6th European LS-DYNA Conference

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

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

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

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

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

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

• A New Impact Scenario for P-V Tram Certification

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

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

• Accurate and efficient dummy models for occupant safety design
• Advanced Finite Element Model for AE-MDB Side Impact Barrier

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

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

• Advanced Simulations of Cellular Structures with LS-DYNA

  Matej Vesenjak, Zoran Ren - University of Maribor

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

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

  Rudolf Bötticher - TMB GmbH

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

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

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

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

• ALE Modeling of Surface Waves

  AQUELET Nicolas - Livermore Software Technology Corporation

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

• ANSA PRE PROCESSING FOR LS-DYNA

  Alexandros Kaloudis - BETA CAE Systems SA

• Application of Shell Honeycomb Model to IIHS MDB Model

  Shigeki Kojima - TOYOTA TECHNICAL DEVELOPMENT CORPORATION, Tsuyoshi Yasuki, Koji Oono - Toyota Motor Corporation

  This paper describes a new finite element modeling method of Aluminum honeycomb using shell elements. It is our new modeling method that cell size of honeycomb structure is enlarged to increase time step size for FEM analysis, and compressive strength is controlled by thickness of shell elements. New modeling method was applied to IIHS moving deformable barrier model, and side impact analysis with a full vehicle model was performed. The result of simulation using a new barrier model showed much better correlation with a test result than previous simulations.

• Concept Design of an A-Pillar Mounted Airbag for Pedestrian Head Protection

  Jianfeng Yao, Jikuang Yang - Chalmers University of Technology

  Accident investigations have shown that in pedestrian-versus-vehicle accidents, windshield edges, A-pillars, cowls are the main sources for severe head injuries due to their high stiffness. To mitigate head injury severities, it is necessary to improve the safety performance of these structures. An A-pillar mounted airbag system (AMAS) was devised with the aim to prevent head from directly impacting against stiff structures such as A-pillars, windshield frames and edges. The airbags of the AMAS are installed inside A-Pillars. When a car strikes with a pedestrian, the airbag will break the A-Pillar cover and deploy along the whole APillar to cover the stiff structures. In this study, the safety performance that can be provided by this system was evaluated by mathematical simulations. A finite element (FE) Ford Taurus car model and an EEVC headform model were used to simulate the pedestrian headform tests as proposed by EEVC. FE airbag models were developed and the influence of airbag parameters, including airbag type, inflow mass rate, vent size and deploy timing, were investigated by mathematical simulations. The safety performance of the AMAS was also evaluated by an FE human head model. The results show that this system can greatly reduce the head injury severity in case a pedestrian head impacts with A-pillar areas.

• Contact and Sliding Simulation of Rubber Disk on Rigid Surface with Microscopic Roughness

  Sunao Tokura - JRI Solutions, Ltd.

  It is crucial to obtain detailed information about frictional interaction between tire and road surface to estimate performance of vehicle brake system or tire on real road surface. Simulation using Finite Element Method (FEM) in addition to experimental procedure is regarded to be useful to investigate contact behavior between tire and road surface. However, indeed, it is difficult to apply FEM simulation for such a problem since contact and sliding of rubber on rough rigid road surface may cause local large element distortion on rubber material and simulation may fail by negative volume error. In this paper, modeling of a rubber disk and rigid road surface with microscopic roughness, which can be used as a baseline for simulation of contact behavior between tire and road surface, is described. Some investigation for analysis technique to ensure stable computation of rubber disk and road surface model under severe condition has been made. It was shown that proposed modeling technique could avoid extreme mesh distortion during simulation. It is expected that the proposed technique can be used in simulation of rolling/sliding tire on real road surface.

• Corpuscular method for airbag deployment simulations

  Lars Olovsson, IMPETUSAfea AB

• Current features and developments of LS-PREPOST

  P. Ho - Livermore Software Technology Group

• Deployment Simulations of Space Webs

  M. Gärdsback, G. Tibert - Royal Institute of Technology

• DEVELOPMENT AND EVALUATION OF A CONTINUUM NECK MUSCLE MODEL

  S. Hedenstierna, P. Halldin, K. Brolin - Royal Institute of Technology, Stockholm, Sweden

  The Finite Element method is a powerful tool for analyzing the biomechanics of the human body. One area that has attracted increasing attention is the cervical musculature and its influence in neck injury mechanisms. Most cervical FE models of today use spring-elements as muscles and are limited to discrete geometries and nodal output results. A solid-element muscle model however, will improve the geometry and add properties such as tissue inertia and compressive stiffness. It also enables analysis of element stresses and strains within the muscular tissue. The aim of this study was to determine how a continuum muscle model influences the impact behavior of a human neck FE model compared to a discrete muscle model. The 3D geometries of the neck muscles were digitized from MR images of 50th percentile males and positioned relative to the KTH FE neck model in line with anatomical data from the literature. The muscles were modeled using solid finite elements and a non-linear, viscoelastic continuum material model. The behavior of the new muscle model during impact was compared to an existing discrete muscle model for frontal, rear-end, lateral and oblique impacts. The continuum muscle model stiffened the response of the KTH neck model and improved the boundary conditions for the vertebral column compared to a discrete model.

• DEVELOPMENT OF ADVANCED HUMAN MODELS IN THUMS

  Masami Iwamoto, Yuko Nakahira, Atsutaka Tamura, Hideyuki Kimpara, Isao Watanabe, Kazuo Miki - Toyota Central R&D Labs., Inc.

  A finite element model of human body called THUMS has been developed to predict gross motions and multiple skeletal injuries of a whole human body during impacts. Recently, we have developed a head/brain model and thoracic/abdominal internal organ models to evaluate more severe injury risks for occupants and pedestrians in automotive accidents. The head/brain model was validated against some test data on translations and rotations of the head obtained from the literature. The internal organ models were validated against hub impacts for the thorax or abdomen. These models are currently attempted to predict severe injuries in the brain and liver, etc. Finally, we will show THUMS family including a small female, a large male, and a child, etc, which have been developed to investigate the effects of body size on impact responses and injuries.

• Development of BioRID II Dummy Model using Stochastic Methods

  Sebastian Stahlschmidt, Bastian Keding, Katharina Witowski, Heiner Müllerschön, Uli Franz - DYNAmore GmbH, Stuttgart, Germany

  Consumer and insurance organizations use the BioRID II dummy as test device to assess the risk of whiplash injuries in rear crash scenarios. DYNAmore GmbH developed a finite element model for LS-DYNA of the BioRID II dummy in cooperation with the German Automotive Industry (FAT). The project follows the updated development guidelines of successfully developed models for the FAT in previous projects. This paper describes the applied development methodology, modeling techniques and the current model. Due to significant pre-stress in the dummy and other new features the modeling requires LS-DYNA 971. An outline of the good performance of the model release 2.0 in various validation tests is presented. The paper concludes with results from robustness investigations performed with LS-OPT.

• Development of validated Finite element model of an articulated truck suitable to simulate collisions against road safety barriers

  M. Pernetti - Second University of Naples, S. Scalera, G. Cibllis - University of Naples "Federico II"

  Crashworthiness is one of the most important aspect which is taken into account in road design. The effectiveness of Finite Element Method (FEM) to solve major design problems and as a tool to perform parametric studies, has been plainly demonstrated in literature. Of course this is possible only when available models of vehicles and devices are calibrated in a wide range of impact conditions. This research, was intended to develop a well defined multipurpose finite element model of an articulated truck. The model has been set up taking into account two real test impacts, the first against a concrete wall and the second against a steel bridge safety barrier. The fundamental steps of the modelling process will be described along with any requirements needed to reproduce the two full scale tests. The results obtained demonstrate that the modelling processes of vehicle and safety devices were accurate and that, in particular, the articulated truck FE model is suitable for a wide range of impact conditions. As a conclusion, the validated model is reliable to foresee the impact behaviour without needing expensive crash tests.

• Development of validated Finite element model of a rigid truck suitable to simulate collisions against road safety barriers

  M. Pernetti - Second University of Naples, S. Scalera - University of Naples "Federico II"

  The effectiveness of FEM (Finite Element Method) to improve the crashworthiness, both of the vehicle and of the road safety hardware, has been plainly demonstrated in literature. As well known, such a methodology can be successfully employed (i) as a support to design novel devices and (ii) as a tool to perform parametric studies to assess the influence of different factors. Of course this is possible only when available models are calibrated in a wide range of impact conditions. In this work, a well detailed finite element model of a rigid truck is presented. The model has been validated through an extensive comparison with two full scale impact tests, the first against a concrete wall and the second against a road safety steel barrier. The excellent agreement attained when simulating the abovementioned impacts, characterized by noticeably different nature, demonstrates that the modelling processes of the vehicle and devices were accurate and that, in particular, the FE model of the Heavy Good Vehicle is suitable for a wide range of impact conditions. As a conclusion, the validated model is reliable to predict the impact behaviour without needing expensive crash tests.

• Developments in Occupant and Seat Modelling with Primer 9.3

  Miles Thornton, Richard Sturt, Chris Bell - Arup

  There is constant pressure to reduce the time needed to process design data into crash results (mesh, assemble, create different crash cases, check, run, post-process). The meshing step has been reduced by batch meshing technology, and progress has been made in several other areas such as automatic post-processing. Attention is now turning to the remaining bottlenecks, which include occupant and seat positioning. These steps require careful manual work and cannot currently be automated. The problem is magnified by the large number of seat position/dummy combinations. • It is intended that Primer Version 9.3 will solve these problems, by providing fast methods of dummy positioning, seat positioning, seat foam compression, and belt fitting.

• DOE SENSITIVITY ANALYSIS WITH LS-OPT AND VISUAL EXPLORATION OF DESIGN SPACE USING D-SPEX

  Katharina Witowski, Heiner Muellerschoen, Marko Thiele - DYNAmore GmbH, Uwe Gerlinger - AUDI AG

  This paper describes the approach of a DOE (Design of Experiments) sensitivity analysis using LS-OPT in conjunction with AURA for simulating the radiation of a diesel particle filter. The process flow from preprocessing to the visual evaluation of the results using the D-SPEX (Design SPace EXplorer) software is presented. For the purpose of this sensitivity analysis the geometrical arrangement as well as polynomial curves from the AURA input had to be parameterized. Further more various discrete and coupled scalar parameters where used in this investigation.

• Effects of Mesh Size and Remapping on the Predicted Crush Response of Hydroformed Tubes

  Guillaume D'Amours, Ahmed Rahem - National Research Council of Canada, Robert Mayer - General Motors Technical Center, Bruce Williams - University of Waterloo, Michael Worswick - University of Waterloo

  Crashworthiness simulations can be useful tools in vehicle design. According to Du Bois [1], there are many factors which affect the reliability of crashworthiness models. Especially, the mesh size and the mapping of forming results into crash models. Few studies have analyzed the mesh size effect with forming results on the crashworthiness of frame components. This paper presents an analysis of crush response of hydroformed aluminium tubes from both experiments and finite element simulations. The predicted crush response for tubes meshed with different mesh sizes for hydroforming with results transferred to the crash simulations will be firstly shown. Predicted mean crush forces will be compared to measured ones. Thereafter, forming results were remapped on a secondary model, having coarser mesh sizes for crush simulations, with the LS-DYNA option called *INCLUDE_STAMPED_PART. Results show that in certain instances, it may be better to use a fine mesh size for the hydroforming models and remap forming results to coarser mesh sizes for crashworthiness models to save computational time.

• ENHANCEMENTS IN DUMMY MODEL DEVELOPMENT AND OUTLOOK

  Jim Rasico, Fuchun Zhu - First Technology Safety Systems, Inc., USA, Robert Kant, First Technology Safety Systems Europe, The Netherlands

  It has been almost 11 years since FTSS introduced the Hybrid III 50th dummy finite element model in 1996. From their inception, Finite Element dummy models were constrained in size and accuracy by the computational resources and modeling capabilities of the time. In recent years, the numerical simulation and analysis industry has benefited from the advanced computing technology and finite element modeling techniques. Today the latest technologies are being utilized to further improve the dummy model accuracy, and stability. A key requirement for new models is to achieve a level of geometric accuracy unattainable a decade past. The new CAD data source for FE models is derived from 3-D laser and X-ray scanned geometry to ensure the accurate representation of hardware geometry both externally and internally. New material testing is being utilized to compliment existing data sets and allow for the replacement of simple material models with more complex/realistic definitions. Experiments with oblique loading conditions have been designed to further enhance the FE model. This data will allow validation in conditions experienced by many dummy model users. Additional tests will be carried out to examine different impact pulses to attain the highest level of dummy model performance verification. These advanced technologies are being implemented in the dummy models to further improve their quality.

• Enhancements in dummy model development and outlook

  Jim Rasico, Fuchun Zhu, Robert Kant - First Technology Safety Systems, Inc.

  It has been almost 11 years since FTSS introduced the Hybrid III 50th dummy finite element model in 1996. From their inception, Finite Element dummy models were constrained in size and accuracy by the computational resources and modeling capabilities of the time. In recent years, the numerical simulation and analysis industry has benefited from the advanced computing technology and finite element modeling techniques. Today the latest technologies are being utilized to further improve the dummy model accuracy, and stability. A key requirement for new models is to achieve a level of geometric accuracy unattainable a decade past. The new CAD data source for FE models is derived from 3-D laser and X-ray scanned geometry to ensure the accurate representation of hardware geometry both externally and internally. New material testing is being utilized to compliment existing data sets and allow for the replacement of simple material models with more complex/realistic definitions. Experiments with oblique loading conditions have been designed to further enhance the FE model. This data will allow validation in conditions experienced by many dummy model users. Additional tests will be carried out to examine different impact pulses to attain the highest level of dummy model performance verification. These advanced technologies are being implemented in the dummy models to further improve their quality.

• Evaluation of rail height effects on the safety performance of W-Beam barriers

  Dhafer Marzougui, Pradeep Mohan, Cing-Dao (Steve) Kan - The George Washington University, USA, Kenneth Opiela - US Department of Transportation, USA

  The objective of this study is to investigate the effect of rail height on the safety performance of G4(1S) w-beam guardrail systems. The study involved three steps. In the first step, a detailed finite element model of the G4(1S) guardrail system was created. The model incorporated the details of the rail, connections, the post, the blockout, and the soil in which the post was embedded. To validate the model of the wbeam guardrail system, a model of the setup of this w-beam system in previous fullscale crash tests was created. Simulations were performed using this model and the results were compared to the full-scale crash test data. The results were similar indicating that the model was an accurate representation of the actual system. In the second step of the study, the validated model served as the basis for four additional models of the G4(1S) guardrail to reflect varying rail heights. In two of the four models, the rails were raised 40 and 75 mm (1.5 and 3 inches). In the other two models, the rails were lowered 40 and 75 mm. Simulations with these four new models were carried out and compared to the first simulation to evaluate the effect of rail height on safety performance. The simulation results indicated that the effectiveness of the barrier to redirect a vehicle is compromised when the rail height is lower than recommended. The third step of the study consisted of performing full-scale crash tests with the guardrail at standard height and 60 mm (2.5 inches) lower. The data from the crash tests validated the simulation results.

• EVOLVING TECHNOLOGY: MULTI-PHASE, MULTIMATERIAL, ALE APPROACH AND TOOL DEVELOPMENT FOR BURIED BLAST SIMULATION

  Dr. Rahul Gupta - U.S. Army Research Laboratory Aberdeen Proving Ground

  Modeling the response of structures subjected to blast from shallow buried explosives poses a challenge, primarily due to the inherent coupled interaction. The response of the structure affects the surrounding blast pressure field, which in turn, affects the loading on the structure; therefore the problem is coupled in nature. The problem is complicated due to the difference in time scales associated with the blast loading and structural damage. Damage mechanisms such as structural collapse generally occur later compared to the duration of the blast since the duration of the failure event is much longer. In this presentation, an evolving methodology, combining the effects of early coupled interaction and later structural damage, Fluid-Structure Interaction (FSI) effect using multi-material and multi-phase Arbitrary Lagrangian Eulerian (ALE) formulation is described. The utility of the methodology is demonstrated through a newly developed toolset for LS-DYNA ALE based simulation and an example involving blast loading on a highfidelity plate structure supported through Vertical Impulse Measurement Fixture [VIMF]. Data from the experiment is compared with the LS-DYNA ALE simulation to investigate the efficacy of the methodology. Results reveal that this new analysis tool yields accurate results that will be useful in predicting vehicle response and provide a means of quickly iterating on proposed structural solutions.

• Experience from using recently implemented enhancements for Material 36 in LS-DYNA 971 performing a virtual tensile test

  Michael Fleischer - BMW Group, Thomas Borrvall - Engineering Research Nordic AB, Kai-Uwe Bletzinger - Technische Universität München

  In today’s automotive industry the development of car bodies considerably depends on the use of computer-aided tools to meet the challenges of rising product complexity and growing number of variants. Today, enabled by modern simulation software, improved material models and numerical methods, simulation has become essential for the evaluation of sheet-metalstamping processes before press tools are manufactured. Though modern material models are available, some effects are not described correctly, because some parameters are assumed to be constant. In reality, a lot of these “constant” values must be considered variable. To better represent the real material behaviour, some enhancements for the standard material models have to be implemented to get a more realistic simulation. In this paper we present the results of virtual tensile tests, comparing input- and outputparameters, using the first LS-DYNA material model with variable Lankford coefficients / R-values, yield curves, volume and Young’s modulus. All these features are now available in one material model – LS-DYNA 971 Material 36.

• Fan Blade Bird Strike Analysis Using Lagrangian, SPH and ALE Approaches

  Alexander A. Ryabov, Vladimir I. Romanov, Sergey S. Kukanov - Sarov Engineering Center, Yuriy N. Shmotin, Pavel V. Chupin - NPO Saturn

  Fan blade bird resistance is one of the most important certification requirements for modern jet engines. The development test to meet the requirement is difficult and costly experiment. The expenses can be significantly reduced by using the numerical simulation of fan blade bird strike problem in the design of jet engine. The common technique for such simulations is modeling of bird as a solid cylinder or ellipsoid with material properties similar to water. The paper presents some results of fan blade bird strike analysis using LS-DYNA Lagrangian, SPH and ALE approaches to model the bird. The main objectives of the investigations are to compare the results obtained by means of different approaches and to find out the advantages and disadvantages of every approach.

• FE-MODELING OF SPOTWELDS AND ADHESIVE JOINING FOR CRASHWORTHINESS ANALYSIS

  A. Haufe , G. Pietsch - Dynamore GmbH, Germany, M. Feucht, S. Kolling - DaimlerChrysler AG, Germany

  The increasing demands with regard to the predictive capabilities and the exactness of crash simulations require more and more investigations into numerical models in order to capture the physical behavior reliably. Steps towards this goal are the usage of finer meshes which allow for a better geometrical representation and more sophisticated material models which allow better prediction of failure scenarios. Another important playground towards improved crash models is the area of connection modeling. Validation in this area is usually closely related to very detailed models which cannot be easily translated into a crash environment due to time step restrictions. Therefore, representative substitute models have to be developed and foremost validated. The aspect that failure of the connections has to be considered as well adds another dimension to the complexity of the task. The present paper highlights the conflict between predictive capability, capture of physical reality and manageable numerical handling. Another aspect of the paper is the attempt to raise the awareness of the topics verification and validation of numerical models in general. This concept is illustrated using latest developments for modeling of spotwelds and adhesive bonding in LS- DYNA.

• FE-MODELLING OF HYDRODYNAMIC HULL-WATER IMPACT LOADS

  Ivan Stenius, Anders Rosén - KTH Centre for Naval Architecture

  This paper considers finite element modelling of the hydrodynamic loads in hull-water impacts. The commercial FE-code LS-DYNA is used with a multi-material arbitrary Lagrangian-Eulerian formulation and a penalty contact algorithm. The great advantage of this modelling technique is that it enables the modelling of the instantaneous fluidstructure interaction. A difficulty is however the selection of appropriate modelling parameters. A method to rationally select appropriate modelling parameters is discussed and briefly described. Convergence of the pressure distribution is presented and discussed. Pressure distributions and loads are favourably compared with other theoretical methods and with experiments.

• Finite element analysis of Polymer reinforced CRC columns under close-in detonation

  Benjamin Riisgaard NIRAS Consulting Engineers, Denmark, Anant Gupta, Priyan Mendis, Tuan Ngo - The University of Melbourne

  Polymer reinforced Compact Reinforced Composite, PCRC, is a Fiber reinforced Densified Small Particle system, FDSP, combined with a high strength longitudinal flexural rebar arrangement laced together with polymer lacing to avoid shock initiated disintegration of the structural element under blast load. Experimental and numerical results of two PCRC columns subjected to close-in detonation are presented in this paper. Additionally, a LS-DYNA material model suitable for predicting the response of Polymer reinforced Compact Reinforced Concrete improved for close-in detonation and a description of the LS-DYNA multi-material Eulerian method for modeling the blast event is also presented in this paper.

• Fluid Structure Interaction for Immersed Bodies

  Jason Wang, Hao Chen - Livermore Software Technology Corporation

  A new method for automatically constructing the coupling surface along shell edges is developed. By using this new "edge" option together with "shell thickness" option in the *CONSTRAINED_LAGRANGE_IN_SOLID card, we can accurately model problems involving shell structures with leading edges cutting into ALE materials. Engineering problems include bird striking at propulsion system fan blades; helicopter impacting water. This new feature is implemented in the latest LS-DYNA 971 release 7600 and ready to use with minor input deck modifications. Before, in order to correctly model the FSI, blades had to be meshed by using Lagrange solid elements. This approach can ensure an accurate coupling interface but the time step size is greatly reduced due small element sizes. The lengthy running time for the problem makes this approach impractical. The new "edge" and "thickness" feature will construct a proper coupling surface from shell elements and provide reasonable time step sizes for the simulations.

• Forming of alloy plate by underwater shock wave of explosive

  K. Kuroda, H. Hamada, H. Hamashima, S. Itoh - Kumamoto University, Japan

  The fuel cost and efficiency of the automobile greatly depend on the weight. Researches for light weight automotive components are actively being performed, and automobiles using Aluminium alloys instead of steel are becoming more common. However, Al alloys have limited formability in comparison with steel and its final shape is more limited. We have attempted to improve this limited formability of Al alloys by explosive forming technique, which is a particular material processing method. In this method, a shock wave is generated by an explosive and propagated through a suitable pressure medium, e.g. water or air, and deforms a metal plate. We performed numerical analysis using LS-DYNA3D, and compared the results to the experimental observations.

• HIGH VELOCITY IMPACTS SIMULATIONS WITH SPH METHODS IN LS-DYNA

  Gilles Mazars, Gabriel Desille, Vincent Lapoujade - CRIL Technology - Groupe ALYOTECH, Christian Durin - CNES

  Several high velocity impacts (HVI) can be simulated using the SPH method in LSDYNA. Space debris, whose quantity is on the rise, now pose a major threat to satellites. Effective impact models enable both the development of more efficient protections and the prediction of the damage that an individual HVI will cause to structures. This paper aims to provide advice and words of caution on how to best model such impacts but also presents an example of a user implemented EOS in a SPH model. Usually, in the simulation of an HVI on a plate, both projectile and target are modeled using SPH parts. Commonly, the target model uses a tied transition from the SPH impact zone to the lagrangian parts which represent the undamaged area. This method reduces the number of elements in the model and the calculation time. The advantages and limits of the SPH method are presented first. The influence of the SPH/LAG transition on the quality of results is then discussed. Third, the influence of several SPH parameters on numerical results is mentioned. The number of particles used through the target thickness is of special interest, having a profound effect on the rear face cloud occurring after a perforation. Space debris can collide with satellites structures at velocities exceeding 10 km/s. In these conditions, commonly used EOS, such as the Gruneisen, for example, can not represent the material behavior during the expansion phase. The contribution of a user implemented EOS are presented for a HVI on an aluminium plate. The results are compared with experimental data to define optimized configurations as a function of impact velocity.

• HPC Considerations for Scalable Multidiscipline CAE Applications on Conventional Linux Platforms

  Stan Posey - Panasas, Inc.

  This paper examines HPC workload efficiencies for sample multidiscipline LS-DYNA applications on a conventional HPC Linux platform with proper balance for I/O treatment. Model parameters such as size, element types, schemes of implicit and explicit (and coupled), and a variety of simulation conditions can produce a wide range of computational behavior and I/O management requirements. Consideration must be given to how HPC resources are configured and deployed, in order to satisfy growing LS-DYNA user requirements for increased fidelity from multidiscipline CAE.

• Image Based Meshing for LS-DYNA

  Brian Walker - Arup, Philippe Young - Simpleware

  Simpleware provides what is effectively a 3D photocopier: three dimensional replicas can be generated automatically based on scans. In parallel, computer simulations can be used to assess the suitability or performance of objects in operation. Simpleware's technology has opened up FEA and RP manufacturing to a variety of applications and research fields including: • Industrial reverse engineering • Research in materials and composites • Non-destructive evaluation (NDE) • Biomechanical Research • Implant design and manufacturing • Surgery simulation and planning • Forensics • Biomimicry Simpleware software can be used in conjunction with the “Oasys LS-DYNA Environment” to make an efficient toolkit for the creation and running of models in LS-DYNA.

• Implementation of a material model with shear rate and temperature dependent viscosity

  Mathias Vingaard, Benny Endelt, Jesper deClaville Christiansen - Aalborg University

  A material model with shear rate and, optionally, temperature dependent viscosity was implemented. Shear rate dependence is expressed with a Yasuda function and temperature dependence with an Arrhenius function. The functions were fitted to viscosity data from oscillatory rheometry of polystyrene. Validation of the viscosity function in the material model was done with a single element with prescribed shear rate and temperature. Steady state results from a Newtonian simulation of plane Poiseuille flow with the implemented user material model were found to be identical to results from a simulation with LS-DYNA's MAT_NULL. Flow through a 4:1 contraction with shear rate dependent viscosity was simulated explicit and compressible as well as implicit and incompressible. Reasonable agreement was found for pressure loss, inlet force and outflow velocity.

• IMPLEMENTATION OF A NOVEL SHIP SIDE STRUCTURE INTO A TANKER AND A ROPAX VESSEL FOR INCREASED CHRASHWORTHINESS

  Sören Ehlers, Kristjan Tabri, Nicole Schillo, Janne Ranta - Helsinki University of Technology

  The energy absorption of a novel ship side structure is numerically analysed. The structure is implemented into an ice going Tanker and a ROPAX vessel. The aim is to evaluate the benefits in crashworthiness of such an application over the existing conventional side structures. The collision simulations are performed with the explicit non-linear solver LS-DYNA up to the point of inner shell breaching. The obtained energy-penetration curves of the novel structure are then compared to energypenetration curves of the conventional structure. The novel sandwich structure results in clear benefits in terms of increased energy absorption during collision; 30 per cent for the Tanker, and about 50 per cent for the ROPAX. The applied failure criterion and mesh size dependency are also discussed.

• Increasing Initial Internal Energy of Air Elements near Explosive for Fluid-Structure Models of a Steel Plate Subjected to Non-contact Explosion

  Wen-Chih Li, Wen-Feng Yu, Ding-Shing Cheng - National Defense University

  This study was to simulate a steel plate subjected to non-contact explosion by using Arbitrary Lagrangian-Eulerian (ALE) algorithm of the LS-DYNA software. A 3-D Fluid-Structure interaction model was considered. The numerical result would be compared with S.D. Boyd’s experiment, which 250g Pentolite explosive detonated above a 5 mm thick steel plate. The Eulerian mesh for explosive and air and the Lagrangian mesh for steel plate and its supporting system were coupled together with overlap. The JWL equation of state and the linear polynomial equation of state were used for explosive and air respectively. A bilinear stress-strain relationship was assumed for the steel plate which was modeled with shell elements. By increasing initial internal energy of air elements near explosive with a temperature of 3000K, the maximum displacement of the midpoint of the steel plate from the ALE model for explosive with a standoff distance of 50 cm was improved from an error of -46.7% to 15.3% after compared with S. D. Boyd’s experiment in 2000. Besides, the maximum displacement for the case of explosive with a standoff distance of 25 cm can have an significant improvement with only 0.5% error.

• Innovative modeling capabilities in virtual.lab in view of cross attribute simulation

  Tom Van Langenhove, Cedric Canadas, Nick Tzannetakis, Christophe Liefooghe - LMS International

  To meet the challenge to support the development of an ever increasing number of vehicle models and variants with an optimal quality in the constantly decreasing resource and time requirements, companies are forced to increase the integration amongst and impact of the different simulation disciplines in the core vehicle design and engineering process. A proposed methodology is offered by LMS through the LMS Virtual.Lab Software suite proposing an integrated platform for body, chassis, engine and full vehicle engineering. Through its integration in Dassault Systemes PLM and Simulia solutions it tightly links multi-attribute simulation with vehicle design. Innovative assembly and modelling capabilities enable a unique bridge between the different vehicle attribute domains, being noise & vibration, durability, strength and crash/impact. The definition of a generic assembly, which can be even defined directly on the design model represented by CAD together with multi-solver modelling information, and a multi-solver pre/post environment seamlessly integrating leading crash, linear, and non-linear solvers (LS-DYNA, Nastran, Abaqus) allows an easy and thorough information and data sharing between the different disciplines, strongly increases the efficiency in creating subsystem and vehicle models and delivers optimal collaboration between design and engineering teams. This paper focuses on a comprehensive presentation of the methodologies employed, clearly demonstrates the aims and value that a multi-attribute PLM integrated solution brings, documented by real industrial examples and metrics.

• Interface ANSYS Workbench for LS-DYNA

  M. Hörmann - CADFEM GmbH

• Investigation into the rising air pressure inside the door during side impacts

  Michael Machens - Wilhelm Karmann GmbH, Thomas Wessels - FH Osnabrück

  A crucial point in side impacts is the rapid intrusion of the side structure of the door into the passenger compartment. In the initial stage of the crash it is essential to provide sufficient space between occupant and door trim to enable a proper unfolding of the side airbag. This problem can be alleviated by using the rising air pressure inside the door as an additional input for crash sensing. When combined with the common acceleration sensing on the centre tunnel or B-Pillar it is feasible to increase the sensitivity of the impact detection so that an earlier airbag triggering in side impacts can be achieved. However, because of the introduction of more demanding side impact test configurations this phenomenon still needs to be investigated. In the early development process side impact simulations are usually employed to estimate the available space for airbag unfolding. But these simulations have shown some discrepancies if kinematics of the door trim intrusion during the airbag unfolding phase is compared to the experiments. This can be attributed to a lack of consideration of the air inside the door. A method to simulate this phenomenon which incorporates fluid-structure interaction is given in LS-DYNA. Recent developments in this software allow the use of an Arbitrary Lagrangian-Eulerian (ALE) solver and therefore make it possible to simulate the airflow inside and out of the door during a side impact. Using this approach, the dynamic pressure distribution inside the door and the loss of pressure due to outflowing air was simulated. Within the scope of this study the predictability of the pressure signal recorded for crash sensing and the additional air-induced intrusion of the door trim which reduces space for airbag unfolding is investigated in comparison to the different side and pole impact experiments.

• LANDMINE PROTECTION OF ARMOURED PERSONNEL CARRIER M113

  Mads Berg Larsen, Niras Demex, Kasper Cramon Jorgensen

  This paper presents numerical analysis and full-scale test of a mine protected armoured personnel carrier M113 subjected to a detonation of a buried 5.56 kg C4 surrogate mine placed under the belly of the vehicle. The protection consists of granulated ceramics (CRUSHMAT) filled within the space between the bottom plate and a reinforced floor. The vehicle structure and mine protection are modelled with Lagrange elements and the mine and surrounding air with ALE elements. CRUSHMAT is modelled using material model 63 Crushable foam, where stress-strain behaviour is obtained with laboratory tests.

• LS-DYNA Data Management using Visual-Environment

  S.H. Shetty, V. Ganesan, S.C. Sivalingam, E. De Pommery, J.L. Duval - ESI Group

  Realistic Simulation is considered to be the most important part of Simulation Based Design (SBD) in the product development cycle. Realistic simulations can not be achieved just by using currently available CAE pre and post processing functionalities alone. Many of the complex requirements of CAE modeling need to be addressed by having a synchronized CAD and CAE environment. CAE analysts need a tool, which will allow them to control variables, manage data, adapt the changes, and transport across different disciplines of analysis such as Crash, Safety, NVH and Durability. ESI’s Open VTOS™ application called “Visual-Environment (VE)” provides such capabilities as a complete solution to SBD. VE is an integrated suite of pre-post, CAE data management tools synchronizing CAD and CAE. It also provides several contexts based on individual FE solvers. Visual-Crash DYNA (VCD) is for LS-DYNA model setup, Visual-Composer (VCO) is for model assembling and data management by linking CAD (Geometry) and FE (Physics). VCO and VCD allow managing LS-DYNA model data linking to corresponding CAD assemblies. It helps to adapt fast design changes, communicate the engineering changes back to design, and to track the models and solutions of multiple iterations. Visual-Safe is an advanced pre-processor for safety features, Visual-Mesh a general purpose meshing tool, Visual-Viewer (VVI)-a general purpose plotting and simulation application, Visual-Life Nastran (VLN) a general purpose pre processor for NASTRAN, Visual-Process Executive-an application for process customization and automation are the other contexts to name a few.

• LS-DYNA Features for Hot Forming

  Arthur Shapiro - LSTC

  LS-971 has several features to model the hot forming process. A thick thermal shell formulation for the blank allows modeling a temperature gradient through the thickness. The keyword, *MAT_ADD_THERMAL_EXPANSION, allows calculating thermal strains for all the mechanical material models. A user-defined flag is available to turn off thermal boundary conditions when part surfaces come in contact. A thermal oneway contact algorithm is available to more accurately calculate contact between a die zoned with a CAD type surface mesh when in contact with a uniform meshed blank. Thermal-mechanical contact user defined parameters allow modeling the coefficients of friction as a function of temperature and thermal contact resistance as a function of interface pressure. A new feature models bulk fluid flow through the die cooling passages.

• LS-DYNA Performance and Scalability in the Multi-Core Environment

  Gilad Shainer - Mellanox Technologies

  Efficient data transfer between clustered compute nodes is critical for balanced system performance. In a balanced system, the overall performance is equal to or greater than the sum of its components, while in a non-balanced system, the performance is less than the sum. The challenge of achieving balanced performance becomes more evident in multi-core environments. A multi-core environment introduces high demands on the cluster interconnect and the interconnect must handle multiple I/O streams simultaneously. In this paper we explore the benefits of InfiniBand high-speed connectivity solution for multi-core clusters, and show the scalability and efficiency of LS-DYNA on InfiniBand connected multi-core cluster platforms.

• LS-DYNA USED TO ANALYZE THE MANUFACTURING OF THIN WALLED CANS

  Joachim Danckert - Aalborg University

  The ironing process and the backward can extrusion process are widely used for the manufacturing of thin walled cans. In the ironing process the die is commonly made with a cylindrical die land and in backward can extrusion the punch is commonly made with a cylindrical punch land. LS-Dyna has been used in the analysis of the influence, which the die land and the punch land have. The results suggest that a small misalignment of the die land, respectively the punch land may cause the process to become unstable resulting in uneven can height and uneven can wall thickness. Simulations also suggest that it is possible, by making minor changes to the geometry of the die land respectively the punch land, to make the process significantly more robust with regard to the influence from a small misalignment of the land. The results obtained from the LS-Dyna simulations are in good agreement with experimentally obtained results.

• LS-OPT based identification of a user defined material model for distortional hardening with application to sheet forming processes with complex strain path changes

  Vladislav Levkovitch, Bob Svendsen - University of Dortmund

  Sheet metal forming involves large strains and severe strain path changes. Large plastic strains lead in many metals to the development of persistent dislocation structures resulting in strong flow anisotropy. This induced anisotropic behavior manifests itself in the case of a strain path change by very different stress-strain responses depending on the type of the strain path change. While many metals exhibit a drop of the yield stress (Bauschinger effect) after a load reversal, some metals show an increase of the yield stress after an orthogonal strain path change (so-called cross hardening). To model the Bauschinger effect, kinematic hardening has been successfully used for years. However, the usage of the kinematic hardening leads automatically to a drop of the yield stress after an orthogonal strain path change contradicting experimental results for materials exhibiting the cross hardening effect. Another effect, not accounted for in the classical elasto-plasticity, is the difference between the tensile and compressive strength, exhibited e.g. by some steel materials. In this work we present a phenomenological material model whose structure is motivated by polycrystalline modeling that takes into account the evolution of polarized dislocation structures on the grain level – the main cause of the induced flow anisotropy on the macroscopic level. The model considers besides the movement of the yield surface and its proportional expansion, as it is the case in conventional plasticity, also the changes of the yield surface shape (distortional hardening) and accounts for the pressure dependence of the flow stress. All these additional attributes turn out to be essential to model the stress-strain response of high strength steels subjected to non-proportional loading. The model is implemented into LS-DYNA via the user material interface. After an LS-OPT based parameter identification for a dual phase high strength steel with the help of one- and two-stage loading tests, we demonstrate the capability of the model to predict the spring-back in processes with complex strain path changes.

• MATHEMATICAL MODELLING OF THE EARLY PHASE DEPLOYMENT OF A PASSENGER AIRBAG – FOLDING USING ORIGAMI THEORY AND INFLATION USING LS-DYNA PARTICLE METHOD

  Krystoffer Mroz, Bengt Pipkorn - Autoliv Development AB, Sweden

  Initial evaluation of the particle method for mathematical out-of-position simulations was performed. The evaluation was carried out by means of static inflation and impactor tests. In the out-of-position load case, the occupant is initially positioned very close to airbag module and the interaction airbag-occupant occurs during the early deployment phase of the airbag. Thus a realistic representation of the folding pattern together with an explicit modelling of the gas flow and the non-uniform pressure distribution play an important role. The first folding step of a 3D passenger airbag concerns the flattening to a 2D shape. The method used in this study was based on mathematical origami theory. The method consists of an initial user specification of one or a few main constraint folds. The remaining creases, which are needed to flatten the 3D airbag to a 2D state with a minimum area loss, were generated using the origami theory. The actual flattening was performed by solving a nonlinear optimization problem. The subsequent folding of the flat 2D airbag into a housing module was carried out by commercially available software. In the mechanical impactor tests, the airbag was inflated with chest and head shaped impactors resting on top of the airbag. The tests were modelled using the particle method for the gas flow and the predictions from the models were compared to the results from the mechanical tests. Good agreement between predictions and test results were obtained. Next step will be to evaluate the method by means of airbag inflation with an occupant positioned close to the airbag.

• Methodology for Selection of Material Models for Plastics Impact Simulation

  Hubert Lobo - DatapointLabs

  The volume of plastics that are subjected to impact simulation has grown rapidly. In a previous paper, we discussed why different material models are needed to describe the highly varied behavior exhibited by these materials. In this paper, we cover the subject in more detail, exploring in depth, the nuances of commonly used LS-DYNA material models for plastics, covering important exceptions and criteria related to their use.

• MICROSTRUCTURE EVOLUTION AND MECHANICAL RESPONSE IN THE HOT STAMPING PROCESS

  Mats Oldenburg, Per Salomonsson - Luleå University of Technology, Paul Åkerström, Greger Bergman - Gestamp Hardtech AB

  In the manufacturing of ultra high strength boron steel components with the hot stamping process, it is of great importance that the final product will have the desired material properties. This is especially true for safety related automotive components. Often the preferred microstructure is a mix of martensite and bainite. In this work a model is developed and implemented in order to predict the austenite decomposition into ferrite, pearlite, bainite and martensite during arbitrary cooling paths. The model is based on Kirkaldy’s rate equations and later modifications by Li et al. After modification, the model accounts for the effect from the added boron and the effect of straining at high temperatures. The implementation is as part of a material subroutine in the finite element program LS-Dyna. The achieved volume fractions of microconstituents and hardness profiles in the analyses show good agreement with the corresponding experimental observations. The phase content affect both the thermal and the mechanical properties during the process of continuous cooling and deformation of the material. A thermo-elastic-plastic constitutive model including effects from changes in the microstructure as well as transformation plasticity is implemented in the LS-Dyna code. The model is used together with a thermal shell formulation with quadratic temperature interpolation in the thickness direction. The developed methods are used to simulate the complete process of simultaneous forming and quenching of sheet metal components. The implemented models are used in coupled thermo-mechanical analysis of the hot stamping process and are evaluated by comparing the results from hot stamping experiments. The results from simulations such as local thickness variations, hardness distribution and spring-back in the component show good agreement with experimental results. However, it is shown that the simulation of the final cooling stage relies on a correct modelling of contact properties and heat transfer.

• Model improvement during seat project

  Christofer Karlsson, Scania CV AB

  To help predict the behaviour of a seat assembly when performing a seat belt anchorage pull test (according to regulation ECE R14/05 and directive 76/115/EEC) a FE-model has been built and improved in several steps. To increase the accuracy of the simulation (quasi static), a number of modifications were made to the initial model. The adjustments include higher mesh density, allowing a better representation of the geometry. A tensile strength test has been performed on one critical component which showed a lower yield strength than that provided by the supplier which called for a model update. Physical tests have been carried out and simulation results have been compared to these tests. While doing so, the rails at which the seat is mounted on and the lock sleeves that keep the rails in its position were considered to be too week in the model. By incorporating thick shell elements, this issue was solved. It is believed that these combined modifications significantly improve the performance of simulating a pull test.

• Modeling Hailstone Impact onto Composite Material Panel Under a Multi-axial State of Stress

  M. Anghileri, L. Castelletti, A. Milanese, A. Semboloni - Politecnico di Milano, Italia

  Flying through a hailstorm is dangerous not only for the direct damages but also for the hidden damages which may concur to more serious accidents. In this work, hail impact onto composite structure under a multi-axial state of stress is investigated. Initially, a reliable model of a hailstone is developed referring also to the recent research on ice modelling. In parallel, a numerical model to predict delaminations in pre-stressed composite structures caused by low energy impacts is developed and validated against experimental data. Finally, the impact of the hailstone onto a composite structure is simulated.

• Modelisation of screen rupture during a mobile phone free fall

  C. Lacroix - Sagem Communication, Groupe Safran, France

  Sagem brand mobile phone enjoys a strong presence in world markets thanks to continuous technological innovations associated to a high level of quality. We will approach here the case of the mobile phone screen (LCD), major part of a mobile phone whose integrity must be ensured throughout the life of the product. The specifications sheet specifies strict standards concerning the shock resistance: LCD should not be damaged during a series of 2 X 10 falls at a determined height (corresponding to average human height). Answer of such requirements needs a best understanding and good analysis of the mechanical phenomena which appears in the LCD during the impact on the floor.

• Modelling Carpet for Use in Occupant Crash Simulations

  Dylan Thomas - Honda R&D Americas

  Prediction of occupant injury using crash simulations can require numerical representation of materials that are not normally included within the structural model. Intuitively, it makes sense that the carpet would be required to predict the tibia index during frontal crash events; however, there appears to be little published on the topic. The tibia index is an injury criteria that needs to be predicted during IIHS frontal offset occupant simulations, but is also be looked at during unbelted FMVSS 208 simulations. Since carpet behaves quite differently during compressive and tensile loading, a numerical representation that can stably capture both regimes during occupant modelling is needed. This paper outlines a method to model the carpet using a specific meshing method and two material models. Shell elements in combination with the *PIECEWISE_LINEAR_PLASTICITY material model are used to model the tensile load carrying capacity of the carpet, while brick elements with the *MAT_FU_CHANG_FOAM material model are used to represent the compressibility of the carpet. Validation of using this modelling method with test data is presented, as well as the application of the carpet model in larger occupant models.

• MODELLING OF MATERIAL BEHAVIOUR AND FRACTURE FOR ALUMINIUM ALLOYS WITH APPLICATIONS TO PLASTIC FORMING AND CRASHWORTHINESS

  Odd Sture Hopperstad, Torodd Berstad, Odd-Geir Lademo, Magnus Langseth - Norwegian University of Science and Technology

  Constitutive models and failure criteria for aluminium alloys have been formulated and implemented in LS-DYNA for corotational shell elements. The applications are largescale simulations of plastic forming and crashworthiness. The constitutive models include plastic anisotropy, non-linear isotropic and kinematic hardening, strain-rate effects and simple fracture criteria. A non-local instability criterion is used to determine the onset of strain localization. Predictions of plastic instability and fracture are mesh dependent. To reduce this problem, non-local thinning has been introduced. Some aluminium alloys exhibit the Portevin-Le Chatelier effect or serrated yielding. This is caused by negative steady-state strain rate sensitivity. A simple model for dynamic strain aging is included in the models to account for this phenomenon. Examples of the use of the models in prediction of formability, plastic forming, welded connections and crashworthiness are given.

• MPP DECOMPOSITION OF A SPH MODEL

  Jean Luc Lacome - LSTC Vincent Lapoujade Cril Technology – Groupe Alyotech

  SPH, Smoothed Particle Hydrodynamics, is a very efficient tool to model industrial problems where large deformations occur. However, one disadvantage of the SPH technique is the expensive cpu cost compared to standard Finite Elements. Using the MPP version of LS-DYNA allows users to handle large problems (more than a million of particles) in a reasonable time. Due to the meshfree nature of the SPH method, standard decompositions used for finite elements can sometimes lead to very bad speed-up of the code. Users have to be aware of some options and rules to define customized decompositions in order to minimize communications between processors and get very good load balancing. Two different models are presented. The first one is a pure SPH model of a high velocity impact of a sphere on a plate, the second one is a coupled FE-SPH model of a bird impacting a set of fan blades of an engine.

• Multi-Scale Modeling of the Impact and Failure of Fiber Reinforced Polymer Structures using DIGIMAT to LS-DYNA Interface

  L. Adam, R. Assaker and R. Ramaya - e-Xstream engineering S.A.

  This paper deals with the prediction of the overall behavior of polymer matrix composites and structures, based on mean-field homogenization. We present the basis of the mean-field homogenization incremental formulation and illustrate the method through the analysis of the impact properties of fiber reinforced structures. The present formulation is part of the DIGIMAT [1] software developed by e-Xstream engineering. An interface between LS-DYNA and DIGIMAT was developed in order to perform multi-scale FE analysis of these composite structures taking into account the local, anisotropic, nonlinear and strain-rate dependent behavior of the material. Impact simulations are performed on glass fiber reinforced polymer structures using DIGIMAT interface to LS-DYNA. These analyses enable to highlight the sensitivity of the impact properties to the fibers’ concentration, orientation and length.

• Multi-Scale Modelling of Textile Structures in Terminal Ballistics

  Rimantas Barauskas - Kaunas university of technology, Lithuania

  An efficient finite element model of the ballistic impact and perforation of the woven fabrics structures has been developed in LS-DYNA. The bullet has been considered as a deformable body in contact with the fabric package presented by interwoven yarn structure. The model of the weave has been created by presenting the multifilament yarns by thin shell elements the thickness of which represents the real thickness of yarns. The total model of the fabric has been developed by employing the multi-scale approach. The “woven” zone in the vicinity of the bullet impact has been joined with the uniform surrounding areas of textile presented by membrane elements. The junction between the two types of zones of the fabric has been performed by means of the tie constraint and by proper adjustment of material parameters ensuring the minimum cumulative wave propagation speed error along selected directions. The model has been verified by comparing the response of the structure with the reference solution obtained by solving the full woven structure model. Physical and numerical experiments have been performed in order to identify the material model parameters.

• New developments in LS-OPT Version 3.2

  Nielen Stander, Willem Roux - Livermore Software Technology Corporation

  An overview of LS-OPT features is given with special emphasis on the major new optimization features available in LS-OPT Version 3.2. These include GUI support for parameter identification, confidence intervals for individual optimal parameters, point plotting as an enhancement to 3-D metamodel plotting, matrix expressions, coordinatebased result extraction and retry features for job distribution

• New Developments in the Compression of LS-DYNA Simulation Results using FEMZIP

  Rodrigo Iza Teran, Clemens-August Thole, Rudolph Lorentz - Fraunhofer Institute for Algorithms and Scientific Computing SCAI

  The standard usage of simulation as part of the automotive design process and increased computer power has increased the demand on archiving resources. This data may be reused several times during the development process and reused later for new models. Compression of the simulation results reduces both the archive size and the access times. This is why FEMZIP was developed several years ago. FEMZIP was specially designed for the compression of crash simulation results. We report on the improvements of FEMZIP both in regard to speed and to compression factors. FEMZIP is now also available built into several postprocessors. This means that these postprocessors can read and process compressed files directly. As a consequence of the improvements in FEMZIP, the postprocessors can display the compressed files faster than uncompressed files.

• Numerical Modelling and Biaxial Tests for the Mullins Effect in Rubber

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

  The formulation, testing and numerical study of the Mullins effect on rubber are presented. Ogden first modelled the Mullins effect for studying the unloading in filled rubber. It has been extended here to include the Mullins effect on both unloading and subsequent loading. To demonstrate the Mullins effect experimentally, a new biaxial test, inflation of a plane circular membrane, is used. Some experimental test data are presented. An approximate solution, a relation between the inflation pressure and the displacement at the centre for the inflation of a plane circular membrane is presented. The test data and the approximate solution are used to determine the Mullins damage material constants. For more accurate study, the material constants can also be obtained through the combination of LS-DYNA, LS-OPT and the test data. The test data, analytical results and numerical results from LS-DYNA are shown. They agree with one another.

• OPTIMIZATION OF DESIGN PARAMETERS FOR A CONTACT SENSOR IN BUMPER-PEDESTRIAN IMPACT BY USING FE MODELS

  Sunan HUANG, Jikuang YANG - Chalmers University of Technology, Sweden, Rikard FREDRIKSSON, Autoliv Research, Autoliv AB, Sweden

  An active hood system was developed in Autoliv to minimize the head injury risk of pedestrians from impacts with car front. In order to detect the car-to-pedestrian impact in time, a contact sensor placed in the car bumper is needed. The stiffness of the bumper foam material is highly dependent on the environment temperature, which will result in unstable output from the contact sensor. A new pedestrian-bumper contact sensor was developed in Autoliv, in order to receive a stable output from the sensor at different temperatures. In this study, the new contact sensor was analyzed and evaluated by using a bumper FE model of a production car. A baseline bumper FE model was firstly developed and validated by using EuroNCAP lower legform impact tests on the production car bumper. In order to improve the safety performance of the bumper FE model, the bumper foam material was softened and the foam thickness was increased. At the same time, the location, boundary condition and material property of the lower stiffener was also adjusted. As a result, the improved bumper model can meet the acceptance requirements of the EEVC WG17 lower legform impact test. A human lower extremity FE model was developed and the safety performance of the improved bumper was further evaluated by using the human lower extremity FE model.

• Optional Strain-Rate Forms for the Johnson Cook Constitutive Model and the Role of the Parameter Epsilon_0

  Len Schwer - Schwer Engineering and Consulting Services

  A brief review of the standard Johnson-Cook model is presented. Three optional strainrate forms are introduced and calibrated to laboratory data for A36 steel. Next a brief description of the LS-DYNA Version 971 implementation of the new strain-rate forms, within the existing viscoplastic formulation of the Johnson-Cook model, is presented. Finally, all four calibrated strain-rate forms are exercised in single element uniaxial stress test simulations, and the results are compared with the A36 steel effective stress versus effective strain data at three different strain rates. The comparison of the calibrated model response to the quasi-static A36 steel data is used to illustrate the role & of the Johnson-Cook parameter ε 0 .

• Parameter identification for the simulation of debonding in honeycomb sandwich using LS-Dyna

  M Hörmann - CADFEM GmbH

• Performance of LS-DYNA with Double Precision on Linux and Windows CCS

  Yih-Yih Lin - Hewlett-Packard Company

  Although the majority of LS-DYNA jobs are simulated with single-precision arithmetic, the more accurate and robust double-precision arithmetic has to be used for certain situations. Currently, most public LS-DYNA benchmarks are with single precision and few with double precision. As a result, users often try to extrapolate the performance of LS-DYNA with double precision from that with single precision. This paper shows that such extrapolations are often misleading. Furthermore, a comparative performance study on LS-DYNA with double precision, using all of the industry standard processors—Intel Xeon, Intel Itanium, and AMD Opteron—and the two major operating systems—Linux and Windows CCS—is presented to provide users with information for choosing the right configuration to run LS-DYNA with double precision.

• Practical Optimization for Automotive Sheet Metal Components

  Xiao Chen, Omar Ghouati - Ford Research and Advanced Engineering Europe

  Forming simulation has now reached an acceptable level of accuracy. It is possible to predict the hardening, the thinning and required forces for sheet metal stamped parts and it is also possible to predict the geometrical defects such as springback, wrinkling and surface appearance problems. Sheet metal forming can therefore be used in a closed loop to help design of parts and required tools in order to achieve a pre-defined geometry and mechanical performance. The paper presents a practical optimization methodology applied to automotive sheet metal stamped parts. The goal is to automatically optimize tool geometry in order to achieve an optimal part. An optimal part is regarded as a part free of defects. The defects are classified in two categories: material and geometrical. Material defects prevent the forming of the parts which can be in the form of a premature failure or an excessive wrinkling. The geometrical defects prevent the formed part from being assembled to the body structure and are generally referred as “springback”. In order to establish this optimization methodology, available tools for optimization and automatic geometry modification were coupled to LS-DYNA [1]. A special attention was paid to the definition of the optimization problem: appropriate selection of design variables, definition of the response functions in order to characterize the possible part defects (material or geometrical) and specification of the required physical constraints. The developed methodology will be demonstrated on actual automotive components

• PROBABILISTIC ANALYSIS OF UNCERTAINTIES IN THE MANUFACTURING PROCESS OF METAL FORMING

  H. Müllerschön, D. Lorenz - DYNAmore GmbH, W. Roux - Livermore Software Technology Corporation, M. Liebscher, S. Pannier - TU Dresden, K. Roll - DaimlerChrysler AG

  The purpose of this paper is to account for uncertainties in the manufacturing processes of metal forming in order to evaluate the random variations with the aid of FEsimulations. Various parameters of the Finite-Element model describing the investigated structural model are affected by randomness. This, of course, leads to a variation of the considered simulation responses such as stresses, displacements, and thickness reductions. On this, for the simulation engineer basic questions arise regarding: (1) the dimension of the range of variation of the simulation responses (2) the significance/contribution of the (input) parameters with respect to specific responses and (3) the reliability of the process design with respect to constraints (failure, damage, requirements, ...). In order to find solutions to these questions several methodologies may be applied that are available in the commercial optimization software LS-OPT (Stander et al. [5]). Some of the methodologies, such as Monte Carlo simulation, meta model based Monte Carlo simulation, stochastic fields, are discussed in this paper and are demonstrated by means of a metal forming problem.

• Probabilistic Assessment of a Stiffened Carbon Fibre Composite Panel Operating in its Postbuckled Region

  D. Elder, R. Thomson - Cooperative Research Centre for Advanced Composite Structures Limited, Australia

  This paper presents a probabilistic study on the behaviour and buckling capacity of a thin shell carbon fibre stiffened panel operating in its postbuckling region. The paper is a part of the ongoing world wide research into this phenomena being conducted by the CRC-ACS and many other interested parties including the EU FP6 Project COCOMAT. The aim of the research is to develop proven design methods that will allow an increased specific strength of stiffened composite structures commonly used in the civil aviation industry. Unlike their metal counterparts which can be reliably designed to operate with postbuckled loads, the use of similar composite parts for primary structures has not yet been widely adopted by industry. This is mainly due to the relatively brittle nature of composites which prevents significant yield based load paths being developed local to the stiffened regions of the structure. Using LS-OPT and LS-DYNA the study explores the probabilistic variations of a COCOMAT panel using a stochastic analysis. The response of the panel was the peak buckling load and the design variables included uncertainties in material properties, manufacturing tolerances and geometric imperfections. It was concluded that three of the four ply angles require accurate orientation during placement to produce a panel that will exhibit good repeatability for experimental testing. In addition the available computational methods in LS-DYNA to simulate buckling are reviewed and compared through the testing of a small baseline model.

• Reduction of Acceleration Induced Injuries from Mine Blasts under Infantry Vehicles

  Ala Tabiei, Gaurav Nilakantan - University of Cincinnati, USA

  Anti tank (AT) mines and improvised explosive devices (IED) pose a serious threat to the occupants of infantry vehicles. The use of an energy absorbing seat in conjunction with vehicle armor plating greatly improves occupant survivability during such an explosion. The dynamic axial crushing of aluminum tubes constitutes the principal energy absorption mechanism to reduce the blast pulse transmitted to the occupant in this investigation. The injury mechanisms of both vehicle-occupant contact interfaces are simulated viz. vehicle seat upon the occupant’s torso and vehicle floor upon the occupant’s feet. Data such as hip and knee moment, femoral force, and foot acceleration is collected from the numerical dummy which simulates the occupant’s response. This data is then compared to injury threshold values from various references to assess survivability.

• Road Safety Devices Assessment for Sliding Motorcyclists Protection

  M. Anghileri, L. Castelletti, A. Milanese, M. Pirola, F. Pistochini - Politecnico di Milano, Italia

  Statistics show that the impact with a roadside safety barrier of a motorcyclist sliding on the pavement after an accident is potentially more dangerous than the accident itself. In recent years, in effort to avoid the most serious consequences, the approach to barriers design changed and specific devices have been introduced to improve motorcyclists’ safety. At LAST Crash Labs, the effectiveness of one of these devices was experimentally and numerically investigated. A good numerical-experimental correlation was obtained and, in view of that, it was concluded that the numerical approach is a rather reliable tool for the development of devices for motorcyclists’ protection.

• ROBUST PARAMETER DESIGN IN LS-OPT

  Willem Roux - LSTC

  Robust parameter design creates designs insensitive to the variation of specific inputs. The paper discusses the robust parameter design capability within the context of its implementation in LS-OPT version 3.2. The paper provides the following details: the fundamentals of robust parameter design, the design of experiments based methodology used in LS-OPT, and an example problem.

• Robustness Evaluation Crashworthiness Simulation Results

  Johannes Will - DYNARDO GmbH, Uli Stelzmann - CADFEM GmbH

  The numerical robustness of simulation results from explicit time integration is an important topic. We know for real world applications of passive safety and crashworthiness that we have some numerical noise, but the interesting question is if that really does influence significantly our simulation results. Furthermore, today the robustness of the designs against naturally given input scatter, in loading conditions, geometry or material become part of the virtual product development process. Then, the prognosis of the variation of important simulation results using stochastic analysis procedure is necessary. Again the question arises how much of the calculated variation is coming from numerical noise. The paper will present a procedure of numerical robustness evaluation using stochastic analysis to quantify the scatter of simulation results. Using coefficients of determination, a procedure of deselecting variation defined by correlation to physical input scatter and "undefined" variation is introduced. The breakthrough in practical application and the acceptance of stochastic analysis for robustness evaluations was achieved by using linear and quadratic correlations and the corresponding measures of determination as well as by projection of statistical measures on the finite element structure.

• Rupture Modeling of Spot Welds Suitable for Crash FE Analysis in Vehicle Development Process

  Koushi Kumagai, Masakazu Shirooka, Jirou Ohachi, Toshirou Ogawa - Toyota Motor Corporation

  This paper describes the development of rupture modeling of spot welds suitable for crash FE analysis in vehicle development process. The authors presented a detailed spot weld rupture model called ‘spider web model’ in Toyota and confirmed that it closely correlates with actual full vehicle crash test results. Although, the spider web model is accurate, extensive effort is required to construct the model. Also, the spider web model can only simulate the nugget pullout mode of spot weld rupture and it cannot simulate the nugget fracture mode observed in the ultra high strength steels. Many investigations have been conducted on spot weld rupture modeling using mesh free connection which is suitable for vehicle development process. However, these models have not been validated with a full vehicle level test results. A spot weld rupture model using beam element and mesh free connection, which can simulate both nugget pullout and nugget fracture mode of spot weld rupture, has been developed. Full vehicle level FE analysis is conducted to confirm the prediction accuracy of developed spot weld rupture model. Results show that spot weld rupture locations and number of ruptured spot welds closely correlate with actual crash test results.

• Seismic Modelling of an AGR Nuclear Reactor Core

  Bruce Duncan,Berislav Kralj - Atkins

  The work concerns the seismic response of an Advanced Gas-cooled Reactor (AGR) core. An LS-DYNA finite element model has been developed that represents each graphite brick. The contact between the bricks and their keys has been modelled with non-linear coaxial spring/dampers allowing for limited free motion. The model is a three dimensional representation of all the core layers and a neutron shield, making use of a symmetry by only modelling half of each layer. Different layers and groups of bricks have been allocated different spring/damper properties in order to accommodate differing initial geometry and levels of irradiation flux exposure. The core’s restraint system has also been modelled. Bespoke programs have been developed in Visual Basic for Applications to automatically generate the key file used by LS-DNYA and deal with the post-processing of results files. Sensitivity studies were done to assess the effects of changing the magnitude of the event and the effects of irradiation on the bricks.

• Simplified modeling of thin-walled tubes with octagonal cross section - axial crushing

  Yucheng Liu, Michael L. Day - University of Louisville

  This article investigates the collapse characteristics of thin-walled tubes with octagonal cross sections during axial crushing. The tubes’ axial crushing resistance (the relationship between crushing force and axial deformation) is described with a series of mathematical equations, which are derived applying global energy equilibrium theory. The derived axial crushing resistance is then used for developing simplified finite element models for the thin-walled octagonal tubes. The simplified finite element model is composed of beam elements and nonlinear springs, where the nonlinear springs were defined using the derived axial resistance and would be used to simulate the buckling behavior of the simplified model during crash analyses. The developed simplified models are used for crash analyses, and the results are compared to those from corresponding detailed models as well as from the published literatures. Relatively good agreement is achieved through these comparisons, and it shows that the simplified models can save much more computer resources and modeling labor compared to the detailed models. Explicit code LS-DYNA is used for all the modeling and simulation presented in this article.

• Simulating the Complete Forming Sequence for a Roll Formed Automotive Bumper Beam

  Trevor Dutton, Paul Richardson - Dutton Simulation Ltd, Matt Tomlin, Tom Harrison - Wagon Automotive plc

  As part of the development of a new automotive bumper beam, a complete simulation of the entire forming process was carried out using LS-DYNA. The material for the beam was an ultra high strength steel presenting many challenges for the forming process. The sequence of forming operations was roll-forming (including forming a sweep in the initially straight roll-formed section), local annealing, forming of an initiator in the wall of the section and then crushing the end of the previously rolled section. The forming results (geometry, thinning and work hardening) were all transferred to the simulation of the bumper performance under various impact conditions. The paper describes the development of certain novel simulation techniques, particularly for the roll-forming for which the implicit analysis options of LS-DYNA were used, representation of the annealing process, as well as the method in which data was transferred between the various simulations. Above all, we describe how the simulations were used to guide the design of the bumper beam system up to the point of prototype manufacture and test.

• Simulation of a CMVSS 215 bumper pendulum test series with LS-DYNA

  Armin Huß, Heiko Beck, Ingenieurbüro Huß & Feickert, Germany

  In the course of an increasing automotive development for international markets many new loadcases have to be tested. The Canadian bumper pendulum test (CMVSS215) is one of these loadcases that form a special challenge for the simulation with LS-DYNA due to its sequential process. For this test four different bumper pendulums have to impact the vehicle, while with each new test the prior damages have to be taken over. Until now the simulation had to be interrupted after each impact due to the necessity of repositioning the vehicle to the initial state. This demands personal intervention of an engineer after each of the first three impacts costing useful time. In some cases complex scripts are run between the impacts to reposition the car, which has the advantage of being independent of human intervention, but still these are time-consuming methods. Much more practicable and feasible is a solution directly using the possibilities of LSDYNA which neither cost any script processing time nor affords human intervention. At Ingenieurbüro Huß & Feickert a method was developed which links the motion of the impactors to the movement of the car so that each pendulum can start in the right initial position for the specific loadcase. Thus the test can be performed in one single run saving useful time for development.

• Simulation of a Mine Blast Effect on the Occupants of an APC

  A. Brill, B. Cohen - RAFAEL Ballistic Center, Israel, P. Du Bois, Consulting Engineer, Germany

  In this paper the use of LS-DYNA for the simulation of a mine blast load on an armoured personnel vehicle is presented with comparison to a full test. The investigated vehicle is an M113 APC with occupants seated in commercial seats. Different approaches to the numerical analysis of this complicated event are presented and results are compared. In particular the blast load is applied using the standard engineering model (CONWEP) because of the obvious computational advantages of this approach. However, a fully coupled finite element analysis simulating the interaction between the blast wave, the detonation gases and the vehicle was also performed. It is shown that the classical engineering model can severely underestimate the load on the APC. The use of the LS-DYNA component dummy models for the simulation of the occupants is also illustrated. The numerical simulations using LS-DYNA hydrocode were in good agreement with the experimental results. Those results show that the normal accelerations measured in the dummies pelvis are lower than the critical acceleration.

• Simulation of acoustic and vibroacoustic problems in LS-DYNA using boundary element method

  Ahlem Alia, Mhamed Souli - LSTC, James Hargreaves, Brian Walker - ARUP, Mojtaba Moatamedi - University of Salford

  The present work concerns the new capability of LS-DYNA® in solving acoustic and vibroacoustic problems. In vibroacoustic problems, which are assumed to be weak acoustic-structure interactions, the transient structural response is computed first. By applying the FFT, it is transformed into a frequency response. The obtained result is taken as boundary condition for the acoustic part of the vibroacoustic problem. Consequently, the radiated noise at any point into space can be calculated. The new developed LS-DYNA keyword is based on boundary element method (BEM) in which only the surface of the acoustic domain needs to be discretized. Besides BEM that solves the Helmholtz equation as a linear system, the new card allows, also, to use two other approximative Rayleigh and Kirchhoff methods. Both methods do not require a system of equations to be assembled and solved. Consequently, they are faster than BEM. Rayleigh method assumes that the radiating structure is a plane surface clamped into an infinite rigid plane. In Kirchhoff method, BEM is coupled to FEM used for acoustics in LS-DYNA by prescribing non reflecting boundary condition. In this case, at least one fluid layer needs to be merged to the vibrating structure.

• Simulation of containment-tests of fast-spinning rotors by explicit FEM

  Thomas Winter - MAN B&W Diesel, Germany, Armin Huß, Heiko Beck - Ingenieurbüro Huß & Feickert, Germany

  The objective of Containment Tests is to demonstrate that the housing of a turbocharger is of sound design and capable to satisfactorily contain fractured rotating parts inside the casing. As of yet these tests were carried out on a test bed during the type approval procedure of the turbochargers. On one hand this is very expensive and time consuming and, on the other hand, the comprehension of high-speed deformation processes is restricted as well as the possibilities for measurements and improvements are limited. Due to these reasons containment tests were simulated using the explicit finite element technique, which is implemented in the code LS-DYNA. The results of the simulations which were carried out were used to improve the performance of the turbocharger in containment safety. Regions of high loading of the structure could be identified and improved. For validation purposes a test was carried out on the test bed. The results of this test have shown excellent correspondence to calculation results of the simulation with respect to global and local deformations and the mechanical behaviour of the charger components.

• Simulation of Masonry Wall Failure and Debris Scatter

  Stuart C. McCallum, BAE Systems - ATC (Filton), Paul M. Locking, Steve R Harkness, BAE Systems - Land (Shrivenham)

  This paper outlines a methodology for the simulation of masonry wall failure and debris scatter. The aim of this work is to develop simulation techniques which can be used to assess and improve the design of building structures subject to high explosive loading. Masonry walls are constructed from bricks that are modelled as individual parts with tiebreak and single surface contact types. A key requirement of this work is to accurately predict the final landing position and scatter pattern of any bricks. If the acceleration of a separated brick is significantly high, the trajectory and final landing position of the brick will be influenced by air-drag. In this work we simulate the air-drag force using a user FORTRAN subroutine and demonstrate its accuracy with comparison to theory. The strength of the mortar-masonry brick bond is validated by comparison with laboratory experiments conducted in previous work showing close agreement. A series of simulations are then presented which demonstrate the failure and debris scatter of a simplified building structure.

• SIMULATION OF THE IMPACT ON GROUND OF AIRDROP LOADS TO DEFINE A STANDARD WORST CASE TEST

  Yves de Lassat de Pressigny, Thierry Baylot - Centre d’Essais en Vol, Ministère de la Défense, France

  The French Flight Test Centre in Toulouse (CEV Tl) made in 2004 prototype simulations of ground impact after airdrop (2d-40, 5th European LS-DYNA users conferences.) Its purpose was to enable the test centre to achieve parametric analyses of the shock level produced by airdrop with a combination of simulation and real tests, which was not feasible with tests only (because of the number of test cases required). Indeed a first proposal with several hundreds test cases had been rejected by the French Army Headquarters because of its high cost and length. An alternate solution with about a hundred simulation results and fifty four life tests was finally accepted and realised throughout 2005 and 2006. LS-DYNA was used to demonstrate what were the cargo fitting techniques and impact conditions that could produce the highest shock levels with the current state of airdrop technology. This gave the experts early hints in their purpose to design a standard test case to assess weapon systems reliability after airdrop. The testing campaign afterwards was focused on checking key points of the simulation analysis and evaluate the importance of non deterministic effects that could not be simulated, which is needed to estimate the actual value of the future standard qualification test for airdrop.

• Sloshing response of a LNG storage tank subjected to seismic loading

  Rosario Dotoli, Daniela Lisi, Danilo Bardaro - CETMA, Marco Perillo, Massimo Tomasi - EnginSoft

  The number of Liquefied Natural Gas tanks is continually increasing. These tanks are very large and their capacity is about 150000[m3]. According to safety standards these kinds of tanks consist of an inner steel shell, containing the LNG, and an outer reinforced concrete shell. Nevertheless, they represent a great risk if they fail during an earthquake. Several types of tank failures have been observed. Tanks may be damaged for different reasons. Large shell hoop tensile stresses, resulting from a combination of hydrostatic pressure and hydrodynamic pressure, due to horizontal and vertical ground motions, could fail the tank. A more common type of failure is known as “elephant’s foot buckling”[3]. This is caused by the large overturning base moments, resulting from the impulsive and convective liquid loading on the tank wall during an earthquake. The high vertical compressive stresses, which develop in the tank wall, may cause the buckling of the structure. The aim of this work is to simulate the seismic behaviour of an LNG tank during an earthquake. The analyses have been performed with Ls-Dyna code using a Lagrangian Conference approach [1],[5]. The applied seismic loads have been registered during a Richter magnitude 7.1 earthquake (Magnitude Moment 6.9). Simulations have shown that fluid motion and fluid-structure interaction are responsible of a failure type known as “elephant’s foot”. 3-D results of the large model (76 [m] in diameter) have been visualized with the support of a multi-wall screen at CETMA Virtual Reality Centre (CVRC). This BARCO visualization system is based on ORAD pc cluster with Digital Video Graphics DVG-10, with tracking and stereo capabilities. The FEM model consists of a flat anchored bottom and a cylindrical metallic wall in contact with the LNG: Diameter Wall high Liquid level Liquid volume Tank mass Liquid mass 76[m] 41[m] 38[m] 172000[m3] 4470[ton] 68954[ton]

• SOME APPLICATIONS OF LS-OPT TO BIRD IMPACT SIMULATION

  Peter Starke, Leonhard Mitterleitner - EADS Military Air Systems

  This paper describes the application of LS – OPT for assessment of the influence of stochastic effects in bird strike events. To address the problem, a two – step approach has been chosen. In the first step, LS – OPT has been used in order to automatically determine the penetration velocities for different impact sites. In a second step, LS – OPT was used to create a response surface from the calculated penetration velocities. Subsequently, for a given scatter in the impact site the resultant statistical distribution has been determined by LS – OPT.

• Some observations on failure prediction in sheet metal forming

  Mats Larsson - Saab Automobile, Sweden, Kjell Mattiasson - Chalmers Univ. of Technology, Sweden, Mats Sigvant -Volvo Cars Manuf. Engng., Sweden

  This paper presents results from a FE-study on failure prediction in ductile metal sheets. The studied material, a DP600 dual phase steel, is used throughout the study. The effects of variation of element sizes, material parameters, and friction are shown and discussed. Also results from simulations of in-plane and out-of-plane tests are compared and discussed.

• Spotweld Failure Prediction using Solid Element Assemblies

  Skye Malcolm - Honda R&D Americas Inc., Emily Nutwell - Altair Engineering

  One current methodology for spotweld modelling utilizes a tied contact to connect the weld elements to the components. In order for this contact to be robust and acceptably mesh independent, multiple solid elements are needed to represent a single weld. Several studies were conducted which concluded that a cluster of eight hex elements provides significantly improved performance over a single beam or hex element. However, ease of use is critical to the application of these spotwelds since thousands of welds can be present in a single full vehicle model. Therefore, a single output is generated for each weld assembly rather than on an element basis. The time step for these hex clusters is controlled by the smallest edge length so using multiple elements does not result in a time step penalty since the thickness of the weld is usually the smallest edge length. This paper will present the development of the eight hex cluster weld, followed by the validation process of these cluster spotwelds. Failure parameters for the resultant-based Mat 100 Damage-Failure model were derived by simulating coupon tests of single welds in shear and tension failure. These failure parameters were then used in a component test model with dozens of welds, several of which failed under the applied load. Finally, these parameters were applied to a full vehicle model using automatic sorting of the welds by the pre-processing software. At both the component and full vehicle level, good agreement was found between simulation and test results. The additional mass scaling and run time penalties of the cluster spotwelds were not significant. Furthermore, the effort needed to apply automatic methods to organize the welds is small enough to be practical in the production CAE environment.

• Springback analysis in Andvanced High Strength Steel using a new flexible semi-industrial tool geometry, the flex-rail

  A. Andersson - Volvo Cars Body Components, Sweden

  The automotive industry is using more and more of Advanced High Strength Steel in order to reduce the weight of the car. Since this will generate more springback, it is of vital importance to be able to predict the amount of springback in the parts. Otherwise, many late changes have to be made in order to fit the parts in their position. In order to increase the ability to understand and test the behavior of the springback in sheet-metal parts, a new semi-industrial experimental tool, the flex-rail, has been developed. This is a very flexible tool, which can be used for various kinds of materials, from mild steel and aluminum to advanced high strength steel such as TRIP-steel and CP-steel by using different inserts. The tool is designed for experimental analysis of 3D-springback, which is the case in the more complicated automotive parts, such as bpillars and side members. The scope of this work is to analyze the springback behavior and prediction for Advanced High Strength Steel both numerically and experimentally. Sheet-metal-forming simulations were made in LS-DYNA. The results proved that the new geometry, flex-rail, gave a complex springback behavior for all tested materials. Furthermore, the prediction of springback showed good correlation in sections with small amounts of twist but that LS-DYNA underpredicts the springback for sections with large amounts of twist for all materials.

• STRUCTURAL OPTIMIZATION OF PRODUCT FAMILIES EXPOSED TO CRASH LOADING

  Michael Öman - Linköping University, Sweden

  This paper discusses the problem of structural optimization in product family design and different methodologies are evaluated for weight optimization of components that are common for members in the family. First, the benefits of product family design are presented, followed by a discussion of the complexity of the design problem when the product family is exposed to crash loading and multiple load cases. It is concluded that in large problems the number of combinations of product and load case can get very large and due to the large number of simulations needed, it becomes practically impossible to solve the optimization problem with traditional methods. Therefore, a new methodology is presented that reduces the number of simulations by identifying the most critical combination of product and load case for every boundary condition and iteration. Different optimization methodologies are applied to a family of crash boxes and, finally, results and efficiencies are compared.

• THE ROLE OF CAE MODELLING IN VOLVO SAFETY ENGINEERING

  Ingrid Skogsmo - Director Volvo Cars Safety Centre

  Safety has been a Volvo cornerstone from its founding in 1927, and has remained a fundamental core value since. Within the Ford Motor Company, Volvo Cars has been appointed Centre of Excellence for safety. Continuous development and expansion of the concept of automotive safety involve visionary ideas build on earlier innovative passive and active safety approaches to deliver new "intelligent" solutions designed to neutralize risks of driver error while enhancing motoring enjoyment. The basis for the safety development is a solid understanding of what happens in the real world. Since 1970, Volvo Cars' Accident Research Team has investigated accidents with Volvo cars in Sweden and today we have a database containing more than 36.000 accidents – resulting in valuable in-depth studies as well as comprehensive accident statistics. This knowledge plays an important role when Volvo Cars sets its targets and it is also used as a basis for developing in-house test methods that are similar to real-life accidents, product development and new car projects. Examples of safety systems that have been pioneered as a result of the accumulated experience include the world first systems SIPS (Side Impact Protection System) and WHIPS (Whiplash Protection System), as well as a patented frontal collision structure. Testing, both physical and virtual, and analysis are essential parts in the development of a new car. The Volvo Cars Safety Centre has state-of-the art facilities for car testing, verification and innovative technology that enables us to recreate real traffic situations. Developing a new car model has traditionally been a very test intensive activity. As hardware and software were developed, full car crash simulation and other advanced CAE methods became available, and the product development has become more and more CAE-driven. The ultimate goal - analytical sign off -where production tools are ordered without full scale physical testing, seems to be within reach. To some extent we are already there.

• Uncertainty Assessment with Stochastic Simulation in Aircraft Cabin Development

  D. Vogt,R. Hartnack,M. Olbert - EADS Innovation Works, J. Schlattmann, Hamburg University of Technology

  To fulfill the need for shorter development cycles in modern product development the increased use of computer-aided engineering is one possibility. While the numerical calculation of a model leads to one single solution, the behavior of systems in the real world is never exactly repeatable due to tolerances and natural scatter in the system parameters. The assessment of the resulting uncertainties is of great importance for systems requiring a high level of reliability (such as aerospace systems), therefore they should be treated with special care in the development process and in particular in computer-aided engineering. This paper describes the execution and analysis of an uncertainty management technique with Stochastic Simulation for an LS-DYNA model of an exemplary system consisting of an overhead stowage bin and carry-on baggage excited by external acceleration. The Stochastic Simulation results are evaluated using statistical methods. It is shown which parameters are of paramount influence on system behavior and may hence result in a critical load due to carry-on baggage.

• Using LS-Dyna as an Aid to the Inclusive Design of Child Resistant Closures

  Joe Luxmoore, Dr. Alaster Yoxall - University of Sheffield

  The population of most developed countries is ageing. Despite continuing medical advances, ageing brings with it a host of issues, not least a loss in strength and dexterity. One major area of concern is the ability of elderly consumers to access packaged goods such as food and medicines. In previous studies, the authors developed an LS-Dyna model of a human hand that was used to investigate the effect of physical dimensions and the choice of grip type on joint stresses and hence levels of discomfort. The work was supported by consumer ethnography studies and lead to recommendations for inclusive packaging design. In the present paper, the model is applied to a product that is known to cause particular difficulties for the elderly, the “squeeze and turn” child resistant closure, identifying the specific ergonomic issues associated with it.

• USING LS-OPT/LS-DYNA IN A MULTI-ATTRIBUTE OPTIMIZATON

  Forsberg Jimmy, Björkman Gunnar - VTEC

  This paper summarizes the experiences of using the LSTC environment in a multiattribute optimization. The work was carried out in an on-going project, SuperLIGHTCar (SLC), which aims to reduce the weight of the body in white (BIW) of a compact class car by at least 30%. This objective is made possible by using new materials and a blend of materials in the design. The car should still fulfil user rating, e.g. Euro NCAP demands but also demands of production rate, cost, life cycle analysis, stiffness demands, etc.. The VTEC involvement in the SLC project is to perform structural optimization of the BIW with respect to the defined loadcases and corresponding target values for responses defined for each loadcase. In this paper the set up of the current optimization problem, resources needed and “work-arounds” are presented. The current optimization formulation requires the solution of 6 impact loadcases, 2 static loadcases and an eigenvalue problem. The final results from this investigation are still to be seen.

• Using LS_DYNA to find Failure modes during design process

  Dr. Tayeb Zeguer - Jaguar and Land Rover

  Understanding the customer needs Failure Mode List Generation Detection using CAE – Capability and Enablers CAE Execution Process and the use of DFSS principles Conclusions

• VALIDATING DYNAMIC TENSILE MECHANICAL PROPERTIES OF SHEET STEELS FOR AUTOMOTIVE CRASH APPLICATIONS

  P.K.C. Wood, C.A. Schley - University of Warwick, M. Buckley - Jaguar and Land Rover, B. Walker - ARUP, T. Dutton - Dutton Simulation

  A thin-wall open channel beam, fabricated from high strength Dual Phase sheet steel, subjected to 3-point bending and constant velocity boundary condition, is investigated to validate material performance for automotive crash applications. Specifically quantitative validation of material tensile data determined from high speed tests and component models, and qualitative validation of materials resistance to fracture. The open channel beam is subjected to quasi-static and increasing loading speed and in all cases, large displacement in which deformation involves formation of a plastic hinge. This paper describes development of test procedure, notably beam specimen design, measurement system and boundary conditions, using both experimental and numerical techniques. The new test procedure, as a compliment to crush testing, will increase confidence in the modeling and application of new advanced higher strength materials in automotive crash structures.

• Virtual Modelling of Motorcycle Safety Helmets: Practical Problems

  Alessandro Cernicchi, Ugo Galvanetto, Lorenzo Iannucci - Imperial College London

  Motorcycle helmets are safety devices that can be optimised to perform better in different impact configurations. It is not easy to determine the mechanical properties of a particular model of helmet which maximise its effectiveness in real impact conditions and it is not surprising that most helmet producers use empirical design procedures and assess the effectiveness of their products by carrying out numerous experimental impact tests. The application of advanced computational techniques (i.e. Finite Element Method) to the study of the mechanical behaviour of helmets has been conducted with a variable degree of success in several cases. The use of virtual methods clearly provides a superior flexibility during the design process due to the simplicity by which the model is modified and retested. This work is an attempt to clarify modelling aspects encountered in helmet virtual testing, such as mesh dependency of the results, the influence of retention system on the response and composite shell modelling. A Finite Element model of a commercially available helmet has been developed and impact tested reproducing the test conditions prescribed by the ECE 22.05 standards. Particular emphasis has been given to the analysis of fibre reinforced plastic helmets, which are currently under further development, due to their superior performance. The results have been compared with experimental data and possible reasons for discrepancies have been analysed.

• VOLVO TECHNOLOGY VEHICLE STRUCTURAL OPTIMIZATION ENVIRONMENT

  Gunnar Björkman,Jimmy Forsberg - Volvo Technology, Jan Engström - SCH Incubator AB

  With the ever increasing capability in computer power, optimizing a full vehicle structure including most of the crash load cases will be a real possibility in the near future. For example, the Cell chip used in PS3 or the availability of recent GPU of high end PC graphics cards delivers 100 – 1000 GFLOPS. The bottleneck in this scenario will not be the computer power, instead the problem will be how to feed the computers with models and input decks to analyze in a reliable and stable way with little or no manual interventions. At Volvo Technology, we have, in different research and internal projects, developed a Vehicle Structural Optimization Environment that has the capability to enable the use of global optimization, in the development and evolution of vehicle structure. This environment integrates and manages the analysis software, the optimizer, our Linux cluster together with its queuing system, the model and concept generator, and finally the management of all generated models and analysis results. Currently we are using LSdyna for crash and static analysis, LSopt for controlling the optimizations and AML for creating models and input decks. An important factor in this environment is to have a stable model and input deck generator, without any manual interaction, capable of generating input decks for analysis for all types of concept that is of interest. Except for just changing thicknesses we may want to: find the most effective material to use, both from a weight and a cost perspective, determine the best layout for tailor welded blanks, change the cross section dimensions, find needed stiffeners or investigate new way of subdividing the design in parts. As an example, a global optimization of a BIW, including approximately 100 design variables, analyzing the Euro NCAP crash cases for five stars, handling, comfort and cost, running approximately 10-12 iterations for the optimization, will result in approximately 2500-3000 crash analysis, 1500-2000 eigenvalue analysis, and 4000

• WATER IMPACT: EXPERIMENTAL TESTS AND NUMERICAL SIMULATIONS USING MESHLESS METHODS

  Marco Anghileri, Luigi Castelletti, Edoardo Francesconi - Politecnico di Milano, Italia

  The outcomes of a research focusing on water modelling and fluid-structure interaction, are here presented. A number of water impact drop tests using a typical aircraft skin panel were performed. The tests were numerically reproduced modelling the fluid region using the two meshless methods implemented in LSTC/LS-Dyna 971: the Smoothed Particle Hydrodynamics and the Element Free Galerkin method. The accuracy of the models was evaluated referring to the data collected in the tests.