http://www.dynalook.com daily 1 2009-03-06T17:29:14Z http://www.dynalook.com/european-conf-2001/36.pdf LS-DYNA is available on a wide variety of computer platforms, ranging from commonplace personal computers to sophisticated vector processors to high-performance scalable servers. This presentation will review historical LS-DYNA performance and look forward to what can be expected in the next generation of computer platforms. The capability of available computer platforms always has a bearing on what type of simulations LS-DYNA end users can run. In the past, departmental machines such as DEC VAX servers provided many computing cycles to users. Porting of the code to Cray vector machines made overnight full-car crash simulations practical. Models grew larger but could still be run overnight as machine speeds increased and SMP parallel versions became available. At the same time, UNIX workstations increased in capability to the point where many sophisticated simulations could be run on desktop machines. Most recently, significant advances in LS-DYNA and computer hardware have taken place in two different areas: scalable servers, and machines based on low-cost processors. The advances are being driven by the growing acceptance of the MPI version of LS-DYNA, the level of performance available from low-cost commodity processors, and the level of performance available from high-performance processors available in scalable systems. Current performance examples and trends in microprocessor improvement can be used to give users guidance on what levels of LS-DYNA performance will be attainable in the next few years. No publisher admin 2010-04-08T09:48:12Z File http://www.dynalook.com/european-conf-2001/51.pdf In order to yield significant added value, computer model need to reach to a level of reliability that enables decisions, which are only based on simulation results. Airbag deployment is highly non linear and non reproducible. Scatter in all system properties and boundary conditions also cause scatter in the performance of the system. The aim of this paper is to use stochastic simulation approach to include this natural scatter into the computer models. This allows evaluation of the performance scatter and thus an assessment of reliability and quality of the simulated system. Stochastic simulation can be used for system improvement, which offers a further application tool for system optimisation. The problem is not to find optimum solution in a mathematical sense, but to develop sufficiently good and especially robust solutions for real world situations. In this paper stochastic approach will be introduced and applied to the side airbag deployment. No publisher admin 2010-04-08T09:56:02Z File http://www.dynalook.com/european-conf-2001/53.pdf Stiffened plates and curved panels are widely used as primary structural elements in aerospace, marine and civil engineering. Their stable postbuckling behavior and their capability to sustain loads far in excess of their initial buckling loads may lead to considerable weight savings, if their postbuckling strength is fully utilized and possible fatigue problems are eliminated. In the presence of large deflections, bifurcations, load and displacement limit points, the analysis of arbitrary anisotropic shells requires the adoption of incremental and iterative procedures capable of tracing the complete load- displacement path. Although the true response is dynamic in nature, a fully static solution is followed in most cases. Stiffened panels loaded in axial compression were extensively studied and employed in aeronautical structures in the thirties, forties and beyond, yielding the effective width. In the last decades, the trend to optimize the design shear panels, and the employment of composites and higher strength metals, has led to similar required relative stiffnesses in both civil and aeronautical engineering. The civil engineers employ stiffer flanges in order to improve the postbuckling strength of the web and the aeronautical engineers decrease the relative flange cross-sectional area in order to save weight. The nonlinear analysis of shells requires the efficient blend of finite element technology and path-following techniques. Due to the increased computational effort of the incremental and iterative solution process, it is imperative to obtain the structural response by simple, inexpensive and accurate finite elements. In this paper the postbuckling performance of composite shells using computer code LS-DYNA is analysed. No publisher admin 2010-04-08T09:57:05Z File http://www.dynalook.com/european-conf-2001/64.pdf The purpose of a detonation chamber is to ensure vapor and fragment containment during the destruction of explosive munitions. The toxic vapors generated by the detonation can be vented into a filtration unit. Compared to free air detonations, the use of a detonation chamber reduces the environmental impact of munitions destruction. The manufacture and testing of a detonation chambers is time consuming and expensive. At present, new designs are mainly based on experience with previous designs and rough estimates. A more accurate and reliable method for predicting a chambers performance would therefore be a significant aid in the design process. This paper considers the most straightforward method for predicting the performance of a chamber design, which is to simulate a munitions detonation in the chamber. The simulation is accomplished using LS- DYNA's multi-material Eulerian methods. No publisher admin 2010-04-08T10:08:29Z File http://www.dynalook.com/european-conf-2001/PAULDUBOIS.pdf No publisher admin 2010-04-08T10:14:42Z File http://www.dynalook.com/european-conf-2001/NUMERICAL-SIMULATION-OF-THE-WOOD-RESPONSE-TO-THE.pdf The experiments where the freely supported spruce beams have been loaded by the detonation of an explosive charge have been evaluated using of the numerical simulation. The explicit Lagrangean finite element code LS DYNA 3D has been used to analyse the beam response. The wood has been considered as global orthotropic linear elastic material with a material damage. The material damage has been described by the strain at the wood failure. This simple material model seems be better than the Tsai - Wu model widely used in another numerical simulations. Spruce wood , beam , material damage, explosive loading, finite element , numerical analysis Wood is an anisotropic cellular material such as honeycombs, metal ring systems, polymeric foams and some others . These materials are very convenient for the design of impact energy absorbers and as core materials in lightweight structures. Their behaviour under static loading is well summarised in the book (Gibson and Ashby 1988). Wood in particular has also been used as a protective material for high velocity impact events for many centuries (Johnson 1986a, 1986 b) and is very often used as an impact energy absorbing material at the design of the transportation flasks for nuclear fuel etc. There have been only a few systematic studies of the behaviour of wood under high rates of loading following from some impact events (Johnson 1986a). Recently the extensive impact test data have been obtained for some wood species (Reid and Peng 1997, Harrigan et al. 1998) . These data have been used for the development of the models of the macro – deformation and micro – deformation modes resulting from the dynamic uniaxial compression at the specimen impact. The present paper focuses on the other kind of the dynamic loading which is the effect of the detonating explosive. The study of this problem has some practical applications . Wood may be successfully used as a part of a structure which should absorbed most of the energy of the mine explosion etc. It is obvious that there is a variety of different arrangements, kind of wood, thickness of wood layer etc. In order to reduce the number of expensive experiments some reliable numerical simulation is necessary. The present paper deals with the problem of such numerical analysis using of the finite element code LS DYNA 3D. No publisher mike 2009-03-26T16:51:03Z File http://www.dynalook.com/european-conf-2001/IN-BORE-BEHAVIOUR-OF-LARGE-CALIBRE-ARMOUR-PIERCING.pdf The efficiency of large calibre armour piercing fin stabilised discarding sabot projectiles (APFDS) is primarily linked to their terminal ballistics performances. But other parameters, such as its accuracy and its yaw at the impact have also a large influence on the performance. These two parameters magnitude, as well as the survivability of the projectile during the launch phase are greatly affected by the interaction between the projectile and the gun, also known as the “balloting”. Nowadays, the accurate description of the rod free flight has been made possible thanks to Computational Fluid Dynamics calculations, allowing to predict the flight quality or the retardation, and back calculation of initial disturbances of an unexpectedly odd shot. But this situation is not true for the early moments of the firing sequence, i.e. the projectile inbore travel and the sabot separation. For the latter, a long way to go remains. But, in the field of projectiles in-bore behaviour, a lot of works have been performed, using different numerical methods, which allowed scientists to make significant progress. This paper describes some of the works performed in the Giat Industries Weapon and Ammunition Systems Division (DSAM), whose purpose was to understand how the interactions between the weapon and the projectile could affect its mechanical behaviour and its muzzle exit conditions. No publisher mike 2009-03-26T16:51:00Z File http://www.dynalook.com/european-conf-2001/some-examples-of-energetic-material-modelling-with.pdf SNPE is using DYNA codes for more 15 years for characterisation and modelling of energetic materials : high explosives, solid propellants, gun propellants and pyrotechnic systems for functioning, safety, survivability and vulnerability analysis in space and defence applications. This paper presents some examples of the use of LSDYNA in the field of solid mechanics, fluid mechanics and detonics. The first example concerns the development of a constitutive model for a cast PBX. A general dynamic viscoelastic model developed in LSDYNA is used to analyse Split Hopkinson Pressure Bar (adapted for soft materials characterisation) experiments, reverse Taylor test instrumented by high speed framing camera and VISAR system. A postprocessing variable implemented is used for analysing dynamic failure in dynamic Brazilian tests performed with SHPB system. Two others short examples are given : functioning of a pyrotechnic system separation in space application and LSDYNA/Euler simulation of the interaction of blast waves with explosive charges in sympathetic detonation phenomena. No publisher mike 2009-03-26T16:39:10Z File http://www.dynalook.com/european-conf-2001/characterization-and-component-level-correlation.pdf Polyurethane (PU) foams are one of the most widely used countermeasures for head impact protection. For accurate prediction of the head injury parameters, studies were conducted to establish a reliable LS-DYNA[1] material model to characterize PU foams. A 5.0pcf (80.09 g/l) PU foam was characterized using four different material models available in LS-DYNA for simulating foams, namely MAT_LOW_DENSITY_FOAM (MAT57), MAT_CRUSHABLE_FOAM (MAT63), MAT_BILKHU_DUBOIS_FOAM (MAT75) and MAT_FU_CHANG_FOAM (MAT83)[1]. The Finite Element Analysis (FEA) results were compared with the physical test results. The FEA material model resulting from the characterization procedure was validated using a component level, head impact correlation study. A simple side rail section was extruded about the SR1 target point and was impacted with a standard headform at an initial velocity of 15mph. Three different cases were investigated; baseline model with body-in-white (BIW) only, BIW with 18mm foam and BIW with 22mm foam. The Head Injury Criterion (HIC)[2] and acceleration curves from the simulation were compared with the physical tests. No publisher mike 2009-03-26T16:48:33Z File http://www.dynalook.com/european-conf-2001/finite-element-analysis-of-ductile-failure-in.pdf Notched specimens of the structural steel Weldox 460 E have been tested at high strain rates in a Split Hopkinson Tension Bar. The aim was to study the combined effects of strain rate and stress triaxiality on the strength and ductility of the material. It is further considered important to obtain experimental data that may be used in validation of constitutive relations and fracture criteria. The force and elongation of the specimens were measured continuously by strain gauges on the half-bars, while the true fracture strain was calculated based on measurements of the fracture area. Optical recordings of the notch deformation were obtained using a digital high-speed camera system. Using image processing of the digital images, it was possible to estimate the true strain versus time at the minimum cross-section in the specimen. The ductility of the material was found to depend considerably on the stress triaxiality. Non-linear finite element analyses of the notched tensile specimens at high strain rates have been carried out using LS-DYNA. A computational material model including viscoplasticity and ductile damage has been implemented in LS-DYNA and determined for Weldox 460 E steel. The aim of the numerical simulations was to assess the validity of the material model by comparison with the available experimental results. No publisher mike 2009-03-26T16:48:47Z File http://www.dynalook.com/european-conf-2001/web-centric-ls-dyna.pdf The Internet has changed the way business is done – and High Performance Computing (HPC) is no exception. Many firms have launched “dot-com” software to facilitate B2B collaboration, outsource jobs, provide engineering services, or exchange data with suppliers and partners. Recently, however, hundreds of dot-coms have failed, and many high-tech companies have laid off thousands of workers. Now what? The term ASP (application service provider) has become popular in the past several years. ASPs deliver and manage applications and services remotely for multiple users – either through the Internet or a private network. An ASP owns the relationship with the end-user customer. Security tops the list of customers’ concerns. Hundreds of ASPs have sprung up, but most of these (e.g., Exodus, Qwest, Corio, EDS, Applicast, etc.) host computing services for commercial applications rather than technical ones. This paper introduces some basic concepts in portal supercomputing and ASPs, and suggests future directions LSTC and its worldwide distributors may wish to consider to web-enable LS-DYNA to make it accessible to a wider engineering community. No publisher mike 2009-03-26T16:39:11Z File http://www.dynalook.com/european-conf-2001/ls-dyna-performance-on-ultrasparctm-iii-servers.pdf Sun Microsystems recently announced a new line of high-performance Sun FireTM Midframe servers and Sun BladeTM 1000 workstations based on 750-MHz UltraSPARC-III microprocessors. These new computers offer exceptional performance for numerically intensive MCAE applications at reasonable prices. This paper presents single- and multi-processor performance and scalability results of LS-DYNA running on these systems. Results of both OpenMP and MPI binaries are compared to those of existing server platforms. Scalability and performance results are presented for the OpenMP binary that has been built with Sun's native OpenMP compiler extension. Comparisons with a previous version using libraries from KAI show significant improvements both in the absolute execution time and the scalability. The MPI executable tuned for the new Sun Fire server resulted in a 40-60% improvement in execution time over the entire range of processor counts. No publisher mike 2009-03-26T16:42:32Z File http://www.dynalook.com/european-conf-2001/estimation-of-the-transverse-crush-resistance-of-a.pdf Ocean-going vessels are very complex structures, and can have displacements ranging from hundreds to tens of thousands of tons. In the case of bulk carriers and tankers, this can be as much as half-a-million tons. When in motion, they can possess very large amounts of kinetic energy even if their velocities are small. They therefore have the potential to cause serious damage in case they are involved in a collision. Ships moving in ports or harbours often move in limited space and there is always the possibility that an accidental collision may occur, albeit at a low velocity. If either the striking or struck ship carries sensitive or hazardous materials then the consequences of a collision may be far more serious than that consisting simply of structural damage to either ship. One way of reducing potential damage to ships carrying such cargo is to restrict the travel velocities of approaching ships to some limiting values. The reliable estimation of such velocities needs as a minimum a knowledge of the crush characteristics of at least the target vessel, and preferably that of the striking vessel too. The situation addressed in this paper is one where a moored vessel, a T23 frigate, is struck normally by a similar moving vessel. It is required to estimate the crush characteristics of the struck vessel around the chosen impact location. A knowledge of the crush characteristics can then be used to derive limiting approach velocities in order to minimise damage, intrusion, etc. in the struck vessel. A three-dimensional mesh of the struck section of the moored ship has been modelled using finite elements. The implicit algorithms in LS-DYNA3D(1) were used to simulate the crushing of this ship section. The paper presents the method of analysis and the derived crush characteristic, which is then used to estimate limiting velocities for an approaching vessel No publisher mike 2009-03-26T16:48:42Z File http://www.dynalook.com/european-conf-2001/development-and-validation-of-a-us-side-impact.pdf Automotive safety regulations vary in different parts of the world. Dynamic side impact regulations, for example, are different than the ones in Europe. United States National Highway Traffic Safety Administration (NHTSA) and the European Union (EU) have each produced their own distinct testing procedures such as different deformable barriers, impact configurations and anthropomorphic test devices (dummies). Although both test procedures have the same final objective, estimate occupant responses in side impact, they differ greatly in execution. One of the main differences in testing is the Moving Deformable Barrier (MDB) used. The US MDB is designed to represent an average midsize vehicle in the US market, while the European MDB represents a mid size vehicle in Europe. The objective of this paper is to develop a finite element model representing the US deformable barrier for use in side impact simulations. Special emphasis is made on using the various available material models in LS-DYNA and the correct adhesive properties to predict the correct behavior of the honeycomb material. These models are validated to available full-scale tests. As known by many researchers, the main difficulty of MDB modeling is the prediction of the barrier complex failure modes. In side impact tests, the severe shear deformation of the honeycomb material, full densification of barrier edge, rupture of aluminum cover sheets, and tearing of honeycomb blocks are often observed. This complex pattern of honeycomb material failure mode makes it difficult to predict. Numerical instabilities, such as negative volume, sever hourglassing, and inaccurate predictions are often experienced. No publisher mike 2009-03-26T16:48:38Z File http://www.dynalook.com/european-conf-2001/numerical-simulations-of-ductile-failure-in.pdf A test programme has been carried out to establish the mechanical properties of three extruded aluminium alloys. The investigated alloys exhibited significant anisotropy in strength, plastic flow and ductility. The anisotropy is mainly due to crystallographic texture, and an anisotropic yield criterion is needed to describe the mechanical behaviour. Several yield criteria were evaluated against the experimental data. The yield criterion Yld96 proposed by Barlat and co-workers was found to be superior with respect to accuracy for the actual aluminium alloys. In an attempt to model ductile failure of the investigated materials, a coupled model of elasto-plasticity and ductile damage was implemented in LS-DYNA for plane stress analysis with corotational shell elements. The material model combines the anisotropic yield criterion Yld96 with the associated flow rule, isotropic strain hardening and isotropic damage. The parameters defining the yield criterion and the strain hardening were determined from tensile tests and pure bending tests, while the damage parameters were identified using inverse modelling of tensile tests performed with purpose-made specimens. A series of biaxial tensile tests was also completed, and the results from these tests were used in an attempt to evaluate the constitutive model. No publisher mike 2009-03-26T16:42:03Z File