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14th International LS-DYNA Conference

Detroit, 2016

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  • *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

  • 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 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 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 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 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 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 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 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 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 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 .

  • 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.

  • 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.

  • 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.

  • 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.

  • 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 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.

  • 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  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 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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.

  • 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 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.

  • 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.

  • CORrelation and Analysis (CORA) in Visual-Environment

    Megha Seshadri (ESI Group), Rohit Ramanna (ESI North America), Shivakumar Shetty (Humanetics)

    CORA (Correlation and Analysis) rating is a curve comparison technique, to evaluate the time-history signals. CORA requires at least two curves for comparison, the reference curve (test result) and the comparison curve (simulation). This method is mainly used in Injury Studies.

  • Coupling of Particle Blast Method (PBM) with Discrete Element Method for buried mine blast simulation

    Hailong Teng (LSTC)

    This paper presents two meshless methods: particles blast method (PBM) and discrete element method (DEM). Particle blast method (PBM) is intend to model the gaseous behavior of high velocity, high temperature detonation products. PBM is developed based on corpuscular method (CPM), which has been successfully applied to airbag deployment simulation where the gas flow is slow. For blast simulation where gas flow is extremely high, the equilibrium assumption in CPM is no long valid. By reformulating the particle interaction algorithm, we proposed the PBM that is capable of modelling thermally non-equilibrium system and applied this method for the simulation of blast loading. DEM focus on the modeling of granular media, which might exhibit complex behavior under different condition. Finally, the paper present the coupling of PBM with DEM for buried mine blast simulation.

  • Crash Testing and Simulation of a Cessna 172 Aircraft: Pitch Down Impact onto Soft Soil

    Edwin L. Fasanella (National Institute of Aerospace), Karen E. Jackson (NASA Langley Research Center)

    During the summer of 2015, NASA Langley Research Center conducted three full-scale crash tests of Cessna 172 (C-172) aircraft at the NASA Langley Landing and Impact Research (LandIR) Facility. The first test represented a flare-to-stall emergency or hard landing onto a rigid surface. The second test, which is the focus of this paper, represented a controlled-flight-into-terrain (CFIT) with a nose-down pitch attitude of the aircraft, which impacted onto soft soil. The third test, also conducted onto soil, represented a CFIT with a nose-up pitch attitude of the aircraft, which resulted in a tail strike condition. These three crash tests were performed for the purpose of evaluating the performance of Emergency Locator Transmitters (ELTs) and to generate impact test data for model validation. LS-DYNA ® finite element models were generated to simulate the three test conditions. This paper describes the model development and presents test-analysis comparisons of acceleration and velocity time-histories, as well as a comparison of the time sequence of events for Test 2 onto soft soil.

  • Crash Testing and Simulation of a Cessna 172 Aircraft: Hard Landing Onto Concrete

    Karen E. Jackson (NASA Langley Research Center), Edwin L. Fasanella (National Institute of Aerospace)

    A full-scale crash test of a Cessna 172 aircraft was conducted at the Landing and Impact Research Facility at NASA Langley Research Center during the summer of 2015. The purpose of the test was to evaluate the performance of Emergency Locator Transmitters (ELTs) that were mounted at various locations in the aircraft and to generate impact test data for model validation. A finite element model of the aircraft was developed for execution in LS-DYNA® to simulate the test. Measured impact conditions were 722.4-in/s forward velocity and 276-in/s vertical velocity with a 1.5° pitch (nose up) attitude. These conditions were intended to represent a survivable hard landing. The impact surface was concrete. During the test, the nose gear tire impacted the concrete, followed closely by impact of the main gear tires. The main landing gear spread outward, as the nose gear stroked vertically. The only fuselage contact with the impact surface was a slight impact of the rearmost portion of the lower tail. Thus, capturing the behavior of the nose and main landing gear was essential to accurately predict the response. This paper describes the model development and presents test-analysis comparisons in three categories: inertial properties, time sequence of events, and acceleration and velocity time-histories.

  • Current Status of LS-DYNA ® Iso-geometric Analysis in Crash Simulation

    Yijung Chen, Shih-Po Lin, Omar Faruque, Jim Alanoly, Mohammed El-Essawi, Ragu Baskaran (Ford Motor Company)

    This paper reports a current implementation of Iso-geometric Analysis (IGA) in crash simulation. Several crash critical enhancements of IGA had been proposed by Ford and implemented by LSTC. Such examples include the fix of shear-locking of Mindlin-Reissner shell and the implementation of attached node to NURBS patch. The benchmark of IGA Mindlin-Reissner shell reveals the existence of mild shear-locking in the default full integration scheme. This problem had been fixed in the new option of selected reduced integration. The non-interpolatory nature of NURBS control points makes them not suitable for CAE nodal operations. The attached-node feature to NURBS patch was then created to output nodal time history and to apply nodal force or nodal constraint for IGA model. To exhibit the superiority of IGA performance, an example of curved component was developed to demonstrate the benefit of exact geometry in computational analysis. A crash-can sled model with fixed rigid wall was built to test IGA features which used in frontal crash. This sled model contains all required ingredients – IGA contacts rigid wall, IGA self-contact, meshless spot-welds connecting to NURBS patch, rigid body-IGA connection, gravity loading, nodal acceleration and the compatibility of *MAT_024 plasticity model with IGA model – to evaluate the performance of IGA in crash safety analysis. The implementation of Bezier extraction to interface with other advanced spline functions and the development of IGA-FE hybrid model for future crash safety development are also addressed.

  • Delamination Prediction of Uni-Directional Composite Laminates using Shell Elements and a Strain Rate Dependent Micro-mechanical Material Model

    Sandeep Medikonda, Ala Tabiei (University of Cincinnati, Cincinnati)

    The effectiveness of studying inter-laminar delamination in composites with the help of newly formulated thickness-stretch shell elements (ELFORM=25) as compared to the traditional plane-stress shell elements (ELFORM=2) has been investigated using LS-DYNA ® . A strain-rate dependent micro-mechanical material model using ply-level progressive failure criteria has been used to simulate the initiation and propagation of delamination. The numerical delamination growth has been qualitatively analyzed against the experimental C-scan images for multiple impact events on a T800H/3900-2 CFRP plate. As an addition to the capability of the micro-mechanical material model, a methodology of assigning physical significance to the choice of damage parameters has been presented.

  • Design and Validation of a Crash Rated Bollard as per SD-STD-02.01 Rev. A (2003) Standard using LS-DYNA ®

    Saurabh R. Deshpande, Santosh E. Chopade, N. V. Karanth (Automotive Research Association of India), Maj. Amitava Mittra (Swaraj Secutech Pvt. Ltd.)

    Use of vehicle barriers for traffic regulation is of utmost importance in a densely populated country like India. These barriers can be used effectively to divert vehicles during public events and emergency situations. Due to their periodic requirement at different locations, it is essential that the barriers provide visibility and security while remaining comparatively cheaper at the same time. Out of the different types of available barriers like solid walls, pillars, beams, gates, etc., a bollard (vertical pole protruding from the ground to a very less but visible height) is the most effective in terms of space occupied and absorption of impact energy. Multiple bollards used in series are effective towards withstanding large vehicle impacts, while allowing passage to pedestrians and bicycle riders with ease. The prevalent methodology of evaluating energy absorption capacity of bollard as per SD-STD-02.01 Rev. A (2003) standard includes physical impact of the designed bollard by designated vehicle type (M type of vehicles) for K-4, K-8 and K-12 types of crash ratings. A finite element (FE) model of the designed bollard was analyzed under similar impact conditions using crash analysis software (LS-DYNA v. 971). The FE results were validated with the results of the physical test conducted subsequently. Parametric optimization of the K-12 rated FE bollard was conducted and a new bollard design for K-8 rating was thus prepared and analyzed for vehicular impact. The use of Computer Aided Engineering (CAE) tools and FE analysis during design stage itself aimed at reducing the cost and time required to build and successfully test the bollard for crash rating.

  • Design optimization with Modal Assurance Criteria (MAC)

    Sumie Kinouchi, Ryo Ishii, Masahiro Okamura (JSOL Corporation)

    Simulation-based optimization is one of the efficient tools for product design optimization. This paper introduces the application example of modal analysis with LS-DYNA® and mode tracking of LS-OPT ®, to improve the body stiffness. The mode tracking is a powerful tool to track a specific mode by evaluating the scalar MAC value even if the sequence of modes is changed due to the modification of the design variables by the optimizer. For the connection in the car body model, adhesive bonding is included as well as spot welding.

  • Development and Validation of Bolted Connection Modeling in LS-DYNA ® for Large Vehicle Models

    Michalis Hadjioannou, David Stevens, Matt Barsotti (Protection Engineering Consultants LLC)

    As part of the United States Marine Corps (USMC) Mitigation of Blast Injuries through Modeling and Simulation project, Protection Engineering Consultants performed numerical and experimental investigations to develop modeling approaches for bolted connections. Vehicle models require efficient yet accurate methods to represent bolted connections, especially under extreme loading situations where connection behavior may have crucial impact on the accurate prediction of the response. Efficient connection models require relatively coarse mesh sizes and computationally cheap element types that allow modeling large numbers of connections in vehicle models. This paper describes the development and validation of reduced bolted connection models that utilize a combination of beam and shell elements. The models were developed and validated with data from bolted connections that were tested under static and dynamic loading conditions. The tests provided valuable data for the refinement of the models, which are shown capable of simulating connection behavior up to and including rupture. Important aspects of the modeling procedure are highlighted including contact definitions and bolt preloading, as well as inherent limitations that exist in such models. The study also demonstrates the importance of material failure parameters such as triaxiality-dependent and strain-rate-dependent fracture. These parameters influence not only the connection capacity but also the absorbed energy before the connection fails. Considerations of the absorbed energy are crucial when assessing the safety of occupants in vehicles under extreme loading conditions.

  • Development and Validation of a 95 th Percentile Male Pedestrian Finite Element Model

    Wansoo Pak, Costin D. Untaroiu (Virginia Tech)

    The pedestrian is one of the most vulnerable road users. Given an impact event, the probability of a pedestrian fatality in a traffic crash is almost two times higher than that for a vehicle occupant. Therefore, pedestrian protection regulations which involve subsystem tests in car-to-pedestrian collisions (CPC) have been proposed in Europe and Asia. In addition, human finite element (FE) models have been developed to better understand the whole vehicle- pedestrian interaction, and assess the pedestrian injuries. However, the majority of these human th models represent a 50 percentile human, so their responses cannot be extrapolated to understand the responses of pedestrian with other anthropometries during a CPC. The main goal of this study was to develop and validate a FE model corresponding to a 95 th percentile male (M95) pedestrian. The model mesh was developed by morphing the Global Human Body Models Consortium (GHBMC) 50 th percentile male (M50) pedestrian model to the reconstructed geometry of a human subject having 194 cm height and 103 kg weight. The material properties of the M95 pedestrian model were assigned based on GHBMC M50 occupant model. The knee joint and upper torso of the FE model were preliminarily validated against Post Mortem Human Surrogate (PMHS) test data recorded in four-point knee bending tests and upper body blunt lateral impact tests. Then, pedestrian-to-vehicle impact simulations were performed using the whole pedestrian model and the results were compared to corresponding pedestrian PMHS tests. Overall, the results generated by the FE model showed to be well correlated to test data. Therefore, the model could be used to investigate various pedestrian accidents or to improve vehicle front end design for pedestrian protection.

  • Development of a Finite Element Model of the WIAMan Lower Extremity to Investigate Under-body Blast Loads

    Wade Baker, Costin Untaroiu (Virginia Tech), Mostafiz Chowdhury (US Army Research Laboratory)

    Occupants of military vehicles are likely to be subjected to an under-body blast (UBB) resulting from anti – vehicular land mines and improvised explosive devices (IEDs). For years the automotive industry has successfully used human anthropomorphic test devices (ATDs) to help quantify the occupant injury risk over a wide range of impact scenarios. However, it has been proven that these ATDs are inadequate when it comes to accurately measuring the response of the human to under-body blast loading. Therefore, a new dummy concept, called WIAMan (Warrior Injury Assessment Manikin) is being developed together by various research institutions and industry leaders. A numerical model of the lower leg was developed in LS- DYNA ® based on CAD geometry of the dummy. Material models in LS-DYNA were assigned based on high and low strain-rate tests to model the viscoelastic behavior of the soft tissue used to represent the flesh, heel pad, foot plate, and tibia compliant element of the dummy leg. The WIAMan FE model was simulated under identical conditions as the experiments done on the physical dummy. A comparison between the outputs from the simulation and the test data was used to validate the unbooted WIAMan lower extremity (WIAMan-LX) model. The proposed numerical models of materials exhibiting viscoelastic responses show good correlation to the test data at both high and low strain rates. Simulations of the entire WIAMan-LX correlate well to the WIAMan physical dummy tests. Additionally, a comparison of the WIAMan to Hybrid-III and post-mortem human surrogate (PMHS) tests is presented. Future work includes further validation of the model and correlating the responses of the dummy to risk of human injury.

  • Development of a Finite Element Model of a Motorcycle

    N. Schulz, C. Silvestri Dobrovolny and S. Hurlebaus (Texas A&M Transportation Institute)

    Over the past years, extensive research efforts have been made to improve roadside safety hardware to reduce injury to occupants of four wheel vehicles and heavy trucks. In comparison, limited research has been conducted to address the safety of motorcycle riders when impacting roadside safety hardware. The vulnerability of motorcycle riders can lead to a high risk of injury for the rider, especially when impacting roadside barriers. In real-world motorcycle crashes there is a wide range of impacts against other vehicles and barriers. Reproducing these different motorcycle crash scenarios through physical crash testing can be considerably costly and time consuming. Computer simulations are a great tool to address the wide range of impacts in real world motorcycle crashes because they are significantly cheaper and quicker than performing full scale crash tests. Motorcycle simulation models have been developed since the 1970’s and have improved in detail and complexity over the years. However, there is still a need to develop detailed motorcycle models that are geometrically accurate and can accurately predict motorcycle response behavior. The researchers have developed a Finite Element (FE) computer model of a motorcycle through reverse engineering. This model can be used to investigate impact scenarios involving motorcycles. To validate the accuracy of the model, measurements of the motorcycle computer model such as mass, geometry, etc, were compared to measurements of the physical motorcycle.

  • Development of a Simplified Finite Element Approach for Investigation of Heavy Truck Occupant Protection in Frontal Impacts and Rollover Scenarios

    C. Silvestri Dobrovolny, N. Schulz (Texas A&M University System)

    A finite element model combining a heavy truck conventional-type cabin structure, its interior components, ATD, and passive restraint systems was developed to simulate real-world typical crash scenarios, such as frontal impacts and rollover crashes. These crash scenarios are considered conditions for which there is need and still room for improvement in terms of occupant safety. This paper describes the modeling effort to develop a cabin structure with its interior components through reverse engineering and the development of simplified approaches to replicate finite element computer simulations of frontal impact and rollover scenarios. The model was used to replicate head-on crashes into a rigid barrier at 35 mph which are representative of impact conditions typical of NHTSA NCAP tests. For this crash scenario, an existing FE full tractor-semitrailer model was employed to collect the typical crash pulse resulting from a head-on impact crash. The crash pulse was subsequently applied to defined locations of the new FE cabin model with inclusion of interior components, ATD, and restraint systems. Parametric simulations were then performed by varying characteristics of passive restraint systems and acceleration data from ATD body regions was collected to assist with the calculation of body injury levels for each simulated case. The developed model was also employed to replicate a critical rollover event, determined to be the result of an evasive maneuver followed by an overcorrecting maneuver, with an initial truck speed of 60 mph. To replicate this sequence of maneuvers, a simplified approach was proposed by analyzing truck kinematics through the TruckSim software program. Subsequently, kinematics outputs were applied to the center of the floor of the LS-DYNA® finite element cabin model. The researchers suggest future work to be conducted to address approach limitations, such as validating cabin interiors material models and including cabin deformation, which is not currently incorporated in the simplified proposed approach.

  • Development of a Subcell Based Modeling Approach for Modeling the Architecturally Dependent Impact Response of Triaxially Braided Polymer Matrix Composites

    Christopher Sorini, Aditi Chattopadhyay (Arizona State University), Robert K. Goldberg, and Lee Kohlman (NASA Glenn Research Center)

    Understanding the high velocity impact response of polymer matrix composites with complex architectures is critical to many aerospace applications, including engine fan blade containment systems where the structure must be able to completely contain fan blades in the event of a blade-out. Despite the benefits offered by these materials, the complex nature of textile composites presents a significant challenge for the prediction of deformation and damage under both quasi-static and impact loading conditions. The relatively large mesoscale repeating unit cell (in comparison to the size of structural components) causes the material to behave like a structure rather than a homogeneous material. Impact experiments conducted at NASA Glenn Research Center have shown the damage patterns to be a function of the underlying material architecture. Traditional computational techniques that involve modeling these materials using smeared, homogeneous, orthotropic material properties at the macroscale result in simulated damage patterns that are a function of the structural geometry, but not the material architecture. In order to preserve heterogeneity at the highest length scale in a robust yet computationally efficient manner and capture the architecturally dependent damage patterns, a previously-developed subcell modeling approach is utilized. This work discusses the implementation of the subcell methodology into the commercial transient dynamic finite element code LS-DYNA ® . Verification and validation studies are also presented, including simulating the tensile response of straight sided and notched quasi-static coupons composed of a T700/PR520 triaxially braided (0°/60°/–60°) composite. Based on the results of the verification and validation studies, advantages and limitations of the methodology and plans for future work are discussed.

  • Droptower Impact Testing & Modeling of 3D-Printed Biomimetic Hierarchical Composites

    Grace Xiang Gu, Steven Kooi, Markus J. Buehler (Massachusetts Institute of Technology), Alex J. Hsieh (Massachusetts Institute of Technology,US Army Research Laboratory), Chian-Feng Yen (US Army Research Laboratory)

    Inspired by the hierarchical designs of natural materials, this paper highlights the use of 3D-printing as a plausible pathway to discern and differentiate material attributes critical to desirable impact properties. A comprehensive study was focused on the influence of three different hierarchical designs derived from a nacre-like architecture, where two base materials varying vastly in properties were used to evaluate the low-velocity impact on 3D-printed hierarchical materials. The work presented here develops a numerical model to characterize the failure modes and damage behavior of various hierarchical materials organized in different configurations. The finite element software LS-DYNA ® is used where force-displacement responses and damage patterns obtained from simulation are compared with experimental results obtained from drop tower impact tests. This study clearly demonstrates that the emerging 3D-printing technology can enable rapid prototype towards hierarchical ductile/brittle hybrid designs for future impact resistant materials.

  • Durability assessment of welded structures based on welding simulation with LS-DYNA ®

    Andriy Krasovskyy (DYNAmore Swiss GmbH), Antti Virta (Winterthur Gas & Diesel Ltd), Thomas Klöppel (DYNAmore GmbH)

    The importance of welding for modern structural engineering cannot be emphasized enough. Different techniques are currently applied in the industrial environment offering almost unlimited possibilities regarding manufacturability with high cost effectiveness. At the same time the requirements on welded structures are increasing and so the requirements on the design methods. This paper presents an advanced calculation method for fatigue assessment of welds based on the simulation of a welding process in LS-DYNA ® , thermophysical material modeling and fracture mechanics. The proposed method considers the most important aspects for durability prediction of welds. Applying worst-case assumptions, fatigue limits derived by the weight function method can be used in the lifetime assessment of complex welded structures together with the critical plane approach in order to consider a multiaxial nonproportional loading.

  • Durability Study for Tractor Seat Using LS-DYNA ®

    Jithesh Erancheri, Ramesh Venkatesan (Kaizenat Technologies Pvt Ltd)

    Today in many tractors with enclosed cabs, an extra seat named as 'instructor seat' are available. As a regular driver seat, this seat should also undergo the same testing and product validation process. This seat is incorporated to serve various purposes like enhances the training of tractor operators, facilitates communications between workers, improves the demonstration of for-sale tractors, transports workers to worksites, assists operations requiring extra help etc. LSTC's LSDYNA introduced a powerful vibro-acoustic solver which can address almost all major problems in the frequency domain. In this paper, we used the explicit capability of LS-DYNA to model the drop of tractor Instructor seat (henceforth called a I -Seat) and then the frequency domain capability to estimate the damage of parts that undergoing steady state loading . We have used LS-DYNA's new fatigue solver capability for SSD loading to predict the damage.

  • Effect of Thin-walled Tube Geometry on Its Crashworthiness Performance

    Anton Kuznetcov, Igor Telichev, Christine Q. Wu (University of Manitoba)

    The present paper deals with the numerical analysis supporting the crashworthiness design of a thin-walled tube. The thickness and wall shape were parametrically changed to study their effect on the tube performance under the axial impact. Different tube geometries were evaluated based on the common crashworthiness criteria to identify the effective designs which provide the efficient energy absorption and low peak force. The applicability of selected criteria for crashworthiness design was discussed. The observations obtained in the parametric study can be used to improve the crash behavior of energy-absorbing structures.

  • Eigensolution Technology in LS-DYNA ®

    Roger Grimes (LSTC)

    LSTC has been adding additional eigensolution technology to LS-DYNA. For several years LS-DYNA has a Block Shift and Invert Lanczos Eigensolver in both SMP and MPP implementations. But this capability did not cover the full spectrum of applications. We have supplemented the Lanczos solver with a Power Method solver for Implicit mechanic problems using the Inertia Relief Feature. As we have been adding unsymmetric modeling features through materials, elements, and contact, we have added an eigensolver based on ARPACK for such problems. Important applications for the unsymmetric eigensolver are rotational dynamics and brake squeal analysis. We are also developing an implementation of AMLS (Automated Multilevel Substructuring Method) for applications such as NVH that want hundred, even thousands, of eigenmodes quickly which are willing to have a less accurate solution compared to the Lanczos eigensolver.

  • Evaluation of Various Numerical Methods in LS-DYNA ® for 3D Crack Propagation

    Ala Tabiei, Wenlong Zhang (University of Cincinnati)

    In this paper, four different numerical methods implemented in the large scale simulation code LS-DYNA ® are evaluated to determine their abilities and limitations in fracture problems especially 3-d crack propagation problems. These methods are: Finite Element Method (FEM), Discrete Element Method (DEM), Element Free Galerkin (EFG) method and Extended Finite Element Method (XFEM). Their methodologies are briefly described and several numerical simulations are carried out and compared with experiment results. In some examples, fracture parameters are evaluated and mesh sensitivity is studied. Their potentials and limitations are discussed.

  • Experimental and Numerical Investigation of the Tearing Resistance of a Parachute Woven Fabric using LS-Dyna ®

    B.Perin, R.Blois, P.Bordenave (DGA Aeronautical Systems), Ch.Espinosa (Université de Toulouse)

    The performance of a parachute system is conditioned by its ability to sustain the loads applied by its environment during its life. Among others tear resistance is crucial since the unstable propagation of small defects into cracks can lead to the catastrophic loss of load carrying capacity. Defects under consideration are pre-existing notches or cuts. Experimental campaigns of quasi-static tear resistance in the warp and weft directions of parachute woven flexible fabrics have been realized at DGA Aeronautical Systems following the normalized tests defined by NF G07- 145 and NF G 07-149 (‘trousers’ tear or Single Rip Method, and ‘nail’ tear, see Fig. 1). On the contrary to the case of a metallic material, which tear resistance can be related to notch resistance through the yield strength and local plasticity, tear resistance of a tissue involves complex stress and stain distributions in the yarns of the woven fabric. It is shown that sliding of the rip stop yarns are not well handled by the testing standards. A numerical simulation plan has been designed and operated in order to determine the characteristics of a representative numerical model for both the material behavior and the large flexible structure, in the perspective of including it in a full 3D FSI simulation. Results are presented and compared to experimental ones. Using a homogenized anisotropic material, the size of the mesh and the contact algorithm are the critical parameters that handle the crack propagation through the local wrinkles and stresses description. Even though the out of plane deformations are not completely well reproduced for the Single Rip Method, the final numerical model is quite satisfactory regarding the force- displacement curve prediction for both test standards. Perspectives are driven for both enhancing the testing standards and deriving a more representative model for future 3D FSI models.

  • Finite Element Investigation of Injury Risks of Immature Pelvis and Femur in Pedestrian Impact

    Ming Shen, Anil Kalra, Runzhou Zhou, Xin Jin, King H. Yang (Wayne State University), Binhui Jiang (Hunan University), Yajing Shu (Chongqing University)

    Car-to-pedestrian collision is a major cause of injury and death for children. Due to the different anthropometric features of a child compared to an adult, children present more injuries in the pelvic region (including the proximal femur) than adults do. It was hypothesized that the epiphyseal growth plates (GPs) in the hip region may affect the stress distribution and further influence the injury pattern seen in children. To quantitatively address this issue, finite element (FE) simulations of an SUV-to-pedestrian impact was conducted. The human model was built based on a 10-year-old whole-body FE model (CHARM-10) embedded with the GPs at the pelvic region (triradiate cartilages at the bottom of acetabulum) and the proximal femur (femoral head GP and greater trochanter GP). The GP geometries were taken from clinical images and medical study reported in the literature. The material properties were derived from a set of optimization procedures using the published experimental results. The results of the parametric studies revealed that the GPs have significant effects on the mechanical responses and injury outcomes. More specifically, the hip joint contact force was reduced, implying a reduced stiffness of the pelvic girdle; the risks of fractures at the femoral shaft and acetabulum are decreased; the risk of pelvic ramus fracture is elevated. Further simulations explained the detailed effect of each of the three GPs at the hip region.

  • Frequency Domain Analysis for Isogeometric Element in LS-DYNA ®

    Liping Li, Yun Huang, Zhe Cui (LSTC), Stefan Hartmann (DYNAmore GmbH), David J. Benson (Professor for Structural Engineering)

    In the past few years numerous researches have been done in the area of Isogeometric Analysis (IGA), as the simulation model is exactly the desired geometry in this method. Frequency domain analysis is a cheap and fast alternative for time domain analysis. It is particularly suitable for vibration and acoustic analysis, which are very important topics for the design and research of automotives. This paper gives some frequency domain analysis for isogeometric elements, and the results are compared with the finite element analysis (FEA) results.

  • Friction in LS-DYNA®: Experimental Characterization and Modeling Application

    Sheng Dong, Marcelo Dapino (The Ohio State University), Allen Sheldon, Kishore Pydimarry (Honda R&D Americas, Inc.)

    Friction is a widely observed phenomenon in all engineering systems. The importance of friction in computer-aided engineering has long been overlooked and modeling of friction phenomenon has been oversimplified. This paper reports experimental work conducted on a pin-on-disc tribometer to characterize the coefficients of friction between various material combinations, and modeling work of using such measured coefficients in different CAE models. Tested material combinations include coated steel on coated steel and rubber on coated steel. The coefficients were measured under different normal stresses and linear velocities, and employed to a three- point bending model and a pedestrian collision model in CAE tools such as LS-DYNA. It was found that friction plays an important role in deciding the magnitudes and timing of the acceleration or force when initial collision takes place. Higher friction results in higher magnitude of acceleration and force, but shorter sliding distance after the initial collision. Parametric study adopts different values for the coefficient of friction, and the results show that there exist boundaries, within which the role of friction is more evident. Below the lower boundary value, the effect of friction was dwarfed by other factors. Above the upper boundary value, the effect of friction saturates. This methodology of measuring and applying friction coefficients can be applied to various CAE models beyond pedestrian-vehicle collision to assist finding better correlation between simulations and testing data.

  • Identifying Traumatic Brain Injury (TBI) Thresholds Using Animal and Human Finite Element Models Based on in-vivo Impact Test Data

    Keegan Yates, Costin Untaroiu (Virginia Tech)

    Traumatic brain injuries (TBIs) cause roughly 50,000 deaths per year in America. In order to lessen the severity or prevent TBIs, accurate dummy models, simulations, and injury risk metrics must be used. Human data is ideal to develop models, but injury conditions are often complex, e.g. primary and secondary impacts, and tissue level response can often only be studied via an autopsy, but death usually only occurs as the result of severe TBI. To develop better graded injury risk metrics, animal study data must be applied to the human brain. The ultimate objective of our study was to develop a better method to scale injury data by using finite element analysis (FEA). In this study, a finite element model of a Göttingen miniature pig brain and skull was created from MRI and CT images. These pigs’ brains have several characteristics in common with human brains that that make them suitable for testing such as shape and material properties. The regions of the brain were divided into white matter, gray matter, and the ventricles each with viscoelastic material properties. To validate this model, tests were conducted using Göttingen miniature pigs in a translation/rotation injury device subjecting the pig skull to a linear acceleration from 40-96 g’s and an angular acceleration from 1,000-3,800 rad/s 2 . Four of these pigs’ brains were embedded with neutral density radio-opaque markers to track the motion of the brain with a biplanar X-ray system. Fifteen pigs were also tested without markers to allow for injury data to be taken with MRI scans and immunohistochemistry. The impact was then simulated in LS-DYNA ® , and the motion of nodes closest to the marker locations was recorded and used to optimize material parameters. When used in tandem with a human model this will allow for a more accurate transfer function to scale injury data from a pig study to be relevant to humans. While the loading conditions in this study simulate a small range of possible injuries, the scaling methods involved may be applicable to a wide variety of injuries from sports injuries to blasts.

  • Improvements for Implicit Linear Equation Solvers

    Roger Grimes, Bob Lucas, Clement Weisbecker (LSTC)

    Solving large sparse linear systems of equations is often the computational bottleneck for implicit calculations. LSTC is both continuously improving its existing solvers, and continuously looking for new technology. This talk addresses both, describing improvements to the default distributed memory linear solver used by LSTC as well as promising new research. We discuss improvements to the symbolic preprocessing that reduce the occurrences of sparse matrix reordering, a sequential bottleneck and significant Amdahl fraction of the wall clock time for executions with large numbers of processors. Our new approach works for large Implicit models with large numbers of processes when the contact surfaces do not change, or only change slightly. We have also improved the performance of numerical factorization, most significantly with the introduction of a tiled, or two-dimensional distribution of frontal matrices to processors. This improves the computational efficiency of the factorization and also reduces the communication overhead. Finally, we present promising early results of research into using low-rank approximations to substantially decrease both the computational burden and the memory footprint required for sparse matrix factorization.

  • Incorporation of Damage and Failure Into an Orthotropic Elasto-Plastic Three-Dimensional Model with Tabulated Input Suitable for Use in Composite Impact Problems

    Robert K. Goldberg and Kelly S. Carney (NASA Glenn Research Center), Paul Du Bois (George Mason University), Canio Hoffarth, Bilal Khaled and Subramaniam Rajan (Arizona State University), Gunther Blankenhorn (LSTC)

    A material model which incorporates several key capabilities which have been identified by the aerospace community as lacking in the composite impact models currently available in LS-DYNA ® is under development. In particular, the material model, which is being implemented as MAT 213 into a tailored version of LS-DYNA being jointly developed by the FAA and NASA, incorporates both plasticity and damage within the material model, utilizes experimentally based tabulated input to define the evolution of plasticity and damage as opposed to specifying discrete input parameters (such as modulus and strength), and is able to analyze the response of composites composed with a variety of fiber architectures. The plasticity portion of the orthotropic, three-dimensional, macroscopic composite constitutive model is based on an extension of the Tsai-Wu composite failure model into a generalized yield function with a non-associative flow rule. The capability to account for the rate and temperature dependent deformation response of composites has also been incorporated into the material model. For the damage model, a strain equivalent formulation is utilized to allow for the uncoupling of the deformation and damage analyses. In the damage model, a diagonal damage tensor is defined to account for the directionally dependent variation of damage. However, in composites it has been found that loading in one direction can lead to damage in multiple coordinate directions. To account for this phenomena, the terms in the damage matrix are semi-coupled such that the damage in a particular coordinate direction is a function of the stresses and plastic strains in all of the coordinate directions. The onset of material failure, and thus element deletion, is being developed to be a function of the stresses and plastic strains in the various coordinate directions. Systematic procedures are being developed to generate the required input parameters based on the results of experimental tests.

  • Incorporation of Inconel-718 material test data into material model input parameters for *MAT_224

    Stefano Dolci1, Kelly Carney1, Leyu Wang, Cing-Dao Kan (George Mason University), Paul Du Bois (Consulting Engineer, Northville)

    A research team from George Mason University, Ohio State University, NASA and FAA has developed material data and analytical modeling that allows for precise input of material data into LS-DYNA ® using tabulation and the *MAT_224 material model. The input parameters of this model are based on data from many experimental coupon tests including tension, compression, impact, shear and biaxial stress states. The material model also includes temperature and strain rate effects. This research effort involves the incorporation of the Inconel-718 material test data into the material model. This requires the development and validation of a set of material constants for this particular alloy, utilizing the tabulated input method of material model *MAT_224 in LS-DYNA with consideration given to strain rate and temperature. Alloy Inconel-718 is a precipitation hardenable nickel-based alloy designed to display exceptionally high yield, tensile and creep-rupture properties at temperatures up to 1300°F. The sluggish age-hardening response of alloy 718 permits annealing and welding without spontaneous hardening during heating and cooling. This alloy has been used for jet engine and high-speed airframe parts such as wheels, buckets, spacers, and high temperature bolts and fasteners. *MAT_224 is an elastic-plastic material with arbitrary stress versus strain curve(s) and arbitrary strain rate dependency, all of which can be defined by the user. Thermo-mechanical and comprehensive plastic failure criterion can also be defined for the material. This requires a process of test data reduction, stability checks, and smoothness checks to insure the model input can reliably produce repeatable results. Desired curves are smooth and convex in the plastic region of the stress strain curves.

  • Interactive Dynamic Analysis of Subsea Lifting Ropes

    George Laird, Kirk Fraser (Predictive Engineering, Inc.), Ryan Marsh (Sound Ocean Systems, Inc.)

    The dynamic movement of subsea ropes presents an interesting numerical challenge due to the coupling of drag forces with the dynamic response of the rope. Although a FSI approach of fully coupling the surrounding seawater to the rope is theoretically possible it lies beyond the reach of practical engineering when discussing rope lengths in kilometers and possible rope movements in hundreds of meters. A new analysis technique is presented where the drag forces associated with subsea dynamic rope movement are directly integrated into the solution using the LS-DYNA® user subroutine, LOADUD. Drag forces are calculated from analytical solutions to provide discrete drag forces as a function of rope position and velocity. This technique avoids the complexity of a fully-coupled FSI solution while providing the major benefits capturing how the rope will dynamically move while lifting heavy loads while being subjected to strong sea currents. Results are presenting showing how a two kilometer rope would dynamically behave while lifting a heavy load from sea bottom to surface under stratified sea currents.

  • Introducing New Capabilities of JFOLD Version 3 and Airbag Folding Examples

    Richard Taylor (Ove Arup & Partners International Limited), Shingo Yagishita, Shinya Hayashi (JSOL Corporation)

    A software tool called JFOLD has been developed by JSOL Corporation to enable successful airbag folding using LS-DYNA ® . This paper introduces some new capabilities of JFOLD Version 3 and demonstrates folding examples. JFOLD runs inside the powerful and popular pre-processor Primer. JFOLD Version 1 was released in July 2013 and has been continuously developed to make folding airbags quicker and easier.

  • Introduction of Rotor Dynamics using Implicit Method in LS-DYNA ®

    Liping Li, Roger Grimes (LSTC), Thomas Borrvall (DYNAmore Nordic AB)

    Rotor dynamics is commonly used to analyze the behavior of structures ranging from jet engines and steam turbines to auto engines and computer disk drives. This paper introduces the implementation of rotor dynamics in LS-DYNA. The structural transient analysis and mode analysis and other applications, like brake squeal analysis, are presented and validated with other finite element software.

  • Jones-Wilkens-Lee (JWL) Equation of State with Afterburning

    Leonard E Schwer (Schwer Engineering & Consulting Services)

    The standard Jones-Wilkens-Lee equation-of-state for modeling detonation of high explosives was modified to allow inclusion of the additional energy associated with afterburning of fuel rich (oxygen poor) high explosives. Three options are available for including the additional afterburning energy: 1. Constant energy rate addition 2. Linear energy rate addition 3. Miller Extension The performance of the afterburning equation of state is demonstrated via comparison with three experimental and numerical examples: 1. LLNL HEAF Tests, Kuhl et al. (1998): 2. NCEL Tests, Keenan and Wager (1992): 3. Moby Dick Test, Miller & Guirguis (1993)

  • Latest developments in Automotive Aerodynamics Using LS-DYNA ®

    Iñaki Çaldichoury, Facundo Del Pin, Rodrigo Paz (LSTC)

    LS-DYNA® is a general purpose explicit and implicit finite element program used to analyse the non-linear dynamic response of three-dimensional solids and fluids. It is developed by Livermore Software Technology Corporation (LSTC). A module to simulate incompressible flows has been added to LS-DYNA® for coupled fluid/mechanical/thermal simulations (ICFD solver). It offers a response to the ever increasing need of engineers in the automotive industry sector and elsewhere to comprehend and solve complex highly nonlinear problems involving multiple domains of physics. However, if the ICFD solver is to become a viable proposition in automotive aerodynamics, it must demonstrate its ability to accurately reproduce the elementary phenomena observed on simple geometric forms in the wind tunnel. With this objective in mind, the present paper will show for different wind speeds what results can be obtained on widely studied simplified car geometry, the Ahmed body, focusing on the complex 25 ° slant degree case.

  • Looping Formation During Colonoscopy A Simulation

    Charles R. Welch, John D. Reid (University of Nebraska-Lincoln)

    A simulation of a loop formation during colonoscopy is attempted using LS-DYNA . The tissue is comprised of a Mooney-Rivlin rubber model adjusted iteratively to somewhat match raw force-displacement data of small intestine tissue. After finding adequate parameters for friction and damping coefficients, the scope is advanced into a colon model in the simulation and loop formation appears. Whether the loop formation obtained through simulation is realistic remains to be determined due to lack of good test data.

  • Low Risk Deployment Passenger Airbag – CAE Applications & Strategy

    Bill Feng (Jaguar Land Rover)

    Occupants who were out-of-position (OOP) in the vehicles would increase the risk of airbag induced injuries in the crash event. The punch out forces resulting from the airbag deployment act on the occupant and would cause potential injuries. To evaluate the OOP performance of the airbag system, FMVSS208 requests a series of test loadcases. In passenger side OOP, it includes test loadcases with rear-facing child seats, 3yld and 6yld in two different occupant positions. Design of low risk deployment passenger airbag system requires balanced considerations of in-position occupant protection performance and out-of-position performance. A research project has been conducted to investigate those relationships in great details. In this paper, the development of CAE capability to predict low risk deployment passenger airbag behaviors is presented. Using validated CAE mode a series of studies have been conducted to define depowered inflator which can meet the needs of both in-position and out-of-position performances. This forms the key strategy for low risk deployment passenger airbag in design applications.

  • LS-DYNA ® Model Development of the Harmonized Hybrid III 05F Crash Test Dummy

    Chirag S. Shah, George Hu, Jianying Li (Humanetics Innovative Solutions, Inc.), Richard Barnes (Ford Motor Company)

    Finite Element (FE) models of Anthropomorphic Test Device (ATD) commonly known as crash test dummies have become increasingly employed in automotive safety with the underlying benefits of cost and product development cycle. The current paper highlights the development of the harmonized Hybrid III 5th percentile (small female) dummy model referred hereafter as the “HH305 V1.0” LS-DYNA FE model. To be compliant with Euro NCAP test requirements, the model has been incorporated with the SAE harmonized jacket and meets both the lower and higher velocity thorax pendulum impact certifications. The development of HH305 V1.0 FE model particularly focused on accuracy of the thorax performance. The thorax performance of the model was evaluated for a variety of loading conditions such as single rib drop tests, thorax pendulum impact tests and the new aggressive seatbelt pretension tests on the thorax assembly. The seatbelt pretension tests were conducted in collaboration with Ford Motor Company and aimed to improve the thorax correlation for relatively smaller chest deflection at faster rate. The HH305 V1.0 model performance is significantly better compared to its predecessor in all the simulated thorax load-cases. The HH305 V1.0 release for the LS-DYNA FE model is commercially available to customers.

  • LS-DYNA ® Peridynamics for Brittle Fracture Analysis

    Bo Ren and C. T Wu (Livermore Software Technology Corporation), E. Askari (Boeing Commercial Airplane)

    Peridynamics is a new nonlocal theory that provides the ability to include displacement discontinuities in a continuum body without explicitly modelling the crack surface. In comparison to the classical weakly nonlocal or strictly nonlocal models, the peridynamics equation of motion is free of spatial derivative of displacement. The peridynamics also does not require sophisticated book keeping of degrees of freedom or jump conditions in tracking the moving discontinuities. Those features of peridynamics offer significant advantages over other advanced numerical methods for the brittle fracture analysis particularly in three-dimensional problems. The explicit dynamics version of bond-based peridynamics model has been implemented in LS-DYNA ® using the Discontinuous Galerkin (DG) finite element approach to enforce the boundary conditions, constraints, contacts as well as to handle the non-uniform mesh in the engineering practice. The classic material parameters, such as elastic modulus and fracture energy release rate are employed for the determination of material response and failure in brittle material. The LS-DYNA ® Peridynamics supports 8, 6 and 4-noded solid elements with the ability to handle multiple and branching cracks. Several numerical benchmarks are utilized to demonstrate the effectiveness and accuracy of the LS-DYNA ® peridynamics in brittle fracture analysis.

  • LS-DYNA ® Smoothed Particle Galerkin (SPG) Method with Strain Gradient Stabilization and Thermal Effects

    Yong Guo, C.T. Wu, Wei Hu (LSTC)

    The Smoothed Particle Galerkin (SPG) method in gradient form is presented and implemented in LS-DYNA for large inelastic deformation and material failure analyses from low to moderated high speed applications. The new formulation is established following a meshfree Galerkin approach for a solving of partial differential equation in solid mechanics problem and a Strain Gradient Stabilization (SGS) scheme is adopted in linear and nonlinear applications [2-4] for the elimination of zero-energy modes and the enhancement of coercivity. The SPG method in the gradient form recovers the locality of the solution that lacks in the integral form [1]. The discretized system of equation is consistently derived within the penalized meshfree Galerkin variational framework [2] and integrated using a direct nodal integration scheme. The SPG method is also applied to thermal analysis. Several numerical benchmarks and industrial applications are provided in this presentation to demonstrate the effectiveness and accuracy of the new method.

  • LS-DYNA ® Structured ALE (S-ALE) Solver

    Hao Chen (LSTC)

    A new Structured ALE solver is recently added into LS-DYNA. It targets to solve ALE problems with structured mesh. It supports all parallel versions of LS-DYNA, i.e., SMP, MPP and MPP Hybrid. The new solver generates structured ALE mesh automatically. The elements do not have to be of equal size. Instead, a user can define element spacing according to needs of the specific engineering problems. Listing all the elements and nodes used for ALE mesh in the input deck becomes unnecessary. Rather, we can simply define the mesh geometry by a number of control point pairs and let the automated mesh generator do the work. For larger ALE problems, the input deck size will be greatly reduced. The execution time on reading in keyword and writing out structured input decks are minimized. Also, changing mesh geometry becomes much simpler. The new S-ALE solver is easy to use, especially for users acquainted to the old generic ALE solver. The solver is automatically invoked with the generated structured mesh. This process is transparent to users. Most ALE keywords remain the same with exception of three new keywords. They are *ALE_STRUCTURED_MESH, *ALE_STRUCUTURED_MESH_CONTROL_POINTS and *ALE_STRUCTURED_MESH_REFINE.

  • LS-DYNA Performance Enhancement of Fan Blade Off Simulation on Cray XC40

    Ting-Ting Zhu (Cray Inc.), Jason Wang, Brian Wainscott (LSTC)

    This work uses LS-DYNA to enhance the performance of engine FEA simulation of fan blade off containment test on Cray XC40 supercomputers. Blade off containment test is a specific form of air safety test required by the Federal Aviation Administration and other safety agencies, which involves the intentional release of a fan blade when engine is running at full power. The released blade must be contained within the fan cases during the impact and imbalanced rotation. The simulation of fan blade off containment test is technically challenging and computationally intensive. To enhance the performance of fan blade off containment simulation, some improvements are made in surface to surface erosion contact in LS-DYNA version R8.0.0. In this study, the performance of fan blade off simulation using LS-DYNA version R8.0.0 is compared with that using LS-DYNA version R7.1.2 on a Cray XC40 supercomputer. In addition, the MPI communication patterns and load balance among the MPI processes in the fan blade off containment simulation is also analyzed. Finally, a very large model of fan blade off simulation with more than 80 million elements, which used to be a daunting task that took a modern MPP computer more than a month to complete, is carried out using LS-DYNA version R8.0.0 on the Cray XC40 computer.

  • LS-OPT ® Status and Outlook

    Nielen Stander and Anirban Basudhar (LSTC)

    Features added to the recently released LS-OPT Version 5.2 are discussed. An outlook of the next version, which includes Statistical Classification and Digital Image Correlation, is given.

  • Material Testing for Development and Calibration of Material models for Plastic Deformation and Failure

    Amos Gilat, Jeremy Seidt (The Ohio State University Department of Mechanical and Aerospace Engineering)

    Material testing at various, loading conditions, temperatures, and strain rates is used forstudying plastic deformation and failure of materials. The data from such tests is used for developing and calibrating material model that are utilized in numerical codes that are used for simulations of practical applications. The presentation will review experimental techniques used in such testing with emphasis on the integration of Digital Image Correlation (DIC) for measuring full-field deformations and the development of new tests. Of special interest is the testing needed for supporting the new deformation and failure model MAT224 in LS-DYNA ® . This material model is based on experimental determination of a failure surface that gives the equivalent plastic strain to failure as a function of stress triaxiality and the Lode parameter. It is done by testing specimens that are subjected to uniform and nonuniform states of stress and deformation and determining the failure state (deformation and stress) from matching the simulation of the test with the DIC and load measurements. Testing can be done at room temperature or, by using a special furnace, at elevated temperatures (up to 850C°). In addition, a new experimental setup in which full-field deformation and full-field temperature are measured simultaneously on the surface of a specimen during a tensile test is introduced. Results from testing specimens made of stainless steel show a significant temperature increase in the neck area in a quasi-static tension test. In most material models (e.g. Johnson Cook) the effect of strain hardening and temperature softening are uncoupled. The data that is typically used for determining the parameters in the models is obtained from experiments where strain hardening and temperature are coupled. The results from the new experimental setup can be used for uncoupling the effect of strain hardening and thermal softening during plastic deformation.

  • Metal Forming Automation using LS-OPT ®

    Krishna Chaitanya Kusupudi (Whirlpool Corporation)

    The principal objective of this paper is to demonstrate the Metal Forming automation setup using LS-OPT, in which CREO (CAD software), Hypermesh (FE pre-processor), LS-DYNA ® (FE Solver) and LS-PrePost ® (FE post- processor) are integrated. Metal Forming simulations are performed to check the formability of an intended geometry for various process settings like different draw bead retention forces, friction coefficient, blank dimensions, material properties, etc. In case of formability issues, geometry modifications are implemented in the necessary areas. Automation in any process will help to reduce the manual effort in running various combinations, saves time and gives more accurate results. Automation workflow is developed with reference to general metal forming simulation approach. To modify the geometries at concerned areas, CAD software is required. FE –preprocessor is required to create new mesh for modified geometry. LS-DYNA and LS-PrePost is used for solving and post processing respectively. In this work, Design of experiments (DOE) are performed to understand the effects of process parameters and critical dimensions of geometry on formability (Maximum thickness reduction, Crack elements, Risk of Crack elements, Wrinkles, etc). Critical process parameters and affecting areas in the geometry are indentified. Affecting areas are made parametric and significant process parameters which have significant effect on formability are considered. From data analysis of DOE results, a relation can be obtained between geometric dimensions, process parameters and formability responses. The knowledge obtained is shared with Design team and Tool makers. The Automation setup will be used for Optimization, Monte Carlo simulations, etc based on the requirement.

  • Model Set up and Analysis tools for Squeak and Rattle in LS-DYNA ®

    Thanassis Fokilidis (BETA CAE Systems SA), Jens Weber, Mehrdad Moridnejad (Volvo Cars)

    One of the most important quality aspects during the design process of a vehicle is the provided occupant comfort. Comfort in a vehicle is achieved, among others, through a quiet and durable interior, and through the elimination of Squeak and Rattle noises. A huge amount of different tests take place in laboratories in order to produce interior and exterior components that eliminate the occurrence of such undesirable phenomena. As a result, developing numerical models that explain and predict the behavior of a vehicle in Squeak and Rattle is important. The implementation of automated tools benefits analysts in setting up efficient and robust processes for accurate and straightforward CAE simulations. A simulation method that is used for the Squeak and Rattle numerical analysis is the E-LINE method which focuses on calculating and evaluating the relative displacement between two components in the time domain. Based on this method BETA CAE Systems in cooperation with Volvo Cars has developed a set of special tools in ANSA pre-processor and μETA post-processor for identifying the crucial areas, setting up the LS-DYNA E-LINE model definitions for them, and finally evaluating the corresponding LS-DYNA implicit results. The current paper dives deep in E-LINE method by showing both interior and exterior examples. In addition, it presents the BETA CAE Systems automated tools that offer a complete and effective solution in Squeak and Rattle analysis using LS-DYNA, minimizing simulation time consumption and human interaction.

  • Modeling and Simulations of Vehicular Impacts on W-Beam Rail with Raised Blockouts

    C. Silvestri Dobrovolny, N. Schulz, R.P. Bligh (Texas A&M Transportation Institute), C. Lindsey (Texas Department of Transportation)

    With recent changes about appropriate height for beam guardrail, there are more locations where rail height is below the recommended heights. Raising blockout on posts is a cost effective means to adjust rail height, however there is not any known analysis of how this might affects rail performance. The information compiled from this simulation study will enable the DOTs to decide whether raising wood blockouts on wood posts can be chosen as a cost effective mean to adjust rail height when below recommended value, without compromising the rail system performance. Researchers made use of pendulum testing facility to test raised 8-inch wood blockouts on wood posts embedded in soil. Force-displacement data was recorded and evaluated to understand the strength of raised blockout on wood post system and its capability to transmit impact forces into the soil. Results from pendulum testing were also employed to calibrate the behavior of a finite element model of a post and raised blockout system embedded in soil. The researchers detected real-world configurations of W-beam guardrail installations with wood blockouts on wood posts and identified those configurations for which the practice of raising wood blockouts on wood posts would need some additional investigation to assess system crashworthiness according to roadside safety standards. Three cases were identified for further evaluation through FEA analyses: 1) 31-inch MGS system, 4-inch pavement overlay in front of post and 4-inch raised blockouts on posts; 2) 273⁄4-inch rail system, 4-inch increased post embedment due to possible rail deficiency or posts settlement, and 4-inch raised blockouts on posts; 3) 273⁄4-inch rail system, 4-inch pavement overlay in front of post and 4-inch raised blockouts on posts. All cases indicate that the practice of raising wood blockouts on wood posts to maintain minimum rail height requirements appear to likely pass required roadside safety evaluation criteria.

  • Modeling Crack Propagation in Rubber

    Yoav Lev, Konstantin Volokh (Faculty of Civil and Environmental Engineering)

    Traditional bulk failure models are based on the approach of continuum damage mechanics involving internal variables which are difficult to measure and interpret in simple physical terms. Alternative approach was proposed by Volokh [1-5], in which the function of the strain energy density was limited. The limiter enforces saturation – the failure energy – in the strain energy function, which indicates the maximum amount of energy that can be stored and dissipated by an infinitesimal material volume. The limiter induces stress bounds in the constitutive equations automatically. The work presents a numerical implementation of the energy limiter theory using the LS-DYNA ® user defined material. This approach will be tested in few examples. First, the FE subroutine is checked against a simple uniaxial tension case that can be solved analytically. Next, we will model the Deegan-Petersan-Marder-Swinney (DPMS) experiments [6-7] for the dynamic fracture of rubber. These tests use biaxial pre-stretched rubber sheets which are pricked at a point. The pricking initiates a crack which runs along the sheet. We simulate these tests using the user defined subroutines of the hyper-elastic material models enhanced with energy limiters. The numerical results regarding the crack shape and speed are compared to the test observations.

  • Modeling Pre and Post Tensioned Concrete

    Leonard E Schwer (Schwer Engineering & Consulting Services)

    Modern concrete construction often uses pre-stressing of portions of the structure to improve the inherent tensile weakness of concrete. A compressive pre-stress is introduced into concrete using steel tendons loaded under tension. These tendons are either included in the concrete when the concrete is poured, i.e. pre-tension, or run through tubes that were cast in the concrete and then tensioned after the concrete is set, i.e. post-tensioned. Pre-tensioned components are often constructed off-site and shipped to the construction site. There are two types of post-tensioning: grouted or ungrouted. After the tendons are post-tensioned, the tubes containing the tendons may be back filled with grout (cement), this is primarily to minimize corrosion of the tendons. If grout is not used, then the tendons are typically lubricated, also to prevent corrosion.

  • Modeling Rebar in Reinforced Concrete for ALE Simulations

    Shih Kwang Tay, Jiing Koon Poon, Roger Chan (Ministry of Home Affairs)

    A constraint based method to couple rebar in reinforced concrete has been a popular method for Lagrangian simulations. However modeling rebar in Arbitrary Lagrangian-Euler (ALE) concrete has not been widely documented. This paper aims to investigate the effectiveness of the two constraint based keywords, *ALE_COUPLING_NODAL_CONSTRAINT and *CONSTRAINED_LAGRANGE_IN_SOLID found in LS-DYNA ® to couple beam elements in ALE concrete. This paper also explores the option of explicitly assigning steel rebar material within the ALE concrete using *INITIAL_VOLUME_FRACTION to create a Multi-Material Arbitrary Lagrangian-Euler (MM-ALE) simulation.

  • Mullins Effect in Rubber Part Two: Biaxial

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

    The formulation, testing and numerical study of the Mullins effect on rubber are presented. To demonstrate the Mullins effect experimentally, a biaxial test, inflation of a plane circular membrane, is used. Some experimental test data are shown. An approximate solution, a relation between the inflation pressure and the displacement at the center for the inflation of a plane circular membrane is presented. The test data and the approximate solution are used to determine the Mullins damage material constants. These constitution equations are implanted in LS-DYNA. The numerical results from LS-DYNA and analytical results are shown. They agree with one another.

  • Multi-physics applications for ground vehicle aerodynamics: structural thermal radiation coupled to CFD for a more accurate temperature prediction

    Facundo Del Pin, Art Shapiro, Iñaki Caldichoury, Rodrigo R. Paz, Julie Anton (LSTC)

    Thermal radiation is an important heat transfer mechanism which may greatly influence the mechanical behavior of structural parts of a vehicle when they are exposed to aerodynamic loads. This effect is even more evident in high performance vehicles where the engines are running at ever higher temperatures and the structure is built using lighter parts with less conventional materials. The radiated heat from the engine or exhaust system will increase the temperature in parts of the vehicle that are not directly in contact or even physically close. The increased temperature will soften the materials making it more prone to deformation in the presence of the fluid loads. The problem then requires the coupling of the radiation solver with a fluid mechanical solver to accurately predict the temperature of the mechanical part interacting with the air temperature and the deformation of that part when interacting with the air pressure. In the current work the first case will be studied. The conjugate heat transfer solver will be applied to the problem of predicting the temperature in parts of a vehicle when it is heated by radiation from the engine taking into account the cooling effect of the air.

  • Necking and Failure Simulation of Lead Material Using ALE and Mesh Free Methods in LS-DYNA ®

    Sunao Tokura (Tokura Simulation Research)

    After the Fukushima Daiichi nuclear disaster in 2011, the need of experiment to predict failure of the structures including pipes and vessels in nuclear power plant in case of large earthquake or tsunami has been increasing. However it is dangerous and expensive to perform such experiments using real structural material, e.g., 304 stainless steel as very large test facility is needed to cause realistic failure. Alternatively, the idea to use pure lead (100 % Pb) and lead alloy in the experiments has been proposed as alternatives of real materials used in nuclear power plant. Lead is ductile material and lead alloy involving antimony (Sb) is brittle material. So both ductile and brittle failure modes can be reproduced easily in laboratory tests using these materials. For the simulation of failure of the structures, ductility of lead should be modeled accurately. High ductility and large necking are observed in the tensile test of pure lead rod. In this paper, simulation of necking and failure of the lead rod tensile test is tried using ALE and mesh free techniques, i.e., EFG, SPH and SPG implemented in LS-DYNA in addition to the conventional Lagrangian FEM approach, and the results of the simulation are compared and discussed with the experimental result.

  • New Conjugate-Heat Transfer Solvers in the Compressible CESE Solver in LS-DYNA ®

    Grant O. Cook, Jr. and Zeng-Chan Zhang (Livermore Software Technology Corp.)

    Standard coupling methods for performing conjugate-heat transfer between a compressible flow and a structural thermal solver have been previously implemented in the LS-DYNA Conservation Element/ Solution Element (CESE) compressible flow solvers. Unfortunately, they do not conserve energy. One consequence of this in conjugate- heat transfer calculations is that the CESE solver’s conservation properties are compromised by the errors in the energy transferred at the interface between the structure and the fluid. And this error subsequently propagates to the interior of the fluid domain. In cases where a steady-state solution is sought, another consequence is that these energy errors may grow in time to the point that an incorrect steady state solution is computed. While one of the goals of these solvers is avoid non-physical and other erroneous solutions, it needs to be pointed out that the accuracy achieved is still a function of the fidelity of the computational mesh required to resolve the real solution. This is of particular concern in conjugate-heat transfer problems where the fluid boundary layer can be very thin, and large changes in the fluid variables in this fluid boundary layer are typical. Recently, we have implemented new energy-conservative methods for conjugate heat transfer involving compressible gases in the CESE conjugate-heat transfer solvers. These new solvers have been validated using an analytic test that has an initial singularity, and is thus quite challenging. The new method will be described, and discussed in the context of three types of solvers: 1) a fixed mesh Eulerian CESE solver coupled to a rigid structure, 2) moving mesh CESE FSI solvers, and 3) immersed-boundary method (IBM) CESE FSI solvers [1].

  • New XY-Plot interface in LS-PrePost ®

    Philip Ho, Luo Liangfeng, Wenhui Yu, Satish Pathy (LSTC)

    LS-PrePost, a pre and post processing program that compliments LS-DYNA ® , was lacking a good XY-Plotting tool. This paper illustrates and describes the new XY-PLOT which will make post-processing of results an efficient task. With the use of templates, plots from historical data can be generated quickly and compared with the current results. This paper discusses software architecture, its implementation and functionalities. It also discusses future work and direction.

  • Numerical Analysis of the Effects of Orthogonal Friction and Work Piece Misalignment during an AA5042 Cup Drawing Process

    Allen G. Mackey (Rigid Packaging Division)

    Wrinkle development during cup drawing operations is known to be highly dependent on many variables, including material anisotropy, tool geometry, process parameters, and tooling alignment. Weight reduction efforts in packaging industries have resulted in decreasing metal gauges, which exacerbates the formation of wrinkles. In this study, the Numisheet 2014 Benchmark 4 cup drawing process is used to investigate the effects of orthogonal friction on wrinkle formation during drawing of an AA5042 aluminum cup. The anisotropic material properties of rolled AA5042 aluminum alloy sheet are implemented as specified in Numisheet Benchmark 4 for accuracy. The coefficient of friction of the rolled sheet blank is examined orthogonally. The effects of work piece misalignment are investigated and compared to ideal results. Furthermore, the effect of orthogonal friction on the punch force is examined.

  • Numerical Study of an Interrupted Pulse Electromagnetic Expanding Ring Test

    J. Imbert, M. Worswick (University of Waterloo)

    Light weighting of vehicle structures will play an important part in the efforts to reduce fuel consumption and enable alternatively powered vehicles. The use of aluminum alloys and advanced high strength steels is one potential way of achieving significant weight reductions in the short to medium term. One of the main challenges posed by these materials is their relatively poor formability when compared with traditional automotive steel alloys. High speed forming has been studied as a way of increasing the formability of these alloys, with promising results. The lack of accurate constitutive data and models for these materials at the strain rates encountered in high speed forming, which can exceed 1,000 s -1 , presents a significant challenge to their implementation. Expanding ring tests have been used to measure the stress strain response at materials at high strain rates. In principle, these tests generate a uniaxial tensile stress state within the ring. If the driving force is known and the acceleration of the sample can be measured, then the stress and strain response of the material can be obtained. Significant challenges need to be overcome to obtain stress-strain data from this test, namely understanding the induced forces, Joule heating and the actual stress distribution in the ring. An interrupted pulse electromagnetic expanding ring test is being developed at the University of Waterloo to study the high rate behaviour of sheet metals. The test minimizes the induced forces generated on the sample and can produce free flight conditions. Given the complex nature of the phenomena and the speed at which they occur, numerical simulations play a critical role in analyzing the test. This paper presents the results of a multi-physics numerical analysis of the test based on a 3-D simulations using LS-DYNA ® . This analysis has been done to determine the effect of Joule heating and the driving force on the data generated by the test.

  • Predictive fracture modelling in crashworthiness: A discussion of the limits of shell discretized structures

    André Haufe, Filipe Andrade, Karl Schweizerhof (DYNAmore GmbH), Markus Feucht (Daimler AG), Herbert Klamser (Dr. Ing. h.c. F. Porsche AG), Daniel Riemensperger (Adam Opel AG)

    For many years shell formulations were used extensively in crashworthiness applications in order to predict deformations and even rupture of thin shell-like structures. From a general shell theory point of view there are probably no arguments to change this in the near future, unless none of the basic shell assumptions like using them for thin structures, having plane sections and only minor stresses in thickness direction, will be violated. However, especially if damage, localization and eventually rupture is regarded, the aforementioned assumptions limit the applicability and eventually the means to calibrate such models. For instance, if the rupture strain in biaxial loading is to be calibrated from experiments one can have straight biaxial tests or penetration tests (i.e. the Nakazima tests). For both setups classical shell elements deliver the same value for triaxiality of 2/3. While this is the correct solution for a biaxial test, the Nakazima test suffers from the fact that lateral stresses applied to the sheet are not being covered at all in classical shell formulations. Hence the stress triaxiality and the loading angle are not predicted accurate enough . Another well-known issue is the inability of 5-parameter shells to correctly predict a correct stress state in localization zones due to the violation of the plane section assumption. The present paper will describe such limitations in detail, focus on different calibration techniques and resulting drawbacks in the final crashworthiness application. Furthermore, available remedies will be presented and discussed.

  • Preference-based Topology Optimization of Body-in-white Structures for Crash and Static Loads

    Nikola Aulig, Stefan Menzel (Honda Research Institute Europe GmbH), Emily Nutwell (Ohio State University SIMCenter), Duane Detwiler (Honda R&D Americas)

    Topology optimization methods are increasingly applied tools for the design of lightweight structural concepts in the automotive design process. Ideally, topology optimization provides the optimum distribution of material within a user-defined design space for a given objective function. In the vehicle design process, two important objectives are to maximize stiffness of components for regular working conditions and to maximize energy absorption in exceptional loading conditions, for instance in crash events. For these objective functions, the Hybrid Cellular Automata algorithm devises efficient structures in case of the separated disciplines, by heuristically aiming for a uniform distribution of energy densities. Recently, it was demonstrated that a concurrent optimization of crash and static load cases can be performed by a linear weighting, in which the user preference is separated from the scaling of the internal energies. In this paper, the approach is applied to the practical example of a vehicle body-in-white design, which is optimized for multiple crash and linear static load cases. By comparing resulting internal energies of different load case settings we demonstrate that the hybrid cellular automata algorithm with scaled energy weighting is capable to find a very good trade-off solution within a single concurrent optimization run.

  • Quasi-Static Simulations using Implicit LS-DYNA ®

    Satish Pathy (LSTC), Thomas Borrvall (DYNAmore Nordic AB)

    Quasi-static tests that are part of the federal regulations such as FMVSS 216[1] and FMVSS 207/210[1] is predominantly simulated using LS-DYNA’s explicit solver. To be able to produce results in a reasonable time, mass-scaling and time-scaling are employed for these simulations, thereby the physics of the problem gets compromised. This paper demonstrates LS-DYNA’s Implicit capabilities to solve quasi-static problems in a reasonable amount of time, without compromising physics. Recent development and improvements to the implicit solver enables us to solve problems such as this, accurately and with a run turn-around time that is inside the reactionary period of the design community. Two popular tests – Roof-Crush and Seat-Pull tests were chosen for this exercise.

  • Recent Advances on Higher Order 27-node Hexahedral Element in LS-DYNA ®

    Hailong Teng (LSTC)

    This paper presents recent advances of second-order hexahedral element developed for explicit/implicit analysis in LS-DYNA. Several benchmark problems are studied to demonstrate the performance of the higher order element. The results obtained in modeling practical applications involving large deformations, nearly incompressible materials, severe distortions, bending, and contact-impact are also encouraging. Compared to standard 8-node brick element, the high order element is computationally expensive, but it is found to be competitive with other element types due to its much higher accuracy and higher convergence rate. Furthermore, high order element naturally contains the linear strain field and is capable of modeling bending and curved shape accurately without using either hourglass control or introducing incompatible modes. From a user viewpoint, what is gained is versatility in modeling a wide variety of geometries including three-dimensional or plate/shell geometries, and simplicity since only displacement degrees of freedom are used. This paper also present two techniques that transfer 8-node hexahedral model to higher order hexahedral model.

  • Recent Development of ICFD Pre and Post Processing in LS-PrePost ®

    Yu Wenhui, Zhang Zhanqun (Dalian Fukun Technology Corporation (China)), Philip W HO, Inaki Çaldichoury (LSTC)

    As the usage of ICFD module of LS-DYNA grow widely, the requirements of Pre and Post processing dedicated to LS-DYNA ICFD module become more and more urgent. Since early 2014, we’ve been working on ICFD post processing module in LS-PrePost with LS-DYNA developers. It’s now available in LS-PrePost in version 4.3. This new ICFD post processing module is object-oriented, works in both 2D and 3D case. Currently, following functions are included: Section Plane(line), ISO Surface (curve), Stream Line, Vector Plot, Level Set, Data Extraction(Point, Line), Line Integral Convolution(LIC), Attached/Separated Line, Vertex Core. The Pre Processing module of LS-DYNA ICFD module is also under design and development, aims to help traditional ICFD users transfer to LSDYNA ICFD application easily.

  • Recent Developments for Welding Simulations in LS-DYNA ® and LS-PrePost ®

    Mikael Schill, Anders Jernberg (DYNAmore Nordic AB), Thomas Klöppel (DYNAmore GmbH)

    The multi-physics capabilities of LS-DYNA makes it ideal for simulating the welding process where the mechanical and thermal physical regimes are combined to simulate the resulting part tolerance and residual stresses. Welding capabilities are continuously being added to LS-DYNA, e.g. the material models *MAT_CWM and *MAT_CWM_THERMAL which are tailored for CWM simulations. The CWM material models include e.g. ghost element and anneal functionality. However, the challenge when performing this type of simulations is not only related to the solver. The pre-processing quickly becomes a daunting task where the user needs to assign weld paths, weld power and clamping for several weld passes. To accommodate for this, a novel welding GUI has been added to LS-PrePost. The GUI includes e.g. a welding process planner, welding path selection using the graphical interface and welding heat source definition and visualization. Further, the welding process setup is written to an ASCII input file that can be combined with an optimizati on software to optimize the process with respect to e.g. welding deformations. This paper will present the recent developments in the mechanical and thermal solvers in LS-DYNA to accommodate for welding simulations. Also, the novel Welding GUI in LS-PrePost will be presented together with some application examples.

  • Recent Updates for the Heat Transfer Solver in LS-DYNA ® with focus on computational welding mechanics

    Thomas Klöppel (DYNAmore GmbH), Mikael Schill (DYNAmore Nordic AB), Tobias Loose (Ingenieurbüro Tobias Loose)

    Even though welding is a well-established production process in manufacturing industries and it has a significant influence on the finished geometry as well as on the material properties of the processed part, it is still often ne- glected in the virtual process chain. In this contribution novel developments for the heat transfer solver in LS- DYNA ® are presented, which are designed to close this gap in the virtual process chain. First of all, the new keyword *BOUNDARY_THERMAL_WELD_TRAJECTORY is presented that provides an easy and flexible input structure for a heat source moving along a prescribed and, possibly, geometrically complex path for thermo-mechanically coupled and thermal only simulations. As the user can choose from a list of pre-defined equivalent heat source models and this list is very easily extendable, the new feature is potentially applicable to all fusion welding processes. Due to high temperatures, high temperature gradients and very high temperature rates present in welding applica- tions, phase transformations in the microstructure of the material play a crucial role in the process. The new LS- DYNA material model *MAT_GENERALIZED_PHASE_CHANGE/#MAT_254 allows to distinguish between up to 24 different phases in the microstructure. For each of the possible phase transitions the user can choose from a list of generic and well-established transformation models. Therefore, the model is for example applicable to a wide range of steel and aluminium alloys. Transformation induced plasticity and strains as well as annealing effects have also been incorporated into the new material formulation.

  • Robust Modelling and Validation Analysis on the Raffles City Chongqing Project

    Zhi-Gang Liu, Shi-Chao Wu, Xiao Dong, Francois Lancelot, Li-Gang Zhu (Arup)

    Since 2012, Arup has been providing structural engineering services for all design stages of the development of the Raffles City Chongqing (RCCQ). This truly iconic mega-complex has been designed by the internationally acclaimed architect Moshe Safdie for the developers CapitalLand and Singbridge Holdings. Various structural schemes for the 300m-long sky deck atop the four 250m-high interior towers have been assessed using LS-DYNA [1]. Extensive nonlinear time-history analyses have been performed to simulate the behavior of several conservatory articulations and isolation solutions under extreme seismic conditions. Arup Shanghai has also been investigating innovative fuse/concrete outrigger solutions to meet the wind/seismic demands on the 350+m North Towers (T3N and T4N). A hybrid steel diagonal and concrete wall outrigger system (Hybrid OT wall) proved particularly promising. Compared with traditional steel designs, a Hybrid OT wall would simplify the design of the wall-to-mega-column connection while being significantly cheaper in cost. The development of these elements required extensive Finite Element analyses and physical testing. By deploying advanced LS-DYNA capabilities, structurally reliable and cost-efficient options have been identified and validated. This paper presents the validation process, analysis results and the design solutions that could achieve the architecturally ambitious, safe and sustainable design while providing significant cost savings.

  • Roof Rail Airbag Folding Technique in LS-PrePost ® Using DynFold Option

    Vijay Chidamber Deshpande (GM India – Tech Center), Wenyu Lian (General Motors Company), Amit Nair (LSTC)

    A requirement to reduce vehicle development timelines is making engineers strive to limit lead times in analytical simulations. Airbags play a crucial role in the passive safety crash analysis. Hence they need to be designed, developed and folded for CAE applications within a short span of time. Therefore a method/procedure to fold the airbag efficiently is of utmost importance. In this study the RRAB (Roof Rail AirBag) folding is carried out in LS-PrePost ® by DynFold option. It is purely a simulation based folding technique, which can be solved in LS-DYNA ® . In this paper we discuss in detail the RRAB folding process and tools/methods to make this effective. The objective here is to fold the RRAB to include modifications in the RRAB, efficiently and realistically using common analysis tools ( LS-DYNA & LS-PrePost), without exploring a third party tool , thus reducing the turnaround time.

  • Saving Calculation Time for Electromagnetic/ Mechanical/Thermal Coupled Simulations by Using the New EM 2D/3D Capabilities.

    Iñaki Çaldichoury, Pierre L‘Eplattenier (LSTC)

    LS-DYNA ® is a general purpose explicit and implicit finite element program used to analyse the non-linear dynamic response of three-dimensional solids and fluids. It is developed by Livermore Software Technology Corporation (LSTC). An electromagnetism (EM) module has been added to LS-DYNA for coupled mechanical/thermal/electromagnetic simulations, which have been extensively performed and benchmarked against experimental results for Magnetic Metal Forming (MMF) and Welding (MMW) applications. These simulations are done using a Finite Element Method (FEM) for the conductors coupled with a Boundary Element Method (BEM) for the surrounding air, hence avoiding the need of an air mesh. More recently, a 2D axisymmetric version of the electromagnetic solver was introduced for much faster simulations when the rotational invariance can be assumed. In many MMF and MMW applications though, the rotational invariance exists only for part of the geometry (typically the coil), but other parts (typically the workpiece or the die) may not have this symmetry, or at least not for the whole simulation time. In order to take advantage of the partial symmetry without limiting the geometry to fully symmetric cases, a coupling between 2D and 3D was introduced in the EM. The user can define the parts that can be solved in 2D and the ones which need to be solved in 3D and the solver will assume the rotational invariance only on the 2D parts, thus keeping the results accurate while significantly reducing the computation time. In this paper, the coupling method will be presented along with benchmarks with fully 3D and fully 2D simulations, comparing the accuracy of the results and the simulation times.

  • Sensitivity of Particle Size in Discrete Element Method to Particle Gas Method (DEM_PGM) Coupling in Underbody Blast Simulations

    Venkatesh Babu, Kumar Kulkarni, Sanjay Kankanalapalli, Ravi Thyagarajan (RDECOM, TARDEC)

    In this paper, the capability of two methods of modelling detonation of high explosives (HE) buried in soil viz., (1) coupled discrete element & particle gas methods (DEM-PGM) and (2) Arbitrary Lagrangian-Eulerian (ALE), are investigated. The ALE method of modeling the effects of buried charges in soil is well known and widely used in blast simulations today [6]. Due to high computational costs, inconsistent robustness and long run times, alternate modeling methods such as Smoothed Particle Hydrodynamics (SPH) [7] and DEM are gaining more traction. In all these methods, accuracy of the analysis relies not only on the fidelity of the soil and high explosive models but also on the robustness of fluid-structure interaction. These high-fidelity models are also useful in generating fast running models (FRM) useful for rapid generation of blast simulation results of acceptable accuracy [8-14]. In this paper, the effect of sensitivity of particle size in the performance of the DEM_PGM blast simulation is compared to that of the ALE blast simulation method. The main focus of this study is to understand the strengths of DEM_PGM and identify the limitations/strengths compared to the ALE method. Discrete Element Method (DEM) can model individual particle directly, and displace independently which is based on Cundall & Strack [1] A 2m x 2m x 2m volume is filled with ALE elements of 10mm side length. Three sets of ALE-equivalent DEM models are created using 3mm, 4mm and 5mm radius spheres. High explosive TNT is buried 50 mm deep in these three DEM soils and modeled as particles using PARTICLE_BLAST. Each of the 3 sets of DEM are analyzed for 100k, 250k, 500k and 750k TNT particles to understand the sensitivity of the DEM_PGM coupling and how the soil impulse, kinetic energy and translational energy are affected. This analysis has been extended to evaluate the TARDEC generic hull (GH) structural performance and compared to ALE method. Results show that DEM_PGM method reduces the computational time significantly when compared to the ALE method, and soil, a granular material by nature, can be well represented by fine particles in its discontinuous form.

  • Simulating Pellet and Clad Mechanical Interactions of Nuclear Fuel Rod for Pressure Water Reactors

    W. Zhao, D. Mitchell, R. Oelrich (Westinghouse Electric Company LLC)

    Pellet-cladding mechanical interaction (PCMI) is a potential failure mode leading to leaking fuel rods. Ever-increasing fuel duty and more demanding power maneuvers for adapting to alternative energy sources create new challenges for maintaining the high standard of fuel rod structural integrity. Towards meeting the new challenges, the paper describes an on-going effort in developing a coupled thermal-structural model suitable for simulating the complicated PCMI phenomena under normal operations, operational transients, and accident conditions. The models and various application examples are presented in the paper, including off-centered pellet, missing pellet surface, and pellet cracking. The work utilizes the commercial finite element software LS-DYNA ® (LS-DYNA is a registered trademark by Livermore Software Technology Corporation, 7374 Las Positas Road, Livermore, CA 94550, www.lstc.com.)

  • Simulation of Blast Load Reduction on Walls with Foamed Concrete Boards

    Yijian Shi, PhD (ZASA - Logan, Zodiac Aerospace)

    A foamed concrete board (FCB), often used as an insulation layer in structures, has been used to study blast attenuation. A LS-DYNA ® explicit solver chosen as a simulation tool reveals the physics of pressure waves, which transfer through materials, and internal stress in detail. The effectiveness of blast attenuation is measured by the reduction of peak pressure acting on a rigid wall (RW) that is immediately behind the FCB. According to the simulation results, the internal stress in FCB can reach much higher than its static strength under the blast loading. The internal stress is a function of not only material's failure stress and strain/deformation, but also its density, elastic modulus, plastic properties, internal speed, and acceleration. This observation might result in the difficulty to measure the internal stress or load, because load cells and strain gages traditionally only measure the strain or deformation, which can be converted to stress statically. The simulation results indicate that the higher the pressure of the blast than the strength of FCB, the higher the reduction for the peak pressure on RW is. On the contrary, if the pressure of a blast is lower than or about the strength of FCB, there is no reduction of the peak pressure on RW, rather than a significant increase. It seems that the increase is getting relatively larger as the pressure of the blast decreases.

  • Simulation of Wear Processes in LS-DYNA ®

    Thomas Borrvall, Anders Jernberg, Mikael Schill (DYNAmore Nordic AB), Liang Deng, Mats Oldenburg (Luleå University of Technology)

    Wear is an important life-limiting factor of hot forming tools and contributes to the high costs involved in the event of tool replacements and consequential lost production. It is therefore important to understand the complex mechanisms behind wear and to be able to assess the damage it leads to in order to improve tool design. By means of computer simulations and sophisticated wear laws this can be done in a virtual environment, and the aim of this paper is to demonstrate how LS-DYNA in combination with LS-PrePost can be used for this purpose. In version R9 of LS-DYNA, the keyword *CONTACT_ADD_WEAR associates wear laws with contact interfaces and allows for post-processing wear depth on associated surfaces. A goal has been to extend this to a fully-fledged simulation tool for complete wear processes. This includes not only performing a wear simulation, but also using the resulting wear data to modify geometries of interest, and then repeating the procedure for a sufficient number of cycles. It is demonstrated herein that this goal has in principle been reached.

  • Staged Construction of an API 650 Tank on a Settling Foundation

    Alexander Hay, Rudy du Preez, Roelof Minnaar (Advanced Structural Mechanics (Pty) Ltd)

    The staged construction of an API 650 tank is analyzed in this paper. The tank is considered to be erected on a foundation that is initially irregular, and which then experiences differential settlement during the course of construction. The consequence of foundation settlement and initial irregularity is that the final shape of the tank deviates from the intended cylindrical shape. During construction, each strake is added to the tank by positioning the (relatively flexible) rolled plate segments on the top edge of the strake below, while at the same time maintaining a fixed gap between vertical edges of adjacent plates. Once positioned, the vertical welds between plates are executed, and then the circumferential weld to the strake below. As such, the strakes can be considered to be placed on top of each other in a deformed (as dictated by the shape of the top edge of the strake below), but essentially stress-free manner. The structural response of the tank as a whole is also affected by a wind girder, which is moved up the tank in a sequence of temporary positions as the strakes are added, until it is fixed in its final position to the top strake of the tank. In its sequence of temporary locations, the wind girder not only provides stability to the tank shell, but is also used to assist in maintaining the cylindrical shape of the tank. Analysis was made possible by LS-DYNA ® 's staged construction functionality. In addition to the standard staged construction keywords, special provisions were required to enable sequential placement of the strakes in deformed but stress- and strain-free states. This was accomplished by running a sub-problem for each successive strake, where the displacement boundary conditions of the sub-problem enforced shell displacement continuity between the current strake and previous strake. Once the constructed shape of the current strake had been determined, it was transferred to the main model. The strake part was then activated in the main model for further analysis, as further foundation differential settlement occurred. Data transfer between the main model and sub-models was accomplished by means of custom Python scripts. The analyses allowed for the quantification of the effect of differential foundation settlement and initial foundation irregularity (while also including the effect of the wind girder) on the final constructed shape of the tank.

  • Statistical Energy Analysis for High Frequency Acoustic Analysis with LS-DYNA 

    Zhe Cui, Yun Huang (LSTC), Mhamed Souli (Lille University Laboratoire Mecanque de Lille), Tayeb Zeguar (Jaguar Land Rover Limited)

    The present work concerns about the new capability of LS-DYNA  in solving high frequency vibration and acoustic problem, using statistical energy analysis (SEA). As the frequency increases, the number of modes increases. As the result, the traditional numerical methods like finite element (FEM) and boundary element method (BEM) are difficult to use due to the large number elements requirement. It is more practical to consider average responses and their distribution over the structure, using a technique such as statistical energy analysis (SEA). In this paper, several numerical examples are investigated by SEA method with LS-DYNA  . The numerical results are in good agreement with other code.

  • Study on Ultra-high Electro-Magnetic Flux Generation using LS-DYNA ® Multi-Physics Capability

    Kunio Takekoshi (Terrabyte Co., Ltd.)

    Simulation results about two kinds of Electro-Magnetic Flux Generation Methods using LS-DYNA Multi-Physics capability are reported in this paper. It is revealed that the Burgess Model should be considered to model electrical conductivity as functions of relative volume as well as temperature, and that hourglass control type 6 should be used in order to precisely predict the generation of magnetic flux density and the deformation of coil for the methods.

  • Test and Numerical Simulation of Fixed Bollard and Removable Bollard Subjected to Vehicle Impact

    Choon-Keat ANG, Siew-Fern LIM, Jing-Yan KONG (Prostruct Consulting Pte Ltd)

    Crash bollard system is a type of physical security measures used to prevent forced entry by vehicles, as well as to provide adequate standoff distance between the target and a Vehicle-Borne Improvised Explosive Device (VBIED). Thus, the design of crash bollard system will have to take into consideration against high- energy vehicle impact and minimizing the post-impacted penetration. In this paper, fixed bollard and removable bollard systems are developed as inelastic transient finite element models. Both systems are simulated against a vehicle crash impact using LS-DYNA analysis tool. Full-scale vehicle crash tests have been carried out to validate the design and analysis.

  • Test and Simulation Comparison using Titanium Material Models based on MAT224

    Leyu Wang, Sean Haight, Kelly Carney, Paul DuBois, Cing-Dao Kan (George Mason University), Filippo Dicecca (Department of Aerospace Science and Technology), William Emmerling (Federal Aviation Administration)

    Titanium plate impact tests are simulated with *MAT_224, an elasto-visco-plastic material model in LS-DYNA ® with tabulated stress versus strain curves as well as tabulated strain rate and temperature dependency. The *MAT_224 input deck is built upon a series of tensile, shear and compression tests at different strain rates and temperatures conducted on a 0.5" commercial off-the-shelf titanium plate. The input of *MAT_224 is generated so that it predicts all the material property tests conducted on this plate. The 0.5" plate titanium *MAT_224 model is later used to simulate the 0.5" plate impact tests as well as impact tests of the 0.09", 0.14" and 0.25" plates. The predictive performance of the material model for each plate, including exit velocity, failure mode and the profile of the intrusion, are evaluated using the test results. It is shown that the 0.5" plate Ti-6Al-4V *MAT_224 predicts the impact test of the 0.5" titanium plate with great accuracy. However, the predictions for the impact tests of the 0.09", 0.14" and 0.25" plates, using the same material model, are not as accurate. All of these plates meet the specification of AMS-4911, but vary in yield stress from the 0.5” plate, as well as varying between states and material direction. The 0.5 inch plate is the most isotropic and as such most suited for a Von Mises material model. The other plates are from different lots, and clearly have had different processing to produce thinner material thickness. These differences within the same specification are thought to be the cause of the larger difference between test and simulation of the other plates.

  • The Influences of Tensile Test Directions and Yield Stress Selections on the FE Results of TBF1180 U-Channel

    Zhiguo Qin, Ching-Kuo Hsiung (General Motor Company)

    There is no standard on how to decide the yield stresses of Advanced High Strength Steel (AHSS) sheet materials. Is it necessary to decide the accurate yield stresses of AHSS materials in stamping FE simulations? A U-Channel part and TBF1180 material were selected to study this question.TBF1180 is a new third generation AHSS sheet metal. Three uniaxial tensile tests on 0 o (L), 45 o (D) and 90 o (T) directions with respect to the rolling direction are available for this material. All the three uniaxial tensile test stress-strain curves and three yield stresses for each tensile curve were used in FE simulations. The simulation results show that the different tensile curves and different yield stresses have the same Draw-Ins. The three tensile curves have limited differences in forming force (2% difference) and springbacks (about 5% difference). The three given yield stresses have very little forming force differences (less than 0.6%), but have big springback differences (up to 46%). Therefore yield stress has big influence on springbacks. What is the relationship between the yield stress and the springbacks and how to decide a yield stress for better formability and springbacks prediction need more study.

  • The LS-TaSCTM Multipoint Method for Constrained Topology Optimization

    Willem Roux (LSTC)

    The new multi-point constrained optimization scheme is for the constrained topology design of highly nonlinear structures for which analytical design sensitivity information is hard to compute. These highly nonlinear structures are designed for multiple load cases and multiple constraints, which means that the final design should have load paths for each load case as well as satisfy the constraints. This is done here by using two sets of variables: the local variables describing the part topology on the element level and the global variables consisting of the load case weights and part masses. The two sets of variables are treated differently in the design algorithm: the local variables are computed using a suitable method such as fully stressed design, while the values of the global variables satisfying the constraints are computed using numerical derivatives and mathematical programming.

  • The Recent Developments of the Metal Forming Modules in LS-PrePost ® (1) - The EZSetup and 3D-Drawbead Modules

    Quanqing Yan, Kevin Zhang, Philip Ho, Li Zhang, Yuzhong Xiao, Xinhai Zhu (LSTC)

    New functions have been continuously implemented into LS-PrePost to enhance the metal forming analysis with LS-DYNA. In this paper, two important updates – the EZSetup and the 3D Drawbead - will be introduced. The EZSetup module, which has been used in the production simulations, is further enhanced now by incorporating springback compensation, lancing operation as well as the multi-stage simulation setup with unlimited sets of processes and tools. The 3D Drawbead module, as a newly added metal forming module, can be used to generate the mesh of the real beads given the corresponding line beads. Therefore the accurate simulation with the real beads can be performed readily when the feasibility analysis with the line beads is completed. These modules will be under constant development to meet the requirement of our metal forming users.

  • The recent developments of the metal forming modules in LS-PrePost ® (2) - The Die System Module

    Chunjie Zhang, Philip Ho, Yuzhong Xiao, Li Zhang, Xinhai Zhu (LSTC)

    New functions have been continuously implemented into LS-PrePost for users to set up the metal forming simulations with LS-DYNA ® . In this paper, the newly added Die System Module will be briefly introduced. Given the designed part shape, the Die System Module can be used to create the forming tool for the subsequent simulation setup in the EZSetup module of LS-PrePost. The functions that would be needed in the tool creating process are, e.g. flange separation, part tipping, flange unfolding, binder and addendum generation, are provided by the Die System Module in a step-by-step manner. This new module will be under constant development to meet the requirements of our metal forming users.

  • The Significance of the Production Process of FRP Parts for the Performance in Crashworthiness

    Christian Liebold, Andrea Erhart, André Haufe (DYNAmore GmbH)

    As there is a trend in the automotive industry towards using FRP composites for reducing the weight of vehicles, adequate simulation tools to effectively and accurately predict the structural response of composite structures in crashworthiness are needed. Due to the manufacturing induced fiber orientation, which is particularly for short fiber reinforced composites locally varying, the pointwise mechanical behavior of (S)FRP is a priori unknown and accordingly the prediction of the mechanical behavior of FRP-components is challenging. A promising approach is an analysis that covers the complete process chain from the molding process to the crashworthiness modelling: fiber orientation are determined by process simulation and transferred to the structural analysis model through a data-mapper. Using this information, the local anisotropic material behavior can be determined by means of a homogenization procedure and used for the structural analysis. In this paper two recently implemented possibilities for LS-DYNA ® are presented. For the first approach, the data-mapper “DYNAmap” transfers the fiber orientation tensor, which is evaluated in a MoldFlow ® simulation, to the structural analysis model. Using a recently developed constitutive model, pointwise effective anisotropic material properties for this composite are automatically determined and used for the structural simulation. This calculation of homogenized macroscopic properties is done in two steps: At first, effective properties of an associated “pseudo uni-directional” composite are determined by analytical homogenization (see Dvorak [2013]). In a second step an orientation averaging of these uni-directional properties in accordance with the mapped local fiber orientation is carried out; see Advani & Tucker [1987]. While for elasticity the determination of effective properties is done only once in a preprocessing step, for considering inelastic behavior, an update of the material properties during the simulation is necessary from time to time. Alternatively, DYNAmap provides the possibility to perform a homogenization for evaluating the pointwise effective anisotropic elastic stiffness parameters and to transfer the resulting local stiffness values to *MAT_ANISOTROPIC_ELASTIC_PLASTIC. This approach can be extended to an anisotropic elasto-plasticity model with rate dependent hardening. For this purpose, the user has to provide the appropriate Lankford-coefficients and hardening curves, while the mapper provides the dominant fiber orientation pointwise. Damage and failure can be added through *MAT_ADD_EROSION. Within the presentation applications of both approaches will be discussed and compared.

  • Thermal Structural Forming & Manufacturing Simulation of Carbon and Glass Fiber Reinforced Plastics Composites

    Ala Tabiei and Raguram Murugesan (University of Cincinnati)

    The forming process of composites is presented in this paper. A computational micro-mechanical model of loosely woven fabric is presented and used to simulate the thermos-forming of woven fabric composites. The *PART_COMPOSITE is utilized to represent the resin and woven fabric as integration points through the thickness of the ply. The model, which is incorporated in LS-DYNA ® , accounts for the fiber reorientation, trellis mechanism of the yarn and viscoelasticity of the fibers. The resin material model used is a temperature dependent elastic plastic thermal. The behavior of the woven fabric is studied with the classical hemispherical draping and cantilever bending simulations which are validated against experiments. The thermal structural analysis of the carbon/epoxy woven fabric composites is carried out through the bias extension and thermo-forming simulations. This method of incorporating the resin within integration points of the fabric proved satisfactory as the simulation results were in good agreement with the experiment. The proposed model and simulation techniques would be an efficient tool in evaluating factors related to the composite manufacturing process.

  • Use of Data Reduction Methods for Robust Optimization

    Dominik Borsotto, Lennart Jansen, Robin Strickstrock, Clemens-August Thole (SIDACT GmbH)

    Data reduction methods like principle component analysis, singular value decomposition and independent component analysis methods allow analyzing huge sets of data. Applied to simulation results they allow the characterization of major trends in the variation of these results. For the public Chevrolet Silverado example all thicknesses are initially varied independent of each other among a number of simulation results and its correlations are computed to the variation of the behavior of the firewall. The behavior of the firewall is approximated using data reduction methods. It turns out, that the variation of the firewall can be characterized by one basic deformation mode. The thickness variation of a part may show strong or weak correlation to the behavior of this deformation mode. In several steps now, the sensitivity analysis is repeated using only those parts for thickness variation, which had a strong correlation in the previous step. Finally it turns out, that the thicknesses of the longitudinal rails as well as certain bifurcation behavior of the longitudinal are responsible for this variation mode of the firewall.

  • Using Tabulated Experimental Data to Drive an Orthotropic Elasto-Plastic Three-Dimensional Model for Impact Analysis

    C. Hoffarth, B. Khaled, S. D. Rajan (Arizona State University, Tempe), R. Goldberg, K. Carney (NASA-GRC, Cleveland), Gunther Blankenhorn (LSTC)

    An orthotropic elasto-plastic-damage three-dimensional model with tabulated input has been developed to analyze the impact response of composite materials. The theory has been implemented as MAT 213 into a tailored version of LS-DYNA ® being developed under a joint effort of the FAA and NASA and has the following features: (a) the theory addresses any composite architecture that can be experimentally characterized as an orthotropic material and includes rate and temperature sensitivities, (b) the formulation is applicable for solid as well as shell element implementations and utilizes input data in a tabulated form directly from processed experimental data, (c) deformation and damage mechanics are both accounted for within the material model, (d) failure criteria are established that are functions of strain and amage parameters, and mesh size dependence is included, and (e) the theory can beefficiently implemented into a commercial code for both sequential and parallel executions. The salient features of the theory as implemented in LS-DYNA are illustrated using a widely used composite – the T800S/3900-2B[P2352W-19] BMS8-276 Rev-H-Unitape fiber/resin unidirectional composite. First, the experimental tests to characterize the deformation, damage and failure parameters in the material behavior are discussed. Second, the MAT213 input model and implementation details are presented with particular attention given to procedures that have been incorporated to ensure that the yield surfaces in the rate and temperature dependent plasticity model are convex. Finally, the paper concludes with a validation test designed to test the stability, accuracy and efficiency of the implemented model.

  • Validating Innovative Design Solutions - Analysis of the Gerald Desmond Bridge Replacement

    Francois Lancelot, Dong-Ling Li, Mark Nelson, Matt Carter (Arup)

    In 2011, the Port of Long-Beach, in collaboration with Caltrans and LA Metro, awarded the Design and Build contract for the replacement of the deteriorating Gerald Desmond Bridge to SFI Construction (Schimmick / FCC /Impregilo joint-venture). Arup had been lead designer for SFI’s tender proposal, providing structural andgeotechnical engineering, traffic operations analysis, lighting design and civil engineering services. Arup designed an elegant mono-pole stayed-cable solution that met all the project requirements while providing dramatic cost- savings to the Client. The team’s innovative solution earned the judges’ highest ratings for both technical design and price and ultimately won the job. The deployment of advanced LS-DYNA ® analysis capabilities was instrumental in assessing the structural options against the stringent project requirements. The extreme seismic demands of the 1000-year Safety Evaluation Event (SEE) could be addressed by isolating, by means of viscous dampers, the Main Bridge deck from the Towers and by introducing a ground-breaking approach for the design of the ductile hollow-section columns. These innovative solutions, among other particular features of the bridge, required detailed Finite Element modelling and validation through explicit nonlinear time-history analysis. This paper presents some of the key modelling techniques and analyses results that contributed to the successful development of this new landmark.

  • Validation of the ALE Methodology by Comparison with the Experimental Data Obtained from a Sloshing Tank

    Alexander L. Kozak, Payman Khalili Tehrani, T. Eric Abrahamson, Alexander V. Krimotat (SC Solutions, Inc., Sunnyvale)

    Arbitrary Lagrangian – Eulerian (ALE) methodology has been used in Fluid - Structure Interaction (FSI) analyses with LS-DYNA ® for a variety of problems. Validation of ALE solutions by comparison with experimental data provides assurance that the solutions represent the physical world. A water tank under horizontal harmonic excitation tested by O. M. Faltinsen and O. F. Rognebakke [1] is used for validation. The experimental time histories of water surface motion are compared to those obtained from the ALE solution. Both free surface sloshing and the wave impact with the roof are analyzed and compared. The LS-DYNA analytical results match the experimental data very well. Different ALE formulations and mesh densities are explored and their respective solution times are compared. In addition, the ALE and experimental maximum wave heights are compared with the prediction by closed form solutions.

  • Vehicle Seat Bottom Cushion Clip Force Study for FMVSS No. 207 Requirements

    Jaehyuk Jang (CAE Body Structure Systems General Motors)

    Federal Motor Vehicle Safety Standard (FMVSS) No. 207, "Seating Systems," establishes requirements for seats, their attachment assemblies, and their installation, to support robust design for seat attachment to Body under vehicle impact. General Motors has been continuously improving the CAE procedure for this Safety Standard. This presentation introduces a CAE simulation method that was specifically developed to accurately simulate a deformational behavior of the plastic clip that is installed at seat bottom cushion attachments to the vehicle floor. The focus of this study was on how to precisely predict the separation point in load, if it occurs, so that the design of the attachment can be updated to ensure the success of the respective test. This paper discusses a customized model setup for the clip removal force measurement using *DATABASE_JNTFORC with separation criteria at the latch that successfully enables the model results to match the empirical force data at separation. In this newly developed method, an interface management between three-dimensional seat foam and one-dimensional wireframe elements embedded inside the foam without depending on rigid links is introduced. This method uses *CONSTRAINED_LAGRANGE_IN_SOLID keyword that is primarily intended for modeling Fluid-Structure Interaction (FSI). Its CAE simulation process flow from benchmarking up to a proof run to demonstrate a correlation to its empirical data is also introduced.

  • Vibration Analysis of a Compressor Blade at High Temperature

    Devon Downes, Manouchehr Nejad Ensan (Aerospace Portfolio, National Research Council)

    This paper summarizes the vibration analysis of a stage two T56 compressor blade at high temperature. First, an implicit thermal analysis was performed to elevate the blade’s temperature to 700°C. The output parameters of this analysis were then used as a “pre-stress” condition of the blade prior to starting the vibration analysis. Velocity results obtained using numerical simulations were compared to experimental results. The simulation was able to capture the peak velocity within 10% of the experimental result. This analysis was also used to estimate the peak equivalent stress location under combined vibration and high temperature loading. Increased stress was found around the base of the blade where the physical geometry changed abruptly and where the loading was applied.

  • Virtual ROPS and FOPS Testing on Agricultural Tractors According to OECD Standard Code 4 and 10

    D. Hailoua Blanco, C. Martin, A. Ortalda (EnginSoft S.p.A)

    The Roll Over Protection Structure (ROPS) and Falling Object Protective Structure (FOPS) are key safety features in agricultural and forestry tractors in order to avoid or limit risks to the driver in case of roll over or falling objects during normal use. The Organization for Economic Co-operation and Development (OECD) in an effort to improve operator’s safety in Agricultural and Forestry Tractors has set up harmonized testing procedures for ROPS and FOPS systems. The current OECD Codes for tractors relate to several features of performance. In particular, Code 4 and 10 are related to the strength of protective structure in case of roll over and falling objects, respectively [1-2]. On the one hand, Code 4 foresees a sequence of loadings that the protection system has to withstand until the prescribed energy or force is satisfied. The magnitude of the required energy and forces depend upon the reference mass of the tractor. In addition to successfully resist the loading sequence, the ROPS has to guarantee a clearance zone during any part of the tests around the seat index point (SIP), where the operator is placed. By fulfilling all these conditions, the structure is classed as a roll-over protective structure in accordance with the OECD Code 4. On the other hand, Code 10 implies a series of object drop tests from a height to develop a specific energy. Likewise, the clearance zone shall not be entered by any part of the protective assembly or the impacting object itself to pass the test. In light of the complex testing scenarios, numerical simulations with LS-DYNA ® were carried out to virtually assess the performance of a ROPS and FOPS system designed by the Italian tractor manufacturer. As a matter of fact, ROPS and FOPS simulations turned out to be very useful to understand the behavior of the protection system subjected to complex loading and get valuable insights into performance. The main goal of the simulations was to virtually test the tractor according to the Code 4 and 10 prior to official test approval and, if necessary, introduce the necessary structural changes in order to successfully pass the ROPS and FOPS tests.

  • WorldSID 5% Dummy Model Development in Cooperation with German Automotive Industry

    Sebastian Stahlschmidt, George Dumitru, Yupeng Huang, Ulrich Franz (DYNAmore GmbH)

    The paper describes the methodology used to develop the PDB and FAT Dummy models. The models are used by almost all OEMs and restraint system suppliers to enhance the passive safety performance of their vehicles. Nevertheless, the PDB is still launching new projects to further enhance the predictability of the ES-2, ES-2re, BioRID-II and WorldSID models. This paper presents the current state of a new project to develop the WorldSID 5% model. The project is still in definition phase but there are first results available of the Modell. The test database generated to build and validate the models is described as well as the performance of the current development release.