constitutive equation to dummy impact programs are mentioned.

  • A Constitutive Formulation for Polymers Subjected to High Strain Rates

    S. Kolling, M. Feucht - DaimlerChrysler AG, A. Haufe - Dynamore GmbH, P.A. Du Bois - Consulting Engineer

    Reliable prediction of the behavior of structures made from polymers is a topic under considerable investigation in engineering practice. Especially, if the structure is subjected to dynamic loading, constitutive models considering the mechanical behavior properly are still not available in commercial finite element codes yet. In our paper, we present a new constitutive law for polymers which recovers important phenomena like necking, crazing, strain rate dependency, unloading behavior and damage. In particular, different yield surfaces in compression and tension and strain rate dependent failure, the latter with damage induced erosion, is taken into account. All relevant parameters are given directly in the input as load curves, i.e. time consuming parameter identification is not necessary. More- over, the models by von Mises and Drucker-Prager are included in the description as special cases. With the present formulation, standard verification test can be simulated successfully: tensile and compression test, shear test and three point bending tests.

  • A constitutive model for thermoplastics with some applications

    Arild Holm Clausen, Mario Polanco-Loria1, Torodd Berstad and Odd Sture Hopperstad - Norwegian University of Science and Technology

    A constitutive model for thermoplastics is outlined in this paper. The model consists of two parts: A hyperelastic-viscoplastic response due to intermolecular resistance denoted Part A, and an entropic hyperelastic response due to re-orientation of molecular chains called Part B. Both parts are developed within a framework for finite strains. The main constituents are the Neo-Hookean model describing large elastic deformations, the pressure-sensitive Raghava yield function, a non-associated visco-plastic flow potential and Anand’s stress- stretch relation representing the intramolecular stiffness. The 11 non-zero coefficients of the model are identified from uniaxial tension and compression tests on two materials, HDPE and PVC, which are respectively semi-crystalline and amorphous thermoplastics. Subsequently, it is employed in numerical simulations of three-point bending tests on the same materials. The model gives satisfactory predictions when compared to experimental behaviour.

  • A constitutive model for thermoplastics intended for structural applications

    Mario Polanco-Loria, Torodd Berstad - SINTEF Materials and Chemistry / Structural Impact Laboratory (SIMLab), Arild Holm Clausen, Odd Sture Hopperstad - Department of Structural Engineering, NTNU/Structural Impact Laboratory (SIMLab)

    This paper presents a hyperelastic-viscoplastic constitutive model for thermoplastics [1]. It is partly based on a model proposed by Boyce et al. [2]. The model involves a hyperelastic- viscoplastic response due to intermolecular resistance, and an entropic hyperelastic response due to re-orientation of molecular chains. A Neo-Hookean material model is selected for describing large elastic deformations. Moreover, the Raghava plastic yield surface [3] is introduced to capture the pressure sensitivity behaviour, and a non-associative visco-plastic flow potential is assumed for volumetric plastic strain control. The strain-rate effects are formulated in a format well-suited for structural applications. Finally, the intramolecular stiffness is represented with Anand’s stress-stretch relation [4]. The model is developed within a framework developed for finite elastic and plastic strains, using a multiplicative decomposition of the deformation gradient. It is implemented as a user-defined model in LS-DYNA [5]. The material model requires 10 parameters which are easy to identify from true stress-strain curves obtained from uniaxial tension and compression tests. In this paper, the parameters are determined from experimental tests on a polyethylene material with high density (PEHD). Subsequently, the model is employed in numerical simulations of the uniaxial tension test and a quasi-static test on a centrally loaded plate. The numerical model gives satisfactory predictions when compared to the observed experimental behaviour.

  • A constitutive model for thermoplastics intended for structural applications

    Mario Polanco-Loria, Torodd Berstad - SINTEF Materials and Chemistry / Structural Impact Laboratory (SIMLab), Arild Holm Clausen, Odd Sture Hopperstad - Department of Structural Engineering, NTNU/Structural Impact Laboratory (SIMLab)

    This paper presents a hyperelastic-viscoplastic constitutive model for thermoplastics [1]. It is partly based on a model proposed by Boyce et al. [2]. The model involves a hyperelastic- viscoplastic response due to intermolecular resistance, and an entropic hyperelastic response due to re-orientation of molecular chains. A Neo-Hookean material model is selected for describing large elastic deformations. Moreover, the Raghava plastic yield surface [3] is introduced to capture the pressure sensitivity behaviour, and a non-associative visco-plastic flow potential is assumed for volumetric plastic strain control. The strain-rate effects are formulated in a format well-suited for structural applications. Finally, the intramolecular stiffness is represented with Anand’s stress-stretch relation [4]. The model is developed within a framework developed for finite elastic and plastic strains, using a multiplicative decomposition of the deformation gradient. It is implemented as a user-defined model in LS-DYNA [5]. The material model requires 10 parameters which are easy to identify from true stress-strain curves obtained from uniaxial tension and compression tests. In this paper, the parameters are determined from experimental tests on a polyethylene material with high density (PEHD). Subsequently, the model is employed in numerical simulations of the uniaxial tension test and a quasi-static test on a centrally loaded plate. The numerical model gives satisfactory predictions when compared to the observed experimental behaviour.

  • A Continuum Model of Deformation and Damage for API X70 Steel Based on the Theory of Strain Gradient

    Mohammed Anazi, Hussein Zbib, Washington State University, School of Mechanical and Materials Engineering

    This work shows the results of a continuum model of deformation and damage for API X70 steel based on the strain gradient theory. The model is developed according to the continuum mechanics of the elastic/viscoplastic framework. The constitutive equations of the model include the dislocation theory according to the roles of the statistically stored and geometrically necessary stored dislocation densities during plastic deformation. In addition, effects of nucleation and growth of voids are considered within the constitutive equations as a ductile failure based on a classical isotropic damage model. Then, the model is examined for scale and strain rate effects. The developed model is implemented into LS-DYNA® by writing a subroutine within USER_DEFINED_MATERIAL_MODELS (UMAT). A ASTM tensile test is simulated to examine the validity of the model. The results show a good agreement with experimental data found in the literature.

  • A Contribution to New ALE 2D Method Validation

    Nicolas VAN DORSSELAER, Vincent LAPOUJADE - Alliance Services Plus,

    Since LS-DYNA® v971 r4, a new ALE 2D method is available. Several finite element studies were performed by AS+ to evaluate the precision of this method in pure Multi-Materials Euler studies . Pure Multi-Materials Euler was tested on Impacts and Explosives studies from Defense and Spatial fields. A High Velocity Impact, a Long Rod Penetration, an Explosively Formed Projectile, a Shaped Charge Jet and an Air Blast were modeled using 2D axisymmetric models. Results were compared to experimental data extracted from reference papers. The very good precision obtained with the 2D ALE method and its ability to represent very dynamic phenomenon will be shown.

  • A contribution to validation of SPH new features

    Thomas Beal, Nicolas Van Dorsselaer, Vincent Lapoujade (DynaS+)

    Since 1998, the Smoothed Particle Hydrodynamics (SPH) method has been developed by LSTC in LS-DYNA®. This method is called a meshfree method because traditional finite elements are replaced by particles which are not physically connected but mathematically linked. It is an alternative to the classical Lagrangian Finite Elements method and is used to simulate problems where materials are submitted to hydrodynamic deformation modes, such as high velocity impacts. In order to improve the capabilities of SPH in LS-DYNA, LSTC recently developed several new functionalities available in the latest versions of LS-DYNA. The first new feature is the possibility to choose a Lagrangian kernel for SPH particles, which means there are always the same neighbors for one SPH node (more stability in tension). The second option is Hybrid SPH / Solid elements, designed to couple the benefits of both SPH and Lagrangian finite elements. With these new Hybrid elements, it is now possible to switch from SPH to solid elements using certain criteria and to realize a better transition between SPH and finite elements areas (no more tied contacts needed). This paper presents the DynaS+ contribution to the test and the validation of these new SPH options. Simple test cases and more complicated cases representative of industrial problems have been performed to assess the behavior and the interest of these new features. All tests have been conducted using LS-DYNA V970 R6.0.0 released in 2012. A comparison with older modeling ways will show the benefits they already bring, and the ones they will bring in the future, when their development will be completed.

  • A Correlation Study between MPP LS-DYNA Performance and Various Interconnection Networks — a Quantitative Approach for Determining the Communication and Computation Costs

    Yih-Yih Lin - Hewlett-Packard Company

    As MPP LS-DYNA uses the message-passing paradigm to obtain parallelism, the elapsed time of an MPP LS-DYNA simulation comprises of two parts: computation cost and communication cost. A quantitative approach for determining the communication cost and, hence, the computation cost and the speedup of an MPP LS-DYNA simulation is presented. Elapsed times, characteristic—latency and bandwidth—of interconnect networks, and message patterns are first measured, and then the method of least square errors is applied to estimate the two costs. This approach allows one to predict the performance, or the speedup, of MPP LS-DYNA simulations with any interconnect network whose characteristics is known. Also, while conducting this performance study of MPP LS-DYNA, loss of accuracy in single-precision (32-bit) MPP LS-DYNA simulations has been found. This finding and the advantage of double-precision (64-bit) arithmetic are presented. INTRODUCTION - Theory for Performance of MPP LS-DYNA To run an N-processor MPP LS-DYNA simulation, or job, an interconnect network, or called simply as interconnect, must first be established to connect the N processors; the collection of the N processors and the interconnect is called an N-processor cluster. In this paper, we will consider only the case that the N processors are of the same kind. For such a job, MPP LS-DYNA starts by decomposing the geometrical configuration of the model into N sub-domains. Each of the N processors is assigned to perform computation on one of the sub-domains; meanwhile, messages are passed among all those processors so that necessary physical conditions, such as 1 2 N force conditions, can be enforced. Let T comput, T comput, …, T comput be each 1 2 N processor’s computation cost, and let T comm, T comm, …, T comm be each processor’s 1 2 communication cost. Define the computation cost Tcomput as max (T comput, T comput, N 1 2 N …, T comput) and the communication cost Tcomm as max(T comm, T comm, …, T comm), respectively. Then the job’s elapsed time can be described as: T elapsed = Tcomput + Tcomm (1) For a given decomposition, the computation cost Tcomput is fixed. In contrast, the communication cost Tcomm varies with the characteristics of interconnects used. The term “speedup” is defined as the ratio T elapsed, 1-processor / T elapsed, N-processor. In general, speedups are smaller than N. Since for the 1-processor job the communication cost Tcomm is zero, the perfect speedup of N folds can be realized only under the unrealistic conditions of zero communication cost, i.e., Tcomm = 0, and perfectly 1 2 N balanced decomposition, which renders T comput = T comput = …= T comput. Assuming that the N processors are of the same kind, the variation of T comput, 2 N T comput, …, T comput arises out of the unbalanced decomposition of the N subdomains. It is extremely difficult to find a universal algorithm to decompose a model with a balanced decomposition. MPP LS-DYNA does provide features, as documented in pfile in parallel specific options, for users to provide hints to get a more balanced decomposition than the default.

  • A Coupled Thermal and Mechanical Model of Sliding Wear

    S. S. Akarca, W. J. Altenhof, A. T. Alpas - University of Windsor, Canada

    Sliding wear of aluminum alloys induce plastic deformation below the contact surfaces even at light loads. Experimental evidence exists for damage accumulation in the form of nucleation of voids and microcracks around the second phase particles in the material layers adjacent to the contact surface. Crack propagation at a certain depth below the surface may lead to the creation of long and thin wear debris particles. The objective of this work was to study deformation and damage accumulation processes in aluminum alloys during sliding wear. LS-DYNA was used to model multiple sliding contacts between an aluminum alloy and a steel counterface. The material model used in the finite element analysis was based on the stress/strain behaviour of a 356 Al (Al-7%Si) alloy determined directly from the analysis of the deformation state of the subsurfaces generated during sliding wear tests. Strain rate and thermal effects were also considered through a coupled thermal and mechanical analysis using material type 106 in LS-DYNA (*MAT_ELASTIC_ VISCOPLASTIC_THERMAL). The accumulation of stresses and strains were studied as a function of contact cycle number. The Lagrangian thermal and mechanical coupled finite element model developed in LS-DYNA was successful to simulate deformation of the aluminum alloy during sliding contacts. Subsurface distributions of the hydrostatic pressure, strain rate and temperature, which are difficult to characterize experimentally or theoretically for work hardening materials, were determined for different loading conditions during sliding contacts. Predicted distributions of stresses and strains were used to model subsurface damage gradient and delamination of subsurface layers. Numerical investigation of a void growth model based on a ductile void growth theory showed the presence of a damage gradient and a critical depth at which delamination cracks might initiate and propagate.

  • A Coupling of Empirical Explosive Blast Loads to ALE Air Domains in LS-DYNA

    Todd P. Slavik - Livermore Software Technology Corporation

    A coupling method recently implemented in LS-DYNA® allows empirical explosive blast loads to be applied to air domains treated with the multi-material arbitrary Lagrangian-Eulerian (ALE) formulation. Previously, when simulating structures subjected to blast loads, two methods of analysis were available: a purely Lagrangian approach or one involving the ALE and Lagrangian formulations coupled with a fluid-structure interaction (FSI) algorithm. In the former, air blast pressure is computed with empirical equations and directly applied to Lagrangian elements of the structure. In the latter approach, the explosive as well as the air are explicitly modeled and the blast wave propagating through the ALE air domain impinges on the Lagrangian structure through FSI. Since the purely Lagrangian approach avoids modeling the air between the explosive and structure, a significant computational cost savings can be realized – especially so when large stand-off distances are considered. The shortcoming of the empirical blast equations is their inability to account for focusing or shadowing of the blast waves due to their interaction with structures which may intervene between the explosive and primary structure of interest. The new method presented here obviates modeling the explosive and air leading up the structure. Instead, only the air immediately surrounding the Lagrangian structures need be modeled with ALE, while effects of the far-field blast are applied to the outer face of that ALE air domain with the empirical blast equations; thus, focusing and shadowing effects can be accommodated yet computational costs are kept to a minimum. Comparison of the efficiency and accuracy of this new method with other approaches shows that the ability of LS-DYNA® to model a variety of new blast scenarios has been greatly extended.

  • A Coupling of Empirical Explosive Blast Loads to ALE Air Domains in LS-DYNA

    Todd P. Slavik - Livermore Software Technology Corporation

    A coupling method recently implemented in LS-DYNA® allows empirical explosive blast loads to be applied to air domains treated with the multi-material arbitrary Lagrangian-Eulerian (ALE) formulation. Previously, when simulating structures subjected to blast loads, two methods of analysis were available: a purely Lagrangian approach or one involving the ALE and Lagrangian formulations coupled with a fluid-structure interaction (FSI) algorithm. In the former, air blast pressure is computed with empirical equations and directly applied to Lagrangian elements of the structure. In the latter approach, the explosive as well as the air are explicitly modeled and the blast wave propagating through the ALE air domain impinges on the Lagrangian structure through FSI. Since the purely Lagrangian approach avoids modeling the air between the explosive and structure, a significant computational cost savings can be realized – especially so when large stand-off distances are considered. The shortcoming of the empirical blast equations is their inability to account for focusing or shadowing of the blast waves due to their interaction with structures which may intervene between the explosive and primary structure of interest. The new method presented here obviates modeling the explosive and air leading up the structure. Instead, only the air immediately surrounding the Lagrangian structures need be modeled with ALE, while effects of the far-field blast are applied to the outer face of that ALE air domain with the empirical blast equations; thus, focusing and shadowing effects can be accommodated yet computational costs are kept to a minimum. Comparison of the efficiency and accuracy of this new method with other approaches shows that the ability of LS-DYNA® to model a variety of new blast scenarios has been greatly extended.

  • A critique of the THUMS lower limb model for pedestrian impact applications

    T. Cloake, C. Bastien (Coventry University), J. Hardwicke (University Hospitals Coventry and Warwickshire), D. Venetsanos (Coventry University), C. Neal-Sturgess (University of Birmingham)

    The Total Human Model for Safety (THUMS) is widely used for biomechanics research and validated at the component and full-body levels. Nonetheless, some authors have reported differences in predictions between the model and real-life injuries, particularly in the lower limbs. This study aims to perform an extensive critique of the THUMS lower limb and identify areas for improvement. The THUMS model was assessed across quasi-static and dynamic validation tests to understand geometry, material properties and response to impact. The study has highlighted that the THUMS’ geometry is comparable to published cadaveric data for bones and ligaments, but soft tissues (muscle, adipose and skin) and fascia have significant simplifications.

  • A Customized Job Manager for Metal Forming Simulations with LS-DYNA®

    Yuzhong Xiao, Xinhai Zhu, Li Zhang, Houfu Fan, Livermore Software Technology Corporation

    In the metal forming analysis, the simulation time of each job is relatively short. However, due to the iterative modifications of the forming tools based on the simulation results, generally there would be several numerical tryouts. Also in addition to those with a single keyword file input, the number of simulation jobs consisting of several (e.g. the progressive die forming) or even dozens of sequential simulations (e.g. the iterative springback compensation process), is increasing. In comparison to conventional simulations, simulation submission and file management of these jobs have become more time-consuming. Therefore, a simple application (Job Manager) has been customized for LS-DYNA metal forming users to manage the simulation jobs more efficiently and reduce the total time cost.

  • A Cyclic Damaged Plasticity Model: Implementation and Applications

    Yuli Huang, Stephen A. Mahin - University of California at Berkeley

    In analysis and design of structures subjected to earthquakes, the cyclic and dynamic nature of the response leads to complications. Material models need to account for cyclic plasticity, including deterioration and eventual failure due to low-cycle fatigue. A cyclic damage plasticity model MAT_DAMAGE_3 (MAT_153, LSTC 2007) is implemented to combine Armstrong-Frederick/Chaboche nonlinear kinematic hardening, isotropic hardening, and Lemaitre isotropic damage evolution based on continuum damage mechanics. By appropriately choosing parameters, this model can reproduce an approximation to the widely-accepted Manson-Coffin low-cycle fatigue rule without of cycle counting. This makes it possible to model the decrease in the material’s ability to deform inelastically. The material model is applied to assess the behavior of a steel structure subjected to deterioration and failure.

  • A data-driven methodology for the automated analysis and explanation of system behavior in crash simulations

    Janis Mathieu, Michael Di Roberto, Michael Vielhaber

    Attributable to model size and complexity of numerical crash simulations, it is not feasible for the engineers to analyze each area or component in detail, especially when these are not the core subject of investigation. In the field of occupant safety, the main explanatory objective is given by the signals of anthropometric test devices (ATD), as they are relevant for the fulfillment of legal regulations and consumer protection guidelines. Hence, this study proposes a data-driven methodology to automatically determine deviations in ATD behavior in a set of simulations and provide possible causes for the prevalence helping the engineer to understand simulations faster and to ensure quality.

  • A Dedicated Forming Package LS-FORM for Stamping Simulation with LS-DYNA®

    Xinhai Zhu, Yuzhong Xiao, Jin Wu, Junyue Zhang, Yiquan Tang, Yi Xiao, Wei Ding (Livermore Software Technology, an ANSYS Company)

    One dedicated package providing the complete solution is always desired by LS-DYNA forming users. Being developed as a process-based package, LS-FORM achieves a seamless integration of pre-processing, LS-DYNA simulation and post-processing. An innovated tooling setup interface in pre-processing makes it easy to define complicated tool motions. The one-button submission provides the shortcut to the LS-DYNA solver to simulate a multi-stage stamping process. The post-processing module can perform a real-time analysis of the forming process by automatically chaining the multi-stage simulation results into a unified database. The user-friendly GUI, up-to-date graphic rendering and impressive stability will also make LS-FORM attractive to users.

  • A Distributed Randle Circuit Model for Battery Abuse Simulations Using LS-DYNA ®

    Pierre L’Eplattenier and Iñaki Çaldichoury (LSTC), James Marcicki,Alexander Bartlett, Xiao Guang Yang, Valentina Mejia Min Zhu, Yijung Chen (Ford Research and Innovation Center)

    Battery abuse research and modeling, Spatially-resolved battery modeling, Electro-thermal battery modeling. A distributed Randle circuit model has been added to the electromagnetics (EM) module in LS-DYNA. This model implements so called “1 st order Randle circuits” connecting two vis-à-vis nodes on the positive and negative current collectors which define a unit cell. These circuits consist of a state-of-charge dependent voltage source, internal resistance, and RC loop for damping effects. They empirically model the electrochemical processes occurring between the current collectors during charge or discharge, such as electrochemical reactions, lithium transport through the electrodes and separator, and electron transport to reaction sites within the electrodes. The EM solver and Randle circuits are coupled to give the potential, current density, and heating distribution in the unit cell and connected conductors. The heat generation is transferred to the thermal solver, which then feeds back to the temperature dependent Randle circuit parameters. Several unit cells can be connected together either by a connecting mesh or by applying EM boundary conditions, hence forming a complete battery cell. Similarly, several cells can be coupled together to form a module. The main purpose of this model is the additional capability to model the electrical and thermal response to battery abuse scenarios, such as crash-induced crush. Depending on the local mechanical deformation occurring during a crush scenario, some of the Randle circuits can be replaced by a short resistance, hence triggering a local increase in the current flow and Joule heating which can lead to thermal runaway. The distributed Randle model is described, as well as how to set up a typical case in LS-DYNA. The process for obtaining inputs to the Randle card is demonstrated. Basic benchmarks with experimental results are presented.

  • A Fabric Material Model with Stress Map Functionality in LS-DYNA

    T. Borrvall (DYNAmore Nordic), C. Ehle, T. Stratton (Autoliv OTC)

    Material 34 (MAT_FABRIC) in LS-DYNA is the material model of choice for fabrics when simulating airbag deployment in the automotive industry. Over the years, the model has been subjected to continuous robustness improvements and incorporation of important application features and today it comes in several forms and with an extensive set of parameters. The state-of-the-art modelling approach is to use the FORM=14 option which allows for specifying uniaxial stress-strain curves in the fabric’s warp and weft directions.

  • A FAILURE CRITERION FOR POLYMERS AND SOFT BIOLOGICAL MATERIALS

    William W. Feng, John O. Hallquist - Livermore Software Technology Corp.

    A failure criterion, for polymers and soft biological materials subjected to very large deformation, is presented in this paper. The criterion is written in terms of the strain invariants in finite elasticity. Experimental tests for determining the failure criterion of a material and some numerical results from LS-DYNA are shown.

  • A FE Modeling and Validation of Vehicle Rubber Mount Preloading and Impact Response

    Sae U. Park, Madhu R. Koka, Kevin R. Thomson, Jeffrey L. Robbins - DaimlerChrysler Corporation

    A variety of rubber mounts are being used for vehicles as isolators/dampers between body and frame, on the engine cradle, etc. It has been the prevalent CAE practice in the auto industry to evaluate the mounts’ high-speed vehicle crash response by the means of nonlinear spring/beam models. However, the simplified models carry a risk of generating incomplete and erroneous results, especially under very complex crash loadings due to the absence of component contact and failure criteria. To alleviate the shortcomings of the simplified mounts, this paper presents a FE representation of a detailed vehicle rubber mount coupled with failure criteria and initial bolt wrenching (preloading) using LS-DYNA, as well as test validation of those mounts.

  • A Finite Element Analysis of Mid-Shaft Femoral Tolerance under Combined Axial-Bending Loading

    Costin Untaroiu, Dan Genovese, Johan Ivarsson, Jeff Crandall - University of Virginia

    Bone fractures occur frequently at mid-shaft femoral site during frontal and offset automotive crashes. Because these injuries are expensive, it is crucial to understand the injury mechanisms if this injury is to be prevented. The experimental investigation of femoral shaft tolerance under loading corresponding to real world accidents requires a challenging test setup that allows applying external loads in controlled conditions, mimics the boundary conditions of the femur, and measures the loads at the mid-shaft cross-section of the femur. In addition, the variability of mechanical and structural properties of the specimens complicates the determination of the injury tolerance of the femur under different loading conditions. A numerical alternative is presented in the current study. First, a subject specific finite element model of a femur is developed based on medical images. Then, the parameters of two material models frequently used to approximate the cortical bone properties are identified using the Successive Response Surface Methodology in the ranges reported in the literature. The objective function is defined based on the impact force data recorded during a three-point bending test and its corresponding numerical simulations. The polynomial meta-models implemented in LS-Opt converge at close values of the material parameters suggesting good performance of the heuristic design search in the current identification problem. The femoral tolerance at mid-shaft location is determined using a virtual test setup that applies combined axial –sagittal bending loading through an axial preload along the knee-hip line and a transversal impact load at the mid-shaft site along anterior-posterior or posterior-anterior directions. The femoral tolerance curves calculated based on external loads show sensitivity with respect to the impact direction of transversal load due to the initial curvature of the femur, but insignificant dependence on the material mode, or the failure criteria used for femoral cortical bone. In addition to suggesting a numerical approach that uses finite element simulations and optimization techniques to determine the injury tolerance of long bones, the results highlight the predominant role of the bending loading in a combined loading of the femur.

  • A Finite Element Investigation Into the Continuous Induction Welding of Dissimilar Material Joints

    M. Duhovic, J. Hausmann (Institut für Verbundwerk­stoffe), P. L´Eplattenier, I. Caldichoury (LSTC)

    Continuous induction welding is an advanced material processing method with a very high potential of providing a flexible, fast and energy efficient means of joining together thermoplastic composites to themselves and metals and alloys. However, selection of the processing parameters and optimization of the process is very difficult as it involves the interaction of up to four differen t types of physics. In addition, many different material combinations including materials with low or high electrical conductivity, thermal conductivity and heat capacity, make the intuitive selection of processing parameters impossible. In this work, a si mulation test - bed, setup for the continuous induction welding of two material partners and their corresponding physics interactions is used to investigate the induction welding possibilities for several combinations of hybrid material joints.

  • A Finite Element Model of THOR Mod Kit Dummy for Aerospace Impact Applications

    Costin D. Untaroiu, Jacob B. Putnam (Virginia Tech), Jeff T. Somers (Wyle Science)

    New spaceflight vehicles are currently being developed to transport crews to space by NASA and several commercial companies. During the launch, and landing phase, vehicle occupants are typically exposed to spinal and frontal loading. To reduce the risk of injuries during these common impact scenarios, NASA has begun research to develop new safety standards for spaceflight. The THOR, an advanced multi-directional crash test dummy, was chosen to evaluate occupant spacecraft safety due to its improved biofidelity. Recently, a series of modifications were completed by NHTSA to improve the bio-fidelity of the THOR dummy. The updated THOR Modification Kit (THOR-k) dummy was tested at Wright-Patterson (WP) Air Base in various impact configurations, including frontal and spinal loading. A computational finite element (FE) model of the THOR was developed in LS-DYNA® software and was recently updated to match the latest dummy modifications.

  • A Finite Element Model of the Pelvis and Lower Limb for Automotive Impact Applications

    C. D. Untaroiu (Virginia Tech), J. Shin, N. Yue (University of Virginia), Y.-H. Kim, J.-E. Kim, A. W. Eberhardt (University of Alabama at Birmingham)

    A finite element (FE) model of the pelvis and lower limb was developed to improve understanding of injury mechanisms of the lower extremities during vehicle collisions and to aid in the design of injury countermeasures. The FE model was developed based on the reconstructed geometry of a male volunteer close to the anthropometry of a 50th percentile male and a commercial anatomical database. The model has more than 625,000 elements included in 285 distinct components (parts). The material and structural properties were selected based on a synthesis of current knowledge of the constitutive models for each tissue. The model was validated in seventeen loading conditions observed in frontal and side impact vehicle collisions. These validations include combined axial compression and bending (mid-shaft femur, distal third leg), compression/flexion/xversion/axial rotation (foot), and lateral loading (pelvis). In addition to very good predictions in terms of biomechanical response and injuries, the model showed stability at different severe loading conditions. Overall results obtained in the validation indicated improved biofidelity relative to previous FE models. The model may be used in future for improving the current injury criteria of lower extremity and anthropometric test devices. Furthermore, the present pelvis and lower limb was coupled together with other body region FE models into the state-of-art human FE model to be used in the field of automotive safety.

  • A Full-Field Calibration Approach on Material Parameter Identification

    S. Cavariani, A. Scattina (Politecnico di Torino), S. Scalera (DYNAmore Italia), D. De Caro, M. M. Tedesco, F. D’Aiuto, S. Bianco, A. Luera, D. Ghisleri (C.R.F.), C. Ilg (DYNAmore)

    Nowadays the possibility to accurately simulate steel alloys is crucial to expect accurate results in crash analysis. Just as much as welding spots, innovative materials like polymers or composites more predictive steel material models are continually sought after throughout the industry. Complex models require a significant effort to calibrate them to the physical behaviour of the materials, but they can perform better. This work will evaluate and compare different techniques to characterize materials for finite element simulations.

  • A Functional Bayesian Method for the Solution of Inverse Problems with Spatio-Temporal Parameters

    Zenon Medina-Cetina - International Centre for Geohazards / Norwegian Geotechnical Institute, Roger Ghanem, Amy L. Rechenmacher - University of Southern California

    A Functional Bayesian (FB) methodology is introduced for the calibration of constitutive parameters spatially distributed within a model. The probabilistic solution to the inverse problem consists of assimilating the uncertainty captured from the actual material responses into the material parameters. A case study is introduced to illustrate the applicability of the method, where a soil model built in LS-DYNA is parameterized using surface displacement fields read from stereo digital images taken during a series of triaxial tests performed under similar conditions. The implementation of the FB method yields probability density functions of the parameters and its corresponding correlation structure. The parameters field is efficiently sampled using the Polynomial Chaos Decomposition method (PC) which allows for spatial non-stationary and nonGaussian material representations. The posterior integration is performed via Markov Chain Monte Carlo techniques. Results show extended inferences about the material behaviour due to probabilistic description of the material variability.

  • A General Damage Initiation and Evolution Model (DIEM) in LS-DYNA

    Thomas Borrvall, Thomas Johansson and Mikael Schill (DYNAmore Nordic AB), Johan Jergéus (Volvo Car Corporation), Kjell Mattiasson (Volvo Car Corporation and Chalmers University of Technology), Paul DuBois

    As the automotive industry is reducing the number of physical prototypes in favour of computer simulations during their design processes, a lot of demands is put on the accuracy of the virtual finite element models used for this purpose. In this context the mathematical modelling of fracture is of major importance and has been a field of intense research over the past 50 some years. There are numerous fracture models implemented in LS-DYNA, but as of tradition a fracture model is statically linked to the underlying constitutive model which in practice limits its usage to a single stage of the design process. Recently GISSMO [1,2,3] was introduced in an attempt to remedy this shortcoming by allowing the fracture model to be separated from the constitutive model, thus facilitating results from manufacturing simulations to be transferred to subsequent crash simulations. Behind GISSMO, the Damage Initiation and Evolution Model (DIEM) was developed in the same spirit and with similar capabilities, but this model has to the authors’ knowledge not been used extensively. The intention with this paper is to present this latter fracture model and compare it with GISSMO and, to some extent, with CrachFEM [4] to which it has superficial similarities.

  • A Graphical User Interface for Simulating Resin-Transfer-Molding Combining LS-DYNA and OpenFOAM

    M. Wagner, M. Martins-Wagner (OTH Regensburg), A. Haufe, C. Liebold (DYNAmore)

    The paper describes parts of the joint research project Swim-RTM including several industrial and academic partners. Its goal is to combine LS-DYNA and the open-source fluid-dynamics solver OpenFOAM® to simulate the production process for fiber reinforced plastics, particularly the resin-transfer-molding (RTM) process. In this process, the layers of dry fabric (uni-directional or woven) are formed in the mold (draping) and then filled with liquid resin with high pressure at injection points.

  • A gray-scale mapping method to consider locally varying properties for wood forming simulations

    C. Liebold (DYNAmore), D. Zerbst (German Aerospace Center), T. Gereke (TU Dresden), S. Clauß (Mercedes Benz)

    Automotive interior components in upper-class vehicles are often made of wood veneer sheets that are subject to a forming process [1]. Due to the anisotropy and inhomogeneity of the material caused by the development of annual rings during the growth of the tree, establishing a stable production process based on trial-and-error forming tests is time-consuming and costly [2]. Hence, numerical methods for simulating the forming process are in high demand to support the development of feasible trim part geometries. The key for reliable process simulations of wood-based materials is the consideration of the variability of material properties.

  • A Grid-based Adaptive Scheme for the Three-Dimensional Forging and Extrusion Problems with the EFG Method

    H. S. Lu, C. T. Wu - Livermore Software Technology Corporation

    Procedures to adaptively refine meshes are emerging as an important tool for improving accuracy and efficiency in large deformation and fracture analysis. Comparing to the mesh- based adaptive method, the grid-based adaptive mesh-free method has several built-in advantages including naturally conforming in shape functions, smoothed interpolations in surface construction and state variable transfer, and the results are less sensitive to the unstructured grids. In this paper, a grid-based adaptive scheme is proposed for the Element Free Galerkin method in the large deformation analysis of three-dimensional forging and extrusion simulations. To precisely account for the effect of kernel functions during adaptive procedure, we consider the meshfree adaptivity in the framework of arbitrary Lagragian-Eulerian meshfree method with an operator-split time integration. A grid-based interpolation scheme adopted from the meshfree approximation is developed for the state variable transfer after mesh refinement to improve conservation and monotonic properties. Several industrial problems have been solved and compared to the existing numerical methods.

  • A Heterogeneous Constitutive Model for Reinforced Carbon-Carbon using LS-DYNA

    Kelly S. Carney, Robert K. Goldberg, J. Michael Pereira - NASA Glenn Research Center, USA, Ryan S. Lee, Jeremie J. Albert - The Boeing Company

    Reinforced Carbon-Carbon (RCC) is a ceramic matrix, coated C/C composite used in the Space Shuttle’s thermal protection system. A constitutive model for RCC is presented that separates the coating and substrate within a multi-material shell element allowing for bending strains to be accurately computed during a finite element analysis. Version 971 of LS-DYNA contains a new shell element formulation that allows for different constitutive models through the thickness. The carbon substrate is modeled with an orthotropic damage model that was originally developed by Matzenmiller, and has been enhanced into MAT_RATE_SENSITIVE_COMPOSITE _FABRIC (MAT 158). The behavior of the silicon carbide coating is modeled using a new constitutive model that is now included in LS-DYNA as MAT_NONLINEAR_ELASTIC_TENSION_CRACKS (MAT 236). The composite model is used for debris impact analysis on the RCC structures, and good correlation is shown with impact test deflections and damage.

  • A heuristic attempt to reduce transverse shear locking in fully integrated hexahedra with poor aspect ratio

    Dr. Thomas Borrvall - Engineering Research Nordic AB

    In an attempt to alleviate transverse shear locking in fully integrated hexahedra elements with poor aspect ratio, two new variants of solid element type 2 in LS-DYNA have been developed, implemented and tested on some critical problems. The approach is based on modifying the jacobian matrix in such a way that the spurious stiffness is reduced without affecting the true physical behavior of the element. The method is in a sense justified by means of a theoretical motivation, but above all indicated to be of practical use through some illustrating examples. The two new solid elements are termed type-1 and -2, where the latter is more rigorous but suffers from a higher computational expense, whereas solid element type-1 has an efficiency slightly worse than solid element type-2 for explicit analyses. However, all three element types are in that sense comparable for large scale implicit analyses.

  • A heuristic attempt to reduce transverse shear locking in fully integrated hexahedra with poor aspect ratio

    Dr. Thomas Borrvall - Engineering Research Nordic AB

    In an attempt to alleviate transverse shear locking in fully integrated hexahedra elements with poor aspect ratio, two new variants of solid element type 2 in LS-DYNA have been developed, implemented and tested on some critical problems. The approach is based on modifying the jacobian matrix in such a way that the spurious stiffness is reduced without affecting the true physical behavior of the element. The method is in a sense justified by means of a theoretical motivation, but above all indicated to be of practical use through some illustrating examples. The two new solid elements are termed type-1 and -2, where the latter is more rigorous but suffers from a higher computational expense, whereas solid element type-1 has an efficiency slightly worse than solid element type-2 for explicit analyses. However, all three element types are in that sense comparable for large scale implicit analyses.

  • A High Strain Rate Model with Failure for Ice in LS-DYNA

    Kelly S. Carney - NASA Glenn Research Center, David J. Benson - University of California, Paul Du Bois, Ryan Lee - The Boeing Company

    Modeling the high velocity impact of ice was a requirement in the safety calculations for the return-to-flight of the Space Shuttle on July 26, 2005. Ice, however, is not a common structural material and commercial finite element programs didn't have any appropriate models. A phenomenological model with failure was developed to match experimental ballistic tests. The model has a relatively small number of material constants, most of which have been measured experimentally. A description of the model and comparisons of calculations to experiments are presented.

  • A Hosford-Based Orthotropic Plasticity Model in LS-DYNA

    F. Andrade (DYNAmore), T. Borrvall (DYNAmore Nordic), P. Du Bois (Consultant), M. Feucht (Daimler)

    n this contribution, we present a new orthotropic plasticity model available in LS-DYNA. Over the last decades, several orthotropic material models have been proposed in the literature where many of them have been implemented in LS-DYNA. Among these models, the model proposed by Barlat and Lian in 1989 [1], available in LS-DYNA in *MAT_036 [2], is a popular choice, especially in forming simulations. This model allows the user to define up to three R values (Lankford parameters) related to three material directions, namely 0°, 45° and 90° with respect to the rolling direction. Some years ago, the original orthotropic formulation by Barlat and Lian, available under *MAT_036 in LS-DYNA, was extended in such manner that the yield stress can depend on the different material directions. From a user point of view, this meant that up to five flow curves could be defined. Furthermore, up to five R values could also be used where these could be either constant or a function of the plastic strain. In *MAT_036, the extended model is activated by setting the flag HR to 7. However, the extended formulation incorporates the orthotropy in the yield stress as well. The consequence is that these two effects (orthotropy in the effective stress and also in the yield stress) concur against each other. For many materials, especially mild sheet steels, this aspect has often no major influence on the results. However, certain materials do exhibit quite dissimilar R values in the different material directions meanwhile the yield strength is very similar. This is, for instance, the case of many aluminum alloys. In such cases, the extended formulation available through HR=7 in *MAT_036 (or HOSF=0 in *MAT_036E) might lead to concave yield surfaces which, in turn, might lead to numerical instabilities. Therefore, a new option, issued through the flag HOSF, has been implemented in LS-DYNA in *MAT_036E. If HOSF is set to 1, a “Hosford-based” effective stress is used in yield function. This modification tends to alleviate the numerical instabilities observed in the model where the “Barlat-based” effective stress was used whenever the R values were very dissimilar. In a certain sense, the modification can be seen as a new plasticity model because in the new formulation the yield condition is not formulated using any information related to the R values but merely from the flow curves in the different directions. The R values are instead only used in the plastic flow rule. In this paper, we will show the advantages of such formulation as well as the results of the calibration of the material parameters for an aluminum sheet material. The results show that the simulation with the new material model can reproduce the strain fields captured in experiments through DIC very accurately.

  • A Layer by Layer Approach for Simulating Residual Stresses in AM

    N. Strömberg (Örebro University); M. Schill (DYNAmore)

    Distortions and residual stresses developed during additive manufacturing (AM) might be so severe that the design does not meet tolerance requirements or even cracks and fail. Predictions of such distortions and residual stresses by finite element analysis are therefore preferable performed early during the design development in order to reduce such problems. One approach for this kind of analysis is to apply techniques from welding simulations letting the Goldak heat source moving over each layer of the material. However, this is computationally most costly and one might also argue how well this actually represent the AM process. We suggest to simplify this boundary condition to instead apply the heat layer by layer. We mean that this will represent the AM process as well as an approach of using the Goldak heat source and it is much more computational efficient than applying Goldak’s heat source. The model is simply obtained by slicing the geometry in several layers using an in-house script. Then, a volume heat source is applied layer by layer, where each layer is activated starting from the build plate until the final build layer. Sequentially thermomechanical analysis using LS-Dyna is applied, where the heat capacity, conductivity, Young’s modulus, Poisson’s ratio, expansion coefficient, yield stress, and the hardening modulus are given as functions of temperature. The classical heat equation and J2-plasticity with kinematic or isotropic hardening are adopted by using *MAT_THERMAL_CWM and *MAT_CWM, which makes the activation of the layers straight-forward using the ghost feature implemented in these material models. After all layers are activated and heated, a restart of cooling analysis is performed and, finally, the part is cut from the building plate using a third restart analysis. The approach is demonstrated for a benchmark of an open cylinder in Inconel 718 showing the development of distortions and residual stresses in all stages of the AM process from heating during building until the final cut from the build plate. We suggest that this benchmark can serve as an experimental setup in order to validate the suggested approach. This is discussed in the paper and is a topic for future work.

  • A MATERIAL MODEL FOR TRANSVERSELY ANISOTROPIC CRUSHABLE FOAMS IN LS-DYNA

    Andreas Hirth - DaimlerChrysler, Paul Du Bois, Dr. Klaus Weimar - DYNAmore

    Recently new materials were introduced to enhance different aspects of automotive safety while minimizing the weight added to the vehicle. Such foams are no longer isotropic but typically show a preferred strong direction due to their manufacturing process. Different stress/ strain curves are obtained from material testing in different directions. A new material model was added to the LS-DYNA code in order to allow a correct numerical simulation of such materials. Ease-of-use was a primary concern in the development of this user-subroutine: we required stress/ strain curves from material testing to be directly usable as input parameters for the numerical model without conversion. The user-subroutine is implemented as MAT_TRANSVERSELY_ANISOTROPIC_CRUSHABLE_FOAM, Mat law 142 in LS-DYNA Version 960-1106. In this paper we summarize the background of the material law and illustrate some applications in the field of interior head-impact. The obvious advantage of incorporating such detail in the simulation lies in the numerical assessment of impacts that are slightly offset with respect to the foam’s primary strength direction.

  • A Mesh Refinement Study on the Impact Response of a Shuttle Leading-Edge Panel Finite Element Simulation

    Karen E. Jackson, Edwin L. Fasanella - US Army Research Laboratory, VTD, Karen H. Lyle - NASA Langley Research Center, Regina L. Spellman - NASA Kennedy Space Center

    A study was performed to examine the influence of varying mesh density on an LS-DYNA simulation of a rectangular-shaped foam projectile impacting the space shuttle leading edge Panel 6. The shuttle leading-edge panels are fabricated of reinforced carbon-carbon (RCC) material. Nine cases were executed with all possible combinations of coarse, baseline, and fine meshes of the foam and panel. For each simulation, the same material properties and impact conditions were specified and only the mesh density was varied. In the baseline model, the shell elements representing the RCC panel are approximately 0.2-in. on edge, whereas the foam elements are about 0.5-in. on edge. The element nominal edge-length for the baseline panel was halved to create a fine panel (0.1-in. edge length) mesh and doubled to create a coarse panel (0.4-in. edge length) mesh. The element nominal edge- length of the baseline foam projectile was halved (0.25-in. edge length) to create a fine foam mesh and doubled (1.0- in. edge length) to create a coarse foam mesh. The initial impact velocity of the foam was 775 ft/s. The simulations were executed in LS-DYNA for 6 ms. Predicted structural deformations and time-history responses are compared for each simulation.

  • A Mesh-free Analysis of Shell Structures

    C. T. Wu, Yong Guo - Livermore Software Technology Corporation, Hui-Ping Wang, Mark E. Botkin - General Motors

    A mesh-free formulation based on the Mindlin-Reissner shell theory for geometrical and material nonlinear analysis of shells is presented. In this mesh-free formulation, two projection methods are developed to generate the shell surface using the Lagrangian mesh-free interpolations. The updated Lagrangian theory underlying the co-rotational procedure is adopted for the local strain, stress and internal force updating. A local boundary integration method in conjunction with the selective reduced integration method is introduced to enforce the linear exactness and relieve shear locking. Both nonlinear static and dynamic analysis of shell structures with finite rotations are considered. Several numerical examples are presented to demonstrate the accuracy and applicability of the proposed formulation.

  • A Meso-Macro Scale Method for Jointed Structures and Their Failure Analysis

    Wei Hu, CT Wu, Xiaofei Pan, Youcai Wu (Livermore Software Technology, LLC)

    As automotive industry moves rapidly towards electrified and digitalized world, the use of lightweight materials and new joining technologies becomes crucial to counteract the weight of electronic and autonomous equipment for energy efficiency as well as to maintain safety and performance. Numerical modeling the joined structures including their failure behavior has been a big challenge in the modern lightweight vehicle safety design. In this study, a two-scale method developed in LS-DYNA® is introduced for modeling jointed structures and their connection failure. In the meso-scale, a new particle stabilization method via a velocity smoothing algorithm is developed for simulating the large deformation and material failure of joint models. The meso-scale joint model characterizing the baseline of joint structure is bridging with macro-scale shell structures using an immerse approach. As a result, a topological coupling between solid and shell formulations is achieved without the need of matching discretization. This two-scale method facilitates the modeling of most connection failures in different joint models and minimizes human interactions with software. A crushing tube example is utilized to demonstrate the effectiveness and applicability of the present method in modeling the joined structures and failure behavior for the modern lightweight vehicle safety design.

  • A Meta-model based Approach to Implement Variation Simulation for Sheet Metal Parts using Mesh Morphing Method

    H. Zheng, K. Upadhyay, F. Litwa (Mercedes-Benz), K. Paetzold (University of the German Federal Armed Forces Munich)

    The virtual process chain is an essential step for the sustainable digital transformation in the manufacturing industry. For the Body-In-White (BIW) sheet metal parts, the manufacturing joining simulation based on finite element method is used to simulate the joining processes in the body shop. The target is to predict the dimensional accuracy of assemblies after using different types of joining technologies. However, the assembly deviation is not only affected by the joining operations, but also by the initial part deviations. Therefore, an integration of geometrical variations in the joining simulation model is necessary to improve the prediction accuracy.

  • A method for modifying the forming tool geometry in order to compensate for springback effects

    Anders Jernberg - Engineering Research Nordic AB, Sweden

    There is always a certain amount of springback deformation in a metal forming process. The high strength steel is becoming a more attractive choice for many applications when low weight of the structure is of importance. One major drawback with the high strength steel is that the springback deformation increased compared to low strength steel. All currently known techniques to reduce the springback deformation are used in tool design today, so it can be really hard to reduce the springback deformation further. The only possibility to obtain the desired geometry for the sheet after springback is to have a shape of the tool that is different than the desired final shape of the sheet. A method to modify the tool geometry in order to compensate for the springback effect is here presented. It is a heuristic method, based on the difference between the sheet after springback and the desired shape. No parameterisation of the tool geometry is needed. Since no parameters are describing the shape of the tool geometry, it can be modified in an arbitrary way without the restriction of the design space spanned by design parameter. The method is demonstrated on a doubly curved sheet and it is shown that the method gives a very fast convergence for the desired shape of the sheet. It is most likely that the method will work on a variety of different shapes. The method is applicable regardless of the yield strength of the sheet material, but most interesting are probably those materials which gives a large springback deformation, such as high strength steel and aluminium.

  • A Methodology to Model the Statistical Fracture Behavior of Acrylic Glasses for Stochastic Simulation

    Marcel Berlinger, Stefan Kolling, Andreas Rühl (Technische Hochschule Mittelhessen), Jens Schneider (Technical University of Darmstadt)

    Acrylic glass made of PMMA bears great potential for automotive glazing. As a substitute for mineral glass, new freeform designs become possible with a simultaneous reduction of the structural weight. Under safety aspects of highly weight optimized components, a very precise knowledge of the material behavior is necessary since it is well known that PMMA is a material with high variability in its strength. In the present work, a methodology is proposed to determine the statistical probability distribution of fracture strains from experimental testing. Subsequently, a rate-dependent stochastic failure model is developed. By generation of uniformly distributed random numbers which represent the occurrence probability, *MAT_ADD_EROSION cards for LS-DYNA® are used, containing the tabulated fracture strains at different strain-rates. For stochastic simulation there are two possible procedures to apply the present model. The user provides a distinct probability quantile, e.g. 5 % occurrence probability, generates the corresponding *MAT_ADD_EROSION card and performs a worst-case simulation. Alternatively, the user generates a random set of probability quantiles, i.e. N values from zero to one, and performs N simulations. As an application, the last procedure is used in order to show the influence of a varying fracture strain on the head injury criterion (HIC) in validation tests on PMMA side windows. The example demonstrates the necessity of stochastic simulation for a reliable quantification of injury criteria in crashworthiness analysis.

  • A Model for Process-Based Crash Simulation

    O.G. Lademo, T. Berstad, - SINTEF Materials and Chemistry, Norway., T. Tryland - Hydro Aluminium Structures, Norway., T. Furu - Hydro Aluminium R&D, Norway, O.S Hopperstad, M. Langseth - Norwegian University of Science and Technology

    Manufacturing of a bumper system from aluminium extrusions often involves series of forming operations performed in the soft W temper condition, and then artificially age-hardening the components to the material's peak hardness T6 condition. It is perceptible that correct numerical representation of the crash performance of the resulting systems must rely upon a geometry obtained from a model following the process route, i.e. including simulation of all major forming operations. However, the forming operations also result in an inhomogeneous evolution of some internal variables (among others the effective plastic strain) within the shaped components. Here, results from tensile tests reveal that plastic straining in W-temper results in a significant change of the hardening curves (alloy and ageing-dependent increase or decrease in strength) as a function of plastic pre- straining. In addition, the tests revealed that the plastic deformation led to a reduction of the elongation of the T6 specimens. These data were obtained by uniaxial stretching of plates in the W temper to different levels of plastic deformation, sub-sequent artificial ageing to obtain T6 characteristics, machining of uniaxial tensile test coupons and, finally, testing until failure. In the present work, these process effects have been included in a user-defined elasto-viscoplastic constitutive model incorporating a state-of-the-art anisotropic yield criterion, associated flow rule, non-linear isotropic and kinematic hardening rules, a strain-rate hardening rule as well as some ductile fracture criteria. To demonstrate and asses the modelling methodology, a 'through-process analysis' of the uniaxial tensile tests is performed. The pre-stretching of the plates in W temper is modelled with shell elements having an initial random Gauss- distributed thickness and stretched to different levels of plastic strain – comparable to the experimental ones - using the explicit solver of LS-DYNA. Then, uniaxial tensile specimens are trimmed from the deformed plates using the trimming option available in LS-DYNA. Next, strain dependent T6 properties are specified, after which the resulting specimens are stretched until instability and failure. Finally, the model assumptions are assessed by comparing engineering stress-strain curves obtained from the simulations and experiments.

  • A Model for the Stochastic Fracture Behaviour of Glass

    Christopher Brokmann, Stefan Kolling (Technische Hochschule Mittelhessen)

    The failure of glass is caused by initial flaws that are induced during the manufacturing process. These micro-cracks are randomly distributed on the surface of glass, which is why failure is a random process and stress at failure is a non-deterministic parameter. In the present work, a model for the stochastic fracture behaviour of glass is proposed and implemented as a user subroutine in LS DYNA® for shell elements. Due to the stochastic fracture behaviour of glass, a large scattering can be expected when determining the head injury criteria (HIC) in the case of a pedestrian head impact on an automotive windscreen. In this case a high experimental effort would be necessary to evaluate the stochastic scattering. This can be reduced by numerical simulation using a stochastic failure model. The present model generates failure strengths out of a Weibull distribution obtained by coaxial ring-on-ring tests. The generated stresses are used to calculate initial crack lengths by recalculate the subcritical crack growth during experiments. These initial cracks slowly grow, i.e. subcritical, in dependence on the applied stress rate until the critical stress intensity is reached and failure occurs. In order to validate the model, coaxial ring-on-ring tests with different test setups are simulated and compared to experimental values and analytical solutions using the Weibull surface shift.

  • A modified approach for simulating complex compound structures within early design steps

    Georg Gruber, Daniel Klein,Sandro Wartzack - University of Erlangen-Nuremberg

    Owing to increasing relevance of lightweight design the deployment of compound structures with their beneficial material characteristics becomes more and more important. These growing demands for lightweight design cannot be met by improving constructive details at the end of the development cycle. On the contrary already the early design steps have to be exploited adequately, since these steps offer the highest freedom of design. The present paper shows a modified approach for simulating complex compound structures adapted to the requirements of early design steps. The basic idea is overlapping several basic material models (characterized by a low amount of input parameters) within one finite shell formulation to describe any combination of material effects. The benefit of the approach is a more accurate simulation of complex compound structures with reduced modeling effort. A validation of this phenomenological material superposition approach is performed by opposing the results of virtual material tests to experimental results published in the literature.

  • A MOOSE CRASH DUMMY FOR LS-DYNA

    Larsgunnar Nilsson, Anders Jernberg - Engineering Research Nordic AB

    The vehicle to moose impact constitutes a serious traffic problem in the Nordic Countries. Thus, in addition to the conventional requirements on crashworthiness, a Swedish car is also supposed to protect the occupants in the case of a moose impact. The Swedish National Road and Transport Research Institute (VTI) has developed a moose crash test dummy, which has shown to have a similar impact behaviour on the vehicle as a real moose. The main components of the test dummy are 36 rubber plates, but there are also various steel parts holding the pieces together. Due to the height of the moose, the main body will hit a normal size passenger car in the A-pillar and front window region. The legs will hit more frontal parts of the vehicle and make the moose body rotate. In a typical moose impact the A-pillars and the frontal roof are severely deformed into the passenger compartment. A FE-element model of the moose crash test dummy has been developed for LS-DYNA. The FE-model closely replicates all components of the physical dummy. About 30.000 elements are used for the model, which has a critical time step of about 1.5 microsecond. The FE-model of the moose is complete and only the contact interfaces between the moose and the vehicle need to be defined. Simulations of passenger car to moose impacts have been conducted and the results are evaluated and compared to physical test data.

  • A new advanced visco-elastoplastic eight chain rubber model for LS-DYNA

    Dr. Tobias Olsson and Prof. Larsgunnar Nilsson - Engineering Research Nordic AB

    A new advanced eight chain rubber model has recently been implemented in LS-DYNA. The material is tailored for polymeric materials. The basic theory is taken from Arruda’s thesis from 1993 but it has been enhanced with advanced features such as the Mullins effect, viscoelasticity, plasticity and viscoplasticity. The Mullins effect is described by two different models: the first one is strain based and developed by Boyce in 2004 and the second is energy based and developed by Ogden and Roxburgh in 1999. The viscoelasticity is based on the general Maxwell theory with up to six Maxwell elements (a spring and a dashpot in series). There are three different viscoplasticity models implemented: a Norton model with two parameters, a G’Sell model with six parameters and a strain hardening model with four parameters. The plastic yield strength is based on the eight parameter Hill model. The material model has been used to simulate a compression test with a rubber specimen. The material parameters were obtained from inverse FE analys and parameter fitting using LS-OPT and a force-displacement data set. The result shows that this material model can predict rubber behaviour inline with experimental results.

  • A New Approach to Contacts and Rigid Body Inter- actions in LS-DYNA

    Frederik Bengzon, Thomas Borrvall, Anders Jonsson, Gert Petersen

    Traditionally in LS-DYNA (almost) all contact definitions use a penalty formulation. This means that penetration in the contact is required to obtain a contact force between interacting entities. It is then up to the user to verify that the penetrations are small enough not to influence the results. The Mortar contacts [1], which have become the preferred choice for implicit analyses, is of penalty type. Also, the rigid walls (*RIGIDWALL) use a penalty method in implicit analyses. To find a good penalty stiffness setting may be problematic if solid elements (especially tetrahedra), or soft materials, such as rubber or plastic, are involved. It can be hard to find a good trade-off between reasonably small penetrations and implicit convergence.

  • A New Concept on Stamping Die Surface Compensation

    Li Zhang, Jin Wu, Dajun Zhou - DaimlerChrysler Corporation, XinHai Zhu - Livermore Software Technology Corporation

    This paper classifies existing die compensation methods into two general categories, geometry-based method and springforward method. To meet the challenge of increased application of AHSS and its associated severe springback problems, we propose a new concept by using the tooling mesh of design intent as reference during compensation iterations. Incorporation of this concept into these two original methods enhances the efficiency and accuracy of compensated die surface. The enhanced geometric method minimizes the “wrinkle” effect caused by traditional methods done on the blank mesh. The enhanced springforward method improves the convergent rate to a specified tolerance. The proposed scheme can start compensations on a die with either design intent surfaces or already modified surfaces. It is also capable to incorporate actual panel scan data into compensation process to achieve high compensation accuracy.

  • A new constitutive model for nitrogen austenitic stainless steel

    S. Fréchard, A. Lichtenberger, F. Rondot, N. Faderl - Institut Franco-Allemand de Recherches, France, Redjaïmia - Laboratoire de Science et Génie des surfaces, France, M. Adoum - CRIL, France

    Quasi-static, quasi-dynamic and dynamic compression tests have been performed on a nitrogen alloyed austenitic stainless steel. This alloy achieves a high hardening modulus and a good ductility at all strain rates. In addition, this steel is very sensitive to strain rate. The temperature sensitivity has been determined for temperatures varying between 20°C and 400°C. Microstructural analysis has been performed on samples subjected to different loads in order to relate the microstructure to the material behaviour. Johnson-Cook and Zerilli-Armstrong models have been selected to fit the experimental data into constitutive equations. These models are unable to reproduce the behaviour of this type of steel over the complete range of tests. A new constitutive model that better fits all the experimental data at different strain, strain rate and temperature has been determined. This empirical model supposes that the influence of the main parameters is independent. Single Taylor impact tests have been realized to validate the models. Live observations of the specimen during impact have been achieved using a special CCD camera set-up. The overall profiles at different times were compared to numerical predictions performed with LS-DYNA.

  • A New Development in Pedestrian Safety: The FLEX-PLI GTR LS-DYNA Model

    Chirag S. Shah, Fuchun Zhu, Roel Van De Velde, Robert Kant - First Technology Safety Systems

    The lower limb is one of the most frequently injured body regions in crashes involving pedestrians. A biofidelic FLEXible-Pedestrian Legform Impactor Global Technical Regulations (FLEX-PLI GTR) device has been developed under directions of the Flex-PLI Technical Evaluation Group (FLEX-PLI TEG). First Technology Safety Systems (FTSS) is developing a LS-DYNA model in addition to the hardware counterpart. The FLEX-PLI GTR is the latest development and successor of the earlier GT version. The FLEX-PLI GTR device has three regions: femur, knee and tibia. Outer rubber and neoprene foam layers represent the skin and flesh. The femur and tibia regions are segmental to achieve flexible bending behavior representing human like responses during pedestrian crashes. The central bone cores of the tibia and femur have bending moment measuring capabilities at several locations. The knee region has ligament elongations measuring capabilities to be used as injury criteria in regulations. This paper documents the development and dynamic validations of the FTSS FLEX-PLI GTR LS-DYNA model. The model geometry and inertia properties are obtained from available drawings and hardware. The model connectivity and structural integrity are inspected by experiments and verified against hardware. The model material properties are implemented from material test data. The model is then validated against dynamic calibration test for FLEX-PLI assembly without outer skin, and a full legform test against a flat rigid impactor (called inverse test). The femur and tibia bone bending moments and knee ligament elongations from the model output are compared to test data to evaluate model performance and injury predictability. The FTSS FLEX-PLI GTR LS-DYNA model revealed very promising performance in all validation cases and can be potentially used in future pedestrian safety regulations. The model has a 0.85 micro second time step and was found to be very cost effective (in terms of CPU times) and reliable for pedestrian safety simulations.

  • A New Eigensolver for High Performance NVH Analysis: MCMS (Multi-Level Component Mode Synthesis)

    Prof. K. Chang-Wan (Konkuk University); R. Grimes (LSTC)

    NVH (Noise, Vibration, and Harshness) problem is one of the most important targets for comfortable and quiet product design. Especially, in automobile industry, as the degrees of freedom of NVH automobile FE model increases, from millions of degrees of freedom to tens or hundreds millions of degrees freedom, the computational time for NVH analysis becomes serious bottle neck in automobile design and analysis process. Therefore, it has been strongly desired to reduce the computational time of eigenvalue problem analysis, which is the most important part of NVH analysis. In early 2000, the Automated Multi-Level Substructuring (AMLS) method was developed to reduce the computational costs of NVH analysis by the group of University of Texas at Austin, in which author of this paper is also involved in the development of AMLS method as well as Fast Frequency Response Analysis(FFRA) method. As the AMLS method provide significant contributions on automobile NVH analysis, many CAE softwares such as NASTRAN, ABAQUS, Hyperworks released new feature which is similar to AMLS. LSTC has developed a new eigensolver, MCMS(Multi-level Component Mode Synthesis). MCMS generally produces approximate eigensolutions that are less accurate than those computed by Lanczos method, but the error can be tolerated in automobile NVH applications

  • A New Failure Criterion for Laminated Safety Glass

    C. Alter, S. Kolling (TH Mittelhessen); J. Schneider (TU Darmstadt)

    The prediction of the head injurie criterion (HIC) for pedestrian protection in automotive applications is still a great challenge. In particular, the simulation of the head impact on windshields requires a reliable FE-modelling technique as well as predictive material laws including the constitutive behaviour up to fracture. In the present work, a new failure criterion for laminated safety glass under low velocity impact is presented. The model is implemented as a user defined material model for shell elements in LS-DYNA. In order to represent the stress intensity in the vicinity zone of a crack tip, a mixture of the element erosion technique and a decrease of strength in the direction of cracks is considered. By that there is no need to determine the current stress intensity factor. The used failure prediction is similar to a major stress criterion and the fracture strength depends on the stress rate and, in addition, on the fracture state of the neighboring elements. The basic strength is derived from the first region of the crack-velocity dependency which is approximated by an empirical power law. The reduction of element strength in crack direction depends on the element size which allows the use of a regular, coarse mesh. Experimental results of head impact tests under different configurations are used for the validation of the present model.

  • A New Feature to Model Shell-Like Structures with Stacked Elements

    T. Erhart (DYNAmore)

    A computational method for the numerical simulation of stacked shell-like structures will be presented. These types of plane load-bearing components possess a thickness which is small compared to its other (in-plane) dimensions and physical properties vary in thickness direction in distinct layers. Such materials are made from two or more constituent materials with different physical or chemical properties, that when combined, produce a material with characteristics different from the individual components. The individual components remain separate and distinct within the finished structure.

  • A New Heat Transfer Capability Between CPM Gas and Its Surroundings

    Sheng Peng (LSTC)

    Corpuscular particle method (CPM) was developed for airbag deployment simulations. It took into account specifics like airbag folding technique, vent hole design, and interaction between discretized gas flow and airbag fabric to capture the effects of dummy impact on airbags, both fully inflated and out-of-position. It’s numerically very robust and the particle-based nature leads to elegant treatment of venting, porous leakage and gas mixing. Users find novel situations to apply the method and oftentimes new features are needed to better support these scenarios. Among these is the need of more comprehensive treatment of heat transfer. Based on kinetic molecular theory, CPM model behavior is heavily influenced by heat transfer. Yet, a full-blown coupled thermal analysis might not always be viable for a refined model. To enable modeling of heat transfer just in the neighboring structures of the CPM gas can provide a solution to this quandary. The design and implementation status will be discussed. Some other recent advances in CPM in LS-DYNA® will also be discussed. For example, airbag integrity checking reports to the user hard-to-discover abnormality in the airbag structure definitions in the input phase.

  • A New Impact Scenario for P-V Tram Certification

    M. Anghileri, L. Castelletti, M. Pirola, F. Pistochini, S. Raiti- Politecnico di Milano, Italia

    Tram crashworthiness is getting a more and more demanding issue. Simulations carried out to verify that the new tram AnsaldoBreda Sirio-Milano fulfils the prEN 15227 requirements for certification are here described. Besides a new impact scenario with characteristics closer to trams accidents is proposed. Structural enhancements so that the tram fulfils also the more severe impact condition of the new scenario are introduced.

  • A New Keyword to Apply Moving Temperature Boundary Conditions and its Application in Fused Filament Fabrication

    Jinglin Zheng, Xinhai Zhu (Livermore Software Technology, an ANSYS company), Danielle Zeng (Ford Motor Company)

    This paper introduces a new keyword, *BOUNDARY_TEMPERATURE_TRAJECTORY, which is capable of applying a prescribed temperature boundary condition within a specified volume which moves along a designated path at a given speed. Combined with LS DYNA®’s computational welding material model, it is able to simulate the process of extruding and depositing melted material onto the build platform, such as the process of fused filament fabrication. An example of printing a dog-bone-shaped plastic part is given to demonstrate the usage of this keyword. The simulation result agrees very well with experimentally measured local temperature histories, which demonstrates the validity and accuracy of this simulation approach.

  • A New Method for CrachFEM ‘Damage’ Parameter Calculation & Transfer from Autoform to LS-Dyna

    Michael Buckley - Jaguar Land Rover, Mike Selig - Autoform Development GmbH, Martin Oehm - MATFEM

  • A New Method for Efficient Global Optimization of Large Systems Using Sub-models HEEDS COMPOSE Demonstrated on a Crash Optimization Problem

    N. Chase, R. Sidhu, R. Averill (Red Cedar Technology)

    Executing full vehicle finite element simulations can be very time consuming and expensive. Compound this with the large number of evaluations required for crash optimization problems due to their complicated design landscapes, and optimization of full vehicle crash simulations becomes very computationally expensive and difficult. An ideal solution is to reduce the full vehicle down to a manageable sub-model which runs significantly quicker while maintaining the boundary constraints as if utilizing the full vehicle model. The optimization process can then be managed with this sub-model while achieving significant improvements in computational requirements. This paper will demonstrate how to optimize the a-pillar, b-pillar, roof rail, rocker, front header, and roof bow components of a car for roof crush, utilizing Ultra High Strength materials. In addition to the gauge of the individual structural components, a soft zone trigger and its location within the b-pillar are introduced as design variables. LS-DYNA® is utilized as the simulation tool with the new COMPOSE (COMPonent Optimization in a System Environment) feature within the HEEDS-MDO optimization software utilized to perform the optimization. COMPOSE is a new module that enables the use of a sub-model for optimization in a way that significantly reduces the overall optimization time while encouraging the interactions of the optimal subsystem with the global model to be consistently maintained. This creates a design that gives a similar high performance in the global model as was found in the sub-model. It is shown here that the use of COMPOSE can significantly decrease the design time for finding high performing designs for the roof crush optimization, over a traditional global optimization approach. In addition, it is shown that performing an optimization on the sub-system level by using the original boundary conditions from the global model is not a robust approach for this optimization. The study shows that to take advantage of the reduced runtime in the sub-system model, the COMPOSE technology provides a robust solution for efficient optimization of the system.

  • A New Method for the Structural Optimization of Product Families

    Larsgunnar Nilsson - Engineering Research Nordic AB, Michael Öman - Scania CV AB

    This paper discusses the problem of structural optimization of product families subjected to multiple load cases, evaluated by computationally costly finite element analysis. Product families generally have a complex composition of shared components that makes individual product optimization difficult as the relation between the shared variables is not always intuitive. More optimal is to treat the problem as a product family optimization problem. For product families subjected to multiple and computationally costly crash loads, however, the optimization problem takes too long time to solve with traditional methods. Therefore, a new optimization algorithm is presented that decomposes the family problem into sub-problems and iteratively reduces the number of sub-problems, decouple and solve them.

  • A New Model Reduction Method for Vehicle Crash Simulation

    Shinya Hayashi, Shinya Hiroi, Norio Shimizu

    When major design changes are required to satisfy product performance late in the development process, significant cost and time are required to implement them. This is a particular problem in automotive development which requires a large amount time and cost. To alleviate this, automotive manufacturers have adopted the concept of "front-loading" to identify problems early-on in the development process. “Front-loading” is defined as "the distribution of development costs or time in large proportions in the early stages of the design process”.

  • A New Modelling for Damage Initiation and Propagation of Randomly-Oriented Thermoplastic Composites

    K. Saito, M. Nishi (JSOL), S. Hayashi, M. Kan (Honda R&D)

    A new method to model damage properties of Randomly-Oriented Thermoplastic Composites (RO-FRTP) was proposed for finite element analysis (FEA). The materials are composites of thin sheets in which carbon fibers of approximately one inch in length are distributed randomly in thermoplastics resin matrix. While their material properties are intrinsically isotropic in plane from a macro perspective, RO-FRTP have complex nature of damage initiation and progression that depends on the deformation mode. In this study, the damage model that based on Continuum Damage Mechanics (CDM) was developed and the modelling method with 3D shell element for RO-FRTP was proposed. The multifunctional feature of *MAT_ADD_GENERALIZED_DAMAGE in LS-DYNA® has been utilized in order to reproduce damage properties of the material. Furthermore, several numerical studies are conducted and compared to experiments for the purpose of validation of the modelling method. Simulation results show that the modelling method can capture complex damage characteristics of the material in detail and predict deformation of structures accurately.

  • A New Simulation Method for Airbags With Multiple Compartments (Adaptive Euler Domains)

    R.S. Sadeghi, W.A. van der Veen - MSC.Software Corporation

    The paper presents a new simulation method for airbags with multiple compartments. In recent years many accidents happened with passengers that were out of position (OOP) when their airbag deployed. Therefore new safety regulations have come into effect in the USA and an airbag now has to meet several requirements that concern out of positioning. In meeting these requirements simulations of deploying airbags are very useful and are widely used. In OOP the airbag hits the passenger when it is still deploying and the pressure field is far from uniform and so there is a complicated interaction between gas flow and the deploying membrane. This calls for an analysis in which the dynamics of the airbag membrane is coupled with a CFD (Computational Fluid Dynamics) solver. To weaken the frontal blow, an airbag with multiple compartments is sometimes used. The idea is to divert the gas stream in the airbag away from the frontal direction into sideways directions. Since these airbags especially need to operate well in OOP setting the CFD approach is required. The paper presents a new method to simulate a multi-compartment airbag in which each compartment is modeled by the CFD approach and each with a separate Euler domain. Before discussing multi-compartment simulations, we present background on simulations for one airbag using one Euler mesh. In these simulations the gas flow is described by the conservation laws of mass, momentum and energy. Also modeling of the interaction between CFD solver and airbag membrane solver is discussed. The conservation laws are applied to the 3D objects that are formed by taking an Euler element and cutting away everything that is outside the airbag surface. The boundary of this 3D object is in general a multi-faceted surface that consists of: (1) Polygons that connect an Euler element to another Euler element and that are called faces. (2) Polygons that connect Euler elements to the airbag surface, and are called polpacks. In the conservation laws several surface integrals occur. Many of these integrals have to do with transport and are computed by running over faces and polpacks. This gives rise to mass being transported across faces. In most cases there is no transport across polpacks since they are part of the airbag surface. For multi-compartment simulations we have to consider multiple Euler domains. Each Euler domain models one airbag. Communication between the airbags proceeds via the holes that connect one airbag with the other. Holes are modeled as a piece of airbag surface that is fully porous. Given that the largest possible timestep depends on the mesh size, each Euler domain could be advanced with a specific timestep. This would require subcycling. For the multi-compartment application mesh sizes are expected to be of comparable magnitude and all Euler meshes are advanced with the same timestep.

  • A New Strain Rate Dependent Spot Weld Model for Automotive Crash Applications

    Dr. P.K.C. Wood - University of Warwick, Mr. M.A. Buckley - Jaguar and Land Rover, Dr. B. Walker - Ove Arup and Partners, Mr. T. Dutton - Dutton Simulation

    New spot weld failure models in a range of sheet steels have been developed for use in the virtual testing of automotive crash structures to ensure compliance to international safety requirements. The desire to balance the cost to develop the data input to spot weld failure models and their capability to predict failure in simulation tools is central to the method. Full vehicle crash simulations suggest confidence in the predictive capability of the models. This paper describes a strain rate dependent spot weld failure model for use with hexahedron (solid) elements. A spot weld may comprise one, or a cluster of four, eight or sixteen solid elements. The enhanced functional capabilities of the new spot weld model allow a force-based failure for a solid element in which maximum shear force and tension force may be a function of strain rate, and each may each be defined uniquely using a load curve. Further the strength hardening effect at higher strain rate may be defined for the solid element using a simple constitutive expression which relates the properties of the spot weld to plastic strain rate. The new model has been programmed and tested in the finite element software code LS-DYNA®. The results suggest the new spot weld model is capable of reproducing the quasi-static and high rate physical test responses with a high degree of accuracy.

  • A New Way for Multi-piece and Multi-hit Fragment Impact Simulation Using LS-DYNA

    Xudong Xin - Karagozian and Case

    The kinetic feature of weapon fragment is many small masses traveling at extremely high velocities and scattering radially from the explosion center. To simplify the fragment impact analysis, people often convert the fragment momentum into a triangular pressure load with very high magnitude and very short duration, and apply the load directly onto the target. This method may over- or under-predict the impact response due to the complicacy of fragment behaviors such as embedment, perforation and ricochet. It might encounter more difficult situation when involving multi-layer impact and penetration problem. This paper proposes a new method for fragment simulation using the contact technique provided in LS-DYNA. A program was developed which can automatically generate the LS-DYNA keyword input of node, part, initial velocity and contact surface cards for multiple pieces and sets of fragments, based on the given information about mass, location, velocity of each fragment, and other user-defined parameters. This method can be applied not only on multi-piece fragment impact simulation, but also on multi-hit problem in a realistic way. Examples of fragment impact on structure are demonstrated.

  • A New Way for the Adaption of Inverse Identified GTN-Parameters to Bending Processes

    Ioannis Tsoupis, Marion Merklein (Friedrich-Alexander-Universität Erlangen-Nürnberg)

    One major challenge in metal forming exists in sheet metal bending of modern lightweight materials like high‑strength low-alloyed steels (HSLA), since conventional methods of predicting failure in numerical simulation, like the forming limit diagram (FLD), can generally not be applied to bending processes. Moreover, fracture mechanisms are mainly depending on the microstructure, which is very fine-grained in HSLA steels composed with different alloying elements compared to established mild steels. Consequently the damage and failure behaviour of HSLA steels are changing. Especially for small curvature bending processes characterised by high gradients of strain and stress over the sheet thickness other failure criteria than the FLD have to be utilised. Within this paper a numerical study of the micromechanical based damage model Gurson-Tvergaard-Needleman (GTN, *MAT_120) is performed in LS-DYNA®, in order to realise an effective adaptability of the model for bending operations on HSLA steels. The material dependent damage parameters are determined by commonly used methodology of inverse numerical identification re-calculating the uniaxial tensile test. The minimisation of the mean squared error (MSE) of experimental and numerical global load displacement curves is realised by an optimisation algorithm using commercial software LS‑OPT®. For the adaption of the GTN-Model to the bending operation a strain-based calibration method is developed. This method is based on the comparison and adaption of the numerically calculated and the experimentally measured deformation field on the outer surface of the bent specimen. In this context the parameters are systematically varied again in the optimisation software LS-OPT. Their influence on the strain and damage evolution is analysed and discussed. On the one hand it is shown that it is possible to represent the strain evolution by adapting only one parameter instead of all parameters of the model and thus reducing the modelling effort for the user. On the other hand a big effect on the damage evolution and distribution can be identified.

  • A Next Generation Software Platform for LS-DYNA Modeling and Configurable Vertical Application Development

    H. Ouyang, Tim Palmer, Q. He - Engineering Technology Associates, Inc.

    Finite element modeling tools have undergone a transformation in recent years. These tools have been made easier to use, configurable for vertical applications and able to interact with outside applications. Such software needs to not only efficiently create models, but are also expected to interact with other software tools, be configurable and anticipate the future needs of users by being able to extend the users ability to assimilate models and other data efficiently into an LS-DYNA environment. Using the heritage of a stable, well-featured finite element modeling software, ETA has developed a new software platform to create finite element modeling software that meets the challenges of today’s users, both from an infrastructure and a data management standpoint. This will offer users an opportunity to create, share and manage models using standardized interfaces, scripting tools and both standardized and user-defined processes. This paper will present the opportunities that this new platform will offer users and the future of modeling tools that empower users of optimization and synchronous design tools.

  • A Next Generation Software Platform for LS-DYNA Modeling and Configurable Vertical Application Development

    H. Ouyang, Tim Palmer, Q. He - Engineering Technology Associates, Inc.

    Finite element modeling tools have undergone a transformation in recent years. These tools have been made easier to use, configurable for vertical applications and able to interact with outside applications. Such software needs to not only efficiently create models, but are also expected to interact with other software tools, be configurable and anticipate the future needs of users by being able to extend the users ability to assimilate models and other data efficiently into an LS-DYNA environment. Using the heritage of a stable, well-featured finite element modeling software, ETA has developed a new software platform to create finite element modeling software that meets the challenges of today’s users, both from an infrastructure and a data management standpoint. This will offer users an opportunity to create, share and manage models using standardized interfaces, scripting tools and both standardized and user-defined processes. This paper will present the opportunities that this new platform will offer users and the future of modeling tools that empower users of optimization and synchronous design tools.

  • A Non-linear Strain-rate Micro-mechanical Composite Material Model for Impact Problems

    Ala Tabiei, Sandeep Medikonda, Department of Mechanical and Materials Engineering, University of Cincinnati, Cincinnati, Ohio 45221, USA

    A micro-mechanical composite material model is developed to simulate the behavior of uni-directional composites under impact loading conditions in LS-DYNA®. The non-linear strain-rate and pressure dependency in the composite material model is accounted by the resin, which uses previously developed state-variable viscoplastic equations. These equations have been originally developed for metals, however are modified to account for the significant contributions of hydrostatic stresses typically observed in polymers. The material model also uses a continuum damage mechanics (CDM) based failure model to incorporate the progressive post-failure behavior. A set of Weibull distribution functions are used to quantify this behavior and a methodology of assigning physical significance to the choice of damage/softening parameters used in these functions is presented. The impact response of composite laminate plates has been simulated and compared to the experiments. In addition, the effect of hydrostatic stresses on impact problems has been further studied in detail. It has been observed that the predicted results compare favorably to the experiments.

  • A Non-orthogonal Material Model of Woven Composites in the Preforming Process

    Weizhao Zhang, Huaqing Ren, Biao Liang, Jian Cao, Northwestern University, Evanston, IL, USA;, Danielle Zeng, Xuming Su, Jeffrey Dahl, Ford Motor Company, Dearborn, MI, USA;, Mansour Mirdamadi, Dow Chemical Company, Midland, MI, USA, dQiangsheng Zhao, Livermore Software Technology Corporation, Livermore, CA, USA

    Woven composites are considered as a promising material choice for lightweight applications. The new LS-DYNA® material model MAT_COMPRM (MAT_293) that can decouple the strong tension and weak shear behavior of the woven composite under large shear deformation is developed for simulating the preforming of woven composites. The tension, shear and compression moduli in the model are calibrated using the tension, bias-extension and bending experiments, respectively. The interaction between the composite layers is characterized by a sliding test. Finally, the material model is validated by a double dome study.

  • A novel transversely-isotropic 3D elastic-viscoplastic constitutive law for modeling fiber matrix composites

    M. Vogler, R. Rolfes - Leibniz University Hannover, F.X.C. Andrade - University of Porto, J.Schöpfer - Daimler AG, S. Kolling - German Institute for Polymers (DKI)

    A transversely isotropic elastic-viscoplastic constitutive law with a novel 3D failure crite- rion is presented, addressing high pressure effects, strain rate sensitivity in yielding and failure and volumetric plastic strain. The constitutive equations are derived in the frame- work of transversely-isotropic invariants, which allow for a coordinate system independent formulation and an easy parameter identification. Triaxiality dependent non-linearities are taken into account and entirely different yielding behavior under uniaxial/biaxial compression, uniaxial/biaxial tension and under in-plane/transverse shear stress states is addressed. Hardening curves for each loading state can easily be input either via tabu- lated data or optionally by use of a three parameter power law. Lateral plastic straining due to volumetric plastic compression and dilatation is load path dependent as well. In order to control the lateral plastic straining in each stress state, a non-associated flow rule, assuming a plastic potential which gives the direction of the plastic flow is introduced. The applicability of this novel material law is shown by two examples.The first one is a short fiber reinforced thermoplastic PA6GF60, the second one adresses off-axis tensile and compression tests of a unidirectional carbon-epoxy IM7-8552, which is widely used in aircraft industry. For PA6GF60, a complete test setup for characterizing the novel transversely isotropic yield surface is used for validation. All test cases are simulated and compared with these experiments. The sensitivity of the plastic Poisson coefficient and the influence on the simulated load displacement curves are discussed. Strain rate effects are obtained from dynamic uniaxial tensile tests and are considered by a viscoplas- tic approach. Unidirectional carbon-epoxy IM7-8552 reveal pronounced yielding under combined shear- compression loadings as it is observed in off-axis compression tests. Fur- thermore, the glass transition temperature of epoxy resin drops from above 200◦ C to operating temperature in the presence of high pressures. This results in a change of me- chanical properties, effecting the elastic parameters as well as the yielding behavior.This change of mechanical properties and the pronounced non-linear behavior in the presence of high pressure due to matrix yielding can be modeled properly with this new approach.

  • A Numerical Investigation for Rock Fall Impact Behavior of Pithead of Tunnel with Falling Weight Impact Loading

    Abdul Qadir Bhatti, Khaliq U Rehman Shad - National University of Sciences & Technology NUST, Pakistan, Norimitsu Kishi - Muroran Institute of Technology, Muroran

    In order to establish a rational impact resistant design procedure for Arch type rock-shelter based on not only allowable stress design but also on ultimate state design and/or performance based design method, impact resistant capacity and/or maximum input impact energy for the RC structures must be clearly estimated. At present, the RC structures have been designed statically based on allowable stress design method. Here, maximum input impact energy for reaching ultimate state was numerically estimated by means of three-dimensional elasto-plastic finite element method for existing real arch-type RC rock-shelters with sand-cushion and EPS layer under falling heavy- weight impact loading. In this numerical analysis, solid elements were employed for concrete, falling heavy-weight and sand-cushion, and beam elements for rebar. Drucker-Prager and rebar yield criteria were used as material constitutive law for concrete and rebar, respectively. Cracks were estimated by allowing tensile stress cut-off at reaching at the tensile strength. In this paper, weight impact force, total axial force at the side-walls, displacement wave at the loading point, and crack patterns of the shelter at the time occurring of the maximum displacement are output. The results obtained from this study are as follows; 1). About twice the bending moment are generated at the edge as compare to the centre of falling weight in the direction of road axis. 2) It was observed that maximum response generation time of the bending moment and shear force is different. 3) When three layer buffer structure is set up in the tunnel pithead part, the sectional force can be decreased to about 1/2 to 1/5 in the mid-span compared with the case for sand cushion. Keywords: Pithead of tunnel; Three-layered absorbing system; Transmitted impact force; elasto-plastic response

  • A Numerical Investigation into the Injury Potential of Three-year-old Children Seated in Forward Facing Child Safety Seats During Side Impact Crashes in Far Side Configurations

    Qian Wang, Tanya Kapoor, William Altenhof - University of Windsor, Andrew Howard - The Hospital for Sick Children

    This research focuses on the injury potential of children seated in forward facing child restraint seats during side impact crashes. Side dynamic sled tests were conducted by NHTSA using the existing FMVSS 213 seat fixture oriented at both 90° and 45° relative to the motion of the sled buck. A half sine pulse and a scaled FMVSS 213 pulse were used in the tests. All the tests were conducted at a test velocity of 32 km/h (20 mph) and a peak acceleration of 17 g’s. A forward-facing Hybrid III 3-year-old child dummy positioned in a child restraint seat (CRS) with LATCH and the top tether in far side configurations were used in the tests. Details of the sled tests were stated in FMVSS 213 ANPRM. A finite element model of the child restraint seat was developed using FEMB for simulation in LS- DYNA. The child seat model, which included all CAD surfaces provided by Century/Graco Corporation, was fully deformable and was previously validated for frontal impacts. Three side impact simulations were completed for data comparison. (i) using the half sine acceleration pulse with the seat oriented at 90° relative to the motion of the sled, (ii) using the half sine acceleration pulse with the seat oriented at 45° relative to the motion of the sled, and (iii) using scaled FMVSS 213 acceleration pulse with the seat oriented at 90° relative to the motion of the sled. Validation of the numerical model was completed by comparing the head injury criteria (HIC) values and chest accelerations from the experimental and numerical tests. The simulation results were generally in good agreement to the experimental observations. Further studies were conducted to confine lateral movement of the dummy’s head by adding energy absorbing foam blocks in the head region of the CRS. It was observed from the simulation results that foam padding was effective in reducing the injury potential of the child dummy.

  • A Numerical Investigation into HIC and Nij of Children for Forward and Rearward Facing Configurations in a Child Restraint System

    William Altenhof, Rita Turchi - University of Windsor

    This study explores the various differences in potential for injury in 3-year-old children in the case of a frontal collision. A crash analysis between forward and rearward facing children, both restrained in a five-point child restraint, was performed using numerical simulation methods. This comparison was carried out by conducting numerical simulations of these situations using the criteria outlined in FMVSS 213. The injuries that were assessed included neck and head injury, as those types of injuries can be the most devastating and sometimes fatal. In this study, it was determined that when the 3-year-old Hybrid III dummy model is in a rearward facing position, the child sustains less neck loads and head accelerations than the forward facing dummy model. In other words, a 3- year-old child would sustain lower levels of Neck Injury Criteria (Nij) and Head Injury Criteria (HIC). In fact, the difference in the Nij values is quite significant. In North America, the standard for restraining young children states that for a child under the age of 12 months, the child should be restrained in a child seat facing the rear of the vehicle. After 12 months of age, the child can then face forward. This study has opened the forum to debate if this standard should be reconsidered as to save the lives of thousands of children being injured and dying unnecessarily at the hands of vehicle collisions.

  • A Numerical Investigation of Human Biomechanical Response under Vertical Loading Using Dummy and Human Finite Element Models

    Costin D. Untaroiu, Jacob Putnam (Virginia Tech)

    The safety of aerospace transport for both fixed and rotary wing aircraft is evaluated primarily through testing of anthropometric test devices (ATDs), commonly known as crash test dummies. While the majority of the ATDs were certified under automotive horizontal impact conditions, their biofidelity under vertical loading is less known. The objective of this study was to compare the THOR-K dummy model response to the corresponding response of the THUMS human FE model in the same impact conditions. A series of vertical drop tests were performed on a THOR- K crash dummy. Impact conditions were replicated in the FE simulation based on pre-impact velocities and crash pulse decelerations measured during testing. FE simulations were run with both dummy and human FE models using LS-DYNA ® software. Comparisons between injury prediction of dummy and human models were also performed. While a good correlation was observed in terms of neck load between both FE models, the THUMS spine showed a higher bending flexibility within the sagittal plane. In addition, differences were observed in pelvis region where a significant bouncing was observed in THOR model, but not in the THUMS model. The comparison of THOR FE model with THUMS human model may help to improve the THOR design and define better injury criteria for vertical loading.

  • A Numerical Investigation on the Ballistic Performance of Ceramic Composite Armors against EFP Threats

    M. Emin Akca, M. Bartu Ünal, Koray Kaya, H. Hüseyin Türkmen

    The increasing destructiveness of explosive-formed penetrators or projectiles (EFPs) in modern warfare has posed significant challenges in developing effective armored solutions incorporating advanced ceramics as crucial components, offering enhanced protection against high-velocity-formed projectiles. [1] In other words, Explosively Formed Penetrators pose a significant threat to military vehicles, necessitating the development of advanced armor solutions to counteract their destructive potential. Thus, Finite Element Analysis (FEA) research is crucial for the armor system against this threat. In addition, since EFP tests are costly and time-demanding, performing these experiments with FEA provides significant cost and performance efficiency. This study analyzes the composite armor system integrating Nurol Teknoloji [2] ceramics against EFP threats utilizing LS-DYNA, a program for nonlinear dynamic analysis of structures in three dimensions.

  • A Numerical Investigation of Turbulent Flow in Circular U-Bend

    A. Miloud, M. Aounallah, O. Imine, M. Guen (University of Science and Technology of Oran Algeria)

    A numerical investigation of Turbulent flows through a circular 180° curved bend with defined as the bend mean radius to pipe diameter for a Reynolds number of 4.45×104 is presented in this study . The computation domain is performed for a U-Bend with full long pipes at the entrance and at the exit. Two turbulence models were tested in this work.

  • A Numerical Model for Tri-Axially Braided Composites Under High Velocity Soft Projectile Impact

    Jingyun Cheng, Wieslaw K. Binienda - The University of Akron, Akron OH

    A simplified methodology has been developed for modeling 2D tri-axially braided composite plates impacted by a soft projectile using an explicit nonlinear finite element analysis code LS-DYNA. Fiber preform architecture is modeled using shell elements by incorporating the fiber preform architecture at the level of integration points. The soft projectile was modeled by an Equation of State (EOS). An arbitrary Lagrangian-Eulerian (ALE) formulation is used to resolve numerical problems caused by large projectile deformation. The computed results indicate that this numerical model is able to simulate a tri-axially braided composite undergoing a ballistic impact effectively and accurately, including the deformation and failure with a reasonable level of computational efficiency.

  • A numerical study of the effect of geometrical factors on bi-layered tube hydroforming

    Abed Alaswad, Abdul Ghani Olabi - Dublin City University

    Tube hydroforming is one type of unconventional metal forming process in which high fluid pressure and axial feed are used to deform a tube blank in the desired shape. Bi-layered tube hydroforming is suitable to produce bi-layered joints which can be used in special applications such as aerospace, oil production, and nuclear power plants. In this work a finite element study was performed using ANSYS LS-DYNA to investigate the effect of geometrical factors (Tube length, Initial thickness, and Corner radius) on bi-layered tube hydroforming of X branch. Bulge height, Von mises stresses, and thickness distribution were studied for the hydroformed part. Suggestions were made to increase formability of process by adjusting geometrical factors. Optimization was performed to get minimum thickness reduction for a specific design.

  • A numerical study of the effect of geometrical factors on bi-layered tube hydroforming

    Abed Alaswad, Abdul Ghani Olabi - Dublin City University

    Tube hydroforming is one type of unconventional metal forming process in which high fluid pressure and axial feed are used to deform a tube blank in the desired shape. Bi-layered tube hydroforming is suitable to produce bi-layered joints which can be used in special applications such as aerospace, oil production, and nuclear power plants. In this work a finite element study was performed using ANSYS LS-DYNA to investigate the effect of geometrical factors (Tube length, Initial thickness, and Corner radius) on bi-layered tube hydroforming of X branch. Bulge height, Von mises stresses, and thickness distribution were studied for the hydroformed part. Suggestions were made to increase formability of process by adjusting geometrical factors. Optimization was performed to get minimum thickness reduction for a specific design.

  • A Numerical-Experimental Investigations on Crash Behaviour of Skin Panels during a Water Impact Comparing ALE and SPH Approaches

    Eng. Edoardo Francesconi, Prof. Marco Anghileri - Politecnico di Milano

    Water landings in emergency are likely to have tragic consequences for helicopters. Most of the safety devices developed to enhance helicopter crashworthiness have been designed referring to ground impacts and they might be not effective in case of water landings. At LAST, the crash labs of Politecnico di Milano, water impact drop tests were carried out to deepen the knowledge of the event dynamics and to collect reliable data to validate numerical models. The water impact behaviour of skin panels made of aluminium alloy was investigated, in particular the panel failure due to water impact pressure. Drop tests with several drop heights and different impacting masses were performed measuring accelerations of the test article. In the second part of the research, the tests were numerically reproduced adopting ALE and SPH approaches to model the fluid region. The numerical results were compared both ones to the others and to the experimental tests in terms of impact dynamics and data acquired. As a result, a satisfactory correlation was achieved and guidelines to model fluid regions adopting ALE and SPH approaches were drawn.

  • A Numerical-Experimental Investigations on Crash Behaviour of Skin Panels during a Water Impact Comparing ALE and SPH Approaches

    Eng. Edoardo Francesconi, Prof. Marco Anghileri - Politecnico di Milano

    Water landings in emergency are likely to have tragic consequences for helicopters. Most of the safety devices developed to enhance helicopter crashworthiness have been designed referring to ground impacts and they might be not effective in case of water landings. At LAST, the crash labs of Politecnico di Milano, water impact drop tests were carried out to deepen the knowledge of the event dynamics and to collect reliable data to validate numerical models. The water impact behaviour of skin panels made of aluminium alloy was investigated, in particular the panel failure due to water impact pressure. Drop tests with several drop heights and different impacting masses were performed measuring accelerations of the test article. In the second part of the research, the tests were numerically reproduced adopting ALE and SPH approaches to model the fluid region. The numerical results were compared both ones to the others and to the experimental tests in terms of impact dynamics and data acquired. As a result, a satisfactory correlation was achieved and guidelines to model fluid regions adopting ALE and SPH approaches were drawn.

  • A PARAMETRIC AND USERFRIENDLY APPROACH TO INCREMENTAL PROCESS SIMULATION OF SHEET METAL FORMING

    Dr. Victor Apanovitch, Stefan Huhn - Forming Technologies Inc.

    With a steady increase in computational power and decrease in hardware costs during the last few years, the incremental process simulation in the area of sheet metal forming is considered a state-of- the-art tool during the development process at OEMs and many, mainly larger, suppliers. However, the existing pre-processing tools do not support a template based analysis setup that can prevent the need for highly skilled personnel in order to set-up an analysis application and, therefore; open the door for an LS-DYNA based stamping simulation for smaller companies that do not have the skill set and manpower available to do the analysis setup using existing tools. The presented solution FormingSuite FastIncremental, is an analysis environment that provides the end user with a dramatically simplified solution for the setup process for incremental stamping analysis using the LS-DYNA solver. This is done through the automation of tool definition/extraction and an automated setup for blank on curved binder combined with other techniques to enable fast solving time. To ensure an optimized solution time, a combination of inverse and incremental finite element tools is used. This combination can lead to enormous time savings in blank development and positioning, tool definition, binder wrap calculation as well as in simulation run-time while reliable results are produced. The user interface is CAD-like and geared towards an average industry practitioner; definition of complete forming processes as well as the application of boundary conditions is mapped on the first form geometry as it is commonly used on A-layouts in the industry. Associative and regenerative mechanisms ensure that changes made to the first form geometry or to forming conditions are automatically propagated throughout the complete analysis process, ensuring that geometry, forming conditions and results are always in sync. This also means that in conjunction with an automated tool generation, the presented tool enables an automated batch mode processing for pre-defined part groups without any user interaction other than evaluating the calculated results.

  • A PARAMETRIC AND USERFRIENDLY APPROACH TO INCREMENTAL PROCESS SIMULATION OF SHEET METAL FORMING

    Dr. Victor Apanovitch, Stefan Huhn - Forming Technologies Inc.

    With a steady increase in computational power and decrease in hardware costs during the last few years, the incremental process simulation in the area of sheet metal forming is considered a state-of- the-art tool during the development process at OEMs and many, mainly larger, suppliers. However, the existing pre-processing tools do not support a template based analysis setup that can prevent the need for highly skilled personnel in order to set-up an analysis application and, therefore; open the door for an LS-DYNA based stamping simulation for smaller companies that do not have the skill set and manpower available to do the analysis setup using existing tools. The presented solution FormingSuite FastIncremental, is an analysis environment that provides the end user with a dramatically simplified solution for the setup process for incremental stamping analysis using the LS-DYNA solver. This is done through the automation of tool definition/extraction and an automated setup for blank on curved binder combined with other techniques to enable fast solving time. To ensure an optimized solution time, a combination of inverse and incremental finite element tools is used. This combination can lead to enormous time savings in blank development and positioning, tool definition, binder wrap calculation as well as in simulation run-time while reliable results are produced. The user interface is CAD-like and geared towards an average industry practitioner; definition of complete forming processes as well as the application of boundary conditions is mapped on the first form geometry as it is commonly used on A-layouts in the industry. Associative and regenerative mechanisms ensure that changes made to the first form geometry or to forming conditions are automatically propagated throughout the complete analysis process, ensuring that geometry, forming conditions and results are always in sync. This also means that in conjunction with an automated tool generation, the presented tool enables an automated batch mode processing for pre-defined part groups without any user interaction other than evaluating the calculated results.

  • A Path Towards Including Batteries in Electric or Hybrid Car Crash Simulations with LS-DYNA®

    Pierre L’Eplattenier, Iñaki Çaldichoury (Livermore Software Technology, LLC)

    Safety is an important functional requirement in the development of large-format, energy-dense, lithium-ion (Li-ion) batteries used in electrified vehicles. Many automakers have dealt with this issue by enclosing the batteries into protective cases to prevent any penetration and deformation during the car crash. But with the range of electric vehicle increasing and thus the size of the batteries, a more detailed understanding of a battery behavior under abuse becomes necessary. Computer aided engineering (CAE) tools that predict the response of a Li-ion battery pack to various abusive conditions can support analysis during the design phase and reduce the need for physical testing. In particular, simulations of the multi-physics response of external or internal short circuits can lead to optimized system designs for automotive crash scenarios. The physics under such simulations is quite complex, though, coupling structural, thermal, electrical and electrochemical. Moreover, it spans length scales with orders of magnitude differences between critical events such as internal shorts happening at the millimeter level, triggering catastrophic events like the thermal runaway of the full battery. The time scales also are quite different between the car crash happening in milliseconds and the discharge of the battery and temperature surge taking minutes to hours. A so called “distributed Randles circuit” model was introduced in LS-DYNA in order to mimic the complex electrochemistry happening in the electrodes and separator of lithium ion batteries [1][2][3]. This model is based on electrical circuits linking the positive and negative current collectors reproducing the voltage jump, internal resistance and dumping effects occurring in the active materials. These circuits are coupled with the Electromagnetics (EM) resistive solver to solve for the potentials and current flow in the current collectors and the rest of the conductors (connectors, busses, and so forth). The EM is coupled with the thermal solver to which the joule heating is sent as an extra heat source, and from which the EM gets back the temperature to adapt the electrical conductivity of the conductors as well as the parameters of the Randles circuits [1]. One of the advantages of the Randles circuit model is the relative easiness to introduce internal short circuits by just replacing the Randles circuits in the affected area by a short resistance [1][3]. The Randles circuit model also is coupled with the mechanical solver of LS-DYNA where the deformations due to a battery crush allow the definition of criteria to initiate internal shorts [1]. The Randles circuit model can be used either on a solid element mesh that include all the layers of a cell [1][2][3], or using composite Tshells [4][5]. In the second case, the mechanics is solved on the composite Tshell, but an underlying solid mesh with all the layers still has to be built to solve the EM and the thermal. This implies very large meshes and hence simulation times when dealing with many cells, let alone modules, packs or a full battery. This new Battery Macro (BatMac) model allows simulating a cell with very few layers of elements (down to one). Two fields exist at each node of the mesh, representing the potential at the positive and negative current collectors. These two fields are connected by a Randles circuit at each node. It still is possible to include external and internal shorts. The internal shorts can be locally created depending on local values of different mechanical, thermal or EM parameters. The Joule Heating generated by the current leaking through the short resistance is sent to the thermal solver.

  • A Performance Study of LS-DYNA on Vehicle Crash Simulation

    Yih-Yih Lin - Hewlett-Packard Company, Cing-Dao Kan - The George Washington University

    For computer companies to design cost-effective machines for LSTC to optimize the software and for the LS-DYNA user to make an intelligent choice of machines, various factors that affect LS-DYNA’s performance must be investigated and understood. Therefore, we have embarked such an investigation with machines from both Hewlett- Packard and SGI. Many results are reported here. The factors considered include the following: memory systems, SMP vs. MPP LS-DYNA, single vs. double precision, cluster vs. ccNUMA configuration.

  • A Peridynamic Model for Damage Prediction of Fiber-reinforced Composite Laminate

    Bo Ren, C. T. Wu, Livermore Software Technology Corporation

    This paper presents the keywords for a bond-based peridynamic model in LS-DYNA® to predict the damage of fiber reinforced composite laminates. To represent the anisotropy of a laminate by the peridynamic model, a lamina is simplified as a transversely isotropic media under the plane stress condition. The laminated structure is modeled by stacking the surface mesh layers along the thickness direction according to the laminate sequence. The bond stiffness can be evaluated using the engineering material constants, based on the equivalence between the elastic energy density in the peridynamic theory and the elastic energy density in the classic continuum mechanics theory. Benchmark tests are conducted to verify the proposed model. The numerical results illustrate that the elastic behavior of a laminate can be simulated accurately in comparison to experimental data. In terms of damage analysis, the proposed model can capture the dynamic process of the complex coupling of the inner-layer and delamination damage modes.

  • A Pre-processor Software for the Calibration of Material Models for LS-DYNA

    H. Lobo (Matereality)

    LS-DYNA contains a wealth of material models that allow for the simulation of transient phenomena. These models are often quite complex and difficult to calibrate. We present CAE Modeler, a generalized pre-processor software used to convert material property data into material parameters for different material models used in CAE. In this paper, CAE Modeler is used to streamline the conversion of rate dependent stress-strain data into material parameters for the MAT_024 material model. The interactive software is capable of handling all three rate dependency options of MAT_024 and outputs a data file that can be read directly into LS-DYNA. Support for other material models is envisaged.

  • A pregnant woman model to study injury mechanisms in car crashes

    Jérémie Pérès, Michel Behr, Lionel Thollon - IFSTTAR, Kambiz Kayvantash - CADLM

    Based on statistical analysis it has been estimated that 3 to 7% of pregnant women experience trauma, 2 third of those trauma are caused by car accidents. According to one epidemiologic study, the frequency of foetal losses could exceed the death frequency of children aged 0 to 4. Some numerical and experimental tools have recently been developed so as to better understand injury mechanisms leading to foetal losses, nevertheless shortcomings regarding the anatomy of the models must be outlined. Indeed they lack internal organs whereas there is a direct interaction with the uterine wall. Moreover the simplified amniotic fluid model (lagrangian) often implemented is not validated. To fulfil the need of an anatomically precise pregnant woman model, a first finite element model of a 9 month pregnant woman has been developed and validated via a PMHS experimental approach. This model was based on the Humos 50th centile male model and a simplified model of the amniotic fluid was used (Lagrangian). This paper will present the development and validation of the second generation of this model using the LS Dyna software. The geometry of the Humos 50th centile male model was adapted to the anatomy of a 50th centile woman using scaling techniques with a special focus on the pelvis. The model integrates the uterine wall, the foetus, the placenta and an Euler model for the amniotic fluid and represents the anatomy of a 7 month pregnant woman. The uterus is surrounded with main internal organs and bones. An improved PMHS approach was used for validation purpose. Some belt loading of the abdomen and crash tests were realized and compared to the numerical response of the model in similar loading conditions. The pregnant numerical model exhibited a response in agreement with the PMHS tests and will be used to investigate mechanisms leading to fetal losses. A study on parameters influencing the risk of fetal loss is also projected and could ultimately lead to specific safety systems designs.

  • A Process for Robust Design of a Vehicle Front Structure Using Statistical Approach

    Masahiro OKAMURA (JSOL Corporation)

    In recent years, it has become more and more important to take scatter into account in automotive industry. Liability and performance has been guaranteed by adding safety margin to its target in the past. However, needs in cost reduction and trade-off of conflicting requirements do not allow manufacturers enough amount of safety margin any longer[1]. One way to reduce scatter in product performance is to control production quality. However, too much control increases managing cost, and scatter cannot be reduced more than tolerance specified by standards. There are some studies showing major scatters in response are sensitive to boundary conditions such as dummy position and offset or angle of crash barriers[1,2]. However, these are set up by third parties in hardware tests so that the parameters are beyond control[3]. For the reasons above, realistic approach for the problem is to enhance product design which absorbs scatter in production process and boundary conditions. Conventional methods based on design space scan[4] only visualize non-linear transformation of input/output variables, which illustrate relationship of scatters, and physical mechanisms and how scatters propagate is a black box. In this study, scatter propagation mechanism is visualized based on statistical calculation, and structural design is enhanced in order to reduce scatter using the front side structure of an automobile as an example. A process for analyzing scatter propagation mechanisms using statistical analysis software DIFFCRASH is proposed. The trigger of bifurcation is located, selection of deformation mode is made, mechanism of the bifurcation is studied, and design modification is made to stabilize the deformation mode.

  • A Process of Decoupling and Developing Body Structure for Safety Performance

    John M. Madakacherry, Martin B. Isaac, Dr. Charles A. Bruggeman - General Motors, Dr. David Eby - CD-Adapco, Dr. Akbar Farahani - ETA, Inc., Dr. Ron C. Averill - Red Cedar Technology

    This paper describes a novel approach of decoupling and developing local structures for crash performance . The process discussed here enables quick development of local structure to address packaging changes in a mass efficient manner. Hundreds of design choices compatible with other design constraints were evaluated to select the optimized design. Here optimum is defined as the design that met the required parameters (crashworthiness, NVH, package, manufacturability and robustness) at the minimum mass. A large number of choices could be evaluated by using a highly simplified simulation process, since the goal was often making an A-to-B choice at a local level, as opposed to predicting exact performance at a system level. The primary focus of mass reduction was efficiency of the load path strategy, and exploitation of the unique geometrical shapes feasible in the hydroforming process. The designs were also rendered robust through a Montecarlo Simulation process for manufacturing variations and small variations in angle of impact. A subset of the new design was incorporated into a vehicle, which was tested full-scale under the ODB format. Cost constraints prevented complete rebuilding of the load path. The optimized test vehicle had comparable performance when compared to the original design, although the mass of load carrying members was reduced by 20%.

  • A Process of Decoupling and Developing Optimized Body Structure for Safety Performance

    John M. Madakacherry, Martin B. Isaac, Dr. Charles A. Bruggeman - General Motors, Dr. David Eby - CD-Adapco, Dr. Akbar Farahani - ETA, Inc., Dr. Ron C. Averill - Red Cedar Technology

    A large class vehicle meeting NCAP front crash and 40-mph 40% Offset Deformable Barrier (ODB) Impact performance was modified and tested to verify a new load path strategy using hydroformed structure and new analytical tools to reduce the mass of the vehicle while meeting the same or better performance as in the original design. The new approach was used for developing the load path strategy of a complex system model by decomposing it into structural subsets. Components in the load path were developed primarily through decoupled structural simulations. The method facilitated evaluation of a large number of design choices compatible with other design constraints. The primary focus of mass reduction was efficiency of load path strategy and exploitation of unique geometrical shapes feasible in a motor compartment rail hydroforming process using new optimization techniques (HEEDS). In addition, the components were made insensitive to prescribed variations to insure robust system level performance. A subset of the new optimized design was incorporated into the ODB test vehicle for verifications. The test vehicle (original architecture and new hydroformed motor compartment structure) had comparable performance though the mass of new vehicle load carrying members was 20% less.

  • A Quadratic Pipe Element in LS-DYNA®

    Tobias Olsson, Daniel Hilding (DYNAmore Nordic AB)

    Analysis of long piping structures can be challenging due to the enormous number of shell/solid elements that would be required to model a piping structure accurate. In that context a new beam element has been developed that can, if used correctly, reduce the number of elements used in a pipe simulation. Since it is constructed of 3 nodes it is perfect for describing pipe bends, so called elbows. This documentimplemented inDYNA R7 [1]. is meant as an introduction and modelling techniquesLS-DYNA® R7.0.0 but improvements are implementedfor the elbowin the comingelement. It is update of LS-DYNA R7

  • A Rate-Dependent, Elasto-Plastic Cohesive Zone Mixed-Mode Model for Crash Analysis of Adhesively Bonded Joints

    Stephan Marzi, Olaf Hesebeck, Markus Brede - Fraunhofer IFAM, Felix Kleiner - Henkel AG & Co. KGaA

    Presently, there are various cohesive zone models implemented in LS-DYNA. The simplest one consists of a bi-linear traction separation-law in both modes I and II. Further models allow more complicated shapes of the traction-separation law, such as the material model of Tvergaard and Hutchinson or the General Cohesive Zone Model. However, none of these implemented models consider rate-dependency or effects of plasticity. Crash-optimized structural adhesives used in automotive structures, as for example Henkel Terokal 5077, often show a rate-dependent elastic-plastic material behaviour. An extended mixed-mode co- hesive zone model is proposed in this paper. The model considers the effects of rate-dependency and plasticity, and therefore is able to predict the failure of adhesively bonded joints more precisely than the common models. The material parameters describing the rate-dependency of yield strengths or critical energy release rates can be identified directly by (fracture) mechanical tests. The new model is validated by simulations of single lap-shear, T-peel, End-Loaded Shear Joint (ELSJ) and Tapered Double Cantilever Beam (TDCB) tests. A comparison of numerical and experimental results shows the benefits and the limitations of the new model, which will be available from one of the next versions of LS-DYNA. Its official name will be MAT COHESIVE MIXED MODE ELASTOPLASTIC RATEDEPENDENT, or in short MAT 240. The tests were proceeded at velocities ranging over several orders of magnitude. The results, which depend strongly on the test velocity, are predicted well by the new model. Further advantages are seen, when simulating a specimen unloading during a TDCB test. The irreversible displacement after unloading, which is caused by the adhesive’s plasticity, is obtained also in simulations when using the new model. Finally, a side-impact test on a floor pan is simulated, using the new model to predict the failure of adhesive bond lines connecting a cross beam to the structure. The crash tests were performed by Adam Opel GmbH. First simulations of such impact tests, using MAT 138 to model the adhesive layer, were already presented at the recent German LS-DYNA-Forum in Bamberg. The new results obtained with the elastic-plastic, rate-dependent MAT 240 show a good agreement with the experimentally observed behaviour. Thus, the model has been successfully employed in the crash simulation of a large, bonded vehicle structure.

  • A Rate-Dependent, Elasto-Plastic Cohesive Zone Mixed-Mode Model for Crash Analysis of Adhesively Bonded Joints

    Stephan Marzi, Olaf Hesebeck, Markus Brede - Fraunhofer IFAM, Felix Kleiner - Henkel AG & Co. KGaA

    Presently, there are various cohesive zone models implemented in LS-DYNA. The simplest one consists of a bi-linear traction separation-law in both modes I and II. Further models allow more complicated shapes of the traction-separation law, such as the material model of Tvergaard and Hutchinson or the General Cohesive Zone Model. However, none of these implemented models consider rate-dependency or effects of plasticity. Crash-optimized structural adhesives used in automotive structures, as for example Henkel Terokal 5077, often show a rate-dependent elastic-plastic material behaviour. An extended mixed-mode co- hesive zone model is proposed in this paper. The model considers the effects of rate-dependency and plasticity, and therefore is able to predict the failure of adhesively bonded joints more precisely than the common models. The material parameters describing the rate-dependency of yield strengths or critical energy release rates can be identified directly by (fracture) mechanical tests. The new model is validated by simulations of single lap-shear, T-peel, End-Loaded Shear Joint (ELSJ) and Tapered Double Cantilever Beam (TDCB) tests. A comparison of numerical and experimental results shows the benefits and the limitations of the new model, which will be available from one of the next versions of LS-DYNA. Its official name will be MAT COHESIVE MIXED MODE ELASTOPLASTIC RATEDEPENDENT, or in short MAT 240. The tests were proceeded at velocities ranging over several orders of magnitude. The results, which depend strongly on the test velocity, are predicted well by the new model. Further advantages are seen, when simulating a specimen unloading during a TDCB test. The irreversible displacement after unloading, which is caused by the adhesive’s plasticity, is obtained also in simulations when using the new model. Finally, a side-impact test on a floor pan is simulated, using the new model to predict the failure of adhesive bond lines connecting a cross beam to the structure. The crash tests were performed by Adam Opel GmbH. First simulations of such impact tests, using MAT 138 to model the adhesive layer, were already presented at the recent German LS-DYNA-Forum in Bamberg. The new results obtained with the elastic-plastic, rate-dependent MAT 240 show a good agreement with the experimentally observed behaviour. Thus, the model has been successfully employed in the crash simulation of a large, bonded vehicle structure.

  • A Real World Approach for using LS-DYNA to Achieve True Springback Compensation on SS Components During Forming

    M. Clarke - Continental Tool and Die, J. He - Engineering Technology Associates, Inc., X. Zhu - LSTC

    Springback is every tool designer’s nightmare. A tool designer can make a die adjustable for some areas that need to be over-hit. Most parts are sprung throughout their entire surface. In these cases the entire part would need adjustment. Almost every time the die always requires a re-cut/re-work to put the part in spec. This re-work and re-cut is a time consuming, trial and error method that takes shop resources which typically are not available near the end of a build. This presentation illustrated a method which uses DYNAFORM/LSDYNA as the analysis tool, associates with the measurement procedure, provides a complete process and a effective way for the springback compensation needs. This procedure saves hours of measurement and modelling time. In many cases, a single re-cut of the die is all that would be required to achieve the correct compensation in even the most difficult parts.

  • A Real World Approach for using LS-DYNA to Achieve True Springback Compensation on SS Components During Forming

    M. Clarke - Continental Tool and Die, J. He - Engineering Technology Associates, Inc., X. Zhu - LSTC

    Springback is every tool designer’s nightmare. A tool designer can make a die adjustable for some areas that need to be over-hit. Most parts are sprung throughout their entire surface. In these cases the entire part would need adjustment. Almost every time the die always requires a re-cut/re-work to put the part in spec. This re-work and re-cut is a time consuming, trial and error method that takes shop resources which typically are not available near the end of a build. This presentation illustrated a method which uses DYNAFORM/LSDYNA as the analysis tool, associates with the measurement procedure, provides a complete process and a effective way for the springback compensation needs. This procedure saves hours of measurement and modelling time. In many cases, a single re-cut of the die is all that would be required to achieve the correct compensation in even the most difficult parts.

  • A Review of S-ALE Solver for Blast Simulations

    I. Kurtoglu, B. Balaban (FNSS Savunma Sistemleri)

    Blast modeling and simulation is a very important field in the military land vehicle industry. Increasing demands for higher protection levels leads the engineers to more challenging design and simulation cases. In most situations, Arbitrary Lagrange Euler (ALE) method is the most well-known method for blast simulations and also for determining the effects of blast loads on structures. Various studies are performed for the effect of mesh size and the domain shape for traditional ALE solver of LS-DYNA. The newly implemented S-ALE solver is stated to give shorter simulation times and also less memory requirements using the advantage of structured mesh. In this work, the S-ALE solver is compared to the traditional ALE solver for mine blast in steel pod. Different mesh sizes and advection methods are used for comparison. In addition to the displacement, momentum and deformation pattern, the solution times and memory requirements are also examined. Fluid-structure interaction (FSI) performance for solid interfaces is reviewed, as well.

  • A Review of S-ALE Solver for Blast Simulations

    I. Kurtoglu, B. Balaban (FNSS Savunma Sistemleri)

    Blast modeling and simulation is a very important field in the military land vehicle industry. Increasing demands for higher protection levels leads the engineers to more challenging design and simulation cases. In most situations, Arbitrary Lagrange Euler (ALE) method is the most well-known method for blast simulations and also for determining the effects of blast loads on structures. Various studies are performed for the effect of mesh size and the domain shape for traditional ALE solver of LS-DYNA. The newly implemented S-ALE solver is stated to give shorter simulation times and also less memory requirements using the advantage of structured mesh. In this work, the S-ALE solver is compared to the traditional ALE solver for mine blast in steel pod. Different mesh sizes and advection methods are used for comparison. In addition to the displacement, momentum and deformation pattern, the solution times and memory requirements are also examined. Fluid-structure interaction (FSI) performance for solid interfaces is reviewed, as well.

  • A Review of Sixteen Years of LS-DYNA® Application in Stamping Manufacturing Engineering at Chrysler, LLC

    Yang Hu, Changqing Du and Shyam Kariat - Chrysler, LLC, Li Zhang - Livermore Software Technology Corporation

  • A Review of Strucural Part Modelling for Blast Simulations

    G. Balaban, I Kurtoğlu (FNSS Savunma Sistemleri)

    In this study, the effects of various element formulations and mesh sizes are investigated for buried charge simulations using the non-linear finite element code LS-DYNA®. Simulations are performed according to the real test conditions and the results are compared with the plate level mine blast experiments. Tests are carried out using a test setup which is designed and manufactured by FNSS. The blast simulations are examined using ALE method. Simulation model consists by ALE domain which includes soil, air and the explosive definitions and Lagrange domain for the bottom and side plates of the vehicle. The evaluated test plate is made of RHA steel with 20 mm thickness. Simplified Johnson Cook material model is used and the parameters are determined by Split-Hopkinson Pressure Bar tests. Plates are modelled using shell, solid and thick shell elements with different element formulations. Consequently, the elastic and plastic deformation results, effective plastic strain distributions, pressure histories and the cpu times are compared. Furthermore, the advantage and disadvantages of the considered formulations and parameters are presented.

  • A review of the state-of-the-art in vehicle modeling for crashworthiness analysis using LSDYNA

    Paul du Bois

  • A Roadmap to Linear and Nonlinear Implicit Analysis with LS-DYNA

    G. Laird (Predictive Engineering)

    The default LS-DYNA settings are tailored for running large explicit analyses. For new and even experienced users, it can be challenging setting up an implicit LS-DYNA analysis to match analytical solutions or other standard implicit FEA codes. For example, the default element formulations are based on single-point integration whereas implicit analyses benefits from full-integration. A series of example problems are provided that will allow the simulation engineer to exactly match industry standard implicit codes (complete keyword decks can be found at DYNAsupport.com). Along with these example decks, CPU-scaling results will be presented for each implicit analysis type from linear to nonlinear.

  • A Robust Cohesive Zone Model for Cyclic Loading

    Ala Tabiei, Wenlong Zhang (University of Cincinnati)

    Cohesive element approach is a promising way to simulate crack propagation. Commonly used cohesive laws include bilinear law, trapezoidal law and exponential law. However, research has found that when exponential cohesive law is unloading or reloading, the traction curve cannot remain continuous when the mixed mode ratio changes. (Kregting 2005) [1] In this paper, the discontinuity behavior of exponential law is discussed and a remedy is given to handle that. Instead of using a constant unloading slope, we use an unloading and reloading slope that changes with mixed mode ratio, like the damage parameter used in bilinear model. Improved Xu-Needleman’s exponential cohesive law will be used as an example to show this improvement. Its application in cyclic loading for fatigue failure is presented.

  • A SEISMIC POST ELASTIC BEHAVIOR OF SPHERICAL TANKS

    Pascal Pourcel - TECHNIP, Estelle Coussedière, Claire Gauthier, Nima Edjtemai - DYNALIS

    French regulation for seismic verification of structures is separated in two parts : * the "normal risk" for a structure which affects only it's surrounding when it collapses, * the "special risk" for a structure which could be dangerous for persons at long distances The first category includes all buildings. The calculation methods are in general static and the post elastic behavior is taken into account by a reduction factor. This factor allows to divide seismic stresses by a factor, function of the type of structure. For reinforced concrete and steel structures, values of this factor can be found in literature and codes (PS92 in France). The second category concerns the nuclear field and SEVESO's industrial sites (petrochemical industry for example). For the "special risk", the calculation method is a modal spectral analysis, which is an elastic calculation method too. The ability of a structure to have a ductile post elastic behavior is also taking into account by "reduction factors". The spectrum to be considered is regulatory where the seismic level is low (95% of French territory) and must be calculated elsewhere (taking into account site effects). If we consider industrial equipments, only a few values of this reduction factor exist, and they are not specified in codes. The engineer has to define and justify the values he chooses. To find a solution to this problem, the French Ministry of Environment decided in 1997 to make a comparison of French and US approach for this problem. This document gives values for some equipments but concludes anyway that some more calculations are necessary to be sure of these reduction factors. In 1999, The Ministry of Environment decided to undertake specific calculations for some equipments. This paper presents the first calculations performed for this project.

  • A semi-analytical model for polymers subjected to high strain rates

    A. Haufe - DYNAmore GmbH, P.A. Du Bois - Consulting Engineer, S. Kolling, M. Feucht - DaimlerChrysler AG

    Reliable prediction of the behaviour of structures made from polymers is a topic under considerable investigation in engineering practice. Especially, if the structure is subjected to dynamic loading, constitutive models considering the mechanical behaviour properly are still not available in commercial finite element codes. First, we give an overview of material laws for thermoplastics and show how the behaviour can be characterized and approximated by using visco-elasticity and metal plasticity, respectively. Experimental work is presented to point out important phenomena like necking, strain rate dependency, unloading behaviour and damage. A constitutive model including the experimental findings is derived. In particular, different yield surfaces in compression and tension and strain rate dependent failure, the latter with damage induced erosion, need to be taken into account. With the present formulation, standard verification tests can be simulated successfully. Also, an elastic damage model is used to approximate the unloading behaviour of thermoplastics adequately.

  • A SIMPLE CORRECTION TO THE FIRST ORDER SHEAR DEFORMATION SHELL FINITE ELEMENT FORMULATIONS

    Romil Tanov, Ala Tabiei - University of Cincinnati

    The present work concentrates on the development of correct representation of the transverse shear strains and stresses in Mindlin type displacement based shell finite elements. The formulation utilizes the robust standard first order shear deformation shell finite element for implementation of the proposed representation of the transverse shear stresses and strains. In this manner the need for the shear correction factor is eliminated. In addition, modification to any existing shell finite element for the correct representation of transverse shear quantities is minimal. Some modifications to correct Mindlin type elements are presented in the literature. These modifications correct the distribution of the transverse shear stresses only and use the constant transverse shear strains through the thickness. As compared to the above, the present formulation uses the correct distribution and is consistent for both transverse shear stresses as well as transverse shear strains.

  • A Simple Ejection Mitigation Device to Increase Survival of Standing Gunner

    M.S. Hamid (Advanced Computational Systems, LLC)

    It is a challenging task to provide warfighters protection due to impact related injuries such as skull fracture, lower leg and ankle fractures and neck and spinal injuries, which might occur during underbody blast. Tremendous improvements in design of ground vehicles have minimized these injuries. Further improvement can be achieved by new technology solutions by adding a simple passive device to existing design with minimal changes in order to mitigate occupant ejection for a vehicle occupant experiencing underbody blast while standing at nametag, defilade through round hatch opening as part of their operational duty. The patented device is an energy absorbing box with corrugated sheets in all four sides and welded to the top and bottom plates. The top and bottom plates are connected with brackets. The top plate and the brackets are connected with tension failure plates. The corrugated sheets act like energy absorbing (EA) bellows. The EA capacities can be increased by adding collapsible stiffeners inside the box. The device is virtually evaluated in an occupant standing position in a vehicle using LS-DYNA® and LS-PrePost®. The standing occupant is modeled using ATD from LSTC. Modeling of the Gunner Restraint System (GRS) used to keep the occupant in position is developed by using Seatbelt Fitting application module in LS-PrePost. An acceleration pulse is applied to the vehicle in order to represent the effect of blast load. The EA mechanism is evaluated for various side plate thicknesses and heights of the device. The reductions in tibia force and head excursion relative to hatch are presented.

  • A Simple Global/Local Approach to Modeling Ballistic Impact onto Woven Fabrics

    M. P. Rao, M. Keefe - University of Delaware, Newark, B. M. Powers, T. A. Bogetti - United States Army Research Laboratory, Aberdeen Proving Ground

    The objective of this study is to develop and demonstrate the feasibility of an LS-DYNA® Global/Local model for studying the non-linear mechanics of woven fabrics under ballistic impact. The presented approach is built on the observed response of fabrics in experimental studies performed at the Army Research Laboratory (ARL). In particular, two-layer test patches of 600 denier Kevlar KM2® fabrics are modeled with the aim of corroborating experimentally determined V50 velocities and physical deformation patterns. However, the present study begins with a brief overview of detailed three-dimensional (3D) finite element models of the woven fabrics under ballistic impact, comprised of regular undulating geometries of the individual yarn. This model is designated as the Full- Local environment and serves as the baseline for the subsequent Global/Local 3D finite element models. Within this Full-Local environment, the projectile velocity is determined as a function of time, and the response of the fabrics under the applied impact load are presented and discussed. Based on this work, the Global/Local modeling framework is developed that represents the fabric finite element meshes as comprised of combinations of homogenized continuum regions (‘Global’ regions) which neglect yarn undulations, and full 3D undulating yarns (‘Local’ regions). Discussions are presented regarding the implications on the predicted ballistic response of the fabrics. Specifically, comparisons are made for the predicted projectile velocity as a function of time, fabric deformations, energy histories, and computing time required to execute the individual simulations. It is shown that the Global/Local modeling approach results in reasonable savings in computing time without appreciably sacrificing the physics of the problem.

  • A Simple Material Model for Composite Based on Elements with Realistic Stiffness

    T. Tryland (Sintef Manufacturing)

    The obvious question is how to combine models and data to create a virtual prediction tool? There is a long history with measured data to adjust finite element models representing the geometry and material properties of a tested component. It seems to be a good starting point to represent the initial geometry with correct stiffness and challenge the element formulations to maintain realistic stiffness even when the elements are severely deformed. A proper discretisation is crucial when building a finite element model, and most metallic parts are represented as continuums although we know about the elementary particles. It is likely that this simplification is acceptable as long as the strains are small and the strain hardening is sufficient to compensate for local variation in material properties, but remember that brittle behaviour may be the result when the elastic energy stored in the component is allocated into the first local area that fails.

  • A Simple Weak-Field Coupling Benchmark Test of the Electromagnetic-Thermal-Structural Solution Capabilities of LS-DYNA Using Parallel Current Wires

    William Lawson, Anthony Johnson (General Atomics Electromagnetics)

    To begin learning the coupled field capability of LS-DYNA and validate results, a simple simulation of parallel wires carrying current was run. The magnitude of the current in the wires is such that the coupling between the electromagnetic (EM), thermal and structural fields is weak, in the sense that the coupling is taken to be one way. That is, there is no feedback amongst the three field solutions. This allows us to compare LS-DYNA code and known analytical results for code validation to build confidence that the code is being correctly used. LS-DYNA results are also compared to ANSYS results when no analytical results are valid. In addition, this simulation allowed us to test the transfer of EM generated Ohmic heating to the thermal field, and the transfer of EM generated forces to the structural field, a necessary process for coupling fields.   Furthermore, to be able to compare the code and analytical results, temperature-dependent material properties have not been included  a decent approximation with the low currents used.  The set-up of the coupled field model is discussed. Comparison of the LS-DYNA code and analytical results show good agreement where applicable. Comparison with ANSYS results is also good.

  • A Simple, Efficient and Robust Way to do Binder Wrap Simulation with LS-DYNA Implicit Solver

    Kaiping Li, Yang Hu - ASME, Chrysler Group LLC, Xinhai Zhu - Livermore Software Technology Corp.

    With the newly improved LS-DYNA implicit solver, the possibility to use it for binder wrap simulations of Stamping Process becomes reality. The importance of binder wrap simulation can never be overly emphasized since it will not only approve or disapprove the concepts of binder shape design, hence the whole addendum development of stamping process, but also impact the final results of stamping process simulations.

  • A Simplified Approach for Strain-Rate Dependent Hyperelastic Materials with Damage

    D.J. Benson - University of California, S. Kolling- DaimlerChrysler AG, P.A. Du Bois - Consulting Engineer

    Simulation of rubber-like materials is usually based on hyperelasticity. If strain-rate dependency has to be considered viscous dampers are added to the rheological model. A disadvantage of such a description is time- consuming parameter identification associated with the damping constants. In this paper, a tabulated formulation is presented which allows fast generation of input data based on uniaxial static and dynamic tensile tests at different strain rates. Unloading, i.e. forming of a hysteresis, can also be modeled easily based on a damage formulation. We show the theoretical background and algorithmic setup of our model which has been implemented in the explicit solver LS-DYNA [1]-[3]. Apart from purely numerical examples, the validation of a soft and a hard rubber under loading and subsequent unloading at different strain rates is shown.

  • A simplified approach to the simulation of rubber-like materials under dynamic loading

    Paul A. Du Bois - consulting engineer

    The simulation of rubber materials is becoming increasingly important in automotive crashworthiness simulations. Although highly sophisticated material laws are available in LS-DYNA to model rubber parts, the determination of material properties can be non-trivial and time consuming. In many applications, the rubber component is mainly loaded uniaxially at rather high strain rates. In this paper a simplified material model for rubber is presented allowing for a fast generation of input data based on uniaxial static and dynamic test data.

  • A Simulation-Driven System Design Methodology with Manufacturing Constraints

    Kaushik Sinha - DaimlerChrysler Research and Technology

    This paper presents a holistic simulation-driven system design methodology considering multiple performance objectives, performance constraints including formability criterion defined herein, using a genetic algorithm based multi-objective optimization software GDOT, developed in-house. This tool treats multiple objective functions separately without combining them in any form. A decision-making criterion is subsequently invoked to select the “best” subset of solutions from the obtained non-dominated Pareto optimal solutions under multiple performance constraints along with a formability index. Geometric properties, associated material properties (yield strength / plastic strain to failure) are considered as design variables. An example involving the frontal impact on a rail section is used to demonstrate the methodology. This process can further suggest requirements for synthesizing new materials that will result in optimal product performance. The objective of this study is to establish an ‘optimized’ set of design parameters with the dual aim of (i) minimizing the structural weight and (ii) maximizing energy absorption efficiency of the front rail system during frontal impact. The performance constraints being maximum transmitted force, maximum intrusion, pulse efficiency and formability criterion. This study also looks at the effect of parameter uncertainty on the optimal design. This study is composed in two stages. The first stage attempts to solve the multi-objective optimization problem, which is attempted using proprietary GDOT optimization code. Stage two performs reliability-based multi-objective optimization to generate a ‘reliable’ pareto optimal front. A 2nd order meta model is developed using responses, including formability index, computed from physics-based finite element models using LS-DYNATM analysis code. Looking at a broader picture, this methodology can potentially fill the gap between numerically optimized system development and simulation-driven digital product development. This, in turn, will help realize numerical simulation-driven product development process by aiming to achieve designs that are “first time right”.

  • A Smoothed-Particle Hydrodynamics (SPH) Model for Machining of 1100 Aluminum

    S. S. Akarca, W. J. Altenhof, A.T. Alpas - University of Windsor

    The smoothed-particle hydrodynamics (SPH) technique was used to model experimentally observed large deformation behaviour of aluminum (1100 Al) during machining. The effectiveness of the SPH method in predicting the response of the 1100 Al workpiece during orthogonal machining has been assessed through a careful comparison with the experimentally measured stress/strain distribution within the chips formed during steady state cutting. An Eulerian numerical model, previously validated for machining of copper, was also used to evaluate the SPH model. Both the Eulerian and SPH models showed good overall correlation with the experimentally measured stress/strain distribution when an exponential stress-strain behaviour was utilized in modeling. The maximum predicted plastic strains utilizing an Eulerian and SPH solution approach were 7.5 and 8.0, respectively. When the CPU time requirements were considered, the SPH model was the suitable choice to model deformation processes during cutting with relatively good accuracy and approximately 2.75 times less cost compared to the Eulerian model.

  • A Standardized Mechanism to Validate Crash Models for Ductile Plastics

    Megan Lobdell, Brian Croop, Hubert Lobo (DatapointLabs)

    Quantifying simulation accuracy before running crash simulations could be a helpful confidence building measure. This study continues our development of a mechanism to validate material models for plastics used in modeling high-speed impact. Focusing on models for isotropic materials that include options for rate dependency and failure, we explore other models commonly used for ductile plastics including MAT089 and MAT187.

  • A Status Review of Failure Simulation at the Federal Aviation Administration

    D. Cordasco, W. Emmerling (Federal Aviation Administration); P. DuBois (George Mason University)

    The Federal Aviation Administration (FAA) is developing models and methods for simulating fan blade off impact for engine containment. Accurately predicting deformation and failure in such an event is essential for advancing the industry and FAA goal of certification by analysis. Furthermore, industry and government engineers require publicly available tools to standardize the analysis during the engine design, development and certification phase. In addition to the high strain rates and steep temperature gradients typically realized in the impact event, a complex three-dimensional state of stress develops which is dependent on the impactor and target material properties, geometry, relative orientation and impact velocity. The resulting failure surfaces which characterize the plastic failure strain by the state of stress fully defined by the triaxiality and Lode parameter are highly nonlinear. Often, crucial stress state data points are not easily realized by typical specimen level standard tests necessitating the development of new experiments to fully characterize the surface for a given material.

  • A Strategy to Design Bird-proof Spinners

    Prof. Marco Anghileri, Dr. Luigi-Maria L. Castelletti, Ing. Dario Molinelli, Ing. Federico Motta - Politecnico di Milano

    Birdstrike is a serious threat for flight safety which causes every year remarkable losses. Even if modern aircrafts are certified for a level of bird impact resistance, it may happen that structures designed to carry aerodynamic loads, like a propeller spinner, may collapse after a bird strike. In general, the collapse of the spinner is not a concern if the fly-home capability is not compromised. In this paper, a strategy to design bird-proof spinner is introduced and its effectiveness evaluated by means of LS-Dyna. A SPH model of the bird was initially developed and validated. Then the impact of the bird onto a composite spinners was investigated. In particular, to capture its complex failure mechanism, the dynamic behaviour of the composite material used in the aircraft constructions was validated against specific dynamic tests. The influence of the spinner motion was also investigated and the differences between motionless and revolving spinners were pointed out. Improvements to the design of the reference spinner based on the idea of deflecting-the-bird instead of bagging-the-bird were developed and their performances numerically evaluated. In view of the results obtained, it was concluded that composite material and rotational motion can be exploited to design bird-proof spinner. Furthermore, it was observed that increasing the thickness of a spinner is not only against the weight constraints typical of aircraft constructions, but it is also ineffective.

  • A Strategy to Design Bird-proof Spinners

    Prof. Marco Anghileri, Dr. Luigi-Maria L. Castelletti, Ing. Dario Molinelli, Ing. Federico Motta - Politecnico di Milano

    Birdstrike is a serious threat for flight safety which causes every year remarkable losses. Even if modern aircrafts are certified for a level of bird impact resistance, it may happen that structures designed to carry aerodynamic loads, like a propeller spinner, may collapse after a bird strike. In general, the collapse of the spinner is not a concern if the fly-home capability is not compromised. In this paper, a strategy to design bird-proof spinner is introduced and its effectiveness evaluated by means of LS-Dyna. A SPH model of the bird was initially developed and validated. Then the impact of the bird onto a composite spinners was investigated. In particular, to capture its complex failure mechanism, the dynamic behaviour of the composite material used in the aircraft constructions was validated against specific dynamic tests. The influence of the spinner motion was also investigated and the differences between motionless and revolving spinners were pointed out. Improvements to the design of the reference spinner based on the idea of deflecting-the-bird instead of bagging-the-bird were developed and their performances numerically evaluated. In view of the results obtained, it was concluded that composite material and rotational motion can be exploited to design bird-proof spinner. Furthermore, it was observed that increasing the thickness of a spinner is not only against the weight constraints typical of aircraft constructions, but it is also ineffective.

  • A Study Concerning Precision of LS-DYNA Res

    Martin Feyereisen, Jeff Zais, Guangye Li - IBM

  • A Study in Mass Scaling for Sheet Metal Forming with LS-DYNA®

    Jeanne He Du Bois and Paul Du Bois, Forming Simulation Technology LLC

    Metal Forming simulation requires the deformed sheet metal to catch the tooling shapes precisely. With the limitation of lower order elements, mesh refinement is required to represent the key features of the geometry. In reality, the tooling travel speed is very low. Consequently, the physics of sheet metal forming involves a long termination time induced by the low Tool travel speed and a small timestep induced by the fine mesh. Many techniques are available to reduce the computation time for this important class of simulations. This presentation will study the effect of mass scaling, adaptive meshing and the related factor of tool travel speed and attempt to determine the acceptable range of settings for sheet metal forming simulation analysis. We will also identify what are the key criteria to identify the reliability of the simulation results.

  • A Study of LS-DYNA Implicit Performance in MPP

    Dr. C. Cleve Ashcraft, Roger G. Grimes, and Dr. Robert F. Lucas - Livermore Software Technology Corporation

    LS-DYNA models for Implicit Mechanics are getting larger and more complex. We are continually seeing models where the linear algebra problems in Implicit Mechanics have 10M rows and know of at least one that is nearly 40M rows. We expect users wanting to routinely solve problems with 30M very soon. It is these very large linear algebra problems that distinguish the computer requirements for Implicit Mechanics. This paper will present a study of the performance of the MPP implementation of implicit mechanics in LS-DYNA examining such issues as performance, speed-up, and requirements for computer configuration.

  • A Study of LS-DYNA Implicit Performance in MPP

    Dr. C. Cleve Ashcraft, Roger G. Grimes, and Dr. Robert F. Lucas - Livermore Software Technology Corporation

    LS-DYNA models for Implicit Mechanics are getting larger and more complex. We are continually seeing models where the linear algebra problems in Implicit Mechanics have 10M rows and know of at least one that is nearly 40M rows. We expect users wanting to routinely solve problems with 30M very soon. It is these very large linear algebra problems that distinguish the computer requirements for Implicit Mechanics. This paper will present a study of the performance of the MPP implementation of implicit mechanics in LS-DYNA examining such issues as performance, speed-up, and requirements for computer configuration.

  • A Study of LS-DYNA® Implicit Running the Rolls-Royce® Large Representative Engine Model with Intel® Optane™ DC Persistent Memory Technology

    Nick Meng (Intel Corporation), Roger Grimes, Robert Lucas, Francois-Henry Rouet (Livermore Software Technology (LST), an ANSYS company), James Ong (Rolls-Royce Holdings Corp.)

    In this paper we discuss Intel’s continued efforts to optimize the performance of LS-DYNA Implicit. We focus on the Rolls-Royce® Large Representative Engine Model (LREM), the largest implicit model known to Livermore Software Technology. Performance analysis indicated three opportunities for improvement: shared memory parallelization of the LS-GPart reordering code, optimization of the multifrontal linear solver, and usage of Intel® Optane™ DC Persistent Memory. We present results taken while running the LREM model with a tuned hybrid version of LS-DYNA R12.r144413 HYBRID_DP on 2nd Generation Intel® Xeon™ Platinum 8260L scalable processor (formerly Cascade Lake) cluster with Intel’s Optane persistent Memory. We depict the benefits of Intel Optane persistent Memory technology and discuss the techniques needed to optimize LS-DYNA.

  • A Study of Mapping Technique for Air Blast Modeling

    Vincent LAPOUJADE, Nicolas VAN DORSSELAER - Alliance Services Plus, Sandrine KEVORKIAN, Karine CHEVAL - Institut de Radioprotection et de Sûreté Nucléaire

    Since LS-DYNA® v971 r4, a new 2D ALE method with an associated Mapping technique is available. Mapping enables the decomposition of a calculation in several steps: at the end of a 2D ALE calculation, data from the last cycle can be mapped into another 2D or 3D mesh. Several finite element studies of Air Blast were modeled to evaluate efficiency and potential of this new LS-DYNA feature. First, an influence study was performed to evaluate the impact of the mesh characteristic length variation during the Mapping on shock wave both on pressure peaks and impulses. The analysis is focused on the evaluation of the loss due to the Mapping technique. Then, a comparison with experimental data on a simple 2D study of air blast using Mapping technique was performed. The very good precision obtained with the 2D ALE method and its ability to represent air blast phenomena will be shown.

  • A Study of Material and Architectural Effects on the Impact Response of 2D and 3D Dry Textile Composites using LS-DYNA

    Gaurav Nilakantan, Michael Keefe, John W. Gillespie Jr. - University of Delaware, Travis A. Bogetti, Rob Adkinson - US Army Research Laboratory

    High strength 2D fabrics and 3D textile composites comprised of materials such as KevlarTM, VectranTM, ZylonTM, and S2-Glass® find applications in protective systems such as personnel armor, spall liners, and turbine fragment containment. Various parameters can significantly affect the response of these fabrics under high rate impact including yarn/tow geometry (cross section), yarn/tow material (modulus, strength), and architecture (undulations and span). However these are just a few of the many other parameters such as projectile characteristics, boundary conditions, number of layers and orientations, weaving degradations, and so forth. Many of these parameters are inter-related and unfortunately this makes a comprehensive study very complex. Therefore, a set of key parameters have been identified for an initial exploratory numerical investigation. These include, on the material front: yarn/tow axial modulus, strength, frictional coefficient; and on the architectural front: yarn/tow cross section shape, size, span, and angle of inclination of through-thickness stitching or Z-tows. This study provides interesting initial insight into the role of through thickness tows on the overall impact resistance and energy dissipation capabilities for which these high strength fabrics were designed for. 3D fabrics with varying Z-tow architectures are compared against each other as well as against 2D fabrics without through thickness stitching. A special in-house preprocessor DYNAFAB is used to automatically generate the entire textile composite mesh. The user inputs basic parameters describing the desired yarn/tow geometry, architecture, and mesh density. The output is a LS-DYNA keyword input-file ready to use in the simulation. The geometry and undulations in the FE model closely represents the actual micrographs of the textile composite leading to a realistic representation of the architecture.

  • A Study of Material and Architectural Effects on the Impact Response of 2D and 3D Dry Textile Composites using LS-DYNA

    Gaurav Nilakantan, Michael Keefe, John W. Gillespie Jr. - University of Delaware, Travis A. Bogetti, Rob Adkinson - US Army Research Laboratory

    High strength 2D fabrics and 3D textile composites comprised of materials such as KevlarTM, VectranTM, ZylonTM, and S2-Glass® find applications in protective systems such as personnel armor, spall liners, and turbine fragment containment. Various parameters can significantly affect the response of these fabrics under high rate impact including yarn/tow geometry (cross section), yarn/tow material (modulus, strength), and architecture (undulations and span). However these are just a few of the many other parameters such as projectile characteristics, boundary conditions, number of layers and orientations, weaving degradations, and so forth. Many of these parameters are inter-related and unfortunately this makes a comprehensive study very complex. Therefore, a set of key parameters have been identified for an initial exploratory numerical investigation. These include, on the material front: yarn/tow axial modulus, strength, frictional coefficient; and on the architectural front: yarn/tow cross section shape, size, span, and angle of inclination of through-thickness stitching or Z-tows. This study provides interesting initial insight into the role of through thickness tows on the overall impact resistance and energy dissipation capabilities for which these high strength fabrics were designed for. 3D fabrics with varying Z-tow architectures are compared against each other as well as against 2D fabrics without through thickness stitching. A special in-house preprocessor DYNAFAB is used to automatically generate the entire textile composite mesh. The user inputs basic parameters describing the desired yarn/tow geometry, architecture, and mesh density. The output is a LS-DYNA keyword input-file ready to use in the simulation. The geometry and undulations in the FE model closely represents the actual micrographs of the textile composite leading to a realistic representation of the architecture.

  • A Study of MPP LS-DYNA ® Performance on Hardware Configurations

    Yih-Yih Lin and Toshihiro Ishibashi (Hewlett Packard Enterprise)

    With vehicle crash simulation models of sizes up to 10M elements, this paper will investigate how LS-DYNA performance is affected by the four hardware components: processor, I/O, memory, and interconnect network. First, two aspects of processor will be studied: performance gain from Intel Turbo Boost and performance gain from the AVX2 over the SSE2 instruction set architecture. Second, performances of using a local storage, a shared NFS file system, and a shared LUSTRE file system will be measured. Third, three aspects of memory will be studied: DIMM’s frequency, cache coherence snooping modes, and balance-ness of memory configurations. And fourth, performances of two interconnect network switches will be compared: Mellanox IB-FDR and IB-EDR .

  • A Study of Pedestrian Kinematics and Injury Outcomes Caused by a Traffic Accident with Respect to Pedestrian Anthropometry, Vehicle Shape, and Pre-Impact Conditions

    Costin D. Untaroiu, Wansoo Pak, Yunzhu Meng, Virginia Tech, Blacksburg, VA, USA;, Berkan Guleyupoglu, Scott Gayzik, Wake Forest University, Winston-Salem, NC, USA

    Pedestrians represent one of the most vulnerable road users. In the U.S., pedestrian fatalities show an increasing trend from 11% of total traffic fatalities in 2007 to about 15% in 2015. The rapid advancement in finite element (FE) technology, material testing, and computational power promotes FE car-to-pedestrian collision (CPC) simulations as a very useful component in the vehicle design process (e.g., in designing deployable devices for pedestrian head protection). The objective of this study was to investigate the sensitivity of pedestrian kinematics and injury outcomes to pedestrian anthropometry, vehicle shape, and pre-impact conditions (e.g. vehicle speed, relative position of pedestrian to the vehicle).

  • A Study of Quasi-static Problem by SPH Method

    Tatsuo Sakakibara, Toru Tsuda, Ryo Ohtagaki - ITOCHU Techno-Solutions Corporation

    The SPH method is well known for the hydrodynamics and recently SPH is applied for the impact and the penetration behavior into solid materials. SPH is completely mesh free so that it seems to be appropriate to simulate crash behaviors of concrete and rock materials. However, the applicability and the effects of the parameter of SPH for quasi-static problems are not clear completely. In this paper, in order to verify the applicability and the accuracy of SPH on quasi-static problems, a number of unconfined uni-axial compression simulations are performed by SPH. The specimens of different number of elements are used and the parameter sensitivities of SPH are examined. The influences of formulation type of SPH in LS-DYNA® are also investigated. The results of SPH are compared with the Laglangian result. From the results, the effects of the parameter for SPH are made clear. Besides, it is found that the renormalized formulation is efficient to get the accurate results at boundary. As the result, it is conformed that SPH is applicable for the quasi-static problems.

  • A Study of RC Beam-Column Against Close-in Blast Loading Using 3D ALE Mapping to S-ALE Technique

    Zoey Lim Siew Fern, Sun Jian Yun, Heng Zi Jing, Ang Choon Keat

    Mapping technique has been developed to allow the decomposition of a calculation in several steps. The transitions are allowed 1D to 2D/3D, 2D to 2D/3D, or 3D to 3D/2D etc [1], that the data from the model’s latest cycle is saved in a binary file and can be mapped into another model using the “map” command in the expression. This technique has a wide range of application since it allows to adjust mesh length or model size, as well as include Lagrangian or Eulerian Parts.

  • A Study on a Multi-Disciplinary Optimization Method for the PMP

    Soon-Young Seo, Jae-Woo Jeong, Dong-Hyeob Cho, Hyuk Kim - Samsung Electronics Co. Ltd.

    In the mobile electronic appliances market, the feature of products is getting smaller, thinner and more multi- functional. Therefore, mobile products are easily damaged from drop/impact and thermal cycling load. To make them more reliable under these conditions, the junction area between chips and PCB should be designed to bear up under drop/impact. And the heat caused by main chip (Memory & DMB channel chip) should be dissipated as quickly as possible. From the viewpoint of CAE simulation, although those two problems (drop & heat) should be considered simultaneously, they should not. Because the outline of PCB mainly depends on the location of main chip, positioning the main chip is one of the most important steps in the initial design stage. And the dynamic stress from free drop and heat caused by main chip are the one of the most critical factors to position the main chip. This paper presents the design process for positioning the main chip on PCB of PMP using MDO method. That is, the trade-off design variables between drop and thermal loading analysis were identified and system level optimization is performed in parallel. The main theme of this paper is to provide a way to get MDO solution of the PMP model in the early design stage.

  • A study on blast-loaded aluminium plates with crack-like defects subjected to blast loading

    H. Granum (Enodo), D. Morin, T. Børvik, O. Sture Hopperstad (NTNU)

    This paper presents a study on AA6016 plates in temper T4 subjected to blast loading. Four different crack-like defects have been introduced in the plates to facilitate crack propagation as the dominating failure mode. Uniaxial tensile specimens extracted from a plate are used in the calibration of the *MAT_258 material model available in LS-DYNA. This material model contains a non-quadratic yield surface, isotropic work hardening and a failure model where the onset of failure is dependent on the element size as well as its bending-to-membrane loading ratio. Four different element sizes are investigated to assess the ability of the model to predict the onset of failure and subsequent crack propagation in blast-loaded plates by comparison to experiments conducted in a shock tube facility.

  • A Study on Delamination Behavior between Aluminum and CFRTP

    Masahiro Okamura, JSOL Corporation;, Shin Horiuchi, The National Institute of Advanced Industrial Science and Technology

    In the near future, it is predicted that automobiles will use extensive amount of light weight material such as aluminum and CFRP. However, joining these material needs structural adhesive on the purpose of isolation and avoiding local stress concentration. In this paper, a simulation model has been built up using LS-DYNA® for DCB (double cantilever beam) test. Combination of various thicknesses in aluminum and CFRTP specimen has been studied to assess structural toughness. Validity of the simulation model has been confirmed by comparing the results with experiments, and trends and detailed mechanisms are discussed.

  • A Study on Preparation of Failure Parameters for Ductile Polymers

    Kunio Takekoshi, Kazukuni Niwa (TERRABYTE Co., Ltd)

    A study on preparation method of failure parameters for ductile polymers is presented using experimental results of high-speed tensile test for Polycarbonate and simulation results based on Semi-Analytical Model for Polymers (SAMP) constitutive model [1] in LS-DYNA®. In addition, a comparative review of two widely used failure models, namely, total formulation and incremental formulation [2, 3], is carried out using Charpy impact test simulations where the failure parameters are prepared using the proposed method. It is found that the incremental formulation is excellent in predicting the experimentally observed behavior of notched Charpy impact test and non-notched Charpy impact test.

  • A Study on Scatter during Production Process using Statistical Approach using LS-OPT®

    Masahiro OKAMURA, JSOL Corporation

    In recent years, robustness of car body structure has become more important than ever, as car manufacturers are required to achieve conflicting performance in high level such as light weight and crash performance. Major source of scatter in body structures are material scatter and production scatter. Since it is difficult to reduce scatter in material as certain range of scatter is allowed by industrial standard, tightening the quality control is not realistic. Only viable solution is to improve production process such as stamping and joining to address the issue. A common way to assess robustness of the structure is to build response surfaces and study sensitivity of input scatter to output, and there are many papers available on the issues.

  • A Study on Shock Wave Propagation Process in the Smooth Blasting Technique

    Masahiko Otsuka, Yamato Matsui, Shigeru Itoh - Kumamoto University, Kenji Murata, Yukio Kato - NOF Corporation. Aichi Branch, Taketoyo

    Explosives can easily generate high energy and ultra-high pressure. In recent years, research on the advanced technological use of explosives is studied in various places. Here we focus on the Smooth Blasting Technique that is applied for tunnel blasting. This technique is performed to fracture concrete and to reduce the quantity of fragments, while avoiding stress concentration of ground pressure during tunnel blasting. When this technique is used, it is important to know what influence it will have. In our calculation code, the analysis of compressible substances, which cells transform greatly like air, was very difficult. In this study, we use LS-DYNA, an analysis code using a finite-element method. By analyzing the stress state of the air hole circumference, multilayer models such as air, Vinyl Chloride and water are analyzed and it aims to get the propagation process of the shock wave. The Arbitrary Lagrangian Eulerian (ALE) method is based on the arbitrary movement of a reference domain, which additionally to the common material domain and spatial domain, is introduced as a third domain. Three equations of state (EOS) are used in this study. The JWL equation of state is applied for the reaction of the explosive, and has form of a perfect gas equation of state. When the density becomes large, exponential terms modify the perfect gas equation of state. The Mie-Gruneisen equation of state is applied for water and poly vinyl chloride, and the linear polynomial equation of state is applied for air.

  • A study on the bolt modeling with pre-load for field application

    Han Deok Hee, Kim Dong Hyeon, Kim Young Joon

    When fastening a structure with a bolt, an axial force is generated by the tightening torque of them. This axial force acts as a friction force by the friction coefficient of the fastening part, and becomes a factor that directly affects the deformation of the fastening part. For this reason, there have been many studies on how to make the bolt models for applying preload and users are using various methods. What is common is the construction and evaluation of bolt models with preload requires a lot of working by user. So this study was conducted because it was necessary to easy and exact method for with preload bolt models.

  • A Study on the Scalability of Hybrid LS-DYNA on Multicore Architectures

    Yih-Yih Lin - Hewlett-Packard Company

    In this paper, the effects of differences in problem size, number of cores per processor, and interconnect on the Hybrid LS-DYNA’s performance are studied. The result shows that combination of these three factors determines when Hybrid LS-DYNA has a performance advantage over the MPP LS-DYNA.

  • A Study on the Transfer of GISSMO Material Card Parameters from 2D- to 3D-Discretization

    Daniel Sommer, Peter Middendorf (University of Stuttgart), Florian Schauwecker (University of Stuttgart / Daimler AG)

    This study presents basic strategies for transfer of LS-DYNA® material card parameters from 2D- to 3D-discretizaion without extensive recalibration. The responses of a material card, calibrated on two-dimensional shell elements, are shown on single-element tests with different element formulations, on multi-element patches and on coupons. From this, magnitudes of error are ascertained and quick recalibration measures on material model parameters are derived. An evaluation of the stress-state of typical GISSMO-type specimen in different thicknesses and discretization-lengths is given and typical stress-states within the Lode-triaxiality stress-space of these specimens are highlighted. Therefrom, a measure of deviation from the calibrated state can be derived and used as a measure for allowable deviation from the 2D stress-state. Furthermore, the information on the three-dimensional stress-states, even in thin specimen, can be used for quick recalibration of parameters on the failure surface.

  • A Study on Yielding Function of Aluminum Honeycomb

    Shigeki Kojima - TOYOTA COMMUNICATION SYSTEMS CO., LTD. , Japan, Tsuyoshi Yasuki, Satoshi Mikutsu - Toyota Motor Corporation, Japan, Toshikazu Takatsudo - THE YOKOHAMA RUBBER CO., LTD. , Japan

    This paper describes newly developed yielding function of aluminum honeycomb. Physical compression tests of aluminum honeycomb were performed and it was found that yielding stress of aluminum honeycomb highly depended up on direction of compression. Using these test data, a yielding function was newly derived as a function of volumetric change and angle of compression. The yielding function was introduced to MAT126 as an option. ODB frontal collision analysis result with the yielding function showed much better correlation with test results than with MAT126 without the option.

  • A Summary of the Space Shuttle Columbia Tragedy and the Use of LS-DYNA in the Accident Investigation and Return to Flight Efforts

    Matthew Melis, Kelly Carney - NASA Glenn Research Center, Jonathan Gabrys - Boeing, Edwin L. Fasanella - US Army Research Laboratory/VTD, Karen H. Lyle - NASA Langley Research Center

    On February 1, 2003, the Space Shuttle Columbia broke apart during reentry resulting in loss of 7 crewmembers and craft. For the next several months an extensive investigation of the accident ensued involving a nationwide team of experts from NASA, industry, and academia, spanning dozens of technical disciplines. The Columbia Accident Investigation Board (CAIB), a group of experts assembled to conduct an investigation independent of NASA concluded in August, 2003 that the cause of the loss of Columbia and its crew was a breach in the left wing leading edge Reinforced Carbon-Carbon (RCC) thermal protection system initiated by the impact of thermal insulating foam that had separated from the orbiters external fuel tank 81 seconds into the missions launch. During reentry, this breach allowed superheated air to penetrate behind the leading edge and erode the aluminum structure of the left wing which ultimately led to the breakup of the orbiter. In order to gain a better understanding of the foam impact on the orbiters RCC wing leading edge, a multi-center team of NASA and Boeing impact experts was formed to characterize the foam and RCC materials for impact analysis using LS-DYNA. LS-DYNA predictions were validated with sub-component and full scale tests. LS- DYNA proved to be a valuable asset in supporting both the Columbia Accident Investigation and NASA’s return to flight efforts. This paper summarizes the Columbia Accident and the nearly seven month long investigation that followed. The use of LS-DYNA in this effort is highlighted. Contributions to the investigation and return to flight efforts of the multi-center team consisting of members from NASA Glenn, NASA Langley, and Boeing Philadelphia are covered in detail in papers to follow in these proceedings.

  • A Survey of Eigen Solution Methods in LS-DYNA®

    Roger Grimes, Liping Li, Eugene Vecharynski, Livermore Software Technology Corporation

    LSTC has been adding several new methods for solving a variety of eigenvalue problems in LS-DYNA. This talk will give a survey of two new methods including MCMS (our implementation of the AMLS algorithm), and an iterative based method based on the Locally Optimal Block Pre-Conditioned Conjugate Gradients Method (LOBPCG). These methods will be contrasted with our standard method of Block Shift and Invert Lanczos. We will also describe our implementation of Sectoral Symmetry, a method to vastly reduce the problem size for models with a high degree of rotational symmetry such as fan blades.

  • A Systematic Approach to Model Metals, Compact Polymers and Structural Foams in Crash Simulations with a Modular User Material

    G. Oberhofer, H. Gese - MATFEM Partnerschaft Dr. Gese & Oberhofer, A. Bach, M. Franzen, H. Lanzerath - Ford Research & Advanced Engineering Europe

    Today the automotive industry is faced with the demand to build light fuel-efficient vehicles while optimizing its crashworthiness and stiffness. A wide variety of new metallic and polymeric materials have been introduced to account for these increased requirements. Numerical analysis can significantly support this process if the analysis is really predictive. Within the numerical model a correct characterization of the material behaviour – including elasto-viscoplastic behaviour and failure - is substantial. The particular behaviour of each material group must be covered by the material model. The user material model MF GenYld+CrachFEM allows for a modular combination of phenomenological models (yield locus, strain hardening, damage evolution, criteria for fracture initiation) to give an adequate representation of technical materials. This material model can be linked to LS-DYNA when using the explicit-dynamic time integration scheme. This paper gives an overview on the material characterization of ultra high strength steels (with focus on failure prediction), non-reinforced polymers (with focus on anisotropic hardening of polymers), and structural foams (with focus on compressibility and stress dependent damage evolution) with respect to crash simulation. It will be shown that a comprehensive material model - including damage and failure behaviour - enables a predictive simulation without iterative calibration of material parameters. A testing programme has been done for each material group in order to allow a fitting of the parameters of the material model first. In a second step different component tests have been carried out, which were part of a systematic procedure to validate the appropriate predictions of the crash behaviour with LS-Dyna and user material MF_GenYld+CrachFEM for each material group.

  • A Systematic Approach to Model Metals, Compact Polymers and Structural Foams in Crash Simulations with a Modular User Material

    G. Oberhofer, H. Gese - MATFEM Partnerschaft Dr. Gese & Oberhofer, A. Bach, M. Franzen, H. Lanzerath - Ford Research & Advanced Engineering Europe

    Today the automotive industry is faced with the demand to build light fuel-efficient vehicles while optimizing its crashworthiness and stiffness. A wide variety of new metallic and polymeric materials have been introduced to account for these increased requirements. Numerical analysis can significantly support this process if the analysis is really predictive. Within the numerical model a correct characterization of the material behaviour – including elasto-viscoplastic behaviour and failure - is substantial. The particular behaviour of each material group must be covered by the material model. The user material model MF GenYld+CrachFEM allows for a modular combination of phenomenological models (yield locus, strain hardening, damage evolution, criteria for fracture initiation) to give an adequate representation of technical materials. This material model can be linked to LS-DYNA when using the explicit-dynamic time integration scheme. This paper gives an overview on the material characterization of ultra high strength steels (with focus on failure prediction), non-reinforced polymers (with focus on anisotropic hardening of polymers), and structural foams (with focus on compressibility and stress dependent damage evolution) with respect to crash simulation. It will be shown that a comprehensive material model - including damage and failure behaviour - enables a predictive simulation without iterative calibration of material parameters. A testing programme has been done for each material group in order to allow a fitting of the parameters of the material model first. In a second step different component tests have been carried out, which were part of a systematic procedure to validate the appropriate predictions of the crash behaviour with LS-Dyna and user material MF_GenYld+CrachFEM for each material group.

  • A Systematic Approach Towards Integrated Safety Modelling for Aerospace Applications – Preliminary Results on Rigid Seat Simulations

    Nina Wegener, Christoph Sauer, Paul Schatrow, Matthias Waimer

    In the aviation sector, the historically evolved crashworthiness requirements prescribe seat certification separately from the airframe structure. Based on historical test and accident data the airframe crash behaviour is presumed in terms of crash pulses, which are applied to the seat structure for seat certification (e.g. EASA CS-23/25.562). Certification authorities have recently started to change the regulations from a prescriptive to a performance-based certification, considering the crash performance with the seats integrated in the airframe structure (EASA CS-23 Amendment 5). With this, occupant safety and structural crashworthiness is combined to an integrated safety approach. Due to the high cost of full-scale testing in the aviation sector, extensive use of simulation is of interest. Modelling methods are continuously being developed for crash loading conditions relevant to aerospace, which significantly differ from automotive ones. The German Aerospace Center (DLR) Institute of Structures and Design has extensive experience in developing simulation methods for aircraft crash analysis. In an effort to develop an integrated safety modelling approach for aviation, a research initiative was launched to incorporate advanced passenger safety considerations.

  • A Systematic Study on Topology Optimization of Crash Loaded Structures using LS-TaSC

    K. Weider, A. Marschner, A. Schumacher (Bergische Universität Wuppertal)

    In this contribution the chances and limitations of using LS-TaSC for topology optimization of crash loaded structures will be shown. With two demonstrative examples the influence of scaled loads, intermediate densities and conflicting constraints are discussed. As no analytical sensitivities are available in explicit finite element simulations, LS-TaSC uses the interal energy density as sensitivity, which makes it an efficient optimization strategy for stiffness applications. For the provided examples, both a maximum stiffness as well as a crashworthiness design is developed. In the latter case, the multipoint method of LS-TaSC is used to cope with the acceleration of an impactor as objective function. To compare the resulting topology with other topology optimization methods, a thickness optimization of a shell interpretation is performed. The structural behavior is also compared with that of the optimized solid model.

  • A Temperature and Strain Rate Dependent Material Model with Tension-Compression Asymmetry for 0.25 inch Ti-6Al-4V Plate

    Leyu Wang, Paul DuBois, Kelly Carney, Cing-Dao Kan, Center of Collision Safety and Analysis, George Mason University, USA

    Tension-compression asymmetry observed in a 0.25" thick Titanium plate is modeled with *MAT_224_GYS, an isotropic elastic-thermo-viscous-plastic material model in LS-DYNA®. The input deck fits a series of tensile and compression tests at different strain rates and temperatures, conducted on samples cut from a 0.25" commercial off-the-shelf titanium plate. The rate and temperature dependent hardening law is separately defined for the tension and compression response. It is seen that *MAT_224_GYS is capable of capturing the tension-compression asymmetry of Titanium Ti-6Al-4V.

  • A three-dimensional finite element model for the roll bending of heavy plates using a 4-roll plate bending machine

    L. Kappis, P. Froitzheim, Prof. W. Flügge (Fraunhofer IGP)

    Roll bending is a manufacturing process in which sheet metal is continuously formed into a round shape with the help of typically three or four rotating rolls. It is used in particular for the production of thick-walled pipes and shells with large volumes, which are used in the maritime sector, in pipeline construction and in the field of renewable energies. In these areas, at the current state of the art, the process is mainly controlled manually. However, the control of the process is of great importance for its efficiency. For example, over-controlling the machine leads to over-bending of the plate and thus often to material waste, whereas under-bending requires additional rolling passes and leads to an increase in production time. To reduce the human influence on the economic efficiency of the process and to objectify the process, research is currently being carried out on the development of automation solutions for roll bending.

  • A Toolbox for Validation of Nonlinear Finite Element Models

    Dr. Mark C. Anderson, Timothy K. Hasselman - ACTA Inc., John E. Crawford - Karagozian & Case Structural Engineers

    With increasingly powerful computational resources at our disposal, it is becoming common- place to use analytical predictions in lieu of experimentation for characterization of physical systems and events. This trend, with its perceived potential for reducing costs, is the basis for the simulation-based procurement initiatives currently gaining momentum within the Gov- ernment and industry. However, a simulation-based approach is often sold to decision-makers via plausible visualizations of model simulation results; the simulations themselves having only been validated in an ad hoc manner using anecdotal comparisons with real events. Ex- perience has shown that, while simulation using physics-based models may lead to qualita- tively correct results, there can be large quantitative discrepancies between simulation and experimental results for a given physical event, and between simulation results from different analysts for the same event. Obviously, for simulation-based procurement to be a viable alter- native to more traditional test-based procurement, the quantitative accuracy of the simulations must be insured. To do this requires at least a modicum of experimental data (perhaps at the component or subsystem level) to serve as a yardstick with which the accuracy of simulation results can be measured. And it requires minimizing the differences between corresponding analytical and experimental results in physically meaningful ways, as well as characterizing the ability of the models to predict future events. This paper describes a toolbox for the vali- dation of nonlinear finite element models. The toolbox includes tools for quantitatively up- dating model parameters based on the differences between test results and analytical predic- tions, as well as estimating the predictive accuracy of the model based on generically similar comparisons. Use of the toolbox is illustrated for a DYNA model of a reinforced concrete wall subjected to blast loading.

  • A Topology Optimization Tool for LS-DYNA Users: LS-OPT/Topology

    Tushar Goel, Willem Roux, Nielen Stander - Livermore Software Technology Corporation

    Topology optimization is a very powerful tool to develop new concepts and has been widely used in engineering problems involving static loading conditions. However, there has been relatively little work for topology optimization of industrial size non-linear dynamic systems. The main issues are non-linear interactions among the material properties, contacts between parts, large strain-rates, transient behavior, etc. A hybrid cellular automata based method, combining cellular automata theory with the fully loaded design concept, has been demonstrated to be effective in generating new concept designs. This method is called hybrid cellular automata (HCA) and is used as the core algorithm to optimize the topology. This method is implemented in the LS-DYNA framework and would be available shortly. The method has shown encouraging results while solving many engineering problems. In this paper, the details of the methodology and a few engineering examples are provided to demonstrate some capabilities of the code. The main problem solved using the proposed methodology is the development of an optimal topology for a 1 million element box-shaped design domain subject to impact.

  • A Topology Optimization Tool for LS-DYNA Users: LS-OPT/Topology

    Tushar Goel, Willem Roux, Nielen Stander - Livermore Software Technology Corporation

    Topology optimization is a very powerful tool to develop new concepts and has been widely used in engineering problems involving static loading conditions. However, there has been relatively little work for topology optimization of industrial size non-linear dynamic systems. The main issues are non-linear interactions among the material properties, contacts between parts, large strain-rates, transient behavior, etc. A hybrid cellular automata based method, combining cellular automata theory with the fully loaded design concept, has been demonstrated to be effective in generating new concept designs. This method is called hybrid cellular automata (HCA) and is used as the core algorithm to optimize the topology. This method is implemented in the LS-DYNA framework and would be available shortly. The method has shown encouraging results while solving many engineering problems. In this paper, the details of the methodology and a few engineering examples are provided to demonstrate some capabilities of the code. The main problem solved using the proposed methodology is the development of an optimal topology for a 1 million element box-shaped design domain subject to impact.

  • A Tutorial on How to Use Implicit LS-DYNA

    R. Grimes (LSTC)

    This talk will focus on the issues of using the Implicit features of LS-DYNA. Implicit has a profoundly different footprint regarding the computational resources required than an explicit simulation. This talk will especially focus on the management of those computational resources, especially for distributed memory computations. This talk will also include an overview of techniques for debugging models for use by Implicit.

  • A Unified Environment for Collaborative CAE and Immersive Simulation Results Processing

    Stavros Kleidarias, BETA CAE Systems S.A.

    Ever since the first CAE simulations there has always been a need to examine digital models as close to reality as possible. Technology limitations meant that this was done on digital models with unrealistic graphics representation and on a PC monitor. Also, the evaluation of simulation results by engineering teams on different design centers was proven to be inefficient and time consuming, being based on exchanging tediously prepared images, videos and reports.

  • A Unified Environment For Processing Test Videos And Simulation Models

    S. Kleidarias, V. Pavlidis (BETA CAE Systems)

    Throughout the development process of a complex structure such as a vehicle, simulation and testing are both present in almost all phases. Being able to use them efficiently and concurrently whenever this is needed, it maximizes the benefit to the user, as this provides valuable information to identify defects in either the simulation or the test and therefore, avoid errors and delays in the development chain. One common type of test result is the videos, very common in crash domain. Enabling the processing of a video, which is a demanding task on its own, within the same environment where the simulation models are being processed, allows for the direct and easy comparison/correlation of the two and the deduction of useful conclusions. This presentation showcases an LS-Dyna model and relevant real test videos both being processed in META, the post-processor of BETA CAE Systems. META forms a single unified environment for detailed model post-processing as well as for complete video processing. First of all the model view can be easily matched to that of the video either in one plane or in perspective view. Synchronisation of video frames and states of the model can be achieved in a simple way. Valuable information can be extracted from the video. Points as well as distances and angles can be tracked on the video and respective results can be readily plotted on the video as well as in a 2D plot. Tracking functionality for user defined points can also overcome cases where the tracked point is hidden for a number of frames and it also allows for manual tracking for certain frames so as to by-pass tracking discontinuity wherever automatic fix is not possible. Measurements on the video are facilitated by overlaying a grid as well as by defining user defined coordinate systems, either static ones or dynamic. The capability for eliminating rigid body motion from video frames, based on anchoring one or two tracked points on the video, can further assist the correlation of the video with a crash simulation model and thus lead to better conclusions.

  • A Unified SPH-DEM-FEM Approach for Modeling of Debris Flow Impacts on Protective Structures

    Chun Liu, Zhixiang Yu (Southwest Jiaotong University), Qiang Wang (Shanghai Fangkun Software Technology Ltd)

    Debris flows are rapid gravity-driven unsteady flows of highly concentrated mixtures of water and solid particle material, destroying numerous mountain building structures and traffic facilities. Investigation of debris flows is thus of significance to hazard prevention and mitigation. This paper aims to provide a numerical model capable of reproducing the debris flow impact estimation by accounting for complicated fluid-particle-structure interaction (FPSI) with a unified Smoothed Particles Hydrodynamics (SPH), Discrete Element Method (DEM) and Finite Element Method (FEM) approach. The fluid phase is represented by SPH. The solid phase consists of physical particle(s) is represented by DEM, and deformable solid structure is represented by FEM. The Wenjia gully debris flow is carried out to demonstrate the capability of the coupled model for simulating FPSI as the application of the debris flow impact simulations. Compared the actual situation, the propagation of the debris flow and destruction of structures were predicted. Then, the effectiveness of the treatment measures of the Wenjia gully debris flow was clarified from the impact evolution, impact force. The developed method will contribute to a better understanding of FPSI and is a promising tool for hazard analysis and mitigation.

  • A User-Defined Element Interface in LS-DYNA v971

    Thomas Borrvall - Engineering Research Nordic AB

    The user-defined features in LS-DYNA are powerful tools that allow users in academia or industry to verify research results in the context of general and complicated finite element applications. Implementation work concerns only the special field of interest, and there is no need for the comprehensive task of developing and maintaining the complete finite element software. One of the new user-defined features in LS-DYNA v971 is the possibility to define structural solid and shell elements. Up to a total of ten element formulations can be implemented in a single LS-DYNA executable both for explicit and implicit analyses. A high abstraction-level interface is in particular provided for numerically integrated elements, and stabilization schemes can easily be incorporated. There is also the option to implement discrete elements, and property parameters and history variables can be associated with the element. The interface is equipped with additional features that facilitates research on element technology, but also makes it perfectly suited for educational purposes. An overview of the procedure of implementing an element in the new interface as well as invoking it from the keyword input file will be presented.

  • A user-defined Folgar-Tucker-based fiber orientation material model for compression molding of fiber/polymer-compounds

    Dominic Schommer, Miro Duhovic, David May, Joachim Hausmann, Heiko Andrä, Konrad Steiner

    LS-DYNA® provides an ever-increasing portfolio of material models covering a wide range of material behavior for solving multi-physics problems. The software also provides users the opportunity to implement their own user-defined material models via FORTRAN code, to describe the behavior of very specific materials. In this work, a user-defined material model has been developed to describe the compression molding behavior of sheet molding compounds (SMCs). A SMC is a composite material based on a thermoset resin reinforced by chopped long fibers. During the compression molding of SMCs, very complex material behavior involving elastic compaction and plastic flow (depending on material composition) occurs, which is dependent on the local fiber orientation, temperature and strain rate. One way to describe the processing behavior of SMC materials as simply as possible is using a building block approach. Following the identification of the most relevant material effects, individual building blocks are created containing the respective mathematical solutions (e.g. compaction and plastic flow behavior).

  • A Validation Case Study: Steel Billet Drop Tests and Simulations as Reported in NUREG/CR-6608

    Leonard E. Schwer - Schwer Engineering & Consulting Services, James M. Kennedy - KBS2, Inc.

    Before performing safety assessments of spent fuel storage casks in drop and tipover accident simulations, method validation calculations are required. The validation process is outlined by the Nuclear Regulatory Commission (NRC) [Tang, et al., undated], and specifically requires the satisfactory replication of the steel billet drop tests, reported in NUREG/CR-6608 (UCRL-ID-129211) [Witte, et al., 1998]. In addition to reporting the test results in NUREG/CR-6608, Witte, et al. also provide simulations of the tests using the Lawrence Livermore National Laboratory explicit finite element code DYNA3D [Whirley, 1993]; several other organizations have used the Livermore Software and Technology Corporation code LS-DYNA [Hallquist, 1999]. Although other explicit finite element codes would also be applicable, the material model parameters provided for the concrete pad, upon which the billets are dropped, in NUREG/CR-6608 are specific for the Concrete/Geological Material, i.e. Material Type 16, in DYNA3D and LS-DYNA. This sole fact provides a great incentive for analysts to use DYNA3D or LS-DYNA. This manuscript briefly reviews the test configurations and results with recommendations on which configurations and results should be emphasized in comparisons with simulations. Next a brief review of the simulations presented in NUREG/CR-6608 with comments on the modeling and results and suggested improvements is provided. Then comments are provided on the utility of these results, both experimental and numerical, as a validation of the methodology with a particular emphasis on how they extrapolate to the cases of interest for spent fuel storage casks. Finally, a series of recommendations are included that should be considered, and discussed, by analysts providing simulations for spent fuel storage casks and the authorities requiring the safety assessment of these casks.

  • A Variable Finite Element Model of the Overall Human Masticatory System for Evaluation of Stress Distributions During Biting and Bruxism

    S. Martinez, J. Lenz, Prof. K. Schweizer­hof (Karlsruhe Institute of Technology), H. Schindler (University of Heidelberg)

    Simulating the masticatory system during chewing, clenching and bruxism, requires the model to capture the dynamical behavior of its different components: the mandibula and maxilla, the temporomandibular joint (TMJ) including the articular disc and the surrounding cartilage layers, the teeth, the periodontal ligaments (PDL), and the muscles

  • A VCCT-Cohesive Approach for the Efficient Modelling of Delamination in Composite Materials

    P. Daniel (Btechc), J. Främby (DYNAmore Nordic), M. Fagerström (Chalmers University), P. Maimí (University of Girona)

    The accurate modelling of delaminations is necessary to capture the correct behavior of composite structures subjected to demanding loads. While the use of cohesive elements is valid when the discretization is smaller than the failure process zone [1], for many composite materials it implies using a fine mesh, typically smaller than 1.0 mm, leading to excessive computational cost for large structures. On the contrary, the Virtual Crack Closure Technique (VCCT) allows the prediction of delamination growth in larger elements [2] but lacks of an energy dissipation mechanism. Therefore, it leads to excessive vibrations when the delamination propagates in dynamic analyses. The present work aims to combine the best of both methods in order to develop a viable solution for large structures, allowing for coarser meshes than what is possible to use today. To do so, the VCCT is used as a failure criterion to predict damage initiation while a cohesive-like model is added to dissipate the released energy. The model has been implemented in LS-DYNA in the frame of an adaptive user element recently published [3,4]. The model has been validated with Double Cantilever Beam, End-Notched Flexure and Mixed-Mode Bending tests. It demonstrates the ability of the method to accurately model delamination with larger elements and higher stable time step.

  • A View on the Technology of both Vehicle Content and the Product Creation Process for Supercars

    Neil Hannemann - McLaren Automotive

    All road cars have benefited from constantly improving technology; many of these improvements are not always obvious to the consumer. In the category of Supercars the improvements can be measured in ways that are exciting to an automotive enthusiast. The improvements most visibly noted are items that are part of the content of the car, such as electronic fuel injection, airbags, and items cars have always had, such as tires. These technological improvements can fall into 2 categories; Steady improvements and Breakthroughs. Examples in both categories will be discussed. Less obvious are the improvements in automotive design and development processes. The advent of computer technology, powerful and plentiful enough to make CAD and CAE integral parts of the design and development process, is the most important contributor to this ability. The simulation and analysis that is now possible has contributed to the ability to improve many attributes of a car through optimization, and has also allowed the timescales of the design and development process to be compressed. While not as visible as changing the content of the car, improving the design and development process has had just as profound an affect on opening up the performance envelope of Supercars.

  • A Virtual Golf Robot for Golf Equipment Simulation

    Tom Mase - Michigan State University

    The equations of motion for a two-lever pendulum are developed using Lagrange's equation. An assumed kinematic golf swing is used to generate generalized forces to drive the golf robot. These moments are used to generate a golf robot swing using LS-DYNA. The LS-DYNA model is flexible enough so that the model can be used as a virtual laboratory.

  • A Viscoelastic-Viscoplastic Time-Temperature Equivalence for Thermoplastics

    V. Dorléans, E. Michau (Faurecia Interior System), R. Delille, F. Lauro, D. Notta-Cuvier, B. Bourel, G. Haugou, H. Morvan (University Polytechnique Hauts de France)

    For automotive suppliers, it is essential to model the behavior of thermoplastics under crash loading and for a large range of temperature typically from -30° until 85°c. Thermoplastics are very sensitive to both strain rate and temperature with an inverse relation: hardening with strain rate and softening with temperature. Generally, a large experimental campaign has to be carried out to identify different behavior laws of the material, each of them for a specific range of strain rate and temperature. Then, according to the characteristics of the loading case, e.g. impact, corresponding behavior laws are chosen in the database to run the numerical simulations. This results in an important experimental cost and a large database to manage. It is then interesting to explore the time-temperature equivalence of thermoplastics to act on both aspects. Relations between strain rate and temperature sensitivities are identified through dynamic mechanical analysis (DMA) in the viscoelastic domain and described through the Williams, Landel and Ferry model or the Arrhenius model for example. For that, a shift factor is experimentally determined and introduced to modify the time step in the behavior model for the finite element simulation, thus simulating an adapted strain rate. As a novelty, the time-temperature equivalence is here extended to the viscoplastic domain by keeping the same shift factor. It therefore becomes possible to cover all the scope of temperature and strain rate of automotive applications from only DMA and tensile tests at room temperature and different strain rates. This approach is implemented in association with viscoelastic, viscoplastic with non-associative plasticity constitutive laws and non-local damage model [1][2][3] and applied to the case of a polypropylene. The time temperature equivalence is validated for the viscoelastic as well as for the viscoplastic parts of the behavior with good experimental/numerical correlation. As a result, the number of material cards required in Ls Dyna is reduced to only one to cover all the simulations. This approach is also under investigation to be applied to the failure model.

  • A Weight Balanced Multi-Objective Topology Optimization for Automotive Development

    N. Aulig, S. Menzel (Honda Research Institute Europe), E. Nutwell (Ohio State Uiversity), D. Detwiler (Honda R&D)

  • A Zero Thickness Cohesive Element Approach for Dynamic Crack Propagation using LS-DYNA®

    Ala Tabiei, Wenlong Zhang, Department of Mechanical and Materials Engineering, University of Cincinnati, Cincinnati, Ohio 45221, USA

    The zero thickness cohesive element approach for arbitrary crack propagation has a deficiency of introducing artificial compliance to the model, especially when cohesive elements are inserted into every element interfaces. For dynamic problems, the artificial compliance decreases the stress wave speed and makes the result less accurate. In this paper, the reason of the artificial compliance is examined, and the bilinear and exponential cohesive law are compared. The work shows that by choosing the right cohesive stiffness, element size and using bilinear cohesive law rather than exponential cohesive law, the artificial compliance issue can be limited to a negligible level without greatly increasing the computational time.

  • About Isogeometric Analysis and the new NURBS-based Finite Elements in LS-DYNA

    Stefan Hartmann , David Lorenz - DYNAmore GmbH, David J. Benson - University of California

    In the context of isogeometric analysis many research activities have focused on the use of Non- Uniform Rational B-Splines (NURBS). These NURBS-based finite elements have been studied in depth and it has been shown, that they are particularly well suited for computational analysis leading to qualitatively more accurate results in comparison with standard finite elements based on Lagrange polynomials. Due to these motivating results, NURBS-based finite elements are currently implemented into LS-DYNA. This work outlines the basic ideas of isogeometric analysis and gives a short introduction into NURBS basis functions. The new keyword *ELEMENT_NURBS_PATCH_2D available in LS-DYNA is presented together with various possible options, like shell theories with and without rotational degrees of freedom. Preliminary results on the performance of these new elements are studied by means of a sheet metal forming example discussed in the Numisheet conference 2005.

  • Absorbing Materials - Tests Versus Simulations

    R. Ridky, M. Popovic (SVS FEM); M. Drdlova (Výzkumný ústav stavebních hmot); O. Koutny (Bogges)

    An absorption capacity of soft, viscoelastic materials at high strain rates is included in wide range of practical applications. One of the critical questions in any similar analysis is setup of material properties including all physical constants. There are many kinds of tests analysing dynamic properties of absorbing elements. In many cases testing and also numerical simulations are influenced by many types of measurement and simulation conditions. This investigation was focused on relations between particular testing results in their complexity and related numerical simulations as well. The goal of this investigation is to find a numerical material model of absorbing material suitable for explicit numerical simulation especially focused on blast load. Number of variations in real testing is usually strictly limited because of experiment costs. On the contrary numerical simulations have no limits in number of analysed variants but they have handicap in correlation with reality. This should be solved by combined development of requested products. This analysis used four kinds of real tests with different strain rates as consistent and verified points that numerical models should confirm and fill in unknown gaps between them.

  • Abuse Characterization and Simulation of Battery Cells Using Layered Approach

    David Poulard, Prakhar Amrute, Pierre L’Eplattenier, Kevin Kong, Vidyu Challa, Inaki Caldichoury

    The adoption of electric vehicles (EVs) has brought renewed attention to battery safety, particularly in scenarios where batteries are subjected to mechanical abuse, such as car crashes. The potential for battery cells to catch fire or exhibit thermal runaway under such conditions necessitates a comprehensive understanding of the underlying physics. The complex interplay of structural, thermal, electrical, and electrochemical phenomena presents a formidable challenge for accurate simulation and prediction of battery behavior. In this context, the integration of multiphysics coupling within Ansys LS-DYNA® has emerged as a crucial tool for studying battery abuse and enhancing safety measures.

  • Accelerating elastoplastic material models with spare nonlinear regression: A hybrid approach

    G. Bokil, D. Koch, André Haufe, Holger Steeb

    Evaluating material models in Finite Element (FE) simulations is computationally expensive. Recently, Machine Learning (ML) techniques have been explored for accelerating elastoplastic algorithms. One such method includes replacing a part of the algorithm with an ML model which is called the “hybrid” approach. One of the most commonly used algorithms for ductile materials is the J2-based von Mises hardening elastoplasticity. To improve the performance of this model, an ML-based hybrid algorithm was sought. In this algorithm, the expensive iterative plastic correction step was replaced with a single-step prediction from a SINDY-inspired sparse nonlinear regression model.

  • Accelerating Implicit LS-DYNA® with GPU

    Yih-Yih Lin (Hewlett-Packard Company)

    A major hindrance to the widespread use of Implicit LS-DYNA is its high compute cost. This paper will show modern GPU, cooperating with CPU, can help remove this hindrance. Performance improvement for Implicit LS-DYNA with GPU relative to that without, as well as from recent GPU and X86 processor, will be studied. The study will cover GPU related hardware issues, including GPU Boost, memory and PCI Express Interface.

  • Accelerating Regulatory Test Simulation with LS- DYNA through Process Guidance Technology

    Petter Sahlin, Velayudham Ganesan - ESI Group

    With the strength in implementing best practices process guidance technology has proven dramatically reduced lead times in pre and post processing while meeting the increasing complexity imposed by ever changing safety regulations. Using predefined template processes for regulatory tests, for example for Euro NCAP, ACEA, or FMVSS standards, process guidance technology allows users to be driven or guided by ready made test templates for the most common load cases with LS-DYNA and other crash and safety solvers. When integrated in the pre and post environment modelling and results preparation for load cases such as ECE-21, FMVSS 208, the bumper test, or pedestrian safety, analysis loops are reduced from days and hours down to minutes. This presentation describes why and how process guidance technology is introduced, covering both the technological and organisational aspects and decision made as part of the implementations. With the example of pedestrian safety processes the benefits and issues of implementations are presented.

  • Accuracy Issues in the Simulation of Quasi-Static Experiments for the Purpose of Mesh Regularization

    Anthony Smith (Honda R & D Americas Inc. ), Paul Du Bois (LS-DYNA® Consultant)

    Generating an LS-DYNA® material model from coupon-level quasi-static experimental data, developing appropriate failure characteristics, and scaling these characteristics to mesh sizes appropriate for a variety of simulation models requires a regularization procedure. During an investigation of an anisotropic material model for extruded aluminum, numerical accuracy issues led to unrealistic mesh regularization curves and non-physical simulation behavior. Sensitivity problems due to constitutive material behavior, small mesh sizes, single precision simulations, and simulated test velocity all contributed to these accuracy issues. Detailed analysis into the sources of inaccuracy led to the conclusion that in certain cases, double precision simulations are necessary for accurate material characterization and mesh regularization.

  • Accurate and Detailed LS-DYNA FE Models of the US- and EUROSID: A Review of the German FAT Project

    Ulrich Franz, Oliver Graf - CAD-FEM GmbH, Grafing/ Munich, Germany

    Finite element side impact dummy models of the USSID and EUROSID are of major interest for industry, as more detailed models are required for better prediction capabilities, but still efficiency has to be maintained to some degree. Both type of models, the so-called FAT- USSID and FAT-EUROSID have been developed by CAD-FEM in cooperation with the German Association for Automotive Research (FAT). The main objective was to achieve highly validated finite element models. During the development process the models are vali- dated at three levels: material, component and assembly and tested finally by sled test appli- cations. Additional input was provided by other type of simulations from the LS-DYNA users within the FAT. This paper summarizes the experience gained during the validation and optimization process which may be used as a guideline for an efficient methodology to generate reliable finite element dummy models. Finally, the good performance of the current USSID and EUROSID models is presented for some selected tests.

  • Accurate and efficient dummy models for occupant safety design
  • Accurate Prediction of Projectile Residual Velocity for Impact on Single and Multi-Layered Steel and Aluminum Plates

    M. Raguraman and A. Deb - Indian Institute of Science, Bangalore

    The present paper deals with the simulation of impact of jacketed projectiles on thin to moderately thick single and multi-layered metal armor plates using explicit finite element analysis as implemented in LS-DYNA. The evaluation of finite element modeling includes a comprehensive mesh convergence study not previously reported in literature, using both shell and solid elements for representing single-layered mild steel target plates. It is shown that the proper choice of contact algorithm, mesh density, and strain rate-dependent material properties is crucial as these parameters significantly affect the computed residual velocity. The modeling requirements are initially arrived at by correlating against test residual velocities for single-layered mild steel plates of different depths at impact velocities in the range of ~800-870 m/s. The efficacy of correlation is adjudged in terms of a ‘correlation index’, defined in the paper, for which values close to unity are desirable. The experience gained for single-layered plates is next used in simulating projectile impacts on multi-layered mild steel target plates and once again a high degree of correlation with experimental residual velocities is observed. The study is repeated for single- and multi-layered aluminum target plates with a similar level of success in test residual velocity prediction. To the authors’ best knowledge, the present comprehensive study shows in particular for the first time that, with a proper modeling approach, LS-DYNA can be used with a great degree of confidence in designing perforation-resistant multi-layered steel and aluminum armor plates.

  • Acoustic Aalysis for Impact Sound with LS-DYNA

    R. Ishii (JSOL); T. Yamamoto (Nihon Emsco); Z. Cui, Y. Huang (LSTC)

    LS-DYNA is heavily used to analysis transient phenomenon like car crash and makes a huge achievement about physical simulation in a wide variety of industry. For the goal of LS-DYNA, gone-model , one-codeh as solution it give you, a wide variety of function has been developed at each section. Nowadays, LS-DYNA has been developed further and become possible to evaluate Frequency domain analysis and Acoustic analysis as FRF/SSD/AcousticBEM/FEM etc. It will be important to consider how it works as actual experiment or how to define and use in order to make it possible to evaluate multi-physics extensively. This study is intend for the evaluation to impact sound when a crash occurs between one object and another. To compare the result with experiment and check the both sound by ear would be fulfilled in this paper. The conventional other softwares executing acoustic analysis executes with frequency domain or also do a transient analysis with the assumption that steady state continues in appropriate period. It defines the source of sound on the surface of object vibrating and put it as input to BEM/FEM. As it is well known LS-DYNA can do a transient analysis, it can calculate the source of sound itself. The object vibrates due to collision and the sound propagates to the air. This is the mechanism for sound. LS-DYNA further is able to calculate acoustic analysis taking over previous collision simulation. The comparison between LS-DYNA analysis and experiment is theme of this paper. In the future, In order that LS-DYNA has evaluated physically many kinds of simulation in one-model and it will be alternative to actual experiment. The consideration at this time is first step to confirm the validity and helpfulness of this solution.

  • Acoustic and Vibroacoustic Modeling in LSDYNA Based on Variational BEM

    Ahlem Alia - LML, USTL, Mhamed Souli - LSTC

    The paper concerns the vibroacoustic simulation based on the acoustic Variational Indirect Boundary Element Method (VIBEM) recently implemented in LSDYNA. In this formulation, which assumes a weak acoustic-structure interaction, the transient structural response is computed first. By applying the FFT, it is transformed into a frequency response. The obtained results are taken as boundary conditions for the acoustic BEM. Consequently, the radiated noise at any point into space can be calculated. The efficiency of the present method is checked for both pure acoustic and vibroacoustic problems. The obtained results are in agreement with the analytical solutions.

  • Acoustic Radiated Power and Radiation Efficiency Calculation with LS-DYNA®

    Yun Huang, Zhe Cui (Livermore Software Technology, an ANSYS Company)

    The keyword *FREQUENCY_DOMAIN_SSD in LS-DYNA not only provides convenient solution for steady state vibration analysis for structures, but also raises the possibility for acoustic simulation. For example, it can be combined with acoustic boundary element method (keyword *FREQUENCY_DOMAIN_ACOUSTIC_BEM) or acoustic finite element method (keyword *FREQUENCY_DOMAIN_ACOUSTIC_FEM), to compute the acoustic pressure and sound pressure level for vibro-acoustic problems. In addition, with the option ERP for this keyword, one can perform ERP (Equivalent Radiated Power) analysis to get a quick solution for radiated noise, based on the plane wave assumption for the acoustic waves. A new parameter RADEFF has been added to the keyword *FREQUENCY_DOMAIN_SSD_ERP to run acoustic radiated power computation for baffled plates, and also computes the radiation efficiency. With some examples, this paper explains the difference between the ERP (equivalent radiated power) and ARP (acoustic radiated power) and shows how to use this new parameter to compute the acoustic radiated power and radiation efficiency for vibrating structures.

  • ACP Process Integrated 3B Forming Optimization

    A. Farahani, D. Mittal (Engineering Technology Associates), J. Shaw (US Steel)

    The automotive and steel industries have several initiatives such as the development of 3 rd Generation Advanced High Strength Steels (AHSS), the Nonlinear Strain Path Project and the A/SP AHSS Stamping Team Projects. These initiatives are efforts to expand the forming design space with AHSS to enable increased part complexity, which will allow AHSS to be incorporated into more vehicle components and enable mass reduction. The proposed approach discussed in this presentation will provide a new tool in the effort to expand the forming design space of AHSS.

  • ACP-OpDesign: Optimal Design Gateway: Reveal the Path to Optimized Products

    A. Kaloudis, BETA CAE Systems International AG

    ACP OpDesign is an intuitive and process-guided optimization desktop environment. With its optimization oriented and highly specialized user interface, based on the process depicted as a diagram in the tool, it offers the user the capability to take advantage of an efficient, direct interaction to: - ANSA’s powerful morphing and parametrization functionality - custom-designed META Post-processor tools - Topology and parametric optimization Software (LS-TaSC™ and LS-OPT®) - FEA solvers (LS-DYNA®)

  • ACP_Forming_Brochure.pdf
  • ACP_Natures_Way.pdf
  • ACP_Process_Brochure.pdf
  • Adaptation of a solid self-piercing rivet made of aluminum using numerical simulation to extend the application limits

    M. Schlicht, T. Nehls, P. Froitzheim, Prof. W. Flügge (Fraunhofer IGP)

    Increasing resource efficiency, for example through the consistent application and further development of lightweight construction concepts, plays an important role in the development of the mobility sector. This requires a steadily increasing use of high-strength aluminum alloys in primary vehicle structures. A suitable and efficient process for joining high-strength aluminum alloys is solid self-piercing riveting (SSPR). A major advantage of this process is the elimination of time-consuming preparatory work such as pre-drilling, deburring and positioning of the components to be joined, as the rivet punches through these during the installation process. Due to the high stresses on the rivet during the installation process and the lack of knowledge on the use of ultra-high-strength aluminum alloys as the rivet material, solid self-piercing rivets (SSP-rivets) made of steel are generally used. However, against the background of recyclability, thermal expansion and corrosion protection, the use of aluminum SSP-rivets would be desirable.

  • ADAPTIVE FINITE ELEMENT SIMULATION OF SHEET METAL FORMING PROCESSES USING GRADIENT BASED INDICATORS

    Ramin Moshfegh, Xiangdong Li, Larsgunnar Nilsson, Ramin Moshfegh -Linköping Institute of Technology

    Two mesh refinement indicators based on the gradients of effective stresses (GSIG) and effective plastic strains (GEPS), respectively, are proposed for adaptive finite element analysis of the large deformation, quasi-static or dynamic response of shell structures. The mesh refinement indicators are based on equi-distributing the variation of stresses or plastic strains over the elements of the mesh. A program module is developed and implemented in the nonlinear explicit finite element code LS-DYNA. This module provides element-wise refinement evaluations so that selective mesh refinements are carried out in regions of the mesh where the values of local indicators exceed a user-specified tolerance. The FE model of a conventional deep drawing process is used as numerical model, including both material and geometrical nonlinearities, in order to demonstrate the versatility of the two refinement indicators. Four different refinement indicators, based on angle change, thickness change, GSIG and GEPS based are applied in this investigation. To verify the numerical results against experiments, the anisotropic low carbon steel, FEP04, is used as a reference material. The numerical results are compared with experimental results regarding the thickness distribution versus cup height, effective plastic strain in the deformed sheet and punch force. It is shown that the new proposed indicators can identify finite elements, which have high gradients of stresses or strains so that the mesh is refined in the regions undergoing the most severe deformations and the numerical results are improved.

  • Adaptive Mesh Segmentation for Modelling Dynamic Delamination Initiation and Propagation in Thick Composite Laminates

    J. Selvaraj, L. Kawashita, G. Allegri, S. Hallett (University of Bristol)

    Composites subjected to out-of-plane stresses due to impact loading can suffer from multiple delaminations, but modelling these in large scale structures is a challenging problem. To address this, a methodology is proposed for modelling dynamic delamination initiation and propagation in composites. It adaptively segments the mesh with additional nodes which model the discontinuities in the displacement field caused by delamination. Besides, it also introduces cohesive segments between the newly created nodes so that delamination propagation is controlled by an energy criterion. These adaptations are performed ‘on-the-fly’ in a dynamic explicit Finite Element solution without the need for user intervention, and the mesh segmentation technique does not reduce the time increment size for solution stability. A technique to initialise cohesive tractions with minimal disturbances to the surrounding stress field is also presented. This methodology is described here in detail and demonstrated in the commercial finite element software LS-Dyna. Finally, it is validated against experimental data from the existing literature.

  • Adaptive Sampling using LS-OPT

    A. Basudhar (LSTC)

    LS-OPT is a design optimization and probabilistic analysis package with an interface to LS-DYNA® that provides a flexible framework to solve several types of design problems. In order to solve the problem, it runs simulations at multiple samples that are selected all at once (single iteration) or iteratively [1]. The iterative approach has two main advantages: require prior knowledge about the sufficient number of samples and instead provides a convergence history it can use updated information from the previous runs to select the samples smartly and thus typically reduces the number of required simulations

  • Adaptive Simulated Annealing for Global Optimization in LS-OPT

    Tushar Goel, Nielen Stander - Livermore Software Technology Corporation

    The efficient search of global optimal solutions is an important contemporary subject. Different optimization methods tackle the search in different ways. The gradient based methods are among the fastest optimization methods but the final optimal solution depends on the starting point. The global search using these methods is carried out by providing many starting points. Other optimization methods like evolutionary algorithms that mimic the natural processes like evolution, and simulated annealing that emulates the metal cooling process via annealing can find the global optima but are criticized due to high computational expense. The adaptive simulated annealing algorithm has been proposed to be an efficient global optimizer. This algorithm is implemented in LS-OPT. A few analytical examples and meta-model based engineering optimization examples are used to demonstrate the efficiency of the global optimization using ASA. The optimization results are also compared with the existing LFOPC and genetic algorithm optimization methods.

  • Adaptive Simulated Annealing for Global Optimization in LS-OPT

    Tushar Goel, Nielen Stander - Livermore Software Technology Corporation

    The efficient search of global optimal solutions is an important contemporary subject. Different optimization methods tackle the search in different ways. The gradient based methods are among the fastest optimization methods but the final optimal solution depends on the starting point. The global search using these methods is carried out by providing many starting points. Other optimization methods like evolutionary algorithms that mimic the natural processes like evolution, and simulated annealing that emulates the metal cooling process via annealing can find the global optima but are criticized due to high computational expense. The adaptive simulated annealing algorithm has been proposed to be an efficient global optimizer. This algorithm is implemented in LS-OPT. A few analytical examples and meta-model based engineering optimization examples are used to demonstrate the efficiency of the global optimization using ASA. The optimization results are also compared with the existing LFOPC and genetic algorithm optimization methods.

  • Adaptive Smoothed Particle Hydrodynamics Neighbor Search Algorithm for Large Plastic Deformation Computational Solid Mechanics

    Kirk Fraser (University of Quebec at Chicoutimi)

    Smoothed Particle Hydrodynamics (SPH) has quickly become one of the most popular mesh-free methods since its introduction in 1977. In the recent years, a great amount of research has been focused on addressing some of the common computational time associated with the SPH method. One of the remaining hurdles is the long computational associated with building the neighbor list. Because of the nature of the original SPH codes (astropyshics), the neighbor search is commonly performed for every element in the domain at each time step. In this work, we develop an optimized neighbor search algorithm that is suitable for deployment on NVidia graphics cards (GPU). The SPH code is written using CUDA Fortran. The algorithm can be used for large plastic deformation computational solid mechanics (CSM) problems. The search uses an adaptive algorithm that updates the neighbor list for individual SPH elements depending whether a plastic strain increment threshold is surpassed. The neighbor list as well as the inter-particle spacing (rij) is re-used for elements that do not surpass the search update criteria. Although in this work we use a Cell based search, the algorithm can be easily adapted for the Direct Search, the Verlet List or a Tree Sort approach. Monaghan’s artificial stress term is added to the momentum equation to suppress the common tensile instability. The XSPH approach is used to update the positions of the SPH elements. The algorithm is shown to reduce the overall computation time by up to 70% without loss of accuracy for CSM simulations when compared with the non-adaptive search method.

  • Adaptive Smoothed Particle Hydrodynamics and Higher Order Kernel Function in LS-DYNA®

    Jingxiao Xu, Wei Hu, Bo Ren, Youcai Wu, Xiaofei Pan, C. T. Wu (LST)

    This paper presents the implementation of an adaptive smoothed particle hydrodynamics (ASPH) method for high strain Lagrangian hydrodynamics with material strength in LS-DYNA. In standard SPH, the smoothing length for each particle represents the spatial resolution scale in the vicinity of that particle and is typically allowed to vary in space and time so as to reflect the local value of the mean interparticle spacing. However, in the presence of strongly anisotropic volume changes which occur naturally in most of the applications the local mean interparticle spacing varies not only in time and space, but in direction as well. In ASPH, the isotropic kernel in the standard SPH is replaced with an anisotropic kernel whose axes evolve automatically to follow the mean particle spacing as it varies in time, space, and direction around each particle. By deforming and rotating these ellipsoidal kernels so as to follow the anisotropy of volume changes local to each particle, ASPH can capture dimension-dependent features such as anisotropic deformations with a more generalized elliptical or ellipsoidal influence domain. Some numerical examples are investigated using both SPH and ASPH, also higher order kernel function is studied for both SPH and ASPH formulation. The comparative studies show that ASPH has better accuracy than the standard SPH when being used for high strain hydrodynamic problems with inherent anisotropic deformations, also higher order kernel function has better accuracy than the standard cubic kernel function.

  • Adaptive Thermal Boundary Conditions for Smoothed Particle Hydrodynamics

    Kirk Fraser (University of Quebec at Chicoutimi, Predictive Engineering), Laszlo I. Kiss, Lyne St-George (Predictive Engineering)

    Smoothed Particle Hydrodynamics (SPH) is a robust meshfree approach for the simulation of large plastic deformation processes such as high speed cutting, forging, extrusion, and friction welding. Often, heat transfer is an important consideration for such industrial processes; for this reason, the effects of heat loss from convection, radiation, or flux from the free surface should be included. However, because of the meshfree nature of SPH, the elements located at the free surface can change, and are not typically known at each time step. This difficulty makes application of thermal boundary conditions problematic in SPH simulations. In this work, we describe a robust and efficient adaptive thermal boundary condition algorithm. Our approach uses a straightforward free surface extraction algorithm. Once the free surface elements are found, the appropriate thermal boundary condition can be applied. We describe the SPH boundary formulation for the Dirichlet (defined temperature), Neumann (defined flux), and Robin (convection) boundary conditions. The algorithm is validated against the finite element method and an example of an industrial application, friction stir welding, is presented.

  • Adetailedaircraft tyre finite element modellanding safety assessment for hard

    Hua Guo, Christophe Bastien, Mike V. Blundell, Gary Wood (Coventry University, Dunlop Aircraft Tyres Limited)

    Tyres have an important role in landing gear systems upon aircraft landing and taxing on the ground. The performances of an aircraft tyre under varied load conditions are vital requirements for aircraft safety certification. This paper describes the development of a detailed finite element (FE) model of an aircraft test tyre in order to investigate its performance and assess its safety criteria. The work follows the findings from previous researches [1] [2] [3] [4] and focuses on the aircraft tyre safety assessment under various loading scenarios that were not yet studied. Initially, tyre inflation and static load simulations have been analyzed based on a full-scaled 3D detail LS-Dyna® FE model, replicating the actual geometry and the correlated material properties from industrial experimental data. The dynamic simulations that aim to duplicate tyre load upon aircraft landing scenarios have also been analyzed. Following the comments from aircraft tyre industrial data and guidelines[5] [6], the dynamic simulations have covered the tyre loading scenario from on-road taxing, normal (soft) landing, hard landing to crash landing under different aircraft landing weights. The stresses on tyre/wheel contact areas and on bead cords have been chosen as the safety criteria. The simulation results, analysis and comments have been discussed in great details. The modelling and simulations described in this paper aim to demonstrate the effective use of FE models for aircraft safety assessment, by studying the criteria of the tyre for load cases corresponding with testing and operational scenarios. The development of such predictive model would allow the manufacturers to assess tyre availability during the design process, and also add to the general drive towards the use of more virtual prototypes in an area traditionally reliant on experimental testing.

  • Adiabatic Shear Band Modeling in Inconel-718 Alloy

    Stefano Dolci, Kelly Carney, Paul Du Bois, Cing-Dao Kan (George Mason University)

    The failure mechanism for thick metal plates impacted by blunt projectiles is known as an adiabatic shear band (ASB), which results in a catastrophic failure due to concentrated shear deformation. ASB is generally considered to be a material or structural instability and as such is not controllable. ASBs are a thermodynamic phenomenon occurring at high strain rates and are characterized by large deformations, localized in a narrow band consisting of highly sheared material. Due to the extreme localization of the shear band it is difficult to model it using FEM, because the mesh size needed to capture it is often not practical for real applications. ASBs can control failures in ballistic impacts. For example, the strength characteristics of Inconel 718 are superior to those of Titanium 6Al4V, in quasi-static conditions. Hence, the ballistic limit for the same geometry plates of these materials should be very different. Unexpectedly, tests show that the materials have a similar ballistic limit for a 0.5” plate. The explanation for this similarity is that, inside the ASB the temperature rises to above 700°C, where Inconel undergoes a phase transformation that makes it brittle, causing a sudden failure. Ti6Al4V HPC lattice has a different microstructure than Inconel’s, and so its ASB behavior also differs. 2D analyses are presented, with progressively reduced element sizes until ASB appearance. ASBs of Inconel are shown to have a width of approximately 5 μm. This is far smaller than an element from an “industrial size” mesh. The elements of the mesh need to be smaller than the ASB width in order to capture the localization of shear and the consequent temperature rise in that region. As adiabatic shear band modeling exhibits a strong dependency on mesh size, we propose to neutralize the effects of different mesh dimensions by implementing a new regularization algorithm. The new algorithm will increase the amount of plastic work converted into heat as function of mesh size, where ASBs will occur. The updated model will replicate the ASB characteristics obtained with the ultra-fine 2D mesh using an “industrial size” mesh.

  • Adiabatic Shear Band Modeling in Inconel-718 Alloy

    Stefano Dolci, Kelly Carney, Paul Du Bois and Cing-Dao Kan (George Mason University)

    The failure mechanism for thick metal plates impacted by blunt projectiles is known as an adiabatic shear band (ASB), which results in a catastrophic failure due to concentrated shear deformation. ASB is generally considered to be a material or structural instability and as such is not controllable. ASBs are a thermodynamic phenomenon occurring at high strain rates and are characterized by large deformations, localized in a narrow band consisting of highly sheared material. Due to the extreme localization of the shear band it is difficult to model it using FEM, because the mesh size needed to capture it is often not practical for real applications. ASBs can control failures in ballistic impacts. For example, the strength characteristics of Inconel 718 are superior to those of Titanium 6Al4V, in quasi-static conditions. Hence, the ballistic limit for the same geometry plates of these materials should be very different. Unexpectedly, tests show that the materials have a similar ballistic limit for a 0.5” plate. The explanation for this similarity is that, inside the ASB the temperature rises to above 700°C, where Inconel undergoes a phase transformation that makes it brittle, causing a sudden failure. Ti6Al4V HPC lattice has a different microstructure than Inconel’s, and so its ASB behavior also differs. 2D analyses are presented, with progressively reduced element sizes until ASB appearance. ASBs of Inconel are shown to have a width of approximately 5 μm. This is far smaller than an element from an “industrial size” mesh. The elements of the mesh need to be smaller than the ASB width in order to capture the localization of shear and the consequent temperature rise in that region. As adiabatic shear band modeling exhibits a strong dependency on mesh size, we propose to neutralize the effects of different mesh dimensions by implementing a new regularization algorithm. The new algorithm will increase the amount of plastic work converted into heat as function of mesh size, where ASBs will occur. The updated model will replicate the ASB characteristics obtained with the ultra-fine 2D mesh using an “industrial size” mesh.

  • Adjusting the Contact Surface of Forming Tools in Order to Compensate for Elastic Deformations during the Process

    Knut Großmann, Hajo Wiemer, Andrè Hardtmann, Lars Penter, Sebastian Kriechenbauer - TU Dresden

    Nowadays, despite powerful simulation programs, the tool design process still contains manual and not reproducible work. In specific, the manual die spotting is mostly dependent on the workers experience and consumes a lot of time. A large potential to reduce time and costs is seen by decreasing the die maturing. The paper introduces an approach to obtain deep drawing tools from FE simulation with LS-DYNA, which need less additional manual maturing until good parts can be manufactured. Therefore, the current tool design process was analyzed and it was found out, that not properly assessing elastic tool and press properties in FE simulations in one of a the causes that lead to additional die spotting effort. Hence, a methodology was developed to compensate for the effects of those elastic properties. Depending on their intensity, afore mentioned machine and tool properties are included in the FE model. Based on former research work at the IWM the effects of elastic deformations and dislocations of the die surface on the final shape of the part are calculated. Derived from the calculated deformations, a transformations matrix is calculated and a new die surface is obtained after a few iterations. The new die surface has the same shape under load like the initial die surface without load. The new method was tested through an experimental set-up, which allowed an excessive deformation of the die under load. This experiment does not reflect the reality but serves for general demonstration purposes of the compensation approach. As expected the simulation and experiment show a massive impact of the die deflection on the draw-in of the manufactured part. The die deformation affects the distribution of the blankholderforce on the part. It was found a higher pressure on the die corners and lower pressure in the centre. By means of the compensation method, the die surface was adjusted to achieve that the die surface under load is the same as the initial surface without deformations. The experiments show that the final shape of the part, which was drawn with the compensated die, is very close to the shape, which was predicted without calculating the die deformation.

  • Adjusting the Contact Surface of Forming Tools in Order to Compensate for Elastic Deformations during the Process

    Knut Großmann, Hajo Wiemer, Andrè Hardtmann, Lars Penter, Sebastian Kriechenbauer - TU Dresden

    Nowadays, despite powerful simulation programs, the tool design process still contains manual and not reproducible work. In specific, the manual die spotting is mostly dependent on the workers experience and consumes a lot of time. A large potential to reduce time and costs is seen by decreasing the die maturing. The paper introduces an approach to obtain deep drawing tools from FE simulation with LS-DYNA, which need less additional manual maturing until good parts can be manufactured. Therefore, the current tool design process was analyzed and it was found out, that not properly assessing elastic tool and press properties in FE simulations in one of a the causes that lead to additional die spotting effort. Hence, a methodology was developed to compensate for the effects of those elastic properties. Depending on their intensity, afore mentioned machine and tool properties are included in the FE model. Based on former research work at the IWM the effects of elastic deformations and dislocations of the die surface on the final shape of the part are calculated. Derived from the calculated deformations, a transformations matrix is calculated and a new die surface is obtained after a few iterations. The new die surface has the same shape under load like the initial die surface without load. The new method was tested through an experimental set-up, which allowed an excessive deformation of the die under load. This experiment does not reflect the reality but serves for general demonstration purposes of the compensation approach. As expected the simulation and experiment show a massive impact of the die deflection on the draw-in of the manufactured part. The die deformation affects the distribution of the blankholderforce on the part. It was found a higher pressure on the die corners and lower pressure in the centre. By means of the compensation method, the die surface was adjusted to achieve that the die surface under load is the same as the initial surface without deformations. The experiments show that the final shape of the part, which was drawn with the compensated die, is very close to the shape, which was predicted without calculating the die deformation.

  • Advance in Sheet Metal Forming - One-step Solution, Multi-Beads, Gravity Prebending, Auto Nets, and Local Compensation

    X. Zhu, L. Zhang (LSTC)

    Some of the new features developed since the last conference will be discussed. 1)A fast one-step sheet metal forming program Developed mostly for blank size estimation and forming effect initialization in crash simulation, this powerful feature allows hundreds of parts to be simulated in a very short time. 2)An improvement to the contact draw bead Developed together with Ford Motor Research and Advanced Engineering Laboratory, multiple beads can now be generated automatically based on the base draw bead definition, to represent the actual bead width and forces. This more realistic approach allows for a better blank size prediction and utilization. 3)Pre-bending for gravity simulation Developed together with Ford Motor Company, blanks can now be pre-bent to simulate the various scenarios of stamping press destacker loading of the sheet blank to the draw die. This new approach produces a more realistic gravity-loaded blank shape, resulting in shorter die travel and better stamping quality. 4)Automatic fixture nets for free-standing springback simulation This feature allows for automatic generation of fixture nets of user-specified sizes, in user specified locations, with contacts automatically established, for a free-standing springback simulation. 5)Springback compensation for localized multi-regions Developed together with Chrysler LLC, local compensation of stamping dies can be extended to multiple regions.

  • Advance in Sheet Metal Forming - Failure Criteria, Friction, Scrap Trimming and Adaptive Meshing

    L. Zhang, X. Zhu (LTSC)

    Some of the new features developed since the last conference will be discussed. 1)Directional and pressure sensitive friction model for metal forming Developed together with Ford Motor Research and Advanced Engineering Laboratory, this feature enables definition of Coulomb frictions in any directions in the sheet plane. The friction coefficients can also be scaled based on the contact pressure incurred during the stamping process. 2)Failure criterion for the non-linear strain path for *MAT_036 Developed as a part of the ASP-NSP project, the previously known Formability Index (F.I.) is now implemented together with *MAT_036. Verification of the model will be discussed. 3)Contact-based scrap trimming function Developed together with Ford Motor Company, this powerful feature allows realistic scrap trimming simulation and contact-based kinematic and dynamic transfer from the trim steels to the trimmed scraps. 4)Pre-adaptive along curves for line-die simulation Developed together with Chrysler LLC, a region of user specified size can now be defined for mesh adaptivity along a curve for subsequent line-die simulation.

  • Advanced Finite Element Model for AE-MDB Side Impact Barrier

    M. Asadi , P. Tattersall - Cellbond Composites Ltd., B. Walker - ARUP Campus (UK), H. Shirvani - Anglia Ruskin University (UK)

    This paper represents a new Finite Element simulation model for AE-MDB v3.9 side impact barrier and proposes a method on creating suitable assumptions and material data. Cellbond AE-MDB barrier investigation was carried out to produce an advanced FE model. Experimental Flat Wall and Offset Pole test results were used to validate the accuracy of the developed models. The explicit LS Dyna 3D code was used to model the geometries, and the Material Card data was obtained from several static compressive tests at different angles to characterize the yielding function of the aluminum honeycomb parts. The dynamic models were also validated by a Flat Wall test which represents the crash performance of AE-MDB barrier. For dynamic tests the barrier was mounted on a mobile trolley and it was tested at speed of 35 km/h. In Offset Pole test, the AE-MDB barrier was subjected to an asymmetric crush with a rigid vertical pole in which test speed was 20 km/h. The final comparison of the overall results demonstrates a good correlation between test data and CAE results for both the Flat Wall and Offset Pole tests.

  • Advanced Mode Analysis for Crash Simulation Results

    Clemens-August Thole

    Potential scatter of simulation results caused for exampleby buckling, is still a challenging issue for the predictability. Principle component analysis (PCA) is a well-known mathematical method for data analysis. In order to characterize scatter PCA analysis was applied to the simulation results from a number of runs using all node positions at all time steps. For industrials relevant problems the size of the data base is larger than 100 GBytes (even, if compressed by FEMzip1[7]) . As a result the major components dominating the differences between the simulation results are available. Since PCA is a mathematically based method, the selected modes do not separate different physical effects like buckling at different parts of the model. PCA rather tries to maximize the variations by combining several physical effects into one mode. Difference PCA(DPCA) applies PCA analysis to the results for each part and time step. By analysis of the related covariance matrices, the local dimension of the scatter subspace can be identified and correlation between the scatter at different places can be analyzed. Using DPCA, different origins of scatter can be identified and physically meaningful components can be determined. The paper introduces the approach and shows results for an industrial model.

  • Advanced Modeling and Drop Simulation With New Features of LS-DYNA

    Jason Wu

    Phone drop simulation is an important application of LS-DYNA in electronics industry. The application has been widely used in all leading companies to produce electronic handsets, like Nokia, Motorola, and Samsung. Since more new features complemented in 970 version of LS-DYNA, phone modeling and drop simulation strategy has changed a lot to obtain more accurate and quick results. This paper introduces new methods, and recent development of phone modeling and drop simulation, based on author’s experiences in recent years. The paper is focused on using right element type in LS-DYNA element library and some new strategies to establish better phone model and drop simulation. The paper provides benchmarks to verify the modeling strategies. The paper still gives an example for advanced application of LS-DYNA in multiply impact simulation.

  • Advanced MPP Decomposition of a SPH Model

    Christian MOUTELIERE, Vincent LAPOUJADE (DynaS+), Antoine MILLECAMPS (SNECMA)

    SPH, Smoothed Particle Hydrodynamics, is a very efficient tool to model industrial problems where large deformations occur. However, one disadvantage of the SPH technique is the relative expensive cpu cost compared to standard Finite Elements. Using the MPP version of LS-DYNA® allows users to handle larger problems (up to more than millions of particles) in a reasonable time. Due to the meshfree nature of the SPH method, standard decompositions used for finite elements can sometimes lead to very bad speed-up of the code. Users have to be aware of some options and rules to define customized decompositions in order to minimize communications between processors and get very good load balancing. Two classes of models are presented for addressing all possible situations with respect to optimizing MPP decomposition of a calculation based in whole or in part on the SPH technology. The first one is a pure SPH model of a high velocity impact of a sphere on a plate. The second one is a coupled FE-SPH model of a bird impacting a set of fan blades of an engine. Two versions of the same problem will be studied: for the first, shell elements are used for the modeling of fan blades whereas for the second, solid elements are used.

  • Advanced Pedestrian Legform Impactor (aPLI)

    Katharina Stielau (CDH AG), David Blauth (ATD-MODELS GmbH)

    Pedestrian protection aims to reduce injuries in car-to-pedestrian impacts. It is the subject of increasingly stringent worldwide statutory and consumer rating requirements and is thus increasingly important in current vehicle development. With electric vehicles, which are not always readily noticed by pedestrians, there is an even higher risk of pedestrian injury. Passive pedestrian protection is, active safety systems notwithstanding, the final countermeasure to reduce serious and fatal pedestrian injury. The current test assessment for pedestrian protection uses three “impactors” in different loading scenarios designed to represent injuries to specific parts of the human body, such as the head, the upper leg and the lower leg. Recent development of the Advanced Pedestrian Legform Impactor (aPLI) focuses on enhanced biofidelity of the lower extremities to address long-bone fractures, knee ligament injuries and pelvis fractures in a single impactor instead of the separate, independent, lower leg and upper leg impactors. To date, the requirements for the aPLI are applied to the EuroNCAP 2022 regulations. But as seen with the previous development of the FlexPLI, it is to be expected that the global statutory requirements will be influenced by global consumer rating requirements. The CAE development process focuses on high accuracy simulations within the vehicle development process, using reliable and robust FEM vehicle and impactor models. The aPLI-FE models represent the Cellbond aPLI SBL-A hardware and have been developed in close cooperation with the hardware manufacturer. Utilizing many years of experience in the field of occupant protection with HIII models, the FE model ATD-aPLI was also developed with extensive feedback from partners in the German automotive industry. Special modelling techniques were developed and applied in LS-DYNA®. The ATD-aPLI model was validated by material and component investigations and by experiments in generic test rigs. Models for future hardware versions will be released regularly in preproduction and final versions. Automotive manufacturers face new challenges in the CAE process and hardware tests using the new aPLI. Despite similarities with the previous FlexPLI, the attached upper body mass of the aPLI has a strong influence on the impactor kinematics and particularly the femur load. This paper highlights some characteristics of the aPLI and describes a sensitivity analysis using LS-DYNA within the framework of a typical CAE development process.

  • Advanced Plasticity & Fracture for Structural Car Body Metals in Crashworthiness CAE analysis: SAMP-1 plus GISSMO

    Alejandro Domínguez, Pablo Cruz, Lluis Martorell, Adrián Ros, Eduardo Martin-Santos

    This paper describes an engineering process to generate material cards for forefront crashworthiness CAE analysis that properly capture both plastic and fracture behaviour of car body structural metals. The main objective of the paper is to show that advanced plasticity approaches can be used without significantly increasing the complexity of the overall material characterization process. The paper is mainly centred in metals plastic characterization for shell elements although some important relationships with the fracture characterization will be also discussed. Before defining the engineering process, it is necessary to tackle some misleading general ideas that the automotive CAE community normally assumes as correct for metals like steel or aluminium alloys.

  • Advanced Results Databases Compression Techniques to Allow their Efficient Use in Results Data Management Systems

    Antonis Perifanis, Stelios Karapantazis, Dimitrios Krontsos, BETA CAE Systems S.A.

    The usage of automated post processes is the rule nowadays. Simple scenarios include saving only specific LS-DYNA® results in post processing software native databases whereas in more sophisticated cases a series of report data are stored in data management systems. New challenges arose this way relevant to the need to download the report data from a data server as quickly as possible, display and compare them in the best way allowing in the same time as much access to the original results data as possible.

  • Advanced Simulation Methods for the new Porsche Panamera

    F. Sautter, H. Hogenmüller - Dr.-Ing. h.c. F. Porsche

    The Porsche Panamera brings together for the first time the virtues of a sports car with Porsche’s own interpretation of a classical Gran Turismo. This new segment is characterised by the balance between sportiness on the one hand and comfort, luxury and long-range touring characteristics on the other. The fact that the development was new, with no previous model available to use as a basis for vehicle parameters and characteristics, created a significant challenge. To meet the requirements of a reliable, target-oriented vehicle development, major emphasis was placed on virtual development tools. Advanced simulation methods found their application in the early concept definition, and were integrated into the complete vehicle development process. The CAE tools and methods were also developed further during the project to meet the specific project needs. The following paper demonstrates these points using the example of design for passive safety. The paper describes the new Digital Product Development Process, with its centrally managed multi- disciplinary Digital Protoypes, which was introduced for the Panamera project. Furthermore, a selection of the CAE tools used in the development of the Panamera and their evolution are discussed. The main focus of the CAE tools was to accelerate and provide a qualitative improvement to the product development process.

  • Advanced Simulation Methods for the new Porsche Panamera

    F. Sautter, H. Hogenmüller - Dr.-Ing. h.c. F. Porsche

    The Porsche Panamera brings together for the first time the virtues of a sports car with Porsche’s own interpretation of a classical Gran Turismo. This new segment is characterised by the balance between sportiness on the one hand and comfort, luxury and long-range touring characteristics on the other. The fact that the development was new, with no previous model available to use as a basis for vehicle parameters and characteristics, created a significant challenge. To meet the requirements of a reliable, target-oriented vehicle development, major emphasis was placed on virtual development tools. Advanced simulation methods found their application in the early concept definition, and were integrated into the complete vehicle development process. The CAE tools and methods were also developed further during the project to meet the specific project needs. The following paper demonstrates these points using the example of design for passive safety. The paper describes the new Digital Product Development Process, with its centrally managed multi- disciplinary Digital Protoypes, which was introduced for the Panamera project. Furthermore, a selection of the CAE tools used in the development of the Panamera and their evolution are discussed. The main focus of the CAE tools was to accelerate and provide a qualitative improvement to the product development process.

  • Advanced Simulation of Polymer Composite SMC Compression Molding using Fluid-Structure Interaction in LS-DYNA®

    Dominic Schommer, Miro Duhovic, Florian Gortner, Martin Maier (Institut für Verbundwerkstoffe GmbH)

    Thermoset Sheet Molding Compounds (SMC) are becoming more and more popular as lightweight construction materials in the automotive industry. SMC compression molding is a forming process in which a pre-cut SMC-Prepreg is placed within a heated mold and is first pressed into shape before being cured. By closing the mold, the thermoset resin is forced to flow and takes the randomly orientated fiber reinforcement present, along with it. The flow behavior of the SMCs can be characterized by press rheometry. In a typical press rheometry test, certain data recorded during the test, specifically press force, tool closing speed, position and time together with the known tooling geometry (plate surface area), are used to develop and verify a finite element characterization model in LS-DYNA using the relevant Arbitrary Lagrange Eulerian (ALE) capable material model. In this work, the Fluid Structure Interaction (FSI) capabilities in LS-DYNA are used to model the flow ability of the SMC material. No independent effects of the resin cure on the materials rheology are taken into consideration. The characteristic data obtained from the real press rheometry tests are used to calibrate the material model so that it can be used to predict the mold filling behavior of more complex tooling scenarios. As an example for forming a complex real part, the compression molding of a ribbed automotive spoiler test part is analyzed upon complete closing of the mold. The goal of the simulation is to provide information about the suitability of the tooling design geometry and the processing parameters. A simplified two dimensional model of the ribbed automotive spoiler part shows, that the unrecognized effects inside the material cause a failure in the simulation in certain situations. A future version of the model should make it possible to analyze the nature of the SMC part, more specifically, the flow profile, fiber orientation and resulting volume fraction in the individual sections of the part, in particular the rib section, along with chemical curing of the resin.

  • Advanced Simulations of Cellular Structures with LS-DYNA

    Matej Vesenjak, Zoran Ren - University of Maribor

    Cellular structures have an attractive combination of physical and mechanical properties and are being increasingly used in modern engineering applications. In this study the influence of different parameters (type of base material, type of pore filler, relative density, size of the cellular structure, strain rate) on behaviour of open- and closed-cell cellular structures under impact loading was investigated by means of computational simulations using the explicit finite element code LS-DYNA. The influence of gas filler inside the closed-cell cellular structure was analysed using the representative volume element and the airbag model. The analysis of the fluid filler behaviour inside the opencell cellular structures was done with combination of the Finite element method and the Smoothed particle hydrodynamics meshless method. The base material properties and macroscopic behaviour of cellular structures with and without fillers were determined with experimental measurements of appropriate specimens under quasi-static and dynamic uniaxial loading conditions. Computational simulations show that the base material has the highest influence on behaviour of cellular structures under impact conditions. The increase of relative density and strain rate results in increase of the cellular structure stiffness. Parametric computational simulations have also confirmed that the filler influences macroscopic behaviour of the cellular structures, which depends on the loading type and the size of cellular structure. In open-cell cellular structures with higher filler viscosity and higher relative density, increased impact energy absorption is observed.

  • Advancements in Material Modeling and Implicit Method for Metal Stamping Applications

    Xinhai Zhu, Li Zhang - Livermore Software Technology Corporation

    A review of recent developments in stamping manufacturing will be conducted. The review will be focused on discussions surrounding new features related to static implicit binder wrap, advanced material modeling with Yoshida’s non-linear kinematic hardening in conjunction with Hill’s 1948, Barlat 1989 and Barlat 2000 yield criteria.

  • Advances in Adaptive Thermal-mechanical Metal-forming Simulations in LS-DYNA

    Rudolf Bötticher - TMB GmbH

    The vision of LS-DYNA is to become multiphysics and adaptive. LSTC endeavours to make the LS-DYNA code as complete, accurate and easy to use as possible. This contribution evaluates the features for adaptive thermal-mechanical simulations that are in recent LS-DYNA versions with a focus on implicit 3D. Implicit solutions do not need mass scaling as explicit forming simulations often use. Implicit element free Galerkin (EFG) elements are successfully used for a bulk metal forming test case (upsetting with a non-trivial stamp) with adaptive remeshing of tetrahedrons. The interplay of adaptive remeshing with the contact algorithm is highlighted. Additionally plastic heating of 3Dshells in a deep drawing benchmark example is assessed Some remarks regarding the features for post-processing adaptive simulations with full remeshing in LS-PrePost are evaluated.

  • Advances in Fatigue Analysis with LS-DYNA

    Yun Huang, Zhe Cui, Livermore Software Technology Corporation

    Fatigue analysis is critical to the design and optimization of metal structures and components. This paper reviews the recent development in fatigue analysis with LS-DYNA. Both frequency domain and time domain fatigue solvers have been implemented to LS-DYNA. They can be used towards different simulation situations. Some examples are provided in this paper, to illustrate how to use these fatigue analysis methods. The plan on future development of the fatigue solvers in LS-DYNA, is also discussed.

  • Advances in IGA for Sheet Metal Forming Applications

    S. Hartmann (DYNAmore); D. Benson (LSTC); A. Nagy (LSTC)

    In the last years, Isogeometric Analysis (IGA) has become very popular in the scientific research community. Various types of basis functions are investigated by the researchers, while the most widely used geometry representation in the Computer-Aided-Design (CAD) community is based on NURBS. It has been shown, that NURBS are particularly well suited for finite element analysis leading to qualitatively more accurate results in comparison with standard finite elements based on Lagrange polynomials. This work will give a short overview about the general possibilities of IGA with NURBS in LS-DYNA and focus on the recent advances for the analysis of Sheet Metal Forming Applications. Therefore the benchmark example from the Numisheet 2005 conference on “Forming of an Automotive Underbody Cross Member” (BM2) [1], which has been analyzed by Hartmann et al. [2] in 2011 using one of the first IGA implementations in LS-DYNA, is reanalyzed to demonstrate the progress made since then.

  • Advances in LS-DYNA ® Metal Forming (I)

    Xinhai Zhu, Li Zhang and Yuzhong Xiao (LSTC)

    Some of the new features developed since the last conference will be discussed. 1) Movable adaptive fission/fusion box The movable fission/fusion box is an essential enabler in completing a simulation in a efficient manner, especially in cases where deformation is relatively localized. Related keywords include: *CONTROL_ADAPTIVE, *DEFINE_BOX_ADAPTIVE. 2) Checking fixture clamp definition and simplification of FORMING contact definition The keywords, *DEFINE_FORMING_CLAMP, *DEFINE_FORMING_CONTACT, are created to ease the user definition of checking fixture clamps and contacts definition. 3) New options in *INTERFACE_BLANKSIZE Additional features under this keyword allow users to include/exclude a particular trim lines and to define symmetric conditions for the part, using keywords: *INTERFACE_BLANKSIZE_SCALE_FACTOR, *INTERFACE_BLANKSIZE_SYMMETRIC_PLANE. 4) Some major improvements to *CONTROL_FORMING_SCRAP_FALL In conjunction with the Ford Motor Company, the original “Constraint Release” method is evolved into the “Scrap Trimming” method, making the scrap trimming and fall simulation much more closer to reality. 5) 2D and 3D trimming of solids and laminates An important feature in metal forming simulation using solid elements and laminates, 2D and 3D trimming are now available. 6) Automatic offset of tool element/node IDs The creation of the keyword *INCLUDE_AUTO_OFFSET enables user to offset individual tools with overlapping element/node IDs, allowing the user to bypass a metal forming GUI when updating just one or two tooling pieces. 7) Positioning of unfolded blank in one-step simulation Allows user to specify three points used to position the unfolded blank relative to the part’s initial position and orientation..

  • Advances in LS-DYNA ® Metal Forming (II)

    Xinhai Zhu, Li Zhang and Yuzhong Xiao (LSTC)

    Some of the new features developed since the last conference will be discussed. 1) Implementation of Stoughton’s Non-Associate Flow Model (*MAT_260A) Strain rate sensitive, non-associated flow material model suitable for metal forming simulation. 2) Implementation of Mohr’s Non-Associate Flow Model (*MAT_260B) Strain rate sensitive and temperature softening effect coupled with a non-associated flow rule, combined with a ductile fracture model based on Hosford-Coulomb fracture initiation model, suitable for metal forming and crash simulation. 3) Best fitting of meshed (including STL) parts with *CONTROL_FORMING_BESTFIT Correlation study of simulated springback with scanned STL file made easy. 4) Tool mesh checking/fixing and physical offset of tools (*CONTROL_FORMING_AUTOCHECK) This feature fixes tooling meshes arising from bad tool CAD surfaces, automatically make tool normal consistent and in required orientation, and offsets the tool mesh to create an opposite side of the tool. 5) Formability Index (F.I.) extension to *MAT_036, *MAT_125 and *MAT_226). Predictions of sheet metal failure under non-linear strain paths are extended to aforementioned material models. 6) Implementation of a Cyclic Fatigue Modeling (*MAT_165B) A mixed isotropic and kinematic hardening model suitable for small strain cyclic fatigue modeling.

  • Advances in LS-DYNA® for Metal Forming (I)

    Xinhai Zhu, Li Zhang, Yuzhong Xiao, HouFu Fan, Livermore Software Technology Corporation

    • Enhancements in *CONTROL_FORMING_ONESTEP • Smoothing of strain ratio (β) for failure prediction under nonlinear strain paths, with * CONTROL_ FORMING_TOLERANC • “Soft 6” contact improvement for gage pin contact • Weld line mapping with *INTERFACE_WELDLINE_DEVELOPMENT • Improvements in *BOUNDARY_SPC_SYMMETRY_PLANE (SET) • Improvements in springback compensation • Improvements in *ELEMENT_LANCING

  • Advances in LS-DYNA® for Metal Forming (II)

    Li Zhang, Xinhai Zhu, Yuzhong Xiao, HouFu Fan, Livermore Software Technology Corporation

    • New features in state output with *CONTROL_FORMING_OUTPUT • Automatic change from shell to thick shell elements with *CONTROL_FORMING_SHELL_TO_TSHELL • Define material hardening behavior in LS-DYNA with *DEFINE_CURVE_STRESS • Uniform mesh refinement inside a curve loop with *CONTROL_ADAPTIVE_CURVE • Vector option in *CONTROL_FORMING_BESTFI, and LS-PrePost® 4.5 Best-fit GUI • Sandwiched part mesh adaptivity • New capabilities in 2D and 3D trimming of solids, laminates, and 2D trimming of TSHELL

  • Advances in LS-DYNA® Metal Forming (II)

    Li Zhang & Xinhai Zhu (LSTC)

    Some of the new features developed since the last conference will be discussed. 1) Lancing – instant and progressive Cutting of sheet metal during forming to alleviate thinning and splits. 2) Auto close of open trim curve loop Improvement in trimming simulation by automatically closing an open trim curve. 3) Tailor-rolled blank thickness specification Specification of thickness field of a tailor-rolled blank for any ensuing simulation. 4) Springback compensation referencing original tool mesh Compensation using the original tool mesh for iterations to improve tool surface geometry. 5) Springback compensation – for small part shape change Compensation made easier for those parts with small shape changes that do not affect springback results. 6) Simulation-based blank size optimization A significant development in blank size and trim line optimization of stamping dies.

  • Advances in LS-DYNA® Metal Forming (I)

    Xinhai Zhu & Li Zhang (LSTC)

    Some of the new features developed since the last conference will be discussed. 1) Gaging pin contact improvement New contact treatment for edge contact between gaging pin and sheet blank edge during gravity loading. 2) Output control for parameterized input Specifying D3PLOT and INTFORC outputs made easy for parameterized input. 3) Gravity loading – switching between implicit dynamic and implicit static Taking advantage of the best of both dynamic and static methods. 4) Polygon adaptive box A more flexible adaptive remeshing control. 5) Maximum ID specification for blank adaptive remeshing Setting starting element and node ID for an adaptive blank in a line-die simulation. 6) Flange unfolding Unfolding of deformable flanges onto addendum for trim line development.

  • Advances in Simulating Corrugated Beam Barriers under Vehicular Impact

    Akram Abu-Odeh (Texas A&M Transportation Institute)

    W-beam guardrail systems are the most common roadside railing systems used by many road authorities worldwide. They have been used for decades as roadside barrier to protect errant vehicles from intruding into hazardous areas. This paper gives a description of this rail system and recent methods to simulate its performance under roadside impacts. The availability of simulation technologies such as LS-DYNA® makes it possible to evaluate the performance of guardrail systems under given impact condition. A predictive simulation example and a subsequent crash test are presented as how simulation can be integrated into roadside safety hardware design process.

  • Advances in Simulating the Processing of Composite Materials by Electromagnetic Induction

    M. Duhovic, P. Mitschang, M. Maier (Institut für Verbundwerkstoffe GmbH, Germany), I. Caldichoury, P. L'Eplattenier (LSTC)

    In the previous installment of this work, a flat spiral "pancake" type coil geometry and two different plate material types with large differences in electrical and thermal conductivity (structural steel and carbon fiber reinforced polymer composite) were used to perform static plate induction heating characterization experiments for the purposes of characterizing the heating behavior of both materials in preparation for continuous induction welding simulations. The static plate heating tests were validated experimentally in two Finite Element Analysis (FEA) software codes including LSTC's LS- DYNA® 980 (R7) solver. Following on from this initial work, a simulation test-bed has been created in order to study the continuous induction welding of two joining partners. The simulation test-bed mimics an experimental setup developed at the Institut für Verbundwerkstoffe (IVW) GmbH which considers a two-dimensional joining setup (two flat overlapping plates) and allows a more complete investigation of the thermal behavior that occurs during a continuous induction welding process. 3D surface plots of the top surface temperatures which are generated across the entire width of the joint as well as along its length can be investigated for different welding speeds and induction welding processing parameters. More importantly, the same types of surface plots can also be generated at the joining interface providing a complete view of the temperature profile that occurs during the process at this important location. This information can be used to decide on the optimum processing parameters to ensure that the material anywhere at the joining interface always remains within its prescribed upper and lower processing temperature limits. With its three-way physics coupling, the simulation test-bed also allows the consideration of further processing parameters including the influence of roller contact and additional top surface cooling via a moving air-jet nozzle for different induction welding speeds.

  • Advances in the Measurement and Modeling of Plastics for Impact Simulations

    Hubert Lobo - DatapointLabs

    High strain-rate properties have many applications in the simulation of automotive crash and product drop testing. These properties are difficult to measure. Previously, we described a novel inferential technique for the measurement of the properties of polycarbonate. In this paper, we demonstrate that the technique appears to work for a variety of polymers. We also show that plastics exhibit different kinds of high-strain rate behaviors. It is important to use an appropriate LS-DYNA material model for valid simulation results.

  • Advances on the Incompressible CFD Solver in LS-DYNA

    Facundo Del Pin - Livermore Software Technology Corporation

    The present work will introduce some of the resent developments in the Incompressible CFD (ICFD) solver currently under development in LS-DYNA. The main feature of this solver is its ability to couple with any solid model to perform Fluid-Structure interaction (FSI) analysis. Highly non-linear behavior is supported by using automatic re-meshing strategies to maintain element quality within acceptable limits. In this work we will introduce the additional features for conjugate heat transfer, turbulence model, biphasic flow, some new feature in terms of mesh generation like boundary layer meshing and MPP.

  • Ageing Effect on Crashworthiness of Bus Rollover

    A.H. Iskandar, Q.M. Li (University of Manchester, UK)

    International standards related to protection of occupants in rollover accidents are generally applied on new vehicles and regulated for design approval. However, there is no standard regulation governing rollover crash performance of aged vehicles and no proper systematic test to monitor it. It is known that vehicle structural integrity deteriorates after years of operation undergoing various service environments and conditions. The scenario is worsen if the vehicle is poorly maintained and still in operation beyond its lifespan. These factors directly influence the vehicle crashworthiness level and affects its safety. The present paper attempts to show how ageing factors like corrosion and deterioration of mechanical properties may change the overall vehicle structural strength and hence its crashworthiness performance. As a case study, rollover analysis according to European standards (UNECE R66) was set up on a finite element bus model using LS-Prepost and simulation was performed using LS-DYNA . Different levels of condition due to ageing effect were included in the model to examine the changes of rollover performance of the bus. Aged bus rollover studies from real world crashworthiness investigation in Malaysia were referred for comparison to support the argument. Result shows that ageing factors directly influence the performance of vehicle crashworthiness.

  • Agenda.pdf
  • Agile Dummy Model Development Illustrated by Refinement Activities of the WorldSID Shoulder Model

    R. Brown, G. Stokes (Jaguar Land Rover), U. Franz, S. Stahlschmidt (DYNAmore)

    The Agile Software Development is a method that promotes adaptive planning, evolutionary development, early delivery, continuous improvement, and encourages rapid and flexible response to changes. This method is established in the development of software and influences also many other development processes. The employees at DYNAmore are developing dummy models together with a consortium of car companies since decades. The models are used world wide by almost all automotive companies that run LS-DYNA to design their restraint systems.

  • Aid Design Die of Auto-Body Using Numerical Simulation of 3-D Sheet Metal Forming Processes

    Ninig-an Hu, Ning-yan Zhu - SAE China (Society of Automotive Engineering of China)

    It has been well applied in automotive manufacture of China about the technology of the numerical simulation of 3-D sheet metal forming processes during the recent years. Besides helping tool designers and artificers find optimal shapes of technical surface on the die, DYNAFORM is used in the early stages of the auto-body to work over the formability of various parts. In addition to the stamping process, the new forming technologies can be analyzed with DYNAFORM to find more efficient methods and optimal processing parameters for parts of the auto-body. The paper discussed how DYNAFORM is used to select a critical part in my plant and demonstrated how numerical simulation can reduce the developing time and costs of tools. For example, the formability analysis for the drawing die of the inside rear door on the car was performed using the numerical simulation of 3-D sheet metal forming processes. It is well known that the occurrences of both fracture and wrinkle were the two encountered difficulties in the stamping process. The numerical simulation was performed to analyze the metal-flow that caused the fracture and wrinkle on the draw-bead and it also acted to analyze the change of the blank’s outline that could bring up the fracture or wrinkle. The strain distributions were obtained from the numerical simulations and were also used in conjunction with the forming limit diagram to predict the onset of the fracture. The effect of blank-holder pressure and friction on the occurrence of the fracture and wrinkle was researched. To prevent the formation of the fracture and wrinkle, according to the above formability analysis of the numerical simulation, an optimum shape of the technical surface, the draw-bead distribution and sizes on the drawing die surface and the blank’s outline were finally determined.

  • Air Blast Reflections and Angle of Incidence

    Len Schwer (SE&CS)

    The Unified Facilities Criteria 3-340-02 provides blast wave reflection ratios as a function of angle-of-incidence as Figure 2-193. However no text is provided indicating the source of this information. A knowledgeable source provided that the figure combines experimental and analytic results. In an effort to assess the UFC information, comparisons are made two different sets of small scale experiments and LS-DYNA Eulerian simulation results. These comparisons are agree fairly well with UFC except in the region of the critical angle-of-incidence where there are large differences. Of interest to LS-DYNA users, the comparison also includes the simple analytical expression for reflection ratios as a function of angle-of-incident proposed by Randers-Pehrson and Banister, and used in the LS-DYNA algorithm Load Blast Enhanced. It is shown that the Randers-Pehrson and Banister representation of reflection ratios is a lower bound on the above mentioned experiments and LS-DYNA simulations.

  • Airbag Folding for LS-DYNA using Generator4

    L. Benito Cia (GNS)

    Generator4 is a preprocessor that helps users modeling the most complex CAE designs, from geometry handling and meshing to simulation definition. Characterized by its flexibility, this multi-platform software allows engineers to define calculations for the finite element solver LS-DYNA®, as well as for multiple other solvers. Airbag modeling represents a great challenge for CAE Engineers, where complex processes with high accuracy demands are combined with short cycle times. In order to ease up engineers work at the airbag optimization field, Generator4 includes the Pre-Simulation module.

  • Airbag Folding with Generator4 and LS-DYNA® a Generic Process

    Leyre Benito Cia, Christoph Kaulich, GNS-mbH (Gesellschaft für Numerische Simulation)

    Generator4 is a pre-processor that helps users modeling the most complex CAE designs, from geometry handling and meshing to simulation definition. Characterized by its flexibility, this multi-platform software allows engineers to define calculations for the finite element solver LS-DYNA, as well as for multiple other solvers. Airbag modeling represents a great challenge for CAE Engineers, where complex processes with high accuracy demands are combined with short cycle times.

  • Airbag Folding with JFOLD Latest Developments and Case Studies

    Richard Taylor, Ove Arup & Partners International Limited;, Toru Ishizuka, Mayumi Murase, Shinya Hayashi, JSOL Corporation

    JFOLD is a software tool for simulation based airbag folding in LS-DYNA®. Today’s airbag deployment analysis demands accurate folding of complex designs, but this is often a very time consuming process requiring expert input. JFOLD’s continuous development focuses on making the process simpler and quicker and to give the non-expert access to complex folding techniques. This is achieved through three core elements: intuitive user interface, built-in customisable tool libraries and realistic, state of the art examples and tutorials.

  • Airbag Folding with JFOLD - Latest Developments and Case Studies

    R. Taylor (ARUP); S. Hayashi (JSOL)

    JFOLD is a software tool that helps users perform simulation based airbag folding in LS-DYNA. Today’s airbag deployment analysis demands accurate folding of complex designs, but this is often a very time consuming process requiring expert input. JFOLD’s continuous development focuses on making the process simpler and quicker and to give the non-expert access to complex folding techniques. This is achieved through three core elements: intuitive graphical interface, built-in customisable tool libraries and realistic, state of the art examples and tutorials. Our presentation will describe a driver’s airbag case study of two folding patterns with deployment validation using CPM. Two methods of folding a passenger airbag will also be shown, including and a novel way to quickly flatten the bag from 3D to 2D. To further reduce airbag development cycle times and cost, a new airbag morphing application is under development to help the user optimise the design in a virtual environment. This and other new features will be presented.

  • Airbag Inflator Models in LS-DYNA ®

    Kyoung-Su Im, Zeng-Chan Zhang, and Grant O. Cook, Jr. (LSTC)

    New inflator models for the automotive air bag are developed for the pyrotechnic and hybrid inflation modes. Several propellant examples including Sodium azide(NaN 3 ), Azodicarbonamide(C 2 H 4 N 4 O 2 ), and Guanidine nitrate(CH 6 N 4 O 3 ) are designed for users. To control the gas compositions into the airbag and the flame temperature in the combustion chamber, we modified an existing chemical equilibrium code, PEP(Cruise,1973) and provide a user-friendly code for users to develop their own propellant models. The inflating process is modeled by applying basic conservation laws to the several sub-sections of the inflator. Unlike existing inflator models, a new theoretical approach in a LS-DYNA model is provided. Advantages and disadvantages are discussed for the pyrotechnic and the hybrid models. In addition, we make available detailed descriptions of keyword files with comprehensive examples for the propellant ingredient control, cold and heat flow setup, and output file format options, which can be used to continue the air bag simulation with LS-DYNA’s ALE, SPH, and CESE airbag simulation capabilities.

  • AIRBAG SIMULATION WITH LS-DYNA PAST – PRESENT – FUTURE

    A. Hirth - DaimlerChrysler AG, Germany, A. Haufe - Dynamore GmbH, Germany, L. Olovsson - IMPETUS Afea AB, Sweden

    During the last decade the simulation of the airbag deployment process has become a standard application of explicit finite element codes. At the beginning of the development the focus was to capture the influence and improve the results of dummy impact on fully inflated airbags. Later the deployment kinematics of folded airbags, different folding techniques and vent-hole design became more and more important. With the requirement to comply with FMVSS 208, i.e. Out-of-Position load cases, it became apparently necessary to include the interaction between the internal gas flow and the fabric airbag structure. Hence coupled algorithms that allow for interaction between the discretized gas flow and the airbag structure were the main focus during the past five years. The present paper aims to sketch the development history of airbag deployment simulations from the very beginning of the late 1980s to the current, highly sophisticated models available in LS-DYNA. Different modelling techniques will be shown and their advantages, drawbacks and the necessary effort to gain useful results will be discussed.

  • AirbagApplication for Structural Racing Car Component

    Alessia Prato, Marco Anghileri, Andrea Milanese (Dipartimento di Scienze e Tecnologie Aerospaziali, Italy), Chiara Marozzi (CRM Group)

    In motorsports, there is a deep research in order to make cars more and more competitive, throughout an accurate study on aerodynamics, powerful and advanced engines, structural component design, materials and, of course, on racing strategy. That’s even more true when racing conditions are extremely severe, like in endurance races, such as 24 Hours of Le Mans, where changes in drivers and in racing conditions make the race more exciting. To improve performances, weight is one of the most strict design conditions: a lighter car is faster, more efficient and more competitive so that performances can be improved, with more controllability in acceleration and braking phases, reducing emissions and consumptions. Evolution in studies upon materials and structural applications has got a key role to reduce weight and the use of innovative structures is an open field for experimental tests. Many research works were performed upon materials used in motorsports, especially composite fiber reinforced ones. In [1], Adam presented a general overview on composite mechanical characteristics, production methods, and design principles for racing cars composite applications. In [2], a similar study was presented by Cole and Sherman referring to different light-metals and their use for automotive structural components. Innovative structural applications on car components were also studied in order to improve strength and reduce, at the same time, weight. In the fifties experimental tests carried out at Langley Aeronautical Laboratory of National Advisory Committee for Aeronautics (NACA) revealed that a small amount of pressure inside cylindrical components could increase strength. The first rigorous study upon this topic was performed by Lo, Crate and Schwartz [3]. From the comparison of experimental tests and analytical studies, they demonstrated that internal pressure can positively influence the resistance of cylindrical structures under torsional and compressive loads. Later some studies were carried out on specific cases, like silos and pipes, and Mathon and Limam [4] showed that the effects of internal pressure on closed cylinders under pure bending are dependent on the geometry and, particularly, on the ratio radius/thickness (R/t) and length/radius (L/R). Other studies [5] presented the effects on composite structures with different loads and with or without internal pressure. In this work, the effects of internal pressure on closed cylinders subjected to different loads were ® numerically investigated. Internal pressure was created throughout the use of LS-DYNA 971 airbag models and increasing levels of pressure were tested to evaluate the effect on the analyzed structure. Several FE models of different cylindrical geometries and loads were created and a comparison between metals and composite materials was numerically performed. A focused research on an innovative shape, that can take advantages from this kind of application, was also performed and its results compared with previous model ones.

  • Aircraft Engine Blade-Out Dynamics

    Kelly S. Carney, Charles Lawrence, Dorothy V. Carney - NASA Glenn Research Center

    A primary problem in the design of aircraft gas turbine engine internal and support structures is the accurate simulation of the fan blade-out event and the subsequent windmilling of the engine. Reliable simulations of the blade-out event are required to ensure structural integrity during flight as well as to guarantee successful blade-out certification testing. A model and procedure has been developed which successfully predicts the key physical behavior of a generic engine structural dynamics. The key procedures and modeling techniques for this application are given.

  • Aircraft NPP Impact Simulation Methodology

    Yu.V. Novozhilov (CADFEM CIS JSC), A.N. Dmitriev, D.S. Mikhaluk (CEPSA JSC), N.A Chernukha, L.Yu. Feoktistova ((ATOMPROECT JSC), I.A. Volkodav (SEC DDC JSC)

    The IAEA safety requirements imply that the design of nuclear power plants (NPP) considers both the potential technological disaster and acts of nature. One of the modern mandatory requirements of IAEA standard SRS 87 is to consider a possible massive commercial airplane crashing (APC) into or attacking NPP reinforced concrete (RC) structures. The basis for the methodology is well-validated RC structures modeling. LS-DYNA® constitutive models have been tested by solving a set of verification problems. Selected problems set describes different loading conditions and scales: single finite element study, quasi-static loading, low-speed impact, deformable missile impact, RC wall APC load, shock wave load, perforation by a kinetic missile. The following model parameters are examined: mesh convergence, contact algorithms work, immersed reinforcement coupling, nonlinear stability. The second part of the paper presents a universal method of APC events direct modeling based on the finite element method in the Euler formulation. The relations allowing to identify geometrical, strength, and mass parameters of the airplane finite element model by the given load curve and impact spot are developed. The model of the aircraft obtained in this way allows the transfer of loads on complex-shaped civil structures or when considering the impact at an angle to the surface, with great fidelity. The last part describes the simulation results processing and analysis procedure. Criteria for determining the strength based on the analysis of displacement, strain, and damage of both concrete and reinforcements are proposed. Approach to the evaluation of penetration, perforation, and fracture speed behind the barrier estimation is developed.

  • Aircraft Seat Row-to-row Head Injury Criteria (HIC) Simulation Using LS-DYNA®

    E-June Chen, PhD, Boeing Commercial, Seattle, Washington

    Successful aircraft seat row-to-row HIC certification takes many test iterations and therefore is time intensive. Both developmental and certification tests are repeated to account for customized seat pitches, the range of occupant seated heights (from 5th percentile female to 95th percentile male), and several required impact zones. Row-to-row HIC prediction using simulation can help early design concept development (e.g., evaluating energy absorption devices and breakover mechanisms), and in turn reduce the cost of testing and the associated lead time. The objective of this paper is to introduce row-to-row HIC analysis and prediction using LS-DYNA. The seat modeling techniques for the row-to-row simulation were summarized. Two cases were used to demonstrate HIC predictability using simulation.

  • Airdrop Sequence Simulation using LS-DYNA® ICFD Solver and FSI Coupling

    Morgan Le Garrec, Matthieu Seulin, Vincent Lapoujade, DynaS+, Toulouse, France

    In this framework, the payload freefall is considered for the present paper, from the airplane cargo bay up until the initiation of parachute deployment. The LS-DYNA simulations include multi-physics and fluid-structure interaction coupling. The currently developed ICFD solver is used in conjunction with the non-linear dynamic structural solver.

  • ALE Adaptive Mesh Refinement in LS-DYNA

    N. Aquelet (LSTC)

    An adaptive mesh refinement capability was implemented in the 3D MMALE (Multi-Material Arbitrary Lagrange Euler) code. It automatically and locally refines (or coarsens) ALE hexahedral solid elements. The keyword *REFINE_ALE (or *ALE_REFINE) activating this feature has 3 lines of parameters that enable 3 different kinds of refinement. If the keyword has only one line, the refinement is static and only occurs during the initialization. If the second line is added, the refinement becomes dynamic. Adding the third line allows removing refined meshes.

  • ALE and Fluid Structure Interaction in LS-DYNA

    M. Souli - Laboratoire de Mécanique de Lille, J. Wang, I. Do, C. Hao - Livermore Software Technology Corporation

    Fluid-structure interactions play an important role in many different types of real-world situations and industrial applications involving large structural deformation and material or geometric nonlinearities. Numerical problems due to element distortions limit the applicability of a Lagrangian description of motion when modeling large deformation processes. An alternative technique is the multi-material Eulerian formulation for which the material flows through a mesh, fixed in space and each element is allowed to contain a mixture of different materials. The method completely avoids element distortions. With an Eulerian-Lagrangian (fluid-structure) coupling algorithm, Eulerian parts may interact with Lagrangian parts in the same model. The Eulerian method is limited by dissipation and dispersion problems associated with the fluxing of mass across element boundaries. In addition, the Eulerian mesh must span the whole active space covering all Lagrangian structures and the spatial range of their motions. This requires a large mesh and thus high computing cost. The multi-material arbitrary Lagrangian-Eulerian (MMALE) method improves upon pure Eulerian formulation by allowing the reference fluid mesh(es) to translate, rotate and deform, thus minimize the amount of flux transport, and reduce mesh size of the reference fluid mesh(es).

  • ALE AND FLUID-STRUCTURE INTERACTION IN LS-DYNA

    M’hamed Souli - Université des Sciences de Lille et Technologie

    A new Eulerian-Lagrangian coupling algorithm and improved multi-material ALE-capabilities have made LS- DYNA an efficient tool for analyzing large deformation processes, such as bird strike events and forging operations. This paper contains two example problems that illustrate the current features of the code.

  • ALE and Fluid-Structure Interaction Capabilities in LS-DYNA

    M’hamed Souli - Universite des Sciences et Technologie de Lille, Lars Olovsson, Ian Do - Livermore Software Technology Corporation

    A new Eulerian-Lagrangian coupling algorithm and improved multi-material ALE-capabilities have made LS-DYNA an efficient tool for analyzing large deformation processes, such as bird strike events, forging operations and penetration problems. This paper contains four example problems that illustrate the current features of the code.

  • ALE and Fluid-Structure Interaction Capabilities in LS-DYNA

    Lars Olovsson - Livermore Software Technology Corporation, M’hamed Souli - Universite d’Artois

    A new Eulerian-Lagrangian coupling algorithm and improved multi-material ALE- capabilities have made LS-DYNA an efficient tool for analyzing large deformation processes, such as bird strike events and forging operations. This paper contains two example problems that illustrate the current features of the code.

  • ALE Formulation for the Evaluation of Seismic Behaviour of Anchored and Unanchored Tanks

    Z. Ozdemir - Bogazici University / Université de Lille, M. Souli - Université de Lille, Y. Fahjan - Gebze Institute of Technology

    Estimation of the potential degree of risk for tank failure during an earthquake is very difficult to quantify since the liquid-tank system possesses many different nonlinear behaviour mechanisms which may be triggered simultaneously or separately depending on the characteristics of earthquake, contained liquid properties, fluid depth, dimensions of the tank, roof type, material properties, supporting conditions and stiffness of underlying soil medium. These nonlinear behaviour mechanisms can emerge in the form of elephant foot and diamond shape buckling at the tank wall, rupture at the junction between tank wall and base, buckling at the top of tank and roof, settlement at tank support system and foundation and large amplitude deformations at the base plate. For the case of unanchored tank, in addition to these mechanisms, uplift of tank base, sliding of the tank and successive contact and separation between base plate and foundation can be observed when tank subjects to seismic loadings. The analysis tool used to quantify the tank behaviour has to take into account the effects of all aforementioned factors. Since LS-DYNA is capable of handling complexities associated with the nonlinear transient seismic response of unanchored tanks it is utilized in this study. ALE technique and contact algorithms of LS-DYNA are used to model the coupling of tank and fluid and the interaction between tank base and soil, respectively. The results are compared with the provisions given in tank seismic design codes used in the current practice.

  • ALE Formulation for the Evaluation of Seismic Behaviour of Anchored and Unanchored Tanks

    Z. Ozdemir - Bogazici University / Université de Lille, M. Souli - Université de Lille, Y. Fahjan - Gebze Institute of Technology

    Estimation of the potential degree of risk for tank failure during an earthquake is very difficult to quantify since the liquid-tank system possesses many different nonlinear behaviour mechanisms which may be triggered simultaneously or separately depending on the characteristics of earthquake, contained liquid properties, fluid depth, dimensions of the tank, roof type, material properties, supporting conditions and stiffness of underlying soil medium. These nonlinear behaviour mechanisms can emerge in the form of elephant foot and diamond shape buckling at the tank wall, rupture at the junction between tank wall and base, buckling at the top of tank and roof, settlement at tank support system and foundation and large amplitude deformations at the base plate. For the case of unanchored tank, in addition to these mechanisms, uplift of tank base, sliding of the tank and successive contact and separation between base plate and foundation can be observed when tank subjects to seismic loadings. The analysis tool used to quantify the tank behaviour has to take into account the effects of all aforementioned factors. Since LS-DYNA is capable of handling complexities associated with the nonlinear transient seismic response of unanchored tanks it is utilized in this study. ALE technique and contact algorithms of LS-DYNA are used to model the coupling of tank and fluid and the interaction between tank base and soil, respectively. The results are compared with the provisions given in tank seismic design codes used in the current practice.

  • ALE Incompressible Fluid in LS-DYNA

    Nicolas Aquelet - LSTC Livermore, Mhamed Souli - University of Lille

    The computation of fluid forces acting on a rigid or deformable structure constitutes a major problem in fluid- structure interaction. However, the majority of numerical tests consists in using two different codes to separately solve pressure of the fluid and structural displacements. In this paper, a monolithic with an ALE formulation approach is used to implicitly calculate the pressure of an incompressible fluid applied to the structure. The projection method proposed by Gresho is used to decouple the velocity and pressure

  • ALE Incompressible Fluid in LS-DYNA

    Nicolas Aquelet, Mhamed Souli (LSTC)

    The computation of fluid forces acting on a rigid or deformable structure constitutes a major problem in fluid-structure interaction. However, the majority of numerical tests consists in using two different codes to separately solve pressure of the fluid and structural displacements. In this paper, a monolithic with an ALE formulation approach is used to implicitly calculate the pressure of an incompressible fluid applied to the structure. The projection method proposed by Gresho is used to decouple the velocity and pressure.

  • ALE Incompressible Fluid in LS-DYNA

    N. Aquelet, M. Souli (LSTC)

    The computation of fluid forces acting on a rigid or deformable structure constitutes a major problem in fluid- structure interaction. However, the majority of numerical tests consists in using two different codes to separately solve pressure of the fluid and structural displacements. In this paper, a monolithic with an ALE formulation approach is used to implicitly calculate the pressure of an incompressible fluid applied to the structure. The projection method proposed by Gresho is used to decouple the velocity and pressure

  • ALE Incompressible Fluid in LS-DYNA

    Mhamed Souli - University of Lille

    The computation of fluid forces acting on a rigid or deformable structure constitutes a major problem in fluid- structure interaction. However, the majority of numerical tests consists in using two different codes to separately solve pressure of the fluid and structural displacements. In this paper, a monolithic with an ALE formulation approach is used to implicitly calculate the pressure of an incompressible fluid applied to the structure. The projection method proposed by Gresho is used to decouple the velocity and pressure

  • ALE Modeling of Explosive Detonation on or near Reinforced-Concrete Columns

    J. M. H. Puryear, D. J. Stevens, K. A. Marchand (Protection Engineering Consultants), E. B. Williamson (University of Texas), C. K. Crane (USACE Engineer Research and Dev. Center)

    The detonation of explosive threats in contact with or near reinforced concrete columns was modeled using the Arbitrary Langrangian-Eulerian (ALE) capability of LS-DYNA, in support of the development of a software tool for assessing the vulnerability of structures subjected to terrorist attack. The explosive, air, and concrete were modeled as fluids, and the reinforcement was modeled using beam elements. *MAT_72R3 was used for the concrete, and column damage was characterized using the scaled damage measure, an output from the constitutive model that quantifies damage to the material. The model was initially validated against a large database relating spall and breach thresholds of reinforced concrete slabs to charge weight and standoff. It was further validated against a small database for explosive loading against reinforced concrete columns. A parameter study was then performed to populate a results space comprising four column shapes over a representative ra nge of dimensions. This results space was used to develop a fast-running algorithm that will be implemented in the structural vulnerability assessment software.

  • ALE Modeling of Surface Waves

    AQUELET Nicolas - Livermore Software Technology Corporation

    An Arbitrary Lagrange Euler formulation for the propagation of surface waves is developed in LS-DYNA®. The ALE computational time step in this code is divided in two cycles: a Lagrangian cycle in which the mesh follows the material deformation and an advection cycle in which the users through remapping algorithms control the mesh motion. The new feature presented in this paper is one of these remapping algorithms. It enables a Lagrangian behavior of free ALE mesh boundaries whereas, in the direction of the wave propagation, the ALE mesh is Eulerian to avoid distortions. Nodes on the ALE mesh borders moves with the surface waves during the Lagrangian cycle. During the advection cycle, the remap positions of these nodes are computed by interpolating the Lagrangian positions of their neighbors with biquadratic polynomials. If the wave amplitudes are too important, ALE smoothing can be used for the internal nodes and a specific smoothing is applied on the mesh surfaces.

  • ALE/FSI AirBlast Modeling: On the Way to One Billion Elements

    The Arbitrarian Lagrangian Eulerian (ALE) method of LS-DYNA® software is the best actual solution to perform AirBlast simulation. Indeed, thanks to its coupling method (ALE/FSI), it allows to the user to model complex blast waves interaction with Lagrangian structures. Today, due to hardware advances (the computer power highly increased) and LS-DYNA technology enhancement (ALE Mapping, MPP), it becomes possible to consider models with a very large volume of air, while keeping a good accuracy with a small element size. These new possibilities lead to a quantity of elements never reached before, for which LS-DYNA and LS-PrePost® had to adapt. In this paper, based on work realized with the help of LSTC, we will explain what exactly are the issues of modeling an ALE/FSI model with more than 100 million elements and what solutions were found. We will present some facilities to pre-process such a big model, like the new LS-PrePost “Long Format” or an innovative way to create ALE mesh using a new LS-DYNA keyword. We will also discuss about other important points concerning MPP decomposition, memory needs and post- processing, in order to give LS-DYNA users a complete overview of the ins and outs.

  • Alternative Models of the Offset and Side Impact Deformable Barriers

    Dr. Tore Tryland - Hydro Automotive Structures

    The deformable barriers consist mainly of honeycomb blocks with highly anisotropic behaviour. These parts are made from several layers with aluminium foil that is glued and stretched to form the honeycomb structure. Simple compression tests show high stiffness and strength when the cell structure is folded while both stiffness and strength are significantly lower when the deformation mode is mainly bending of the thin foil. Remember that the typical deformation mode involve also transverse displacement of barrier parts, and when the honeycomb structure is folded this may be seen as the interaction between local and global buckling. Therefore, shell elements are used to model the honeycomb structure, and alternative models of the offset and the side impact deformable barriers are made. Note that scaling is used extensively to limit the number of elements and thereby the computational time that is required. These models with about 30 000 shell elements seem able to predict the global response of the deformable barriers, and they may be easily refined to represent more local behaviour as well.

  • ALUMINUM PLATE PERFORATION: A COMPARATIVE CASE STUDY USING LAGRANGE with EROSION, MULTI-MATERIAL ALE, and SMOOTH PARTICLE HYDRODYNAMICS

    Leonard E Schwer - Schwer Engineering & Consulting Services

    The focus of the present work is to perform an assessment of a relatively new class of numerical methods, referred to as meshfree methods, that offer analysts an alternate analytical technique for simulating this class of ballistic problems, without a priori trajectory knowledge, nor resorting to ad hoc criteria. The assessment is made by the comparison of projectile residual speeds provided by the various techniques, when used to simulate a ballistic impact experiment. The techniques compared are the meshfree method known as Smooth Particle Hydrodynamics, a Multi-Material Arbitrary Lagrange Eulerian (MM-ALE) technique, and Lagrangian with material erosion. Such comparisons inherently have aspects of an apples-to-oranges-to-pears comparison, but an effort has been made to minimize the numerous ancillary aspects of the different simulations and focus on the capability of the techniques. To minimize unintended differences in the simulations, the following three key aspects remain constant: 1. Only one software package (code) is used, 2. The same constitutive model is used, 3. The models were constructed by one analyst with a similar level of experience using the three modeling techniques. Even with these considerable constraints on the simulation comparisons, it is obvious that the results are subject to the analyst’s knowledge and skills in applying the various analysis techniques to the impact simulation. Thus the reader should not assess the merits of these techniques on the provided ‘answers,’ but should instead focus on the relative merits of each technique and their applicability to simulations of interest.

  • ALUMINUM PLATE PERFORATION: A COMPARATIVE CASE STUDY USING LAGRANGE with EROSION, MULTI-MATERIAL ALE, and SMOOTH PARTICLE HYDRODYNAMICS

    Leonard E Schwer - Schwer Engineering & Consulting Services

    The focus of the present work is to perform an assessment of a relatively new class of numerical methods, referred to as meshfree methods, that offer analysts an alternate analytical technique for simulating this class of ballistic problems, without a priori trajectory knowledge, nor resorting to ad hoc criteria. The assessment is made by the comparison of projectile residual speeds provided by the various techniques, when used to simulate a ballistic impact experiment. The techniques compared are the meshfree method known as Smooth Particle Hydrodynamics, a Multi-Material Arbitrary Lagrange Eulerian (MM-ALE) technique, and Lagrangian with material erosion. Such comparisons inherently have aspects of an apples-to-oranges-to-pears comparison, but an effort has been made to minimize the numerous ancillary aspects of the different simulations and focus on the capability of the techniques. To minimize unintended differences in the simulations, the following three key aspects remain constant: 1. Only one software package (code) is used, 2. The same constitutive model is used, 3. The models were constructed by one analyst with a similar level of experience using the three modeling techniques. Even with these considerable constraints on the simulation comparisons, it is obvious that the results are subject to the analyst’s knowledge and skills in applying the various analysis techniques to the impact simulation. Thus the reader should not assess the merits of these techniques on the provided ‘answers,’ but should instead focus on the relative merits of each technique and their applicability to simulations of interest.

  • An Adaptive Meshfree Galerkin Method for the Three-dimensional Thermo-mechanical Flow Simulation of Friction Stir Welding Process

    C.T. Wu, W. Hu (LSTC), H.P. Wang (GM Research and Development Center)

    In this paper, new numerical modeling of material flow in the thermo-mechanical friction stir welding process is presented. In this numerical model, the discretization in space is derived by the meshfree Galerkin method using a Lagrangian meshfree convex approximation. The discrete thermal and mechanical equations are weakly coupled as the time advances using a forward difference scheme. A mortar contact algorithm is employed to model the stirring effect and heat generation due to frictional contact. Heat conductance between contacting bodies is considered as a function of contact pressure. A two-way adaptive procedure is introduced to the coupled thermo-mechanical system to surpass potential numerical problems associated with the extensive material deformation and spatial discretization. In each adaptive phase, a consistent projection operation utilizing the first-order meshfree convex approximation is performed to remap the solution variables. Finally, a three-dimensional thermo-mechanical coupled friction stir welding problem is analyzed to demonstrate the effectiveness of the present formulation.

  • An Adaptive Thick Shell Element for Crashworthiness Assessment of Laminated Composites

    Johannes Främby, Martin Fagerström (Chalmers University of Technology), Jesper Karlsson (DYNAmore Nordic AB)

    The automotive industry is strongly dependent on efficient numerical tools in order to assess the crashworthiness of laminated composites. Unfortunately, to achieve predictive assessments of fracture in laminated composites one must resort to computationally costly, high-fidelity layered models, which in practice makes full vehicle crash simulations very difficult (or even impossible). One solution to this is to use an adaptive modelling technique where an initially coarse model is automatically refined, when and where needed, during the analysis. In this context, we have developed an LS-DYNA® user element which can be adaptively refined through the thickness to allow for both so-called weak discontinuities (discontinuities in strain at material interfaces) and strong discontinuities (discontinuities in displacements, i.e. delamination cracks). Furthermore, we have proposed a remedy to the numerical instabilities which arise from using adaptive refinement in a dynamic explicit solver. This adaptive element proves capable of reproducing the result of high-fidelity models, although at a lower computational cost.

  • An Advanced Identification Procedure for Material Model Parameters based on Image Analysis

    L. Peroni, M. Scapin, C. Fichera (Politecnico di Torino)

    Inverse methods for the material strength model calibration are widespread techniques, which allow taking into account for the actual strain, strain-rate, temperature and triaxiality fields inside the specimen. An optimization procedure generally starts from experimental measurement of force-stroke time history and is based on the minimization of the difference between experimental and numerically computed quantities. In this work, the strength model identification is performed also on the basis of the specimen shape recorded during the test. This information is imposed as boundary condition, which forces the experimental profile to the external surface of the specimen.

  • An airbag application for the ALAR incidences for the Passenger Aircrafts

    Vailore Anandan

    The airbag system can be designed to reduce the damage on the fuselage during an Approach and Landing Accident Reduction (ALAR) situations as well as ditching in the water for the transcontinental flights. Minimum hull damage protects the passengers in deep waters. A preliminary investigation for this end is performed in this paper. A simple model under 10000 elements is used to investigate the problem. The findings of the LS-DYNA finite element simulation are reported in this paper. It also shows a filtering effect on the impact pulse on the structure. The spikes on the deceleration pulse can create injury to the occupants. The airbag filters the pulse thus reducing various injuries to the occupant apart from hull protection. The most useful feature is its automatic deployment at the most critical moment. This is also useful for the small and mid-size aircrafts to survive various ALAR incidences. It saves life as well as property in case of the small crafts.

  • An Analysis of the Hot-forming Process with Thermal and ICFD Simulations

    M. Kintsch, S. Szabo, R. Schneider (Voestalpine Automotive Components)

  • An Application of LS-DYNA for the New FMVSS 208 Front Impact Tests

    Charlotte Jamte, Tim Keer, Richard Maloney, Joshua Weage - Arup

    The automotive safety community is currently facing the challenge of new front impact legislation (FMVSS 208), to be introduced in the USA in 2004. Vehicles will be subjected to an increased number of and type of barrier tests. This paper describes a new technique, using LS-DYNA, to aid the vehicle development process. A virtual “sled” has been developed for analysis of the different FMVSS 208 impact scenarios. This sled model would typically be created and exercised early in the vehicle development process, before a full vehicle model can be created. The sled can incorporate the target structural response of the occupant compartment (translational and rotational accelerations; intrusion; yaw and pitch; steering column motion), the restraint systems (airbags and seat-belts) and the occupants (driver and passenger; different percentile dummies). This modular approach allows different barrier configurations (rigid; rigid angled; deformable offset), impact speeds and occupant sizes (Hybrid III 5th and 50th) to be modeled with simple changes to the input file. The benefits of this approach are the ability to obtain a preliminary assessment of vehicle compliance for a wide range of impact scenarios at a time when the vehicle package is still being determined.

  • An Approach for Modeling Shock Propagation Through a Bolted Joint Structure

    Pouya Shojaei, Mohamed Trabia, Brendan O'Toole, Jed Higdon (University of Nevada, Las Vegas)

    Impact loading is typically characterized by a relatively large load happening over an extremely short duration and inducing broad range of vibration frequencies. Standard design approaches of bolted joints based on static or quasi-static criteria may not be effective under these conditions. This study focused on simulating a drop-weight tower experiment where a free-falling mass impacted a target plate, which was bolted to a cylindrical structure. An accelerometer was used to record transmitted acceleration to the cylindrical structure. An approach for simulating the shock propagation was proposed using LS-DYNA® Explicit finite element code. To reduce computational time, thread was not included. Instead, bolts were represented as cylinders with cross-sectional areas equal to the tensile stress area of the bolts. The results showed good agreement between the finite element and experimental results.

  • An Approach to capture the Ejection Mitigation Requirements of FMVSS 226 with Finite Element Simulations

    André Haufe, George Dimitru - DYNAmore GmbH, Andreas Hirth - Daimler AG, Robert Kirchner - Friedmann & Kirchner

  • An Assessment of ALE Mapping Technique for Buried Charge Simulations

    I. Kurtoğlu (FNSS Savunma Sistemleri)

    In this work, the effects of ALE mapping technique developed by LSTC [1] are investigated for buried charge simulations. Before mapping studies, a mesh sensitivity study is performed for the pure ALE simulations to investigate the effect of 3D mesh size on the impulse. The ALE mapping is performed from a 2D axisymmetric model to full 3D model.

  • An Assessment of the LS-DYNA Hourglass Formulations via the 3D Patch Test

    Leonard E. Schwer - Schwer Engineering and Consulting Services, Samuel W. Key - FMA Development, LLC, Thomas A. Pučik - Pučik Consulting Services, Lee P. Bindeman - Livermore Software Technology Corporation

    The six hourglass formulations available in LS-DYNA for 8 node hexahedral elements are evaluated using the so called ‘3D Patch Test.’. It is demonstrated that three of the six hourglass formulations fail this patch test, including the popular default LS-DYNA viscous form of hourglass control. A detailed description of the 3D Patch Test is provided to allow readers to perform the simple test as part of their code verification.

  • An assessment of the new LS-DYNA layered solid element: basics, patch simulation and its potential for thick composite structure analysis

    Madhukar Chatiri - CADFEM GmbH, Thomas Güll - Adam Opel GmbH, Prof. Anton Matzenmiller - University of Kassel

    One major component of fuel cell vehicles is the hydrogen storage system. A promising and nowadays mostly used approach is to store hydrogen in wet wound carbon fiber reinforced plastic (CFRP) vessels manufactured by filament winding process with an operating pressure of up to 70 MPa (hereafter referred as H2 vessel). Due to the inherent complexity and 3-dimensional nature, accurate behavior of such thick composite structures in impact simulations needs an adequate representation of the composite plies. Modeling thick composite structures with 2-dimensional elements will produce inaccurate results in transverse normal direction. Thus 3D modeling should be used but to model each ply with one solid element leads to undesirably big models and is impractical for large structures. Thus representation of several plies in one solid element and more such elements across thickness is desired. Also, solid elements are needed to represent the 3-dimensional state of stress and impact direction normal to the outer vessel surface. A new layered solid element formulation is implemented in LS-DYNA® Version 971 R4 allowing the definition of multiple integration points through the thickness in combination with arbitrary material orientation. The above new element formulation is presented in this paper describing different patch simulation results and simulation results for thick composite structures such as hydrogen storage H2 vessels.

  • An assessment of the new LS-DYNA layered solid element: basics, patch simulation and its potential for thick composite structure analysis

    Madhukar Chatiri - CADFEM GmbH, Thomas Güll - Adam Opel GmbH, Prof. Anton Matzenmiller - University of Kassel

    One major component of fuel cell vehicles is the hydrogen storage system. A promising and nowadays mostly used approach is to store hydrogen in wet wound carbon fiber reinforced plastic (CFRP) vessels manufactured by filament winding process with an operating pressure of up to 70 MPa (hereafter referred as H2 vessel). Due to the inherent complexity and 3-dimensional nature, accurate behavior of such thick composite structures in impact simulations needs an adequate representation of the composite plies. Modeling thick composite structures with 2-dimensional elements will produce inaccurate results in transverse normal direction. Thus 3D modeling should be used but to model each ply with one solid element leads to undesirably big models and is impractical for large structures. Thus representation of several plies in one solid element and more such elements across thickness is desired. Also, solid elements are needed to represent the 3-dimensional state of stress and impact direction normal to the outer vessel surface. A new layered solid element formulation is implemented in LS-DYNA® Version 971 R4 allowing the definition of multiple integration points through the thickness in combination with arbitrary material orientation. The above new element formulation is presented in this paper describing different patch simulation results and simulation results for thick composite structures such as hydrogen storage H2 vessels.

  • An Assessment of the New LS-DYNA® Multi-Layered Solid Element: Basics, Patch Simulation and its Potential for Thick Composite Structural Analysis

    Thorsten Schütz - Adam Opel GmbH, Anton Matzenmiller - Univ. of Kassel, Madhukar Chatiri - CADFEM GmbH

    Limitation of fossil fuels and global warming favor the introduction of new powertrain concepts for road vehicles with highest efficiency and low greenhouse gas emissions. Fuel cell vehicles offer the highest potential for sustainable mobility in the future. One major component of fuel cell vehicles is the hydrogen storage system. A promising and currently the most-used approach is to store hydrogen in wet-wound carbon fiber reinforced plastic (CFRP) vessels manufactured by a filament winding process with an operating pressure of up to 70 MPa (hereafter referred as H2 vessel). Due to the inherent complexity and the 3-dimensional nature, accurate behavior of such thick composite structures in impact simulations needs an adequate representation of the composite plies. Modeling thick composite structures with two-dimensional elements will produce inaccurate results in transverse normal direction. Therefore, 3D modeling should be used but the idealization of each ply with one solid element leads to undesirably large models and is impractical for large structures. Hence, representation of several plies in one solid element and more such elements across the thickness is aspired. An improved multi-layered solid element showing excellent efficiency of CPU time is implemented in the code of LS-DYNA® Version 971 R4. Like any brick element, it resolves the 3D stress state necessary for impact directions normal to the outer vessel surface. The element allows the definition of multiple integration points through the thickness in order to account for stacks of plies with arbitrary fiber orientation. By defining several layers with different material properties and ply orientations inside one multi-layered solid, the number of elements through the thickness is remarkably reduced and still, the result is close to the one obtained from the detailed finite element model of one brick element per layer. As depicted in Fig.1.2, a complex laminate configuration consisting of 18 different plies with varied fiber angles is represented by one multi-layered solid element with 18 integration points through the thickness. The above new element formulation is presented in this paper describing simulation results for both, different patches and for thick composite structures such as for hydrogen storage H2 vessels.

  • An Assessment of the Robustness of the European Pedestrian Leg Impact Test Using LS-OPT and LS-DYNA

    Tim Keer - Arup

    The automotive safety community is currently facing the challenge of new pedestrian impact requirements, introduced in Europe in 2005. These requirements necessitate considerable changes to the vehicle front end (bumper system, hood and fenders). LS-DYNA models of the pedestrian impactors (head, upper leg and leg) are an important tool for analysis of the various tests that comprise the new requirements. One of the criticisms of the current tests concerns repeatability. Physical testing with the leg impactor, in particular, shows considerable scatter of results. This lack of repeatability can cause the system to be over-designed to give sufficient confidence that the vehicle will meet the pedestrian safety requirements during compliance testing. Lack of repeatability in the results from physical leg impact tests can be caused by three main groups of factors: - variations in the vehicle (e.g. build tolerances) - variations in the legform impactor (e.g. properties of the Confor foam “skin”) - variations in the test set-up (e.g. impact velocity) This paper describes an LS-OPT study designed to assess these issues. An LS-OPT Monte Carlo simulation was used to perform a series of LS-DYNA analyses and to assess the relative importance of the different factors in these groups. The results give insight into the parameters which should be controlled most tightly in order to improve the repeatability of leg impact testing. The paper concludes with a discussion of the benefits of this approach and the potential for further application.

  • An automated belt fitting tool for 6 and 10 year-old child crash dummies

    Gillian Mara, Christian Dalton (Semcon)

    Modelling child occupant safety through computer aided engineering (CAE) within a vehicle is an area that is constantly developing. In 2003, Euro NCAP introduced a child occupant protection rating to inform consumers the results of vehicle safety assessments [1]. These assessments used 18 month and 3 year old dummies in frontal and side crash. Developments in technology and crash dummies have led to the introduction of new larger child dummies in the Q series, those being the 6 and 10 year old. In 2016-18 it is proposed these will be used in frontal and side EuroNCAP consumer crash ratings, where the dummy will be sat in a child seat. In the competitive market there is a demand on manufacturers to produce cars in a shorter time frame from idea to production, therefore making the overall process more efficient and cost effective. One area that this places emphasis on is predicting how cars perform where it has the potential to reduce the need to produce as many prototype vehicles. To ensure the results are accurate the predictive method of finite element analysis (FEA) is very dependent on the inputs, where those are primarily grouped into materials, geometry and boundary conditions. In terms of the child occupant prediction this means obtaining realistic inputs to gain realistic output kinematics and injury criteria during the frontal or side crash. The belt restraint system is one of the most predominant in affecting the child kinematics and one that needs to be modelled accurately. This paper will describe an automated seat belt fitting method using the LS- DYNA® package that is efficient and effective in creating a belt geometry and path for a 6 and 10 year old dummy in a child seat.

  • An Automated Process for Interior Head Impact Analysis

    Thanassis Fokilidis, Antonis Perifanis (BETA CAE Systems SA), Anneli Hoegberg (VOLVO CAR Corporation)

    During the last decade, the Occupant Protection legislation requirements on interior safety properties of automobiles have become considerably more demanding. The US standard laboratory test procedure FMVSS201U regulates the tests for the head protection against the event of its impact on the upper interior roof. The procedure involves the identification of the most critical target zones and headform target angles. To minimize the need for physical tests, the product performance evaluations are, as far as possible, performed with numerical simulations involving CAE software. However, covering all possible load cases would require an infinite number of simulations. In order to automate the generation of input data and to assist in finding the critical load parameters, Volvo Cars Safety Centre and BETA CAE Systems employed a process that involves ANSA pre- SURFHVVRU DQG (7$ SRVW-processor, extended with special tools. This automated process starts with the model file input to ANSA and concludes with the assessment of the LS-'<1$ UHVXOWV ZLWKLQ ü ù requiring minimum human interaction. An advanced algorithm, for the automatic headform positioning, which identifies the areas where the maximum vertical angle can be reached, has been developed. The process also involves a robustness analysis for each target point, and thus reduces the uncertainty of the problem. This has been successfully deployed within Volvo Cars Safety Centre, leading to great reduction of modelling time

  • An Effective Curve Matching Metric for Parameter Identification using Partial Mapping

    Katharina Witowski - DYNAmore GmbH, Markus Feucht - Daimler AG, Nielen Stander - Livermore Software Technology Corporation

    This paper describes a new method for curve matching essential to the solution of inverse problems represented by system parameter identification. Hysteretic response curves are specifically addressed as a general class. The method is based on Partial Curve Mapping (PCM) of the experiment curve onto the computed curve. This methodology involves a curve matching metric which is computed using the volume between the test curve and the computed curve section. A number of examples are presented to demonstrate the capability. These examples represent hysteretic curves which are impossible to match without mapping.

  • An Efficient Modeling Procedure for Simulation of Dynamics of Adhesively Bonded Joints

    Anindya Deb, Indrajit Malvade (CPDM, Indian Institute of Science)

    The present study is aimed at developing a new computationally efficient modeling procedure that predicts well the nonlinear mechanical behavior of adhesively bonded joints. The approach is thought to be particularly beneficial for computationally intensive vehicle crash simulations. Two other conventional modeling approaches are considered, that is, accounting for adhesive layer between shell-based substrates/flanges with monolithic solid elements, and defining a tied contact with failure condition in lieu of the solid elements. The approach presented here and not previously reported in the literature is an enhancement of the latter technique with equivalent properties being assigned to the substrates in the overlap segment of a joint model. A semi-analytical procedure is outlined in detail for arriving at the equivalent properties of substrates by accounting for shear properties of an epoxy adhesive which is geometrically not represented in the model. It is shown that the effect of strain rate on adhesive behavior can be elegantly incorporated in the proposed equivalent property-based approach via Material Type 24 in LS-DYNA for intended applications of dynamics such as vehicle crash safety assessment. The computational efficiency and accuracy of the present approach are established by comparing results yielded by it against experimental data and detailed shell-solid modeling technique.

  • An Efficient New Sequential Strategy for Multi-Objective Optimization using LS-OPT

    N. Stander (LSTC)

    ®A new surrogate-assisted Multi-Objective Optimization algorithm has been implemented in LS-OPT . The algorithm, known as Pareto Domain Reduction, is an adaptive sampling method and an extension of the classical Domain Reduction approach (also known as SRSM). A Multidisciplinary Design Optimization (MDO) example involving a vehicle impact is used to demonstrate that the accuracy is very close to the NSGA-II “exact” method while using a small fraction of the computational effort.

  • An Efficient Shell Element Based Approach to Modeling the Impact Response of Fabrics

    Ali Shahkarami, Reza Vaziri - The University of British Columbia, Canada

    An efficient shell element based computational model is developed to capture the mechanical response of fabrics. The approach considers a single yarn crossover as the basic building block (unit-cell) of the fabric panel and uses a specially formulated shell element within LS-DYNA to capture the essential features of the membrane response of this unit-cell accounting for both geometrical and material characteristics of the yarns. The shell element so developed is used to simulate the impact response of single and multi-ply packs of Kevlar® 129 fabric. The predictions are successfully compared with the measurements obtained from instrumented ballistic impact experiments.

  • An Engineering Approach of an X-Ray Car Crash Under Reverse Small Overlap Configuration

    Y. Leost, P. Bösl, I. Butz, T. Soot, M. Kurfiß, S. Moser (Fraunhofer Institute for High-Speed Dynamics, Ernst-Mach-Institut, EMI), A. Nakata, F. Kase, T. Hashimoto, S. Shibata (Honda R&D Co., Ltd.)

    During a crash event, conventional optical measuring systems provide information about the deformation of parts that are directly visible. The new measuring method called X-Ray Car Crash (XCC) developed at Fraunhofer EMI allows accessing the crash kinematic of specific parts inside the vehicle. This method provides precious information that is currently not accessible in a crash test and allows for better comparison with FEM simulations. The present paper describes a preliminary study performed in collaboration with Honda R&D Co., Ltd. The load case under consideration is a reverse variant of the IIHS Small Overlap with integrated X-Ray technology. Fraunhofer EMI Research Crash Center aims at developing new measurement methods to investigate non-standard high-speed dynamics safety issues. Most of these specific requests are coming from car manufacturers. In order to achieve maximum test reproducibility and simplify boundary conditions, the facility is equipped with a propelled sled system on rails. Thus, it enables to perform impactor to vehicle scenarios with moving barriers up to 3000 kg by 22 m/s. The standard Small Overlap at 64 km/h belongs to the vehicle to barrier scenario and requires some preliminary computations to adapt it for the EMI Crash test facility. Special consideration was given to energy balance in order to determine the right barrier velocity and mass to achieve a similar intrusion in the car to in the standard configuration. Numerical simulations were required at each step to meet the different challenges of this study. This paper describes first the numerical assessment of the validity of the reverse scenario. FEM simulations were then used extensively for developing a special moving barrier presenting maximal structural robustness, well-balanced dynamic behavior and allowing on-sled measurement technics and braking system. Then, LS-DYNA® simulations provided necessary data to perform ray tracing simulations and thus finding the right placement for X-ray source and X-ray detector. Finally, numerical simulations played an important role for an enhanced test setup, by finding the best balance between appropriate mechanical robustness of supporting structures (so called Pit-cover) and low X-ray attenuation.

  • An Engineering Approach to Estimating Partially Saturated Soil Constitutive Properties Using LS-DYNA®

    Len Schwer, Schwer Engineering & Consulting Services, 6122 Aaron Court, Windsor, California, 95492;, Matt Barsotti, Protection Engineering Consulting, 14144 Trautwein Road Austin, Texas 78737

    Soil is perhaps the most common civil engineering material, and ironically one of the most difficult to model due to its variability. At any given site, soil samples taken at different depths and distances may show considerable variability. Even if such samples show relative uniformity, there is often the question of what happens if it rains and the soil saturation changes?

  • An Enhanced Assumed Strain (EAS) Solid Element for Nonlinear Implicit Analyses

    Fredrik Bengzon, Thomas Borrvall, DYNAmore Nordic AB;, Ushnish Basu, Livermore Software Technology Corporation (LSTC)

    Historically, the importance of computational efficiency in explicit analysis has driven the element development in LS-DYNA® [1,2] towards fast and sufficiently accurate formulations. Single point integrated elements with stabilization are well established techniques in this area. The recent growth of implicit analysis has led to a demand of increased accuracy of the element response, and consequently more sophisticated formulations have been introduced in recent years. While high order elements provide a better response, low order elements remain popular due to their simplicity and robustness. An area that has not yet been exploited in LS-DYNA is the family of enhanced assumed strain (EAS) elements, the reason being the computational cost associated with this approach. Solid element 18 is a linear Wilson element based on this technology, but is only available for linear implicit analysis. The goal with this paper is to generalize this to fully nonlinear implicit analysis, and provide information on its merits and drawbacks.

  • An Enhanced Bond Model for Discrete Element Method for Heterogeneous Materials

    Zhidong Han, Hailong Teng and Jason Wang (LSTC)

    The enhanced bond model allows the Discrete Element Method (DEM) to simulate the heterogeneity and discontinuity at the individual particle level at the micro level. The traditional material models at the macro level are applied to each particle independently. This bond model bridges the behaviors of particles at macro and micro levels, and may be used for failure analysis of the homogeneous & heterogeneous materials, including composites, concretes.

  • An enhanced Design exploration using Modal decomposition of Key events in Frontal crash simulation

    M. Okamura, H. Oda (JSOL)

    In recent years, CAE has been used extensively in vehicle development, and parameter study of sheet metal thickness for design exploration and optimization is one of the major applications. Response surface method is commonly used for this application among various analysis tools. The concept is to connect input variables such as sheet metal thickness and output variables such as firewall intrusion with non-linear functions such as radial base, kriging, and neural network.

  • An Enhancement of LS-DYNA® XFEM Shells for Dynamic Ductile Failure Analysis

    Y. Guo, C. T. Wu, W. Hu, Livermore Software Technology Corporation (LSTC), Livermore, CA 94551, USA;, K. Takada, H. Okada, utomobile R&D Center, Honda R&D Co., Ltd, Tochigi, 321-3393 Japan;, N. Ma, Center of Computational Welding Science (CCWS), Osaka University, Osaka, 567-0047 Japan;, K. Saito, Engineering Technology Division, JSOL Corporation, Tokyo, 104-0053, Japan

    This paper presents an enhancement of LS-DYNA XFEM shell method [30] for dynamic ductile failure in shell structures. The XFEM shell formulation adopts the finite element continuous-discontinuous approach. The continuum damage model based on continuous displacements is used in the continuous stage to describe the diffuse micro-cracking in ductile failure before a macro-crack is formed. In the context of first-order shear deformable shell finite element method, a nonlocal modelling procedure based on a projection of mid-plane reference surface is introduced to regularize the element-wise strain fields induced by the continuum damage model. In the discontinuous stage, an incorporation of velocity discontinuities in shell finite elements is pursued by XFEM method when the damage variable exceeds a critical value and the transition from a continuous to a discontinuous model is permitted. A phantom-node approach [17] is employed in XFEM method to simplify the numerical treatment of velocity discontinuities in the shell finite element formulation. Several numerical benchmarks are examined using the explicit dynamics analysis and the results are compared with the experimental data to demonstrate the effectiveness and accuracy of the numerical method.

  • An Eulerian Finite Element Model of the Metal Cutting Process

    A. Raczy, W. J. Altenhof, A. T. Alpas - University of Windsor

    The Eulerian element formulation was employed in the modeling of the orthogonal metal cutting process of commercial purity copper. The constitutive material models elastic-plastic hydrodynamic and Johnson-Cook, were utilized in modeling the workpiece behavior. The capabilities of each model to replicate the experimental chip geometry, stress and strain distributions, and cutting forces, were investigated. The numerical strain distributions, were in good agreement with the experimental strain distribution. The maximum strains of ε p = 8.3 and ε p = 5.6 for the Johnson-Cook material and hydrodynamic material, respectively, occurred in the tool tip region, and were in good correlation with the experimental strain of ε p = 8.1 at this location. The experimental and numerical distributions, all predicted strains of approximately ε p = 3.5 to 3.6 beneath the machined surface and adjacent to the rake face. The stress distributions in both of the investigated materials were noticeable different. The Johnson-Cook model showed a stress increase of up to 425 MPa in the primary deformation zone, while the hydrodynamic model predicted increased stresses of 380 MPa in the secondary deformation zone. The hydrodynamic stress distribution was more consistent with experimental findings, which similarly showed a stress increase, up to 360 MPa, in the secondary deformation zone. The maximum stress in the hydrodynamic material (410 MPa) and in the Johnson-Cook material (438 MPa) were located at the tool tip, and showed good correlation to the maximum experimental stress of 422 MPa, also occurring at the tool tip. The sizes of both the primary deformation zone (350 μm), and the secondary deformation zone (50 μm) predicted by the hydrodynamic and Johnson-Cook material models were in agreement with the experimental observations. The steady state cutting force prediction of the hydrodynamic material was 1332 N, and was within 13% of the experimental findings. The numerical–experimental correlations indicate the Eulerian finite element approach is an effective way of modeling the metal cutting process.

  • An Evaluation of Active Knee Bolsters

    Zane Z. Yang - Delphi Corporation

    In the present paper, the impact between an active knee bolster system and occupant knees has been studied using finite element analysis. The active knee bolster system consisted of an inflatable molding part and a pair of EA supporting brackets. Also included in the FEA model was the entire vehicle cockpit. Both driver-side and passenger- side occupants were considered. The active knee bolster FEA model was first validated by test data including kinematics and femur loads. The performance of active knee bolsters was then compared with that of conventional structural knee bolsters

  • An Experimental and Numerical Investigation on Vulcanized Fiber

    K. Bayram, M. Pfeiffer, C. Alter, Prof. S. Kolling (THM)

    As the automotive industry and its companies start to look for sustainability, materials made of natural fibers receive a growing interest. In the present work, the mechanical properties of a vulcanized fiber material were investigated to understand the orthotropic and rate-dependent material behavior and make it more predictable and thus practicable. *MAT_PAPER was used to represent the anisotropic elastic-plastic behavior of the material for crash and impact simulations. To confirm numerical results from explicit FEM calculations, a user material subroutine comparable to *MAT_PAPER was utilized. Therefore, it was possible to perform implicit calculations of the conducted validation experiments which were performed at low strain rates.

  • AN EXPERIMENTAL AND NUMERICAL STUDY ON THE ENERGY ABSORBING CAPABILITY OF ALUMINUM EXTRUSIONS UNDER OBLIQUE LOADING

    A. Reyes, M. Langseth, O. S. Hopperstad - Structural Impact Laboratory

    Oblique loading was studied through static experiments and numerical simulations. The behavior of square aluminum columns in alloy AA6060 subjected to oblique loading was investigated experimentally for three different load angles. The square columns were clamped at one end and oblique load conditions were realized by applying a force with different angles to the centerline of the column. Numerical simulations were later carried out to validate the numerical model.

  • An Implicit Incompressible CFD Solver in LS-DYNA for Fluid-Structure Interaction Problems

    Facundo Del Pin - Livermore Software Technology Corporation

    The present work is an introduction to a new CFD solver in LS-DYNA®. This solver is part of the efforts put in LS- DYNA with the objective to expand the capabilities into new challenging problems in industry. The new CFD solver will focus on fluid-structure interaction (FSI) applications where incompressible fluids interact with the existing structures in LS-DYNA. Incompressible flows are present in a great variety of industrial applications from sloshing problems to aerodynamics at low Mach numbers. This new incompressible CFD solver coupled to LS-DYNA mechanics will provide an implicit time integration scheme allowing larger time steps and faster convergence to steady state. One of the main features of the solver is the Lagrangian representations of all FSI interfaces providing exact imposition of boundary conditions. In this way the fluid mesh and the solid mesh are tightly coupled such that the fluid domain deforms following the Lagrangian structure displacements. The rest of the domain follows an Arbitrary Lagrangian-Eulerian formulation. The image bellow shows the mesh movement and the conformity of the fluid mesh to the solid mesh.

  • An Implicit Study of High Order Elements in LS-DYNA

    T. Borrvall (DYNAmore Nordic); Prof. D. Benson, H. Teng (LSTC)

    An overall trend in simulation technology is towards increasing the accuracy of model features to yield a more rapid convergence with mesh refinement. In the context of element technology, migrating from shells to solids or from low to high order elements are possible ways to accomplish this. High order elements are therefore of particular importance in implicit analysis, where spatial discretization is limited by algorithmic complexity and memory consumption. Sometimes simulation standards and company regulations even make quadratic elements mandatory, and by tradition they are an important contribution to an implicit finite element software. LS-DYNA is a strong player on the implicit market and today offers a complete set of quadratic shell and solid elements. The intent with the present paper is to give an overview of the implicit capabilities of these elements, including reports on accuracy and convergence, in fairly standard simulation examples. Below some implicit deep drawing examples using high order shells (left) and solids (right) are shown.

  • An Improved 3D Adaptive EFG Method for Forging and Extrusion Analysis with Thermal Coupling in LS-DYNA

    Hongshneg Lu - Shanghai Hengstar Technology Co. Ltd., C. T. Wu - Livermore Software Technology Corporation

    The 3D adaptive EFG method using conventional moving least-square approximation or fast transformation method [1] has been successfully applied to metal forging and extrusion analysis thanks to its high accuracy in dealing with large material deformation [2] in LS-DYNA. Recently, a meshfree convex approximation [3-5] was developed to be an alternative in the large deformation analysis. However, its application to the adaptive method has not been investigated. In this paper, an improved version of 3D adaptive EFG method with emphasizing on the modified maximum entropy approximation, whose approximation is non-negative and owns Korncker-Delta propriety at the boundary, is presented. The thermal effect in forging and extrusion problem is considered, and a scheme to interpolate the thermal state variables during the adaptive procedure is proposed.

  • An Integrated Modeling Scheme for Sensor Embedded Woven Composite Structures in Manufacturing Simulation

    T. Usta, C. Liebold (DYNAmore), M. Vinot (DLR)

    This work focuses on an integrated modeling scheme of a sensor embedded woven composite structure which is created for the joint project “Digitaler Fingerabdruck” (DFA) or in English: “Digital Fingerprint” within the research campus ARENA2036 [4]. The process chain includes a draping simulation of a woven fabric and a trimming simulation using LS-DYNA®, optimization of a tailored-fiber placement process on top of this woven fabric structure using Optistruct®, fiber direction mapping from weaving simulation results using beam elements to shell element target meshes and handling of reinforcing patches using the mapping tool Envyo® [5]. The final goal is to establish an integrated process chain with parametrized variables using LS-OPT® for robustness analysis. A new feature of *MAT_REINFORCED_THERMOPLASTIC (*MAT_249) is also demonstrated to introduce fiber directions as an integration point history variable in global coordinate system to the subsequent simulations [7].

  • An Integrated Process for Occupant Safety Simulations with LS-DYNA & MADYMO Coupling

    Cédric Canadas, Tom Van Langenhove, Christophe Liefooghe - LMS International, Paul van Catz, Peter Ritmeijer - TASS

    This paper presents an innovative integrated process to perform occupant safety simulation with LS-Dyna & Madymo coupling. More than ever before, the automotive industry operates in a highly competitive environment. Manufacturers must deal with competitive pressure and with conflicting demands from customers and regulatory bodies regarding the vehicle functional performance, which forces them to develop products of increasing quality in even shorter time. To address these challenges and deliver optimal collaboration between design and engineering, the integration between CAD and CAE is key. Through a strong link between CAD and CAE, along with the integration of all simulation steps in one environment, new methodologies are developed, allowing the full utilization of parametric geometry based analysis, enabling quick “what if” scenarios simulation, and thus front-loading design with simulation. Complex CAD based assembly is fully automated, reducing the risk of modeling mistakes. Moreover, repetitive tasks such as definition of the model symmetry, are performed automatically. These functionalities allow crash engineers to focus on the impact/safety simulations set up and not on the model construction. LMS Virtual.Lab is fully integrated with Dassault System CATIA V5, therefore seamlessly linking CAD with CAE. In the field of occupant safety, Virtual.Lab pushes the integration a step forward through the support of Madymo Coupling Assistant. Tedious dummy positioning and coupling contact creation becomes straightforward with the visualization of the Madymo dummy in its LS-Dyna FE model environment. A real life industrial case is presented consisting of a CAD based assembly of a door sub-system is performed automatically through automation, and then integrated within a quarter body in white. A Madymo dummy is then positioned wrt the vehicle model, allowing to define coupling simulation of a side impact with LS-DYNA and MADYMO solvers. Back to back comparison of traditional CAE and the proposed new methodology is highlighted to provide a measure of the savings that can be realized.

  • An Interprocess Communication based Integration of AI User Materials into LS-DYNA

    Joachim Sprave, Tobias Erhart, Andr´e Haufe

    Machine Learning (ML) driven material models have been investigated for some time now. The respective ML models can be trained outside of the Finite Element solvers by means of given strain paths and corresponding stress results which have either been recorded from simulations, drawn from distributions, or even measured from hardware tests. The trained models can be easily evaluated regarding their performance based on an-other set of strain paths with results that have not been presented to the model during training. When a model has reached a promising prediction accuracy on the validation data, the natural next step is to test it in a finite element simulation by integrating the trained model as a user material.

  • An Introduction to the LS-DYNA® Smoothed Particle Galerkin Method for Severe Deformation and Failure Analyses in Solids

    C. T. Wu, Y. Guo, W. Hu (LSTC)

    This paper presents a new particle method in LS-DYNA for the severe deformation and failure analyses of solid mechanics problems. The new formulation is first established following a standard meshfree Galerkin approach for a solving of the partial differential equation of a linear elastic problem. A smoothed displacement field is introduced to the Galerkin formulation and leads to a regularized smoothed strain approximation. The resultant smoothed/regularized strain formulation can be related to the residual-based stabilization method for the elimination of zero-energy modes in the conventional particle methods. The discretized system of equations are consistently derived within the meshfree Galerkin variational framework and integrated using a direct nodal integration scheme. The linear formulation is next extended to the large deformation and failure analyses of inelastic materials. In the severe deformation range, adaptive Lagrangian or Eulerian kernel approach can be preformed to reset the reference configuration and maintain the injective deformation mapping at the particles. Several numerical benchmarks are provided to demonstrate the effectiveness and accuracy of the proposed method.

  • An inverse approach for material parameter identification in a cyclic bending test using LS-DYNA and LS-OPT

    Per-Anders Eggertsen - Chalmers University of Technology, Kjell Mattiasson - Chalmers University of Technology / Volvo Cars Safety Centre

    The residual stresses in the blank after forming are the main cause for the subsequent springback in a sheet forming operation. The accuracy of the predicted springback in a Finite Element simulation of the forming operation is very much determined by the quality of the material modeling. Those parts of the workpiece, which in particular contribute to the global springback, have usually been subjected to a bending/unbending deformation mode, when the sheet material has slipped over a tool radius. It is thus of utmost importance that the material model can accurately describe the material response, when it is subjected to such a deformation mode. This is considered by the so-called "hardening law" of the material model. In this context the terms "kinematic" or "mixed" hardening are frequently employed. There are numerous such hardening models described in the literature. Common for them all is that they involve material parameters, which have to be determined from some kind of cyclic test. In theory, the most simple and straight forward test is a tensile/compression test of a sheet strip. In practice, however, such a test is very difficult to perform, due to the tendency of the strip to buckle in compression. In spite of these difficulties some successful attempts to perform cyclic tension/compression tests have been reported in the literature. However, common for these tests has been that rather complicated test rigs have been designed and used in the experiments, in order to prevent the sheet strip from buckling. Another method that frequently has been used for the determination of material hardening parameters is the three-point bending test. The advantage of this test is that it is simple to perform, and standard test equipments can be used. The disadvantage is that the material parameters have to be determined by some kind of inverse approach. The current authors have previously, successfully been utilizing this method. In the test the applied force and the corresponding displacement are recorded. The test has then been simulated by means of the Finite Element code LS-DYNA, and the material parameters have been determined by finding a best fit to the experimental force-displacement curve by means of the optimization code LS-OPT, based on a Response Surface Methodology. A problem is, however, that such simulations can be quite time consuming, since the same Finite Element model has to be analyzed numerous times. In the current paper an alternative numerical methodology is described, in which the Finite Element problem only has to be solved a limited number of times, and, thus, considerably reducing the computational cost. In this new methodology a computed moment-curvature curve is fitted to an experimental one. A complicating factor is, however, that all information to determine a moment- curvature relation is not available directly from the experiment. Therefore, the problem has to be solved in two nested iteration loops, where the optimization loop is contained within an outer loop, in which the FE-analysis is performed. It is demonstrated that the parameters determined by this new method correspond excellent to the ones determined by the conventional method.

  • An inverse approach for material parameter identification in a cyclic bending test using LS-DYNA and LS-OPT

    Per-Anders Eggertsen - Chalmers University of Technology, Kjell Mattiasson - Chalmers University of Technology / Volvo Cars Safety Centre

    The residual stresses in the blank after forming are the main cause for the subsequent springback in a sheet forming operation. The accuracy of the predicted springback in a Finite Element simulation of the forming operation is very much determined by the quality of the material modeling. Those parts of the workpiece, which in particular contribute to the global springback, have usually been subjected to a bending/unbending deformation mode, when the sheet material has slipped over a tool radius. It is thus of utmost importance that the material model can accurately describe the material response, when it is subjected to such a deformation mode. This is considered by the so-called "hardening law" of the material model. In this context the terms "kinematic" or "mixed" hardening are frequently employed. There are numerous such hardening models described in the literature. Common for them all is that they involve material parameters, which have to be determined from some kind of cyclic test. In theory, the most simple and straight forward test is a tensile/compression test of a sheet strip. In practice, however, such a test is very difficult to perform, due to the tendency of the strip to buckle in compression. In spite of these difficulties some successful attempts to perform cyclic tension/compression tests have been reported in the literature. However, common for these tests has been that rather complicated test rigs have been designed and used in the experiments, in order to prevent the sheet strip from buckling. Another method that frequently has been used for the determination of material hardening parameters is the three-point bending test. The advantage of this test is that it is simple to perform, and standard test equipments can be used. The disadvantage is that the material parameters have to be determined by some kind of inverse approach. The current authors have previously, successfully been utilizing this method. In the test the applied force and the corresponding displacement are recorded. The test has then been simulated by means of the Finite Element code LS-DYNA, and the material parameters have been determined by finding a best fit to the experimental force-displacement curve by means of the optimization code LS-OPT, based on a Response Surface Methodology. A problem is, however, that such simulations can be quite time consuming, since the same Finite Element model has to be analyzed numerous times. In the current paper an alternative numerical methodology is described, in which the Finite Element problem only has to be solved a limited number of times, and, thus, considerably reducing the computational cost. In this new methodology a computed moment-curvature curve is fitted to an experimental one. A complicating factor is, however, that all information to determine a moment- curvature relation is not available directly from the experiment. Therefore, the problem has to be solved in two nested iteration loops, where the optimization loop is contained within an outer loop, in which the FE-analysis is performed. It is demonstrated that the parameters determined by this new method correspond excellent to the ones determined by the conventional method.

  • An Inverse Approach to Identify the Constitutive Model Parameters for Crashworthiness Modeling of Aluminum Honeycombs and Moving Deformable Barriers

    Murat Buyuk, Cing-Dao (Steve) Kan, Shaun Kildare, Dhafer Marzougui, Hasan Kurtaran - The George Washington University

  • An Investigation into the Relationship between Wood Bat Durability and Bat Taper Geometry using LS-DYNA ®

    Joshua Fortin-Smith, James Sherwood, Patrick Drane (University of Massachusetts Lowell Baseball Research Center), David Kretschmann (U.S. Forest Products Laboratory)

    Changes in the Wooden Baseball Bat Standards (WBBS) by the Office of the Commissioner of Baseball in cooperation with the MLB Players Association in response to recommendations made by a task force comprised wood and baseball science experts have produced a 65% reduction in the rate of multi-piece failures (MPFs) of bats since 2008. It is hypothesized that the rate of MPFs can be further reduced if regulations on the allowable geometries of the taper region for the bats used by MLB teams are implemented in the WBBS. To develop a fundamental understanding of the relationship among (1) the angle of the taper region of the bat, (2) the starting point of the taper along the length of the bat, and (3) wood density, a series of actual and generic bat profiles was investigated using LS-DYNA for bat/ball impacts. In this paper, the results of these bat/ball impact simulations are shared, and a summary of the various combinations of these geometric parameters on bat stress and strain is presented. The durability information gained from these studies is then used to develop an understanding of why certain bat profiles used in professional baseball have relatively high rates of MPFs while other profiles exhibit relatively low rates of MPFs.

  • An Investigation of AL7075-T651 Plate Perforation Using Different Projectile Nose Shapes

    B. Balaban, İ. Kurtoğlu (FNSS Savunma Sistemleri)

    In this study, the ballistic resistance of monolithic and double-layered plates made of AL7075-T651 are evaluated using the non-linear finite element code LS-DYNA®. Plate simulations are carried out using 20 mm diameter, 197g mass hardened steel projectiles with blunt and ogival nose shapes. Penetration simulations of 20 mm monolithic plates made of AL7075-T651 are performed with both Lagrange and ALE methods and the results are compared with literature experimental studies.

  • An Investigation of Maple Wood Baseball Bat Durability as a Function of Bat Profile using LS-DYNA®

    Blake Campshure, Patrick Drane, James Sherwood (University of Massachusetts Lowell)

    During the 2008 Major League Baseball (MLB) season, there was a perception that the rate at which wood bats were breaking was increasing. MLB responded by implementing changes to the wood bat regulations that were essentially transparent to the players, e.g. changing the orientation for the hitting surface on maple bats, setting a lower bound on wood density, and reducing the allowable range for the slope of grain (SoG) of the wood used to make bats. These new regulations resulted in a 65% reduction in the wood-bat breakage rate. It is proposed that a further reduction can be realized by accounting for the role that bat profile plays with respect to bat durability. To begin to develop an understanding of this relationship, a parametric study was conducted using a finite element model on three baseball bat profiles made from maple wood. These bat profiles that span a range of volumes were examined using LS-DYNA to observe their response to bat/ball impacts over a range of game-like speeds. The Altair HyperMesh and LS-PrePost® pre-processors were used in the making of the geometric representation and finite element meshing of the models. The mechanical behavior of the maple wood and its fracturing were modeled using the *MAT_WOOD material model in combination with the *MAT_ADD_EROSION option, respectively. The effective wood material properties were varied as a function of wood density. Results include how bat profile and SoG influence bat durability, where durability is defined as the relative bat/ball speed that results in crack initiation, i.e. the higher the breaking speed, the better the durability. The effective durability of the bat as a function of profile was found to be well predicted by the LS DYNA modeling.

  • An Investigation of Modeling Approaches for Material Instability of Aluminum Sheet Metal using the GISSMO Model

    G. Falkinger (Leichtmetallkompetenz­zentrum Ranshofen LKR), P. Simon (AMAG Rolling)

    The most generally accepted tool for the assessment of formability of sheet material up to the present date is the forming limit diagram (FLD). It allows the identification of critical areas in a sheet - forming simulation where critical thinning or the appearance of cracks is to be expected. The FLD is determined experimentally in Nakajima tests and is widely used in the design of sheet forming processes . However it is known that the assessment based on the FLD is incomplete.

  • An Investigation of Structural Optimization in Crashworthiness Design Using a Stochastic Approach

    Larsgunnar Nilsson, Marcus Redhe - Engineering Research Nordic AB, Sweden

    In this paper the Response Surface Methodology (RSM) and the Stochastic Optimization (SO) are compared with regard to their efficiency and applicability in crashworthiness design. Optimization of simple analytic expressions and optimization of a front rail structure are application used in order to assess the respective qualities of both methods. A low detailed vehicle structure is optimized to demonstrate the applicability of the methods in engineering practice. The investigations reveal that RSM is favoured compared to SO for less than 10-15 design variables. A novel zooming method is proposed for SO, which improve its convergence behaviour. A combination of both the RSM and the SO is efficient. Stochastic Optimization can be used in order to determine an appropriate starting design for an RSM optimization, which continues the optimization. Two examples are investigated using this combined method.

  • An Investigation of the Application of Bolt Pre- Stress and its Effect during Low Speed Impact Loading

    A. Sean Duvall - AMEC

    This report is an initial investigation in to the effect of pre-stress of bolts during impact. The conclusions are not definitive but do indicate that for large strain analysis the effect of pre-stress in bolts is minimal. The effects are more noticeable for lateral impacts than in axial impacts. Further investigation is required to determine the effects of including friction and for other bolted configurations. This report is not an AMEC document and is not subject to AMEC procedures.

  • An Investigation of the Application of Bolt Pre- Stress and its Effect during Low Speed Impact Loading

    A. Sean Duvall - AMEC

    This report is an initial investigation in to the effect of pre-stress of bolts during impact. The conclusions are not definitive but do indicate that for large strain analysis the effect of pre-stress in bolts is minimal. The effects are more noticeable for lateral impacts than in axial impacts. Further investigation is required to determine the effects of including friction and for other bolted configurations. This report is not an AMEC document and is not subject to AMEC procedures.

  • An Investigation on the Roll-Over Crashworthiness of an Intercity Coach, Influence of Seat Structure and Passenger Weight

    Kadir Elitok, Dr. Mehmet A. Guler, Bertan Bayram - Product Development Dept., TEMSA A.S., Dr.-Ing. Ulrich Stelzmann - CADFEM GmbH

    A roll-over event is one of the most crucial hazards for the safety of passengers and the crew riding in a bus. In the past years it was observed after the accidents that the deforming body structure seriously threatens the lives of the passengers, thus the roll-over strength has become an important issue for bus and coach manufacturers. Today the European regulation “ECE-R66” is in force to prevent catastrophic consequences of such roll-over accidents thereby ensuring the safety of bus and coach passengers. According to the said regulation the certification can be gained either by full-scale vehicle testing, or by calculation techniques based on advanced numerical methods(i.e. non-linear explicit dynamic finite element analysis). The quantity of interest at the end is the bending deformation enabling engineers to investigate whether there is any intrusion in the passenger survival space(residual space) along the entire vehicle. In this paper, explicit dynamic ECE-R66 roll-over crash analyses of a stainless-steel bus under development were performed and the strength of the vehicle is assessed with respect to the requirements of the official regulation. Subsequently, different considerations which are not currently mentioned in the regulation (i.e. passenger and luggage weight) and some worst case assumptions such as the influence of the seat structure were investigated. The non-linear explicit dynamics code LS-DYNA as a solver and ANSA and LS-PREPOST softwares as FEA pre/post- processors were utilized throughout the bus roll-over analysis project. The FEA model was generated by using PCs running on Linux Suse operating system whereas the LS-DYNA solutions were performed on a multiple-processor workstation running on an AIX UNIX operating system. During the first stage, a verification of the calculation procedure following regulation ECE-R66 was performed. The verification of calculation is a compulsory requirement of the regulation, as it is the technical service’s responsibility(TÜV Süddeutschland in this case) to verify the assumptions used in the finite element analysis.

  • An Investigation to Compare the Application of Shell and Solid Element Honeycomb Model in ODB

    Mehrdad Asadi - Cellbond, Brian Walker - ARUP, Hassan Shirvani - Anglia Ruskin University

    Cellbond and ARUP have launched their advanced crash barrier models in 2006 and since the time a continuous study has been carried out to distinguish costumer requirements and review feedbacks. Existing barrier models are constructed using the solid element configuration in honeycomb segments along with validated Modified_Honeycomb material cards. Due to a number of demands on using Shell based honeycomb model in crash barriers by car manufacturers, it was decided to investigate the application in detail using fullscale test data. This paper represents the methodology of creating the shellbased ODB and the comparison with existing solid based FE model. Frontal Offset tests are carried out by a large number of test houses worldwide, according to the European regulation and to FMVSS, as well as by EuroNCAP, Australian NCAP, JNCAP and IIHS. In the frontal offset test, only one side of a vehicles front end hits the deformable barrier, which means that a more concentrated area of the vehicles structure must sustain the impact of the crash rather than the whole width of the vehicle. The Cellbond ODB barrier has been investigated which consists of two different sized aluminium honeycomb blocks in main body and bumper partially covered in aluminium skins. Number of static compressive tests performed to specify honeycomb and adhesive material characters. Adhesive properties are obtained using Climbing Drum, TPeel, Tensile and Plate Shear test results. The barrier was subjected to four individual test conditions with different impactor and impact speeds.

  • An Investigation to Compare the Application of Shell and Solid Element Honeycomb Model in ODB

    Mehrdad Asadi - Cellbond, Brian Walker - ARUP, Hassan Shirvani - Anglia Ruskin University

    Cellbond and ARUP have launched their advanced crash barrier models in 2006 and since the time a continuous study has been carried out to distinguish costumer requirements and review feedbacks. Existing barrier models are constructed using the solid element configuration in honeycomb segments along with validated Modified_Honeycomb material cards. Due to a number of demands on using Shell based honeycomb model in crash barriers by car manufacturers, it was decided to investigate the application in detail using fullscale test data. This paper represents the methodology of creating the shellbased ODB and the comparison with existing solid based FE model. Frontal Offset tests are carried out by a large number of test houses worldwide, according to the European regulation and to FMVSS, as well as by EuroNCAP, Australian NCAP, JNCAP and IIHS. In the frontal offset test, only one side of a vehicles front end hits the deformable barrier, which means that a more concentrated area of the vehicles structure must sustain the impact of the crash rather than the whole width of the vehicle. The Cellbond ODB barrier has been investigated which consists of two different sized aluminium honeycomb blocks in main body and bumper partially covered in aluminium skins. Number of static compressive tests performed to specify honeycomb and adhesive material characters. Adhesive properties are obtained using Climbing Drum, TPeel, Tensile and Plate Shear test results. The barrier was subjected to four individual test conditions with different impactor and impact speeds.

  • An Ivestigation into Modeling Approaches for the Dynamic Response of a Shipping Container Cart and Suspended Automotive Parts under Random Base Excitation using LS-DYNA

    Prof. S. Noll, A. Ramanathan (Ohio State University); E. DeHoff, R. Rittenhouse (Honda)

    Shipping containers are exposed to complex dynamic loading conditions during transport via truck, rail, and air. The loading conditions are further complicated by contact nonlinearities between the cart and ground, between cart holders and suspended parts, and between neighboring suspended parts. This study focuses on developing a modeling strategy to simulate a container cart with parts undergoing ASTM D4728 truck random vibration tests. Initially, the linear frequency-domain properties and response to a random excitation profile of the cart structure were examined and correlated with experimental measurements. The linear response predictions lacked the required modeling fidelity to capture the nonlinear dynamic behavior observed during the testing as the input power spectral density profile was increased to higher levels. Thus, the nonlinear response was then simulated in the time domain using the explicit integration method in LS-DYNA®. The use of LS-DYNA® also allowed the simulation of the complex contact-driven boundary conditions. The total run time was determined to be prohibitively long for the second approach as the time step size was 0.3 μsec for the required simulation duration of more than 5 sec. Finally, a dynamic substructuring strategy was employed through the use of super elements. This final approach captured the dynamic amplification of the cart, maintained the contact nonlinearities, and reduced the total run times. This modeling approach in LS-DYNA® appears promising to capture the complex dynamic loading conditions affecting shipping containers in a computationally efficient manner.

  • An LS-DYNA material model for simulations of hot stamping processes of ultra high strength steels

    Dr. Tobias Olsson - Engineering Research Nordic AB

    This paper present a new material model (*MAT_244) in LS-DYNA capable of simulating phase transition during quenching and forming. Usually during forming the blank is initially heated to become fully austenitized and then continuously formed and cooled. When the temperature is decreasing the austenite decomposes into different product phases. The amount of each phase does not only depend on the mechanical history, but also on the cooling rate of the blank. A higher cooling rate increases the amount of the harder phases (bainite and martensite) whereas a slow process gives higher content of ferrite and pearlite. This thermo-elastoplastic model is based on the isotropic von-Mises yield criterion with an associated plastic flow rule. It includes both the decomposition of austenite into ferrite, pearlite, bainite and martensite, and transformation plasticity. The examples show that the model is well suited for hot stamping simulations and it should be possible to simulate different steel compositions at different cooling rates to obtain a good prediction of the hardening process and the properties of the final product.

  • An LS-DYNA material model for simulations of hot stamping processes of ultra high strength steels

    Dr. Tobias Olsson - Engineering Research Nordic AB

    This paper present a new material model (*MAT_244) in LS-DYNA capable of simulating phase transition during quenching and forming. Usually during forming the blank is initially heated to become fully austenitized and then continuously formed and cooled. When the temperature is decreasing the austenite decomposes into different product phases. The amount of each phase does not only depend on the mechanical history, but also on the cooling rate of the blank. A higher cooling rate increases the amount of the harder phases (bainite and martensite) whereas a slow process gives higher content of ferrite and pearlite. This thermo-elastoplastic model is based on the isotropic von-Mises yield criterion with an associated plastic flow rule. It includes both the decomposition of austenite into ferrite, pearlite, bainite and martensite, and transformation plasticity. The examples show that the model is well suited for hot stamping simulations and it should be possible to simulate different steel compositions at different cooling rates to obtain a good prediction of the hardening process and the properties of the final product.

  • An LS-DYNA Model for the Investigation of the Human Knee Joint Response to Axial Tibial Loadings

    Dr. Chiara Silvestri, Doug Heath, Prof. Dr. Malcolm H. Ray - Worcester Polytechnic Institute

    Automotive accidents frequently involve fracture of the knee joints which can be related to either bone or soft tissue injuries. Previous studies show that the degree of anterior-posterior constraint of the femur bone along its longitudinal axis plays a crucial role in determining the knee-joint-fracture mechanism and internal tibial-femoral load distribution. Also, the anatomical tilt of the tibial plateau, tibial-femoral joint compression results in anterior displacement of the tibia, which has important implications in the prediction of knee injury and might lead to anterior cruciate ligament rupture. This study aimed at validating an existing finite element LS-DYNA® human knee joint model for replication of these complex failure mechanisms when the joint is subjected to tibial axial compression loads. Simulations were run with the joint at 90 ̊ flexion to investigate the effects of anterior-posterior joint constraint on the injury patterns. Comparisons between simulations findings and test outcomes from literature were compared in terms of anterior- posterior and medial displacements of the femur, proximal rotation of the tibia and tibial-femoral load distribution. The finite element model predicted similar injury patterns and internal loads resulted with cadaveric specimen testing. The validated numerical model can be integrated in a complete replication of the human lower extremity and employed in simulations of knee-bolster impacts with the human leg during car crashes. It would be used to predict leg injury patterns with the knee joint subjected to simultaneously axial loading of the femur and the tibia bones.

  • AN LS-DYNA USER DEFINED MATERIAL MODEL FOR LOOSELY WOVEN FABRIC WITH NON-ORTHOGONAL VARYING WEFT AND WARP ANGLE

    Marlin Brueggert, Romil R. Tanov - Center for Advanced Product Evaluation, Division of IMMI

    The behavior of loosely woven fabrics (LWF) differs significantly from other types of woven fabric materials, the major difference being the significant change that the angle between the weft and warp fibers undergoes as the fabric stretching forces change. These unique characteristics have made the LWF a very important part for the functionality of some recently developed occupant protection safety devices for the automotive and heavy machine and truck industry. To efficiently model and analyze the behavior of such devices within an occupant protection model, an accurate representation of the characteristics of the LWF is needed. However, none of the many available LS-DYNA material models seem to fit well with the unique kinematics of the LWF. Therefore, the aim of this work is to present the basics of a formulation for a material model for the analysis of LWF and its implementation as a user defined material in LS-DYNA. To assess the performance of the model, results from the simulation are presented. Although relatively simple, the developed model seems to represent very well the behavior of the LWF and the simplicity of the formulation attributes to the efficiency and stability of the user defined material subroutine.

  • An LS-OPT® methodology for utilizing partial curve data for the calibration of material models

    N. Stander, A. Basudhar (LSTC), S. Du Bois (DYNAmore),

    Parameter estimation is a considerably large application area of optimization. It fulfills the important purpose of characterizing materials based on models available in Finite Element analysis software such as LS-DYNA®. The development of special LS-OPT® features for parameter estimation using Digital Image Correlation and other experimental methods has been ongoing for a number of years. In earlier papers [1,2] some of the available similarity measures as well as the LS-OPT DIC methodology were discussed in broad detail and illustrated with examples.

  • An MPP Version of the Electromagnetism Module in LS-DYNA for 3D Coupled Mechanical-Thermal-Electromagnetic Simulations

    P. L'Eplattenier, C. Ashcraft - Livermore Software Technology Corporation, I. Ulacia - Mondragon Goi Eskola Politeknikoa

    A new electromagnetism module is being developed in LS-DYNA for coupled mechanical/thermal/electromagnetic simulations. One of the main applications of this module is Electromagnetic Metal Forming (EMF). The electromagnetic fields are solved using a Finite Element Method (FEM) for the conductors coupled with a Boundary Element Method (BEM) for the surrounding air/insulators. Both methods use elements based on discrete differential forms for improved accuracy . Recently, a Massively Parallel Processing (MPP) version of the EM module was developed allowing sharing the CPU and memory between different processors and thus faster computations on larger problems. The implementation of the FEM and BEM in MPP will be presented. The EM module will then be illustrated on an actual EMF case. Experimental and numerical results will be compared and the speed-up of the MPP version will be studied. Finally, a new contact capability for the electromagnetic fields will be presented and illustrated on a rail gun simulation.

  • An Objectivity Algorithm for Strain Softening Material Models

    Mauricio V. Donadon, Lorenzo Iannucci - Imperial College London

    Predictive techniques for the analysis and design of metallic or composite components and structures subject to severe loading can lead to significant mesh sensitivity if cracking or tearing or penetration occurs. This is especially important for composite materials in which the material has an elastic brittle response with little or no plastic behaviour, in which energy could be dissipated. Hence, the full potential use of composite in the design of advanced composites and structures has not yet been exploited fully. This work constitutes an effort directed towards the development of an objectivity algorithm for strain softening material models based on the ‘smeared cracking formulation’. The algorithm has been implemented into LS-DYNA for hexahedron solid elements and correctly accounts for crack directionality effects. Thus enabling the control of energy dissipation associated with each failure mode regardless of mesh refinement and element topology. The advantage of the present technique is that mesh size sensitivity on failure is removed leading to results, which converge to a unique solution, as the mesh is refined. If such a scheme were not introduced results could change significantly from mesh to mesh leading to an incorrect structural response. The proposed algorithm has been validated by a series of benchmark tests using different degrees of mesh refinement and element topologies.

  • An Optimization Procedure For Springback Compensation Using LS-OPT

    Nielen Stander, Mike Burger, Xinhai Zhu, Bradley Maker - Livermore Software Technology Corporation

    The purpose of this study is to develop a methodology for springback compensation in sheet metal stamping operations. An optimization method is employed to minimize the difference between the simulation results and the intended design. This procedure results in an optimized die shape. LS-DYNA, LS-OPT and TrueGrid are used to input original tool geometry, material, and process parameters, identify design variables, perform springback simulations, and output optimized tool geometry. It is found that springback trends are consistent with changes in the die shape, which provides an effective strategy for springback compensation. The standard NUMISHEET’96 S-Rail is used as a benchmark example in this study.

  • An Overview of LS-OPT Version 4.1

    Nielen Stander, Tushar Goel - Livermore Software Technology Corporation

    The main focus of the LS-OPT V4.1 development has been to further expand the graphical postprocessor and to significantly improve reliability, usability and transparency when distributing solver jobs across networks. Much of the latter has been accomplished through industrial collaboration. While LS-OPT originated as an LS-DYNA® based tool, new features are increasingly being developed to facilitate interfacing with non-LS-DYNA solvers. This is necessitated by the increasing requirement for conducting multidisciplinary optimization, thereby involving more than one solver type. Therefore, in V4.1, LS-OPT now has MSC NASTRAN support for mode tracking and frequency extraction. A generic extractor has also been added to aid result extraction from text files.

  • An Overview of User Defined Interfaces in LS-DYNA

    Tobias Erhart - Dynamore GmbH

    The user-defined features in LS-DYNA are powerful tools that allow users in academia or industry to verify research results in the context of general and complicated finite element applications. Implementation work concerns only the special field of interest, and there is no need for the comprehensive task of developing and maintaining the complete finite element software. The most popular user interface is for material modeling. But there also exist user interfaces for structural elements, airbag sensors, solution control, friction, interface control, weld failure, loads, output control, adaptivity, thermal contact, and others. An overview of current user-defined interfaces in LS-DYNA version 971 R5.0 will be presented. The aim of this contribution is to bring together the possibilities to add own numerical models and algorithms to the code. Therefore, each interface is described in its functionality. It will be explained, how to activate the particular interface in the input, where to find the corresponding subroutine, and which input/output arguments can be used.

  • AN UPDATED TOOLBOX FOR VALIDATION AND UNCERTAINTY QUANTIFICATION OF NONLINEAR FINITE ELEMENT MODELS

    Keng C. Yap, G. Wije Wathugala, Timothy K. Hasselman - ACTA Inc.

    It is becoming commonplace to use numerical simulations supported by limited experimentation for the characterization of physical phenomena. This trend, with its perceived potential for reducing costs, is the basis for the simulation-based procurement initiatives currently gaining momentum within the government and industry. Insuring the quantitative viability of a simulation-based procurement still requires some experimental data upon which the assessment of simulation accuracy can be based. In addition, it requires minimizing the differences between corresponding analytical and experimental results in physically meaningful ways, and characterizing the ability of the models to predict future events. The purpose of model validation and uncertainty quantification is to confirm the correctness and credibility of numerical simulations, so that the underlying models may be used with greater confidence to extrapolate limited test experience to a range of practical applications. In this paper, an advanced principal components-based computational procedure is demonstrated by validating the DYNA models used to achieve HFPB numerical simulations of physical processes important to assessing weapon- target interaction. Bayesian statistical parameter estimation is used to estimate material parameters that cannot be measured directly, such as strain rate enhancement and shear dilatency in reinforced concrete structures. This demonstration is performed using an updated MATLAB® Nonlinear Model Validation and Verification Toolbox. The work reported in this paper has resulted in improvements to the original Toolbox. A multi-level parameter estimation procedure is implemented to sequentially accumulate information from prior estimates in a Fisher information matrix for use in subsequent parameter estimates. The use of a generic uncertainty model in estimating the predictive accuracy of future DYNA simulations is enhanced through the use of a reduced set of principal component metrics and a basis augmentation technique.

  • Analysis and Design of a Unique Security Bollard Installment Using LS-DYNA® for a K12 Vehicle Impact

    Joseph M. Dulka, Eric R. Dietrich, Kelley S. Elmore, Kendra D. Jones, Clyde S. Harmes, Robert H. Moyer (elmore engineering)

    This paper presents the design process for a unique security bollard providing protection against a K12 [1] (M50 [2]) vehicle crash load. LS-DYNA was used to aid in the design of the security bollard to account for the highly dynamic and inelastic behavior during a vehicle impact. The bollard was installed along the top of a wall for a below-grade courtyard in order to maintain a building security perimeter, providing protection against a potential malevolent vehicle attack. Contrary to typical bollard installations where the foundation is supported on all sides with well compacted soil or other substrata, no significant support was provided on the protected side of the bollard foundation. As a result, this posed significant difficulty in the design of an effective security bollard required to resist a potential K12 (M50) vehicle impact load with zero vehicle penetration. The initial conceptual bollard design originated from the standard Department of State (DoS) DS-22 K-12 rated bollard system [3]. Hand calculations were used to develop a preliminary bollard design with equivalent static design stopping forces based upon existing physical K12 test results. LS-DYNA aided the engineering team in observing structural and material responses characteristic of impact loading which may have otherwise not been perceived by method of traditional hand calculations. Utilizing LS-DYNA as not only an analysis tool, but a powerful design tool enabled the engineering team to optimize the design of the security bollard.

  • Analysis and Design of Large-Scale Civil Works Structures Using LS-DYNA

    David DePolo, Eric Kennedy, Thomas Walker, Ryan Tom - US Army Corps of Engineers

    The Folsom Joint Federal Project (JFP) Auxiliary Spillway is a high profile addition to the Folsom Dam, located approximately thirty miles upstream of Sacramento, California. Total concrete placements on the project will exceed 140,000 cubic yards at a projected cost of nearly $1 billion. The main component of the JFP is a large concrete control structure with steel bulkhead gates, submerged tainter gates, and post-tensioned anchorage. As a critical piece of the flood control system in a densely populated, active seismic region, the JFP demanded a rigorous analysis of a scale never before used by the U.S. Army Corps of Engineers to design a civil works structure. The Sacramento District of the Corps developed a three-dimensional LS-DYNA model of the control structure, foundation, and reservoir in order to capture the fluid-structure and soil-structure interaction during a seismic event, something not possible with standard dam analysis procedures. The model incorporated anomalies within the foundation; their effects were significant and could not have been established and properly accounted for without the LS-DYNA model. The analysis examined seven suites of ground motions and two pool elevations that envelope the expected demand on the structure. Results from the model were used for both evaluation and design purposes. This paper presents suggestions on the modeling of large scale civil works structures such as the JFP. Included is an overview of lessons learned regarding contact definitions and troubleshooting, the application and scaling of seismic input, and methods for accurately modeling the behavior and load paths. Extensive verification of the LS- DYNA results was conducted using another widely used finite element analysis program; the procedures and results are discussed. Additionally, the paper advises on items to be considered during model development, with a focus on generating output suitable for design.

  • Analysis and Optimization of Aluminum Automobile Side Door Design Using LS-DYNA® Implicit and LS-OPT®

    Akshay Kulkarni, Richard Newton (Novelis Inc.)

    Vehicle design and development involves various types of linear and non-linear finite element analyses. Using different solvers for different types of analyses is not always a cost-effective solution. Using one solver for multiple types of analysis saves cost as well as it allows sharing CAE models between various disciplines. Although LS-DYNA historically has been used for explicit analysis, recent enhancements in LS-DYNA Implicit enable it to be used for various implicit analyses. This work focuses on the analysis and optimization of an automobile side door assembly made of aluminum, using LS-DYNA Implicit Solver for multiple load cases. A combination of Novelis’s high formable and high strength aluminum alloys were used in the door design. Implicit load cases used for this analysis were – modal analysis, door sagging, door frame stiffness, and beltline stiffness. LS-DYNA Implicit models were further used for setting up DOE and design optimization. LS-OPT tool was used to conduct multi-response DOE studies and optimization to minimize the door weight while meeting all the performance requirements. Additionally, the DOE runs results were combined with Excel cost model results to choose an optimal design that balanced the total mass of the door versus the cost to manufacture. A final validation simulation was run to demonstrate the optimized design met all expected performance requirements.

  • Analysis and Testing of a Composite Fuselage Shield for Open Rotor Engine Blade-Out Protection

    J. Michael Pereira, Charles R. Ruggeri, Duane M. Revilock (NASA Glenn Research Center), William Emmerling (FAA William J. Hughes Technical Center, Atlantic City), Silvia Seng, Charles Frankenberger (Naval Air Warfare Center, China Lake), Kelly S. Carney (George Mason University)

    The Federal Aviation Administration is working with the European Aviation Safety Agency to determine the certification base for proposed new engines that would not have a containment structure on large commercial aircraft. Equivalent safety to the current fleet is desired by the regulators, which means that loss of a single fan blade will not cause hazard to the Aircraft. The NASA Glenn Research Center and The Naval Air Warfare Center (NAWC), China Lake, collaborated with the FAA Aircraft Catastrophic Failure Prevention Program to design and test lightweight composite shields for protection of the aircraft passengers and critical systems from a released blade that could impact the fuselage. LS-DYNA ® was used to predict the thickness of the composite shield required to prevent blade penetration. In the test, two composite blades were pyrotechnically released from a running engine, each impacting a composite shield with a different thickness. The thinner shield was penetrated by the blade and the thicker shield prevented penetration. This was consistent with pre-test LS-DYNA predictions. This paper documents the analysis conducted to predict the required thickness of a composite shield, the live fire test from the full scale rig at NAWC China Lake and describes the damage to the shields as well as instrumentation results.

  • Analysis of a Propane Tank Truck Impacting a Concrete Column Using LS-DYNA

    Clayton F. Heberling - Pressure Sciences, Inc.

    Pressure Sciences Inc. used LS-DYNA to model a propane tank truck colliding with a concrete column. The analysis simulates an accident that occurred in 1994 in White Plains, New York. Correlation between the accident and an LS-DYNA analysis of that crash is described. The ultimate purpose of the analyses is to improve the crashworthiness of propane semi-trailers. To address the stiffening effect of the propane fluid, we correlated several models with drop tests that had been performed on 1/12 scale railroad tank car heads. The heads included unpressurized heads, fluid pressurized heads, and fluid pressurized heads with an air cushion. In order to model the liquid propane, explicit solid elements were used. The material model used for the propane was the elastic material model with the fluid option. The paper describes the procedure used to incorporate the elastic material model with the fluid option. The propane vapor was modeled using explicit solid elements and the null material model with a linear polynomial equation of state. The paper gives the derivation of a simplified version of the linear polynomial equation of state to simulate Boyle’s law. We were able to use LS-DYNA to obtain good correlations with drop tests when we modeled the liquid using the elastic material model with the fluid option and the vapor with a null material with the linear polynomial equation of state. We also obtained reasonable correlations between our LS-DYNA model and the White Plains, NY accident involving a propane tank truck and a concrete column.

  • Analysis of a single stage compressed gas launcher behaviour : from breech opening to sabot separation

    F. Plassard, J. Mespoulet, P. Hereil - Thiot-Ingenierie

    Single stage compressed gas guns are used in Shock Physics laboratory to perform characterization experiments and ballistic events. The main advantage of this kind of launcher is that impact conditions are well defined (impact obliquity, impact velocity). In order to achieve high quality in ballistic performance, it is essential to understand the behaviour of the projectile in the barrel of the gun. This paper is devoted to the simulation of the whole behaviour of a laboratory gun, from breech opening up to the muzzle blast sabot separation due to air drag forces. LSDYNA was used as a numerical tool for the improvement of the launched package behaviour which consists in sabots and projectile. The simulation needs to reproduce the in-bore operations of a launcher taking into account gases which act on both sides of the projectile: very high pressures release at the base as well as pressure built-up and the gas thrown out from the tube at the front. There is also a need to predict perfectly the sabots behaviour when the projectile is released from the tube so as to control the impact conditions on the target. The Fluid / Stucture Interaction (FSI) capability of LSDYNA is used as a numerical tool to increase the knowledge in this field. The challenge is to obtain a simulation recreating the effect of gases on the projectile at both high pressures and high velocities. High speed and ultra high speed video cameras set up in our facility allow us to make correlation between calculations and experiments and so validate the simulation. This work gives to our Laboratory a real tool for optimizing the sabots design in terms of material, shape, dimensions and thus increases the quality and reliability of ballistic experiments.

  • Analysis of Extended End-Plate Connections Under Cyclic Loading Using the LS-DYNA Implicit Solver

    Ashish Bhargava, W.M. Kim Roddis, Dhafer Marzougui, Pradeep K. Mohan - The George Washington University

    Moment-Resisting Frames (MRF’s) are widely used as lateral-force resisting systems in buildings. Their successful performance depends on the behavior of their moment-resisting beam-column connections. In regions at risk for earthquakes, MRF’s need to resist large cyclic forces and displacements. A variety of beam-column connections are used in practice. Most, including end plate connections, are designed assuming the MRF seismic capacity is based on the ability of the connection to allow inelastic rotation through the development of plastic hinges within the beam elements of the structure. In this paper, Finite Element (FE) computer analysis is used to simulate the behavior of the joint region of an MRF. A computer model of the MRF’s extended end plate beam-column connection was created and its performance was analyzed under cyclic loading condition. The LS-DYNA implicit solver was used in this study. Results from these simulations were compared to previously conducted physical tests. The results show good correlation with the measured test data. The work demonstrates the ability of LS-DYNA to simulate the cyclic behavior of this type of beam-column connection and is a step toward using physically calibrated computational model to complement physical testing for the future evaluation of this type of structural detail.

  • Analysis of Fibre Orientation using μCT Data

    Sebastian Mönnich, Robert Glöckner , Florian Becker - German Institute for Polymers (DKI)

    Integrative simulations are based on a calculated bre orientation from which the local material properties can be derived in several ways. For instance the micro-mechanical model proposed by Tandon and Weng may be used coupled with an orientation averaging approach to include the bre orientation. This approach then gives the elastic properties of the bre matrix compound with a strong dependency, of e.g. the elastic modulus, on the bre orientation. Modeling failure for nite element simulations, e.g. crash, also requires knowledge of the bre orientation, because the failure strains and energy dissipation also depend on the orientation of the bres [1, 2]. The accuracy of the calculated bre orientation depends on several simulation input parameters, which are not necessarily physical properties. The most important example is the bre interaction coecient (c). This parameter allows the user to modify the calculated bre orientation from isotropic to transversely isotropic [3]. In this paper a new experimental method to determine the bre interaction coecient is presented. The classical approach to validate the calculated bre orientation would be the usage of optical microscope images of cut surfaces of the specimen and the calculation of the bre orientation by measuring the cut ellipsis dimensions. This method is very time consuming and with respective to the necessary magnication not very accurate, because not all bres can be accounted for. The new method is using a model based algorithm to analyze three-dimensional micro computer tomography measurements. This enables the identication of up to 90% of the bres within the specimen and calculate a second order orientation tensor and the bre length distribution in any arbitrary space. Due to the fact that a model based algorithm is used, the bre detection can also be performed, if the density of the matrix polymer is near to the density of the bre material. This is a novelty to existing bre orientation measurements with computer tomography. To obtain reliable data which can be directly compared with injection moulding simulations, several steps had to be taken. First of all a representative volume must be dened, in which the bre orientation will be evaluated. This representative volume must be the same in the injection moulding simulation and the μCT measurement. As the injection moulding model is already discretized, the representative volume is set as a stack of nite elements over the part thickness. To calculate the second order orientation tensor in exactly the same geometrical space and the same coordinate system as in the injection moulding simulation, it was necessary to develop a method which allows a reconstruction of the original part from which the μCT specimen was taken. A special painting and evaluation procedure were implemented into the existing method to recalculate the original position and orientation of the specimen, enabling us to achieve the desired measurements. At the moment the determination of the bre interaction coecient requires still many injection moulding simulations, which then are compared to the measured values. This allows for a more realistic bre coecient in comparison to the default parameter. The next steps are to automate the described procedure and to correlate the measured bre orientations directly with the bre interaction coecient to avoid unnecessary simulations.

  • Analysis of formability of advanced high strength steel sheets with phenomenologically based failure criteria with separate treatment of instability, shear and normal fracture

    K. Isik, C. Soyarslan, A.E. Tekkaya - Technical University of Dortmund, H. Richter - ThyssenKrupp Steel Europe AG

    Despite their wide application in sheet metal forming analysis, Forming Limit Diagrams cannot supply reliable results for the cases involving non-proportional strain paths or material classes with reduced ductility such as advanced high strength steels (AHSS). Fracture criteria appear as complimentary tools for assessment of formability in these cases. CrachFEM, as an advanced failure model, merges an instability criterion that includes strain hardening and yield loci effects with fracture criteria which monitor damage accumulation for ductile normal fracture and ductile shear fracture separately where stress triaxiality ratio and maximum shear stress dependence are taken into account, respectively. In the present study, rectangular deep drawing of two AHSS classes is studied both experimentally and numerically. Blanks with different rolling directions and blank orientations with respect to the punch are taken into account. Simulations are conducted using CrachFEM failure model and LS-DYNA where texture of the sheet due to rolling is modeled with Hill’48 type anisotropic yield locus. Experimental studies reveal that the failure occurs mainly due to instability with necking whereas in- plane shear stress state in drawing zone seems to be insufficient to create shear fracture. Numerical results show not only the predictive capability of CrachFEM but also regarding weaknesses which needs improvement for better predictions.

  • Analysis of High Velocity Impact Penetration Using the Smoothed Particle Galerkin Method

    Youcai Wu, Yong Guo, C. T. Wu, Wei Hu (LSTC), Joseph Magallanes (Karagozian & Case)

    Impact penetration is a very complex multi-physics procedure, which involves localized damage, large degree of material fragmentation (failure) and separation (ejecta), complicated projectile – target interaction. The mathematical models of these problems are often ill-posed and the corresponding numerical solutions are generally non-smooth. In essence, severe mesh distortion would occur if Lagrangian finite element method (FEM) is used. Furthermore, ad-hoc erosion criteria are usually needed to model the fragmentation process for the mesh-based formulation. In this paper, the smoothed particle Galerkin (SPG) meshfree method [1] in LS-DYNA ® is tested for the analysis of this type of problems. SPG method is a pure particle method based on the nodal integration of nonlocal Galerkin weak formulation. Numerically, the SPG formulation [1-4] is designed to alleviate the zero-energy modes in the conventional meshfree method and to naturally handle the material separation during the failure process. Good agreement with experimental data was observed in the numerical results, which indicates the potential of the SPG formulation in modeling the material failure and associated debris tracking in impact penetration problems.

  • Analysis of LS-DYNA MOR Approaches for Application in Crash Analysis and Integration in SDM Workflows

    Z. El Khatib, U. Reuter (TU Dresden), M. Thiele (SCALE)

    Numerical simulations are often characterized by long computational times, especially as the size of the model grows larger. In many cases, this necessitates the use of a high-performance computer in order to speed up the simulation and obtain results faster. Nevertheless, computational times can still be large, such as in the automotive and aerospace industries. The automotive industry is highly dependent on numerical modelling. Companies perform numerical simulations for crash analysis in the preliminary phases of design, because it eliminates the need to perform expensive physical crash tests of prototypes. Optimization, another time-consuming process, is also often performed during the different stages of a project and is only possible using virtual testing. However, optimization adds to the scale of computational time needed in the automotive industry for virtual product development. The longer it takes to perform such numerical processes, the longer the time-to-market of a certain vehicle model and eventually, the higher the cost.

  • Analysis of Partially Confined Blast Experiments and Simulations

    Len Schwer Schwer Engineering & Consulting Services

    Data and simulation results presented by Teland et al. (2018) for incident and reflected pressure histories indicated the simulation results time of arrival and pressure magnitude did not agree well with the data for the reflected shock. They posited three possibilities for the differences: (1) Charge load (explosive mass per chamber volume), (2) Afterburning and (3) Variable Gamma for the gas mixture.

  • Analysis of the Scatter of a Deploying Airbag

    R. Brown, M. Bloomfield (JaguarLandrover), C.-A. Thole, L. Nikitina (Fraunhofer Institute SCAI)

    This paper discusses some of the challenges faced by the automotive industry in dealing with the natural variation in input parameters and environmental factors that lead to scatter in results. We describe how a lack of consideration of this variation can lead to surprises during testing, with the associated risk of unplanned cost, and present a technique using Principal Components Analysis to improve the robustness of CAE crash models. In a purely virtual product development world, increasingly demanding functional requirements, and pressure on weight and cost, mean that analysis techniques must lead to designs that are robust with respect to external noise sources; large safety margins are no longer acceptable. Conventionally the CAE process has used nominal values for input parameters, and has been satisfied with single, deterministic solutions. However, virtual techniques have much to offer in understanding and managing scatter, and the consideration of variability in the CAE process is becoming more common-place. At the same time, the CAE method introduces its own issues associated with model stability, and these must also be addressed before design optimisation is attempted. Frequently, analysis approaches used to improve design robustness can also be applied to issues of model stability, and we describe an example where Principal Components Analysis within the Diffcrash software package has been used to identify a source of instability in an airbag model. The mathematical background to the PCA method is presented, explaining its application to the analysis of variation, and showing how it can help in locating a source of scatter in results. The airbag example illustrates how this can be applied to allow changes to the modelling technique (or to the design) to be made to reduce the scatter. In this example, the source of the different airbag behaviours shown in figure 1 was identified as being a contact issue at an earlier point in time (figure 2), and a modification to the contact definition led to a reduction in the dispersion in results. Lastly we offer insight into the requirements for deployment of such techniques, and describe how process integration is a fundamental necessity for a successful, sustained implementation.

  • Analysis of Unsteady Aerodynamics of a Car Model in Dynamic Pitching Motion Using LS-DYNA® R7

    Yusuke Nakae, Tsuyoshi Yasuki, Hiroshi Tanaka, Jiro Takamitsu (Toyota Motor Corporation)

    This paper describes the numerical analysis of unsteady aerodynamics of a car model in dynamic pitching motion using LS-DYNA R7. Large-Eddy simulations with ALE method were performed to clarify the effects of unsteady aerodynamic forces on aerodynamic characteristics of cars in dynamic motion. The forced sinusoidal pitching oscillation was imposed on the 1/4 scaled car model and the flow velocity was set to 27.78 m/s. The model was based on a real production car and it was simplified by removing its engine compartment cavity and smoothing its surface. Tires were fixed on the ground and separated from the car body. Unsteady aerodynamic forces acting on the model were investigated. And the mechanism of the differences between the aerodynamic forces acting on the car model in the dynamic motion and those in stationary states occur was mainly discussed. The computational results showed good agreement with the results of the high accuracy LES code computations. Also, results showed the differences between the aerodynamic forces in the dynamic pitching motion and those in the stationary states. Especially, the lift force showed remarkable differences. Even in the same posture of the pitch angle 0 degree (i.e. the posture in which the under floor of the car body is parallel to the ground), the lifts showed different values at stationary state and during nose-up or nose-down respectively. As a result of this analysis, it was revealed that these differences in the aerodynamic forces were mostly due to the changes of the surface pressure distributions around rear end of the front wheelhouse. The flow structures behind the front tires changed with volume shrinking or expanding of front wheel house owing to the car motion. These changes affected the surface pressure distributions.

  • Analysis of Unsteady Aerodynamics of a Car Model with Radiator in Dyna­­mic Pitching Motion using LS-DYNA

    Y. Nakae, J. Takamitsu, H. Tanaka, T. Yasuki (Toyota Motor)

    This paper describes the numerical analysis of unsteady aerodynamics of a radiator mounted car model in dynamic pitching motion using LS-DYNA ICFD solver. Large-Eddy simulations with ALE method and porous media modeling were performed to clarify the unsteady aerodynamic forces acting on cars with engine compartment in dynamic motion.

  • Analyzing 'Noisy' Structural Problems with LS-OPT: Probabilistic and Deterministic Fundamentals

    Willem Roux, Nielen Stander - Livermore Software Technology Corporation

    System identification of 'noisy' structural design optimization problems: the sources of uncertainty, the competing roles of bias and variance, and the interaction of uncertainty and deterministic effects. Two test problems are used to clarify the effect of different approaches.

  • Analyzing Bicycle Accidents with Human Body Models

    V. Alvarez (Lightness by Design), H. Wendelrup (Hövding), K. Brolin (Lightness by Design)

    For the past 20 years, single-bicycle accidents have been the most common cycling accidents in Sweden (more than 70% of all injuries) [1-4] and in other countries where many people use bikes as means of transportation [5-6]. Vehicles were involved in a majority of the lethal bicycle accidents. Neck injuries were a small portion of all cycling injuries, but they were associate with a large risk of permanent medical impairment. Therefore, it is interesting to explore if head protective safety devices can provide safety benefits for the neck as well. Hövding is a head protective device that is worn as a scarf around the neck, with sensors that trigger inflation of an airbag in case of an accident. Theoretically, the portion of the airbag that surrounds the neck could protect from neck injuries (see Fig. 1).

  • Analyzing Elastomer Automotive Body Seals Using LS-DYNA

    Linhuo Shi - TG North America Corporation

    Several different elastomer automotive body seals (weatherstrips or weather seals) are analyzed using explicit solver of LS-DYNA. The results are compared with those obtained from non-linear finite element analysis (FEA) solvers widely used for elastomer analysis as well as the experimental results. It is found that properly modeled LS-DYNA can be a very good tool for elastomer body seal analysis, especially for the analysis with potential instabilities, such as snap-through, loss-of-contact, severe slip-stick, and complicated contact problems.

  • Anatomically accurate finite element model of a human head for crash applications

    Alberto Tacchi, Ivan Colamartino, Gabriele Canzi, Giorgio Novelli, Marco Anghileri

    Every year road traffic accidents are responsible of approximately 1.3 million deaths in the world, resulting in one of the main causes of mortality. According to the World Health Organization (WHO), by the 2020s road traffic accidents will be the leading cause of premature death. Moreover, between 20 and 50 million people involved in incidents suffer non-fatal injuries, most of them leading to disabilities [1]. These injuries considerably affect individuals, their families, and nations from both social and economic points of view. Over the last 60 years, experimental activities focused on the impact behavior of the human body were carried out with crash dummies and human cadavers, expanding the available injury database, exposing the most common injury scenarios and allowing the development of effective predictive criteria. The most frequently injured body regions resulted to be head and lower limbs; however severe to fatal injuries (Abbreviate Injury Scale values AIS 3+), are more commonly related to head impacts, as shown in Figure 1 [2].

  • Anisotropic Behaviors and Its Application on Sheet Metal Stamping Processes

    Weilong Hu, Jeanne He - ETA-Engineering Technology Associates, Inc.

    Basic behaviors of anisotropic properties of materials, relating to sheet metal forming processes, are discussed. The R-value is used to describe some forming problems including wrinkles and thinning failures. According to the analysis results, to point out that the anisotropic behaviors of materials affect the formability of blanks in some cases is very serious. Finally, a numerical example is presented to discuss this property further.

  • ANSA PRE PROCESSING FOR LS-DYNA

    Alexandros Kaloudis - BETA CAE Systems SA

  • Application and CAE Simulation of Over Molded Short and Continuous Fiber Thermoplastic Composite

    Helga Kuhlmann, Pieter Volgers, Zhenyu Zhang (DuPont)

    In the field of structural design, from aerospace and automotive to consumer packaging, numerical structural analysis using the finite element method (FEM) is becoming ever more important to accurately predict the performance of the considered part. In a highly competitive market, industries are demanding higher performance, improvements in fuel efficiency, increased recycling and greater safety, whether this is an airplane wing or mineral water bottle. In response to the above factors, there has been a significant increase in the application of composites. Today, finite element simulations are used extensively in the design and assessment by virtually all mayor industries. Finite element analysis (FEA) has become an integrated tool in this design and optimization. In this paper, beams constructed from over molded Short fiber Reinforced Thermoplastic on Continuous Fiber Reinforced Thermoplastics are described. One of the challenges is accurate CAE simulation of the static and dynamic behavior of the part. Model data are validated through correlation between coupon and sub-system physical tests, and further verified with results from quasi-static and impact tests. Physical test on beams confirmed good correlation between test and Finite Element Analysis.

  • Application and CAE Simulation of Over Molded Short and Continuous Fiber Thermoplastic Composites, Part I

    P. S. Kondapalli, K. Grumm (BASF Corp.)

    Short Fiber Reinforced Thermoplastics (SFRT) such as glass filled Polyamide 6 and 66 have been widely adopted as a metal replacement in a wide range of industries. The main advantage of using these materials is high strength to weight ratio, light weight, parts consolidation, easy manufacturability etc. Continuous Fiber Reinforced Thermoplastics (CFRT) are also gaining popularity because of its ability to achieve high directional stiffness/strength by tailoring the number of layers and angles. Applications which combine these two by over molding SFRT on CFRT inserts are still in its infancy. One of the hurdles is the lack of good CAE simulation capability for such applications. This paper describes the CAE tools that are developed using LS-DYNA to successfully model static and dynamic behavior of such parts. Material 58 in LS-DYNA is used for modeling the CFRT material while a User Defined Material Law models the SFRT material and they are coupled together through suitable contact definitions. Its applicability is verified through a number of examples varying from very simple to complex configurations

  • Application and CAE Simulation of Over Molded Short and Continuous Fiber Thermoplastic Composites, Part II

    P. S. Kondapalli, K. Grumm (BASF Corp.), Y. Cao (Faurecia North America), V. Laurent (Faurecia Europe)

    Automotive seating back frames for front row are mostly constructed from high strength steel in order to meet very rigorous crash requirements. The main requirements are meeting the rear impact and luggage retention behavior as specified by the standards. In this paper, seating back frames constructed from over molded Short Fiber Reinforced Thermoplastics (SFRT) on Continuous Fiber Reinforced Thermoplastics (CFRT) inserts are described. One of the challenges is accurate CAE simulation of the static and dynamic behavior of such parts. CAE tools using LSDyna were developed to model accurately the rear crash and luggage retention behavior. Designs validated through CAE analyses were used to cut the tool and build prototype parts. Physical tests on Prototype parts confirmed good correlation between the tests and FEA. They met all the required criteria without requiring any design changes.

  • Application of *MAT_258 for Bending and Crushing of Extruded Aluminum Profiles Using Shell Elements

    Jens Kristian Holmen, Joakim Johnsen (Enodo AS), David Morin, Tore Børvik, Magnus Langseth (Norwegian University of Science and Technology (NTNU))

    *MAT_258 (*MAT_NON_QUADRATIC_FAILURE) is a through-thickness failure regularization model for shells in LS-DYNA®. In this model the failure parameter is computed as a function of the size of the element as well as its bending-to-membrane loading ratio. The constitutive behavior and fracture surface in *MAT_258 are represented by well-known analytical expressions which simplify the calibration process. This means that ductile failure initiation can be predicted in thin-walled metallic structures with minimal calibration effort and cost. In this study, we go through the calibration process of *MAT_258 for two aluminum alloys before the calibrated material cards are applied in shell element simulations of double-chamber aluminum extrusions in both three-point bending and crushing.

  • Application of a Composite Material Shell-Element Model in Ballistic Impact and Crush Simulations

    Tobias Achstetter, Kelly Carney, Paul Du Bois, Cing-Dao Kan (George Mason University), Sheng Dong (The Ohio State University), Allen Sheldon (Honda R&D Americas)

    A new orthotropic material model with tabulated hardening curves for different loading directions, strain-rate and temperature dependency, damage, and a new strain-based generalized tabulated failure criterion was utilized to simulate ballistic impacts and a C-channel under crush loading. These validation simulations of the material model were performed to test the physical usefulness and robustness of the developed material model. Ballistic impact tests were chosen to highlight the capabilities of the material model in high speed impact applications. For the tested unidirectional composite material in the ballistic impact, extensive material data was available. In a recent study, Dong et al. calibrated an existing material model in crush simulations to match force-displacement characteristics of several crush experiments and a match between tests and simulations was achieved after several rounds of optimization. To highlight the capabilities of the new material model in crush load cases, its results were compared to the force-time history obtained in tests and simulations using MAT58. For both the ballistic impact and crush simulations, the same modeling approach was used.

  • Application of a Full-Field Calibration Concept for Parameter Identification of HS-Steel with LS-OPT®

    Christian Ilg, André Haufe, David Koch, Katharina Witowski, DYNAmore GmbH;, Nielen Stander, Livermore Software Technology Corporation;, Åke Svedin, DYNAmore Nordic;, Mathias Liewald, Institut für Umformtechnik, Universität Stuttgart

    In recent years results of digital image correlation (DIC) techniques have significantly improved in terms of accuracy, resolution as well as the speed of experimental strain measurement. The current availability of 2D or even 3D surface strain history during loading allows new approaches in constitutive parameter identification. In addition, localization (Fig 1.) exhibited in the numerical simulation can be integrated with DIC to identify constitutive parameters.

  • Application of Crack Propagation Simulation of Windshield to Roof Strength Analysis

    R. Chikazawa, T. Komamura, S. Yamamoto, T. Yasuki, S. Kojima (Toyota Technical Dev. Corp.)

    This paper describes a new modeling method to represent the crack propagation of windshield, namely the laminated safety glass. In the roof strength analysis used for vehicle development process, it is not easy to accurately predict crack propagation paths with existing modeling method, e.g., improving material properties. If the windshield cracks in a test using a prototype vehicle, the body deformation in the simulation and that in the test might not match, resulting in a less accurate simulation of force transfer to vehicle frames through the windshield. Therefore, prediction of crack propagation in a windshield is significant in accurately estimating the deformation and improving the accuracy of roof strength simulation results. The new modeling method to represent the crack propagation of the windshield was applied using tied overlapping shell technique, one of the modeling methods for material fracture, which has been developed by Kojima et al. The tied overlapping shell technique consists of element groups made of base elements and overlapping elements which are rotated 45 degrees in the normal direction. The base and the overlapping elements are connected using tied contact. The physical laminated safety glass windshield is constructed by placing an adhesive polyvinyl butyral (PVB) interlayer between two glass panes, outer glass and inner glass. In this study, double overlapping shell parts and a PVB interlayer part were applied to a windshield model to represent the crack propagation of the glass. Consequently the model has three layers with five mesh plates. Each part is modeled with shell elements and positioned corresponding to the neutral location of each layer thickness respectively. Four-point bending tests using specimens cut out of windshield glass were carried out to determine the critical fracture strain of glass considering the loading mode in roof strength analysis. Thereafter, application of the windshield glass model developed in this study to a roof strength analysis model was carried out to validate against test data. This paper summarized the application of new modeling method to represent the crack propagation of windshield glass in a roof strength analysis. It was found that the first two cracks propagation and the maximum force of the roof strength could be simulated. In the model the first two cracks propagated in the same shape as seen in the test. However, the number of crack propagation paths observed in the simulation was just two while there were many crack paths observed in the test. In addition, the difference in the maximum force of the roof strength between in the simulation and in the test was approximately 1%. However, after the cracks occurred, the force dropped more rapidly in the simulation than in the test. With this consideration there may be room for correction of the elimination methods.

  • Application of Digital Image Correlation to Material Parameter Identification using LS-OPT

    N.Stander (LSTC); K. Witowski, A. Haufe, M. Helbig, D.Koch, C. Ilg (DYNAmore)

    Digital Imaging Correlation (DIC) is an optical method which provides full-field displacement measurements for mechanical tests of materials and structures. It can be used to obtain temporal displacement, deformation or strain fields from an experimental coupon and can be combined with Finite Element Analysis to identify the constitutive properties of a material [1]. Because DIC-based parameter identification is an inverse process, optimization is used to obtain the parameters which will minimize the discrepancy between the measured and the computed fields. The Mean Squared Error functional typically used [1] is: f(x)=∑_(j=1)^n ‖φ_j (x)-φ ̃_j ‖^2 where φ_j (x) is a vector of nodal displacements/strains (for computation and experiment) at a number of observation points and n is the number of observation states. The functional can be augmented to incorporate global force-displacement measurements or any other functional resulting in parameter identification based on DIC. As part of this research, the DIC methodology was implemented in the LS-OPT® code utilizing the following main features: (i) multi-point responses and histories, (ii) the alignment and automatic mapping of points to an FE model. An graphical interface is provided for importing ARAMIS/GOM® (a popular commercial optical test package) test results. As a first test example, a parameter identification problem was constructed using a flat tensile bar with a hole in which the deformation field history was used as "test" input to recover the original parameters. Further parameter identification examples will be presented at the conference.

  • Application of Dynamic Relaxation in Thermo-Elastic Structural Analysis of Highway Pavement Structures

    Samir N. Shoukry, Gergis W. William, Mourad Riad - West Virginia University

    This paper describes the application of the dynamic relaxation technique implemented in LS-DYNA in analyzing large transportation structures as dowel jointed concrete pavements under the effect of temperature variations. The main feature of the pavement model is the detailed modeling of dowel bars and their interfaces with the surrounding concrete using extremely fine mesh of solid elements, while in the bridge structure, it is the detailed modeling of the girder-deck interface as well as the bracing members between the girders. The 3DFE results were found to be in a good agreement with experimentally measured data obtained from instrumented pavements sections constructed in West Virginia. Thus, such a technique provides a good tool for analyzing the response of large structures to static loads in a fraction of the time required by traditional implicit finite element methods.

  • Application of FEA in Stamping Auto Underbody Parts

    Yuyuan Wang, Marcel Pillon, Ron Ouellette, Chris Pitre, John Laporte - Canadian Engineering and Tool

    The complex auto underbody components need a long process of die design and tryout, some times need several to hundred times of costly trial-and-error to get required stamping parts. It is very critical to the die design how to decide and evaluate the die shapes of each forming stage and how to distribute the deformations between preform(s) and form for multi-stage forming. Combination of simulations for each forming stage using Dynaform and shape design using Catia can reduce the time and cost of die tryout, and make the die design optimization possible. The stampability of the part can be evaluated. The optimized die shapes and deformation distribution can be obtained. The main forming failures, such as wrinkles/double metals and cracks can be solved at die design stage. This paper attempts to show some applications of simulation techniques combined with shape design in the die design.

  • Application of FSI/ALE on Mower Grass Cutting Simulation

    Vincent Zou, John Cox (Stanley Black & Decker)

    A mower’s grass mowing quality and energy consumption are two very important factors for battery powered mower development. The challenges include developing a highly efficient cutting blade that matches with the deck for creating the ideal air flow for bagging, mulching and side discharging and consumes as little energy as possible, which, improves the battery running time. It is critical for the development engineers to understand the mower’s air flow inside the deck, the blade’s energy consumption for air flow and clippings transportation during mowing. In this paper, the LS-DYNA® FSI/ALE was used to simulate the mower mowing process. The simulation model was validated, and the result was used for improving the mower’s deck and blade design.

  • Application of LS-DYNA ® to NVH Solutions in the Automotive Industry

    Prasanna S. Kondapalli, Tyler Jankowiak (BASF Corp.), Yun Huang (LSTC Corp. Livermore)

    There are a number of powertrain applications in the Automotive Industry made of short glass fiber reinforced thermoplastics (Polyamide 6 or 66). Examples of these are Air Intake Manifolds, Cylinder Head Covers (CHC’s), Oil Pans etc. Assessment of NVH (Noise, Vibration & Harshness) characteristics using simulation tools is a critical requirement for such applications. Modal analysis, steady state dynamic analysis and acoustic analysis are some of the CAE (Computer Aided Engineering) analyses that are required. LSTC has developed a range of tools within LS-DYNA to carry out such analyses. In this paper, these capabilities are explored for various NVH analyses of automotive components. Examples of modal analysis and steady state dynamic response using the finite element method (FEM) are given and compared with other standard software. Boundary element methods (BEM) are well suited for doing acoustic analyses because of its requirement for modeling only the boundary of a vibrating body. Both the direct and the indirect boundary element methods are implemented in LS-DYNA. Examples using both methods are shown. Various options existing within these methods are also discussed. Post processing of acoustic quantities are demonstrated.

  • Application of LS-DYNA and MADYMO Coupled Model for Simulating an Offset Frontal Crash Scenario

    Gunasekar T. J., Mostafa Rashidy - EASi Engineering, Norman Ludtke - Ludtke and Associates, Bruce Spinney - NHTSA

    A full vehicle finite element model of the 1995 Chevrolet Lumina validated in full frontal impact was used to simulate a frontal offset impact. The tibia index injury criteria set forth in the European Directive 96/79 were used to assess the injury indices of the occupant in frontal offset computer simulation. Based on the injury predictions from the baseline model, a structural modification to vehicle was made in order to reduce the tibia index. In the modified vehicle model simulation, the tibia index of the occupant was found to be reduced from 1.13 to 0.73 for the right tibia and from 0.62 to 0.45 for the left tibia.

  • Application of LS-DYNA  in Structural Fatigue Analysis and Post-Processing with LS-PrePost 

    Yun Huang, Zhe Cui, Philip Ho, Chengju Zhang (LSTC)

    This paper provides a review of the development of LS-DYNA in structural fatigue analysis and the post-processing of the results with LS-PrePost. Fatigue is the progressive and localized structural damage that occurs when the material is subjected to cyclic loadings. Fatigue damage and failure are very common in industries. Some studies have suggested that over 80% of all mechanical failure of metal are attributable to fatigue. Starting from 971 R7 version of LS-DYNA, a series of features have been implemented in LS-DYNA to provide fatigue and durability analysis for metal structures, under various vibration loading conditions. The analysis provides accumulative damage ratio, expected fatigue life and cycles for the structures, based on the Palmgren-Miner rule and material’s S-N curve. With the recent updates in LS-PrePost (4.2, 4.3), a new interface has been added to provide the fringe plot of the fatigue variables, which greatly simplifies the post-processing of the results and makes the result analysis easier. Some examples are provided to demonstrate the effectiveness and convenience in running LS-DYNA and LS-PrePost for fatigue analysis and results post-processing.

  • Application of LS-DYNA in Identifying Critical Stresses Around Dowel Bars

    Samir N. Shoukry, Gergis W. William, Mourad Riad - West Virginia University

    A detailed 3D Finite Element (3DFE) Model is developed to examine the triaxial state of contact stress that develops around the dowel bars due to both traffic and thermal loads. Dowel bars are modeled using 8-node solid brick elements. Sliding interfaces with friction that permit separation are modeled along the full cylindrical surface between each dowel and the surrounding concrete. The model results are validated through comparison with laboratory measured strains in dowel jointed concrete specimens. The model results reveal that under the standard axle load, tensile stresses of magnitude sufficient to initiate localized concrete failure may develop in the concrete surrounding the loaded dowel. Such stresses are responsible for initiating cracks in the concrete that lead to the rapid joint deterioration.

  • APPLICATION OF LS-DYNA IN NUMERICAL ANALYSIS OF VEHICLE TRAJECTORIES

    Jerry W. Wekezer - FAMU-FSU College of Engineering, Krzysztof Cichocki - Technical University of Koszalin

    Errant vehicles may pose a serious threat to neighboring traffic of pedestrians, bicyclists, and even to their drivers in a densely populated urban environment. Accident reconstructions have indicated that street curbs do not offer any meaningful protection against errant vehicles, which can easily traverse street curbs even at small velocity and shallow angles. The paper presents research results of a study, in which computational mechanics was utilized to predict vehicle trajectories upon traversing standard Florida DOT street curbs. Computational analysis was performed using LS- DYNA computer code and two public domain, finite element models of motor vehicles: Ford Festiva and Ford Taurus. The suspension systems of the original vehicle models were evaluated and additional suspension components were identified and developed. The finite element models of the required suspension systems were developed using geometry from the actual suspension parts, captured using a digitizing arm. Due to complex geometry of these parts, the MSC-PATRAN preprocessor was used to create data for LS-DYNA code. Shock absorbers were modeled using discrete spring and damper elements. Connections for the modified suspension systems were carefully designed to assure proper range of motion for the suspension models. Inertia properties of the actual vehicles were collected using tilt-table tests and were used for LS-DYNA vehicle models. A standard FDOT street curb model was developed using rigid wall option in LS-DYNA. Initial, computational mechanics analyses suggest that vehicles tend to retain larger amount of their kinetic energy after traversing street curbs. It is therefore dangerous to anticipate that performance of street curbs would be comparable with that demonstrated by guardrails. In order to validate the assumed discrete numerical models and the results of LS-DYNA analyses, full-scale experimental tests have been performed at Texas Transportation Institute. Two types of vehicles have been tested: Ford Festiva and Ford Taurus, both for two values of approach angle: 15 and 90 degrees, with impact velocity of 45 mph. Experimental results including accelerations, displacements and overall vehicles behavior were registered by high-speed video cameras and have been compared with numerical results and computer animations. Verification results indicated a good correlation between computational analysis and full-scale test data. The study also indicated a strong importance of properly modeled suspension and tires on resulting vehicle trajectories. The major goal of the research was to study the behavior of various vehicles (from small Ford Festiva to pickup truck Chevrolet C2500), for different approach angles, velocities and curb profiles. Experiences gained in preliminary numerical analyses and experimental tests allow studying a matrix of critical cases without time- consuming and costly additional experimental testing.

  • Application of LS-DYNA SPH Formulation to Model Semi- Solid Metal Casting

    F. Pineau, G. D’Amours - National Research Council Canada, Aluminium Technology Centre

    Semisolid metal alloys have a special microstructure of globular grains suspended in a liquid metal matrix. This particular physical state of the matter can be exploited to produce near-net-shape parts with improved mechanical properties. Indeed, semi-solid processes take advantage of a much higher apparent viscosity of the die cast materials by limiting the risk of oxide formed on the free surfaces to become incorporated into the casting when the material is injected into the die. Semi-solid processes that use billets as feedstock material are however tied up with an additional type of surface contamination. During the injection phase, the external-skin on the periphery of the billet, which has been in contact with air and lubricant during the transfer in the shot sleeve may be incorporated into the casting. This can be an important cause of reject for most structural parts in the automotive industry. In order to predict and control the occurrence of skin inclusion into cast parts during the injection phase of semi- solid processes, Lagrangian methods are appropriate. Indeed, the skin, composed of contaminated or even partially solidified metal, has different mechanical properties compared to the core of semi-solid aluminum. Abitrary- Lagrangian-Eulerian formulations, which can account for the coupling between the “solid” skin and the flow of “semi-solid” aluminum are promising but still necessitate a huge amount of computer power. On the other hand, particle based Smoothed Particle Hydrodynamics (SPH) approaches are particularly well suited to this kind of flows involving complex flow behavior and solidification. These methods are able to track accurately free surface flows with fragmentation and break up as well as to follow the advection of oxides through the flow. In this paper, a first analysis is performed in order to investigate the potential of the SPH solver of LS-DYNA to deal with the problem of skin inclusion in semi-solid die casting processes. Preliminary results show that the SPH approach is a very promising simulation tool to follow the skins during semi-solid injection casting.

  • Application of LS-DYNA for Auto NVH Problems

    Yun Huang, Zhe Cui (LSTC)

    NVH (Noise, Vibration and Harshness) is an important topic for the design and research of automotives. Increasing demands for improved NVH performance in automotives have motivated the development of frequency domain vibration and acoustic solvers in LS-DYNA. This paper presents a brief introduction of the recently developed frequency domain vibration and acoustic solvers in LS-DYNA, and the application of these solvers in auto NVH problems. Some examples are given to illustrate the applications.

  • Application of MADYMO Occupant Models in LS-DYNA/MADYMO Coupling

    Happee R., Janssen, A.J., Fraterman E., Monster J.W. - TNO Automotive

    The LS-DYNA – MADYMO coupling has been extended so that users gain maximal flexibility in their choice of software and models. Where the traditional coupling allowed only MADYMO ellipsoids and planes to contact entities in the coupled code, now contact can also be defined with MADYMO FE. This enables state of the art MADYMO dummy models, subsystem models, barrier models and human models to be applied in the coupling with LS-DYNA.

  • Application of Model Order reduction Techniques in LS-DYNA

    P. Friedrich (SCALE)

  • Application of New Concrete Model to Roadside Safety Barriers

    Akram Abu-Odeh - Texas Transportation Institute

    The subject of roadside safety has been seeing a healthy growth in the use of nonlinear finite element analysis in designing and analyzing roadside hardware systems. Some factors that helped researchers include the expanded capabilities of LS-DYNA commercial finite element code, the availability of several public domain vehicle models and the availability of material models explicitly built and modified for roadside safety applications. One of these new material models is *MAT_CSCM (and the short input version *MAT_CSCM_CONCRETE) incorporated in LS- DYNA version 971 as material type 159. Material model *MAT_CSCM which was developed by APTEK INC. is a continuous surface cap material model with the ability of capturing concrete material behavior using minimal input like the compressive strength of concrete and maximum aggregate size. In this paper two examples of using LS- DYNA to simulate impacts with concrete barrier are presented. They are two different pendulum simulations of a concrete parapet with a steel railing on top. The deformation and damage profiles along with the force time history were used as measures for comparing tests and simulations. Both examples indicate a reasonable correlation between tests and simulations. Figure 1a shows the response of the concrete parapet as tested and figure 1b shows the response calculated from the LS-DYNA simulation.

  • APPLICATION OF NON-DETERMINISTIC METHODS TO ASSESS MODELLING UNCERTAINTIES FOR REINFORCED CARBON-CARBON DEBRIS IMPACTS

    K. Lyle - NASA Langley Research Center, Hampton VA, E. Fasanella - ARL-VTD Langley Research Center, Hampton VA, M. Melis and K. Carney- NASA Glenn Research Center, Cleveland OH, J. Gabrys -The Boeing Company, Philadelphia PA

    The Space Shuttle Columbia Accident Investigation Board (CAIB) made several recommendations for improving the NASA Space Shuttle Program. An extensive experimental and analytical program has been developed to address two recommendations related to structural impact analysis. The objective of the present work is to demonstrate the application of probabilistic analysis to assess the effect of uncertainties on debris impacts on Space Shuttle Reinforced Carbon-Carbon (RCC) panels. The probabilistic analysis is used to identify the material modeling parameters controlling the uncertainty. A comparison of the finite element results with limited experimental data provided confidence that the simulations were adequately representing the global response of the material. Five input parameters were identified as significantly controlling the response.

  • Application of Scrap Shedding Simulation in Stamping Manufacturing

    Diane Xu - Ford Motor Company, Jim Kosek - Engineering Technology Associates, Inc.

    One of the most critical issues in stamping manufacturing today is the successful shedding of scrap from limited trim dies. Until recently, die tryout was the first opportunity to check the shed scrap feasibility of a trim die. The newly developed scrap shed analytical module can be used for analyzing trim die scrap shed feasibility before die creation. It simulates Scrap shedding during or after the die is designed using Dynaform and LS-DYNA®. Scrap shedding simulation offers die designers and manufacturers the opportunity to closely examine a trim die’s performance before die construction. With today’s tighter die design timelines and reduced number of dies in manufacturing, it is more critical than ever to establish trim die design integrity as early as possible in the design process. This can be achieved through Dynaform scrap shedding simulation. Dynaform scrap shedding uses a flexible body approach to simulate the exiting of scrap from the workstation. This allows for full interaction of all essential variables and forces acting on the die and sheet metal part. It allows for a real world simulation that calculates the effect of any changes in die speed, initial velocity, material properties or die design. Various trim operations, such as direct and cam trim, can be very easily simulated. Once a design defect is found, possible solutions can also undergo a virtual tryout in the Scrap Shedding simulation. It has a great impact on cost and timing when used in stamping engineering, and can be used to avoid the pitfalls of defective die design.

  • Application of Shell Honeycomb Model to IIHS MDB Model

    Shigeki Kojima - TOYOTA TECHNICAL DEVELOPMENT CORPORATION, Tsuyoshi Yasuki, Koji Oono - Toyota Motor Corporation

    This paper describes a new finite element modeling method of Aluminum honeycomb using shell elements. It is our new modeling method that cell size of honeycomb structure is enlarged to increase time step size for FEM analysis, and compressive strength is controlled by thickness of shell elements. New modeling method was applied to IIHS moving deformable barrier model, and side impact analysis with a full vehicle model was performed. The result of simulation using a new barrier model showed much better correlation with a test result than previous simulations.

  • Application of SynfiniWay Grid Platform for iterative LS-DYNA studies

    E. Deguemp - Fujitsu Systems Europe, M. Adoum, V. Lapoujade - CRIL Technology

    Whether end-users need to access local or remote systems, to use a batch system or to run jobs interactively, they will always raise the same questions: “Which system can I run my job on?” and “How do I get data to the machine where my job will execute?” Users should only need to know what applications they want to run and where the inputs for these applications are located. To answer these needs, Fujitsu markets a middleware product called SynfiniWay which hides all issues related to CPU location, and allows execution of complex applications via workflows. The conclusion of this paper is that the SynfiniWay middleware can solve LS- DYNA iterative problems: the search for an optimal mesh size or successive LS- DYNA calculations with modified initial conditions. SynfiniWay provides an infrastructure to execute these studies automatically and transparently on remote computers (grid computing).

  • Application of the Discrete Elements Method to Frequency Analysis and Use of the “Bond” Method for Fracture Modeling

    Tess Legaud, Edith Grippon,Vincent Lapoujade (DynaS+), ierre-Louis Chiambaretto, Yves Gourinat (Université de Toulouse)

    Nowadays more and more complex mechanical behaviors have to be modelled. In order to do so, the generally used numerical methods, like finite elements, show some limitations. Particularly, finite elements’ ability to model granular media is reduced, partly because of the contact handling complexity between each grain. One of the alternatives is to use meshless methods. Within the software LS-DYNA ® , there notably exists a meshless method named “Discrete Element Method” (DEM). This method was initially implemented in the software to model granular media, and especially granular flows, where the displacements of each particle are deduced from Newton’s equation [1]. An extension of the method consisting in bonding particles together with smooth heterogeneous bonds essentially permits to model fracture (DEM-HBOND), which is a significant issue in many fields. Our studies consist in two disconnected projects presented below: As part of the Midi-Pyrénée project “TANKYOU”, we are trying to find a granular material that would have the same vibratory behavior as a fluid. In order to do that, we have especially been seeking the mode shapes of a cylinder fully filled with Discrete Element Spheres (DES). The issue here is to vibrate DES with explicit calculations. As part of an internship, a tensile test on a DES steel specimen has been performed to test fracture modeling. The impact of particles’ organizations (meshes) in the specimen has been studied, and results have been compared with finite elements results.

  • Application of the SPH Finite Element Method to Evaluate Pipeline Response to Slope Instability and Landslides

    A. Fredj, A. Dinovitzer (BMT Fleet Tech-nology), M. Sen (Enbridge Pipelines)

    Buried pipelines operating on active slopes can be subject to lateral and axial loads resulting from slope instability and landslides. The techniques to predict pipeline displacements, loads, stress or strains are not well described in design standards or codes of practice. Finite element analysis based soil-pipe interaction simulation has developed in recent years and is proving to be a useful tool in evaluating the pipeline behavior in response to slope movement. A description of the BMT pipe soil interaction modeling techniques, their validation against full scale trails and comparison to spring support models has been previously published.

  • Application of the SPH Method for Simulation of Aerospace Structures under Impact Loading

    M-A Lavoie, A. Gakwaya1 - Laval University, Cité Universitaire, Quebec, Canada, M. Nejad Ensan - National Research Council, Ottawa, Ont. Canada.

    The SPH method is applied in industrial level problems as encountered for example in studies related to bird impact on composite aircraft structures. This paper first demonstrates the accuracy of the method for bird impact on rigid target modeling and then applies the developed model to a more complex problem, namely the secondary bird impact.

  • Application of Topology Optimization for Crash with LS-OPT/Topology

    Heiner Müllerschön, Katharina Witowski - DYNAmore GmbH, Nikolay Lazarov - University of Karlsruhe

    Since end of 2009 a new software tool LS-OPT/Topology is available from LSTC. With LS-OPT/Topology nonlinear topology optimization with LS-DYNA can be applied for static and even for dynamic problems. The underlying method is Hybrid Cellular Automata (HCA) which is a heuristic, gradient-free approach. The objective is to obtain a structure with uniform internal energy density subject to a given mass fraction. In the current version LS- OPT/Topology-1.0, topology optimization with hexahedron solid elements, material *MAT_024 and some established contacts is possible for single and for multiple load cases. In this paper, first experience with the HCA-methodology and the application of LS-OPT/Topology to industrial problems is demonstrated. Capabilities and limitations of the new implementation will be highlighted.

  • Applications of ICFD / SPH Solvers by LS-DYNA to Solve Water Splashing Impact to Automobile Body

    G. Wang, E. DeHoff (Honda); F. Del Pin, I. Caldichoury, E. Yreux (LSTC); K. Gardner (Ohio State University)

    When a vehicle runs at high speed on a watery or muddy road, the high speed splashing generated by tire rotation often causes damage to the underbody panels. This is a challenging dynamic FSI (fluid-structure interaction) problem for Honda to consider. ICFD and SPH are two powerful solutions used in FSI applications, especially for high speed flow and with dynamic free surface evolution. This paper presents some FSI solutions of water splashing of automotive components by using ICFD and SPH solvers from LS-Dyna.

  • Applications of ICFD solver by LS-DYNA in Automotive Fields to Solve Fluid-Solid-Interaction (FSI) Problems

    G. Wang, P. Rodriguez, J. Tippie, S. Smith (Honda R&D Americas); F. Del Pin, I. Caldichoury (LSTC)

    Fluid-solid interaction (FSI) becomes a more and more important and wider application field in the automotive industry. It is challenging to CAE engineers to predict performance of complicated systems under high speed flow and with dynamic free surface evolution. This paper presents the three following FSI accomplishments in the power sports field by using ICFD solver from LS-DYNA®.

  • Applications of LS-DYNA in Electronics Products

    Hanks Hsu, Brian Hsiao - Flotrend Corporation

    Portable electronic devices have become smaller and lighter but they are also easily damaged during accidentally drop situation. Therefore, new electronic products are usually needed to pass requirements of shock and drop test before actually delivering to customers. FEM simulation provides engineers a useful and powerful approach to identify the potential weakness of products before the prototype is even made. The report will introduce the applications of the Ls-dyna in a virtual lab which simulates the experiment conditions of shock and drop tests in computers. It also shows Ls-dyna can be a very effective tool for engineers to improve the performance of their design in the shock and drop test.

  • APPLICATIONS OF LS-DYNA TO STRUCTURAL PROBLEMS RELATED TO RECOVERY SYSTEMS AND OTHER FABRIC STRUCTURES

    Benjamin A. Tutt, Anthony P. Taylor - Irvin Aerospace Inc.

    Irvin Aerospace Inc., has used the LS-DYNA Explicit Finite Element Analysis (FEA) tool for over five years for the analysis of static and dynamic fabric problems. The References provide many examples of this previous work. Our first application was the analysis of airbag landings for several spacecraft programs, including Reusable Launch Vehicles (RLV’s), various Unmanned Air Vehicles (UAV’s), Military Airdrop Systems, and planetary exploration systems. These are all covered in the references. This paper presents some current results along the lines of the above, and other recent developments. These include an air beam supported structure, which was evaluated for both snow and wind loads, and a fabric blanket system that was somewhat optimized by a combination of FEA analysis and testing. While these applications appear rather bland, the air beam structure is designed to house military fighter and rotary aircraft and must withstand significant snow and wind loads. The blanket system is used to constrain a target-missile that performs a unique ‘Air Launch’ mission, involving extracting the target from a cargo aircraft and allowing it to stabilize prior to release and ignition.

  • Applications of Multiscale and Subcycling methods for Press Hardened Steel Parts Failure Assessment

    Y. Drouadaine (ArcelorMittal)

    Press Hardened Steel (PHS) parts, like B-pillar made of Usibor® 1500, are today the best steel solutions in order to fulfil the most aggressive crash requirements with the lowest body structure mass. However, these severe crash conditions request a failure risks analysis during the vehicle design process. The usual Usibor® 1500 failure modelling method proposed by ArcelorMittal always remains compatible with a current full car model mesh size, whether for base metal or spot-weld Heat Affected Zone (HAZ) or laser welded line. Shell elements in the mesh size range 3 mm – 5 mm are used with CrachFEM fracture criterion. One alternative, for an improved failure risk prediction, would be to use a meso-scale model with solid element mesh size less than 0.5 mm for the most critical areas. This method leads to a heterogeneous model when used in a full car crash simulation (finest 3D elements to 2D elements mesh size ratio close to 10 times). In this case, the time step is imposed to the whole model by the smallest elements. This may lead either to increase drastically the CPU time or to provide results affected by an excessive added mass level in case of a too ambitious imposed time step. LSTC and DYNAmore have recently developed (2014) new features like Subcycling - *CONTROL_SUBCYCLE_K_L - and Multiscale - *CONTROL_SUBCYCLE_MASS_SCALED_PART_{SET} - in order to reduce the calculation time without adding a huge amount of mass. It seemed interesting to use these new features in the field of heterogeneous crash models without none of the two time-step issues previously mentioned. The present paper will describe results obtained by these new features, especially the multiscale option. It is applied to different mesh size heterogeneous models, from a three points bending test on a specimen till a full car model during side impact. Energy balance stability, parts deformation, local plastic strain will be presented and compared with the ones obtained by the unique time-step reference calculation. A CPU time performances comparison will be also presented and then, the multiscale method efficiency will be established for each tested model. The elapsed time saving reaches 34% in case of a 3D local failure analysis performed on a full vehicle during side impact, without any negative impact on the quality of results. Current limitations of heterogeneous models, questions and expectations regarding the multiscale approach and the 3D-2D transition modelling will be also discussed to conclude the presentation.

  • Applications of the new magnetostatic solver/ AMS preconditioner in LS-DYNA®

    M. Duhovic (TU Kaiserslautern), I. Caldichoury, P. L’Eplattenier, T. Nguyen (Ansys/LST), J. Hausmann (TU Kaiserslautern), L. Kielhorn, T. Rüberg, J. Zechner (Tailsit)

    Previous implementations of LS-DYNA’s EM module have relied on an explicit scheme, requiring very small time-step sizes and therefore long simulation times. Recently, a new magnetostatic solver/ AMS preconditioner has been developed in LS-DYNA®. Unlike the current implementation, the new solver is unconditionally stable with respect to the time-step size and allows for the handling of materials with high permeability and low electrical conductivity. In this paper, the capabilities of the new solver is tested on the use-case of carbon fiber reinforced thermoplastic composite (CFRTPC) laminate induction heating using magnetic flux concentrators/field formers. In the current work, induction heating characterization experiments were performed on carbon fiber poly(ether ether ketone) (CF/PEEK) laminates using two different coil geometries.

  • Applying Buried Mine Blast Loads to a Structure Utilizing the User Module Capability

    E. Lazerson, H. Raz, Z. Asaf (Plasan SASA)

    Developing armored vehicles to withstand a buried mine blast is a challenging task. The development of solution with optimum trade-off between mobility and survivability cannot be done by trial and error alone. The development of reliable CAE model of the vehicle and threat, using a simulative tool, is essential. In the early design phase, extensive use of simulation is done to optimize the structure. This process requires a short turnover time for the simulations. Use of ALE or Particle Blast can give good results but involves long runtimes. On the other hand, using Load Blast (ConWep) or Initial Impulse Mine is fast and simple. Initial Impulse Mine works by applying initial velocity on selected elements. The unselected elements have initially zero velocity. This velocity discontinuity can lead to unreasonable results. The aim of the Load Blast is to simulate an air blast but not buried mines. It is possible to calibrate Load Blast to get the correct peak pressure or the local impulse, but not both. It is impossible to change Load Blast spatial pressure distribution. In this work a new user-defined module was implemented. This ConWep-like user loading enables the simulation of a buried mine explosion by modification of pressure distribution via a shape function. Using this technique a better pressure and momentum distribution over the target can be achieved with running times similar to *LOAD_BLAST_ENHANCED (ConWep). The new module is implemented in FORTRAN and activated using the *USER_LOAD_SEGMENT keyword. The compiled module is activated in the LS-DYNA® deck by using the new *MODULE_LOAD keyword. The use of the new solvers with dynamic loading of modules enables our simulation team members to use this code easily and to issue new versions of the module as needed.

  • Applying Digital Image Correlation Methods to SAMP-1 Characterization

    Hubert Lobo, Brian Croop, Dan Roy (DatapointLabs, USA)

    SAMP-1 is a complex material model designed to capture non-Mises yield and localization behavior in plastics. To perform well, it is highly dependent on accurate post-yield material data. A number of assumptions and approximations are currently used to translate measured stress-strain data into the material parameters related to these inputs. In this paper, we look at the use of direct localized strain measurements using digital image correlation (DIC) as a way to more directly extract the required data needed for SAMP-1

  • Applying the Dynamic Relaxation Step to Determine Influence on Global Model Response from Shock Tube Loading for Mounted Hybrid III Head Neck Assembly

    Emily Ward, Tim Harrigan - The Johns Hopkins University

    Blast-induced traumatic brain injury (bTBI) is a critical issue for warfighter protection. Since bTBI has many features in common with injuries due to impact loading, the Hybrid III crash test dummy can be used to study many aspects of this injury, and the head-neck assembly of the Hybrid III dummy can provide a relevant initial bench test for computational studies of traumatic brain injury. LS-DYNA® has provided finite element models (FEM) of various Anthropomorphic Test Dummies (ATDs), and in this study the head-neck subassembly from the LSTC- NCAC 50th% Full FE H-III Dummy was used. To study the effects of blast on the head a shock tube experiment was simulated and the relevant loading conditions were applied to the head-neck assembly of the Hybrid III dummy FEM. The results were then compared to similar experimental test data. Since the initial tension in the neck cable of the Hybrid-III head-neck assembly is a key factor in the experimental response, simulating the initial tension in the neck cable is required in order to maintain a consistent boundary condition for the model. The neck cable definition in the Hybrid-III FEM was modified to include an initial stress, which was implemented using a dynamic relaxation step applied to initialize the model. The dynamic relaxation step is applied using explicit techniques and a sensitivity study is explored to understand impact of the initialization on the global response. The relative influence on the resulting global behavior response depends on the loading conditions.

  • Approach for Modelling Thermoplastic Generative Designed Parts

    F. Althammer (Daimler/University of Stuttgart), D. Moncayo (Daimler), Prof. P. Middendorf (University of Stuttgart)

    This study presents an approach to characterize thermoplastic generative designed parts and compares the usability of different material models in LS-DYNA. For using 3D printed parts in prototypes it is at first necessary to be able to predict the deformation behaviour of the printed part itself. The deformation behaviour of thermoplastics and especially of thermoplastic generated parts depends on a variety of material properties. In general the parts have a composed anisotropy consisting of the process and material anisotropy. The process anisotropy is reflected to different mechanical properties due to the building directions of the 3D printer. The material anisotropy includes divergent tension and compression behaviour and approximately orthotropic behaviour due to particle reinforcement. The main task therefore is to evaluate current material routines and modeling techniques to ensure the predictability of the parts behaviour with available and implemented material cards. The performed characterization consists standard specimen tests for a non-reinforced and a carbon particle reinforced thermoplastic, which is produced in the selective laser sinter process. The conducted tests are a tensile, a compression and a shear test. The test specimen were built in different construction directions. In addition, component tests were executed in order to evaluate the predictability of the generated material cards in multiaxial stress states.

  • Armor Steel Impacted by Projectiles with Different Nose Shapes – Numerical Modelling

    T. Fras, N. Faderl (French-German Research Institute of Saint-Louis), C. C. Roth, D. Mohr (ETH Zurich)

    The presented experimental investigation concerns 3 mm thick target plates impacted by strikers with different noses at velocity close to 300 m/s and is conducted to gain an insight into mechanisms of deformation and fracture characteristic for a high strength high hardness armour steel, [1]. Guaranteed by the producer yield strength and ultimate tensile strength of the steel are 1300 MPa and 2200 MPa, and the hardness is within 600 – 640 HB, [2]. Due to impacts, the projectiles and targets, both extracted from the armour steel, are severely deformed and fractured. Numerical simulations of the performed test are carried out using the explicit solver of the finite element software package LS-Dyna R9.0.1. The model used in the simulation implemented through the user material subroutine accounts for a yield function with a non-associated flow rule, a Swift–Voce strain hardening law and Johnson–Cook type of multipliers with the effects of strain rate and temperature. The stress-triaxiality, Lode angle parameter and strain-rate dependent Hosford–Coulomb fracture initiation model is employed to predict a steel failure, [3-4].

  • ASPECTS OF SEAT BELT MATERIAL SIMULATION

    C. Pedrazzi, K. Elsäßer, S. Schaub - TRW Occupant Restraint Systems GmbH & Co. KG

    The so-called D-ring dynamic overturning is an instability phenomenon occurring occasionally during car crashes. It can have a negative effect to the restraint function of the seat belt system and lead to increased seat belt forces to the occupant. In order to avoid this phenomenon the influence of different parameters has to be investigated. Therefore a simulation model has been created, using the Finite Element Code LS-DYNA 3D. Major questions to be clarified in this context are: • Define initial geometry for the belt running through the D-ring. • Choice of appropriate material model. • Influence of physical parameters, i.e. D-ring geometry, friction properties, belt material, belt forces, crash pulse, etc. The definition of the initial geometry and a feasibility study have been presented at the 2000 CAD-FEM conference [2]. The modelling method, results for a given baseline geometry, variations in different material models and the pre-simulation of a new concept of the D-ring, the so called “roller D-ring” are presented in the current paper.

  • Assembly of full-vehicle digital crash models using ANSA techniques

    A. Kaloudis (BETA CAE Systems)

    The level of complexity of the full-vehicle digital crash models varies between car manufacturers. Undoubtedly, however, it is very high and the trend is to become higher and higher, due to the fact that the development teams want their models to include even more details. During all these years a standard technique, that has become of common use, is the fragmentation of the full-vehicle model into *INCLUDE files. Each one contains a distinct physical subassembly of the vehicle, which we shall subsequently name module. This technique offers various advantages, but definitely sets a challenging task. That of connecting the modules to each other and assembling them into a full-vehicle model. Using the embedded capabilities of ANSA we have created processes and tools that enable : i) fast and robust intermodular connections represented by various element types, ii) efficient and reliable integrity check of these connections, iii) the assembly of multi-variant modules, iv) inspection of the connection areas in a lightweight view, v) an error-free update of modules’ versions, vi) the overview of the modules participating in the full-vehicle models with aid of graphs, vii) the reusability of already existing models, as the basis for the creation of new ones.

  • Assessing and Validating the Crash Behavior of Securalex®HS, a High-Strength Crashworthy Aluminum Alloy, Using the GISSMO Model

    Callum J. Corbett, Laurent Laszczyk, Olivier Rebuffet (Constellium Technology Center)

    Specialized aluminum alloys play an ever increasing role in today’s automotive industry. The desire for lightweighting is driven by both performance aspects as well as the legislative framework regarding emissions and fuel efficiency. Using aluminum rolled products for structural car body parts requires good formability and high mechanical properties paired with predictable and safe performance under crash loading. Simulating and predicting the crash behavior requires a detailed material model including damage and failure. To this extent, a vast range of experiments are performed on Securalex ® HS samples. The relevant state of the material is the in-service temper, so that a heat treatment is applied to all samples prior to testing. In order to compare the simulation results to the experiments, digital image correlation techniques are used to measure strains on the specimen surfaces during testing. After calibrating the plastic material response, a detailed failure model is required. Using the GISSMO model, an equivalent plastic strain to failure curve depending on stress triaxiality is defined. It is parametrized with three variables and coupled with an optimizer based on the simplex method. By defining suitable error functions based on the simulation results, it is possible to optimize the failure curve and obtain a good correlation with the experiments. The final step lies in validating the failure model. To this end, the calibrated model is used to simulate and predict the deformation and crack initiation during the quasi-static axial crush of a square profile. The results are compared to experiments done on two-piece friction-stir welded boxes.

  • Assessing Options for Improving Roadside Barrier Crashworthiness

    D. Marzougui, C.D. Kan, K.S. Opiela (George Mason University)

    The introduction of new crash test requirements raises questions about the efficacy of commonly used barriers that had been accepted under earlier test requirements. Seven commonly-used barriers were crash tested under the new MASH requirements in a recent NCHRP project. Three of the barriers tested did not meet the new requirements for the test with the 2270 kg vehicle. While the implementation of the MASH standards does not require hardware that passed the previous NCHRP 350 requirements to be re-evaluated, there is an interest in knowing whether these devices can be modified to meet the more stringent MASH requirements by DOTs. In another effort, these seven NCHRP crash tests were successfully simulated to provide an extended validation of the new finite element model of a Chevrolet Silverado pick-up truck as a surrogate for the 2270 kg test vehicle. This provided the opportunity to, among other things, evaluate the potential of various retrofit options for improving two of the three barriers that failed. An analyses of six modifications for the G9 Thrie-beam barrier and three variations of the G4(1S) guardrail median barrier was undertaken. A summary of the testing and simulation modeling of the two tests is presented as the basis for the simulation of modified versions of the barriers. The evaluation results are presented for each of the retrofit options and recommendations offered.

  • Assessing the Convergence Properties of NSGA-II for Direct Crashworthiness Optimization

    Guangye Li - IBM Deep Computing Group, Houston TX, Tushar Goel, Nielen Stander - Livermore Software Technology Corporation

    The elitist non-dominated sorting genetic algorithm (NSGA-II) converges to the Pareto optimal front (POF) if a sufficient number of function evaluations are allowed. However, for expensive problems involving crash simulations, only a limited number of simulations might be affordable. It is observed that initially there are significant advances towards the POF but as the population matures, the improvements are relatively small. This means that one can probably limit the computational expense by terminating the search at the right point. The paper also demonstrates a successful use of IBM cluster for parallel processing that significantly reduces clock time for optimization.

  • Assessment of Abdominal and Skeletal loadings and Kinematics during Frontal Impacts through a Novel Tool for HBM Variants Generation Based on the Occupant’s BMI

    Zouzias D, Fokylidis A, Lioras A, Rorris L

    HBM variant generation tools are solely based on morphing techniques to adjust the shape of the external surface to a target depending on the BMI of interest. Even though this approach can quickly produce HBM variants, downgrades the model’s mesh by stretching the elements and compromising their quality. Furthermore, the dependence of the abdominal organs morphology on the occupant’s BMI is rarely, taken into account. This paper presents a novel tool for automatic HBM variant generation, that respects elements’ quality taking also into account the volume of the abdominal organs.

  • Assessment of Automotive Panel to Meet Handling Load Requirements: CAE Simulation

    Harihar Kulkarni, John M. Eidt - Ford Motor Company, Dharmveer Podhuturi, Akbar Farahani - Engineering Technology Associates, Inc.

    Material handling of sheet-metal components within the plant or one plant to the other significantly impacts quality and assembly process. Any permanent deformation of sheet metal component contributes to poor quality of an automotive subassembly. One way is to minimize occurrence of unacceptable deformation is to follow trial and error approach. However, such approach is time consuming during launch; in addition cost of stamping and testing prototype panel is high. Therefore a CAE methodology, using dynamic time domain solver ‘LS-DYNA’, was developed to provide design guidance and to examine probability of permanent set in the panel due to manual and robotic handling loads. An outer panel of a liftgate is used as an example to establish this methodology. The CAE results confirmed that proposed design of outer panel is capable to meet handling loads and eliminated need of redesign and saved launch time. This paper discusses a methodology to simulate handling process and evaluate behavior of sheet metal panels subjected to time varying enforced displacements. In this approach FEA techniques and a nonlinear flexible dynamic model are combined. Such approach helped to simulate handling process and to assess relations among material strength, panel topology, and locations of suction cups in end-effectors. Experimental validation of this proposed technique is in progress.

  • Assessment of LS-DYNA Scalability Performance on Cray XD1

    Ting-Ting Zhu - Cray Inc.

    Technologists worldwide have now recognized that CAE (Computer Aided Engineering) offers an unprecedented opportunity to revolutionize product development. Today, CAE promises not only increased productivity but also faster time-to-market, lower warranty costs and above all, products that are safer, outperform and work better. With the broad acceptance of the MPI based implementation of LS-DYNA, the manufacturing industry is pushing the limits of scalability as they scramble to meet stringent product design cycle constraints. Microprocessor based cluster systems are increasingly being deployed for production workloads. But, the scalability and system efficiency can be very poor on such systems. The industry goal to reduce time-to-market can be met only if the system has a balanced architecture and the interconnect technology is able to deliver sustained performance for actual applications. In this study, an in-depth analysis will be performed to assess the performance of LS-DYNA on Cray’s XD1 system. A correlation between the hardware features of Cray XD1 and the attributes of LS-DYNA will be made. Various phases involved in a typical crash simulation, such as - initialization, element processing, contact and rigid bodies calculations will be analyzed. An MPI profiling tool will be used to monitor the MPI performance in the context of computation, communication and synchronization aspects of LS-DYNA. The communication patterns and message sizes will be studied for variety of standard benchmarks ( www.topcrunch.org ). The role of Cray XD1’s balanced architecture and the HHTUTU UUTTHH high speed interconnect technology will be presented in the specific context of LS-DYNA and production workloads. Performance results of LS-DYNA on Cray XD1 will be highlighted that truly demonstrate “Application efficiency at scale”.

  • Assessment Of Mach Stem Pressures: Comparison Of Experiments With Engineering And Eulerian Models

    Len Schwer (Schwer Engineering & Consulting Services)

    Laboratory scale tests conducted by Kisters and Kuder (2012) provide reflected pressure histories for a 1kg TNT charge detonated at 0.32m above a rigid surface. The pressure histories are measured 1m from the charge using a vertical array of pressure transducers to infer the height of the Mach Stem at this range. Two such vertical arrays, each with 9 pressure transducers at varying heights above the surface, were used, and the test was repeated three times. Four additional configurations with heights- of-burst (HOB) varying from 0.1 to 0.32m and standoff ranges of 0.9 to 1.2m were conducted, but not reported in the present reference. Examination of the measured wave forms allowed Kisters and Kuder to estimate the height of the Mach Stem, a.k.a. triple point, to within 60mm (vertical gauge spacing). The pressure histories from the vertical array measurements provide an opportunity to assess the accuracy of the LS-DYNA air blast engineering model referred to as LOAD_BLAST_ENHANCED, and results from simulations using the LS-DYNA Eulerian solver usually referred to as Multi-Material Lagrangian Eulerian (MM-ALE). In addition to comparisons of maximum pressure, and time-of-arrival (TOA), the time integrated pressure histories provide maximum impulses for comparison.

  • Assessment of Motorcycle Helmet Chin Bar Design Criteria with Respect to Basilar Skull Fracture using FEM

    S. Farajzadeh Khosroshahi, M. Ghajari (Imperial College London), U. Galvanetto (University of Padova)

    Statistical studies showed that the chin bar of full-face helmets is the region with the highest number of impacts. In an Australian research, fifty percent of severe impacts took place to the front of the helmet and forty percent of these resulted in Basilar Skull Fracture (BSF). There are two standards, which include criteria for assessing the performance of the helmet’s chin bar, Snell M2015 and ECE 22.05.

  • Assessment of the Capacity of a Reinforced Concrete Structure for Impact with Military Jet Aircraft

    M. Miloshev, M. Kostov (Risk Engineering)

    The current paper presents analysis of a reinforced concrete structure for impact with Phantom F-4 military aircraft. The analysis is performed by the missile-target interaction method. The finite element (FE) model of the aircraft is validated by comparison of the load-time function, obtained by numerical impact simulation into rigid planar target to the one, obtained from full-scale impact test. The latter was performed in 1988 at the SANDIA national laboratory in the US and the results were made public. Two models of the jet fuel are investigated – rigid fuel model and Smooth Particle Hydrodynamics (SPH). The rigid fuel model refers to the case where the mass of the fuel is lumped to the structural elements of the fuel tanks. The load-time curves computed by the numerical simulation into rigid wall are compared to the experimental one in Fig. 1. Very good match between the numerical and experimental results is achieved which implies that the FE model captures well the mass and stiffness distribution of the real aircraft and is suitable for performing missile-target interaction analyses. The target is a reinforced concrete structure with an asphalt layer which is laid on top of it. It is assumed that this asphalt increases the capacity of the structure and acts as an energy disspating layer in case of high velocity impact. A number of analyses is performed assuming asphalt material properties, defined for different temperatures and strain rates. The parameter which is compared as a result from the analyses is the area of perforation of the structure. It is related to the ammount of debris which could penetrate, as well as to the assessment of the consequences of possible fire inside.

  • ATV and MATV techniques for BEM acoustics in LS-DYNA

    Yun Huang, Zhe Cui (LSTC)

    This paper presents the new ATV (Acoustic Transfer Vector) and MATV (Modal Acoustic Transfer Vector) techniques for BEM acoustics in LS-DYNA, which were implemented recently. Acoustic Transfer Vector provides the transfer function between the normal nodal velocity on structural surface and the acoustic response at selected field points; Modal Acoustic Transfer Vector provides similar transfer function, but is based on the excitation from modal shape vibrations. ATV and MATV reveal the inherent properties of structures and acoustic volume, and can be used to predict radiated noise from vibrating structures when combined with vibration boundary conditions. Particularly they are useful for the acoustic analysis of structures subjected to multiple load cases. Some examples are given to illustrate the application of the ATV and MATV techniques. For ATV, post-processing of the results in the form of binary plot database is also presented.

  • Automated Metamodeling for Efficient Multi-Disciplinary Optimisation of Complex Automotive Structures

    Dr. Florian Jurecka - FE-DESIGN GmbH

    The use of multi-disciplinary optimisation methods (MDO) in the development process of complex automotive structures is often hindered by several problems. The required resources for very expensive simulations such as crash or 3D CFD analyses rapidly exceed the means available – especially whenever many input parameters, disciplines or load cases are involved. Furthermore, we have experienced that it can be difficult to assure stable runs of simulation processes over a longer period of time. As a result, ‚trivial’ problems such as missing licenses, an overload in network or hard disk resources can lead to a termination of the optimisation process. Not to mention that an optimisation run based on different disciplines can only start once all disciplines involved have set up their respective simulation models. Even a simple change in only one affected discipline would necessitate the optimisation run to start from scratch (with simulations for all load cases/disciplines to be redone). Here, metamodeling techniques can lead to a significant increase in efficiency since all information on the system behaviour gained from former analyses can be reused e.g. for optimisation runs or sensitivity analyses. In addition to this data storage functionality, the use of metamodels also decouples the occupation of computing resources from the actual use of the information. That means that idle CPU time can be used to collect more information on the product or system leading to reduced computation times in the actual optimisation method. Problems in particular simulation runs do not automatically result in a termination of the MDO method, but can easily be repeated. Consequently, it is also possible to evaluate the different disciplines independently even when other disciplines cannot provide a final simulation model yet. All these advantages together result in a much more efficient usage of computation resources. However, the complexity and diversity of metamodeling techniques often prevent the potential user from these benefits. Typically, the choice between the different metamodel formulations is not easy to make. In this paper, an approach is presented which allows for an automated model selection and fitting process. This approach enables the user to use metamodels rid of the complicated selection and fitting process. This task is undertaken by an optimisation algorithm which automatically generates a large variety of metamodels and accesses their respective applicability by means of statistics. As a result, the user gets the most suitable metamodel for each load case or discipline individually and in addition important information about the accuracy of the approximation. The approach will be illustrated by a typical example of a multi-disciplinary optimisation of automotive structures.

  • Automated Metamodeling for Efficient Multi-Disciplinary Optimisation of Complex Automotive Structures

    Dr. Florian Jurecka - FE-DESIGN GmbH

    The use of multi-disciplinary optimisation methods (MDO) in the development process of complex automotive structures is often hindered by several problems. The required resources for very expensive simulations such as crash or 3D CFD analyses rapidly exceed the means available – especially whenever many input parameters, disciplines or load cases are involved. Furthermore, we have experienced that it can be difficult to assure stable runs of simulation processes over a longer period of time. As a result, ‚trivial’ problems such as missing licenses, an overload in network or hard disk resources can lead to a termination of the optimisation process. Not to mention that an optimisation run based on different disciplines can only start once all disciplines involved have set up their respective simulation models. Even a simple change in only one affected discipline would necessitate the optimisation run to start from scratch (with simulations for all load cases/disciplines to be redone). Here, metamodeling techniques can lead to a significant increase in efficiency since all information on the system behaviour gained from former analyses can be reused e.g. for optimisation runs or sensitivity analyses. In addition to this data storage functionality, the use of metamodels also decouples the occupation of computing resources from the actual use of the information. That means that idle CPU time can be used to collect more information on the product or system leading to reduced computation times in the actual optimisation method. Problems in particular simulation runs do not automatically result in a termination of the MDO method, but can easily be repeated. Consequently, it is also possible to evaluate the different disciplines independently even when other disciplines cannot provide a final simulation model yet. All these advantages together result in a much more efficient usage of computation resources. However, the complexity and diversity of metamodeling techniques often prevent the potential user from these benefits. Typically, the choice between the different metamodel formulations is not easy to make. In this paper, an approach is presented which allows for an automated model selection and fitting process. This approach enables the user to use metamodels rid of the complicated selection and fitting process. This task is undertaken by an optimisation algorithm which automatically generates a large variety of metamodels and accesses their respective applicability by means of statistics. As a result, the user gets the most suitable metamodel for each load case or discipline individually and in addition important information about the accuracy of the approximation. The approach will be illustrated by a typical example of a multi-disciplinary optimisation of automotive structures.

  • Automated Post Simulation Analysis, Mining, Reporting and Collaboration with d3VIEW

    A. Nair, S. Bala (LSTC)

    Data management, mining, comparison and presentation play vital roles in utilization of Finite Element Analysis for product design and decision making. Post simulation interpretation of results is largely a manual process and interpretation of data points is limited to only a handful of data points. The capability to perform such tasks seamlessly will reduce workload for an engineer and help focus his attention more on engineering rather than spend time generating reports. d3VIEW is a simulation data management and collaboration software that is tightly integrated with LS-DYNA to automate post-simulation analysis. This paper will discuss the evaluation of d3VIEW. Publicly available LS-DYNA finite element models are used to showcase d3VIEW’s capability. d3VIEW’s ability to extract LS-Dyna results, store and compare data, generate reports using templates, visualization and collaboration are highlighted. Collaboration of reports generated automatically with peers and management would give instant access to qualitative and quantitative post processing of simulation results.

  • Automated Post-Processing & Report-Generation for Standard Crash & Safety Tests Simulation

    T. Nikolaos (BETA CAE Systems S.A.)

    There are an increasing number of standardized tests, for which a vehicle should comply with. All these tests, usually, require the generation of a standardized report. For the generation of reports for simulated tests, after each solver run, the followed post-processing actions are always the same. Most of the tasks in the post-processing of simulation of road vehicles crash tests, involve repeated actions while, in certain cases, these actions may represent up to 90% of the total. This repetition is proven cumbersome, time-consuming and prone to errors. Therefore, the automation of the execution of those actions and the subsequent report generation is required. This paper presents software tools that automatically process and create reports, for Pedestrian Safety analysis, Occupant Protection in Interior Impact (FMVSS 201U), IIHS structural ratings and Bus Rollover (ECE R66), based ®on LS-DYNA results. These tools streamline the extraction of the results for the respective tests. They lead directly to reports and create overview models for supervisory evaluation in cases of a large number of simulation runs. The automation of complicated post-processing procedures in μETA (mETA), the Post-Processor of BETA CAE Systems S.A., not only saves time and eliminates user’s frustration but it also assures an error-free outcome. Keywords: Post-processing, process automation, reporting, Pedestrian Safety, FMVSS 201U, IIHS, Bus Rollover ECE R66.

  • Automatic Analysis of Crash Simulations with Dimensionality Reduction Algorithms such as PCA and t-SNE

    David Kracker (Dr. Ing. h.c. F. Porsche AG), Jochen Garcke (Fraunhofer SCAI), Axel Schumacher University of Wuppertal, Pit Schwanitz (University of Wuppertal)

    The increasing number of crash simulations and the growing complexity of the models require an efficiently designed evaluation of the simulation results. Nowadays a full vehicle model consists of approximately 10 million shell elements. Each of them contains various evaluation variables that describe the physical behavior of the element. Therefore, the simulation models are very high dimensional. During vehicle development, a large number of models is created that differ in geometry, wall thicknesses and other properties. These model changes lead to different physical behavior during a vehicle crash. This behavior is to be analyzed and evaluated automatically. In this article, potentials of several algorithms for dimensionality reduction are investigated. The linear Principal Component Analysis (PCA) is compared to the non-linear t-distributed stochastic neighbor embedding (t-SNE) algorithm. For those algorithms, it is necessary that the input data always has an identical feature space. Geometrical modifications of the model lead to changes of finite element meshes and therefore to different data representations. Therefore, several 2D and 3D discretization approaches are considered and evaluated (sphere, voxel). In order to assess the quality of the results, a scale-independent quality criterion is used for the discretization and the subsequent dimensionality reduction. The simulations used in this paper are carried out with LS-DYNA®. The aim of the presented study is to develop an efficient process for the investigation of different data transformation approaches, dimensionality reduction algorithms, and physical evaluation quantities. The resulting evaluation method should represent physically relevant effects in the existing simulations in a low-dimensional space without human interaction and thus support the engineer in the evaluation of the results.

  • Automatic Evaluation of LS-DYNA® Simulation Results Using Statistical Database and Python

    Daxin Wu, Olaf Hartmann (ARRK Engineering)

    Thanks to the significant increase of computational power, full-vehicle crash simulation has become a standard procedure in vehicle crashworthiness design. It has enabled engineers to accommodate constantly shortened development period in automotive industry. On the other hand, with eased access to simulation tools, simulation results flood during the project development. Most of the time, only a small specific portion of the results is analyzed by engineers. Based on internal statistics gathered from various projects, the number of curves in history outputs from a full-vehicle crash simulation varies from 14,000 to 500,000, depending on the model complexity and conventions of the project. Nevertheless, only 0.1 to 1 percent of the entire outputs are used. The rest of the curves are not analyzed mainly due to two reasons, namely little relevance to the focus of the analysis and absence of post-processing method for systematic analysis of a large amount of outputs. However, considering the size of a full vehicle crash model and the complexity of the crash event, a lot of information can be overlooked. Using data mining, history outputs from past simulations can be systematically gathered, processed in a statistical manner and then stored in a database to serve as a reference for future simulations and even as the basis for more advanced evaluations methods. In the scope of this work, we developed a method for automatic evaluation of history outputs of LS-DYNA simulations by comparing them with a reference database created from previous simulation results, which are predecessors or comparable with the new simulation. The comparison identifies the history outputs with the most significant deviations and records the time points, when such discrepancies occur. Furthermore, the spatial information of these history outputs are extracted, namely the positions on the vehicle. The comparison result therefore shows both the time when deviations occur and the structural regions which are most likely responsible for the deviations. This helps determine the sequence of different structural behaviors and their interdependencies. Significant deviations can come from initial differences in the model, which may indicate modelling errors, or arise over time. This tool was adopted in the crash development of a sports car in order to ensure model quality and identify the sequence of different structural behaviors and their causes. In this paper, we present the possibility of automatic evaluation of all LS-DYNA history outputs using python. This serves as a foundation for further evaluation techniques based on big data analysis.

  • Automatic Generation of Accurate Material Models for Long Fiber Reinforced Plastics in Crash Simulations

    Timo Schweiger, Jörg Lienhard, Hannes Grimm-Strele, Matthias Kabe

    Long fiber reinforced plastics (LFRPs) offer excellent mechanical properties and are widely used in automotive and aerospace industries. Accurately modeling the behavior of LFRPs under crash conditions is crucial for designing lightweight and safe structures. However, creating reliable material models for LFRPs is challenging due to their complex microstructure and anisotropic nature. This study presents an automatic method to generate highly accurate material models for LFRPs, specifically tailored for crash simulations.

  • Automatic Processes for Multiple Analyses

    Miles Thornton, Christopher Bell, David Burton, Paul Davidson, Ben Dennis, Roger Hollamby, Richard Sturt - Arup

  • Automating LS-DYNA Simulation Processes using SOFY’s Rapid Application Development Environment RADE.

    Dirk Ulrich - SOFY GmbH, Germany

    Since the first applications of Finite Element Analysis (FEA) in automotive design this technology has gone a long way to become a standard tool fully integrated in the design process of automotive industry. Strongly promoted by progress in mathematics, information and computer technology simulation results have today reached a level of accuracy comparable to physical testing. In parallel developments in software technology – ranging from CAD to graphical interactive pre- and postprocessing - have helped FEA to develop from a work performed by specialists into an industrial tool used by design engineers. Within a product design engineers often have to judge the performance of dozens of design variants by doing very similar Finite Element Analysises. This leads to the requirement to automate the preand postprozessing of FEA to reduce errors and turnaround times and to improve quality and productivity. This paper demonstrates how RADE – the Rapid Application Development Environment – of the commercial pre- and postprocessing package SOFY is used in industry to automate analysis processes from input creation to report generation.

  • Automating Oasys PRIMER and Oasys D3PLOT using JavaScript

    Miles Thornton - Arup

    Oasys PRIMER and Oasys D3PLOT now contain JavaScript interpreters. Adding a scripting engine allows the user to automate both pre and post processing tasks. Extensions to the core JavaScript language allow the user to interact with the programs, create and/or manipulate data, create user interfaces, read and write files and extend the functionality of PRIMER and D3PLOT. The syntax is quick and easy to learn. There are several advantages in using scripts: • Quick turnaround – you do not have to wait for new version of PRIMER or D3PLOT • You can keep your application confidential • The script is under your control – you can do it yourself if you wish. This paper describes the scripting technology, outlines possible applications and gives demonstrations in Oasys PRIMER and Oasys D3PLOT.

  • Automation of LS-DYNA’s Material Model Driver for Generation of Training Data for Machine Learning based Material Models

    D. Sommer, K. Mitruka, Prof. P. Middendorf (University of Stuttgart)

    The substitution of classical constitutive material models with data-driven models supported by machine learning techniques could provide a leap in the modelling of materials. The most notable benefits are a faster description of new materials without a tedious manual parameter identification procedure, lower computational time for simulations due to efficient computation within the material model and a more efficient selection of the correct material model for the use-case. The base for any data-driven model is adequate amount and quality of training data. Based on this, machine learning techniques can be used to train neural networks such that they learn the relationship between given input and output. The mapping in the machine learning based material model will be the strain measures to the stresses, similar to classical models.

  • Automatized Kinetic and Strainfield Based Calibration for a Thermoplastic Material Model using High Speed Tensile Tests

    S. Schilling, P. Suppinger, P. Blome (Autoliv)

    Current and future automotive development cycles are driven by the needs for lightweight designs, cost reductions, comfort- and safety improvements and the reduction of time-to-market. One way to cope with the listed challenges is the usage of thermoplastic materials for integrative designs of components. Among the challenges for passive safety supplier Autoliv to design thermoplastic components, which are placed in the load path of seatbelt components, is the strong dependency on loading velocity of the components. As crash situations are the most dominant load cases for design and functionality, a strong demand for predictive strain rate dependent material models is given. Strain rate effects are next to temperature- and humidity effects the major challenge concerning thermoplastics. As an industrial demand for a comprehensive material database, it needs to be fast, efficient, economical and accurate. Also, the need for a fully automatized material model calibration process is expressed. To fulfill these demands a two-stage reverse engineering process fits test results to analytical approaches for a quasi-static and a strain rate dependent stress-strain response along with an analytic approach for modelling of visco-elasticity and strain rate dependent damage. The needed test results, to which the analytical parameters are fitted, consist of force-displacement as well as strainfield characteristics and were measured using a newly developed high-speed tensile testing device. This device is designed to get close to constant loading velocity of specimen resulting in strain rates up to 𝜀𝜀̇ = 320 𝑠𝑠−1. The accuracy of the test results is ensured by a wedge-to-wedge, self-locking coupling mechanism, a start-up length for acceleration travel of the tensile testing machine as well as a local force gauge. Especially by the local force gauge, consisting of strain gauges arranged as Wheatstone bridge, it is realized that oscillations in force signals of dynamic testing are minimized. The automatized material model calibration routine fed with accurate test results from the high-speed tensile testing device shows promising results to further enhance simulation quality and predictability for the design of thermoplastic components in crash load cases.

  • AutoMesher for LS-DYNA Vehicle Modeling

    Ryan Alberson, David Stevens (Protection Engineering Consultants), James D. Walker, Tom Moore (Southwest Research Institute)

    Software has been developed to automatically mesh CAD files in support of expedient modeling of armored vehicles and similar structures. The AutoMesher software is written in Python as well as LSTC’s Script Command Language (SCL). The SCL syntax is similar to C programming, but runs as a script within LSTC’s LS-PrePost® (LSPP) software application. A Python module is used as the interface and a wrapper for LSPP. By leveraging the functions in LSPP through the SCL, nine different algorithms were written to mesh I beams, T beams, angles, rods, plates, tubes, and surface-meshed formed shapes. Logic is used in these algorithms to identify the shape characteristics needed to define an equivalent FEA mesh of the CAD geometry, such as geometric planes that represent flanges or web components of an I-beam. These algorithms are the heart of the AutoMesher and can be used to generate more intelligent meshing solutions. The algorithms and software are described in this presentation. The AutoMesher software was developed by Protection Engineering Consultants (PEC) in support of the Defense Advanced Research Projects Agency (DARPA) Adaptive Vehicle Make (AVM) program, under subcontract to Southwest Research Institute (SwRI). AVM is an ambitious program to reduce the time required for the design, development, and production of complex defense cyber-mechanical systems, such as military ground vehicles, by a factor of five.

  • Automotive Door Sealing System Analysis

    Rosa Zhao, Frank Lee, Thomas Oetjens - General Motors Corp.

    Door sealing system is one of the most important automotive quality issues. Problems with door seal system could cause water leakage, wind noise and hard to open or close, which impair customer’s satisfaction of the vehicle. That is why the door seal problem is always among the Hardy Perennial Top 10 list in JD Power Tracking Study. The design rationality and manufacturing process are important aspects for the functionality and performance of a sealing system. However, the door sealing system involves many design variables and manufacturing variables. It is almost impossible to precisely confirm individual quantitative effects on functionalities of these variables. Therefore, computer based simulation of door sealing system is more practical since it can isolate the critical factors and it is cost effective and time efficient. LS-DYNA was used to simulate door seal system. The key structural component, the rubber seal, was modeled and simulated. Different types of elements, material models and contact algorithms from LS-DYNA element, material and contact libraries were tried and compared. Consequently, the best modeling and simulation technology was developed for the door sealing system analysis. The newly developed method showed the great potential of comprehensive studies of door sealing system. The analysis results provided some major parameters, such as seal deformation, contact pressure and energy transformation, which would influence the functionality and performance of the door sealing system. The analysis results have been compared with some available test data, and very good correlations were obtained. The analysis also evaluated the influence of manufacturing deviations. With the results obtained from this analysis, the relationship between the major parameters could be established and used as a tool to derive a better sealing system design at early stage. This analysis method could also be used to evaluate the influence of certain type of process error. Eventually, this analysis method will be developed into a tool that is capable of predicting water leakage, wind noise and hard to open/close problems caused by either product design or manufacturing process.

  • Axial Crushing of an Aluminum-CFRP Hybrid Component: FE-Modeling, Simulation and Experimental Validation

    S. Hoque (AIT), A. Rauscher (University of Applied Sciences Upper Austria)

    The crushing performance of aluminum-CFRP (Carbon Fiber-Reinforced Plastics) hybrid generic crash components under axial compression load is experimentally investigated. Aluminum crash components, having similar geometry, are also crushed and compared with the hybrid components. The performance of the hybrid components is found to be twice as much as that of the aluminum components in terms of peak force and specific energy absorption (SEA). Finite element simulations of the crush tests are carried out in LS-DYNA®. The extended 3-parameter Barlat model (MAT36E) is used to characterize the anisotropic elasto-plastic behavior of aluminum sheet. The CFRP laminate is characterized by an orthotropic linear elastic material model (MAT54) with a progressive failure criterion (Chang and Chang). The aluminum-CFRP interface is modeled using tied contact with cohesive mixed mode failure criterion to capture the delamination behavior. Good agreement is found between experiment and simulation in terms of Specific Energy Absorption (SEA) as well as deformation pattern.

  • Bake-Hardening Effect in Dual-Phase Steels: Experimental and Numerical Investigation

    David Koch, Filipe Andrade, André Haufe, DYNAmore GmbH, Stuttgart, Germany;, Markus Feucht, Daimler AG, Sindelfingen, Germany

    Typically, the material characterization for the simulation is performed based on the virgin material which is used for the preparation of the corresponding component. However, due to the processing of the material, its mechanical properties may vary greatly. A typical example are materials subjected to forming operations. The work hardening during the forming process changes the local material properties such that the stress necessary for further plastic straining increases. Such effect can actually be captured in numerical simulations by transferring the plastic strain from the forming process into the subsequent step (e.g., a crash simulation). However, several components undergo not only a forming but also a heat process. Experimental evidence shows that the combination of plastic straining and heat treatment can further affect the behavior of a material. Therefore, a closer look at the influence of the pretreatment as well as the development of methods to take this influence into consideration is of great interest.

  • Bake-Hardening Effects, Arbitrary Image Data and Finite Point-Set Analysis Results made Accessible with envyo

    C. Liebold (DYNAmore), J. Zerbst (Daimler), S. Hagmann (Porsche), M. Hedwig (Porsche)

    In the recent past, a lot of effort has been made towards the closing of the simulation process chain for all different kinds of materials. Besides the regular transfer of resulting stress, strain, and history data, main focus from a material’s perspective has been on the transfer of fiber orientations from process simulations for continuous fiber reinforced composites [1] together with various homogenization approaches for short fiber reinforced plastic materials [2].

  • Ballistic Behaviour of UHMWPE Composite Material: Experimental Characterization and Numerical Simulation

    H. Abdulhamid, P. Deconinck, P.-L. Héreil, J. Mespoulet (Thiot-Ingenierie)

    This paper presents a comprehensive mechanical study of UHMWPE (Ultra High Molecular Weight Polyethylene) composite material under dynamic loadings. The aim of the study is to provide reliable experimental data for building and validation of the composite material model under impact. Three types of dynamic characterization tests have been conducted: in-plane tension, out-of-plane compression and out-of-plane shear. Moreover, impacts of spherical projectiles impact have been performed on larger specimen. Regarding the numerical simulation, an intermediate scale multi-layered model (between meso and macro scale levels) is proposed. The material response is modelled with a 3d elasto-orthotropic law coupled with fiber damage model. The modelling choice using *MAT_ORTHOTROPIC_SIMPLIFIED_DAMAGE is governed by a balance between reliability and computational cost. Material dynamic response is unconventional [1, 2]: it shows large deformation before failure and very low shear modulus and peeling strength. Numerical simulation has been used both during the design and the analysis of tests. Mechanical properties related to elastic moduli and failure strength have been measured. The ballistic numerical model is able to reproduce the main behaviors observed in the experiment. The study has highlighted the influence of temperature and fiber slipping in the impact response of the material.

  • BALLISTIC IMPACT MODELING OF COMPOSITE MATERIALS

    Chian-Fong Yen - Materials Sciences Corporation

    A computational constitutive model has been developed to characterize the progressive failure be- haviors of composite laminates under high velocity ballistic impact conditions. The composite failure model has been implemented within LS-DYNA as a regular material subroutine. The inte- grated code was successfully utilized to predict the damage and ballistic behavior of composite laminates subjected to various ballistic impact conditions. The availability of this design tool will greatly facilitate the development of composite structures with enhanced ballistic survivability.

  • Ballistic Impact Simulations of an Aluminum 2024 Panel Using *MAT_224 in LS-DYNA® Considering Oblique Incidence and Attitude Angles of a Rectangular Projectile

    C. K. Park, K. Carney, P. Du Bois, C. D. Kan (George Mason University), G. Queitzsch (retired, Federal Aviation Administration), D. Cordasco, W. Emmerling (Federal Aviation Administration)

    The objective of this study is (1) to validate the *MAT_224 model for Aluminum 2024 with complex impact conditions, (2) to evaluate its predictability of ballistic limit and residual velocities of a projectile under various impact conditions, and (3) to investigate the effects of oblique and attitude angle variations of a projectile on penetration to a target plate. The newly developed *MAT_224 model (version 2.0) for Aluminum 2024 was utilized to simulate a series of ballistic impact tests conducted by NASA using a rectangular block projectile of Inconel 718 with sharp edges and corners, impacting Aluminum 2024 flat panels at oblique angles of incidence. A full ballistic impact simulation model was created with over twenty million solid elements and used to conduct approximately one hundred ballistic impact simulations. Overall, the ballistic impact simulations showed highly comparable results with the NASA tests in terms of projectile residual velocities, failure shapes of the target plates, and projectile penetration behavior. Based on a series of ballistic impact simulations, the ballistic limit velocities of the projectile were predicted.

  • BatMac: A Battery Macro Model to Simulate a Full Battery in an Electric or Hybrid Car Crash

    P. L‘Eplattenier, I. Caldichoury (LSTC)

    Safety is an important functional requirement in the development of large-format, energy-dense, lithium-ion (Li-ion) batteries used in electrified vehicles. Computer aided engineering (CAE) tools that predict the response of a Li-ion battery pack to various abusive conditions can support analysis during the design phase and reduce the need for physical testing. In particular, simulations of the multiphysics response of external or internal short circuits can lead to optimized system designs for automotive crash scenarios.

  • Batted-Ball Performance of a Composite Softball Bat as a Function of Ball Type

    Jennifer Yee (Combat, University of Massachusetts), James A. Sherwood (University of Massachusetts), Stephen Fitzgerald (Combat)

    The ideal models of softball bats and balls should have the flexibility to allow for the ability to capture how BBS varies as a result of changes in bat and ball constructions. If such models were available, then the design engineer could customize the bat design with the goal to maximize the BBS for a given ball construction. A credible finite element model of the ball-bat collision for softball is challenging. Achieving such a model is difficult primarily because of variations in the processing of the polyurethane cores of softballs which can yield different properties of the overall ball, e.g. hardness and liveliness, and the response of the softball during a bat-ball collision is rate dependent. The mechanical behavior of the composite bat is slightly less challenging to model because the bat material can be assumed to be essentially linear elastic unless significant material damage is induced during the collision. Experimental and finite element methods were used to model the collision between a composite softball bat and softballs of different COR (Coefficient of Restitution) and compression specifications. An example model is shown in Figure 1. Experimental bat characterization methods included barrel compression and modal analysis. Experimental softball characterization methods included COR, CCOR (Cylindrical Coefficient of Restitution), compression and dynamic stiffness. Finite element models were built in HyperMesh and analyzed in LS-DYNA®. Softballs were modeled using LS-DYNA material models #6, #57 and #83, and the composite softball bat was constructed according to the manufacturer’s specifications using *PART_COMPOSITE. Three methods to calibrate the finite element softball models were investigated and included “flat-surface” and “cylindrical-surface” coefficients of restitution and DMA (dynamic mechanical analysis). The “cylindrical-surface” test was found to be the most effective method of calibration to predict the batted-ball speed (BBS) as measured in bat/ball impact testing. This paper presents a summary of the complimentary experimental and finite element studies that were completed to develop a bat-ball collision model for the research of composite softball bats. Softballs were characterized using simple tests, and finite element models of the softballs were calibrated to yield good correlation to the experimental characterization tests. The calibrated softball models were then used to explore their ability to correlate with bat-ball collisions using a composite softball bat.

  • Battery Abuse Case Study Analysis Using LS-DYNA ®

    James Marcicki, Alexander Bartlett, Xiao Guang Yang, Valentina Mejia, Min Zhu, Yijung Chen (Ford Research and Innovation Center), Pierre L’Eplattenier, Iñaki Çaldichoury (LSTC)

    Battery abuse research and modeling, Spatially-resolved battery modeling, Electro-thermal battery modeling. As Lithium-ion batteries see increasing use in a variety of applications, anticipation of the response to abuse conditions becomes an important factor in designing optimized systems. Abuse scenarios with potential relevance to the automotive industry include crash-induced crush leading to an internal short circuit, external short circuit, or thermal ramp, and overcharge conditions. Simulating each of these abuse scenarios requires sophisticated modeling tools that span multiple physical and electrochemical phenomena, as well as handle complex geometries that accurately represent battery cells, modules, and packs. The three-dimensional, transient analysis capabilities of LS-DYNA can be leveraged to simulate the battery response with a high degree of spatial resolution, which is widely considered a prerequisite for predicting the highly localized phenomena involved in the onset of thermal runaway. The electrical, electrochemical and thermal response of the new LS-DYNA battery model can be coupled to the mechanical solver using a variety of approaches, ranging from one-way coupling based on a time-scale analysis to tight two-way coupling. Several battery abuse case studies will be examined to verify the capability of the modeling tools. The impact of hardware size will be investigated, as the thermal behavior and corresponding severity of the abuse response changes depending on the number of cells and their configuration within a module. Experimental data will be used to estimate parameters, confirm the model capability, and identify areas of future work to improve the fidelity and ease of implementation of the simulation tool. Multiple hardware types will be compared to demonstrate the relationship between cell performance and module abuse response.

  • Battery Abuse Simulations Using LS-DYNA

    P. L'Eplattenier (LSTC)

    Safety is an important functional requirement in the development of large-format, energy-dense, lithium-ion (Li-ion) batteries used in electrified vehicles. Computer aided engineering (CAE) tools that predict the response of a Li-ion battery pack to various abusive conditions can support analysis during the design phase and reduce the need for physical testing. In particular, simulations of the multiphysics response of external or internal short circuits can lead to optimized system designs for automotive crash scenarios. Recently, a so called “distributed randles circuit” model was introduced in LS-DYNA in order to mimic the complex electrochemistry happening in the electrodes and separator of lithium ion batteries. This model is based on electrical circuits linking the positive and negative current collectors reproducing the voltage jump, internal resistance and dumping effects occurring in the active materials. These circuits are coupled with the Electromagnetics (EM) resistive solver to solve for the potentials and current flow in the current collectors and the rest of the conductors (connectors, busses, and so forth). The EM is coupled with the thermal solver to which the joule heating is sent as an extra heating source, and from which the EM gets back the temperature to adapt the electrical conductivity of the conductors as well as the parameters of the Randles circuits. One of the advantages of the Randles circuit model is the relative easiness to introduce internal short circuits by just replacing the Randles circuits in the affected area by a short resistance. The Randles circuit model also is coupled with the mechanical solver of LS-DYNA where the deformations due to a battery crush allow the definition of criteria to initiate internal shorts. Up to now, the Randles circuit model was only available on solid elements. So the user had to create a mesh with all the layers of a cell (positive current collector, positive electrode, separator, negative electrode, negative current collector, negative electrode, separator, and so forth), and define segment sets of each of the current collectors to connect them by Randle circuits in a distributive way. The construction of the case was cumbersome and the mechanical solver often presented limitations on solid elements with one very small dimension compared to the other ones due to the extreme thinness of the different layers. The mechanical deformation of a succession of stiff layers (current collectors) and very soft ones (electrodes and separators) also was a challenge. Recently, the Randles circuit model has been extended to composite Tshells. These new elements promise a better and faster mechanical resolution, and make the setting of the simulations much easier for the user. Finally, a new battery packaging environment is being developed in LS-PREPOST helping with the setup of cell or multi-cell cases. In section 2, we will present the new battery cell model on composite Tshell and give some first example of internal short simulations, and in section 3, we will present the new battery packaging environment in LS-PREPOST

  • Battery Cooling Simulation using STAR-CCM+

    D. Grimmeisen, M. S. Schneider (Cascate)

    A generic Li-ion battery pack as typically used in an electric vehicle is simulated in STAR-CCM+, using an analytical model for the electrochemical battery behavior and a thermal/flow simulation with conjugate heat transfer to determine the cooling efficiency. A single Li-ion battery cell is modeled in Battery Design Studio. This model is then used in the Battery Simulation Module of STAR-CCM+, which allows to embed the cell within an electric circuit and to put it under a prescribed load. The battery model then calculates the heat development in the cell based on the load and the electrochemical model. This heat is applied as a distributed heat source in the fluid simulation, which can then be used to investigate and optimize the cooling efficiency.

  • Battery simulation in the crash load case

    Slides of the presentation from S. Rybak (EDAG)

  • Behaviour and Modelling of Dual-Phase Steels

    Venkatapathi Tarigopula, Odd Sture Hopperstad, Magnus Langseth, Arild Holm Clausen - Norwegian University of Science and Technology (NTNU)

    Dual-phase steels are being increasingly considered for application in vehicle structural crash components because of their combined attributes of high-strength and good formability characteristics. Accurate prediction of such components, which are often made of formed components, is necessary to reduce the cost of physical tests. The non-linear finite element method is an efficient and reliable tool for the design of new components. The reliability of the finite element analyses depends on the accuracy of the constitutive and fracture models. To support the engineering applications of dual- phase steels for crash and forming events, both strain hardening and strain rate hardening must be thoroughly modelled for general loading paths. In this paper, an elasto-viscoplastic phenomenological model is adopted to represent the material behaviour of dual-phase steels. The constitutive model is formulated in the framework of phenomenological continuum mechanics. The main ingredients of the model include a non-quadratic yield criterion, the associated flow rule and non-linear isotropic and kinematic hardening. The model is within the class of plasticity models proposed by Chaboche [1] and Lemaitre and Chaboche [2] for application to monotonic, non-proportional and cyclic loading conditions. The constitutive model is also able to depict viscous characteristics of the material. The material was experimentally characterized under different loading conditions suited for crash and forming events. Figure 1 depicts the approach embraced in this research for identification of material parameters for the utilized model from material tests. The conventional material tests are providing data for the calibration of the model. Simple tension tests were used to characterize the elastic parameters, the yield surface and the isotropic hardening parameters. Non-proportional tension tests were used to identify the kinematic hardening parameters. Additionally, viscous parameters were identified from the corresponding tension tests over a wide range of strain-rates. The predictive capability of the adopted numerical model is assessed against the material behaviour at elevated rates of strain and the material behaviour under strain-path changes. Particularly, phenomena like dynamic localisation, large plastic deformations have given due importance for validity of the numerical model. Moreover, the same model is validated for crashworthiness performance of dual-phase steel generic components. The model provides results which are in good agreement with the experimental observations. In this work, the non-linear explicit FE code LS-DYNA was used for numerical computations.

  • Behaviour and Modelling of Dual-Phase Steels

    Venkatapathi Tarigopula, Odd Sture Hopperstad, Magnus Langseth, Arild Holm Clausen - Norwegian University of Science and Technology (NTNU)

    Dual-phase steels are being increasingly considered for application in vehicle structural crash components because of their combined attributes of high-strength and good formability characteristics. Accurate prediction of such components, which are often made of formed components, is necessary to reduce the cost of physical tests. The non-linear finite element method is an efficient and reliable tool for the design of new components. The reliability of the finite element analyses depends on the accuracy of the constitutive and fracture models. To support the engineering applications of dual- phase steels for crash and forming events, both strain hardening and strain rate hardening must be thoroughly modelled for general loading paths. In this paper, an elasto-viscoplastic phenomenological model is adopted to represent the material behaviour of dual-phase steels. The constitutive model is formulated in the framework of phenomenological continuum mechanics. The main ingredients of the model include a non-quadratic yield criterion, the associated flow rule and non-linear isotropic and kinematic hardening. The model is within the class of plasticity models proposed by Chaboche [1] and Lemaitre and Chaboche [2] for application to monotonic, non-proportional and cyclic loading conditions. The constitutive model is also able to depict viscous characteristics of the material. The material was experimentally characterized under different loading conditions suited for crash and forming events. Figure 1 depicts the approach embraced in this research for identification of material parameters for the utilized model from material tests. The conventional material tests are providing data for the calibration of the model. Simple tension tests were used to characterize the elastic parameters, the yield surface and the isotropic hardening parameters. Non-proportional tension tests were used to identify the kinematic hardening parameters. Additionally, viscous parameters were identified from the corresponding tension tests over a wide range of strain-rates. The predictive capability of the adopted numerical model is assessed against the material behaviour at elevated rates of strain and the material behaviour under strain-path changes. Particularly, phenomena like dynamic localisation, large plastic deformations have given due importance for validity of the numerical model. Moreover, the same model is validated for crashworthiness performance of dual-phase steel generic components. The model provides results which are in good agreement with the experimental observations. In this work, the non-linear explicit FE code LS-DYNA was used for numerical computations.

  • Behaviour model for semi-crystalline polymer, application to crashworthiness simulations

    R.Balieu, F.Lauro, B.Bennani, B.Bourel - Univ Lille Nord de France, K.Nakaya, E.Haran - TOYOTA MOTOR EUROPE

    Today polymer materials are frequently used in the transport domain with more severe specification requirements. The behaviour modeling and failure prediction have consequently become a priority. In this paper, an elasto- viscoplastic behaviour model is presented, with non associated plasticity, damage and strain rate effect, which represents the observed behaviours of a semi-crystalline polymer under dynamic loading.

  • Belt Modelling in LS-DYNA®

    Mikael Dahlgren, Abhiroop Vishwanatha, Anurag Soni (Autoliv Sweden, India, North Germany), Klas Engstrand, Jimmy Forsberg (DYNAmore Nordic AB), Isheng Yeh (LST LCC)

    Belt modelling in LS-DYNA has gone from 1D-belt elements, through hybrid belt modelling into 2D seatbelt elements. The current paper investigates recently developed features in LS-DYNA such as bending, strain-rate and orthotropic material behavior. A short description of the evolution of belt modelling is also given. Belt modelling in LS-DYNA has in the past and in the closest future included modelling of sliprings which are points in space where the belt elements pass through. Typical, these are located at sharp directional changes in the belt routing, e.g. B-pillar, D-ring and buckle tongue. Currently, it is the slipring functionality that inhibits users from using an ordinary element and material, of their own selection, to model the belt. Both 1D and 2D belt elements are assigned with *MAT_SEATBELT as it is the only material compatible with sliprings. 2D belt elements in LS-DYNA is a combination of 1D-belt elements along the length direction of the belt and 2D membrane elements made of a MAT_FABRIC material created internal in LS-DYNA. The MAT_FABRIC is created based on *MAT_SEATBELT values. This means current *MAT_SEATBELT in LS-DYNA do not carry any bending loads. The new feature development makes the coating functionality found for MAT_FABRIC available in *MAT_SEATBELT_2D. This enables the bending load carrying possibilities for the 2D belt elements in LS-DYNA. Apart from this feature strain-rate dependency and orthotropic material behavior have been added to the 2D belt elements. It will be shown that the interaction between occupant and belt is improved. It will also be shown that the behavior of an unloaded belt is improved. Finally, there is a short outline of foreseen future needs regarding belt modelling features.

  • BEM Methods For acoustic and vibroacoustic problems in LSDYNA

    Souli Mhamed, Yuang Yun, Zhe Cui, Zeguar Tayeb (LSTC)

    The present work concerns the new capability of LS-DYNA in solving acoustic and vibroacoustic problems in time domain and frequency domain, using the following LSDYNA Cards: *MAT_ACOUSTIC *FREQUENCY_DOMAIN_ACOUSTIC_BEM *FREQUENCY_DOMAIN_ACOUSTIC_FEM *FREQUENCY_DOMAIN_SSD In vibroacoustic problems, which are assumed to be weak acoustic-structure interactions, the transient structural response is computed first. By applying the FFT, it is transformed into a frequency response. The obtained result is taken as boundary condition for the acoustic part of the vibro acoustic problem. Consequently, the radiated noise at any point into space can be calculated. The new developed LS-DYNA keyword is based on boundary element method (BEM) in which only the surface of the acoustic domain needs to be discretized. Besides BEM that solves the Helmholtz equation as a linear system, the new card allows, also, to use two other approximate Rayleigh and Kirchhoff methods. Both methods do not require a system of equations to be assembled and solved. Consequently, they are faster than BEM. Rayleigh method assumes that the radiating structure is a plane surface clamped into an infinite rigid plane. In Kirchhoff method, BEM is coupled to FEM used for acoustics in LS-DYNA by prescribing non reflecting boundary condition. In this case, at least one fluid layer needs to be merged to the vibrating structure.

  • BEM Methods For acoustic and vibroacoustic problems in LS-DYNA

    Yun Huang - Livermore Software Technology Corporation, Mhamed Souli - University of Lille, Rongfeng Liu - JSOL Corporation

    This paper presents the new developments of finite element methods and boundary element methods for solving vibro-acoustic problems in LS-DYNA. The formulation for a frequency domain finite element method based on Helmholtz equation is described and the solution for an example of a simplified compartment model is presented. For boundary element method, the theory basis is reviewed. A benchmark example of a plate is solved by boundary element method, Kirchhoff method and Rayleigh method and the results are compared. A dual boundary element method based on Burton-Miller formulation is developed for solving exterior acoustic problems which were bothered by the irregular frequency difficulty. Application of the boundary element method for performing panel contribution analysis is discussed. These acoustic finite element and boundary element methods have important application in automotive, naval and civil industries, and many other industries where noise control is a concern.

  • BEM Methods For Acoustic and Vibroacoustic Problems in LS-DYNA

    M. Souli, Y. Huang, R. Liu (LSTC, University of Lille Laboratoire Mecanque de Lille, JSOL Corp.)

    The present work concerns the new capability of LS-DYNA® in solving acoustic and vibroacoustic problems using a new keyword *FREQUENCY_DOMAIN_ACOUSTIC_BEM In vibroacoustic problems, which are assumed to be weak acoustic-structure interactions, the transient structural response is computed first. By applying the FFT, it is transformed into a frequency response. The obtained result is taken as boundary condition for the acoustic part of the vibro acoustic problem. Consequently, the radiated noise at any point into space can be calculated. The new developed LS-DYNA keyword is based on boundary element method (BEM) in which only the surface of the acoustic domain needs to be discretized. Besides BEM that solves the Helmholtz equation as a linear system, the new card allows, also, to use two other approximate Rayleigh and Kirchhoff methods. Both methods do not require a system of equations to be assembled and solved. Consequently, they are faster than BEM. Rayleigh method assumes that the radiating structure is a plane surface clamped into an infinite rigid plane. In Kirchhoff method, BEM is coupled to FEM used for acoustics in LS-DYNA by prescribing non reflecting boundary condition. In this case, at least one fluid layer needs to be merged to the vibrating structure.

  • Benchmark as decision support for cloudification: Moving CAE and HPC to the cloud increases quality and efficiency of simulations

    C. Woll (GNS Systems)

    A decision in favor of the cloud and the associated organizational changes are of central strategic importance for automotive OEMs and their suppliers. In advance, it is important to clarify whether existing organizational structures and processes can actually be optimized with the help of the cloud. To this end, we regularly carry out benchmarks for well-known customers as a decision-making aid. In the presentation, we will present a benchmark with real productive jobs based on existing data in the customer's specific environment. Mapping the workflow with selected CAE applications in the cloud provided a realistic basis for evaluation of their benefits and costs. In addition to comparing runtimes and results of selected benchmark jobs, our experts tested the quality of remote work in a workstation scenario for selected finite element analyses (FEA), Computational Fluid Dynamics analyses (CFD) and iterative analyses.

  • Benchmark of Frequency Domain Methods for Composite Materials with Damage using LS-DYNA®

    Myeong-Gyu Bae, Seonwoo Lee (THEME Engineering, Inc.)

    The composite material is widely used in the structures as aircrafts, satellites, ships, automobiles, and so on which demand light weight and high performance. A various type of damage could occur through low-speed impacts and fatigue loads. It is generally known that the assessment of the natural frequency by vibration testing is a very attractive method as a Non-Destructive Test (NDT) and the vibration response of a composite structure can be utilized as an indicator of damage. In this paper, a desirable FE modeling technique regarding composite types (Laminated/Sandwich) and laminate methods of composite material were investigated using LS-DYNA. Firstly, according to the laminated properties of composite material (number of layers, anisotropy, shape, etc.), frequency responses were compared between the latest theories and the latest version of LS-DYNA. Secondly, various types of damage in cantilever beam with composite material were represented and estimated in FE model and those frequency responses were compared among experiments, LS-DYNA, and other FE code. Finally, delamination phenomenon in rectangular plate with composite material was represented and estimated in FE model and those frequency responses were compared between experiment and LS-DYNA. It was evaluated and verified that the prediction for the tendency of natural frequency using the frequency domain method in LS-DYNA could be appropriate for composite materials with or without damage.

  • Benchmark of LS-DYNA® for Off-shore Applications according to DNV Recommended Practice C208

    Marcus Lilja (DYNAmore Nordic AB)

    The use of non-linear FEA is growing in the offshore industry. Det Norske Veritas AS (DNV), one of the world’s largest ship and offshore classification societies to the maritime industry, has developed a Recommended Practice (DNV-RP-C208) on the usage of non-linear implicit finite element simulations in offshore applications. DNV-RP-C208 creates a de facto standard for structural load capacity analysis of off-shore structures. The Recommended Practice in combination with handbook formulas and empirical data create a de facto standard that will be used for investigations, studies and dimensioning off-shore structures for years to come. The Recommended Practice contains several benchmark problems with references solutions that can be used to verify a finite element software and the modeling methodology. This paper presents results from LS‑DYNA for a selection of these benchmark problems , ranging from beam bending problems with elasto-plastic behavior to instability and collapse analysis. All benchmark problems are solved using the implicit non-linear solver. Development of new features in LS‑DYNA and LS-PrePost® were necessary in order to complete the task. This paper presents results from the benchmarks, solution techniques, and the newly developed features.

  • Benchmark of Topology Optimization Methods for Crashworthiness Design

    C. H. Chuang, R. J. Yang (Ford Motors Company)

    Linear structural topology optimization has been widely studied and implemented into various engineering applications. Few studies are found in the literature which deals with nonlinear structures during vehicle impact events. One of the major challenges for nonlinear structural topology optimization is the unavailability of design sensitivities in impact simulations, due to the highly nonlinear and computationally intensive nature of these problems. In this paper, three commercially available methods are reviewed and discussed: Equivalent Static Loads (ESL), Hybrid Cellular Automata (HCA), and Inertia Relief Method (IRM). A vehicle structure, subjected to a full frontal impact, is used to compare the topology optimization results generated using HCA and IRM.

  • Benchmark Study on the AIRBAG_PARTICLE Method for Out-Of-Position Applications

    Wenyu Lian - General Motors, Dilip Bhalsod - Livermore Software Technology Corporation, Lars Olovsson - IMPETUS Afea

    The demands for developing safety restraint systems that perform well under Out-Of-Position (OOP) conditions have increased significantly in recent years. At the same time, the development of simulation capabilities for OOP have made progress in most major crash/safety software, such as the coupled Lagrangian-Eulerian approach (here referred to as AIRBAG_ALE) in LS-DYNA® by LSTC. Similar technologies are applied in MSC-Dytran by MSC and Madymo_CFD (Madymo) by TNO. A somewhat different approach is the FPM method in PAMCRASH by ESI. The AIRBAG_ALE capability in LS-DYNA, MSC-Dytran, and Madymo_CFD use loose-coupling techniques to couple the Lagrangian finite element airbag with a flow domain modeled with an Eulerian or ALE description of motion. PAMCRASH uses a particle based Lagrangian method, referred to as the Finite Point Method (FPM), for the description of the gases inside the airbag. All these methods share the same challenges associated with the coupling of the gas flow to folded bags under high speed deployment. Generally, the computations require considerable CPU power. The improved AIRBAG_ALE algorithm was developed in 2004 by Lian, Olovsson and Bhalsod [1]. In the same year, a set of benchmark problems were proposed by Lian at the SAE Conference [2]. A driver side airbag OOP study using AIRABG_ALE was presented in 2004 at LS-DYNA users’ Conference [3]. During the last few years, some modeling difficulties using AIRBAG_ALE have been reported. To overcome the difficulties, the Corpuscular Method (here referred to as AIRBAG_PARTICLE) was developed by Olovsson [4]. This study is intended as an evaluation of the accuracy, stability and efficiency of AIRBAG_PARTICLE compared to AIRBAG_ALE in OOP applications. More specifically, in this work the benchmark problems in ref. [2] have been studied using AIRBAG_PARTICLE. The results of AIRBAG_PARTICLE and AIRBAG_ALE are discussed.

  • Benchmarking Concrete Material Models Using the SPH Formulation in LS-DYNA®

    Brian Terranova, Research Engineer, University at Buffalo;, Andrew Whittaker, Professor and MCEER Director, Department of Civil, Structural, and Environmental Engineering, University at Buffalo;, Len Schwer, Schwer Engineering & Consulting Services, 6122 Aaron Court, Windsor, California, 95492, U.S.

    A model of a cylinder with a diameter and height of 400 mm was constructed in LS-DYNA using SPH particles to investigate the unconfined, quasi-static behavior of three concrete material models (i.e., MAT016, MAT072R3, and MAT159) in axial compression. Models were also prepared using Lagrangian solid elements and analyzed in axial compression to generate benchmark stress-strain data. Mesh refinement studies were conducted for the SPH cylinder to investigate the effects of particle spacing on predictions of elastic modulus and peak average axial stress. Analysis of the Lagrangian model showed post-peak softening for MAT072R3 and MAT159 and non-softening (i.e., perfectly plastic) behavior for MAT016. The SPH cylinder reasonably recovered the elastic modulus and peak average axial stress of the Lagrangian cylinder for all three material models, but the post-peak behavior predicted using the Lagrangian cylinder was not recovered using the SPH cylinder for material models MAT072R3 and MAT016.

  • Benefits of coupling FLACS-CFD® and LS-DYNA® for hydrogen safety applications

    L. Paris, M. Duchateau (Gexcon France), P. GLAY (DYNAmore France)

    There is a need for transitioning to an energy system with less greenhouse gas emissions and more sustainable energy production and consumption. A long-term structural change in energy systems is needed. Germany and France, among other countries, have decided to scale up the green hydrogen sector, with fundings of 9 billion and 7 billion euros respectively in the next 10 years.

  • Benefits of Scalable Servers with Global Addressable Memory for Crash Simulation

    Christian Tanasescu, Kevin Fox - SGI

  • Benefits of Scalable Server with Global Addressable Memory for Crash Simulation

    Christian Tanasescu, Nick Meng - SGI Inc.

    A wide variety of industries rely on mechanical computer-aided engineering (CAE) to improve design quality, reduce design-cycle time, and control costs. In designing automobiles, the manufacturers must meet different government regulations for vehicle safety. The maturity of Explicit Finite Element methods and the increasing computational power of today's computers have allowed the automotive industry to incorporate the Crash simulation technology in the critical path of the design process. As the application of Crash simulation moves from the component level analysis to the system level, the complexity and the size of the models increase continuously. By combining the capabilities of Intel® Itanium® 2 processors, the open-source Linux® operating system, and SGI® NUMAlink(tm) technology, the SGI Altix family of servers and superclusters with Global Addressable Memory (GAM) is uniquely able to meet the needs of advanced CAE simulation for product development. This paper will outline the features and benefits of using SGI Altix systems with Itanium® 2 processors running LS-DYNA. With the dramatic increase of the price performance of modern high performance computers, the model sizes of car crash and metal stamping simulations have been constantly increasing in recent years. Nowadays, a 1 Million element model is a common case. For large models, highly scalable computers and software play crucial roles in reducing turnaround time for simulations. The combination of the domain decomposition based LS-DYNA and the highly scalable SGI cc-NUMA system is an ideal solution for reducing simulation turnaround time. After briefly introducing the SGI cc-NUMA architecture and the benefits for scalable applications like LS-DYNA, based on recent performance data on the SGI Altix family of systems, we will address the simulation grid concept enabled by a large shared-memory architecture like the SGI Altix 3700. This aims at making the workflow more efficient, not only improving the solver performance. Multi-terabyte datasets can be loaded entirely into memory and operated upon without disk-swapping. In addition, expanding the processing paradigm with I/O and graphics pipes connected directly to the large memory, results in dramatically improved performance and foster collaborative engineering.

  • Benefits of the AMD Opteron Processor for LS-DYNA

    Dawn Rintala - Advanced Micro Devices, Inc.

  • Biomechanical analysis of whiplash injuries; women are not scaled down men

    Mordaka J., Gentle C. R. - Nottingham Trent University

    Whiplash is the most common soft tissue injury sustained in car accidents. The term is commonly associated with hyperextension of the neck as the head rotates backwards in rear end collisions but the exact injury mechanism is not fully understood because the neck is an anatomically and mechanically complex structure. Experimental studies of the mechanism of injury are limited by several ethical and practical factors, so biomechanical computational simulation, based upon experimental research and mathematical modelling, appears to be the most appropriate method of investigation. During the last decade, significant progress has been made in improving car occupant safety through the use of safety devices, such as airbags and advanced seat belts, as well as the construction of the car body itself. Much still needs to be done, especially for female occupants, because statistically they incur twice the risk of whiplash injury as male car occupants. No simple explanation has so far been found for this difference. It is thought that the anatomic dissimilarity of the sexes is the principal reason, but there are undoubtedly a number of secondary, sociological reasons: women tend to drive smaller cars than men and are more likely to be passengers. The lack of a full explanation arises from the fact that, although there have been several FE-models of the male cervical spine reported, female models are rarely documented. This paper addresses the problem by developing a biomechanical FEM model of the 50th and the 5th percentile female cervical spines, based on the earlier published male model created at the Nottingham Trent University, which relies on grafting a detailed biomechanical model of the neck and head onto a standard HYBRID III dummy model. All numerical analyses have been undertaken using LS-DYNA. Special attention was paid to the behaviour of the scaled down male model in comparison with the model, which included female characteristic features. FEM models of males and females in a representative seat were therefore subjected to 9.5 km/h rear-end simulated collisions and were compared against reported experimental tests. The detailed behaviour varied significantly with gender. The female models revealed greater and earlier peak horizontal acceleration of the head and smaller peak relative extension than the male models. It was concluded that the presented FE models were reasonably in accordance with available crash data on instrumented volunteers in terms of head motion.

  • BioRID II Dummy Model Development -- Influence of Parameters in Validation and Consumer Tests

    S. Stahlschmidt, B. Keding, U. Franz - DYNAmore GmbH, Germany, A. Hirth - DaimlerChrysler AG, Germany

    Whiplash injuries frequently occur in low speed rear crashes. Many consumer and insurance organizations use the BioRID II dummy, to assess the risk of whiplash injuries in car accidents. An LS-DYNA model of the BioRID II dummy has been developed by DYNAmore GmbH in cooperation with the German Automotive Industry. In the consortium a huge effort has been made to build a test database for the development of the FE-dummy. This paper describes the effort performed to generate the experimental data for material, component and full dummy validation. The dummy contains a considerable number of pre-stressed parts which can not be neglected since it stiffens the neck significantly. In order to capture the occurring pre-stresses appropriately the modeling techniques require the application of new features in LS-DYNA and specific handling during pre-processing. The paper describes the model and shows its performance in validation tests. Finally, different whiplash simulations are used to emphasize influences of selected parameters on injury criteria of the BioRID II model.

  • Biotex BigBag Simulation - LS-DYNA Airbag Tool Unusual Application

    C. Weinberger, B. Hirschmann (4a engineering); Johanna Eichelter (Franz S. Huemer)

  • Bird Strike Analysis of Aircraft Engine Fan

    Y.N. Shmotin, P.V. Chupin, D.V. Gabov - NPO SATURN, А.А. Ryabov , V.I. Romanov , S.S. Kukanov - Sarov Engineering Center

    Safety in accidental conditions is one of the important requirements an aviation jet engine must meet. It is known that one of quite possible and very dangerous accident is a bird strike into the engine in the flight. This case is characterized by the high speed impact of the bird onto rotating blades of the fan, causing large dynamic deformations of the blades and other elements which may lead to disintegration of the construction. That’s why numerical investigations of the bird strike are very important and should be implemented during design stage of a development process. The proposed paper presents some results of numerical simulations of dynamic deformations of the fan blades loaded by the bird impact, obtained by LS-DYNA code. There is an analysis of the numerical results and their verification by comparison with experimental data.

  • Bird Strike Analysis of Aircraft Engine Fan

    Y.N. Shmotin, P.V. Chupin, D.V. Gabov - NPO SATURN, А.А. Ryabov , V.I. Romanov , S.S. Kukanov - Sarov Engineering Center

    Safety in accidental conditions is one of the important requirements an aviation jet engine must meet. It is known that one of quite possible and very dangerous accident is a bird strike into the engine in the flight. This case is characterized by the high speed impact of the bird onto rotating blades of the fan, causing large dynamic deformations of the blades and other elements which may lead to disintegration of the construction. That’s why numerical investigations of the bird strike are very important and should be implemented during design stage of a development process. The proposed paper presents some results of numerical simulations of dynamic deformations of the fan blades loaded by the bird impact, obtained by LS-DYNA code. There is an analysis of the numerical results and their verification by comparison with experimental data.

  • Bird Strike and Fan Blade Out Using LS-DYNA at Snecma
  • Bird Strike and Fan Blade Out Using LS-DYNA at Snecma
  • Bird Strike Modeling Using a New Woven Glass Failure Model

    Lorenzo Iannucci, Mauricio Donadon - Imperial College London

    The bird strike impact problem is an increasing menace to the composite aerospace designer, especially since more aerospace components are being manufactured from composite materials. The LS-DYNA FE code is often used to model such an event as it can accurately represent the bird material behaviour and the contact between the bird and the structure. However, numerical simulations are usually accompanied by a parallel testing programme to validate the numerical simulations for some of these impact scenarios. The present paper described the implementation of an improved damage mechanics based material model to simulate the progressive failure of woven glass composites. A series of bird strike impacts on flat panels fabricated from low cost woven glass composite materials are used to validate the material model for practical composite component applications. The panels are modelled with shell elements only. The new material model can capture the strain rate enhancement to strength and strain observed for woven glass materials using a damage lag concept. A hydrodynamic model for the bird, based on 90% water and 10% air, is used to represent the behaviour of the bird for all impact scenarios considered. The bird is heterogeneous in nature, however, a uniform material behaviour is assumed with a geometry based on a 2:1 length: diameter ratio with a cylindrical body and spherical end caps using mesh less Smooth Particle Hydrodynamic (SPH) techniques. Appropriate contact definitions are used between the bird and the composite panel. The simulations results are compared to experimental results and conclusions drawn.

  • Bird Strike Simulation for BA609 Spinner and Rotor Controls

    Cheng-Ho Tho, Michael R. Smith - Bell Helicopter Textron Inc.

    Bird strike incidents are not uncommon and cost the U.S. civil aviation industry approximately $495 millions and 631,341 hours of downtime annually [1]. The development test to meet the bird strike certification requirements is very costly and time-consuming. This paper presents the bird strike analysis using the Arbitrary Lagrangian- Eulerian (ALE) technique in LS-DYNA for the BA609 spinner and rotor controls assembly shown in Figure 1. The objective is to reduce the development costs and cycle time while achieving weight-efficient resistant design by accurately predicting the composite failures and structural impact performance – with the ultimate goal of certifying by analysis only. The spinner assembly provides the swashplate drive load path and aerodynamic fairing for the rotor hub and controls. The failure of the spinner assembly could result in loss of the aircraft. Therefore the assembly must show compliance with “continued safe flight and landing” requirements following the high-energy bird impact. An idealized cylinder with hemispherical ends surrounded by air, which is modeled as 1-point ALE solid elements, is used to represent the bird model. The bird strike finite element model is validated through correlation with the tests conducted at the Southwest Research Institute of San Antonio in February 2005. This paper analyzes three most load-critical test conditions and evaluates the structural failures of the spinner assembly subjected to the bird strike dynamic loads. Figure 2 shows the correlation of one of the airplane mode shots for a 4.0-lb [1.8-kg] bird fired from a compressed gas gun at 240 kts [127.3 m/s] impact velocity targeting at the upper spoke of the spinner controls. Numerical results showed favorable correlation in terms of composite failure modes on the spinner cone, and the secondary impact fracture of the controls components such as upper spoke and cyclic link. The validated analytical model is used as a design support tool to produce useful information on the load mechanisms to guide the program for redesign.

  • Birdstrike onto the Composite Intake of a Turbofan Engine

    Marco ANGHILERI,Luigi CASTELLETTI, Fabio INVERNIZZI, Marco MASCHERONI - Politecnico di Milano, Italia

    Birdstrike is a menace for flight safety likely to have tragic consequences. In view of that, the efforts provided to design high-efficiency bird-proof structures are fully justified. In this work the impact of a standard 4-lb bird onto a nacelle made of composite material required for the certification of the component has been investigated using LS-Dyna 970. Initially, the dynamic behaviour of the composite material used in the manufacturing of the external skin panels of the intake was achieved by referring to specific experimental tests. It was observed, in fact, that the dynamic behaviour of the composite material has a deep influence on the failure mechanism of the structure. Subsequently, the numerical model worked out for the composite material was used to numerically reproduce a bird impact certification test. A SPH model of the bird validated in previous research was used. A good numerical-experimental correlation between experimental data and numerical results was obtained.

  • bjective evaluation of the quality of the FAT ES-2 dummy model

    Christian Gehre - PDB, Sebastian Stahlschmidt - DYNAmore GmbH, Matthias Walz - DAIMLER AG

    The numerical simulation is an essential part of the development of the passive safety of vehicles. Robust and predictable computational models are the base of the successful application of those simulations. Crash test dummies and their virtual counterparts are measuring tools to evaluate the injury risks to occupants in car crashes. The progress of those dummy models was remarkable over the past years. By increasing the quality, the potential of further significant improvements declines. Hence, the assessment of im- provements and their impact on the overall quality of simulations is getting more complex. Major improvements of sub-parts do not necessarily improve the overall performance of a model. There- fore, a standardised objective evaluation of models could ease the definition of priorities of model updates. Objective rating tools could help to solve this problem. These tools are calculating the level of correlation between two signals, usually coming from test and simulation. All signal ratings can be merged to global ratings. However, the analysis of only one loading case is not sufficient to calcu- late a reliable and a robust quality score of a dummy model. A more comprehensive approach is required to provide a valid rating for all relevant loading conditions. Furthermore, it must distin- guish between good and poor models and should correlate with user experiences. This paper presents results of a study to assess the quality of the LS-DYNA FAT ES-2. The data set comprises results of dummy certification tests as well as results of various component and sled tests. The extraction of the most relevant dummy responses was an essential part of the evaluation too. Finally, all scenarios were applied to different releases of the FAT ES-2. The cal- culated quality scores were verified with the experiences of users of the model. The findings of this study are limited to the FAT ES-2 model but can be transferred to another dummy model. However, the selection of loading cases and signals must be adjusted to each dummy.

  • Blast Detonated by Impact Simulation

    M. Büyük (Sabanci University), H. Balaban, U. Penekli (FE-Tech)

    The purpose of this study is to present parameters required for blast detonated by impact simulation in LS-DYNA with comprehensive approach and compare with AUTODYN results. Blast detonated by impact is a widely used method for controlled blast. However, design of the problem is more likely limited to simulation results. For a proper and reliable simulation, it has to be taken care of reacted and unreacted state parameters of detonative product, mesh size and method.

  • Blast Impact on Aluminum Foam Composite Sandwich Panels

    Rajan Sriram, Uday K. Vaidya - The University of Alabama at Birmingham

    Sandwich aluminum foam structures are being considered for energy absorption applications, crashworthiness, protection of transformer housings, and structural safety. Blast loading is one such phenomenon that is a potential threat to such structures. This study examines LS-DYNA modeling for aluminum foam sandwich composites subjected to blast loads. The sandwich composite was designed using polymer composite facesheets and aluminum foam as core. The core was modeled using material model 126 (*MAT_MODIFIED_HONEYCOMB). The facesheets were modeled using material model 59 (*MAT_COMPOSITE_FAILURE_SOLID_MODEL) and material model 161 (*MAT_COMPOSITE_MSE). 1 point corotational solid element formulation was used for the core and constant stress solid element formulation was used for the facesheets. LS-DYNA implementation of CONWEP blast equations (*LOAD_BLAST) was used to apply the blast load. The box design was evaluated using simulation and iterated until similar performance was achieved. The results were used to predict the modes of failure and energy absorption phenomenon. The simulation was also performed for different dimensions of box having different curvatures. The paper discusses details of the LS-DYNA simulation work and the parametric studies for the aluminum foam sandwich constructions.

  • Blast Mitigation Seat Simulations Using LS-DYNA®

    Buğra Balaban, Ahmet Mete Sabah

    Military vehicles are exposed to mine and explosive loads in operational conditions and the vehicle must have the appropriate protection level to prevent personnel injuries. Blast mitigation seats represent a critical component in ensuring personnel safety. In this study, we conducted mine blast simulations using the non-linear finite element code LS-DYNA® to examine the structural behavior of blast mitigation seats. The blast simulations were carried out in accordance with the requirements of NATO AEP-55 STANAG 4569 VOL-2. We employed the Structured Arbitrary Lagrangian-Eulerian (ALE) method for these simulations. The model encompassed an ALE domain, including soil, air, explosive definitions, and a Lagrange domain for the 4x4 military vehicle. To assess the impact of the explosive charge on the occupant, we utilized the LSTC Hybrid III 50th dummy. We measured force and acceleration outputs from the dummy and compared them with the allowable limits defined in NATO AEP-55 STANAG 4569 VOL-2.

  • Bolted Joint Connections of FRP-Components in Submarines Subjected to Underwater Shock

    A. Rühl, B. Özarmut, B. Hennings, O. Nommensen, A. Paul (thyssenkrupp Marine Systems)

    The application of fiber reinforced plastic (FRP) and sandwich components is an established practice at various locations in state-of-the-art submarines. Due to acoustic reasons, easy formability and low mass density at comparatively high strength values, these components bear a huge potential for buoyancy-related constructions. The shock-design and -calculation of these components as well as their connecting parts are crucially supported by Finite Element simulations using LS-DYNA. The present work shows an investigation of FRP-based bolted joint connections in today’s submarines and their connection to the pressure hull in terms of modelling and simulation. The transfer from detailed models to simulation of a full-scale shock submarine, as shown in Fig. 1, is presented and discussed.

  • Bolted Joint Representation in LS-DYNA to Model Bolt Pre-Stress and Bolt Failure Characteristics in Crash Simulations

    Shailesh Narkhede, Nitin Lokhande, Bhavesh Gangani, Ganesh Gadekar - Tata Motors Ltd.

    During the vehicle crash event (especially vehicles involving light and heavy commercial vehicles where bolted connections are predominantly used) bolted joints behavior, in terms of deformation and failure, play significant role in detecting the level of occupant protection offered by the vehicle structure. The current FE modeling techniques, for bolted joint representation in crash FE models, pose various limitations in terms of simulating the real life bolted joint behavior with explicit codes like LS-DYNA. The present bolt modeling techniques do not address the important aspects of bolted joint like • pre-load/pre-stress representation in the bolt, • bearing stresses between bolt shank and clamped plates, clamping forces between plates • Friction between bolts and plates and failure modeling of bolting joints. This paper describes FE modeling methodology, for bolted joint representation in crash FE models, for crash simulations using LS-DYNA. Two alternative options are proposed for modeling of bolted joint, either with beam element or with solid hexa elements so as to address the above mentioned aspects of bolted joint in crash simulations. The proposed FE modeling methodology is validated with theoretical calculations and experimental test results. The proposed bolt modeling methodology will help to achieve accurate prediction of structural behavior in crash load cases where bolted joints are predominantly used in crash load paths, such as cabin structure assessment with pendulum impacts, assessment of under run protections devices etc.

  • Book of Abstracts.pdf
  • Book of Abstracts.pdf
  • Boundary Element Analysis of Muffler Transmission Loss with LS-DYNA

    Z. Cui, Y. Huang (LSTC)

    This paper presents a case study of applying the boundary element method (BEM) in LS-DYNA for calculating transmission loss (TL) of mufflers. Both the three-point method and the four-pole transfer matrix method are used for calculating the transmission loss. The three-point method is easier to use, but it solves for the transmission loss only and nothing else. The four-pole method has the advantage of providing transfer matrix of the muffler, which contains important parameters when the muffler is connected to another muffler or other components in the silence system. Numerical predictions are examined by experimental results and theoretical results for all test cases. The results show that LS-DYNA can be used to perform muffler transmission loss analysis effectively.

  • Breaking Bad(ly) – Investigation of the Durability of Wood Bats in Major League Baseball using LS-DYNA®

    Eric L. Ruggerio, James A. Sherwood and Patrick J. Drane (University of Massachusetts)

    The bats used in Major League Baseball (MLB) are turned from a single piece of wood. Northern white ash had been the wood of choice until the introduction of hard rock maple in the late 1990s. Since the introduction of maple, there has been a measurable increase in the number of bats breaking into multiple pieces. These failures can be a significant factor during play, i.e. pieces of bats landing flying into the field of play, thereby distracting fielders from making the appropriate play for the given game situation. Observations of bat breakage in the field and in controlled conditions of lab testing of bats have shown the bat durability is a function of wood quality and bat profile. Wood quality is described by the density and the slope of grain of the wood. The bat profile is described by the variation in the diameter of the bat along its length. The bat properties that are preferred by players, i.e. low-density wood and a bat profile of a big barrel and a slender handle, are in direct contradiction with what makes for a durable bat. In this paper, LS-DYNA is used to develop calibrated models of the breaking of yellow birch wood bats in controlled lab conditions. The WOOD material model in combination with the ADD EROSION option using a maximum principal strain failure criterion was found to produce a credible simulation of the failure modes seen in wood baseball bats.

  • Brick versus shell elements in simulations of aluminium extrusions subjected to axial crushing

    Ø. Fyllingen - Bergen University College, O.S. Hopperstad, A.G. Hanssen, M. Langseth - Norwegian University of Science and Technolog

    In previous published literature, deviations in the mean crushing force and deformation pattern have been found between simulations with plane stress shell elements and experimental results for aluminium extrusions subjected to axial crushing. In the current study, simulations with solid and shell element models were carried out and compared to experimental results to study the influence of element type for this class of problems. The mean crushing force in the simulations using shell elements with through thickness stretch and solid elements were much closer to the experimental values than the plane stress shell elements. Concerning the deformation pattern, the solid element simulation exhibited a folding pattern much closer to the experimental one than the simulation with plane stress shell elements. To validate the conclusions drawn here, simulations of profiles with other geometries should be performed and compared to experimental results.

  • Brick versus shell elements in simulations of aluminium extrusions subjected to axial crushing

    Ø. Fyllingen - Bergen University College, O.S. Hopperstad, A.G. Hanssen, M. Langseth - Norwegian University of Science and Technolog

    In previous published literature, deviations in the mean crushing force and deformation pattern have been found between simulations with plane stress shell elements and experimental results for aluminium extrusions subjected to axial crushing. In the current study, simulations with solid and shell element models were carried out and compared to experimental results to study the influence of element type for this class of problems. The mean crushing force in the simulations using shell elements with through thickness stretch and solid elements were much closer to the experimental values than the plane stress shell elements. Concerning the deformation pattern, the solid element simulation exhibited a folding pattern much closer to the experimental one than the simulation with plane stress shell elements. To validate the conclusions drawn here, simulations of profiles with other geometries should be performed and compared to experimental results.

  • Broad-Spectrum Stress and Vibration Analysis of Large Composite Container

    Adrian Jensen, George Laird (Predictive Engineering, Inc.), Adrian Tayne (ECS Case, Becklin Holdings, Inc.)

    A large composite shipping container was analyzed for drop, impact, PSD random vibration and general stress analysis. The main shell of the container was a glass-fiber vacuum infused composite with closures made of aluminum. Lifting rings and other major structural load points were attached to the composite container using thick aluminum plates with preloaded bolts to distribute point loads into the shell. The uniqueness of this work was that one base model could address progressive composite failure whether under static conditions (implicit) or during drop test analysis (explicit) along with bolt preload and extensive nonlinear contact behavior at closures, skid plates and load rings. Analysis recommendations are provided for general implicit analysis for: (i) PSD random vibration with bolt preload; (ii) progressive failure of composites with *MAT_54; (iii) contact modeling and (iv) optimization of run times using MPP LS-DYNA ® . The explicit analysis of the container was rather simplistic but some comments will be made about the analysis setup and runtimes.

  • Buckling and post-buckling analyses of stiffened composite shells with inter-laminar damages

    Aleksandrs Korjakins, Patricia Kara, Kaspars Kalnins - Technical University, Riga

    In the present paper buckling and post-buckling response of axially loaded composite stiffened shell with inter-laminar damage regions have been solved using computer code LS-DYNA. Reduced number of layers and reduced stiffness in damaged region has been investigated. In addition skin delamination with contact model has been used for the analysis of the fracture toughness in the damaged regions. Energy release rates are calculated by Technique-B methodology, employing the 2D shell elements. Mode I and mode II fracture properties are obtained in the damaged regions of the carbon/epoxy composite stiffened shell. The influence of different damages regions on the buckling and post-buckling behavior of stiffened shell is investigated.

  • Buried Charge Engineering Model: Verification And Validation

    Len Schwer (Schwer Engineering & Consulting Services), Todd Slavik (LSTC)

    Livermore Software Technology Corporation (LSTC) recently added an empirically-based model for buried mine blast loading via the keyword *INITIAL_IMPULSE_MINE. This is an engineering model based upon experimental results, much like the air blast engineering model provided by *LOAD_BLAST_ENHNACED. The model is based on the work of Westine, et al. (1985) as presented, and extended, by Tremblay (1998). The implementation is applicable to flat (horizontal) and oblique (angled) target plates consisting of either shell or solid elements. Westine, et al. (1985) performed a series of buried charge experiments using thick (non-deforming) target plates with a set of impulse plugs inserted into holes drilled in the plate. The impulse plugs were spaced at 10 different ranges from the plate center, and hence angles from the center of the buried charge. Detonation of the buried charge forces the impulse plugs vertically out of the plate and measurement of their speed provides an estimate of the momentum (impulse) provided by the buried charge.

  • CAE Analysis of Passenger Airbag Bursting through Instrumental Panel Based on Corpuscular Particle Method

    Y. Feng, M. Beadle (Jaguar Land Rover)

    The safety regulation requires that passenger airbag (PAB) to deploy into working position in time without causing any fragmentation of its surrounding structure. Due to the significant load of airbag deployment and its complex unfolding process, it is always a challenge to design a PAB system which enables airbag safely bursting through instrumental panel. A CAE based approach has been developed at Jaguar Land Rover (JLR) to lead the passenger airbag system design. The foundation of the CAE approach is to model the airbag bursting loading condition representatively.

  • CAE Applications for Balanced Curtain Airbag Design Meeting FMVSS226 and System/Component Performance

    Bill Feng (Jaguar Land Rover)

    Curtain airbag is a key restraint component to protect occupants in the events of side impact (referred as First Impact) and rollover (referred as Second Impact). In the curtain airbag design during the vehicle programme, following requirements dominate the design. FMVSS226 Ejection Mitigation (EjM) requires curtain airbag provide adequate protection for rollover event. Restraint system performance for legal and consumer tests, such as FMVSS214 and NCAPs, requires good occupant head protection in the first impact. TWG Out-Of-Position (OOP) requires low risk deployment of curtain airbag for the occupants seating in out-of-position. In addition, curtain airbag design should ensure the integrity of surrounding trims, such as pillar trims, during the deployment at different environmental conditions. In 2011, NHTSA introduced the new regulation for rollover protection, FMVSS226 Ejection Mitigation. The requirement demands increased occupant containment in rollover and side crashes for belted/unbelted occupants and third rows of seating. The rule requires the linear impact tests at two energy levels and two inflation times (e.g. 278J@1.5s and 178J@6s). The results of this requirement are the introduction of larger curtain airbag with higher power inflator for longer inflation. Since then, FMVSS226 EjM has become a key loadcase to define the curtain airbag inflator selection and curtain airbag design. However, the introduction of larger curtain and larger inflator has great challenge to the integrity of curtain airbag and surrounding trims, and OOP performance as well. Therefore, it is important that balanced performances between restraint system requirements and component requirements during the process of curtain airbag design and inflator selection. In this paper, CAE applications and studies have been conducted to gain the understanding of energy requirements and managements for balanced curtain design airbag to meet the multiple requirements on restrain system performance, EjM, OOP and component integrity.

  • CAE as a Service as Cloud Platform for the Full LS-DYNA Simulation Process

    A. Geiger, K.-H. Hierholz, C. Neimöck (T-Systems)

    Mit CAE as a Service stellt T-Systems eine Cloud-basierte Lösung für den gesamten CAE Prozess vom Infrastruktur- bis zum Softwarelayer mit dynamisch skalierbarem Durchsatz und Leistungsfähigkeit. Use cases sind u.a. (a) HPC Spitzenlastabdeckung für Durchsatz- und Problemgrößen-Peaks, (b) Bereitstellung des vollständigen CAE Prozesses mit Pre-/Solver-/Postprocessing und Simulation Data Management als Service, (c) Bereitstellung von sicheren und skalierbaren Kollaborationsumgebungen für die gemeinsame Entwicklungsarbeit zwischen OEM und OES.

  • CAE Correlation with Test for Door Slam in Nonlinear Dynamic Stress and Fatigue Life Analysis

    Guangtian Gavin Song, Rana Sanghera, Surya Yerva, Hamid Keshtkar - DaimlerChrysler Corporation

    In automotive industry, CAE fatigue life analysis is very important in durability evaluation and product optimization to dramatically reduce the design period and minimize the expensive durability testing. In the past time, CAE fatigue life analysis is constrained to the linear stress based methodology in the local strain approach. Generally, the linear stress based methodology is stress analysis with linear material properties. Contact surface could be defined if needed for large deformation and rotation dynamic problem. Then, the stress time history result is retrieved to input to further fatigue life analysis or firstly converted to nonlinear stress with Neuber’s rule with considering plastic deformation effect. But in some cases, the structure’s large deformation and rotation movement can make large area plastic deformation. Under those cases, the linear stress based methodology can’t precisely predict the load path, and further affect the following fatigue analysis accuracy. Nonlinear dynamic method with material nonlinearity should be used in stress prediction for those cases, and the principal strain time history retrieved from nonlinear stress analysis can be directly input to fatigue analysis. This investigation takes door slam as example with LS-DYNA as solver in both the linear and the nonlinear methodology based stress analyses and with Fe-Fatigue in fatigue life analyses to show the linear stress based methodology more conservative and the nonlinear stress based methodology more accurate together with strain life method for low cycle fatigue in nonlinear dynamic problem.

  • CAE Data Management and Quality Assessment of LS-DYNA Crash Models using V-CESS

    Matthias Eick, Dr. Lars Fredriksson, Dr. Jochen Seybold - Altair Engineering GmbH

    The meshing, modeling and evaluation of LS-DYNA crash models for vehicle crash simulations is constantly subjected to an increase in complexity, since the model sizes grow, several vehicle variants are instanced from one single CAE data set and since the number of load cases and the requirements on the evaluation quality are constantly increasing. Current models sometimes contain more than 1000 different components and 1 million elements. In recent years, the model complexity has also been increased since interior parts and dummy models are included. The increased complexity makes it difficult to handle the models since changes in parts in many cases influence many different vehicle variants and load cases. V-CESS is a "Virtual Process Automation Framework" designed to simplify and standardize this type of CAE processes and is developed together with DaimlerChrysler AG, department PBE/DAM [3]. The system was developed in a pilot project with the aim to manage the CAE data of the "Sprinter Successor" in order to create, manage and evaluate crash models in LS-DYNA. In engineering projects together with DaimlerChrysler AG, department PBE/DAM, we have shown that the return on investment of V-CESS is reached at about 1.5 virtual prototypes. The meshing cost can be reduced by 15% and the engineering cost saving is approx. 30%.

  • CAE Data Management from a single Geometry Revision to multi-disciplinary Simulation Results

    Jens Philippeit, Zoran Petrovic - Siemens Product Lifecycle Management Software

    Development processes for more complex new products and better performance require necessarily verification through digital simulation. Due to shortened development cycles the time to answer questions about reliable product characteristics is cut off and an efficient change management has to be established in the process chain from CAD to CAE. Normally CAE processes start with CAD data from a PDM system. To start CAE analysis it is required to easily filter different product configurations from latest CAD data, automatically prepare data for simulation (i.e. batch meshing) and pass this to simulation processes. Depending on type and number of simulations and change rate of CAD it will be shown what tools a simulation data management system can provide to efficiently guide the CAE process and shorten the cycles between CAD and CAE. Optimized data handling as well as integration of CAE tools will be the key for synchronized and economic development processes. Making decisions on digital simulations mostly involves different simulation disciplines. Therefore decisions for digital optimizations have to run in a multi-disciplinary context, access the same data sources and lead to a common decision of all involved analysis. By establishing a Simulation Data Management this can be done very efficiently keeping the data together and running as fast as possible a decision making process. Tools like workflows and decision tables will support this process.

  • CAE Data Management from a single Geometry Revision to multi-disciplinary Simulation Results

    Jens Philippeit, Zoran Petrovic - Siemens Product Lifecycle Management Software

    Development processes for more complex new products and better performance require necessarily verification through digital simulation. Due to shortened development cycles the time to answer questions about reliable product characteristics is cut off and an efficient change management has to be established in the process chain from CAD to CAE. Normally CAE processes start with CAD data from a PDM system. To start CAE analysis it is required to easily filter different product configurations from latest CAD data, automatically prepare data for simulation (i.e. batch meshing) and pass this to simulation processes. Depending on type and number of simulations and change rate of CAD it will be shown what tools a simulation data management system can provide to efficiently guide the CAE process and shorten the cycles between CAD and CAE. Optimized data handling as well as integration of CAE tools will be the key for synchronized and economic development processes. Making decisions on digital simulations mostly involves different simulation disciplines. Therefore decisions for digital optimizations have to run in a multi-disciplinary context, access the same data sources and lead to a common decision of all involved analysis. By establishing a Simulation Data Management this can be done very efficiently keeping the data together and running as fast as possible a decision making process. Tools like workflows and decision tables will support this process.

  • CAE Process Support by MIDAS and MEDINA

    Sattler M., Finkel A.

  • CAE Simulations for Passive Safety focused on the Porsche Cayenne - the Transition to New Technologies

    Erich Schelkle, Herbert Klamser - Dr. Ing. h.c. F. Porsche AG

    Simulation technologies are methods which have been traditionally applied in automotive engineering for a long time. Over the decades, enormous progress has been achieved in both, the simulation methods and the CAE-programs used. Thanks to the high efficiency levels of the current computer generation and the use of economically priced commercially available hardware such methods are being applied on a widespread basis today. Visionary concepts of the past are turning into reality. When considering the process of automotive engineering and the futuristic potential inherent in those methods, it becomes obvious that virtual automotive development still is in its infancy. This applies to the whole range of options from the coupled parallel/sequential simulation of manufacturing processes to the cross-functional simulation, including efficient management systems designed to handle the entire CAE process [1]. At the same time, the CAE model transfer between the various expert departments on the one hand and between the OEMs and the system suppliers on the other has to be optimized while developing suitable documentation- and DataMining systems [2]. What must also be mentioned is the need for continuous updating of the traditional methods in terms of numerical data and technical content. Currently, in the early phases of automotive engineering, the development activities are mostly handled in a sequential manner [3,4]. That is where the newly conceived CAD/CAE methods come in quite handy: They allow component geometries to be prepared on the basis of topologies and parameters and subsequent modifications to be implemented quite rapidly [5]. For the synergy effects of these innovative design tools to be made full use of it is necessary, however, to combine the parametric concept geometry model with mathematical optimization methods. This approach allows the inherent design potential to be fully opened up and thus the defined targets to be reached in the most optimum way [6]. Even though such numerical design strategies have already been used in certain areas, their wide-spread and consistent introduction into conceptual design is yet to come. It is with these innovative CAD/CAE strategies that the present paper is dealing.

  • CAE Validation Study of a Side Window Impact using Plexiglas Materials

    D. Lopez Ruiz (Tecosim Technische Simulation), A. Rühl, Prof. S. Kolling (THM Giessen), E. Ruban, B. Kiese­wetter, S. Ulzheimer (Evonik Industries)

    An experimental and numerical study regarding the head impact on a side rear window was performed. Based on several years of material development and manufacturability (Evonik Industries AG), the expert knowhow in material testing and LS-DYNA material implementation (Giessen Institute of Mechanics and Materials) and the CAE user experience (TECOSIM Technische Simulation GmbH) and in closer cooperation between all parties, it was decided to start a development study. The outcome of the study should show the behavior of different PLEXIGLAS® (PMMA) windows using different PLEXIGLAS® grades and possible feasible combinations.

  • CAE Workflow Coupling Stamping and Impact Simulations

    Henry Shibayama, Rohit Ramanna, Sri Rama Murty Arepalli, Arthur Camanho (ESI)

    Visual-Environment is an open and integrated user environment enabling simulation and analysis across multiple domains for efficient product engineering. A CAE workflow has been developed chaining stamping and impact simulations. The workflow originates from stamping matrix design (performing stamping simulations) to impact simulations considering the residual stress and thickness variation due to stamping process. The objective to be achieved is the creation of a fast end-to-end workflow, aiming at accurate impact simulations while taking into account the results from manufacturing processes. So far, impact simulations are performed considering the stamping simulation results. The next step of the project is to perform welding simulations and consider its residual stresses and distortion, aiming at more accurate impact simulations, through chaining and considering the process effects coming from stamping and welding analysis as well. Visual-Diemaker is a software tool focusing on the design of the stamping matrix, with some feasibility tools, such as tipping evaluations. Visual-Diemaker also integrated some tools for the set-up of stamping simulation. For development and evaluation of the methodology all simulations were performed using PAM-STAMP. Generated output results were M01 files (one per component), containing the residual stress and thickness variation. In a first step Visual-Process, a mass-customization and automation tool to support the automation of CAE tasks, converts automatically M01 (PAM-STAMP) file structure to LS-DYNA® key-words respectively syntax (using ELEMENT_SHELL_THICKNESS and INITIAL_STRESS_SHELL). As a second step, the same tools allows the CAE engineer to open the LS-DYNA impact model in Visual-Environment, then setting the components to be chained with the stamping results, define the reference nodes for the construction of a reorientation matrix, and finally define a different number of integration points through the thickness. This process basically reads and converts the M01 syntax and also adds the INCLUDE_STAMPED_PART syntax into the global impact model which references the converted M01 file. The purpose of the project is the ability of automated chaining between manufacturing and performance structural simulation in one and same environment. After achieving this development goal, further implementation and industrialization of this kind of analysis methodology into a CAE industrial department is expected as a reliable and fast way to proceed with chained analysis using different CAE solver.

  • Calculating Electromagnetic Field (EMF) Distortion to Maintain and Secure Electric Transmission Lines

    John Puryear, David Rodriguez (ABS Consulting), Iñaki Çaldichoury (Livermore Software Technology Corporation)

    Critical to the electric power grid are the high voltage transmission lines. These assets are geographically dispersed and typically transverse large distances across remote areas. Those attributes make them challenging to maintain and physically secure. Electrical power system operators are continually improving data acquisition and interpretation to draw new inferences about system performance. These advances raise the possibility of monitoring the power lines’ electromagnetic fields (EMFs) and using them as “sensors” with a range of potential applications. One possible application is ballistic detection. A common problem for utilities is ballistic damage to insulators. Were reliable ballistic detection available, inspection could be triggered by actual gunshots and restricted to where gunshots occurred. With growing concern of attacks to the power grid, being able to detect gunsh ots is additionally attractive. A bullet passing near a power line is a conductor passing through a large EMF. This physical condition raises the possibility that a change in the line signal could be detected when a bullet passes near the cable. LS-DYNA ® ’s electromagnetic (EM) solver was used to calculate the change in line signal due to a bullet passing nearby. Another potential application of power lines as sensors is structural health monitoring. Transmission lines themselves are conductors within a baseline EMF. Displacements caused in service conditions (galloping conductors or damaged insulators) or by extreme events (seismic damage or high winds), change the mutual inductance between the cables. This scenario served as a second case study for calculating the effect of an external event (kinematic motion of cables) on the cable signal. Finally, metal theft or willful damage is a persistent threat to utility assets, and the capability of sensing and identifying the location of an intruder anywhere along the line would assist in apprehending the intruder and deter future intrusions. In principle, the power line can function like existing electromagnetic devices that sense intrusion. This possibility was investigated using the EM solver. Specifically, a finite element model including an energized transmission cable and intruding truck has been used to calculate any change in cable current density due to the presence of the truck. In this paper, the motivation for analyzing these case studies, the details of the studies themselves and results from the calculations are presented. In addition, recommendations for future work are discussed.

  • Calculation and Validation of Material Tests with Specimens Made out of Filled Elastomers

    P. Thumann, K. Swidergal, Prof. M. Wagner (OTH Regensburg)

    In deep-drawing dies for steel sheet parts of car bodies huge masses are moved. To prevent vibrations, which occur by sudden acceleration or stopping of those masses, elastomeric tubular dampers [1] are used. The dampers are made out of carbon filled elastomers. A good knowledge about the material behaviour of metals is available.

  • Calculation of the Velocity and Shape of an Explosively Formed Projectile (EFP) Using Axisymmetric ALE

    John Puryeara, Ben Harrison, ABS Group, 140 Heimer Rd. Suite 300, San Antonio, TX;, Lynsey Reesec, Michael Oesterle, NAVFAC Engineering and Expeditionary Warfare Center, Port Hueneme, CA

    The symmetry common to most explosively formed projectiles (EFPs) permits their characterization using 2D axisymmetric analysis. Formation of an EFP entails volumetric expansion of the explosive and extensive plastic flow of the metal plate, both of which can be calculated using an Arbitrary Lagrangian Eulerian (ALE) method. Accordingly, the 2D axisymmetric ALE capability in LS-DYNA® was applied to calculate the velocity and shape of an EFP. The methodology was validated against EFP velocity and shape measurements published in SAND-92-1879 by Hertel.

  • Calibration and Application of GISSMO and *MAT_258 for Simulations Using Large Shell Elements

    Joakim Johnsen, Jens Kristian Holmen (Enodo AS), Gaute Gruben (SINTEF Industry), David Morin, Magnus Langseth (Norwegian University of Science and Technology (NTNU)

    For many industrial applications finite element (FE) models are becoming increasingly large, making shell elements a necessary tool to maintain a reasonable computational time. Shell elements describe a plane stress state and phenomena like local necking and failure under bending must be appropriately dealt with. Thickness-to-length ratios larger than two are not uncommon for shell elements. This is often larger than the elements used for material model calibration and can sometimes lead to challenges in describing the geometry and the stress state. In this study, we evaluate the accuracy of *MAT_258 and a standard GISSMO calibration. The material and component tests are made of Docol 1400M. Results from *MAT_258 and GISSMO are compared to several component tests spanning a wide range of stress states.

  • Calibration and Experimental Validation of LS-DYNA Composite Material Models by Multi Objective Optimization Techniques

    Stefano Magistrali - Omega Srl, Research and Innovation Centre, Marco Perillo - EnginSoft SpA

    Experimental quasi-static tensile and impact tests were conducted over two different types of composite laminates and four different types of sandwich laminates, in order to evaluate their basic mechanical characteristics and energy adsorption capability. The second phase of this research work approaches and resolves the calibration of the mechanical parameters included into the LS-DYNA composite material models. This calibration starts and is based on the material physical properties derived from the test results. LS-DYNA model parameters, model constrains and objectives defining the problem have been studied and analysed by using modeFRONTIER. modeFRONTIER is a multi-objective and multi-disciplinary integrated platform. Input parameters were varied into a controlled range. This allows to find quickly and to define accurate model configuration as well as model sensitivity to those parameters, leading to reliable numerical models for impact simulations. Accurate comparison of simulation results with experimental material results is crucial to achieve optimum and precise material models. The present research study offers also an understanding of the effect of numerical input parameters and variables on sandwich laminates structural response in terms of absorbed energy, maximum energy, maximum force and curve morphology. Calibration of material models, able to reproduce the effective impact behaviour of real composite materials, is fundamental in order to simulate general crashworthiness problems. This kind of approach allows either to understand variable influences on composite dynamic structural response or to get improved solution for industrial case studies.

  • Calibration of *MAT_258 with a Lode dependent fracture surface and its application in bending of high-strength steel

    J. Holmen, J. Johnsen (Enodo), D. Morin, M. Langseth (NTNU)

    *MAT_258 (*MAT_NON_QUADRATIC_FAILURE) is a through-thickness failure regularization model for shells in LS-DYNA. In this model the failure indicator is computed as a function of both the size of the element and its bending-to-membrane loading ratio. The constitutive behavior and fracture surface in *MAT_258 are represented by well-known analytical expressions which simplify calibration. We present the calibration process for *MAT_258 with a three-parameter Extended Cockcroft-Latham fracture surface for the high strength steel Docol 1500M. The material card is applied in shell element simulations of three-point bend tests.

  • Calibration of GISSMO Model for Fracture Prediction of A Super High Formable Advanced High Strength Steel

    Xiaoming Chen, Guofei Chen, Lu Huang, Ming F. Shi, United States Steel Corporation

    Advanced high strength steels (AHSS), due to their significantly higher strength than the conventional high strength steels, are increasingly used in the automotive industry to meet future safety and fuel economy requirements. Material failure that was rarely observed in crash tests a decade ago occurs more frequently in AHSS parts due to the relatively low ductility when compared to conventional steels. In computer aided engineering (CAE) crash analysis, a fracture model is often integrated in the simulations to predict the effects of material failure during crash events. In this paper, parameters of a fracture criterion are generated and calibrated for a Super High Formable (SHF) Steel with a minimum tensile strength of 1180 MPa (1180SHF).

  • Calibration of Material Models for the Numerical Simulation of Aluminium Foams – MAT 154 for M-PORE Foams @ 3 Loads

    Vito Primavera, Marco Perillo (EnginSoft SpA), A. Carofalo, M. De Giorgi, R. Nobile (University of Salento)

    Metallic foams are very promising for engineeristic applications due to their peculiar characteristics, like the high energy-absorbing property coupled with a reduced weight. Even if applications can be widespread in several fields, such as automotive, civil, aerospace, etc., industrial requirements are still far to be fully accomplished, especially in terms of technological processes and a whole mechanical characterization. Material modeling of metallic foams, like the aluminium ones, is a crucial point for performing accurate numerical simulations along with the design phase. Material models available in the explicit, non-linear finite element code LS-DYNA® represent a very efficient way to handle and to investigate foam behavior. An extended experimental/numerical activity has been set out at the aim to calibrate and validate suitable material models with respect to different aluminium foams and several loading conditions. While a previous phase of the activity [1] has been focused on the assessment of a procedure addressed to point out, starting from the available experimental data, the key points of material model calibration, the current activity has been focused on the procedure application, i.e. the exploitation of the built-up methodology in respect of calibration of M-PORE open cells aluminium foam at three different loading conditions. A good number of foams material models are available in the LS-DYNA database, and further in the last years different enhancements have been performed at the goal to include the physical phenomenons able to increase the accuracy of the models. Amongst the available ones, MAT 154 (MAT_DESHPANDE_FLECK_FOAM) has been here chosen because it provides satisfactory results compared with the experimental ones, but at the same time it still requires to be studied for more loading conditions. Since the calibration process requires to optimize the material model free parameters according to different objectives, LS-DYNA has been coupled with modeFRONTIER®, Process Integration and Design Optimization software platform. Once all the FE (Finite Element) models related to the corresponding experimental tests have been integrated into modeFRONTIER, a first sensitivity analysis has been performed at the purpose to get confidence with MAT 154 behavior and then an efficient optimization phase in order to pursue the numerical configurations satisfying the different targets provided by experimental tests. Efficient and intuitive post-processing tools have been applied firstly to get a deep knowledge of the investigated phenomenons and eventually to look for the best solutions.

  • Calibration of Six Constitutive Material Models for Geomaterial

    R. Nasouri (University of Texas), H. Rokhy (Amir Kabir University), A. Matamoros, A Montaya (University of Texas), R. Backzadeh (Urmia University)

    Recently, several constitutive material models have been developed and added to the LS-DYNA library to predict concrete geomaterial behavior. These developments were established merely from using concrete compressive strength, which limits the level of robustness in capturing actual concrete behavior. This study focuses on developing a simplified approach to calibrate six constitutive material models including Soil and Foam, Pseudo Tensor, Geological Cap Model, Concrete Damage Model Rel-3, Johnson Holmquist, and Continues Surface Cap Model against Triaxial and Hydrostatic Compression Tests (TXC and HCT) data. Comparisons between individual numerical results were performed to evaluate whether accuracy can be offered through a corresponding constitutive material model. The presented calibration method can also be applied to different geomaterials such as rock and soil.

  • Capabilities of Result Visualization in LS-OPT V4.1 - Demonstrated by Means of Industrial Problems

    Katharina Witowski, Heiner Müllerschön - DYNAmore GmbH

    During the last decade the optimization software LS-OPT has been used for design optimization, for DOE-studies, for system identification and for stochastic investigations in many industrial projects. LS-OPT became over the years a highly sophisticated software tool with very effective and reliable optimization methodologies particular suitable for highly nonlinear problems. This paper illustrates the capabilities of LS-OPT by means of several industrial applications. The focus is on the new post processing features of LS-OPT 4.1 such as visualizing results of multi-objective optimization, multiple load case optimization, sensitivity analysis and the visualization of curve data evaluated on the basis of meta-models. Of course, the objective and the setup of the optimization problems is discussed and demonstrated.

  • Car Body Optimization Considering Crashworthiness, NVH and Static Responses

    Phani Adduri, Gary Quinn, Juan P. Leiva, Brian C. Watson (Vanderplaats Research and Development, Inc)

    This paper demonstrates a design system to efficiently perform optimization based on responses computed from multiple LS-DYNA® analyses while also taking into consideration the linear loading conditions such as the ones for NVH and Static responses. The proposed design system, ESLDYNA, is based on the Equivalent Static Load (ESL) method, which requires the iterative process of non-linear structural analysis (LS-DYNA) and linear structural analysis and optimization (GENESIS). Unlike general purpose optimization software packages, it does not require a large number of analysis calls even for problems with large numbers of design parameters. Therefore, large-scale optimization techniques, such as topology, topometry and topography, can be easily employed. Several examples using different optimization techniques will be presented. One of the examples will include optimizing the design for frontal crash, normal modes and static loading conditions simultaneously.

  • Cardiac Electrophysiology Using LS-DYNA®

    Pierre L’Eplattenier, Iñaki Çaldichoury, Facundo Del Pin, Rodrigo Paz, Attila Nagy, Dave Benson (Livermore Software LLC)

    Heart disease is among the leading causes of death in the Western world; hence, a deeper understanding of cardiac functioning will provide important insights for engineers and clinicians in treating cardiac pathologies. However, the heart also offers a significant set of unique challenges due to its extraordinary complexity. In this respect, some recent efforts have been made to be able to model the multiphysics of the heart using LS-DYNA. The model starts with electrophysiology (EP) which simulates the propagation of the cell transmembrane potential in the heart. This electrical potential triggers the onset of cardiac muscle contraction, which then results in the pumping of the blood to the various organs in the body. The EP/mechanical model can be coupled with a Fluid Structure Interaction (FSI) model to study the clinically relevant blood flow parameters as well as valves or cardiac devices. This paper concentrates on the EP part of the model. Other papers in this conference will present the mechanical and FSI parts. Different propagation models, called “mono-domain” or “bi-domain”, which couple the diffusion of the potential along the walls of the heart with ionic equations describing the exchanges between the inner and the outer parts of the cells have been implemented. These models were first benchmarked against published results obtained from other EP research codes on a simple cuboid heart tissue model. More recently, we also performed benchmarks proposed by the FDA against analytical solutions. Other features of the EP solver will also be presented such as coupling between the tissue and a surrounding bath, coupling between mono and bi-domain in the same model, and coupling of the mono/bi domain models with a Purkinje Network. Finally, multi-physics simulations with the EP coupled with mechanical deformation and FSI for the blood flow will be presented. These models include arteries and valves for a realistic model of a ventricular pump.

  • Cardiac Electrophysiology using LS-DYNA®

    Pierre L’Eplattenier, Sarah Bateau-Meyer, Dave Benson, Livermore Software Technology Corporation, Livermore, California 94551;, Vikas Kaul, Carl Schu, Mark Palmer, Darrell Swenson, Joshua Blauer, Medtronic plc, Minneapolis, Minnesota 55432

    Heart disease is among the leading causes of death in the Western world; hence, a deeper understanding of cardiac functioning will provide important insights for engineers and clinicians in treating cardiac pathologies. However, the heart also offers a significant set of unique challenges due to its extraordinary complexity. In this respect, some recent efforts have been made to be able to model the multiphysics of the heart using LS-DYNA.

  • Cardiac Electrophysiology using LS-DYNA®

    P. L’Eplattenier, I. Caldichoury, K. El Houari (Ansys/LST)

    Heart disease is among the leading causes of death in the Western world; hence, a deeper understanding of cardiac functioning will provide important insights for engineers and clinicians in treating cardiac pathologies. However, the heart also offers a significant set of unique challenges due to its extraordinary complexity. In this respect, some recent efforts have been made to be able to model the multiphysics of the heart using LS-DYNA.

  • CASE STUDY – Material models for depiction of unloading in low speed crash applications

    B. Hirschmann, Y. Nakagawa, N. Matsuura (Honda), H. Pothukuchi, M. Schwab (4a engineering)

    Computer simulation is used in many fields of automobile development to shorten the development term and reduce tests. Large plastic parts such as instrument panels and bumper fascia take a lot of time to make a die, so it is necessary to determine the part shape quickly to shorten the term. Therefore, performance verification by simulation is important. However, due to issues such as material property and complicated part shapes, reproduction of phenomena such as deformation and failure are sometimes not sufficiently accurate in simulations of plastic parts. Creating a die, testing part, and evaluating its performance in such a situation may raise the possibility of inadequate performance. In that case, it is necessary to modify the die, which requires extra cost and time. Therefore, high simulation accuracy is necessary to avoid such risks.

  • Cause Investigation of Capsizing Accident of Ro-Ro Ferry Ship using Marine Accident Integrated Analysis System

    S. Lee, J. Lee, J. Park, T. Jung (Korea Maritime & Ocean University)

    Ro-Ro Ferry ship was capsized and was sunk down to the bottom in the sea water due to the rapid turning for the several reasons, such as lack of stability and poor lashing, etc. Objective of this study is to investigate the capsize accident cause by full-scale ship rapid turning simulation through the comparison with AIS track in this capsize accident, considering several factors, such as GoM, ship velocity, rudder angle, etc., and using Marin Accident Integrated Analysis System (highly advanced M&S system of FSI analysis technology). MAIAS of full-scale ship turning simulation are verified by comparison with maneuvering performance sea trial test result of initial building ship. Several things were carried for this rapid turning simulation, such as accurate ship model modification using floating simulation according to hydrostatic characteristics of loading conditions, and investigation of cargo loading arrangement and cargo lashing states. There was relatively good agreement of full-scale ship sea trial turning simulation with sea trial test result, and good prediction of cargo loading arrangement and cargo lashing states comparing to the AIS track in this capsize accident.

  • Cause Investigation of Flooding & Sinking Accident of Ro-Ro Ferry Ship using Marine Accident Integrated Analysis System

    S. Lee, J. Lee, J. Park, T. Jung (Korea Maritime & Ocean University)

    Ro-Ro Ferry ship was capsized and was sunk down to the bottom in the sea water due to the rapid turning for the several reasons, such as lack of stability and poor lashing, etc. Objective of this study is to figure out the air pocket existence in the flooding & sinking accident using Marin Accident Integrated Analysis System (MAIAS; highly advanced M&S system of Fluid-Structure Interaction analysis technology). Several things were carried for this investigation of air pocket existence, such as accurate ship posture track according to accident duration using several accident photos and movies, precise ship and cargo moving track and sea water inflow amount according to accident duration using floating simulation and hydrostatic characteristics program, accurate understanding of exterior openings and interior paths of sea water inflow, simulation of sea water inflow using flooding & sinking simulation and calculation of exterior openings & interior inflow paths. There was relatively good prediction of air pocket existence.

  • Ceramic-rubber hybrid materials – A way to sustain abrasive heavy impact applications

    M. Herr (AC2T research), M. Varga, L. Widder (AC2T), J. Mermagen, S. Rodinger, W. Harwick (Fraunhofer EMI)

    Transport of raw materials in industrial applications usually involves highly abrasive processes and requires wear protection for a reliable, long operation period. At transfer points such as between conveyer belts additional impact loads can limit the lifetime. For such conditions rubber-ceramic hybrid materials can extend the lifetime multifold by combining the wear resistance of ceramics with the impact resistance of rubbers.

  • Certification by Analysis of a Typical Aircraft Seat

    N. Dhole, V. Yadav, G. Olivares (National Institute for Aviation Research)

    Advancements in computer hardware in recent years have made it possible to solve complex real world problems using finite element methods (FEM). Full scale dynamic certification testing of aircraft seats is a very complex, expensive and time consuming process. A high acceleration pulse is applied on the seat structure in a short duration of period, and the seat structure has to pass stringent FAA certification criteria. FAA and the aircraft industry are working together to reduce the cost and time required for certification of the seat while improving occupant safety. This is being achieved by using a process known as Certification by Analysis or CBA where the seat is certified using finite element methods. The process and guidelines for CBA are described in advisory circular AC 20-146 developed by the FAA. As per the AC 20-146, FE models can replace the actual dynamic testing scenarios such as: 1) demonstrating compliance to standard test requirements for changes to a baseline seat design, 2) establishing the critical seat installation/configuration in preparation for dynamic testing. This paper describes in detail different techniques that can be used for the validation of a FE model of typical aircraft seat using the finite explicit code LS DYNA. As an example, the FE model of an aircraft seat is validated against the full scale dynamic test conducted as per AC 25.562.

  • CFD Validations with FDA Benchmarks of Medical Devices Flows

    Chien-Jung Huang, Iñaki Çaldichoury, Facundo Del Pin, Rodrigo R. Paz, LSTC

    Computational Fluid Dynamics (CFD) is a powerful tool and has been applied on various problems. In the biomedical application, CFD has been applied not only on the simulations of blood flow and airflow in lungs, but also on the designs and analysis of the medical devices. This study focuses on two benchmark problems proposed by FDA for the standardization of CFD simulation on the safety analysis on the blood-contacting medical devices, which is called CFD Round Robin study. The first case is the flow in a nozzle with a conical change in diameter at one end of the throat, and a sudden change at the other end, whereas the second problem is the system of blood pump housing and impeller. These two problems were simulated with the LS-DYNA® ICFD solvers and the obtained results are compared with results from other numerical and experimental studies.

  • Challenges of Predicting Impacts with Roadside Safety Hardware: Recent Case Studies

    Akram Abu-Odeh, Texas A&M Transportation Institute, The Texas A&M University System College Station, Texas

    As an integral part of engineering safer roads, road side safety devices passively interact with errant vehicles to redirect them safely back to the road or bring them to a safe and controlled stop. These devices take the form of crash cushions, cable barriers, concrete barriers, steel barriers, guardrails, guardrail terminals and others. Placement criteria and warrants are established in the AASHTO Road Side Design Guide (1). However, before those devices are placed on the roadways, they have to be evaluated under objective test conditions. Given that possible combinations of impact speeds, impact angles, vehicle characteristics and roadway characteristics are infinite, it is impossible to design roadside safety hardware for all those combinations. Thus a “Practical Worse Case” philosophy derived from crash data analyses is followed to determine such impact conditions. In the USA, the evaluation methodologies are established in the Manual for Assessing Safety Hardware (MASH) guidelines (2). As with any design process, gone are the days of try and error experimentation due to increased cost of testing and the increased accuracy and efficiency of simulation. Hence, state of the art nonlinear finite element methodology has been gaining tractions in designing and enhancing the safety of roadside devices. LS-DYNA® established itself as the code of choice for simulating vehicular impact scenarios with roadside hardware. This paper will highlight roadside safety hardware (3, 4) that was designed through extensive LS-DYNA simulations and had subsequent crash tests per the latest MASH guidelines. Signals and phenomena from simulations are compared with those from the subsequent tests and presented within this paper.

  • Challenges of Simulative Consideration of Aluminium Hardening Caused by Paint-Bake

    David Koch, André Haufe, Christoph Wilking, Christian Liebold (DYNAmore GmbH), Markus Feucht, Sebastian Roller (Mercedes-Benz AG)

    Local pre-straining in the forming process and thermal loading in the paint bake process have a significant effect on the further development of local material properties. In many cases it is therefore unavoidable to take such effects into account in the further course of the simulation along the part processing chain. This is particularly evident when the hardening of aluminium components during artificial ageing in the cathodic dip painting furnace is to be considered. During the precipitation processes, dislocations form between the metal lattices depending on the pre-straining and the applied temperature load, which ultimately lead to a further increase in strength. In the following it is shown how this strengthening can be estimated for use in subsequent CAE simulation processes and thus made accessible to crashworthiness simulations. The basis for this approach is the JMAK equation that describes the degree of local hardening phenomenologically. Tensile tests are carried out on differently pre-strained and heat-treated samples. Based on the results of the tests the parameters of the JMAK equation are derived. Using *MAT_TAILORED_PROPERTIES in LS-DYNA® allows the consideration of several locally varying state variables. Here the yield stresses are to be defined as a function of i.e. the degree of hardening and the pre-strain applied during the forming process. The corresponding quantities are mapped from the discretization of the forming simulation (i.e. equivalent plastic strains) and the thermal simulation of the paint-bake-oven (i.e. the computed degrees of hardening) onto the spatial discretization used in crashworthiness. Thus, it is possible to represent the dependence of the yield curves on the decisive influencing variables of the production and hence consider locally individual material behaviour.

  • Characterisation and Simulation of Structural Adhesives

    M. Clarke, J.G. Broughton, A.R. Hutchinson - Oxford Brookes University, M. Buckley - Jaguar Land Rover

    The analysis of adhesive bonded joints and structures relies on accurate materials data and mathematical models. In the present study the goal was to develop a method for simulating accurately, using LS-Dyna, the behaviour of aluminium structures bonded with a single part, heat curing epoxy adhesive. This required a structure with known boundary conditions and for which the substrates deformed in a predictable manner. A suitable specimen, formed from two folded aluminium tubes bonded into a T-shape, had been developed by Ford Research Center, Aachen. The MAT 169 material card was selected as a method that showed promise for use in the simulation of bonded joints. A test programme was developed to characterise the adhesive for use with the MAT 169 material card, using tests from the British Standards catalogue. These data were then used to analyse the T-shaped structure under quasi static loading. The results of tests and analysis of the T-shaped structures were used to assess the accuracy of the adhesive characterisation and suitability of the MAT 169 material card. A parametric study was then carried out to determine the robustness of the solutions. Once it had been established that a robust solution had been reached the results from the parametric study were used to develop an optimised set of input data for the adhesive.

  • Characterisation and Simulation of Structural Adhesives

    M. Clarke, J.G. Broughton, A.R. Hutchinson - Oxford Brookes University, M. Buckley - Jaguar Land Rover

    The analysis of adhesive bonded joints and structures relies on accurate materials data and mathematical models. In the present study the goal was to develop a method for simulating accurately, using LS-Dyna, the behaviour of aluminium structures bonded with a single part, heat curing epoxy adhesive. This required a structure with known boundary conditions and for which the substrates deformed in a predictable manner. A suitable specimen, formed from two folded aluminium tubes bonded into a T-shape, had been developed by Ford Research Center, Aachen. The MAT 169 material card was selected as a method that showed promise for use in the simulation of bonded joints. A test programme was developed to characterise the adhesive for use with the MAT 169 material card, using tests from the British Standards catalogue. These data were then used to analyse the T-shaped structure under quasi static loading. The results of tests and analysis of the T-shaped structures were used to assess the accuracy of the adhesive characterisation and suitability of the MAT 169 material card. A parametric study was then carried out to determine the robustness of the solutions. Once it had been established that a robust solution had been reached the results from the parametric study were used to develop an optimised set of input data for the adhesive.

  • Characterisation of an Energy Absorbing Foam for Motorcycle Rider Protection in LS-DYNA

    S. Maier (University of Stuttgart), M. Helbig (DYNAmore), H. Hertneck (SAS-TEC), J. Fehr (University of Stuttgart)

    A study on traffic fatalities [1] shows that the most frequent causes of motorcyclists’ deaths in accidents are multiple skeletal and visceral injuries. Brain and skull injuries are the second leading cause. An injury frequency and pattern data analysis of discharged riders of powered two-wheelers from hospitals [2] show that the most common injuries of non-fatal accidents are injuries of the lower extremities followed by upper extremity and traumatic brain injuries. With this data of fatal and non-fatal accidents it can be said that besides head protection, the protection of a two-wheeler rider’s whole body with lower and upper extremities is of major importance.

  • CHARACTERIZATION AND COMPONENT LEVEL CORRELATION OF ENERGY ABSORBING (EA) POLYURETHANE FOAMS (PU) USING LS-DYNA MATERIAL MODELS

    Babushankar Sambamoorthy - Lear Corporation

    Polyurethane (PU) foams are one of the most widely used countermeasures for head impact protection. For accurate prediction of the head injury parameters, studies were conducted to establish a reliable LS-DYNA[1] material model to characterize PU foams. A 5.0pcf (80.09 g/l) PU foam was characterized using four different material models available in LS-DYNA for simulating foams, namely MAT_LOW_DENSITY_FOAM (MAT57), MAT_CRUSHABLE_FOAM (MAT63), MAT_BILKHU_DUBOIS_FOAM (MAT75) and MAT_FU_CHANG_FOAM (MAT83)[1]. The Finite Element Analysis (FEA) results were compared with the physical test results. The FEA material model resulting from the characterization procedure was validated using a component level, head impact correlation study. A simple side rail section was extruded about the SR1 target point and was impacted with a standard headform at an initial velocity of 15mph. Three different cases were investigated; baseline model with body-in-white (BIW) only, BIW with 18mm foam and BIW with 22mm foam. The Head Injury Criterion (HIC)[2] and acceleration curves from the simulation were compared with the physical tests.

  • CHARACTERIZATION AND COMPONENT LEVEL CORRELATION OF ENERGY ABSORBING (EA) POLYURETHANE FOAMS (PU) USING LS-DYNA MATERIAL MODELS

    Babushankar Sambamoorthy, Tuhin Halder - Lear Corporation, Ford Division

    Polyurethane (PU) foams are one of the most widely used countermeasures for head impact protection. For accurate prediction of the head injury parameters, studies were conducted to establish a reliable LS-DYNA[1] material model to characterize PU foams. A 5.0pcf (80.09 g/l) PU foam was characterized using four different material models available in LS-DYNA for simulating foams, namely MAT_LOW_DENSITY_FOAM (MAT57), MAT_CRUSHABLE_FOAM (MAT63), MAT_BILKHU_DUBOIS_FOAM (MAT75) and MAT_FU_CHANG_FOAM (MAT83)[1]. The Finite Element Analysis (FEA) results were compared with the physical test results. The FEA material model resulting from the characterization procedure was validated using a component level, head impact correlation study. A simple side rail section was extruded about the SR1 target point and was impacted with a standard headform at an initial velocity of 15mph. Three different cases were investigated; baseline model with body-in-white (BIW) only, BIW with 18mm foam and BIW with 22mm foam. The Head Injury Criterion (HIC)[2] and acceleration curves from the simulation were compared with the physical tests.

  • Characterization and Material Card Generation for Thermoplastics

    M. Helbig, A. Erhart, A. Haufe (DYNAmore GmbH)

    Modelling polymer materials for crashworthiness applications is still an ongoing and challenging topic. Besides the constitutive model the spatial discretization plays a significant role in setting up predictive models in impact scenarios where damage and fracture are dominating the part deformation. Therefore, the limits of the chosen spatial discretization shall always be kept in mind. However, the present contribution is focused on recent enhancements of constitutive models for polymeric materials. This topic is as well ongoing for many years and has been tackled almost 2 decades ago by the development of MAT_SAMP-1 (#187) in LS-DYNA®. Many years of continuous improvement lead to a versatile and usable as well as predictive model. Unfortunately for the cost of slow execution speed if the parameter set or the various curve definitions were not chosen wisely. Therefore, a simplified model with the aim to have a more competitive model available when it comes to computing speed was developed. The so called SAMP_LIGHT (#187L) model comes with a complete redesign for speed but also with a number of limitations (due to the speed argument) and still seems to be versatile enough for everyday simulations. The present contribution recalls the features of SAMP-1 and discusses some of the issues that may lead to exaggerated execution time. Then the reduced model is described and a viable approach to convert available SAMP-1 constitutive data towards SAMP_LIGHT is presented. Clearly the limited model may not be as predictive as the fully flavored one – but the drawbacks may not be severe enough to not give it a try.

  • Characterization and Modeling of the Deformation and Failure Behavior of Neat Thermoplastic Homopolymers under Impact Loading Conditions

    P. Stelzer, Z. Major (Johannes Kepler University Linz)

    The increasing use of thermoplastic polymers in structural applications exposed to impact loading conditions drives the need of accurate and reliable FEM simulations. Classical elasto-plastic formulations are based on the von Mises yield criterion and only of limited suitability for modeling polymers. Advanced material models become necessary to capture the complex mechanical deformation and damage behavior. However, the experimental effort is significantly higher to provide material input data. The objective of this study was the modeling of the deformation and damage behavior of thermoplastic homopolymers under monotonic and impact loading conditions with the commercial FEM code LS-Dyna. For this purpose, the material model SAMP-1 and the damage model GISSMO were employed for a Polypropylene and a Polycarbonate grade. A comprehensive experimental characterization, applying full-field strain analysis using a digital image correlation technique and a high speed camera, was performed for the calibration of the models. To derive the input parameters for SAMP-1, uniaxial tensile and simple shear tests were carried out. Experimental compression data was taken from previous studies. Coupon tests were conducted to assess the triaxiality dependent damage and failure behavior. The focus was set on the methodology and modeling techniques to identify a suitable calibration method for the constitutive models. To describe the actual local deformation behavior and to provide a straight-forward methodology, a direct experimental approach was favored to derive the material model input data. Validation was performed on the tensile tests by comparing the numerical and experimental results of the global force-displacement curves and of the local deformations. The elasto-viscoplastic constitutive model SAMP-1 was calibrated for ambient temperature (23±1 °C) and three different strain rates (0.1, 1 and 10 s−1). Until the yield point is reached, the mechanical response is linear elastic. The characteristic pressure dependent quadratic yield surface of SAMP-1 was fitted by the input of tensile, compression and shear data. Moreover, the model incorporates multiaxial hardening behavior. The non-isochoric plastic deformation could be captured by the experimentally determined apparent Poisson’s ratio. The determination of the failure curve, in terms of failure strains as a function of the stress triaxiality factor, is essential for the calibration of ductile damage models like the formulation implemented in SAMP-1 or GISSMO. A combined experimental-numerical approach was used to identify equivalent plastic strain values and corresponding stress triaxiality factors at fracture initiation. A case study on the calibration of a GISSMO model by numerical optimization was conducted for an aluminium alloy. The method of an average triaxiality factor was selected as a rather direct way to extract the failure strains from the experimental tests and was applied for PP and PC.

  • Characterization and Modeling of Spot-Weld Joints in Press Hardening Steels Associated with Softening in Heat Affected Zone

    H. Ghassemi-Armaki, Q. Khan (ArcelorMittal); A. Gill, S. Zilincik (Chrysler)

    Next generation of advanced high strength steels (AHSS) are extensively considered for usage in Body-in-White (BIW) with lower thickness to reduce the vehicle weight and increase fuel efficiency. Resistance Spot Welding (RSW) continues to be a major joining process in BIW, with an average of 4500 spot-welds per vehicle. Spot-weld strength has direct correlation with the thicknesses, and yield strength of the joining sheets in the stack up configuration. Characterization and FEA modeling of spot-welds for accurate failure prediction is of vital importance in vehicle crash safety simulations. This will also lead to an optimized weld layout, optimum weld pitch and cycle time and this has a direct impact on assembly plant layout/investment. Press Hardening Steels “PHS” (e.g. Usibor® 1500) show high strength after hot-stamping and are one of the major category of AHSS. These steels contain a fully martensitic microstructure, which show softening in Heat Affected Zone (HAZ) after spot-welding because of martensite tempering. Accurate prediction of load-displacement and failure load of the spot-weld depends on input data for softened HAZ and connection definition of two joining sheets. In the present study, a modeling method for the spot-weld nugget and HAZ zone was developed and compared to test results. An eight, hexahedral element assembly is used to represent a spot-weld and an element ring of width, 0.35 times of the weld diameter is used to simulate softened HAZ. Since softening in the HAZ is not uniform and shows a gradient as a function of distance from spot-weld center, the HAZ material simulated using Gleeble for different locations was used to characterize and provide material input data for the HAZ shell element. Spot-weld failure was characterized by testing the spot-weld in different loading modes, including, tension-shear, coach-peel, cross-tension and KSII configurations (30, 60 and 90 degrees). *MAT_100_DA in LS-DYNA (version 9.1) was used along *DEFINE_CONNECTION_PROPERTIES for defining material properties for the weld. Results show that the chosen stress-strain curve representative for HAZ shell elements extracted from Gleeble samples can predict the yielding of the load-displacement curve well. Additionally, *MAT_100_DA parameters depend on sheet metal thickness, and exponents for failure equation in this model can be lower than 1 and up to 4 as reported in literature.

  • Characterization and Modeling of Spot-Weld Joints with *MAT_100_DA Parameter Optimization using LS-OPT®, and 3 Sheet Spot-weld Modeling Method Development in LS-DYNA®

    Qaiser Khan, Hassan Ghassemi-Armaki, ArcelorMittal Global R&D, East Chicago, IN, USA;, Amandeep Singh Gill, Scott Zilincik, FCA Chrysler Technical Center, Auburn Hills, Michigan, USA;, Abhishek Gawade, Purdue University, Indianapolis, Formerly Intern at ArcelorMittal

    Spot-weld strength is of crucial importance to the overall vehicle structural integrity and crash safety. With the innovation of Advanced High Strength Steels (AHSS), prediction of spot-weld fracture is of paramount importance in current and future vehicle designs. Spot-weld testing on AHSS intensive coupons was carried out in five different loading conditions, such as Tension-Shear, Coach-Peel, Cross-Tension and KSII configurations (30, 60 and 90 degrees). In spot-weld simulation, a combination of an eight element hexahedral assembly and *MAT_100_DA was used for defining the spot-weld failure criteria. *MAT_100_DA is a 3D stress-based failure surface model which requires the user to define failure stress and exponents for axial, shear and bending stress in order to fail a spot-weld nugget. These parameters are generated from the coupon testing performed in different loading conditions and has to be done for each individual spot-weld stackup in the vehicle.

  • Characterization and Modeling of Engineering Friction and Wear with LS-DYNA

    S. Dong (Ohio State University); A. Sheldon (Honda)

    In mechanical systems, friction and wear usually take place concurrently between two surfaces when they slide or roll relative to each other. Friction exhibits resistance to the relative motion which may vary with different normal loads and relative velocities, while wear is the removal and displacement of the materials from one or both surfaces. The initiation of significant surface wear, in turn, changes the friction, and therefore the overall contact properties. This occurs more often when there are differences in hardness and/or surface roughness between the two surfaces. This paper presents experimental characterization of friction and surface wear between different material combinations. Materials tested, from hard to soft, include coated steel, plastics, ATD rubber, and roof linear fabric. Static and dynamic friction coefficients are measured using a pin-on-disc tribometer under various normal loads and linear velocities. Surface wear, if significant, is characterized using an optical profilometer or a microscope. It was found that the friction coefficient decreases when surface wear first takes place. Part of the displaced material gets stuck in between the two surfaces and acts as a third-body solid lubricant. This type of lubrication mechanism plays more significant role when the material opposite to the worn material is harder. The modeling of friction and wear is then implemented in LS-DYNA. The relationship between friction coefficients, normal stress, and linear velocity is defined in *CONTACT and the wear properties are defined in *CONTACT_ADD_WEAR. Parametric studies are then performed to study the influence of wear and friction properties in crash models.

  • Characterization of a cohesive zone model for adhesives with *MAT_240 and curve mapping method in LS-OPT

    Nicole Betz, Tobias Behling, Martin Holzapfel, Mathieu Vinot, Nathalie Toso

    The importance of adhesives in automotive structures exposed to high crash loads has increased over the years. To improve the structural sizing, it is necessary to predict the behavior of bonded joints under dynamic impact and crash loads. Cohesive zone models have proven to be suitable for numerically representing adhesive behavior in Finite-Element simulations. However, the manual determination of the model parameters requires experience with the material model and a corresponding amount of time to derive the various parameters. The present work aims at developing an optimization scheme with LS- OPT for the effective and automated identification of input parameters for the material card *MAT_240 (*COHESIVE_MIXED_MODE_ELASTOPLASTIC_RATE) [1] which is used to represent the behavior of the adhesive layer. The present work focuses on a curve mapping process with LS-OPT.

  • Characterization of fragments induced by High Velocity Impacts and additional Satellite shielding protective structures evaluation

    T. Legaud, V. Lapoujade (DynaS+)

    A substantial number of debris coming from human production gravitates around the Earth. Their size, nature, orbit and velocity can extremely vary, but all these debris represent an increasing collision risk and a threat for the current and future spatial activity. The spatial researchers are looking for solutions to limit this risk, by better controlling the launched objects number and by improving the protection of their structures.

  • Characterization of the Lode = -1 Meridian on the Al-2024 Failure Surface for *MAT_224 in LS-DYNA ®

    Robert L. Lowe, Jeremy D. Seidt, Amos Gilat (The Ohio State University)

    A key ingredient in the modeling of ductile fracture using *MAT_224 in LS-DYNA is the failure surface, a 3-D graphical representation of the equivalent plastic strain at failure as a function of stress triaxiality and Lode parameter. Ballistic impact experiments used to validate the existing *MAT_224 plasticity and failure models for 2024 aluminum reveal a strong trend of ductile fractures along the Lode = -1 meridian, a region currently underpopulated with experimental data. Exploiting a novel physical interpretation of the Lode = -1 meridian, several new experiments to populate this critical region are proposed and numerically simulated in LS-DYNA, based on adaptations of the standard ASTM quasi-static hemispherical punch test.

  • Characterization of Water Impact Splashdown Event of Space Shuttle Solid Rocket Booster Using LS-DYNA

    Matthew E. Melis - NASA Glenn Research Center, Khanh Bui - Livermore Software Technology Corporation

    The ALE capability in LS DYNA is used to predict splashdown loads on a proposed replace- ment/upgrade of the hydrazine tanks on the thrust vector control system housed within the aft skirt of a Space Shuttle Solid Rocket Booster. Two preliminary studies are preformed in working towards conducting a full comprehensive analysis: An analysis of the proposed tank impacting water without supporting structure, and an analysis of actual space capsule water drop tests conducted at NASA’s Langley Research Center. Results from the preliminary studies provide confidence that useful predictions can be made by applying the ALE methodology to a detailed analysis of a 26-degree section of the skirt with proposed tank attached. Results for all three studies are presented and compared to limited experimental data. The challenges of using the LS DYNA ALE capability for this type of analysis are discussed.

  • Characterizing LS-DYNA ® Implicit performance on SGI ® Systems using SGI MPInside MPI profiling tool

    Dr. Olivier Schreiber, Tony DeVarco, James Custer, Scott Shaw (SGI)

    SGI delivers a unified compute, storage and remote visualization solution to manufacturing customers reducing overall system management requirements and costs. LS-DYNA integrates several solvers into a single code base. The implicit solver is studied for better matching with the multiple computer architectures available from SGI, namely, Multi-node Distributed Memory Processor clusters and Shared Memory Processor servers, both of which are capable of running in Shared Memory Parallelism (SMP), Distributed Memory Parallelism (DMP) and their combination (Hybrid) mode. The MPI analysis tool used is SGI MPInside featuring customary communication profiling and "on the fly" modeling to predict potential performance benefits of the different upgrades available from the latest Intel ® Xeon ® CPU, interconnect and its middleware, MPI library, and the underlying LS-DYNA source code. Profile-guided MPIplace component is used to minimize inter rank transfer times.

  • Characterizing LS-DYNA Performance on SGI Systems using SGI MPInside MPI Profiling Tool

    T. DeVarco, O. Schreiber, A. Altman, S. Shaw (Silicon Graphics)

    SGI delivers a unified compute, storage and remote visualization solution to manufacturing customers reducing overall system management requirements and costs. LS-DYNA integrates several solvers into a single code base. In this paper, the explicit solver is hereby studied for better matching with the multiple computer architectures available from SGI, namely, multi-node Distributed Memory Processor clusters and Shared Memory Processor servers, both of which are capable of running in Shared Memory Parallelism (SMP), Distributed Memory Parallelism (DMP) and their combination (Hybrid) mode. The MPI analysis tool used is SGI MPInside.

  • Chemically Reactive Flows in Airbag Inflator Chambers

    Chemically Reactive Flows in Airbag Inflator Chambers, K. Im, G. Cook Jr., Z. Zhang (LSTC)

    Airbags are part of an important vehicle safety system, and the inflator is an essential part that generates a specific volume of gas to the airbag for a short duration of time. Recently, we have developed numerical models of automotive airbag inflators in conjunction with the LS-DYNA® chemistry solver. In this study, detailed and comprehensive descriptions for theoretical models are developed for a conventional pyrotechnic inflator (PI) and a compressed, heated gas inflator (HGI).

  • Classification-based Optimization and Probabilistic Analysis Using LS-OPT®

    Anirban Basudhar, Imtiaz Gandikota, Livermore Software Technology Corporation, Livermore CA, USA;, Katharina Witowski, DYNAmore GmbH, Germany

    LS-OPT is a standalone Design Optimization and Probabilistic Analysis package with an interface to LS-DYNA® that is capable of solving a variety of reliability assessment and single or multi-disciplinary design problems. It consists of a flexible framework with various methods that are suited to specific types of problems. The solution methods in LS-OPT are broadly categorized as direct or metamodel-based. Metamodel-based methods build approximations of the system responses using only a few samples, before applying core optimization or probabilistic analysis methods on these inexpensive surrogate models. They are particularly attractive due to higher efficiency compared to direct methods, which on the contrary can be prohibitively expensive in some scenarios.

  • Classification-based Optimization and Reliability Assessment using LS-OPT

    A. Basudhar, I. Gandikota, N. Stander (LSTC), A. Svedin, C. Belestam (DYNAmore Nordic), K. Witowski (DYNAmore)

    Simulation-based design often involves the use of metamodeling techniques that provide a cheap surrogate model to replace expensive evaluations. Several types of metamodels are available in LS-OPT, e.g. Radial Basis Function Networks, Feed Forward Neural Networks, Kriging etc.

  • Closing the Gap between Process- and Crash Simulation for Composite Materials

    Ch. Liebold, A. Haufe (DYNAmore GmbH, Germany), H. Finckh (Deutsches Institut für Textil- und Faserforschung Denkendor, Germany), T. Günther(Volume Graphics GmbH, Germany)

    The usage of fiber reinforced plastics (FRP) becomes more and more important in the automotive industry and therefore, the requirements for accurate crash analysis results for such materials increase. As already known from sheet metal forming, process simulations are performed to predict fiber orientations for all kinds of short, long or endless fiber reinforced parts, even though most of the available software tools only use geometrical approximations. On the example of carbon reinforced braided tubes, a mapping tool will be introduced which is able to transfer fiber orientations as well as initial stresses and strains gained from braiding simulations using a high resolution beam mesh onto a coarse crash mesh. The mapping results will be compared with CT–scans taken from such tubes to confirm their accuracy. In the near future, the developed mapping algorithm shall support all kinds of process simulations such as draping or weaving for different element types as well as for different composite materials.

  • Cloud-based Pedestrian Protection App

    Megha Seshadri, Naga Prasad Lagisetty, ESI Group

    Democratize as the meaning says “make (something) accessible to everyone,” is the main objective of today’s industry to have simulations accessible to everyone to achieve significant improvements in development time and consistent outputs. In this paper we would like to present the workflow of a cloud-based Pedestrian Head Impact simulation. The Head Impact simulation will be executed through an embedded workflow, which internally executes several existing and validated process templates on cloud. Once the process execution is completed, the results are uploaded to the cloud and made available for download and visualization on the web.

  • Cloud-Enabled CAE Solutions: Requirements, Basic Concepts and Usability

    A. Heine (CPU 24/7)

    Up-to-date, particularly commercial methods of numerical simulation are able to meet requirements of modern product development and optimisation processes. However, essential prerequisite is not only the application software but also the appropriate High Performance Computing (HPC) resources. Specific applications, like simulation of large models with a very high number of grid points, CFD-driven design optimisation with necessary innumerable variations as well as complex, multidisciplinary problems regarding the simulation of iterative interactive effects are typical examples of getting efficient, high-quality, prompt and precise results only through appropriate High Performance Computing.

  • Cluster Scalability of Implicit and Implicit-Explicit LS-DYNA Simulations Using a Parallel File System

    Mr. Stan Posey, Dr. Bill Loewe - Panasas Inc., Dr. Paul Calleja - University of Cambridge

    The parallel efficiency and simulation turn-around times of CAE software continue to be an important factor behind engineering and scientific decisions to develop models at higher fidelity. Most parallel LS-DYNA simulations use scalable Linux clusters for their demanding HPC requirements, but for certain classes of FEA models, data IO can severely degrade overall scalability and limit CAE effectiveness. As LS-DYNA model sizes grow and the number of processing cores are increased for a single simulation, it becomes critical for each thread on each core to perform IO operations in parallel, rather than rely on the master compute thread to collect each IO process in serial. This paper examines the scalability characteristics of LS-DYNA for implicit and implicit-explicit models on up to 256 processing cores. This joint study conducted by the University of Cambridge and Panasas, used an HPC cluster environment that combines a 28 TFLOP Intel Xeon cluster with a Panasas shared parallel file system and storage. Motivation for the study was to quantify the performance benefits of parallel I/O in LS-DYNA for large-scale FEA simulations on a parallel file system vs. performance of a serial NFS file system. The LS-DYNA models used for the study comprise cases that were relevant in size and physics features to current LSTC customer practice. The favourable results demonstrate that LS-DYNA with parallel I/O will show significant benefit for advanced implicit simulations that can be heavy in I/O relative to numerical operations. These performance benefits were shown to extend to a mix of concurrent LS-DYNA jobs that require concurrent data writes to a shared file system, which for an NFS-based file system would still bottleneck from its single data path for I/O. The paper also reviews CAE workflow benefits since, as an LS-DYNA simulation is completed, the same shared storage provides a platform for direct post-processing and visualization without the need for large file transfers.

  • Cluster Scalability of Implicit and Implicit-Explicit LS-DYNA Simulations Using a Parallel File System

    Mr. Stan Posey, Dr. Bill Loewe - Panasas Inc., Dr. Paul Calleja - University of Cambridge

    The parallel efficiency and simulation turn-around times of CAE software continue to be an important factor behind engineering and scientific decisions to develop models at higher fidelity. Most parallel LS-DYNA simulations use scalable Linux clusters for their demanding HPC requirements, but for certain classes of FEA models, data IO can severely degrade overall scalability and limit CAE effectiveness. As LS-DYNA model sizes grow and the number of processing cores are increased for a single simulation, it becomes critical for each thread on each core to perform IO operations in parallel, rather than rely on the master compute thread to collect each IO process in serial. This paper examines the scalability characteristics of LS-DYNA for implicit and implicit-explicit models on up to 256 processing cores. This joint study conducted by the University of Cambridge and Panasas, used an HPC cluster environment that combines a 28 TFLOP Intel Xeon cluster with a Panasas shared parallel file system and storage. Motivation for the study was to quantify the performance benefits of parallel I/O in LS-DYNA for large-scale FEA simulations on a parallel file system vs. performance of a serial NFS file system. The LS-DYNA models used for the study comprise cases that were relevant in size and physics features to current LSTC customer practice. The favourable results demonstrate that LS-DYNA with parallel I/O will show significant benefit for advanced implicit simulations that can be heavy in I/O relative to numerical operations. These performance benefits were shown to extend to a mix of concurrent LS-DYNA jobs that require concurrent data writes to a shared file system, which for an NFS-based file system would still bottleneck from its single data path for I/O. The paper also reviews CAE workflow benefits since, as an LS-DYNA simulation is completed, the same shared storage provides a platform for direct post-processing and visualization without the need for large file transfers.

  • Cohesive Contact Modeling in Thermoforming Simulations of Metal-CRFP-Metal Sandwich Sheets

    Ö. Cebeci, A. Zeiser (Inpro Innovations­gesellschaft für fortgeschrittene Produk­tionssysteme in der Fahrzeug­industrie), M. von Scheven (University of Stuttgart)

    A novel carbon fiber reinforced metal laminate based on thermoplastic polymer is investigated in the project LEIKA. For the safeguarding of the production of the parts made of this material, coupled thermo-mechanical simulations have to be carried out. Experiments show a large relative sliding, separation and re-sticking behavior between layers during the forming of the heated sheets. Hence, each layer of the laminate needs to be modeled as an individual shell in order to represent the different forming behavior.

  • Cohesive Zone Modeling of Adhesively Bonded Interfaces: The Effect of Adherend Geometry, Element Selection, and Loading Condition

    Devon C. Hartlen, John Montesano, Duane S. Cronin (University of Waterloo)

    Cohesive zone modeling (CZM) is an efficient technique for modeling adhesively bonded interfaces in structure-level simulations. CZM provides a reduction in computational expense compared to using solid elements and provides a more accurate representation of adhesive response, damage, and failure compared to tiebreak contact methods. Despite these benefits, the adoption of CZM is slowed, in part, due to a lack of information and guidelines as to their appropriate use in industrially relevant modeling situations. While many research studies have applied cohesive elements in conjunction with solid elements to model the adherends, most industrial applications such as automotive structures, are commonly modeled with shell elements. Using CZM to join parts meshed with shell elements requires understanding of how forces and moments are transferred from adherend to adhesive, how the bond line should be modeled geometrically, and how adhesive and adherend parts should be connected numerically. While LS-DYNA® contains several cohesive element formulations, including one specifically developed to be compatible with adherends meshed with shells, and a host of connection techniques, there remains a general lack of understanding as to how CZM should be implemented. To guide the use of CZM, a parametric study was undertaken to examine the effect of cohesive element formulation, adherend element selection, bond line geometry, adherend geometry, and the effect of various connection methods on model response. Two exemplar geometries were explored to examine the effect of different loading condition: a double cantilever beam test and a single lap shear test. It was found that changes in element selection and geometry could dramatically affect the stability and accuracy of the responses of a simulation. Based on the results of this study, this paper presents guidelines and recommended practices for applying CZM to adhesive bond lines for a range of possible modeling scenarios.

  • Coil Winding Simulations of Electrical Machines

    Stavroula Stefanatou, Johannes Heydenreich

    The winding of coils on stator teeth is a central process in the manufacture of electrical machines. The quality of the windings and the associated copper fill factor are important factors for the efficiency of electrical motors. While the copper winding process was manual labor some years ago, this process has meanwhile been completely automated and has been taken over by machines and robots. What is still left for manual labor is the setup of the machines for series production. This can be quite time consuming and costly. To support this setup process, fully understand it in all its details and speed it up, BROSE has used LS-DYNA to develop simulation models for the setup of new coil windings.

  • Collaboration for Future HPC-based Simulation Technologies

    A. Walser (Automotive Simulation Center Stuttgart)

    The use of Numerical Simulation and High Performance Computing (HPC) in vehicle development has already been established for years. Nowadays it is the third pillar of vehicle development along with construction and testing. Computer Aided Engineering (CAE) methods in combination with HPC technologies enable engineers to solve complex problems in a quick and cost-effective way long before hardware prototypes are available. Furthermore it opens up the possibility to analyze not just a single concept idea, but many concept variations parallel.

  • Collision of a light weight passenger car against a steel bridge barrier: evaluation of severity indices varying impact conditions

    Prof. Dr. Mariano Pernetti, Dr. Salvatore Scalera - AMET ITALY

    The standards which fixes guidelines for the execution of crash tests to assess the effectiveness of safety barriers in USA and Europe, define an experiment with a low weight passenger car. Such an investigation’s aim is to evaluate risks for vehicle’s occupants in case of impact against the tested device. The congruence of this approach with the philosophy of testing at “the practical worst condition”, has been widely demonstrated in literature. On the other hand, this kind of tests are really expensive and many parameters are hard to control and measure. Due to the aforementioned reasons, numerical analysis of vehicles collisions against safety barriers has become a convenient methodology that supports and integrates the previous one, especially considering the continuous technological hardware/software progress. Besides, the chance of controlling and evaluating each factor which influences full scale crash tests, makes such a methodology an important tool to perform parametric studies to assess the influence of different factors on crashworthiness. This research, carried out with a combine numerical experimental approach, is intended to assess what happens during the collision of a light weight passenger car against a steel bridge barrier with a containment energy level of 724kJ. The work includes three parts. In the first, the fundamental steps of the modelling process are described along with any requirements needed to reproduce four different full scale tests: the frontal and oblique collisions against a concrete wall and the impacts against two types of steel barrier with different containment energy level (127kJ and 724kJ). Data comparison between full-scale and FE simulation concerns time histories of longitudinal and transversal acceleration of CG’s vehicle, ASI, THIV, PHD, pitch and roll angle, velocity variation in the vehicle direction and residual displacements of the barrier. The second part is aimed at clarifying what happens during the impact of the light weight passenger car against a steel bridge barrier. The obtained results clearly show that the acceleration of CG’s vehicle and the value of impact severity indices are affected in a meaningful manner not only by the transversal kinetic energy but also by the impact angle. The last part defines a simple procedure useful to estimate the impact severity indices for a very wide range of impact conditions. The tests performed on the procedure show a very good agreement between estimated and calculated values.

  • Collision of a light weight passenger car against a steel bridge barrier: evaluation of severity indices varying impact conditions

    Prof. Dr. Mariano Pernetti, Dr. Salvatore Scalera - AMET ITALY

    The standards which fixes guidelines for the execution of crash tests to assess the effectiveness of safety barriers in USA and Europe, define an experiment with a low weight passenger car. Such an investigation’s aim is to evaluate risks for vehicle’s occupants in case of impact against the tested device. The congruence of this approach with the philosophy of testing at “the practical worst condition”, has been widely demonstrated in literature. On the other hand, this kind of tests are really expensive and many parameters are hard to control and measure. Due to the aforementioned reasons, numerical analysis of vehicles collisions against safety barriers has become a convenient methodology that supports and integrates the previous one, especially considering the continuous technological hardware/software progress. Besides, the chance of controlling and evaluating each factor which influences full scale crash tests, makes such a methodology an important tool to perform parametric studies to assess the influence of different factors on crashworthiness. This research, carried out with a combine numerical experimental approach, is intended to assess what happens during the collision of a light weight passenger car against a steel bridge barrier with a containment energy level of 724kJ. The work includes three parts. In the first, the fundamental steps of the modelling process are described along with any requirements needed to reproduce four different full scale tests: the frontal and oblique collisions against a concrete wall and the impacts against two types of steel barrier with different containment energy level (127kJ and 724kJ). Data comparison between full-scale and FE simulation concerns time histories of longitudinal and transversal acceleration of CG’s vehicle, ASI, THIV, PHD, pitch and roll angle, velocity variation in the vehicle direction and residual displacements of the barrier. The second part is aimed at clarifying what happens during the impact of the light weight passenger car against a steel bridge barrier. The obtained results clearly show that the acceleration of CG’s vehicle and the value of impact severity indices are affected in a meaningful manner not only by the transversal kinetic energy but also by the impact angle. The last part defines a simple procedure useful to estimate the impact severity indices for a very wide range of impact conditions. The tests performed on the procedure show a very good agreement between estimated and calculated values.

  • Combined Analysis of LS-DYNA Crash-Simulations and Crash-Test Scans

    L. Jansen, D. Borsotto, C. Thole (Sidact)

    In robustness campaigns and optimization processes metamodels are created out of a set of crash-simulations. With the help of such analyses the models used for the simulations can be improved. For example instabilities can be found and explained or the needed material can be minimized under certain safety restrictions. An important question in this context is: How good can these metamodels represent the reality? To answer this question, one can compare the crash-simulations to the real crash-tests, which were recorded by camera systems after the crash. To be able to compare the test-data with the LS-DYNA crash-simulations, we first need to convert the test-data by matching the geometries and transferring the part information from the simulation to the crash-test. Afterwards one can calculate the combination of the simulations, which approximates geometry and deformation behavior of the test-data as close as possible. The distance and difference in behavior between this calculated best fit and the actual crash-test can be used to measure the quality of the simulation model. Once the evaluation of the model is finished, the test-data can also be added to a robustness campaign as an additional simulation and used for further analysis. This allows us to answer questions such as: How does the test fit into the simulation subspace? Which simulation runs are similar to the test for a certain crash event? Which of the dominating crash events found in the simulation can also be found in the test? Thus, the described matching procedure combined with exemplary further analysis methods on the one hand allow for a quick and automated matching between test and simulation and on the other hand a more detailed validation of the simulation model in comparison to the actual test. Due to the conversion of the test-data, the same post-processors can be used for both the simulations and the test-data, resulting in a smoother workflow.

  • Combined Analysis of LS-DYNA® Crash-Simulations and Crash-Test Scans

    Dominik Borsotto, Lennart Jansen, Clemens-August Thole, SIDACT GmbH

    In robustness campaigns and optimization processes metamodels are created out of a set of crash-simulations. With the help of such analyses the models used for the simulations can be improved. For example, instabilities can be found and explained or the needed material can be minimized under certain safety restrictions.

  • Combined Numerical/Experimental Approach for Rivet Strength Assessment

    F. Previtali, M. Anghileri, L.-M. L. Castelletti, A. Milanese - Politecnico di Milano

    The failure mechanism of common aeronautical structures is influenced by the crash behaviour of the riveted joints. Therefore, crashworthiness analyses of aeronautical structures require accurate models of the joints under crash conditions for a correct prediction of the crash behaviour of the structure. In this work, a method to create reliable FE models able to reproduce the behaviour of rivets under crash conditions is introduced. Using explicit FE codes, it is common practice to model rivets and bolts with rigid links or beams, and adopt as a failure criterion the allowable forces envelope obtained for a single rivet after tests [1]. It is shown here that numerical simulations of tests carried out on a single rivet under different loading conditions can be used to characterise the crash behaviour of riveted joints in place of expensive and time-consuming test campaigns. A specific test device was built in order to apply multi-axial loads to a single rivet and perform tests to evaluate the behaviour of a rivet under different loading conditions: from pure shear to pure tension. Numerical simulations of the single rivet test were then carried out using LS-Dyna [1] to reproduce experimental test and to validate the numerical model of the rivet. The rivet was discretised with solid eight-node elements and the piecewise linear plasticity material model was initially used. However, different constitutive laws were then used to characterise areas with either compressive or tensile loads. The whole loading process, from bucking to failure was simulated. Numerical results and test data were compared and it was observed that the numerical models are able to correctly represent the behaviour of a rivet after a tuning of the material parameters and therefore can be used to characterise a riveted joint. At this stage of the research, only quasi-static loading conditions were considered. This assumption allowed reducing the number of parameters that affects the calculations thus simplifying the model set-up. Future works will investigate the effect of strain rate to reproduce crash conditions.

  • Combined Numerical/Experimental Approach for Rivet Strength Assessment

    F. Previtali, M. Anghileri, L.-M. L. Castelletti, A. Milanese - Politecnico di Milano

    The failure mechanism of common aeronautical structures is influenced by the crash behaviour of the riveted joints. Therefore, crashworthiness analyses of aeronautical structures require accurate models of the joints under crash conditions for a correct prediction of the crash behaviour of the structure. In this work, a method to create reliable FE models able to reproduce the behaviour of rivets under crash conditions is introduced. Using explicit FE codes, it is common practice to model rivets and bolts with rigid links or beams, and adopt as a failure criterion the allowable forces envelope obtained for a single rivet after tests [1]. It is shown here that numerical simulations of tests carried out on a single rivet under different loading conditions can be used to characterise the crash behaviour of riveted joints in place of expensive and time-consuming test campaigns. A specific test device was built in order to apply multi-axial loads to a single rivet and perform tests to evaluate the behaviour of a rivet under different loading conditions: from pure shear to pure tension. Numerical simulations of the single rivet test were then carried out using LS-Dyna [1] to reproduce experimental test and to validate the numerical model of the rivet. The rivet was discretised with solid eight-node elements and the piecewise linear plasticity material model was initially used. However, different constitutive laws were then used to characterise areas with either compressive or tensile loads. The whole loading process, from bucking to failure was simulated. Numerical results and test data were compared and it was observed that the numerical models are able to correctly represent the behaviour of a rivet after a tuning of the material parameters and therefore can be used to characterise a riveted joint. At this stage of the research, only quasi-static loading conditions were considered. This assumption allowed reducing the number of parameters that affects the calculations thus simplifying the model set-up. Future works will investigate the effect of strain rate to reproduce crash conditions.

  • Combustion Engine Analyses Using New and Extended Features in LS-DYNA

    A. Jonsson, T. Borrvall, F. Bengzon (DYNAmore Nordic)

    Recently, many enhancements have been made to LS-DYNA’s implicit solver with regard to improved robustness and general functionality. New material models, element formulations, and features for convenient load history management all contribute to making the implicit solver more versatile and user friendly. The new features are of course relevant to general analyses, but here a case-study of a combustion engine analysis is presented to illustrate and promote these new features. Focus will be on thermal and mechanical analyses, to evaluate deformation, stress, plastic strain, gasket pressure etc. The built-in fatigue analysis capabilities of LS-DYNA will also be demonstrated since fatigue life is often the design target in structural analyses of combustion engines.

  • Comparative Analysis of Occupant Responses between LS-DYNA® Arbitrary LaGrange in Euler and (ALE) and Structured–ALE (S-ALE) Methods

    Venkatesh Babu, Kumar Kulkarni, Sanjay Kankanalapalli, Bijan Khatib-Shahidi, Madan Vunnam, U.S. Army, Research Development & Engineering Command, (RDECOM), Tank Automotive Research Development & Engineering Center (TARDEC), Warren MI 48397

    The LS-DYNA ALE/FSI package can accurately model the dynamic response of the structure under blast loading. To simulate blast loading, High explosive, air and sometimes soil are modeled as different ALE materials which flow inside an ALE mesh that covers a spatial domain of our point of interest. If the spatial domain is of complex geometry, the ALE mesh is necessarily unstructured. But often times, the geometry is simply of a box shape so a structured (rectilinear) ALE mesh could be used.

  • Comparative Evaluation of Isogeometric Analysis and Classical FEM with Regard to Contact Analysis

    Z. Naveed, A. Kühhorn, M. Kober (BTU Cottbus-Senftenberg)

    Isogeometric analysis represents a newly developed technique that offers the application of Computer Aided Design (CAD) concept of Non-uniform Rational B-Splines (NURBS) tool to describe the geometry of the computational domain. The simplified transition of CAD models into the computational domain eliminates the problems arising from the geometrical discontinuities induced by the faceted approximation of the mesh. Moreover, numerical analysis directly on NURBS objects significantly reduces the design-to-analysis time compared to traditional FEA approach. In the field of contact mechanics, when finite elements are applied to geometry with curved surfaces, the result is a non-smooth geometrical representation of interface surfaces which may lead to mesh interlocking, high jumps and spurious oscillations in contact forces. To eliminate these issues, various surface smoothening strategies are to be employed in case of FEM. Isogeometric based analysis alleviates these issues without employing any additional smoothening strategy due to inherent higher order continuity of NURBS basis functions and much more accurate results are obtained compared to conventional FE approach. In the current study, LS-DYNA is used to demonstrate the capabilities and advantage of an isogeometric analysis though an example of pendulum under gravitational load. The numerical simulation results are analytically validated and the comparison of NURBS surfaces with faceted surfaces is carried out to investigate the accuracy.

  • Comparative Evaluation of Sound Absorption Performance of Various Types of Core Panels

    S. Tokura (Tokura Simulation Research Corporation)

    Core materials such as honeycomb core panels are used in various industrial products as lightweight and high stiffness materials. As one of the characteristics of the core panel, the sound absorption effect due to the core structure is expected. By using a large core panel for a soundproof wall such as a highway, the possibility of producing a soundproof wall that is lighter than the conventional soundproof wall and has a high sound insulation/absorption effect is being studied. In addition, with the electrification of automobiles, further quietness in the passenger compartment is required, and the use of core panels is being considered for improving the quietness of various transportation machines such as automobiles. Therefore, in this research, we assume several types of core shapes and compare the sound absorption effect of the core panel by modeling the interaction between the core panel and the sound in the air using ALE-based FEM in LS-DYNA®.

  • Comparative Performance of InfiniBand Architecture and Gigabit Ethernet Interconnects on Intel® Itanium® 2 Microarchitecture-based Clusters

    Dr. Lars E. Jonsson, Dr. William R. Magro - Intel Americas, Inc.

    The Intel® Itanium® 2 microarchitecture is based on a 64-bit processor architecture that is ideally suited to compute-intensive applications such as LS-DYNA. In fact, Hewlett Packard* has demonstrated outstanding performance of their Itanium 2-based systems on a range of technical computing applications, including LS-DYNA[1]. Given the success of the platform in achieving performance on a per-processor basis, we turned our attention to the speedups achievable with tightly coupled clusters of Itanium architecture-based servers. In this paper, we study the scalability of an Itanium 2-based server cluster consisting of 4-CPU SMP nodes, connected by gigabit Ethernet* and by a high-performance InfiniBand* Architecture interconnect. We study the relative performance of these interconnects, relating the observed application-level performance to the underlying performance characteristics of the interconnect.

  • Comparative Study of Material Laws Available in LS-DYNA® to Improve the Modeling of Balsa Wood

    Teddy MAILLOT, Vincent LAPOUJADE, Edith GRIPPON (DynaS+), Bernard TOSON, Nathalie BARDON, Jean-Jacques PESQUE (CEA CESTA)

    In order to compute the requirements for transporting packages in various situations using balsa wood as an energy absorber, a constitutive model is needed that takes into account all of the specific characteristics of the wood, such as its anisotropy, compressibility, softening, densification, and strain rate dependence. Completeness alone is not sufficient for the model, because it must perform appropriately in simulations that include many other non-linear situations, such as being subjected to friction, undergoing large deformations, and even failure. To improve their existing modeling within LS-DYNA, CEA CESTA, in partnership with I2M of Talence, carried out a major experimental campaign both on standard characterization tests and on more complex tests representative of the behavior of real structures. All these tests have been modeled using different LS-DYNA material laws to assess their respective limitations and achieve optimal modeling within the framework of material laws currently available in LS-DYNA. In a final validation phase, this optimized material law has been introduced in a finite element model representative of a real package to evaluate its effect relative to the initial law.

  • Comparative Study of Positioning HBM to Cycling Postures Based on Experimental Data

    Maria Oikonomou, Athanasios Lioras, Lambros Rorris, Thomas Nikodelis, Athanasios Mihailidis

    The objective of Crash Analysis is to ensure the safety of a diverse spectrum of road users through the utilization of several finite element (FE) crash simulations. While a considerable number of studies have focused on evaluating the motion and the potential injuries of occupants and pedestrians, the investigation of two-wheel vehicle users remains underrepresented, even though they are considered vulnerable road users and two-wheelers are common personal transportation. Therefore, studying their kinematic behavior in multiple collisions is crucial to ensure safe and convenient travel.

  • COMPARING PLATE-LEVEL BLAST ANALYSIS USING ALE, S-ALE AND CONWEP METHODS

    Ahmet Salih Yilmaz, Barkin Sonmez, Ulas Ozcan Erkan

    The simulation analyses of the explosion were performed using three different methods: LBE (Lagrangian-based Eulerian), PBM (Particle-based Method), and ALE (Arbitrary Lagrangian-Eulerian). The reference point cloud data obtained from the scanning process after the explosion tests conducted on a 12 mm thick M400 steel plate indicated a deformation of approximately 12.5 cm at a Y-directional distance between the measured points. Based on this measurement, the explosion analyses were simulated using the aforementioned three methods. The scenario involved the detonation of 6 kg of TNT beneath the structure.

  • Comparing the Frontal Impact Responses of the VIVA+ Average Female and SAFER Average Male Human Body Models in a Generic Seat

    E. Svenning (DYNAmore Nordic), K. Mroz (Autoliv), T. Johansen (DYNAmore Nordic), N. Lubbe (Autoliv), J. Iraeus (Chalmers University)

    The VIVA+ 50F average female Human Body Model (HBM), currently in early beta status, was compared to the SAFER average male HBM Version 9 with the aim of investigating differences between females and males in terms of kinematics and injury assessment in frontal impacts. The VIVA+ HBM is under development within the research project VIRTUAL and will be released as open source during the summer 2022.

  • Comparison between Experimental and Numerical Results of Electromagnetic Tube Expansion

    J. Shang, S. Hatkevich, L. Wilkerson (American Trim LLC)

    Electromagnetic forming is a complex coupled mechanical-thermal-electromagnetic phenomenon. To accurately simulate this high-velocity and high-strain-rate process, electromagnetism (EM) module of LS-DYNA has been developed. In this paper, the predictive ability of the EM module is assessed through a comparison between experimental and numerical results of electromagnetic tube expansion. The experiment was to apply electromagnetic forming for expansion of Al 6061-T6 tube. Photon Doppler Velocimetry (PDV) was used to measure the velocity during the tube expansion. This process was also modeled using LS-DYNA EM module. Different parameters of Johnson-Cook strength model for Al 6061-T6 were applied to verify the constitutive model parameters for Al 6061-T6. Moreover, 2D axi-symmetric simulations with different mesh densities were performed in this case. A comparison of the expansion velocity between experimental and numerical results is presented and discussed. The good agreement was found between the experimental and numerical results.

  • Comparison Between Experimental and Numerical Results of Electromagnetic Forming Processes

    José Imbert, Michael Worswick - University of Waterloo, Canada, Pierre L’eplattenie - LSTC, Livermore, USA

    Electromagnetic Forming (EMF) is a high speed metal forming process that is being studied with interest in both academia and industry as a way of improving existing sheet metal forming. The main thrust of the published research has been increasing the formability of aluminum alloys. Observing and measuring EMF process is made very difficult by the high speeds involved and the tooling used to obtain the final shapes. As with many other processes, numerical simulations can potentially be used to study the details of EMF; however, one limiting factor is the difficulty in modeling the process, since accurate models of both the structural and electromagnetic phenomena must be solved. Researchers have relied on simplifications that use analytical magnetic force distributions, on separate electromagnetic (EM) and structural codes or on in-house codes that can solve both problems simultaneously. In this paper, the predictive ability of the EM module of LS-DYNA® is assessed through a comparison between experimental and numerical results for samples formed by EMF. V-Channel and conical shaped samples were formed using two different EMF apparatuses. For the V-Channel samples a double rectangular coil was used and for the conical samples a spiral coil was used. Both processes were modeled using LS-DYNA®’s EM module. A comparison of the final experimental and numerical final shape and current profiles is presented. It was found that the models provide good qualitative results and are able to predict the major features of the samples studied. Good quantitative agreement between the predicted and measured current profiles was found. The discrepancies observed are the result of numerical issues and the simplifications used in the creation of the specific models. It was found that the software can accurately predict the trends of the forming processes studied.

  • Comparison of ALE and SPH Simulations of Vertical Drop Tests of a Composite Fuselage Section into Water

    Karen E. Jackson, Yvonne T. Fuchs - NASA Langley Research Center Hampton

    Simulation of multi-terrain impact has been identified as an important research area for improved prediction of rotorcraft crashworthiness within the NASA Subsonic Rotary Wing Aeronautics Program on Rotorcraft Crashworthiness. As part of this effort, two vertical drop tests were conducted of a 5-ft-diameter composite fuselage section into water. For the first test, the fuselage section was impacted in a baseline configuration without energy absorbers. For the second test, the fuselage section was retrofitted with a composite honeycomb energy absorber. Both tests were conducted at a nominal velocity of 25-ft/s. A detailed finite element model was developed to represent each test article and water impact was simulated using both Arbitrary Lagrangian Eulerian (ALE) and Smooth Particle Hydrodynamics (SPH) approaches in LS-DYNA®, a nonlinear, explicit transient dynamic finite element code. Analytical predictions were correlated with experimental data for both test configurations. In addition, studies were performed to evaluate the influence of mesh density on test-analysis correlation.

  • Comparison of Analytical and Numerical Results in Modal Analysis of Multispan Continuous Beams with LS-DYNA

    Abhijit Mahapatra, Avik Chatterjee - Central Mechanical Engineering Research Institute, India

    This paper deals with the study of natural frequencies of vibration of continuous beams supported on hinged end supports with and without overhang. The paper illustrates the analytical formulation of the natural frequencies and corresponding modes of a n-span continuous beam by using a general solution for the Euler-Bernoulli differential equation. Using two different approaches, namely the analytical method and the numerical method some typical continuous beams are analyzed and the conformance of the FEM solver LS-DYNA is tested. The objective is to test the correlation between approximated analytical and numerical methods adopted for this particular study. The computed results are given in tabular form.

  • Comparison of Crash Models for Ductile Plastics

    B. Croop, M. Lobdell, H. Lobo (DatapointLabs)

    There is interest in quantifying the value of different material models being used in LS-DYNA today for the modeling of plastics. In our study, we characterize two ductile, yet different materials, ABS and polypropylene, for rate-dependent tensile properties, and we use the data to develop material parameters for the material models commonly used for plastics: MAT_024 and its variants, MAT_089 and MAT_181. We then perform a falling dart impact test, which produces a complex multi-axial stress state, and we simulate this experiment using LS-DYNA. For each material model, we are able to compare simulation to actual experiment, thereby obtaining a measure of fidelity of the simulation to reality. In this way, we can assess the benefits of using a particular material model for plastics simulation.

  • Comparison of crash tests and simulations for various vehicle restraint systems

    M. Massenzio, S. Ronel - Université de Lyon, C. Goubel - Université de Lyon / Laboratoire INRETS Equipements de la Route (LIER SA), Lyon Saint Exupéry Aéroport, E. Di Pasquale - SIMTECH

    The use of computational mechanics methods is now largely adopted in the field of Road Side Safety. They are certainly interesting in the context a product development. However, the application of these methods in the certification process raises number of issues, addressed, among others, within the EU CEN TC226/WG1/TG1/CM-E, where some of the authors participate. This paper presents some crash test results and their related simulations, and aims to cover a wide panel of devices, different both in the architecture of the devices and in the outcome of the crash test carried out for certification. After a brief presentation of the failure modes observed, we discuss different validation criteria.

  • Comparison of crash tests and simulations for various vehicle restraint systems

    M. Massenzio, S. Ronel - Université de Lyon, C. Goubel - Université de Lyon / Laboratoire INRETS Equipements de la Route (LIER SA), Lyon Saint Exupéry Aéroport, E. Di Pasquale - SIMTECH

    The use of computational mechanics methods is now largely adopted in the field of Road Side Safety. They are certainly interesting in the context a product development. However, the application of these methods in the certification process raises number of issues, addressed, among others, within the EU CEN TC226/WG1/TG1/CM-E, where some of the authors participate. This paper presents some crash test results and their related simulations, and aims to cover a wide panel of devices, different both in the architecture of the devices and in the outcome of the crash test carried out for certification. After a brief presentation of the failure modes observed, we discuss different validation criteria.

  • Comparison of Different Material Models in LS-DYNA (58, 143) for Modelling Solid Birch Wood

    G. Baumann, Graz, F. Feist (University of Technology), S. Hartmann (DYNAmore), U. Müller (University of Natural Resources and Applied Life Sciences), C. Kurzböck (Virtual Vehicle Research Center)

    Sustainability plays an increasingly important role in the automotive industry. In order to reduce the ecological footprint, the suitability of alternative bio-based materials like wood is investigated within the project WoodC.A.R. In order for wood to be used as an engineering material for structural components or even crash relevant structures, it has to fulfill high mechanical demands. The material behavior has to be predictable and describable in a numerical simulation. Therefore, two material models *Mat_58 (*Mat_Laminated_Composite_Fabric) and *Mat_143 (*Mat_Wood) were compared and validated against quasi-static tension and compression tests in all its six anatomical directions but also against three-point bending tests with the wood fibers oriented parallel to the beam’s axis. So called “clear wood” samples, i.e. specimens without any growing features, were tested covering the different load levels: linear elasticity, strain-hardening, strain-softening and rupture. While *Mat_58 is an orthotropic material model, *Mat_143 is transversally isotropic which means there is no possibility to distinguish between the radial and the tangential direction of the material. Therefore, a trade-off for both directions has to be found. On the other hand, the material law *Mat_143 is able to consider influences like temperature, moisture content or even the quality respectively sorting degree of the wood. Both material models show that some simplifications considering the hardening and softening behavior, especially in compression have to be taken into account in multi-element specimens. While wood shows softening at longitudinal compression, there is a pronounced hardening in perpendicular direction. The strengths and weaknesses of both material models are discussed.

  • Comparison of Faceted Vs Ellipsoid Dummies In Frontal Crash Simulations

    Hovenga P.E., Spit H.H., Kant A.R., Happee R. - TNO Automotive Safety Solutions

    An improved Hybrid-III 50th %ile crash test dummy model has been developed in MADYMO. Advanced multibody techniques have been used to obtain fast computation times with the geometry and potential accuracy of CPU intensive finite element models. So-called facet surfaces have been used in combination with flexible bodies and rigid bodies. The MADYMO contact algorithm has been enhanced with options to separately describe the non-linear compliance of two contacting objects such as a dummy and a seat and orthotropic, penetration- dependent friction has been implemented to capture of ‘belt pocketing’ in the dummy flesh. The available set of component and full dummy validations has been extended with load cases representing the latest restraint system designs and test procedures. A systematic validation has been performed using objective rating techniques to compare the enhanced facet model to the standard ellipsoid model. Objective rating showed that the enhanced facet model provides significant benefits in particular for chest deflections.

  • Comparison of FEM and SPH for Modeling a Crushable Foam Aircraft Arrestor Bed

    Matthew Barsotti - Protection Engineering Consultants, LLC

    Passenger aircraft can overrun the available runway area during takeoff and landing, creating accidents involving aircraft damage and loss of life. Crushable foam arrestor bed systems are often placed at runway ends to mitigate such overruns. As the aircraft tires roll through the bed, the material compaction dissipates energy, bringing the aircraft to a controlled stop. A detailed two-year analysis was conducted for the TRB Airport Cooperative Research Program to develop improved arresting systems (Barsotti, et al., 2009). A major thrust of the effort was the development of validated numerical models for crushable arrestor bed materials and deformable aircraft tires. Finite element models for the crushable material manifested several problems due to the unusual mode of deformation experienced, which included significant element skewing, heavy compaction (~90%), and high hourglass energies (~19%). Many meshing and hourglass mitigation strategies were attempted, but they produced only marginal improvement. The Smoothed Particle Hydrodynamics (SPH) method was adopted as a replacement, and detailed performance comparisons of the FEM and SPH versions were made. Error convergence studies using mesh refinement were performed for 1-D, 2-D, and 3-D cases, culminating in the comparison of full tire & arrestor models for each formulation.

  • Comparison of Hybrid III Rigid Body Dummy Models

    Stephen Kang, Paul Xiao - Ford Motor Company

    Hybrid III Dummy Computer Aided Engineering (CAE) models have long been used for aspects of vehicle design, including vehicle structure and restraint systems to meet regulatory safety rating targets and internal company requirements. The quality and run time of these CAE models in simulating physical dummies directly affects the usefulness of CAE tools in vehicle development. The objective of this study is to compare the responses of the Madymo Rigid Body dummy and the LSTC Rigid-FE dummy in four crash test modes of one vehicle. During the study, in order to have a fair and sound comparison, the authors have requested each of the companies (TASS and LSTC) to examine the performance of their respective dummy models in essentially the same vehicle environment model. The authors would like to acknowledge their efforts and comments. In particular, frontal crash test modes using the passenger belted and unbelted 50th percentile male Hybrid III dummy and the passenger belted and unbelted 5th percentile female Hybrid III dummy were studied. In each test mode, the Madymo Rigid Body dummies and the LSTC Rigid- FE dummies (beta release) were used. The CAE model results were compared with test results in both time history measurements (acceleration, velocity, displacement, forces, moments) and occupant kinematics (using high speed video). This is the result of one case study and the authors do not intend to draw any general conclusions as to which dummy model is better in relation to the other.

  • Comparison of Lagrangian, SPH and MM-ALE Approaches for Modeling Large Deformations in Soil

    Cezary Bojanowski - Argonne National Laboratory, Ronald F. Kulak - RFK Engineering Mechanics Consultants

    Ongoing research at the USDOT funded Transportation Research and Analysis Computing Center (TRACC) at Argonne National Laboratory on bridge stability for bridges with piers in scour holes relies greatly on LS- DYNA® capabilities for modeling large deformations in soil and fluid structure interaction. When it comes to soil modeling, material model MAT_005 Soil and Crushable Foam is often used as a first approximation. It is especially useful when little material characterization is performed--which is usually the case for riverbed soil. Although an abundance of reports can be found where MAT_005 was used with the Lagrangian approach, its use in Smoothed Particle Hydrodynamic (SPH) and Multi Material Arbitrary Lagrangian - Eulerian (MM-ALE) approaches is considerably less documented. This paper presents a comparative study of the performance of MAT_005 with Lagrangian, SPH and MM-ALE approaches for predicting large deformation soil response. For the purpose of validation, simulations were performed for the in-situ experiment of a steel loading pad penetrating into silty clay sand. Using LS-OPT® metamodel based sensitivity analysis was conducted to identify the most relevant material and loading parameters. The results show that the three formulations can produce reasonable predictions at large penetrations. Although very suitable for soil penetration problems, MM-ALE requires iterative adjustments of contact parameters to eliminate spurious leakage. The LS-OPT sensitivity analysis on material parameters indicates the yield function parameters have the greatest influence on the results. Further important parameters are the soil density and appropriate modeling of the soil island boundaries. It was also noted that the choice of the type of domain decomposition greatly affects the compute time.

  • Comparison of Laser-Scanned Test Results and Stochastic Simulation Results in Scatter Mode Space

    M. Okamura, H. Oda (JSOL), D. Borsotto (Sidact)

    Recent years, CAE plays more important roles in product development than ever. Good CAE models require validation works with various test data. However, the way of comparison needs to be improved in order to meet the market expectations. Usually a set of test data is given to CAE engineers after all specimen are tested, and test machines are cleaned up. In case CAE engineers find out remarkable differences between simulation results and test results are too great due to mistakes in test laboratories, validation process becomes quite difficult in many cases. In this study, quasi static compression of a crash box is used as an example in order to illustrate the proposed process. A preliminary stochastic simulation and a set of tests is conducted, and the deformation of the crash boxes are transformed into the common modal space. This process makes it possible to assess similarity of deformation modes from multiple simulation results and test results at a glance. This analysis can be conducted at test lab, and fundamental difference between test and simulation can be detected every time specimen are tested. In case an issue is detected, CAE engineers and test engineers can start discussion how to improve the test set up and simulation model in the laboratory.

  • Comparison of LS-DYNA and NISA in Solving Dynamic Pulse Buckling Problems in Laminated Composite Beams

    Haipeng Han, Farid Taheri - Dalhousie University, Canada

    In this paper the dynamic pulse buckling of laminated composite beams was analyzed using LS-DYNA and another widely used commercial FE code, namely NISA (Ver.12), developed by EMRC (Engineering Mechanics Research Corp). Two types of impact loadings that could induce dynamic pulse buckling of composite beams were analyzed. The first one was a force applied to the structure in a very short duration (i.e., an impulse load). The other one was the impact of a moving mass having a certain initial velocity. This problem brings considerable challenges if one is to simulate the phenomenon accurately. The main objective of this technical exercise was to investigate the influence of certain numerical parameters on the integrity of the out coming results. The objective was also to assess the performance of a “conventional, general purpose” type FEM program versus LS-DYNA, which is considered as a leading FEM code for the analysis of highly nonlinear phenomena. This was an interesting exercise in demonstrating why one should use codes like LS-DYNA, as oppose the general purpose FEA codes when considering such highly non-linear phenomena. Both abovementioned loading types were considered in this study. In the analysis using LS-DYNA, the force function was introduced by applying an impulse force at one end of the FRP beam. The moving object was also modeled in LS-DYNA by means of a rigid wall having a mass and an initial velocity. The impact by moving object could not be accommodated by NISA, so only the pseudo-impulse type loading could be considered in NISA. Parametric studies were also conducted to investigate the effect of the slenderness ratio, the curvature and the stacking sequences of the FRP beams, as well as the examination of the influence of the initial imperfection used to promote structural instability.

  • Comparison of LS-DYNA Version 7, 9 and 11 – A View of an Airbag Supplier

    A. Seeger (iSi Automotive Berlin), S. Stahlschmidt (DYNAmore)

    Several LS-DYNA versions are currently available – R7 is still in use in several projects, the currently mostly used version is R9, future projects will be run in R11. This paper will compare these three versions with focus on some airbag issues.

  • Comparison of material models for crash simulation - experimental and simulation work

    S. Mönnich, F. Becker - German Institute for Polymers (DKI), B. Fellner - MAGNA STEYR Fahrzeugtechnik

  • Comparison of MM-ALE and SPH methods for modelling blast wave reflections of flat and shaped surfaces

    Jovan Trajkovski (University of Ljubljana)

    The Multi-Material Arbitrary-Language-Euler (MM-ALE) and Smooth-Particle-Hydrodynamics (SPH) are widely used methods for numerical examination of structural response under blast loading. On the other hand, the methods are quite demanding for use. They have their own advantages and disadvantages depending on the structural geometry and its relative position with regard to the blast wave source location. This paper presents comparison results of detailed numerical examination using both the MM-ALE and SPH method. A series of simulation tests were performed using flat and shaped armor steel plates in LS-DYNA. The comparison results showed that the SPH method offers better results and efficiency compared to the MM-ALE method. This is especially evident in cases involving curved structural geometry. The results of this paper will be of great value in the decision making process when choosing an appropriate method for blast response analyses of structures.

  • Comparison of Particle Methods : SPH and MPS

    Sunao Tokura (Tokura Simulation Research Corporation)

    SPH (Smoothed Particle Hydrodynamics) implemented in LS-DYNA® has been used widely in various industrial fields as a reliable and robust particle method. At present SPH is considered as one of major numerical simulation method for compressible fluid and solid materials. Recently a unique particle method called MPS (Moving Particle Simulation) has been developed and started to use for some industrial application as a CFD (Computational Fluid Dynamics) solver for incompressible flow. As most application for fluid flow in industry are incompressible, MPS may have a potential ability to treat such problems efficiently than SPH. Both methods have common characteristics that particles are used to discretize continuum domain to be solved. However, as the numerical procedures to solve the governing equation are very different, each numerical simulation method has both inherent advantages and disadvantages. This paper demonstrates the comparison of SPH and MPS for some engineering problems and intends to reveal the difference of these two methods. Comparison of numerical simulation techniques should be very useful for further understanding about multiphysics capability of LS-DYNA even for expert LS-DYNA users. Surface tension model, turbulence model, treatment of Newtonian and Non-Newtonian fluid, coupling with structures and other several topics are discussed. In addition an FSI (Fluid Structure Interaction) problem using MPS software and LS-DYNA is demonstrated in the presentation. In this FSI problem a vehicle is washed away by a tsunami and crashes against a rigid wall. Pressure of tsunami on the surface of the vehicle is computed by MPS software and the deformation of the auto body is calculated by LS-DYNA.

  • Comparison of Polyurethane and Epoxy Adhesive High Strain Rate Performance Using Cohesive Zone Model

    Devon Downes, Manouchehr Nejad Ensan, Chun Li

    It is known that the ballistic performance of ceramic composite personnel armour is highly dependent on the thickness of ceramic and backing material. Recent studies have begun focusing on the effect of adhesive bonding between the ceramic and the backing plate, because failure of the adhesive layer can cause separation between the ceramic and backing. This debonding between substrates causes the ceramic to underperform by shattering early due to an imperfect transmission of the stress wave to the backing material. Given that the adhesive plays such an important role in armour, it is important to better understand the underlying physics.

  • Comparison of Single Point Incremental Forming and Conventional Stamping Simulation

    A. Belmont, R. Cruz, S. Fernandez, E. Quiroz and R. Perez-Santiago, Universidad de las Américas Puebla, Puebla, Mexico

    This paper resumes simulation related aspects of one project aimed to compare two different sheet metal manufacturing technologies: Incremental Sheet Forming (ISF) and Conventional Stamping. Simulation of stamping in different stages of product development is an established practice in the industry, and the obtained results utilized to validate the process engineering before engaging in tooling fabrication. On the other hand, ISF simulations are difficult to implement, mainly due to its long computational time stemming from the incremental and localized deformation strategy, which for a simple part demands a tool path length in the order of hundreds or thousands of meters.

  • Comparison of Strategies for Landmine Modeling in LS- DYNA with Sandy Soil Material Model Development

    Matt Barsotti; Eric Sammarco, Ph.D., P.E.; David Stevens, Ph.D., P.E. (Protection Engineering Consultants)

    As part of the United States Marine Corps (USMC) Mitigation of Blast Injuries through Modeling and Simulation project, Protection Engineering Consultants investigated and compared a range of landmine modeling strategies in LS-DYNA. Dividing the constituent materials into solids (soil) and fluids (air and explosive burn products), various numerical formulations were applied to the two groups in different combinations. Single-formulation strategies included a traditional all-ALE approach and a less conventional all-SPH approach. Hybrid formulation strategies included combinations of ALE fluid and explosive materials with FEM, DEM, or SPH soil. The various single- formulation and hybrid-formulation are compared in terms of implementation, required coupling definitions, stability issues, calculation demands, and overall feasibility. The quantitative performance of three front-runner strategies were compared against benchmark test data. Evaluation cases included initial soil bubble formation, scaled-test impulses against flat plates, scaled-test impulses against angled plates, and full-scale impulses against flat plates. The benchmark tests used sandy soils at varying levels of saturation. A generalized sandy soil modeling approach was used to generate parameters for the Pseudo Tensor material model and the Tabulated Compaction equation of state. The average error for predicted impulse was less than 2.5%, which was obtained from the generalized soil model using a priori material parameter settings and without post hoc tuning.

  • Comparison of the Brain Response to Blast Exposure Between a Human Head Model and a Blast Headform Model Using Finite Element Methods

    Rahul Makwana (DEP-Autoline Inc), Sumit Sharma (Eicher Trucks and Buses VE Commercial Vehicles Ltd.), Liying Zhang (Wayne State University)

    Impact induced traumatic brain injury (TBI) has been studied by physical testing using various surrogates, including cadavers, animals, and crash test dummies and by computer modeling including Finite Element (FE) models of human, animal and crash test dummy head. The blast induced TBI research and evaluation of a protective device call for a head model which can mimic wave propagation phenomena through different parts of the head. For proper investigation of head responses and resulting brain injuries due to primary blast exposure, the characteristics of a physical test headform including details of brain/skull anatomy and material properties of the head tissues must be critically designed. The current study was undertaken to numerically evaluate the blast performance of an anatomically realistic headform constructed with existing skull/brain simulant materials in comparison with human head model responses in order to propose a future headform which could be used for testing equipment in blast loading conditions. Quantitative biomechanical response parameters such as pressure, strain and strain rates within the brain were systematically monitored and compared between the blast anatomical headform and the FE human head model. The results revealed that the blast anatomical headform resulted in an average of about 20% over prediction of the biomechanical response parameters in the brain. The results imply that the plyometric based thermoplastic, polycarbonate, polymethylmethacrylate, and polyoxymethylene can be the suitable surrogate skull materials for simulating head responses under blast exposure.

  • Comparison of the RHT Concrete Material Model in LS-DYNA and ANSYS AUTODYN

    C. Heckötter, J. Sievers (GRS)

    The goal of this paper is to compare the implementations of the RHT concrete model developed by Riedel, Hiermaier and Thoma in the commercial hydrocodes ANSYS AUTODYN and LS-DYNA for different stress conditions. The considered stress conditions include hydrostatic compaction related to the Mie-Grüneisen equation of state in conjunction with a p-α model, uniaxial tension, uniaxial compression and tri-axial compression. Parameters of the failure surface and residual strength surface were fitted to data of several tri-axial compression tests. Major differences are observed regarding the behaviour under uniaxial tension. It is pointed out that the current model implementations do not consider fracture energy. Hence, the simulation results depend inherently on mesh size in cases where tensile properties are relevant. Furthermore, comparative validation studies based on impact tests dealing with punching failure of reinforced concrete slabs subjected to hard missile impact have been performed. The sensitivity of the ballistic limit velocity as well as residual missile velocities on model parameters is discussed. The work of GRS was carried out in the framework of the German reactor safety research program sponsored by the German Federal Ministry of Economic Affairs and Energy (BMWi).

  • Comparison of Two Modeling Approaches for Thin-Plate Penetration Simulation

    Norman F. Knight - Veridian-MRJ, USA, Navin Jaunky - Eagle Aeronautics, USA, Robin E. Lawson - FDC/NYMA, USA, Damodar R. Ambur - NASA Langley Research Center, USA

    Modeling and simulation requirements for uncontained engine debris impact on fuselage skins are described and assessed using the tied-nodes-with-failure (TNWF) approach and the element-erosion (EE) approach for penetration simulation. The TNWF approach is based on coincident nodes generated in selected regions of the target plate that are tied together using a constraint relation and the target plate is modeled with shell elements. The EE approach is based on eliminating or removing of an element once some criterion is reached.

  • Complexity based design robustness analysis

    Damien BORDET, Kambiz KAYVANTASH - CADLM

    Application to mechatronic component (vehicle hatchback )

  • Composite Forming Simulation with Introduction to J-Composites/Form Modeler Version 2.0

    M. Nishi, S. Wang, S. Dougherty (JSOL), X. Zhu (LSTC)

    JSOL Corporation has developed J-Composites®, a set of tools, which works in cooperation with LS-DYNA®, to facilitate the complex manufacturing process and process-chain simulation of fiber reinforced composite materials. The J-Composites series consists of “Form Modeler”, a tool to set up a press forming analysis model, and “Fiber Mapper”, a tool to map a resin flow simulation result on to a structural mesh. Additionally, “Compression Molding”, a tool for compression molding simulation is in development. This paper introduces some new capabilities of J-Composites/Form Modeler version 2.0 and demonstrates composite forming simulations.

  • Composites in High Voltage Applications

    C. Weinberger, M. Rollant (4a engineering)

    In the last years the demands of the automotive industry have led to a strong interest in a more detailed virtual description of the material behavior of thermoplastics. More and more complex material models, including damage and failure, have to be characterized, while keeping the importance of gaining material data quickly in mind. Currently material and failure modeling in crash simulations typically deal with simple von Mises visco-plasticity (*MAT_024) and equivalent strain failure criteria, which cannot describe the complex material behavior of plastics. Past developments have focused on the yield behavior under different load situations (tension, shear, compression), which are implemented in more complex material models like *MAT_SAMP-1 for thermoplastics as well as *MAT_215 for fiber reinforced thermoplastics.

  • Comprehensive Correlation of Seat Track Assembly – From Forming to Assembly Test

    S. Sinne, H. Klose, V. J. Dura Brisa, P. Partheymüller (Brose Fahrzeugteile)

    The dimensioning of seat structure including its adjusting components is always a challenge between comfort, lightweight and strength. The main interface between seat structure and vehicle is the s eat track assembly . It enables the length adjustment and transfers a significant amount of the crash load. The increased demands to lightweight , reduction of development time and cost efficiency require a continuous improvement of simulation models regarding accuracy in p redictability.

  • Comprehensive Digital Twin of a Beverage Can Body Forming Process and Performance Evaluation

    Sebastijan Jurendic, Maximilian Weiser

    Novelis is a world leader in aluminium flat rolled products and a major supplier to the beverage can-making industry. As such, Novelis is deeply involved in supporting the can-making industry to help shaping a more sustainable future together. Reducing the amount of metal used for each beverage can is a major driver for improving sustainability of the beverage can packaging, thus Novelis is actively investigating and developing state of the art modelling tools and approaches to support further optimization of the beverage can.

  • Compression Molding Analysis of Long Fiber Reinforced Plastics using Coupled Method of Beam and 3D Adaptive EFG in LS-DYNA

    S. Hayashi (JSOL); H. Chen, W. Hu (LSTC)

    Composite materials like fiber reinforced plastics (FRP) are becoming more widely used in the automotive industry and have been found very effective in reducing vehicle weight. Recently, long carbon fiber reinforced thermoplastics are increasingly being used for lightweight structural parts with high stiffness, strength and energy absorption performance. Compression molding is considered one of the most efficient manufacturing processes to mass produce FRP parts for automotive applications. Compression molding can form long fiber reinforced thermoplastics into complex shapes with relatively low manufacturing cost and short process time. However, currently there are a very limited number of high-accuracy simulation technologies available that can predict long fiber orientation, filling timing and other behavior required for compression molding. In the first part of this paper, a new simulation technology for compression molding of long fiber reinforced plastics implemented in LS-DYNA is introduced. The main features of this new technology are fibers modelled by beam elements and matrix modelled by tetrahedron solid elements with r-adaptive remeshing function based on an Element-Free-Galerkin (EFG) formulation. In the second part of this paper, an investigation of how to define macroscopic viscosity during compression molding of long fiber reinforced thermoplastics is presented. In the final part of this paper, compression molding simulation for stampable sheet made of long fiber reinforced thermoplastics is presented using a complex shaped punch with one cross-rib geometry. The simulation results show good agreement to experiment. In conclusion, this new simulation technology has great potential to simulate compression molding of long fiber reinforced plastics with high accuracy.

  • Compression of LS-DYNATM1 Simulation Results using FEMZIP©

    Clemens-August Thole - Fraunhofer Institute for Algorithms and Scientific Computing

    The standard usage of simulation as part of the automotive design process has increased the demand for archiving simulation results. Intensive collaboration during the development process requires the exchange of simulation results. Compression of simulation results reduces the size of archives and the time for data transfers. Like compression of video streams and pictures, the effective compression of simulation results requires specific tools which exploit the specific data structures of LS-DYNA3D simulation results and allow for a reduced precision of the results. FEMZIP is especially designed for the compression of crash simulation results and achieves a reduction by factor of 7 for reasonable precision requirements.

  • Computational Approach to Detect Instability and Incipient Motion of Large Riprap Rocks

    Cezary Bojanowski, Steven Lottes, Transportation Research and Analysis Computing Center Nuclear Engineering Division, Argonne National Laboratory

    Bridge scour is the process of removal of sediment from around bridge abutments or piers. In the most severe cases, scour leads to failure of bridges. One of the ways to stop or prevent the scour is to reinforce the riverbed by placing large rocks on the portion of the riverbed vulnerable to scour at bridge foundation structures (method called riprap installation). The sizing of riprap in scour countermeasure design is based mostly on limited field observations and scaled laboratory tests under ideal controlled conditions. The actual size of riprap required for many field applications is too large for testing in the laboratory. As a consequence, there is significant uncertainty in the formulas for sizing riprap.

  • Computational Biomechanics: a challenge at the engineering /life sciences interface5th

    John Middleton, Georges Limbert - Cardiff Medicentre

  • Computational Fluid Dynamic of NACA0012 with LS-DYNA ® (ALE & ICFD) and Wind Tunnel Tests

    B. Perin, O. Verdrel, P. Bordenave (DGA Aeronautical Systems), E. Grippon, V. Lapoujade (DynaS+), H. Belloc (Université de Toulouse), I. Caldichoury (LSTC)

    DGA Aeronautical Systems, the technical centre of the French ministry of Defense dedicated to aircraft performance testing and evaluation, combines tests and simulations to validate, among others, parachute systems for the Airdrop Department. The latter also developed modeling and simulation capabilities as a support for evaluation. In parallel, under the authority of the French Ministry of Defense, the Department of Aerodynamics, Energetics and Propulsion (DAEP) of Institut Supérieur de l’Aéronautique et de l’Espace (ISAE), a public institution of higher education and research, conducts research and training support for the Institute. As such, it has developed over the last years the research topic "Aerodynamics of Free Flight Devices" focused particularly on paragliding. The DAEP has expertise and resources in the field of wind tunnel tests and flight aerodynamics of paragliders. DynaS+, a LS-DYNA French distributor and associated services, got a research and innovative subvention from French Government, RAPID financing, to improve the parachute simulation with LS-DYNA. All these entities have shared their skills to better understand and to enhance the knowledge of the fluid representation in the Fluid-Structure Interaction (FSI) simulation of parachute models. They have worked to compare different fluid representations from experimental wind tunnel testing to numerical simulations (ALE and ICFD solvers) around a rigid rectangular wing with NACA0012 airfoil. This study is a complementary work from the publication perspective and concerning the simulation of a flexible ram-air. This paper shows the limitations of the ALE solver to get the aerodynamic coefficients for a wing and the hopes raised by the ICFD solver.

  • Computational Material Models for TSCP Plastics Comparison of the Deformation Behavior with MAT 24 and MAT SAMP-1 with DIEM

    M. Dobes, J. Navratil (Robert Bosch)

    The subject of this article is comparison of the deformation and stress response for two computational material models suitable for POM material. Both material models use erosion of finite elements, but in the first case *MAT_24 is used together with MAT_ADD_EROSION and with parameters combination and in the second case *MAT_SAMP-1 is used together with DIEM (Damage Initiation and Evolution Model). The new computation material model SAMP-1 was built based on the original experimental data used for *MAT_24 and additional tests (3-point bending test, puncture test, etc.). The strain rate effect is considered based on the experiments in defined range and other strain rate values were calculated based on the analogue with Johnson-Cook constitutive material model. The attention is focused on tensile/pressure definition of computational material model in plasticity. This is very important effect for good prediction of the cracks with using damage material model DIEM. The next characteristic is an accumulation of the damage which leads to rupture and finite elements deletion. This property is depending on the stress triaxiality. The results of deformation and stress response are very different for both approaches and SAMP-1 gives closer results to the experimental reality. The two types of the practical tasks are used for comparison of the stress and deformation behavior of these two computational material models. The first comparison checks deformation and stress response and second case tests difference between damage models. This work directly connects to previous articles for FSM (Fuel Supply Modules) introduced in preceding LS-DYNA conferences. We find some non-physical behavior of the *MAT_SAMP-1 for specific configuration. So, this article is appeal for LS-DYNA users and developers to propose of solving of this non-physical behavior *MAT_SAMP-1 in specific situation, like as contact, compression loading area.

  • Computational Micro-Mechanical Model of Composite & Flexible Woven Fabric with Fiber Reorientation

    Ala Tabiei, Ivelin Ivanov - University of Cincinnat

  • COMPUTATIONAL MICRO-MECHANICAL MODEL OF FLEXIBLE WOVEN FABRIC FOR FINITE ELEMENT IMPACT SIMULATION

    Ala Tabiei, Ivelin Ivanov - University of Cincinnati

    This work presents a computational material model of flexible woven fabric for finite element impact analysis and simulation. The model is implemented in the nonlinear dynamic explicit finite element code LSDYNA. The material model derivation utilizes the micro-mechanical approach and the homogenization technique usually used in composite material models. The model accounts for reorientation of the yarns and the fabric architecture. The behavior of the flexible fabric material is achieved by discounting the shear moduli of the material in free state, which allows the simulation of the trellis mechanism before packing the yarns. The material model is implemented into the LSDYNA code as a user defined material subroutine. The developed model and its implementation is validated using an experimental ballistic test on Kevlar woven fabric. The presented validation shows good agreement between the simulation utilizing the present material model and the experiment.

  • Computational Modeling of Adiabatic Heating in Triaxially Braided Polymer Matrix Composites Subjected to Impact Loading via a Subcell Based Approach

    Christopher Sorini, Aditi Chattopadhyay, Arizona State University, Tempe, AZ, USA;, Robert K. Goldberg, NASA Glenn Research Center, Cleveland, OH, USA

    The high rate deformation of polymer matrix composites is often accompanied by significant local adiabatic heating; in the case of ballistic impact loading, heat is generated locally within the polymer matrix due to the conversion of plastic work to heat, but the rapid nature of the event does not allow sufficient time for heat transfer to occur. In this work, a user-defined material subroutine implemented into LS-DYNA® to facilitate the analysis of triaxially braided polymer matrix composites subjected to impact loading, including the effects of heat generation due to high rate inelastic deformation of the polymer matrix, is discussed. To approximate the triaxially braided architecture in finite element models in a computationally efficient manner, a subcell-based modeling approach is utilized whereby the mesoscale repeating unit cell of the triaxial braid is discretized in-plane into an assemblage of subcells. Each mesoscale subcell is approximated as a unique composite laminate with stacking sequence determined from the braid architecture and unidirectional layer thicknesses and fiber volume fractions determined from optical micrographs. Each laminate is modeled in LS-DYNA as a layered thick shell element, where integration point strain increments are taken as volume averaged strain increments applied to a doubly-periodic repeating unit cell with one fiber and three matrix microscale subcells. The generalized method of cells micromechanics theory is utilized to localize the globally applied strains to the constituent level to determine the local strains and stresses as well as the global response of the doubly-periodic repeating unit cell via homogenization. An existing unified pressure dependent viscoplastic constitutive model that was previously extended by the authors to nonisothermal conditions is utilized to model the rate, temperature, and pressure dependent polymer matrix. In the polymer constitutive model, the inelastic strain rate tensor components have been modified to explicitly depend on temperature; strain rate and temperature dependent shifts in matrix elastic properties are determined by shifting dynamic mechanical analysis data with the integration point effective strain rate. Since the subroutine is micromechanical in nature, constitutive models are only applied at the lowest (micro) length scale. Local temperature rises in the polymer matrix due to inelastic deformation are computed at the microscale via the heat energy equation, assuming adiabatic conditions. Simulations of quasi-static straight-sided coupon tests and flat panel impact tests on a representative [0°/60°/–60°] triaxially braided composite material system are conducted to validate the subcell methodology and study the effects of adiabatic heating on the simulated impact response. Time histories of simulated and experimentally measured out-of-plane displacement profiles during the impact event are compared; good agreement is found between experiments and simulations. Simulation results indicate significant internal temperature rises due to the conversion of plastic work to heat in an impact event.

  • Computational Modeling of Geosynthetic Reinforced Soil (GRS) Composites Under Axial Loading

    Marta Sitek, Cezary Bojanowski (Argonne National Laboratory)

    Modeling the behavior of a granular medium, such as soil, as a finite element continuum is a challenging task. A significant number of constitutive models for soils are implemented in commercial software, but their application is limited to specific cases. The main goal of the work presented in this paper was to select a soil model implemented in LS-DYNA ® that performs best in simulating a laboratory compression test of geosynthetic reinforced soil (GRS). The full-scale geosynthetic reinforced soil composite tests were performed at FHWA’s Turner-Fairbank Highway Research Center. An example of a free-standing mini-pier test in a three-dimensional stress-strain state is considered. The specimens vary with geosynthetic reinforcement strength and spacing. The models are built in stages, as soil is placed layer by layer, with geotextile inserts, and compacted. The specimens are then axially loaded until collapse. The history of vertical displacements of the top surface, horizontal displacements on the free surfaces and the ultimate load are recorded and compared with the experimental results. A preliminary study was performed to find the most appropriate soil material model available in LS-DYNA, which would represent well the behavior of granular soil in interaction with a geotextile. Computational results closest to experimental ones were obtained with the use of the *MAT_HYSTERETIC_SOIL (079) model in combination with the *MAT_FABRIC (034) material model to represent the behavior of the geotextile. Additionally, the model *MAT_ADD_EROSION was used to simulate the failure of the geosynthetic material under loading. The simulations show a good correspondence with the experiments. Failure modes of the computational models are similar to the ones obtained in the laboratory. Even though local damage of the soil was not captured, the axial strain and the failure load are represented well.

  • Computational Modeling of the TPU Shock Absorber using LS-DYNA

    Ahmet Mete SABAH, Buğra BALABAN

    In this study, various analysis and test activities are presented, which were carried out for the development of shock-mitigating floor mats. These impact-absorbing floor mats are produced from hyperelastic materials and are designed to absorb high-amplitude, short-duration shock loads in defense or civil applications. Throughout the study, the *MAT027 model is examined for its suitability in modeling hyperelastic materials in both static and dynamic analyses, conducted using the non-linear finite element code LS-DYNA®. The *MAT027 model accurately describes the behavior of hyperelastic materials and is often preferred for this type of material. To correctly apply this model, specific parameters pertaining to the hyperelastic material must be determined. This study primarily focuses on the determination of these material parameters through tests conducted on samples made of Thermoplastic Polyurethane (TPU) material. In the initial phase of the study, a literature review concerning TPU material was conducted, and material parameters were obtained using the test data presented in this study. The material parameters were then optimized using LS-Opt® to achieve the best material behavior. Following the determination of material parameters, dynamic simulations were performed using LS-DYNA®, and the simulation results were subsequently compared with experimental data. With the material parameters in hand, the second phase of the study involved the design of cellular structures with various geometric shapes. The force-displacement graphs of these newly designed shapes were analyzed through dynamic analyses.

  • Computational simulations of aluminum foam projectile behavior

    M. Borovinsek, M. Vesenjak, Z. Ren - University of Maribor, S. Itoh - Kumamoto University

    The results of experimental tests and computer simulations of open-cell aluminum foam behavior under high deformation rates are presented. Experimental Taylor impact tests showed, that the open-cell foam projectile deforms already during its acceleration in the Taylor barrel. This behavior was investigated further by use of computer simulations with the LS-DYNA. The simulations confirmed very high sensitivity of open-cell foam projectile to the acceleration.

  • Computer Generation of Sphere Packing for Discrete Element Analysis in LS-DYNA

    Z. Han, H. Teng, J. Wang (LSTC)

    The constructive algorithms for sphere packing are based on the pure geometrical computation. They are very efficient and robust for building very large sphere packings with millions of spheres in a few minutes. A constructive algorithm has been developed in LS-DYNA for arbitrary 3D geometries with the size distribution control. The brief introduction of the algorithm is presented in this paper. The procedures and some generated sphere packings are also presented to demonstrate its application for the discrete element analysis by using LS- DYNA.

  • Computer Simulated and Experimental Verification of Tooling for Progressive Deep Drawing.

    Peter Kostka, Peter Cekan - Slovak University of Technology in Bratislava

    The ability to predict different process conditions in deep drawing is essential for die face designers, tooling, stamping and manufacturing engineers. These predictions in turn affect the speed, accuracy and cost of the final produced product. This paper briefly discusses the possibilities of controlling the blankholder pressure distribution and shows some computer simulations done in DYNAFORM, with the results being experimentally verified with tooling designed by the authors.

  • Computer Simulation of Sheet Metal Forming and Drawbead Effects Using eta/DYNAFORM

    Yinghong Peng, Zhaoyuan Wang, Xiongfei Yin, Xueyu Ruan - Shanghai Research Institute of Tool & Die

    The kernel technology of a computer simulation system and the general procedure of dynamic simulation in sheet metal forming are presented. As an example, processing parameters of the experimental die of a car inner door panel were optimized with eta/DYNAFORM software. The appropriate round corner of punch, BHF and the correct layout of the drawbead were obtained.

  • Computing on GPUs

    Prof. Dr. Uli Göhner - DYNAmore GmbH

    The increasing power of GPUs has led to the intent to transfer computing load from CPUs to GPUs. A first example has been the porting of computing intensive algorithms like e.g. ray-tracing algorithms from CPU to GPU. Through the Compute Unified Device Architecture (CUDA [4]) GPUs can also be used to increase computing speed for High Performance Computing applications. In this paper different parallelization strategies for different processor architectures are presented. They are compared and first experiences using GPUs for a collection of numerical applications are given.

  • Computing on GPUs

    Prof. Dr. Uli Göhner - DYNAmore GmbH

    The increasing power of GPUs has led to the intent to transfer computing load from CPUs to GPUs. A first example has been the porting of computing intensive algorithms like e.g. ray-tracing algorithms from CPU to GPU. Through the Compute Unified Device Architecture (CUDA [4]) GPUs can also be used to increase computing speed for High Performance Computing applications. In this paper different parallelization strategies for different processor architectures are presented. They are compared and first experiences using GPUs for a collection of numerical applications are given.

  • Concept Design of an A-Pillar Mounted Airbag for Pedestrian Head Protection

    Jianfeng Yao, Jikuang Yang - Chalmers University of Technology

    Accident investigations have shown that in pedestrian-versus-vehicle accidents, windshield edges, A-pillars, cowls are the main sources for severe head injuries due to their high stiffness. To mitigate head injury severities, it is necessary to improve the safety performance of these structures. An A-pillar mounted airbag system (AMAS) was devised with the aim to prevent head from directly impacting against stiff structures such as A-pillars, windshield frames and edges. The airbags of the AMAS are installed inside A-Pillars. When a car strikes with a pedestrian, the airbag will break the A-Pillar cover and deploy along the whole APillar to cover the stiff structures. In this study, the safety performance that can be provided by this system was evaluated by mathematical simulations. A finite element (FE) Ford Taurus car model and an EEVC headform model were used to simulate the pedestrian headform tests as proposed by EEVC. FE airbag models were developed and the influence of airbag parameters, including airbag type, inflow mass rate, vent size and deploy timing, were investigated by mathematical simulations. The safety performance of the AMAS was also evaluated by an FE human head model. The results show that this system can greatly reduce the head injury severity in case a pedestrian head impacts with A-pillar areas.

  • Concepts toTake Elastic Tool Deformations in Sheet Metal Forming into Account

    A. Haufe, D. Lorenz - DYNAmore GmbH, Germany, K. Roll, P. Bogon - Daimler AG, Germany

    In recent years the development of more and more niche products, i.e. cars with different external appearance, has become a remarkable trend in the automotive industry. This trend, however, generates higher costs for individual tooling geometries that are traditionally made as stiff as possible. A second trend is the increasing use of high and ultrahigh strength steel grades for bodies in white. Here too the design philosophy for the tools in sheet metal forming is based on a rather rigid and stiff tool approach. It is clear though, that a tremendous amount of money could be saved by designing the tools such, that their elastic deformation during the forming process is taken into account. This would lead to lighter and hence more inexpensive tools. The traditional approach to design the tool geometry by finite element simulations with rigid tools. Clearly, if elastic deformations are to be accounted for in such models, the assumption of a rigid tooling geometry needs to be abandoned. Here the straight forward approach would be to discretize the tool by a sufficiently accurate full 3D finite element model. Additionally the machine stiffness may be added to the model for completeness. Obviously this will lead to prohibitively increased computing time especially for large parts. A simple yet effective way to take the elastic deformations nonetheless into account is to condensate the discretized machine and tool geometry once and reuse it in subsequent simulations runs. The paper will discuss recent features in LS-DYNA® that allow the static condensation of elastic tool and machine geometries. Furthermore the application of the “deformable rigid bodies”- approach is shortly discussed.

  • Conjugate Heat Transfer in LS-DYNA®: An Update of the ICFD-Structure Coupling Capabilities for Hot Stamping

    Iñaki Çaldichoury Rodrigo Paz, Facundo Del Pin, Chienjung Huang (Livermore Software Technology, an Ansys company)

    Hot stamping is an essential process in the long and complex assembly chain that will lead to the manufacturing of a complete vehicle. The three main steps consist in a metal sheet being heated, formed and rapidly cooled, yielding parts with high strength and light weight. The main focus of research in that area resides in reducing cycle times, i.e. the time it takes for the tools to cool down, while simultaneously maintaining a high integrity of the formed workpieces. To that effect, the design of cooling systems has drastically increased in complexity and new guiding models are needed for the engineer to be able to identify and then correct potential ‘dead flow zones’, ‘hot spots’ and other problematic areas. Simulation is increasingly viewed as the most general and versatile tool to tackle those challenges. The physics require a coupled thermal, fluid and often mechanical simulation for which a Multiphysics code is needed. Within LS-DYNA, the ICFD solver offers such capabilities and efforts have been continuous over the years to improve existing capabilities and add new ones in conjunction with user feedback [1] [2]. This paper will offer an overview of the existing capabilities, reveal some best practice approaches as well as introduce the latest developments, with a special focus on the fluid-structure interface and how turbulent effects may affect the heat transfer.

  • Consideration of Manufacturing Effects to Improve Crash Simulation Accuracy

    Curd-Sigmund Böttcher, Steffen Frik - Adam Opel AG

    The confidence level of crash simulations is mainly determined by a well-defined finite element representation of the vehicle structure, correct modelling of the kinematics, and the material properties being applied. In the past, materials were described by quasistatic – or, if available – dynamic stress-strain characteristics. Besides this, each sheet metal part was assumed to have a uniform gage and material characteristics. However, it is a well-known effect that the physical properties of steel can alter significantly during the manufacturing process. This comprises an increase of material stiffness due to plastic deformation as well as gage changes. The amount of these changes is of very local nature and cannot be covered by simply scaling material properties and gages. In the past, crash software tools didn’t support the introduction of these local effects, so that they couldn’t be taken into account. In the meanwhile LS-DYNA has the capability to import information provided by stamping tools such as PAMSTAMP or AutoForm. Thereby a very important part of the material properties can be introduced into the crash simulation models, leading to a significantly increased correlation to test results. The impact of this effect on crash performance was analysed for a recent vehicle project and will be discussed in detail.

  • Consideration of Orientation Properties of Short Fiber Reinforced Polymers within Early Design Steps

    G. Gruber, A. Haimerl, S. Wartzack (Chair of Engineering Design KTmfk. University of Erlangen-Nuremberg FAU)

    Abstract Within the modern automotive industry there is an increasing application of parts made of short fiber reinforced polymers (SFRP). The reasons are their beneficial mechanical properties and their series production capability. However, the prediction of their crash behavior by simulation is very complicated, since a precise simulation requires considering the fiber orientation distribution. That’s why, in early design steps often only imprecise, isotropic simulation approaches are deployed in order to save calculation time and license costs for additional software tools. The aim of the present paper is to introduce a simplified simulation approach allowing an anisotropic simulation taking into account the orientation data obtained by an injection molding simulation. To ena ble its application in ®early design steps only standard functions already implemented in LS-DYNA are deployed. The complex material behavior of short fiber reinforced polymers is represented by overlapping two standard material models of LS-DYNA in one single shell definition. The input parameters of the resulting phenomenological material description are obtained by using optimization methods. The methodology being used to convert the orientation data in order to set up an executable input deck is supported by two self-developed software tools. The first software tool extracts the orientation angles from the process simulation by assigning fiber orientation tensors to corresponding shell elements of the mesh of the crash simulation. For each shell element the orientation data are averaged and projected on the shell. By doing so, the complex orientation state is reduced to just three values per shell element – one fiber orientation angle and two fiber orientation probability values. Based on these data, the second software tool creates the executable input deck. The legitimacy of the presented approach is proved by an experimental validation: SFRP-plates are analyzed within a drop weight test. Despite the mentioned simplification (reduction of the complexity of the orientation state) the numerical results show a strong correlation with the experimental data.

  • Considerations for LS-DYNA Efficiency in SGI IRIX and Linux Environments with a NUMA System Architecture

    Stan Posey, Nick Meng - SGI

    Manufacturing industry and research organizations continue to increase their investments in structural analysis and impact simulations such that the growing number of LS-DYNA users continue to demand more from computer system environments. These demands typically include rapid single job turnaround and multi-job throughput capability in a multi-user high-performance computing (HPC) environment. What is more, many LS-DYNA simulation environments coexist with other mechanical computer aided engineering (MCAE) software for structural analysis and computational fluid dynamics that all compete for system resources such as CPU cycles, system bandwidth, memory, disk storage and I/O. This paper examines the computational efficiency of structural analyses and simulations for relevant applications in LS-DYNA. Parameters such as model size, element types, and simulation conditions can produce a wide range of computational behavior such that consideration should be given to how system resources are allocated and configured. The computational characteristics of the SGI® Origin® 3000 servers, based on IRIX® and MIPS®, and the SGI® Altix™ 3000 servers, based on Linux® and Itanium® 2 from Intel®, are examined for both turnaround and throughput requirements that include industrial-size examples. In addition, simple guidelines on proper system configuration and innovative use of available SGI system resource management tools are provided that are designed to maximize LS-DYNA productivity. Introduction Mechanical design and manufacturing organizations increasingly rely on highperformance computing (HPC) technology and mechanical computer-aided engineering (MCAE) applications to drive innovation in product development.

  • Considerations for LS-DYNA Workflow Efficiencies in an HPC Linux Environment

    Stanley Posey - HPC Applications Development

    Manufacturing industry and research organizations continue to increase their investments in structural analysis and impact simulations such that the growing number of LS-DYNA users continues to demand more from computer system environments. These LS-DYNA workflow demands typically include rapid single job turnaround and multi- job throughput capability for users with diverse application requirements in a high-performance computing (HPC) environment. Additional complexity arises from the need for many LS-DYNA HPC environments to coexist with other computer aided engineering (CAE) software for a variety of multi-physics and multi-scale structural and computational fluid dynamics analyses that all compete for the same HPC workflow resources. For today’s economics of HPC, these resources such as CPU cycles, memory, system bandwidth and scalability, storage and I/O, and file and data management – must deliver the highest levels of CAE productivity and HPC reliability that is possible from a Linux platform environment. This presentation examines workflow efficiencies of CAE simulations for relevant applications in LS-DYNA for an HPC Linux platform developed by SGI. LS-DYNA modeling parameters such as model size, element types, schemes of implicit and explicit (and coupled), and a variety of simulation conditions can produce a wide range of computational behavior and data management requirements, such that careful consideration should be given to how system resources are configured, deployed, and allocated to meet increasing user demands. The HPC system technology of the SGI® AltixTM clusters and servers, based on Linux® and Itanium® 2 from Intel®, have demonstrated both LS-DYNA turnaround and throughput achievement that includes industrial-sized examples. In addition, SGI simulation data management technology of HPC file systems and data storage tools, are providing the LS-DYNA workflow management necessary to maximize user productivity, and enable a user roadmap of increasing LS-DYNA modeling fidelity.

  • Considering damage history in crashworthiness simulations

    Frieder Neukamm, Markus Feucht - Daimler AG, André Haufe - DYNAmore GmbH

    Crashworthiness simulations using explicit Finite Element methods are a central part of the CAE process chain of car body development. Since crash tests of prototype cars at an early development stage are very expensive, a maximum in predictive performance of crash simulations can make a substantial contribution to a cost-efficient car development process. A central issue to ensure this, is an accurate prediction of crack formation in crashworthiness simulations. As the use of advanced high-strength materials in modern car body structures is increasing, crack formation is more likely to occur in such parts of the body-in-white. Typically, structural parts of a car body are manufactured by means of deep-drawing processes. Due to this, the local properties of these parts can be changed remarkably compared to the unprocessed material. In order to be able to accurately predict crack formation, the damage history including local plastic strain and pre-damage has to be considered. Since the use of forming simulations has become usual practice for sheet metal manufacturing, a damage model suitable to be used for both forming and crashworthiness simulations will be presented in the following. Based on the well-known failure criterion of Johnson and Cook, a generalized formulation is proposed that can account for complex failure modes in modern high strength materials. Numerical examples will be presented to demonstrate the practical use of the damage model for the process chain of sheet metal manufacturing.

  • Considering damage history in crashworthiness simulations

    Frieder Neukamm, Markus Feucht - Daimler AG, André Haufe - DYNAmore GmbH

    Crashworthiness simulations using explicit Finite Element methods are a central part of the CAE process chain of car body development. Since crash tests of prototype cars at an early development stage are very expensive, a maximum in predictive performance of crash simulations can make a substantial contribution to a cost-efficient car development process. A central issue to ensure this, is an accurate prediction of crack formation in crashworthiness simulations. As the use of advanced high-strength materials in modern car body structures is increasing, crack formation is more likely to occur in such parts of the body-in-white. Typically, structural parts of a car body are manufactured by means of deep-drawing processes. Due to this, the local properties of these parts can be changed remarkably compared to the unprocessed material. In order to be able to accurately predict crack formation, the damage history including local plastic strain and pre-damage has to be considered. Since the use of forming simulations has become usual practice for sheet metal manufacturing, a damage model suitable to be used for both forming and crashworthiness simulations will be presented in the following. Based on the well-known failure criterion of Johnson and Cook, a generalized formulation is proposed that can account for complex failure modes in modern high strength materials. Numerical examples will be presented to demonstrate the practical use of the damage model for the process chain of sheet metal manufacturing.

  • Considering Manufacturing Induced Inhomogeneity in Structural Material Models (VMAP)

    B. Jilka, P. Reithofer (4a engineering)

    The ITEA VMAP project aims to gain a common understanding of and interoperable definitions for virtual material modelling in Computer Aided Engineering (CAE). Using industrial use cases from major material domains and representative manufacturing processes, new concepts will be created for a universal material exchange interface for use in virtual engineering workflows. [1] In the VMAP consortium with nearly 30 partners, 4a is focusing on injection molding of plastics. Two sub use cases – namely impact behavior of fiber reinforced thermoplastics and structural behavior of foamed parts - are presented in this contribution.

  • Considering the Local Anisotropy of Short Fibre Reinforced Plastics: Validation on Specimen and Component

    Finding the optimal design of plastic components using FEM tools has become an increasingly important topic for companies and research institutions. However, typical simulation models neglect the local anisotropy of injection moulded plastic components and often fail to predict the correct mechanical behaviour and failure mode. Using an integrative simulation approach, the manufacturing process and the resulting local anisotropies can be incorporated in a structural finite-element model which significantly enhances the predictive quality of the model. This is especially the case for glass-fibre reinforced polymers, where the difference between the mechanical behaviour longitudinal and lateral to the fibre is high. This also concerns the strength of weld lines, which are often inevitable in injectionmoulded parts. Fibre orientation needs to be considered because it is indispensable for understanding weaknesses of a polymer part design. Injection-moulding simulation is already a common tool for process simulation and allows calculating the fibre orientation. For structural analyses, various anisotropic material models have been developed or improved in the last years and interfaces to transfer the orientation become more and more available. This now allows making the step to integrative simulation also on an industrial level. The anisotropic material model, used in this study is *MAT_4a_MICROMEC, a micromechanics model based on the Mori-Tanaka Meanfield Homogenization [1]. In this study, the experience of implementing an integrative simulation approach is presented. Furthermore, the fibre orientation determined by mouldflow simulation and the prediction of mechanical behaviour on specimen and component level are validated.

  • Constitutive Model of Filled Elastomers Capable of Capturing Mullins Effect, Hysteresis, Induced Anisotropy and Permanent Set – Part I: Model Theory & Implementation

    R. Chandrasekaran, M. Hillgärtner, M. Itskov (RWTH Aachen University), M. Müller, F. Burbulla (Dr. Ing. h.c. F. Porsche)

    In this contribution, a finite element implementation of a micromechanically based constitutive model describing several inelastic effects of filled rubbers in multiaxial deformation states is presented. The model describes the elastic and inelastic effects of filled rubbers and is based on the network decomposition concept. Accordingly, the rubber network is decomposed into an isotropic elastic network E, responsible for the polymer matrix, and two anisotropic permanent damage networks (M and H) which are responsible for the filler-polymer interaction. The anisotropic damage networks M and H are capable of capturing the Mullins effect, hysteresis, permanent set and induced anisotropic stress softening. This model is implemented into LS-DYNA® by means of a subroutine within *MAT_USER_DEFINED _MATERIAL_MODELS (UMAT). The user can easily switch between different combinations of elastic and inelastic models by activating and deactivating each network. The user can also select the number of directions to be considered depending on the complexity of the loading history. The model with appropriate material constants demonstrates good agreement with experimental data.

  • Constitutive Model of Filled Elastomers Capable of Capturing Mullins Effect, Hysteresis, Induced Anisotropy and Permanent Set – Part II: Experiments & Validation

    M. Hillgärtner, R. Chandrasekaran, Mikhail Itskov (RWTH Aachen University), M. Müller, F. Burbulla (Dr. Ing. h.c. F. Porsche)

    This contribution discusses experiments necessary to describe the behavior of filled elastomers under large strains. Filled elastomers show a variety of inelastic phenomena such as Mullins effect, hysteresis, induced anisotropy, and permanent set. While uniaxial tension tests to rupture provide virgin loading curves, other tests are necessary to gather information about the inelastic effects mentioned above. In order to capture these phenomena experimentally, cyclic uniaxial tension tests with stepwise increasing load amplitudes are carried out. Since experimental stress-strain curves characterize some restricted set of defined loading conditions (such as uniaxial test, pure shear, or equi-biaxial tension), additional investigations of two-dimensional strain data from arbitrary deformations states are necessary. This strain data can be obtained for example by digital image correlation. In particular, we demonstrate how the previously described constitutive model can be calibrated using a variety of experiments. We verify the calibration comparing the results of our subroutine implemented as UMAT in LS-DYNA with two-dimensional strain data obtained from digital image correlation of a plate with a hole subjected to tension. The described model shows good agreement with the obtained data.

  • Constitutive Modeling for Composite Forming Simulation and Development of a Tool for Composite Material Design

    Masato Nishi, Tei Hirashima, Sean Wang (JSOL Corporation)

    Many of the existing FE models in macroscopic forming simulation of fiber fabric have neglected out-of-plane bending stiffness, by using membrane elements, as it is very low compared to in- plane stiffness. To consider this, the shell-membrane hybrid model (S-M model) proposed in the author’s previous study can capture bending stiffness as a function of the rotation of the mid- surface. However, influence of the transverse shear deformation upon the bending behavior is not able to be described in this model. In this study, in order to simulate the transverse shear deformation robustly, the thick-shell model (TS model) based on Reissner-Mindlin plate theory is applied in forming simulation of carbon fiber fabric. To compare the predictive capability of out- of-plane deformation, especially wrinkling, by the TS model to the conventional S-M model, we identify the material parameters of each model through a series of coupon experiments. In the S- M model, the bending property is derived from 3-point bending tests across yarn and in a 45 ̊ direction, regardless of in-plane properties. On the other hand, the transverse shear modulus is derived from 3-point bending tests with the in-plane properties because the bending behavior results from the rotation of the mid-surface and the transverse shear deformation in the TS model. To complete the study, the forming simulations are carried out by these two FE models and verified by means of comparison with the actual experimental deformations. Small wrinkles that are not captured in the S-M model can be captured in the TS model. Furthermore, a software tool for composite forming simulation that JSOL is developing is presented.

  • Constitutive Modeling of Biological Soft Tissues

    Attila P. Nagy, David J. Benson, Livermore Software Technology Corporation, Livermore, CA 94551, USA;, Vikas Kaul, Mark Palmer, Medtronic plc, Minneapolis, MN 55432, USA

    In the present communication, we introduce a class of material models primarily aimed at simulating the elastic and viscous behavior of biological soft tissues in LS-DYNA®. The constitutive law is modular and each module may comprise of different models. Consequently, the analyst may easily change models in a module and also include additional modules to account for more complex material behaviors within the same keyword. In its most general form, the material is considered nearly incompressible, anisotropic, and hyperelastic with the passive behavior defined using a decoupled strain energy function. The contractile and viscoelastic behavior of the tissue may be considered by invoking extra modules. The models are verified using a wide range of recently published results and show excellent agreement.

  • Constrained Multidisciplinary Topology Optimization

    Willem Roux, Imtiaz Gandikota, Guilian Yi (Livermore Software Technology – an ANSYS Corporation)

    For multidisciplinary topology optimization it can be difficult to select the weights for each load case. This becomes even harder if there are multiple design considerations per case. But if constraint values can be defined, then the problem is solvable, because the problem is transformed into one of satisfying the constraints. The most difficult constraint to control is that of the crash pulse, because the existing linear methodologies cannot be used – solutions such as multipoint strategies and spatial kernels must be introduced instead. The NVH constraints are however linear and solving the NVH constraints in combination with the crash pulse becomes a two-level problem. In this paper we show multidisciplinary design optimization considering constraints from impact, linear statics, and frequency load cases.

  • Contact and Sliding Simulation of Rubber Disk on Rigid Surface with Microscopic Roughness

    Sunao Tokura - JRI Solutions, Ltd.

    It is crucial to obtain detailed information about frictional interaction between tire and road surface to estimate performance of vehicle brake system or tire on real road surface. Simulation using Finite Element Method (FEM) in addition to experimental procedure is regarded to be useful to investigate contact behavior between tire and road surface. However, indeed, it is difficult to apply FEM simulation for such a problem since contact and sliding of rubber on rough rigid road surface may cause local large element distortion on rubber material and simulation may fail by negative volume error. In this paper, modeling of a rubber disk and rigid road surface with microscopic roughness, which can be used as a baseline for simulation of contact behavior between tire and road surface, is described. Some investigation for analysis technique to ensure stable computation of rubber disk and road surface model under severe condition has been made. It was shown that proposed modeling technique could avoid extreme mesh distortion during simulation. It is expected that the proposed technique can be used in simulation of rolling/sliding tire on real road surface.

  • Continuous Simulations from Resistance Spot Welding Process to Joint Strength

    S. Yagishita, T. Kawashima, N. Ma (JSOL)

  • Continuous Surface Cap Model for Geomaterial Modeling: A New LS-DYNA Material Type

    Leonard E Schwer - Schwer Engineering & Consulting Services, Yvonne D Murray - APTEK, Inc.

    The Continuous Surface Cap Model is a new addition to the LS-DYNA geomaterial modeling library of constitutive models (Material Type 145). This new model should replace the use of the Geological Cap Model (Material Type 25) for most applications. The Continuous Surface Cap Model maintains all the functionality of the Geological Cap Model with the addition of the third stress invariant, strain rate effects, and damage modeling. The Continuous Surface Cap Model has also been reported to be about three times faster than the Geological Cap Model in a large scale application. This article briefly describes some of the model features and illustrates its application.

  • Control System in LS-DYNA

    C. Keisser (DYNAmore); I. Yeh (LSTC)

    Control System is a very old concept aimed at improving or changing the behavior of any dynamic system. In our daily lives, there are many control applications like in a toaster or in room temperature regulators but also in our cars when using cruise control or ABS. More recently, Control Syst