5th European LS-DYNA Conference

Birmingham, 2005

A Computational and Experimental Analysis of Ballistic Impact to Sheet Metal Aircraft Structures
Matti J. Loikkanen - Boeing Commercial Airplanes, Murat Buyuk, Cing-Dao (Steve) Kan - The George Washington University, Nick Meng - SGI

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

A failure criterion, for polymers and soft biological materials subjected to very large deformation, is presented in this paper. The criterion is written in terms of the strain invariants in finite elasticity. Experimental tests for determining the failure criterion of a material and some numerical results from LS-DYNA are shown.
A Process of Decoupling and Developing Body Structure for Safety Performance
John M. Madakacherry, Martin B. Isaac, Dr. Charles A. Bruggeman - General Motors, Dr. David Eby - CD-Adapco, Dr. Akbar Farahani - ETA, Inc., Dr. Ron C. Averill - Red Cedar Technology

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

Reliable prediction of the behaviour of structures made from polymers is a topic under considerable investigation in engineering practice. Especially, if the structure is subjected to dynamic loading, constitutive models considering the mechanical behaviour properly are still not available in commercial finite element codes. First, we give an overview of material laws for thermoplastics and show how the behaviour can be characterized and approximated by using visco-elasticity and metal plasticity, respectively. Experimental work is presented to point out important phenomena like necking, strain rate dependency, unloading behaviour and damage. A constitutive model including the experimental findings is derived. In particular, different yield surfaces in compression and tension and strain rate dependent failure, the latter with damage induced erosion, need to be taken into account. With the present formulation, standard verification tests can be simulated successfully. Also, an elastic damage model is used to approximate the unloading behaviour of thermoplastics adequately.
A Study Concerning Precision of LS-DYNA Res
Martin Feyereisen, Jeff Zais, Guangye Li - IBM
A Study on Yielding Function of Aluminum Honeycomb
Shigeki Kojima - TOYOTA COMMUNICATION SYSTEMS CO., LTD. , Japan, Tsuyoshi Yasuki, Satoshi Mikutsu - Toyota Motor Corporation, Japan, Toshikazu Takatsudo - THE YOKOHAMA RUBBER CO., LTD. , Japan

This paper describes newly developed yielding function of aluminum honeycomb. Physical compression tests of aluminum honeycomb were performed and it was found that yielding stress of aluminum honeycomb highly depended up on direction of compression. Using these test data, a yielding function was newly derived as a function of volumetric change and angle of compression. The yielding function was introduced to MAT126 as an option. ODB frontal collision analysis result with the yielding function showed much better correlation with test results than with MAT126 without the option.
A View on the Technology of both Vehicle Content and the Product Creation Process for Supercars
Neil Hannemann - McLaren Automotive

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

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

The paper concerns the vibroacoustic simulation based on the acoustic Variational Indirect Boundary Element Method (VIBEM) recently implemented in LSDYNA. In this formulation, which assumes a weak acoustic-structure interaction, the transient structural response is computed first. By applying the FFT, it is transformed into a frequency response. The obtained results are taken as boundary conditions for the acoustic BEM. Consequently, the radiated noise at any point into space can be calculated. The efficiency of the present method is checked for both pure acoustic and vibroacoustic problems. The obtained results are in agreement with the analytical solutions.
An Assessment of the LS-DYNA Hourglass Formulations via the 3D Patch Test
Leonard E. Schwer - Schwer Engineering and Consulting Services, Samuel W. Key - FMA Development, LLC, Thomas A. Pučik - Pučik Consulting Services, Lee P. Bindeman - Livermore Software Technology Corporation

The six hourglass formulations available in LS-DYNA for 8 node hexahedral elements are evaluated using the so called ‘3D Patch Test.’. It is demonstrated that three of the six hourglass formulations fail this patch test, including the popular default LS-DYNA viscous form of hourglass control. A detailed description of the 3D Patch Test is provided to allow readers to perform the simple test as part of their code verification.
An Inverse Approach to Identify the Constitutive Model Parameters for Crashworthiness Modeling of Aluminum Honeycombs and Moving Deformable Barriers
Murat Buyuk, Cing-Dao (Steve) Kan, Shaun Kildare, Dhafer Marzougui, Hasan Kurtaran - The George Washington University
Application of SynfiniWay Grid Platform for iterative LS-DYNA studies
E. Deguemp - Fujitsu Systems Europe, M. Adoum, V. Lapoujade - CRIL Technology

Whether end-users need to access local or remote systems, to use a batch system or to run jobs interactively, they will always raise the same questions: “Which system can I run my job on?” and “How do I get data to the machine where my job will execute?” Users should only need to know what applications they want to run and where the inputs for these applications are located. To answer these needs, Fujitsu markets a middleware product called SynfiniWay which hides all issues related to CPU location, and allows execution of complex applications via workflows. The conclusion of this paper is that the SynfiniWay middleware can solve LS- DYNA iterative problems: the search for an optimal mesh size or successive LS- DYNA calculations with modified initial conditions. SynfiniWay provides an infrastructure to execute these studies automatically and transparently on remote computers (grid computing).
Assessment of LS-DYNA Scalability Performance on Cray XD1
Ting-Ting Zhu - Cray Inc.

Technologists worldwide have now recognized that CAE (Computer Aided Engineering) offers an unprecedented opportunity to revolutionize product development. Today, CAE promises not only increased productivity but also faster time-to-market, lower warranty costs and above all, products that are safer, outperform and work better. With the broad acceptance of the MPI based implementation of LS-DYNA, the manufacturing industry is pushing the limits of scalability as they scramble to meet stringent product design cycle constraints. Microprocessor based cluster systems are increasingly being deployed for production workloads. But, the scalability and system efficiency can be very poor on such systems. The industry goal to reduce time-to-market can be met only if the system has a balanced architecture and the interconnect technology is able to deliver sustained performance for actual applications. In this study, an in-depth analysis will be performed to assess the performance of LS-DYNA on Cray’s XD1 system. A correlation between the hardware features of Cray XD1 and the attributes of LS-DYNA will be made. Various phases involved in a typical crash simulation, such as - initialization, element processing, contact and rigid bodies calculations will be analyzed. An MPI profiling tool will be used to monitor the MPI performance in the context of computation, communication and synchronization aspects of LS-DYNA. The communication patterns and message sizes will be studied for variety of standard benchmarks ( www.topcrunch.org ). The role of Cray XD1’s balanced architecture and the HHTUTU UUTTHH high speed interconnect technology will be presented in the specific context of LS-DYNA and production workloads. Performance results of LS-DYNA on Cray XD1 will be highlighted that truly demonstrate “Application efficiency at scale”.
Automatic Processes for Multiple Analyses
Miles Thornton, Christopher Bell, David Burton, Paul Davidson, Ben Dennis, Roger Hollamby, Richard Sturt - Arup
Benefits of Scalable Servers with Global Addressable Memory for Crash Simulation
Christian Tanasescu, Kevin Fox - SGI
Birdstrike onto the Composite Intake of a Turbofan Engine
Marco ANGHILERI,Luigi CASTELLETTI, Fabio INVERNIZZI, Marco MASCHERONI - Politecnico di Milano, Italia

Birdstrike is a menace for flight safety likely to have tragic consequences. In view of that, the efforts provided to design high-efficiency bird-proof structures are fully justified. In this work the impact of a standard 4-lb bird onto a nacelle made of composite material required for the certification of the component has been investigated using LS-Dyna 970. Initially, the dynamic behaviour of the composite material used in the manufacturing of the external skin panels of the intake was achieved by referring to specific experimental tests. It was observed, in fact, that the dynamic behaviour of the composite material has a deep influence on the failure mechanism of the structure. Subsequently, the numerical model worked out for the composite material was used to numerically reproduce a bird impact certification test. A SPH model of the bird validated in previous research was used. A good numerical-experimental correlation between experimental data and numerical results was obtained.
Buckling and post-buckling analyses of stiffened composite shells with inter-laminar damages
Aleksandrs Korjakins, Patricia Kara, Kaspars Kalnins - Technical University, Riga

In the present paper buckling and post-buckling response of axially loaded composite stiffened shell with inter-laminar damage regions have been solved using computer code LS-DYNA. Reduced number of layers and reduced stiffness in damaged region has been investigated. In addition skin delamination with contact model has been used for the analysis of the fracture toughness in the damaged regions. Energy release rates are calculated by Technique-B methodology, employing the 2D shell elements. Mode I and mode II fracture properties are obtained in the damaged regions of the carbon/epoxy composite stiffened shell. The influence of different damages regions on the buckling and post-buckling behavior of stiffened shell is investigated.
Comparison of Faceted Vs Ellipsoid Dummies In Frontal Crash Simulations
Hovenga P.E., Spit H.H., Kant A.R., Happee R. - TNO Automotive Safety Solutions

An improved Hybrid-III 50th %ile crash test dummy model has been developed in MADYMO. Advanced multibody techniques have been used to obtain fast computation times with the geometry and potential accuracy of CPU intensive finite element models. So-called facet surfaces have been used in combination with flexible bodies and rigid bodies. The MADYMO contact algorithm has been enhanced with options to separately describe the non-linear compliance of two contacting objects such as a dummy and a seat and orthotropic, penetration- dependent friction has been implemented to capture of ‘belt pocketing’ in the dummy flesh. The available set of component and full dummy validations has been extended with load cases representing the latest restraint system designs and test procedures. A systematic validation has been performed using objective rating techniques to compare the enhanced facet model to the standard ellipsoid model. Objective rating showed that the enhanced facet model provides significant benefits in particular for chest deflections.
Compression of LS-DYNATM1 Simulation Results using FEMZIP©
Clemens-August Thole - Fraunhofer Institute for Algorithms and Scientific Computing

The standard usage of simulation as part of the automotive design process has increased the demand for archiving simulation results. Intensive collaboration during the development process requires the exchange of simulation results. Compression of simulation results reduces the size of archives and the time for data transfers. Like compression of video streams and pictures, the effective compression of simulation results requires specific tools which exploit the specific data structures of LS-DYNA3D simulation results and allow for a reduced precision of the results. FEMZIP is especially designed for the compression of crash simulation results and achieves a reduction by factor of 7 for reasonable precision requirements.
Computational Biomechanics: a challenge at the engineering /life sciences interface5th
John Middleton, Georges Limbert - Cardiff Medicentre
Crash-tests simulations by LS-DYNA code on the HPC AMD64 Cluster
Prof. Nikolay Shabrov, Prof. Yuri Mikhailov, Iliya Lopatukhin,- Saint Petersburg State Polytechnical University, Russia, Dr. Evgeniy Shmelev, Dr. Sergey Kurdyuk - AVTOVAZ Company, Russia

Crash-test simulations of the car models by LS-DYNA code are carried out on the HPC 16 CPU AMD64 Opteron processors Cluster. Simulations are based on the large 3D finite element car models that contain more then one million DOF. Architecture and benchmark of the HPC 16 CPU AMD64 Cluster were tested by engineering applications with commercial engineering codes LS- DYNA instead of synthetic benchmark. For this purposes several tasks were taken from www.topcrunch.org. The tasks named “3 Vehicle Collision” and “Neon”. Benchmark tests have shown pretty good results for such type of industrial problems and confirmed that Opteron processor on AMD platform is preferable to Itanium processor on Intel platform. LS-DYNA code was used for crash analysis of real modern cars produced by AVTOVAZ in Russia. HyperMesh software was used to create finite element mesh and for a pre- processor for LS-DYNA solver. To visualize simulations as 3D virtual reality objects crash analysis results obtained on HPC Cluster were imported on 3D Virtual reality system named WorkBench. WorkBench 3D virtual reality system contains soft screen, two multimedia projectors, computer with dual heads graphics adapter and tracking system Flock of Birds. COVISE software was used for visualization of CAD models of the cars and crash analysis results as 3D virtual reality objects.
Crashworthiness of Conventionally Designed Railway Coaching Stock and Structural Modifications for Enhanced Performance
X. Xue - AEA Technology Rail, F. Schmid - University of Sheffield

In this paper, the authors present a crashworthiness assessment of a conventionally designed railway passenger vehicle and suggest modifications for its improvement. The analytical approach consisted of two stages. Firstly, the crashworthiness of the coach was assessed by simulating a collision between the coach and a rigid wall. Then, after analysing the structural weaknesses, the design of the coach was modified and simulated again in the same scenario. It was found that bending or jack-knifing is a main form of failure in conventionally designed rail vehicle structures and components. The coach design, as modified by the authors, overcomes the original weaknesses and shows the desired progressive collapse behaviour in simulation. The conclusions have general relevance and suggest the need for a rethink of some aspects of rail vehicle design.
Current and Future Developments of LS-DYNA
Dr. J. O. Hallquist - Livermore Software Technology Corporation
Current Features of LS-PREPOST
LSTC
Deformable Rigid Bodies in LS-DYNA with Applications – Merits and Limits
Karl Schweizerhof, Johann Bitzenbauer - University Karlsruhe, Germany, Ulrich Franz - DYNAmore GmbH, Germany

Modal methods are long known in linear dynamic analysis for efficient computations of the response of structures. The mechanical idea behind is to find a particularly useful problem dependent basis (so called eigenfunctions or eigenmodes) which can be separated into some of major importance for the behavior of the structure and others of minor interest (which can be subsequently disregarded). Unfortunately this concept is basically a completely linear one. However, more recent versions of LS-DYNA offer the possibility to superimpose shape functions from a previously computed eigenmode basis with a nonlinear rigid body motion for parts of the structure. This allows to consider at least some of the elastic behavior of a body which would be otherwise considered completely rigid. The resulting displacements are then computed with standard explicit methods, allowing on one side a substantial reduction of the number of degrees of freedom and on the other side parts of the system can be still computed in a fully nonlinear manner. The method has been presented in [1]. In the current contribution, two different practical applications, a head impact problem and a deep drawing simulation are presented and compared to a fully nonlinear solution.
Design and Implementation of a Multi-Fabric Message Passing Interface (MPI): Intel® MPI Library
Dr. Michael D'Mello - Intel Americas Inc., USA

Environment & Situation Analysis Program direction Intel® MPI Design Considerations – High Level Design – Stability – Functionality – Performance – Portability – Environment & Tools support – Extensibility Highlights of Intel® MPI Program
Developing FE-TIRE Model for Road Noise Simulation
Masaki SHIRAISHI - SRI R&D Ltd., Kimihiro HAYASHI - The Japan Research Institute,Limited
Development of a Numerical Model of an Anthropomorphic Test Device for the Study of Human Related Impact Events
Elisa OLDANI, Emanuele FRACASSO, Luigi-M. L. CASTELLETTI, Marco ANGHILERI - Politecnico di Milano, Italia

The aim of this work is the development and validation of a numerical model of an Anthropomorphic Test Device for the simulation of impact events involving humans and consequently the study and development of crashworthy structures and restraint systems. The research approach consisted in a first validation by subcomponents of the numerical model, comparing the response of the model to the results of experimental tests specifically designed for this purpose. Then, the whole model response was observed and compared to experimental tests reproducing standard tests for the homologation of helicopter seats, in order to validate the model for use in a specific category of impact events. The simulation results showed very good agreement with the experimental tests, proving the Anthropomorphic Test Device numerical model a reliable tool for the analysis of analogous impact events. The model looks also promising for future developments, in particular it is suitable to be further improved in order to be able to reproduce a faithful response in different impact scenarios.
Development of BioRID-II Dummy Model in Cooperation with the German Automotive Industry
Peter Schuster, Sebastian Stahlschmidt, Uli Franz - DYNAmore GmbH
Development of Orbital Debris Impact Protection Panels
M. ANGHILERI, L. CASTELLETTI, F. INVERNIZZI, M. MASCHERONI, F. PIGOLI - Politecnico di Milano, Italia

The presence of debris in the orbits used by artificial satellites represents an actual threat for space operations – as such an event is likely to cause the failure of the satellite. Spacecraft hulls are in general built with honeycomb-cored sandwich panels made of Aluminium alloys - which are not effective as a protection in case of medium size debris impact. Using LS-Dyna 970, the benefits (from a mechanical standpoint) coming from the use of materials such as polymeric foams or aramidic fibres in manufacturing hull panels were investigated. Indeed, these materials are frequently used in common applications for their excellent ballistic characteristics and low weight. Initially, a reliable numerical model was developed referring to experimental tests consisting of the impact of medium size debris against sandwich panels with honeycomb core. Hence, using the same impact scenario of the tests, the impact behaviour of different panel typologies obtained using a polymeric foam core or using aramidic fibres as reinforcement was evaluated. As a result, it was possible to highlight the advantages coming from the use of these materials in order to have lightweight and debris-proof structures.
Experience from Using a New Material Model for Stainless Steels with TRIP-effect
Daniel Hilding - Engineering Research Nordic AB, Erik Schedin - Outokumpu Stainless AB, Avesta Research Centre

This paper presents experience from using a recently developed material model for austenitic stainless steels with TRIP-effect for simulation of sheet metal forming. Results from two different forming operations are presented. In materials with TRIP-effect, a phase transformation from austenite to martensite occurs during forming that significantly affects the hardening behavior. The effect is sensitive to the amount of straining as well as the temperature. For materials that have a strong TRIP-effect new forming techniques are possible that can lead to very light and strong components. The material model for austenitic stainless steel sheet exhibiting the TRIP-effect has been implemented in LS-DYNA.
External blast load on structures – Empirical approach
G. Le Blanc, M. Adoum, V. Lapoujade - CRIL TECHNOLOGY

Modeling structures response to blast loads interests more and more people concerned about industrial accidents and/or terrorism. Today, two approaches are available: one can either use an ALE model (*ALE) with a lagrangian-eulerian coupling (*CONSTRAINED_LAGRANGE_IN_SOLID) or a pure lagrangian approach where an analytical loading of the structure replaces the computation of the propagation. The lagrangian approach allows the use of a much smaller model since only the structure is modeled. This kind of approach, based on the empirical model described in the TM5-855 US army handbook (CONWEP), is currently available in LS-DYNA (*LOAD_BLAST). However, it is limited to the treatment of the explosions of hemispherical charges on the ground or spherical charges in the air without ground interaction. In many cases, the interaction of the shockwave with the ground induces blast reinforcement. CRIL TECHNOLOGY, in order to get more precise blast load evaluation with a pure lagrangian approach, has developed a new user-loading model (evolution from *LOAD_BLAST) to take into account new abacuses for TNT and for reflecting coefficients, ground effects and Mach stem. Major evolutions are based on empirical models described in the TM5-1300 US army handbook. This new user-loading, in many cases leads to more precise and more conservative load while retaining a reasonable model size as the method is purely lagrangian.
Failure Modes Analysis in the Crash Barrier Simulation
Lei Hou - CELLBOND, UK

The technology of FEA modelling is expanding rapidly in the field of automotive safety analysis. From the pre/post-processing for the material impact to the mathematical equations in the solver the non-linear analysis becomes a vital part of the simulation. In this paper we trace the development of experimental data validated-analysis method for the Cellbond honeycomb barrier model by using LS-Dyna software. The utilization of the database from IIHS and Advanced-MDB cores in the estimation of solid material parameters enables our simulation well framed into the impact criterion corridors. Over the past 10 years in Cellbond Ltd, at least three general categories of experimental-analysis methods can be identified in the failure modes classification: (1) Forced-Normal Mode Tests, (2) Dynamic Frequency-Response Filtration and (3) Mathematical Estimate against Theory. FEA impact-analysis method for each of these categories can be incorporated as multiple-input concept in one way or another. Historically, the failure modes characteristics of structural mechanical systems have been estimated by techniques that fall into either the first or second category. The forced-normal mode tests method has always been included in the repeated single inputs concept while the Dynamic Frequency-Response Filtration method, until recently, only involved the application of multiple-input. This paper presents a generalised FEA-modes-analysis method with emphasis on the including the refinements of the previous methods. The FEA-modes- analysis method, that fall into the last two categories are composite approaches that utilize the static load-curve estimation algorithms based upon structural models and include multiple-input concepts. The current FEA developments in the areas of dynamic simulation are encouraging.
Finite element modelling of the static axial compression and impact testing of square CFRP tubes in LS-DYNA3D
Dimitrios Papapostolou - National Technical University of Athens

LS-DYNA3D finite element code was used for investigating the compressive properties and crushing response of square FRP (Fibre Reinforced Plastic) tubes subjected to static axial compression and impact testing. Several models were created in order to simulate a series of static and dynamic compressive tests that were performed in the National Technical University of Athens (NTUA) using carbon FRP tubes, that were featured by the same material combination (woven fabric in thermosetting epoxy resin) and external cross-section dimensions but different length, wall thickness, laminate stacking sequence and fibre volume content. Modelling the three modes of collapse observed during the experimental works (i.e. progressive end-crushing with tube wall laminate splaying, local tube wall buckling and mid-length unstable crushing) was the primary goal of the simulation works. The agreement between calculations and test results regarding the main crushing characteristics of the tested CFRP tubes –such as peak compressive load and crash energy absorption– and the overall crushing response of the tubes was quite satisfactory as the finite element models were refined several times in order to achieve optimum results.
Fluid Structure Interaction with *MAT_SOFT_TISSUE and EFG Elements
Rudolf Bötticher - TMB GmbH

This paper presents LS-DYNA 970.5434a transient simulations for the fluid- structure interaction (FSI) in a prototype biomedical duct. Standard and element free Galerkin (EFG) elements are compared for the nearly incompressible membrane out of *MAT_SOFT_TISSUE, which is a composite reinforced hyperelastic material. The coupling of a multi-fluid arbitrary Lagrangian Eulerian (ALE) solid domain to an EFG solid domain is possible and its LS-DYNA implementation keeps developing. The paper describes particularities of this coupling. The EFG simulation for nearly incompressible materials necessitates a non-default support of 1.4x1.4x1.4 or even higher for accurate results. The EFG simulation demands higher computation times than the standard formulation with reduced integration and type 6 hourglass control. An example is shown, in which the high ratio of the elastic moduli chosen for the fibers and the bulk of the soft tissue material generates a severe hourglass problem that only the EFG method can cope with. The standard formulation, however, is remarkably robust and it proves difficult generating an extreme situation where only EFG works and the solver run would abort otherwise. So the potential of the EFG method lies in the accurate prediction without introducing non-physical energy in the system for hourglass stabilization, in situations, where selective reduced or full integration show a too stiff behavior and reduced integration has a hourglass problem. Although LS-DYNA 5434a is already much faster than 5434, a more computational efficient implementation of EFG for solid elements is required. Therefore, the features of the LS-DYNA 971 beta version, which address this lack of performance, are assessed as well. The paper features an abstracted input deck.
Fluid-Structure-Interaction Effects in Airbag Out-of- Position Load Cases: An introduction to the ALE- framework in LS-DYNA
Dr. A. Haufe, Dr. K. Weimar - DYNAmore GmbH
Further Improvements to the Truck Model for Roadside Safety Simulation – Suspension and Steering
Dustin A. Boesch - Quartus Engineering Inc., John D. Reid - University of Nebraska-Lincoln

Pickup trucks are commonly used for crash testing of roadside safety hardware, while nonlinear finite element analysis using LS-DYNA is commonly used to simulate that crash testing. To improve the accuracy of simulation a new front suspension and steering system was developed to replace the existing system on a pickup truck model used for roadside safety simulation. All of the critical components, such as mounting points, alignment, track width and mass, were incorporated into the new model, along with the capability to make the most important components deformable by carefully modeling the geometric details. It is believed that these modifications significantly improve the performance of simulating impacts with roadside curbs, rocks, or culvert grates, where dynamic suspension movement is essential, and with guardrail systems when deformation of the lower control arm is important
General considerations for the influence of mesh density in LS Dyna
Udo Jankowski, Manfed Sans, Michael Fairchild - TECOSIM GmbH

Accurate and reliable CAE results are essential for the product development process in manufacturing industries. This is particularly so in the automotive industry where virtual simulation predictions are gradually replacing physical testing in the ever greater drive to reduce product development time and costs. CAE is nowadays completely integrated in the development process and critical design decisions are often based on the FEM calculations. The accuracy of predictions is very much dependent on the detail used to model physical structures; larger the models, better the results. However, larger models also demand much greater computing resources, especially for crash simulations. Model sizes are, therefore, dictated by reasonable computing times to solve the equations. At the same time, there is also a tendency to produce larger models not only for better accuracy but also as a result of use of automatic model generation to reduce time and cost for this phase of CAE analysis and to enable effective decision making based on CAE performance predictions. This background will be documented in this paper.
Grid-Based LS-DYNA Solutions
Henry H. Fong, Jonas Edberg - Sun Microsystems, Inc.

In addition to offering SPARC/Solaris systems for MCAE users, Sun Microsystems also markets Opteron-based servers and workstations. These Opteron solutions offer excellent price/performance for LS-DYNA simulations, and are particularly suitable for clustering. Users have a choice of three operating systems: Solaris 10 x64; Linux (SuSE or Red Hat); or Microsoft Windows. This paper describes briefly these computing systems, and show some typical LS-DYNA performances on standard benchmarks such the 3-car- crash problem. Also cited is a Mefos cold rolling benchmark, run using both a SPARC/Solaris Sun Fire V480 server as well as a cluster of Sun LX50 Xeon- based processors. Sun's cluster systems typically utilize Sun's N1GE grid engine load management software to schedule, manage, and prioritize compute jobs.
Heat Transfer in LS-DYNA
Arthur B. Shapiro - Livermore Software Technology Corporation

LS-Dyna can solve steady state and transient heat transfer problems on 2- dimensional parts, cylindrical symmetric parts (axisymmetric), and 3-dimensional parts. Heat transfer can be coupled with other features in LS-DYNA to provide modeling capabilities for thermal-stress and thermal-fluid coupling. This paper presents several examples using LS-DYNA for modeling manufacturing processes (e.g., metal forming, welding, casting).
Impact Analysis of a 16t Truck against different Road Safety Restraint Systems
Elisa Oldani, Luigi Castelletti, Marco Anghileri, Mario Mongiardini - Politecnico di Milano, Italia

In this work, the Finite Element model of a 16-ton truck suitable for the numerical analysis of the impact with road safety devices is described. The possibility to correctly reproduce the behaviour of both the vehicle and the barrier before the actual testing is greatly helpful in the design of restraint systems and it can avoid failure of tests. Particular attention was paid in modelling features of the truck such as frame, suspensions and tyres, which play a central role in determining the vehicle behaviour during the impact. The truck model complies with the requirements for the homologation of H3-type barriers, in accordance with the European standard CEN EN 1317. Impacts against two different restraint systems were considered: a concrete New Jersey-type barrier and a H3-type steel deformable barrier. The simulations were carried out using LS-Dyna 970 that has shown to be particularly suitable for this kind of analysis. Eventually, results have showed the reliability of this model for the design and analysis of safety barriers.
Improvement Design of Vehicle’s Front Rails for Dynamic Impact
Chien-Hsun Wu, Chung-Yung Tung, Jaw-Haw Lee - Automotive research & testing center, Caleo C. Tsai - China Motor Corporation

Frontal collision tests indicate that the energy absorbing components playing the main role of providing protection for the occupants during the crashing processing. The frontal rails are the main components to absorb energy during collision. The position of the spot welding, beads, the cross section and thickness of the frontal rails are significantly facts that affect the energy absorption during impact. This paper is concentrated on improving the energy absorbing efficiency of the vehicle’s front rails during impact and giving better existing space of the passenger compartment after collision by using LS-DYNA. Utilize the improved model to enhance the exiting vehicles and compare the results to the frontal impact test.
Integrating LSTC and MSC.Software Technology for Explicit Dynamics and Fluid-Structure Interaction
Erik Plugge - MSC.Software Benelux B.V.

LSTC and MSC.Software have entered a long-term strategic partnership, with the objective of integrating complementary technology to the benefit of the structural and fluid dynamics community. This paper presents some of the technical aspects of this integration, highlights the technologies being used, and demonstrates the new application capabilities being enabled by this partnership. The presentation will focus on two aspects of code coupling. Firstly, between MSC.Software’s MSC.Dytran Eulerian solver and LSTC's LS-DYNA explicit solver, and secondly the integration of LS-DYNA explicit solutions via the SOL700 sequence in MSC.Nastran. Both the Eulerian solver in MSC.Dytran and the structural explicit solver in LS- DYNA are unique in their class. Coupling the two codes together allows FSI (Fluid-Structure Interaction) simulations to be run efficiently and on a high level of accuracy and speed. Similarly, coupling of the LS-DYNA explicit solver with MSC.Nastran via SOL700 enables a new range of applications in crash and impact from within a general-purpose structural environment. This paper describes technical aspects of how these code integrations have been developed, and presents a range of application areas and examples of the new dynamics and fluid-structure interaction capabilities achieved.
Integrative crash simulation of composite structures
Stefan Glaser- Andreas Wüst - Engineering Plastics Europe - KTE

-- Integrative Simulation? - Motivation - Fiber orientation in filling process - Material modelling - Influence of fiber orientation tensor -- Simulation applications - Simulation of material tests - Static loading - Crash loading
LS-DYNA performance on new computing choices from IBM
Guangye Li, Jeff Zais, Greg Clifford - IBM
MODELING of WELDING SEAM SEQUENCES
Sergey Medvedev, Maria Petrushina, Oleg Tchij - National Academy of Sciences of Belarus

This paper explores simulation techniques for prognosis residual strains of welded structures taking into account welding seam sequences. Simplified approaches of welding stress and strain theories were used and implemented on SKIF-family supercomputers. The elaborated program options allow to apply the fictitious shrinkage forces to the weld models of arbitrary space location. The results of the experimental computational verification of the proposed approaches are presented, welded structures models of complicated design being used. The obtained results meet good agreement with data obtained in the production processes and special literature.
Modelling of damage in composite materials using interface elements
W.G. Jiang, S.R. Hallett, M.R. Wisnom - University of Bristol

A simple and robust implementation of an interface element has been addressed in this paper. A new state variable is introduced to trace the extent of damage accumulated at the interface. The element not only simulate mixed mode delamination propagation in composite materials but also satisfactorily deals with mode ratio change during the debonding process. The interface model is implemented in LS-DYNA code. The model has been applied to scaled open hole tension tests. Comparison between numerical results and experiments shows good correlation.
Modelling of the failure behaviour of windscreens and component tests
D.-Z. Sun, F. Andrieux, A. Ockewitz Fraunhofer Institute for Mechanics of Materials, H. Klamser, J. Hogenmüller - Dr. Ing. h.c. F. Porsche AG

Windscreens from laminated safety glass (glass/PVB interlayer/glass) are widely used in automotive structures and have an important contribution to the stiffness of the vehicle. The stiffness of the laminated safety glass is dominantly given by the two layers of glass while the PVB interlayer serves to fix glass splinters to avoid serious injuries of the passengers in a collision. A finite element model for modelling the failure behaviour of laminated glass windscreens is presented. A special element structure with three layers (shell/volume/shell) has been used to model the laminated glass windscreen. A fracture criterion for brittle fracture based on the maximum principal stress (σI ≥ σc) was applied to model the fracture behaviour of glass. The PVB interlayer was modelled with both a linear elastic and a hyperelastic material law without damage. The critical fracture stress of glass was determined by fitting the failure force measured from static bending tests on laminated glass windscreens. The transferability of the fracture criterion and the corresponding parameter was checked by simulating two different loading cases of the component tests.
Modelling Study to Validate Finite Element Simulation of Railway Vehicle Behaviour in Collisions
X. Xue - AEA Technology Rail, F. Schmid - University of Sheffield

Half-width/full-length and half-width/half-length vehicle models, based on geometrical symmetries, have been adopted widely in the finite element modelling of rolling stock structural behaviour. These techniques have been successful in the analysis of rail vehicles undergoing static loading, such as the proof load test, and in basic impact studies. Until now, such rail vehicle impact tests and associated simulations have been largely confined to impact scenarios where a rail vehicle collides with a rigid wall or a rigid body. This is also a standard model specified in the crashworthiness section of the Technical Standards for Interoperability. The authors identified a need to study the limitations of these impact scenarios and modelling techniques when applied to dynamic impacts. The authors of the paper present the results of studies focusing on the above areas. The work was carried out by means of finite element analysis and comparison. The train set studied is a conventionally designed high-speed electric multiple unit. Finite element models of full vehicle structures were used in all impact scenarios. It was found that impact modelling could mask some structural weaknesses when using a rigid wall as the impacted object. A symmetrical impact was shown to lead to an unsymmetrical result and, therefore, both half and quarter structure models may hide some aspects of crash behaviour. These findings have significance for both impact simulation and the physical testing of rail vehicles.
Moving Beyond the Finite Elements: A Comparison between Finite Element Methods and Meshless Methods for Modeling Honeycomb Materials and Simulating Side Impact Moving Deformable Barriers
Murat Buyuk,Shaun Kildare,Cing-Dao (Steve) Kan - The George Washington University

Movable Deformable Barriers (MDBs) are used in surrogate tests to represent the behavior of an average midsize vehicle. The main difficulty in MDB modeling is the prediction of frontal energy absorbing barrier, where honeycomb materials are used and usually expected to simulate 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, severe hourglassing, and inaccurate predictions are often experienced. In this study, National Highway Transportation Safety Administration (NHTSA) side impact MDB is modeled by using a 3D non-linear explicit dynamics numerical solver, LS-DYNA. As a conventional modeling technique, both barriers are first modeled by using Lagrangian solid hexahedron finite elements (FEs). Mat-26 (*MAT_HONEYCOMB) is used as a constitutive model for the barrier construction. By using this Lagrangian model as a reference point, Eulerian and Arbitrary-Lagrangian Eulerian (ALE) models of the MDBs are also created. However, when the distortions become very severe, especially Lagrangian FE algorithms are not always adequate. Honeycomb material behavior is found to behave unstable in this type of impact problems. More recently meshless methods (or particle methods) have been developed and applied to solid mechanics problems since they can efficiently be used to represent severe distortions. In this study, Element Free Galarkin (EFG) model of the MDB is also created. Each MDB model is compared to a full scale crash test against a load cell wall. Accelerometer responses from the simulations are compared to the measured values from the test. Computational costs of the systems are also compared to provide a foresight for the usage of the meshless methods in transportation safety field related research. Dhafer Marzougui, FHWA/NHTSA National Crash Analysis Center, The George Washington University
MPP Implicit for LS-DYNA v. 971
Cleve Ashcraft, Roger Grimes, Bob Lucas - LSTC

The Vision • LSTC wants to provide a single package that allows users to perform all of their analyses. – Implicit computations must be integrated with explicit – Linear analyses (useful for debugging large models) must be integrated as well.
Multidisciplinary Optimisation and the Design for 6 Sigma
Dr. Tayeb Zeguer - Jaguar Cars Ltd
New Features in LS-OPT Version 3.0
Nielen Stander, Willem Roux - Livermore Software Technology Corporation
NUMERICAL SIMULATION OF DAMAGE IN THERMOPLASTIC COMPOSITE MATERIALS
Kevin Brown - University of Nottingham, Richard Brooks, Nicholas Warrior

Thermoplastic composites are being considered for application in vehicle bumper and front-end structures for increased pedestrian protection. This paper describes recent progress in the calibration and validation of LS-DYNATM material model 162 (*MAT_COMPOSITE_DMG_MSC) for the modelling of impact damage in the glass/polypropylene commingled fabric thermoplastic composite, TwintexTM. In this study, MAT 162 is calibrated by using a series of tests that were conducted at quasi-static and dynamic loading rates. These consisted of in-plane tension, shear and compression tests. A novel procedure for calibrating in-plane shear damage is presented. To demonstrate the predictive capabilities of the model, the response of TwintexTM laminates subject to dynamic impact loading is simulated. The force–time histories and damage predictions are successfully compared with corresponding experimental instrumented falling weight test results. It is concluded that MAT 162 provides a versatile tool for predicting damage progression in thermoplastic composites.
Numerical simulation of ground impact after airdrop
Yves de Lassat de Pressigny - Centre d’Essais en Vol, MinDef/DGA/DE, France, Vincent Lapoujade - CRIL Technology, France

The airborne forces of many countries use honeycomb paper as energy damping material (EDM) for heavy cargo airdrop. Its roughly constant crushing resistance makes the dimensioning of the kinetic energy absorber layer quite easy. Yet the velocity and attitude of a parachute at ground impact is variable, due to weather conditions, or undamped pendulum movement of the load under the parachutes. Those parameters have a big influence on the shock level generated at ground impact. Since ground and flight testing is long and expensive, the Flight Test Centre (CEV) of the French MoD has been developing simulations tools to evaluate the EDM design efficiency for all impact conditions at the rigging’s draft design level. In 2003, the CEV definitely chose LS-DYNA for that kind of simulation and proved the consistency of the results for Shock Response Spectrum (SRC) prediction and comparison. The paper presents the modelling work made for the EDM an application results for ammunition and vehicle airdrop.
Numerical simulation the bottom structures grounding test by LS-DYNA
Ainian Zhang, Katsuyuki Suzuki - The University of Tokyo,

Nonlinear finite element method (FEM) is a powerful tool for analyzing ship collision and grounding problems. The reliability of the numerical simulation results largely depends on the proper definition of problem and careful control of some critical parameters. The purpose of the paper is to study the effect of selected parameters on crashworthiness of the single-hull bottom structure due to raking. The quasi-static grounding process is simulated by the LS-DYNA code. The effects of the following parameters are considered: the boundary condition, the friction coefficient, shell element type, the residual stress and the material model. The influences of selected parameters are assessed by comparing the different results in the impact force and absorbed energy vs. penetration of rock model. Some suggestions are proposed for numerical simulation in finite element code LS-DYNA.
On the Optimization of the Punch-Die Shape: An Application of New Concepts of Tools Geometry Alteration for Springback Compensation
A. Accotto, G. Anedda, M. Sperati, R. Vadori - Altair Engineering Srl

This work here presented concerns the activities of stamping tools alterations of an automotive component done thanks optimization technologies. The process of nominal geometry alteration of a complete stamping die is traditionally based on the experience of the try-out people who manually modify the tools in order to compensate geometrical differences due to springback under a Trial-and-Error approach and often the restroking die needs so substantial modifications to lead to be partially re-designed . With the introduction of new steels, high tensile steels with considerable springback effects, this approach become more and more difficult. Trial and error techniques used in the reality in the try-out phase now are possible in the development phase thanks to morphing technologies in HyperForm. But an innovative technique, developed at Altair Engineering, give the possibility to proceed automatically and systematically: the approach, general and flexible, is based on a orthonormal base of deformation functions that allows the automatic management of the geometry alteration of the die. Not least the principle to obtain a small geometry error after the cutting stages, before the restroking stage. The geometry alteration are hence applied on the draw tools. The process is automatically managed by an optimization algorithm in Altair HyperStudy, who manages the geometrical parameters who define the die shape in order to converge to the optimal die shape. This paper shows how the morphing approach and the automatic deformation function approach converge to the same solution and the improvements obtained in the reality.
Perforation of Composite Floors
William Algaard, John Lyle, Conrad Izatt - Arup

Rapid construction methods for multi storey buildings involve maximising the tasks that can be carried out simultaneously on site. The risks of construction workers, fitting out lower floors, being hit by large objects dropped during installation can be managed by understanding the protection provided by the intermediate floors. This paper describes a Finite Element based methodology for assessing the impact event using LS-Dyna. The aim of the method is to evaluate low velocity impacts of heavy objects dropped onto concrete floors in order to establish the potential for perforation. The methodology is validated by comparing the simulation results with empirical penetration formulae available for concrete structures and with some experimental results. It is concluded that the perforation limits can be predicted with good confidence, but that further experimental research in the low velocity range is desirable.
Post-test simulation of airliner wing access panel subject to tyre debris impact
R. S. Birch, D. Karagiozova, R. A. W. Mines - University of Liverpool, C. Bergler, M. Kracht - CADFEM GmbH

The purpose of the investigations described in this paper is a simulation approach for tyre debris impact on wing access panels. Aircraft tyre rubber has a complex structure containing directional layers of nylon reinforcement embedded in the rubber matrix. Material properties of the compound have been derived from quasistatic compression and tensile tests with specimen cut in circumferential and axial direction of the tyre, i.e. with various reinforcement orientations. The Mooney-Rivlin material model describing the structural response of rubber, with embedded layers of elastic reinforcement cables, are used for the idealization of the tyre material. The material constants and reinforcement properties have been calibrated by the quasistatic specimen tests. The tyre mode then has been validated by dynamic impact tests of tyre fragments shot onto aluminium plates under an angle of 45 degrees. Measurements of transient strains of the aluminium plate shows good agreement with the simulation. For the full scale tests, tyre specimen with dimensions of 425x100x27mm were shot onto an access panel, fixed on a steel holding plate, at a velocity of about 110m/s and an angle of 45 degrees. Measurements were taken from strain gauges fixed to the inner surface of the outer cover and to the outer surface of the inner cover. Three tests with approximately the same parameters were carried out and showed good reproducibility of the strain curves. The mesh dependent parameters of the tyre model had to be re-calibrated for the full scale impact test simulation, to obtain a reasonable mesh density. The geometry of the tyre specimen has been matched according to the test. Simplifications that are assumed for the access panel idealization are e.g. the modelling of screws by a tiebreak contact formulation and the neglected rubber seal. The simulation results show a tyre deformation that is quite similar to the test. Also the calculation of the dynamic strains correlates well with the test. The tyre model proves to be robust and can be used for future analyses.
Productivity Gain in Crashworthiness Simulation EASi-CRASH for Complete Safety and Crash Modeling for LS-DYNA
Shivakumar Shetty, Petter Sahlin - ESI Group

The pre and post-processing for crashworthiness and safety simulation in automotive development projects is constantly changing. New functionality of the solver requires evolutionary updates, while the paradox of combining reduced lead times with an ever increasing range of regulatory tests calls for more dramatic improvements and innovative approaches. Hence the changes, the underlying need is constant – to increase productivity in model build-up, analysis and results evaluation for crashworthiness and safety simulation. This paper will present what is essential for productivity gains in crash modelling and results evaluation for simulation with LS-DYNA - exemplified with use cases from OEMs and major safety suppliers.
Recent Development for Metal Forming Simulation
Yasuyoshi Umezu, Ninshu Ma - The Japan Research Institute, Ltd., Japan

Since 1996, Japan Research Institute Limited (JRI) has been providing a sheet metal forming simulation system called JSTAMP-Works packaged the FEM solvers of LS-DYNA and JOH/NIKE3D, which might be the first multistage system at that time and has been enjoying good reputation among users in Japan. To match the recent needs, “faster, more accurate and easier”, of process designers and CAE engineers, a new metal forming simulation system JSTAMP-Works/NV is developed. The JSTAMP-Works/NV packaged the CAD automatic healing function in it and had much more new capabilities such as prediction of 3D trimming lines for flanging or hemming, remote control of solver execution for multi-stage forming processes and shape evaluation between FEM and CAD. On the other way, a multi-stage multi-purpose inverse FEM solver HYSTAMP is developed and will be soon put into market, which is approved to be very fast, quite accurate and robust. Lastly, authors will give some application examples of user defined ductile damage subroutine in LS-DYNA for the estimation of material failure and springback in metal forming simulation.
Self-piercing riveting
Andre Stühmeyer - CAD-FEM GmbH

Overview • The self piercing riveting process • FE analysis of the joining process – Large deformation – Material failure – 2D remeshing approach – 3D remeshing approach • Comparison with experiments • Process optimization with FEA • Summary
Shape Optimization of a Vehicle Crash-box using LS-OPT
Marcus Redhe, Larsgunnar Nilsson - Engineering Research Nordic AB, Fredrik Bergman - Saab Automobile AB, Nielen Stander - LSTC

The aim of this project is to optimize the geometry of a crash-box due to impact at low velocity impact. The optimization problem is solved in LS-OPT, using Neural Networks as meta-model. The Neural Networks meta-model has been evaluated on a small test example and it shows remarkable good approximation of the responses. The geometry was parameterized using HyperMorph. In addition to the geometry parameters, the sheet thickness and the material quality of the crash-box and the bumper-beam were also varied. The FE-model used is a passenger car from Saab Automobile. The objective is to minimize the mass of the crash-box subjected to two deformation constraints and a constraint on the maximum plastic strain in the main crash-rail, which is positioned behind the crash-box. During the optimization procedure, unfortunately, the crash-rail shown to be too weak and it need to be strengthening up using an extra component in the weak section of the crash-rail. Consequently no solution that fulfilled all constraints was found. However, LS-OPT reduced the mass of the component with 20 % and in the same time reduced the sum of all constraint violations with 50 %. Only the plastic strain constraint was violated after five iterations. The meta-modelling technique using Neural Networks showed good results with small surface approximation errors.
Side Member Crumple Section Simulation and Structural Optimization
Taian Chen, Clive Chirwa, Wei Wang, M. Mao - The University of Bolton

Energy absorbing structural component in a car front impact The study shows the energy management of the front end structure it’s stiffness, strength and crush mode as function of occupant load. A well designed front end structure will have loads well below the tolerance limit of actual injury criteria (FMVSS 208, ECE R94) Progressive tube axial crushing and s-shape tube bending are commonly used as energy absorbers This paper presents experimental and FE parametric study of side member energy absorption capability, its force characteristic and the collapse mechanism
Simulation of Hydrodynamic Ram and Liquid Aeration
S.C.McCallum, D.D.Townsend - BAE SYSTEMS

During the past several years, research within BAE SYSTEMS has concentrated on developing a capability for simulating Hydrodynamic Ram (HRAM). In this paper we demonstrate how the ALE technique in LS-DYNA can be used to simulate the principal stages of HRAM with liquid aeration. LS-DYNA is used to simulate the impact of a small steel sphere at 2km/s into a water-filled container manufactured from 3.2 mm thick aluminium alloy L165. The simulation results are compared with laboratory experiments from a two-stage gas-gun facility showing close agreement with peak pressure and impulse values. In additional simulations, aeration is modelled using an effective equation of state, which describes the compressibility of the water (on a macro-scale) inside the container. The simulation results show that aeration can be used to alleviate the shock wave that forms ahead of the projectile in order to reduce damage on the surrounding structure.
Simulation of the Crash Performance of Crash Boxes based on Advanced Thermoplastic Composite
Matthias Hörmann - CADFEM GmbH, Germany, Marco Wacker - Jacob Composite GmbH, Germany

Because of their superior mechanical properties in combination with a relative low density Fiber Reinforced Composites (FRC) are of great potential in the area of lightweight structures respectively applications. Consequently FRC is gaining influence and acceptance not only in the automotive industry. Unfortunately the application of endless reinforced composites with duroplastic matrix was mainly restricted by a production technique unsuitable for a full production run. Up to date it was only possible for short and long fiber reinforced duroplastic SMC (Sheet Molding Compound) and thermoplastic GMT (Glass Mat Reinforced Thermoplastic). Compared with conventional reinforced duroplastics the continuous reinforced thermoplastic composites (Advanced Thermoplastic Composites) have the capability for a full production run in terms of a thermoforming procedure (see Figure). With this technique Jacob Composite and partners were able for the first time to deliver fiber reinforced composite bumper beams in a number of 50.000 pieces/year for the automotive industry.
Simulation of Wave-Dissipating Mechanism on Submerged Structure using Fluid-Structure Coupling Capability in LS-DYNA
Sunao Tokura, Tetsuji Ida - The Japan Research Institute, Ltd.

Understanding the wave-dissipating mechanism of seashore structures is important to design effective seashore protection system against high waves. From the engineering point of view, wave dissipation with seashore structures is considered as a kind of fluid-structure interaction (FSI) problem. Recently constructing a submerged structure "flexible mound" is increasing for some advantages. The flexible mound is made of rubbery material and is deformable. Authors tried to apply the ALE (Arbitrary Lagrangian Eulerian) capability in an explicit finite element program LS-DYNA to this problem and compared the behavior of conventional "rigid mound" (breakwater) and flexible mound. Through this preliminary study authors showed that the FSI analysis using LS-DYNA could widely be used to design shore structures.
The “Shaken Baby” Syndrome; Computational Studies of a New Hypothesis of its Cause
J.Cheng, S. Cirovic, I.C. Howard, A. Yoxall, M.A. Parsons - The University of Sheffield

The term “shaken baby syndrome” refers to a unique pattern of non-accidental traumatic injury occurring in children by shaking. Typical injuries include subdural haemorrhage, retinal haemorrhage as well as tears to cortical bridging veins. Infants younger than 6 months are significantly more vulnerable to the shaken baby syndrome than older infants and children, a fact that has been difficult to reconcile with all previous explanations of the phenomenon. The paper explores a new hypothesis for the unique vulnerability of infants (i.e. those younger than about 6 months) to shaking: - the different motions of the brain in skulls with and without the flexibility provided by the fontanelles. The investigation involved the study of two highly simplified finite element models of a skull and brain subjected to shaking, namely, one with a representation of the fontanelle, and one without. The results revealed dangerously enhanced local accelerations and shear strains in the region of the fontanelle. These findings provide a potential mechanism for the special vulnerability of infants to shaking, and suggest some reasons why shaking motions can be much more dangerous than those associated with impact.
The Applicability of the Universal HP-MPI to MPP LS-DYNA on Linux Platforms
Yih-Yih Lin

In addition to its parallel algorithm, MPP LS-DYNA for cluster computing derives its parallelism from the MPI library and the interconnect. MPI has always had a standard since its inception. On the other hand, there are diverse interconnects and switches in the market, each with unique low-level interface and performance considerations. This variety of interconnects has resulted in a difficult support burden for LSTC, the software developer, and also resulted in inconvenience for MPP LS-DYNA users. To address this difficulty in portability HP-MPI was invented. HP-MPI has enabled a single MPP LS-DYNA executable to work on most prevailing interconnects on a given Linux hardware platform, HP or non-HP. In this paper, the universal applicability of HP-MPI to diverse interconnects on Linux platforms will be verified by the MPP LS-DYNA simulation on the well- known 3-Vehicle-Collision model. Furthermore, it will be shown that the performance of HP-MPI is on a par with, and often better than, other MPI libraries. HP-MPI is ensured with the highest quality because every one of its release is qualified with a suite of 2000 tests. Thus we can safely claim that HP- MPI, being a supported product and requiring no end-users licensing, is the only MPI that MPP LS-DYNA users need on most Linux platforms.
The Application of Optimization and Robustness Technology to a Martian Lander Concept
Paul Sharp,Royston Jones - Altair Engineering Limited, Richard Slade - Astrium Limited

Optimization and robustness technologies provide a gateway for the rapid assessment of an engineering design. Following the development of a design concept, optimization technology can automatically modify design variables of the system (i.e. airbag geometry, vent area etc.) to achieve the optimum performance characteristics. Once the design has been optimised, a robustness assessment can be performed. This culminates in the determination of a probability value which provides a scientific basis to quantify the success of a design concept. Many industries require the risk of an engineering operation to be quantified in order to convince licensing authorities or key decision makers. There are fewer clear cut cases where a design is required to perform in an alien environment (i.e. wind velocity, rock height, pitch attitude etc.). The paper showcases new and innovative technology available in Altair HyperStudy to determine optimization and robustness assessments using a minimum amount of LS-DYNA runs.
The influence of bird-shape in bird-strike analysis
S.C. McCallum, C. Constantinou - BAE SYSTEMS

This paper describes the results of simulations to assess the influence of bird shape during bird-strike. In the first part of this paper, simulations are presented which compare the results of a traditional bird shape model (hemispherical ended cylinder) impacting a square flat panel using the ALE and SPH techniques. In each case the bird is modelled with a mass of 8 lb and has physical dimensions (torso) representative of a Canadian goose. The simulation results show close agreement with one another for stagnation pressure and displacement of the panel. Biometric data obtained from the IBRG (International Bird-Strike Research Group) is then used to construct a more detailed bird model of a Canadian goose that includes multi-material parts. The model is simulated using SPH and compared to the results of the hemispherical ended cylinder. The simulation results obtained using this new bird model indicates that a target may become pre-stressed from the initial impact of the head and neck, prior to the impact of the torso. This may have an important consequence for damage initiation and failure of the target.
The Optimization of the LSTC Hybrid III Dummies to enhance the numerical stability and to fulfill the current standards
Wolfgang Lietz - CAD-FEM GmbH

• Many years ago LSTC developed Hybrid III-Dummies. One group of these have on the outer surface deformable parts. The dummies are free and without charge for user’s of LS-DYNA. • In the last years on on hand the dummies changed and on the other hand the expectations on the dummies were growing. • This paper describes the the overall validation and optimization process of the whole dummy and in detail the optimization work for the neck validation of the 95% Dummy.
The thick shell element type 3
Andre Stühmeyer - CAD-FEM GmbH
The use of an Oasys PRIMER model management database during accelerated vehicle development programs such as the 2005 Ford GT
Tim Keer, Simon Iregbu - Arup

The role of CAE (Computer Aided Engineering) in the automotive vehicle development process continues to grow in importance. CAE has been one of the key enablers in the recent reduction of vehicle development times, as it allows less reliance on time-consuming and costly prototype testing. Impact CAE has been at the forefront of this CAE revolution. Various additional factors continue to place increased demands on the impact CAE team: The increased number of loadcases required to be analyzed (side o impact alone can require analysis of FMVSS214, SINCAP, IIHS, ECER95 barrier, FMVSS201 pole and EuroNCAP pole impacts, as well as additional OEM-specific loadcases) The increased use of a single underbody for multiple vehicles (e.g. a o sedan and a wagon) The need to analyze different vehicle options (e.g. different powertrains o for front impact; an optional sunroof for side impact) The increased detail in today’s models (in terms of the number of o components modeled as well as the number of elements in the model) Analysis is increasingly expected to be the active driver of the vehicle o design process, not just a passive predictor of performance These factors have combined to place increased pressure on CAE engineers to achieve rapid creation of multiple loadcases for multiple vehicle options. This paper describes a process for management of impact CAE models during vehicle development programs. It is based around the Oasys PRIMER model management software. Arup used this process during the development of the 2005 Ford GT (see Figure 1). Arup performed all the structural CAE for the Ford GT, working for Mayflower Vehicle Systems and Ford Motor Company. The design and analysis of this vehicle has been described elsewhere (Reference 1) and is not repeated here. In this paper, the discussion is limited to the use of Oasys PRIMER Databases and Templates.
Tool Design for a High Strength Steel Side Impact Beam with Springback Compensation
Trevor Dutton - Dutton Simulation Ltd, Richard Edwards, Andy Blowey - Wagon Automotive Ltd

Prediction of formability for sheet metal pressings has advanced to a high state of confidence in recent years. The major challenge is now to predict springback and, moreover, to assist in the design of tooling to correctly compensate for springback. This is particularly the case for materials now being routinely considered for automotive production, such as aluminium and ultra high strength steels, which are prone to greater degrees of springback than traditional mild steels. This paper presents a case study based on the tool design for an ultra high strength steel side impact beam. The forming and springback simulations, carried out using eta/DYNAFORM (based on the LS-DYNA solver), are reported and compared to measurements from the prototype panels. The analysis parameters used in the simulation are presented, and the sensitivity of the results to variation in physical properties is also reviewed. The process of compensating the tools based on the analysis prediction is described; finally, an automated springback compensation method is also applied and the results compared with the final tool design.
Topology optimization in crashworthiness design
Larsgunnar Nilsson - Engineering Research Nordic AB and University of Linköping, Jimmy Forsberg - University of Linköping

Topology optimization has developed rapidly, primarily with application on linear elastic structures subjected to static loadcases. In its basic form an approximated optimization problem is formulated using analytical or semi-analytical methods in order to perform the sensitivity analysis. When an explicit finite element method is used to solve contact-impact problems, the sensitivities cannot easily be found. Therefore, an alternative formulation for topology optimization is investigated in this work. The fundamental approach is to change the element thicknesses based on the internal energy density distribution in the structure. Within this formulation it is possible to treat nonlinear effects, e.g. contact-impact and plasticity.
Using LS-DYNA Implicit for Metal Forming Applications
Cleve Ashcraft, Roger Grimes, Xinhai Zhu - LSTC
Validating Material Information for Stochastic Crash Simulation Part 1: Quasi-Static Properties
P.K.C Wood, C. A. Schley, S. Kenny - University of Warwick, T. Dutton - Dutton Simulation

This paper describes the steps in validating material information for stochastic simulation using a quaisi-static tensile test experiment. Sources of physical noise usually present in a testing environment such as variation in material properties, geometry and boundary conditions are included as inputs to Finite Element models. This work is carried out in the context of a research project supported by the Automotive Industry in the Midlands. The broad aim of the project is to establish a material properties validation process for crash simulation. Stochastic models of representative components and small assemblies in a vehicle structure, in addition to tensile testing of coupons, will be created and will form an essential part of the verification process. All models will be validated through experimental testing and these investigations will establish variations in material properties and the significance of dependencies such as strain rate and form induced thinning. Stochastic simulation is a CAE tool, enabling the support of robust engineering design. Robust engineering design is viewed as an essential part of automotive product development.
Vehicle Roof Crush Modelling & Validation
Mingzhi Mao, E. C. Chirwa,T. Chen - The University of Bolton, UK

Real roof crush tests, quasi-static or dynamic, have been widely used to evaluate the safety integration of vehicle structure, especially in the USA, where there are specified standards such as FMVSS 208 and 216. Europe is endeavouring to reach the same target for vehicle safety taking into account the different road condition. However, carrying out full experimental tests is shown to be costly and in many cases unrepeatable. That is why the development of good reliable models can be the key to the solution of successful roof crush simulation that predict real world accidents. For this particular paper, the modelling was partially carried out in Radioss FE model and then translated into LS-DYNA3D. The complete model was finalised in LS-DYNA3D, where it was made available for the roof crush simulations. To improve the structural integrity, spotwelds were remodelled and new Nodal_Rigid_Bodies were built-in manually due to the different definitions and interpretations in these two codes. Roof mesh refinements were done in order to remove roof stiff behaviour in some areas and therefore match the roof deformed pattern shown in real test. Local Cartesian coordinate system was established for rigid planes’ spatial position. In addition, time integration algorithms in LS- DYNA3D were also discussed for roof crush prior to performing quasi-static and dynamic simulations on a small European car. Thereafter the results were verified against the real tests which showed very good agreement, especially in the time history crush characteristics. However, despite the force peak values to be nearly the same there is still a small discrepancy between the quasi-static roof crush simulation and its real test characteristic.
WorldSID 50th The Next Generation Side Impact Dummy
Bhavik Shah, Yi Liu - FTSS