12th European LS-DYNA Conference

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

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

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

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

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

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

• A Full-Field Calibration Approach on Material Parameter Identification

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

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

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

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

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

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

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

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

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

  T. Tryland (Sintef Manufacturing)

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

• A Viscoelastic-Viscoplastic Time-Temperature Equivalence for Thermoplastics

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

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

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

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

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

• Adaptive Sampling using LS-OPT

  A. Basudhar (LSTC)

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

• Airbag Folding for LS-DYNA using Generator4

  L. Benito Cia (GNS)

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

• An LS-OPT® methodology for utilizing partial curve data for the calibration of material models

  N. Stander, A. Basudhar (LSTC), S. Du Bois (DYNAmore),

  Parameter estimation is a considerably large application area of optimization. It fulfills the important purpose of characterizing materials based on models available in Finite Element analysis software such as LS-DYNA®. The development of special LS-OPT® features for parameter estimation using Digital Image Correlation and other experimental methods has been ongoing for a number of years. In earlier papers [1,2] some of the available similarity measures as well as the LS-OPT DIC methodology were discussed in broad detail and illustrated with examples.

• Approach for Modelling Thermoplastic Generative Designed Parts

  F. Althammer (Daimler/University of Stuttgart), D. Moncayo (Daimler), Prof. P. Middendorf (University of Stuttgart)

  This study presents an approach to characterize thermoplastic generative designed parts and compares the usability of different material models in LS-DYNA. For using 3D printed parts in prototypes it is at first necessary to be able to predict the deformation behaviour of the printed part itself. The deformation behaviour of thermoplastics and especially of thermoplastic generated parts depends on a variety of material properties. In general the parts have a composed anisotropy consisting of the process and material anisotropy. The process anisotropy is reflected to different mechanical properties due to the building directions of the 3D printer. The material anisotropy includes divergent tension and compression behaviour and approximately orthotropic behaviour due to particle reinforcement. The main task therefore is to evaluate current material routines and modeling techniques to ensure the predictability of the parts behaviour with available and implemented material cards. The performed characterization consists standard specimen tests for a non-reinforced and a carbon particle reinforced thermoplastic, which is produced in the selective laser sinter process. The conducted tests are a tensile, a compression and a shear test. The test specimen were built in different construction directions. In addition, component tests were executed in order to evaluate the predictability of the generated material cards in multiaxial stress states.

• Armor Steel Impacted by Projectiles with Different Nose Shapes – Numerical Modelling

  T. Fras, N. Faderl (French-German Research Institute of Saint-Louis), C. C. Roth, D. Mohr (ETH Zurich)

  The presented experimental investigation concerns 3 mm thick target plates impacted by strikers with different noses at velocity close to 300 m/s and is conducted to gain an insight into mechanisms of deformation and fracture characteristic for a high strength high hardness armour steel, [1]. Guaranteed by the producer yield strength and ultimate tensile strength of the steel are 1300 MPa and 2200 MPa, and the hardness is within 600 – 640 HB, [2]. Due to impacts, the projectiles and targets, both extracted from the armour steel, are severely deformed and fractured. Numerical simulations of the performed test are carried out using the explicit solver of the finite element software package LS-Dyna R9.0.1. The model used in the simulation implemented through the user material subroutine accounts for a yield function with a non-associated flow rule, a Swift–Voce strain hardening law and Johnson–Cook type of multipliers with the effects of strain rate and temperature. The stress-triaxiality, Lode angle parameter and strain-rate dependent Hosford–Coulomb fracture initiation model is employed to predict a steel failure, [3-4].

• Automatized Kinetic and Strainfield Based Calibration for a Thermoplastic Material Model using High Speed Tensile Tests

  S. Schilling, P. Suppinger, P. Blome (Autoliv)

  Current and future automotive development cycles are driven by the needs for lightweight designs, cost reductions, comfort- and safety improvements and the reduction of time-to-market. One way to cope with the listed challenges is the usage of thermoplastic materials for integrative designs of components. Among the challenges for passive safety supplier Autoliv to design thermoplastic components, which are placed in the load path of seatbelt components, is the strong dependency on loading velocity of the components. As crash situations are the most dominant load cases for design and functionality, a strong demand for predictive strain rate dependent material models is given. Strain rate effects are next to temperature- and humidity effects the major challenge concerning thermoplastics. As an industrial demand for a comprehensive material database, it needs to be fast, efficient, economical and accurate. Also, the need for a fully automatized material model calibration process is expressed. To fulfill these demands a two-stage reverse engineering process fits test results to analytical approaches for a quasi-static and a strain rate dependent stress-strain response along with an analytic approach for modelling of visco-elasticity and strain rate dependent damage. The needed test results, to which the analytical parameters are fitted, consist of force-displacement as well as strainfield characteristics and were measured using a newly developed high-speed tensile testing device. This device is designed to get close to constant loading velocity of specimen resulting in strain rates up to 𝜀𝜀̇ = 320 𝑠𝑠−1. The accuracy of the test results is ensured by a wedge-to-wedge, self-locking coupling mechanism, a start-up length for acceleration travel of the tensile testing machine as well as a local force gauge. Especially by the local force gauge, consisting of strain gauges arranged as Wheatstone bridge, it is realized that oscillations in force signals of dynamic testing are minimized. The automatized material model calibration routine fed with accurate test results from the high-speed tensile testing device shows promising results to further enhance simulation quality and predictability for the design of thermoplastic components in crash load cases.

• Bake-Hardening Effects, Arbitrary Image Data and Finite Point-Set Analysis Results made Accessible with envyo

  C. Liebold (DYNAmore), J. Zerbst (Daimler), S. Hagmann (Porsche), M. Hedwig (Porsche)

  In the recent past, a lot of effort has been made towards the closing of the simulation process chain for all different kinds of materials. Besides the regular transfer of resulting stress, strain, and history data, main focus from a material’s perspective has been on the transfer of fiber orientations from process simulations for continuous fiber reinforced composites [1] together with various homogenization approaches for short fiber reinforced plastic materials [2].

• Ballistic Behaviour of UHMWPE Composite Material: Experimental Characterization and Numerical Simulation

  H. Abdulhamid, P. Deconinck, P.-L. Héreil, J. Mespoulet (Thiot-Ingenierie)

  This paper presents a comprehensive mechanical study of UHMWPE (Ultra High Molecular Weight Polyethylene) composite material under dynamic loadings. The aim of the study is to provide reliable experimental data for building and validation of the composite material model under impact. Three types of dynamic characterization tests have been conducted: in-plane tension, out-of-plane compression and out-of-plane shear. Moreover, impacts of spherical projectiles impact have been performed on larger specimen. Regarding the numerical simulation, an intermediate scale multi-layered model (between meso and macro scale levels) is proposed. The material response is modelled with a 3d elasto-orthotropic law coupled with fiber damage model. The modelling choice using *MAT_ORTHOTROPIC_SIMPLIFIED_DAMAGE is governed by a balance between reliability and computational cost. Material dynamic response is unconventional [1, 2]: it shows large deformation before failure and very low shear modulus and peeling strength. Numerical simulation has been used both during the design and the analysis of tests. Mechanical properties related to elastic moduli and failure strength have been measured. The ballistic numerical model is able to reproduce the main behaviors observed in the experiment. The study has highlighted the influence of temperature and fiber slipping in the impact response of the material.

• BatMac: A Battery Macro Model to Simulate a Full Battery in an Electric or Hybrid Car Crash

  P. L‘Eplattenier, I. Caldichoury (LSTC)

  Safety is an important functional requirement in the development of large-format, energy-dense, lithium-ion (Li-ion) batteries used in electrified vehicles. Computer aided engineering (CAE) tools that predict the response of a Li-ion battery pack to various abusive conditions can support analysis during the design phase and reduce the need for physical testing. In particular, simulations of the multiphysics response of external or internal short circuits can lead to optimized system designs for automotive crash scenarios.

• Battery Cooling Simulation using STAR-CCM+

  D. Grimmeisen, M. S. Schneider (Cascate)

  A generic Li-ion battery pack as typically used in an electric vehicle is simulated in STAR-CCM+, using an analytical model for the electrochemical battery behavior and a thermal/flow simulation with conjugate heat transfer to determine the cooling efficiency. A single Li-ion battery cell is modeled in Battery Design Studio. This model is then used in the Battery Simulation Module of STAR-CCM+, which allows to embed the cell within an electric circuit and to put it under a prescribed load. The battery model then calculates the heat development in the cell based on the load and the electrochemical model. This heat is applied as a distributed heat source in the fluid simulation, which can then be used to investigate and optimize the cooling efficiency.

• Blast Detonated by Impact Simulation

  M. Büyük (Sabanci University), H. Balaban, U. Penekli (FE-Tech)

  The purpose of this study is to present parameters required for blast detonated by impact simulation in LS-DYNA with comprehensive approach and compare with AUTODYN results. Blast detonated by impact is a widely used method for controlled blast. However, design of the problem is more likely limited to simulation results. For a proper and reliable simulation, it has to be taken care of reacted and unreacted state parameters of detonative product, mesh size and method.

• Bolted Joint Connections of FRP-Components in Submarines Subjected to Underwater Shock

  A. Rühl, B. Özarmut, B. Hennings, O. Nommensen, A. Paul (thyssenkrupp Marine Systems)

  The application of fiber reinforced plastic (FRP) and sandwich components is an established practice at various locations in state-of-the-art submarines. Due to acoustic reasons, easy formability and low mass density at comparatively high strength values, these components bear a huge potential for buoyancy-related constructions. The shock-design and -calculation of these components as well as their connecting parts are crucially supported by Finite Element simulations using LS-DYNA. The present work shows an investigation of FRP-based bolted joint connections in today’s submarines and their connection to the pressure hull in terms of modelling and simulation. The transfer from detailed models to simulation of a full-scale shock submarine, as shown in Fig. 1, is presented and discussed.

• Comparative Evaluation of Isogeometric Analysis and Classical FEM with Regard to Contact Analysis

  Z. Naveed, A. Kühhorn, M. Kober (BTU Cottbus-Senftenberg)

  Isogeometric analysis represents a newly developed technique that offers the application of Computer Aided Design (CAD) concept of Non-uniform Rational B-Splines (NURBS) tool to describe the geometry of the computational domain. The simplified transition of CAD models into the computational domain eliminates the problems arising from the geometrical discontinuities induced by the faceted approximation of the mesh. Moreover, numerical analysis directly on NURBS objects significantly reduces the design-to-analysis time compared to traditional FEA approach. In the field of contact mechanics, when finite elements are applied to geometry with curved surfaces, the result is a non-smooth geometrical representation of interface surfaces which may lead to mesh interlocking, high jumps and spurious oscillations in contact forces. To eliminate these issues, various surface smoothening strategies are to be employed in case of FEM. Isogeometric based analysis alleviates these issues without employing any additional smoothening strategy due to inherent higher order continuity of NURBS basis functions and much more accurate results are obtained compared to conventional FE approach. In the current study, LS-DYNA is used to demonstrate the capabilities and advantage of an isogeometric analysis though an example of pendulum under gravitational load. The numerical simulation results are analytically validated and the comparison of NURBS surfaces with faceted surfaces is carried out to investigate the accuracy.

• Comparison of Different Material Models in LS-DYNA (58, 143) for Modelling Solid Birch Wood

  G. Baumann, Graz, F. Feist (University of Technology), S. Hartmann (DYNAmore), U. Müller (University of Natural Resources and Applied Life Sciences), C. Kurzböck (Virtual Vehicle Research Center)

  Sustainability plays an increasingly important role in the automotive industry. In order to reduce the ecological footprint, the suitability of alternative bio-based materials like wood is investigated within the project WoodC.A.R. In order for wood to be used as an engineering material for structural components or even crash relevant structures, it has to fulfill high mechanical demands. The material behavior has to be predictable and describable in a numerical simulation. Therefore, two material models *Mat_58 (*Mat_Laminated_Composite_Fabric) and *Mat_143 (*Mat_Wood) were compared and validated against quasi-static tension and compression tests in all its six anatomical directions but also against three-point bending tests with the wood fibers oriented parallel to the beam’s axis. So called “clear wood” samples, i.e. specimens without any growing features, were tested covering the different load levels: linear elasticity, strain-hardening, strain-softening and rupture. While *Mat_58 is an orthotropic material model, *Mat_143 is transversally isotropic which means there is no possibility to distinguish between the radial and the tangential direction of the material. Therefore, a trade-off for both directions has to be found. On the other hand, the material law *Mat_143 is able to consider influences like temperature, moisture content or even the quality respectively sorting degree of the wood. Both material models show that some simplifications considering the hardening and softening behavior, especially in compression have to be taken into account in multi-element specimens. While wood shows softening at longitudinal compression, there is a pronounced hardening in perpendicular direction. The strengths and weaknesses of both material models are discussed.

• Comparison of Laser-Scanned Test Results and Stochastic Simulation Results in Scatter Mode Space

  M. Okamura, H. Oda (JSOL), D. Borsotto (Sidact)

  Recent years, CAE plays more important roles in product development than ever. Good CAE models require validation works with various test data. However, the way of comparison needs to be improved in order to meet the market expectations. Usually a set of test data is given to CAE engineers after all specimen are tested, and test machines are cleaned up. In case CAE engineers find out remarkable differences between simulation results and test results are too great due to mistakes in test laboratories, validation process becomes quite difficult in many cases. In this study, quasi static compression of a crash box is used as an example in order to illustrate the proposed process. A preliminary stochastic simulation and a set of tests is conducted, and the deformation of the crash boxes are transformed into the common modal space. This process makes it possible to assess similarity of deformation modes from multiple simulation results and test results at a glance. This analysis can be conducted at test lab, and fundamental difference between test and simulation can be detected every time specimen are tested. In case an issue is detected, CAE engineers and test engineers can start discussion how to improve the test set up and simulation model in the laboratory.

• Comparison of LS-DYNA Version 7, 9 and 11 – A View of an Airbag Supplier

  A. Seeger (iSi Automotive Berlin), S. Stahlschmidt (DYNAmore)

  Several LS-DYNA versions are currently available – R7 is still in use in several projects, the currently mostly used version is R9, future projects will be run in R11. This paper will compare these three versions with focus on some airbag issues.

• Composite Forming Simulation with Introduction to J-Composites/Form Modeler Version 2.0

  M. Nishi, S. Wang, S. Dougherty (JSOL), X. Zhu (LSTC)

  JSOL Corporation has developed J-Composites®, a set of tools, which works in cooperation with LS-DYNA®, to facilitate the complex manufacturing process and process-chain simulation of fiber reinforced composite materials. The J-Composites series consists of “Form Modeler”, a tool to set up a press forming analysis model, and “Fiber Mapper”, a tool to map a resin flow simulation result on to a structural mesh. Additionally, “Compression Molding”, a tool for compression molding simulation is in development. This paper introduces some new capabilities of J-Composites/Form Modeler version 2.0 and demonstrates composite forming simulations.

• Composites in High Voltage Applications

  C. Weinberger, M. Rollant (4a engineering)

  In the last years the demands of the automotive industry have led to a strong interest in a more detailed virtual description of the material behavior of thermoplastics. More and more complex material models, including damage and failure, have to be characterized, while keeping the importance of gaining material data quickly in mind. Currently material and failure modeling in crash simulations typically deal with simple von Mises visco-plasticity (*MAT_024) and equivalent strain failure criteria, which cannot describe the complex material behavior of plastics. Past developments have focused on the yield behavior under different load situations (tension, shear, compression), which are implemented in more complex material models like *MAT_SAMP-1 for thermoplastics as well as *MAT_215 for fiber reinforced thermoplastics.

• Considering Manufacturing Induced Inhomogeneity in Structural Material Models (VMAP)

  B. Jilka, P. Reithofer (4a engineering)

  The ITEA VMAP project aims to gain a common understanding of and interoperable definitions for virtual material modelling in Computer Aided Engineering (CAE). Using industrial use cases from major material domains and representative manufacturing processes, new concepts will be created for a universal material exchange interface for use in virtual engineering workflows. [1] In the VMAP consortium with nearly 30 partners, 4a is focusing on injection molding of plastics. Two sub use cases – namely impact behavior of fiber reinforced thermoplastics and structural behavior of foamed parts - are presented in this contribution.

• Constitutive Model of Filled Elastomers Capable of Capturing Mullins Effect, Hysteresis, Induced Anisotropy and Permanent Set – Part I: Model Theory & Implementation

  R. Chandrasekaran, M. Hillgärtner, M. Itskov (RWTH Aachen University), M. Müller, F. Burbulla (Dr. Ing. h.c. F. Porsche)

  In this contribution, a finite element implementation of a micromechanically based constitutive model describing several inelastic effects of filled rubbers in multiaxial deformation states is presented. The model describes the elastic and inelastic effects of filled rubbers and is based on the network decomposition concept. Accordingly, the rubber network is decomposed into an isotropic elastic network E, responsible for the polymer matrix, and two anisotropic permanent damage networks (M and H) which are responsible for the filler-polymer interaction. The anisotropic damage networks M and H are capable of capturing the Mullins effect, hysteresis, permanent set and induced anisotropic stress softening. This model is implemented into LS-DYNA® by means of a subroutine within *MAT_USER_DEFINED _MATERIAL_MODELS (UMAT). The user can easily switch between different combinations of elastic and inelastic models by activating and deactivating each network. The user can also select the number of directions to be considered depending on the complexity of the loading history. The model with appropriate material constants demonstrates good agreement with experimental data.

• Constitutive Model of Filled Elastomers Capable of Capturing Mullins Effect, Hysteresis, Induced Anisotropy and Permanent Set – Part II: Experiments & Validation

  M. Hillgärtner, R. Chandrasekaran, Mikhail Itskov (RWTH Aachen University), M. Müller, F. Burbulla (Dr. Ing. h.c. F. Porsche)

  This contribution discusses experiments necessary to describe the behavior of filled elastomers under large strains. Filled elastomers show a variety of inelastic phenomena such as Mullins effect, hysteresis, induced anisotropy, and permanent set. While uniaxial tension tests to rupture provide virgin loading curves, other tests are necessary to gather information about the inelastic effects mentioned above. In order to capture these phenomena experimentally, cyclic uniaxial tension tests with stepwise increasing load amplitudes are carried out. Since experimental stress-strain curves characterize some restricted set of defined loading conditions (such as uniaxial test, pure shear, or equi-biaxial tension), additional investigations of two-dimensional strain data from arbitrary deformations states are necessary. This strain data can be obtained for example by digital image correlation. In particular, we demonstrate how the previously described constitutive model can be calibrated using a variety of experiments. We verify the calibration comparing the results of our subroutine implemented as UMAT in LS-DYNA with two-dimensional strain data obtained from digital image correlation of a plate with a hole subjected to tension. The described model shows good agreement with the obtained data.

• DDAM Analysis with LS-DYNA

  Y. Huang, Z. Cui (LSTC)

  DDAM (Dynamic Design Analysis Method) is a U.S. Navy-developed analytical procedure for shock design. It helps validate the design of onboard equipment and structures subject to dynamic loading caused by underwater explosions (UNDEX). It is a widely accepted procedure for safety evaluation for civil and military ship building. The keyword for response spectrum analysis (*FREQUENCY_DOMAIN_RESPONSE_SPECTRUM) in LS-DYNA has been extended to run DDAM analysis for shipboard components, with the option _DDAM. This paper first gives a brief review of the theory for DDAM analysis. Then, with several examples, this paper shows how to run DDAM analysis with LS-DYNA and how to perform post-processing of the results. For purpose of cross-validation, the results of DDAM analysis with LS-DYNA in the first example are compared with that given by other commercial code.

• Design and Material Characterization of Reinforced Plastics for Secondary Structural Load Paths in an Early Development Phase

  D. Moncayo (Daimler), M. Cyperling (Mercedes-Benz Werk), G. Dumitru, T. Graf (DYNAmore), D. Coutellier, H. Naceur (Université Polytechnique Hauts-de-France)

  This paper presents different modeling approaches and technical challenges for the discretization of anisotropic elastic-viscoplastic materials in secondary structural parts for the automotive sector. In terms of accuracy, complex geometries based on reinforced plastics in secondary load paths need to factor in the manufacturing process and the resultant local anisotropies within correspondent CAE models. However, during the early phase of product development, integrating reinforced plastics, a robust numerical basis throughout the concept evaluation is required. The basic idea is to maintain the correspondent level of complexity through the subcomponent design within certain limits, in order to improve, speed up and adequately handle complexity in CAE concepts for the automotive sector. Finally, a benchmark analysis of possible options and modeling techniques is introduced, as a contribution to evaluate the balance between the dimensioning of structural load paths and the required material characterization within an acceptable effort.

• Design optimisation of a side impact beam made out of high strength aluminium alloys using Barlat YLD2000 and GISSMO failure model for the “Extended Hotforming Process”

  J. M. Schlosser, S. Mouchtar, W. Rimkus, R. Schneider (Hochschule Aalen)

  The automotive industry is facing new challenges due to stricter CO2 emission laws. Thus, to design more environmentally-friendly cars, various lightweight construction strategies need to be considered to meet the growing demand for resource efficiency [1]. In order to minimise weight, the lightweight design strategy "design for lightweight construction" is increasingly becoming important for industry. Especially the “structural optimisation” with its sub-areas: topology-, fibre-, thickness- and parameter-optimisation is designated as a very powerful tool for lightweight applications. In addition, damage and failure modelling is getting more and more important in order to predict the behaviour of any component by FEM-simulations as accurate as possible. For this purpose, the entire material history (from production right through to the crash of the component) must be taken into account. Whereas for forming processes forming limit curves (FLC`s) are sufficient to predict the material behaviour failure models, which describe failure as a function of stress states, need to be applied for detailed crash calculations [2]. In this paper the design process of an AA7075 side impact beam will be presented; starting from structural optimisation through to the calibration of a material and a damage model. The geometry of the side impact beam is determined by topology optimisation. Special attention is given towards the temperature control of the forming process since a “Thermal Direct Joining” procedure (e.g. for CFRP-patches) is aimed to be implemented. The high-strength anisotropic aluminium alloy (AA7075) is characterised after applying the Hotforming process (Hotforming condition). Both, the Barlat YLD2000 material model and the GISSMO failure model are calibrated using the graphical optimisation tool LS-OPT.

• Design Qualification of the Jupiter Icy Moons Explorer JENI Instrument using the LS-DYNA Frequency Domain Suite

  M. Shanaman, S. Cooper, S. Jaskulek, C. Schlemm, P. Brandt, D. Mitchell, E. Rollend (Johns Hopkins University)

  In 2022 the European Space Agency (ESA) will launch the JUpiter ICy moons Explorer (JUICE) for an 11-year mission to the Jovian system. The Particle Environment Package (PEP) suite of sensors includes the Jovian Energetic Neutrals and Ions sensor (JENI), designed, built, and qualified by The Johns Hopkins University Applied Physics Laboratory. The requirements established to ensure JENI withstands the launch environment include a first instrument mode above 140 Hz and positive structural margin when subjected to 39g per axis quasi-static analyses and random vibration analyses totaling up to 9.12 grms.

• Determination of Impact Loads for a Tracked Military Vehicle during a Crash Scenario

  B. Balaban (FNSS Savunma Sistemleri)

  In this study, crash simulation for a tracked military vehicle is performed and equivalent static and dynamic design loads are determined for a subsystem using LS-DYNA® and LS-OPT®. Detailed finite element model of the track geometry, suspension system and the hull is created. In order to have an accurate vehicle suspension behavior; some verification simulations are conducted with another commercial multibody software and the suspension kinematic is optimized. Full vehicle crash simulations are performed firstly and stress results are obtained from the sub-system mounts of the vehicle. Afterwards, small scale simulation model of the sub-system is created and LS-OPT® is used to get equivalent static and dynamic acceleration loads using the stress results which are obtained from crash simulation.

• Development New MAT Applied Yoshida 6th Order Yield Function and its Verification

  H. Fukiharu, T. Amaishi (JSOL)

  Sheet metal forming simulation has become an indispensable tool for design of automobile parts and process design of its die. As for automobile parts, high strength steel and aluminum alloy are applied for them in progress. On the other hand, these lightweight materials are well known as difficult formability, and many problems have occurred in stamping process. In elasto-plastic FEA, there are many factors that determine the analysis accuracy, the material model is especially important. In case of applying associated flow rule, the yield function is key, and the reproductive capability of the material properties are very significant and influential. In LS-DYNA, there are many material models, and various yield function can be applied. MAT36(Barlet’89), MAT37(Hill’48), MAT242(Ylld2000-2D) [1] are commonly used in sheet metal forming. And this time, the MAT model that uses Yoshida 6th order yield function [2] are developed by using USER MATERIAL function in order to improve the accuracy. This MAT model take Yoshida-Uemori kinematic hardening model which is well known to be able to properly reproduce Bauschinger effect into account. And it can also strain dependency of Young’s modulus into account. This yield function is applicable with 16 parameters both to shell elements as well as solid elements, therefore this model is user-friendly for users from this point of view. In addition, it is easy to consider anisotropic hardening which is important factor for accuracy. This model was implemented as MAT_289. In order to verify the analysis accuracy of this material model, the benchmarks of NUMISHEET 2018 [3] are calculated and the calculation results are compared with experimental data. Good results are also obtaine when shell elements are used and another case where application of solid elements are necessary. In this paper, the analysis results of MAT289 or the other MAT models are compared with experimental results.

• Development of a Customized Beam-to-Shell Element Model Mapping Tool

  M. Duhovic, P. Patil, D. Scheliga, D. Schommer, L. Münch, J. Hausmann (Institut für Verbundwerkstoffe)

  A customized solution enabling the mapping of fiber orientations represented by beam elements in organic sheet materials from one simulation phase to another of the product development cycle has been developed using python scripting language. The strategy implemented for the mapping of the fiber orientations is based on the modeling approaches used for the input models in both types of simulation. The thermoforming simulation model consists of beam and shell elements representing the fiber and polymer layers in an organic sheet respectively while in the structural simulation, the component is usually modeled using only shell elements. The thermoforming simulation results (a .d3plot mesh) and structural simulation model input mesh are provided as inputs to the so called “BETA Mapper script”. The script segregates elements from each model into discrete volumes enabling parallel processing of the mapping procedure. The centroid coordinates of the elements from each matching cuboid are used to identify element pairs by finding the shortest distance between two element centroids. During the thermoforming process, the fibers, in the warp and weft directions of an organic sheet undergo a relative scissoring motion. In order to take this effect into consideration and to capture non-orthogonal fiber directions, the script is developed to produce three solutions and provides the possibility for mapping various types of part geometries. Developable geometries, which can be unfolded as a flat surface and do not exhibit any relative fiber scissoring, are mapped according to “Solution 1” and the part can then be simulated using assigned orthotropic material properties. “Solutions 2” and “3” implemented in the script, provide a methodology to enable the mapping of fiber orientations in two non-orthotropic directions in a single mesh model, which is not feasible with the generic approach using only one definition of the keyword (*PART_COMPOSITE). Additionally, “Solution 2” implemented in the script provides the user with the flexibility to choose the number of individual parts to be generated during the mapping. The method facilitates the realization of correctly mapped fiber orientations of the warp and weft yarns of an organic sheet in a single mesh model. With its three solutions, the “BETA Mapper script” provides the required data integrity between the different phases of organic sheet virtual product development and enables overall improvement in product design.

• Development of a New Method for Strain Field Optimized Material Characterization

  M. Benz, J. Irslinger, M. Feucht (Daimler), P. Du Bois (Consultant), M. Bischoff (University of Stuttgart)

  Due to technical progress, cars of the future will consist of even more different materials than they already do today. Especially plastic materials will experience a further increase of importance, as they provide advantages such as a low density and the freedom to shape them unconventionally. In view of this trend, it is essential to improve the quality of predictions derived from corresponding simulations. Modelling the material in an appropriate way is crucial when simulating a component. While in case of metals plastic deformation happens at a constant volume and therefore is easy to describe, this kind of incompressibility does not apply to plastics. Furthermore, the hardening behavior of these materials is usually significantly more complicated. Therefore, complex mechanical descriptions have to be used for the simulation of plastics, which describe hardening and failure in a multiaxial state of stress. Although those models have been available for some time, it is still cumbersome to calibrate their parameters. In particular, the correct prediction of the strain field, which is the key to characterize material failure e.g. with GISSMO [5], is challenging, as a large number of degrees of freedom have to be adjusted simultaneously.

• Development of a Process Simulation Model of a Pultrusion Line

  M. Duhovic, P. Aswale, D. Schommer, J. Hausmann (Institut für Verbundwerkstoffe)

  The applications for fiber reinforced plastic (FRP) composite structures have increased tremendously in the automotive and aerospace industries due to their lightweight nature. However, because of their high manufacturing cost, composite structures are typically only used for high-end parts. The reason behind this is the relatively low mass production rate of composite structures. Among the various composite manufacturing methods available, pultrusion is a continuous production process, meaning that the potential for mass production is there, if the process can be made fast enough. The process of pultrusion is defined as extrusion with pulling, in contrast with the conventional ‘extrusion process’, which is used for manufacturing uniform cross section structures such as circular bars, hollow tubes, I section beams etc. [1] [2]. Currently, pultrusion has a wide range of applications in the “architecture, transportation, construction, agriculture, chemical engineering, aircraft, and aerospace industry” [2]. On the basis of the polymer used in the manufacturing process, pultrusion can be divided into two types namely: thermoset and thermoplastic pultrusion. Many studies in the past have been conducted on thermoset pultrusion whose main advantage over thermoplastic pultrusion is the fiber impregnation, or ‘wetting out of the fiber reinforcement’ due to the resin’s low viscosity [3]. On the other hand, thermoplastic pultrusion can create parts which are recyclable, post formable, weldable, have excellent environmental stability and good mechanical properties such as high “fracture toughness, higher damage resistance” [1]. Due to such economic, environmental and mechanical advantages, many researchers have contributed to the development of thermoplastic pultrusion mainly in the field of fiber impregnation with thermoplastic resins [1] [4] [5]. With the advancement in thermoplastic prepreg technologies, pultrusion experiments with pre-consolidated tapes (PCT), powder coated tow-pregs and commingled yarns were performed and studied [1]. Moreover, in the early 1990s, thermoplastic pultrusion models were developed by researchers in order to understand the workings of the process [3] [6]. Most of the current research is focused mainly on investigating the effects of process and material parameters on the mechanical performance of the pultruded part. However, the interrelationship between the materials, process, and product is still not fully understood or has been incorporated into a complete CAE processing chain. The development of analytic, computational, and experimental approaches continues and the need of a fully developed simulation model, which can be used to optimize process parameters, avoid a trial and error approach and to improve productivity still exists.

• Development of a User-Defined Material Model for Sheet Molding Compounds

  D. Schommer, M. Duhovic, J. Hausmann (Institut für Verbundwerkstoffe), H. Andrae, K. Steiner (Fraunhofer ITWM), M. Schneider (KIT)

  The compression molding of Sheet Molding Compounds (SMCs) is typically thought of as a fluid mechanics problem. The simulation of such materials is at present based on the background of compression or injection molded short fiber reinforced materials. The usage of CF-SMC consisting of high fiber volume content (over 50%) and long fiber reinforcement structures (up to 50 mm) challenges the feasibility of this point of view. The goal of this work is the development of a user-defined material model based on a solid mechanics formulation for SMC materials in LS-DYNA®. To allow for large deformations in the simulation an Arbitrary Lagrangian-Eulerian (ALE) approach is used. As a first step, a material characterization is carried out in a so-called press rheometer test where the mechanical behavior of the SMC material is analyzed during the compression molding process. The resulting stress response of the material then serves as input information for the material model. The material model itself is based on a modular building-block approach. The individual modules describe certain aspects of the material behavior (e.g. compaction, plastic flow behavior or fiber orientation) and interact with one another through the passing of parameters between the respective modules. This procedure allows for the flexible development of the mathematical description for each part of the material behavior. Initially, a simple mathematical model describes every module. In the further development of the model, each module is expanded by more complex mathematical descriptions. As the overall goal is a work in progress, this paper shows the current implementation of several of these modules including the characterized compression and flow behavior as well as a description for the fiber orientation based on the Folgar-Tucker equation. By simulating the press rheometer test itself using the developed user defined material model, a comparison between simulation and experiments is performed to check the accuracy of the various mathematical models used. The stress response and the flow front development provide the basis for the comparison and provide clues on how to proceed with the further development.

• Development of Carbon Fibre Floor Structure for Premium Electric SUV

  P. Bristo (NIO)

  NIO are a global automotive startup producing electric vehicles for the China market. Our second vehicle, the ES6, was unveiled in December 2018 in Shanghai. It features a lightweight carbon fibre floor body structure, which will become the first high volume CFRP production part in ASIA. This presentation describes the CAE activities undertaken to develop the composite body structure. It explains the approach that was taken to construct the DYNA material cards and the various material tests used to validate them. It explores the various CAE activities used to develop and optimise the design of the parts and the layups of composite layers, and then the successful validation of the parts.

• Development of Pedestrian Headform Finite Element (FE)Model using LS-DYNA® and its validation as per AIS 100/GTR 9

  N. A. Kulkarni, S. R. Deshpande, R. S. Mahajan (The Automotive Research Association of India)

  Thousands of pedestrians die due to road accidents in the world every year. Head injury is more life threatening and most common cause of pedestrian deaths in pedestrian to vehicle collision. To reduce rate of pedestrian death, international safety committees have developed test in which headform impactors are impacted upon car vehicle front structure (bonnet) and approval is given based on headform acceleration within specified range.

• Development of Simple Connection Model for Plastic Parts in Low-Speed Crash Simulation

  N. Matsuura, Y. Nakagawa, O. Ito, K. Kaneda, Y. Ueda (Honda R&D)

  Collision performance is evaluated by CAE not only for metal parts such as steel and aluminum but also for plastic parts. As it takes time to create molds for a large part such as the bumper face, ensuring the performance by pre-calculation is important to shorten the development period. When mold production is started prior to the test to reduce the development time and if failures occur in the test, it will take time and cost to modify the mold. Therefore, high calculation accuracy is desired, but the test reproducibility is not satisfactory in some areas. Out of those areas undergoing enhancement efforts, this document introduces our efforts for plastic parts connection coming-off.

• Dimensionality Reduction of Crash and Impact Simulations using LS-DYNA

  C. Bach (BMW/Technical University of Munich), L. Song (BMW), T. Erhart (DYNAmore), Prof. F. Duddeck (Technical University of Munich/ Queen Mary University of London)

  Automotive crash simulations of full vehicle models still constitute a large computational effort which can be a major problem for applications requiring a large number of evaluations with varying parameter configurations. In some applications, highly similar simulations frequently need to be carried out multiple times with only minor local parameter modifications. At the same time, large amounts of numerical simulation data increasingly become available in industrial simulation databases as part of the progressive level of digitalization of automotive development processes. Data-driven modeling methods are an area of active research, aiming to exploit this new “treasure” in order to find interesting patterns and accelerate predictions.

• Drag Force Simulation on Blast Loaded Fabric Roof

  M. Hadjioannou, E. Sammarco, M. Barsotti (Protection Engineering Consultants)

  An important consideration in predicting the dynamic motion of highly deformable structures subject to blast loads is the effect of drag force. A representative example of this condition is a blast-loaded non-breathable fabric roof, typically used for tents or other aesthetic fabric structures. A fully coupled fluid-structure interaction (FSI) analysis to simulate the interaction of the fabric roof with the air domain is theoretically possible, but is complex and requires significant computational effort. This study presents an alternative approach of including drag force in LS-DYNA® without the need to employ any form of computational fluid dynamics (CFD). Using the keyword *LOAD_MOTION_NODE, the velocity component of each node of the roof fabric elements is used as a variable to calculate the nodal drag force using the dynamic pressure equation. The calculated drag force is then applied at each time step as a nodal force that is opposite to the direction of motion and parallel to the element normals that represent the roof fabric. Results from a validation study using this approach are presented, and a case study involving the response of an arched roof fabric canopy subjected to blast loads is also discussed.

• Dynamic Load Balancing

  B. Wainscott (LSTC)

  MPPDYNA begins each simulation by splitting the model into multiple pieces (domains), and assigning each domain to a CPU core. This is referred to as “domain decomposition.” Efficient MPP processing requires that, as much as possible, every CPU core is kept busy doing useful work. That is to say, each domain should represent the same amount of work to be done. If one core is assigned a domain that is too large, then at certain points in each timestep cycle the other cores will be idle, waiting for this core to finish its calculations. The initial decomposition is based primarily on measured execution times for the different types of elements and the different material models. And it has been the case that once the domains are determined, they persist through the duration of the calculation. This approach has two significant problems. First, the element costs used during decomposition are not perfectly accurate. As material types are added, routines are modified, compiler options changed, and new CPUs are available, keeping this decomposition timing information up to date is simply infeasible. But even if that could be done, the second issue is that for most materials the computational cost of the material changes during the calculation. As elements distort, or exceed their elastic limit and begin to experience plastic deformation, the element evaluations can become more time consuming. This leads to the inevitable conclusion that any static decomposition will result in at least some computational imbalance. As core counts increase, the need for dynamically adjusting the decomposition will also increase.

• Effect of side incubator padding on unrestrained child crash dummy under deceleration force

  Ali Rabiee (Cranfield University)

  Nearly 20 million low birth weight and premature infants are born each year in developing countries, 4 million die within their first month due to unavailability of incubators and neonatal intensive care. Neonates and infants that require an inter-hospital transfer or ambulance/vehicle transfer in an incubator could potentially face fatal and catastrophic events, once subjected to negative acceleration. The main factor affecting the applied force due to the harsh braking or collisional accidents to the neonate/infant is the configuration of the restraining system. By eliminating the restraining system or having low residual strength seat belts the neonate or infant can experience lifelong injuries or even death. The interior of an incubator in case the restraining system fails must be designed to protect the occupant. In this paper, the effect of the paddings on the incubator wall against the unpadded wall is studied on a crash dummy using LS-DYNA software. The deceleration pulse, velocity, and displacement are validated by a sled test at Cranfield Impact Centre (CIC).

• Efficient Characteristic Identification of Plastic Materials for Crash Analysis with 3-Point Bending Machine

  O. Ito, Y. Nakagawa, K. Kaneda, N. Matsuura, Y. Ueda (Honda R&D)

  According to WHO’s report, there are over 270,000 people who are involved in traffic fatal accidents [1]. Based on this accident data, the third-party assessment organization performs pedestrian protection test to evaluate a vehicle safety performance [2]. The pedestrian protection tests are evaluated for the protective performance of a head and legs of pedestrian. In particular, plastic parts such as a bumper face, a grille and head lights are evaluated by the leg pedestrian test. On the other hand, low speed crash test regulated by the United Nations evaluates a bumper protection performance (ECE42). In general, the pedestrian and bumper protection performances are in a trade-off relationship. Therefore, it has become important to balance these performances because the country which does the pedestrian protection test is increasing in recent years. In order to design these performances, it is essential to use the plastic CAE model with high accuracy. However, there are many types of characteristics for the plastic parts compared to the steel parts. It is an issue to collect the material properties for the many plastic parts in author’s development environment. Investigating the past literature to solve this issue, we found that Reithofer et al.[3] developed the machine and method to create the material property for CAE in a short time. So this study is to validate that the machine can be used efficiently to identify the material property for the pedestrian protection and low speed crash.

• Enabling the Analysis of Topologically Connected Multi-Patch Trimmed NURBS Shells in LS-DYNA

  S. Hartmann (DYNAmore), L. Li , A. Nagy, M. Pigazzini, D. Benson (LSTC), L. Leidinger (BMW)

  In 2005, the term “Isogeometric Analysis” (IGA) was introduced by Hughes et al. [1]. Since then, reams of scientific research work has been devoted to this new finite element technology, whose main idea is to use the same geometrical description during the finite element analysis (FEA) that was previously used during the design process in the computer-aided design (CAD) environment. The most widely used and best understood mathematical description in CAD is based on non-uniform rational B-splines (NURBS). Hence NURBS-based shell and solid finite elements have been developed and implemented into LS-DYNA over the last few years. Although NURBS-based solids are available, the remainder of the paper will exclusively focus on isogeometric shell element formulations in LS-DYNA.

• Estimation of Spot Weld Design Parameters using Deep Learning

  A. Pillai (TU Dresden), M. Thiele (SCALE), Prof. U. Reuter (TU Dresden)

  In automotive production, each automobile has approximately 7,000 to 12,000 spot welds along with other kinds of connections. The position of the spot weld with respect to the flange and the distance between the spot welds as well as various other parameters usually vary for each part combination (spot weld design). If these properties are known, they can be used for automatic generation of spot welds during the design phase of the product development which is otherwise a cumbersome manual process. The spot weld design to be determined by the engineer depends on many factors (input parameters) such as loads and forces that might be applied to the structure, material combination, geometry of the parts, connection technology and its process parameters. Some of these parameters such as material combination and geometry of the parts are predefined by the designer or are results of the circumstances such as loads and forces applied at the connection. The remaining parameters such as connection technology, process parameters, spot weld distances and flange distance have to be chosen by the engineer. On the basis of existing designs and with help of machine learning techniques it may be possible to predict the spot weld design parameters like spot weld distance and flange distance. Within this work existing spot-weld designs are extracted from a vast amount of FEM simulation input data available in the Simulation Data Management (SDM) system LoCo of SCALE GmbH and applied as the basis for training and benchmarking new methods for estimating spot weld parameters.

• Estimation of Stress Triaxiality from optically measured Strain Fields

  S. Conde, F. Andrade, M. Helbig, A. Haufe (DYNAmore), M. Feucht (Daimler)

  Nowadays, strain fields can be experimentally measured with high accuracy through digital image correlation (DIC). This kind of measurement is becoming standard when it comes to physical testing of materials. The information from such measurements is then often used in the calibration and validation of material cards to be later used in LS-DYNA. Especially regarding the prediction of failure, the experimentally measured strain fields can be quite helpful. Among several methods for the calibration of material cards, one method relies on the direct use of such strains in the definition of the failure curve as a function of the stress triaxiality ratio. However, in such method, the triaxiality is usually estimated from the simulation of the specimens adopted in the physical tests or, sometimes, it is estimated from analytical calculations based on the loading type and on the geometry of the specimen. It is however widespread known that the triaxiality typically varies during experiments. Therefore, it would be interesting to observe the evolution of the triaxiality throughout the physical test. As mentioned before, the typical way of doing this is through the use of numerical simulation to perform this task. In this paper, we concentrate efforts in developing a method to estimate the triaxiality distribution and evolution using information directly from the DIC measurement. To that end, a plane stress state is assumed and the strain ratio is calculated from the measured strains. The stress triaxiality ratio is, in turn, a relation between the hydrostatic and the equivalent stress. Therefore, in order to calculate the triaxiality from the strain field, a relationship between the strain ratio and the triaxiality has to be defined. This is only possible through the consideration of a constitutive (i.e., material) model. Typically, the J2-based plasticity model (commonly known as the von Mises model, e.g., *MAT_024 in LS-DYNA [1]) is used for this kind of task. However, our research on the topic has shown that this assumption may lead to wrong triaxialities even in cases when the triaxiality is known beforehand, for instance, in a uniaxial tensile test before necking. This error can be significantly reduced if the anisotropy of the material is also taken into account. To that end, we use a Hill-based transversely anisotropic material law in order to consider the effect of the anisotropy. After some mathematical derivations under the assumption of plane stress, negligible elastic strains and proportional loading, it is possible to find a closed-form relation between the strain ratio and the triaxiality including the effect of the R value. The results for an aluminum sheet show that the triaxiality is much better predicted using the new formula. Using a software dedicated to the evaluation and visualization of optically measured strain fields, it should be possible to plot triaxiality fields from experimental data that can be later used either for the calibration or validation of a material card. Furthermore, this novel technique can also be employed on the development of new specimen geometries in order to better assess the stress triaxiality ratios obtained with the new geometry without having to first calibrate a material card for that.

• Evaluation of Simulation Results using Augmented Reality

  M. Lechner, R. Schulte, M. Merlein (University of Erlangen-Nürnberg)

  Simulation has become an important tool in order to design forming processes in a time and cost efficient way. However, simulation results are almost exclusively visualized using conventional laptops or personal computers. Especially, in the press shop an analysis directly at real parts is not possible at the moment. At the same time, there has been a very convincing development in the field of Augmented Reality hardware in recent years. In particular, the iPhone and the iPad of the company Apple as well as the HoloLens of the company Microsoft offer interesting solutions for the industry. Thereby, the Augmented Reality applications are until now limited to CAD-data or assembly problems. Therefore, within scientific contribution a method to visualize simulation results from LsDyna in a simple way is presented. It will be explained, how new simulation results can be loaded on runtime and which use cases can be derived with the technology. In the end, Augmented Reality solutions with HoloLens as well as iPhone/iPad will be compared and evaluated.

• Experimental and Numerical Study of Submillimeter-Sized Hypervelocity Impacts on Honeycomb Sandwich Structures

  F. Plassard (Thiot-Ingenierie), H. Abdul-hamid, P Deconinck, P-L Héreil, J. Mes-poulet (Thiot-Ingenierie), C. Puillet (CNES)

  This paper deals with hypervelocity impacts of submillimer-sized debris on honeycomb sandwich panels. These debris, which are mostly present within the low Earth orbit, indeed represent a real threat for spacecrafts and satellites. In fact, for debris large enough to be tracked, pre-determined debris avoidance manoeuvre is usually conducted to prevent any damage. Submillimer-sized debris, however, are too small to be identified and therefore spatial structures must be protected against such threat. Honeycomb structural panels and whipple shields have been used as primary shielding against orbital debris impact. The protection capability is usually estimated using Ballistic Limit Equations (BLE). These data have been built from experimental tests on whipple shield protection and transposed to honeycomb sandwich panels. In the case of Whipple shield, the debris cloud generated at the impact on the bumper sheet expands until reaching the rear wall. BLE for Whipple shields only depends on materials properties, protection geometry, angle of incidence and impact velocity. For honeycomb sandwich panels, the debris cloud is partially channelled within honeycomb cells, thus limiting its radial expansion. The channelling effect is thus a function of the honeycomb cell geometry. The honeycomb BLE presented by the Centre d’Etudes de Gramat (CEG) in 2008 has been introduced in order to take into consideration such effect.

• Expert Rules as a Powerful Support of the Topology Optimization Procedures of Crash Structures

  Prof. A. Schumacher (University of Wuppertal)

  Topology optimization for the layout finding of structures is commonly used for linear static mechanical problems within the industry. The most often used approach is the subdividing of the topology domain in small parts (pixel or voxel) and to distinguish whether there is material or not [1]. E.g. the well-known homogenization method minimizes the mean compliance considering a mass constraint. These methods work very fast, because they use existing analytical sensitivities of the most relevant objectives like mean compliance, stresses or mass.

• Expert Rules as a Powerful Support of the Topology Optimization Procedures of Crash Structures

  Prof. A. Schumacher (University of Wuppertal)

  Topology optimization for the layout finding of structures is commonly used for linear static mechanical problems within the industry. The most often used approach is the subdividing of the topology domain in small parts (pixel or voxel) and to distinguish whether there is material or not [1]. E.g. the well-known homogenization method minimizes the mean compliance considering a mass constraint. These methods work very fast, because they use existing analytical sensitivities of the most relevant objectives like mean compliance, stresses or mass.

• Explicit Isogeometric B-Rep Analysis on Trimmed NURBS-Based Multi-Patch CAD Models in LS-DYNA

  L. Leidinger (BMW)

  A volatile and highly competitive market forces automotive Original Equipment Manufacturers (OEMs) to speed up their vehicle development processes. A key component in this process is structural design through Computer Aided Design (CAD) and Finite Element Analysis (FEA). Although the efficiency of this process has been significantly improved over the past years, the necessary conversion of NURBS-based CAD models into (linear) polynomial-based FEA models turned out to be a persistent challenge. Generating FEA models usually involves time- and labor-intensive clean-up, de-featuring and meshing steps leading to vehicle model generation times of several weeks. During the iterative vehicle development process, such model generations are even performed multiple times. It is furthermore current practice to apply design changes motivated by structural analysis results directly on the FEA model, which then diverges more and more from the initial CAD model. Adapting the CAD model to the modified FEA model for the next design cycle again requires a significant amount of manual work.

• Failure Modeling of Unreinforced and Fiberreinforced Thermoplastics

  P. Reithofer, B. Hirschmann, T. Schaffranek (4a engineering)

  In the last years the demands of the automotive industry have led to a strong interest in a more detailed virtual description of the material behavior of thermoplastics. More and more complex material models, including damage and failure, have to be characterized, while keeping the importance of gaining material data quickly in mind. Currently material and failure modeling in crash simulations typically deal with simple von Mises visco-plasticity (*MAT_024) and equivalent strain failure criteria, which cannot describe the complex material behavior of plastics. Past developments have focused on the yield behavior under different load situations (tension, shear, compression), which are implemented in more complex material models like *MAT_SAMP-1 for thermoplastics as well as *MAT_215 for fiber reinforced thermoplastics.

• Failure Prediction for Polymer Products with Short Fiber

  J. Takahashi, Y. Fujita (Asahi Kasei)

  Polymers have been often used as structural materials under mechanically severe conditions instead of metals. We usually use FEM simulation when we design polymer products. The failure prediction of impact is especially important because its effect for reduction of development duration and number of trial products cannot be disregarded. The failure prediction has been investigated for a long time [1][2]. We generally start impact simulations using elasto-plastic material such as MAT_024 by giving stress-strain curves with strain rate dependency. We often add our own research achievement about material model by the user defined material models which LS-DYNA offers us to improve prediction accuracy. We developed the isotropic material model based on damage of polymers and introduced it into LS-DYNA by using user subroutine “*MAT_041-050”. We found many good coincidences between experimental impact test and numerical results with our material model. After that, we found the reason why we got good coincidence by simulation with isotropic material model was that glass fibers in the structural specimen of these experimental tests align well at the impact area. Therefore, we decided to start simulations for structural specimens with various fiber distributions. Differences between the isotropic simulation results and anisotropic results are recognized. The importance for taking fiber orientation into account in impact simulations is known [3]. Then, we conducted the experimental impact tests using structural specimen made of Polyamide 66 with 35 weight% short fiber (ASAHI-KASEI LeonaTM 14G35). We set different fiber distribution by giving two gate types in injection molding. In this paper, the effect of introducing fiber distribution is discussed.

• FE approach to evaluate the dynamic friction coefficient for the transient phase of rubber-ice sliding interaction

  R. Leonardi, S. Scalera (DYNAmore Italia), A. Scattina (Politecnico di Torino)

  The improvement of tractive performance on ice is one of the most challenging aspect in the nowadays tire industry. For this reason, a model which can predict the friction coefficient on ice can be useful in the winter-tire design. However, the highly multiphysics nature of the interaction between rubber and ice [1-4], as well as the magnitude of the dimensions involved make the development of a numerical model a quite complex issue. In this work, a first step for the prediction of the friction coefficient on ice is proposed using the finite element method. The subject of this analysis is the transient phase of the sliding interaction between a rubber block and an ice surface. The User Define Friction module of LS-DYNA has allowed to implement the suitable friction law for contacts with ice, widely used in the literature [3, 5], which follows a microscopic approach and it is based on a viscous formulation. Considering again the dimensions involved and the duration of the transient phase, it is impossible to directly validate the model through experimental detection [3]. However, in the subsequent steady-state phase, which involves higher amounts of water and longer time, the experimental measurements are easier. To compare the results, in the literature an indirect procedure was used in order to provide a qualitative validation, using the strict link between the transient phase and the steady-state one. The final comparison between the LS-DYNA results and the literature results has shown a good correlation level.

• FEM-BEM Coupling with Ferromagnetic Materials

  T. Rüberg, L. Kielhorn, J. Zechner (Tailsit)

  Eddy current problems are typically modelled by a combination of Ampère’s law, Ohm’s law, the non-existence of magnetic monopoles and Faraday’s law of induction. Using a magnetic vector potential A, such that the magnetic flux intensity is given by B = curl A, we end up with the equation σ ∂ t A + curl ν(A) curl A = Js [1]. Here, Js are applied source currents, ν(A) the magnetic reluctivity whose dependence on A implies the possible non-linearity of the material behaviour, and σ is the electrical conductivity. In most applications, the domain of interest consists of conducting (e.g. metal parts) and non-conducting regions (e.g. air). In the non-conducting regions, the part σ ∂ tA is dropped from the equation and the model is that of magnetostatics.

• First Steps Towards Machine-Learning Supported Material Parameter Determination

  D. Koch, A. Haufe (DYNAmore)

  Machine learning is becoming more and more part of our world. Even though most people have so far only passively used the possibilities of this technology, e.g. for search queries or product recommendations, many have surely already thought about how these new possibilities could support their work in the future. In this contribution, it is investigated if machine learning is suitable to support the process of material characterization. Through deep neural networks it is possible to "learn" nonlinear relationships between a set of input values and the corresponding output, also known as labels. As a proof of concept, it is examined whether the shape of the yield curve can be predicted based on force-displacement curves from simulated tensile tests. So, in a first step, a large number of tensile tests are simulated which differ in the shape of the yield curve. Here, for the description of the yield curve an approach according to Hockett-Sherby was used which provides 4 parameters for the definition of the shape. The force-displacement curves of these tests are used as the input and the parameters of the yield curve as labels. By considering the entire realistic range of all four parameters, the trained neural network should be able to provide the best matching set of parameters for a given force-displacement curve. For the prediction, of course, the initial and boundary conditions must be the same when generating the force-displacement curve, whether by simulation or in a real test. Of course, all initial and boundary conditions as well as all other assumptions and simulation settings are also learned from the neural network. Therefore a change of these parameters can for sure worsen the predictions considerably and can make a re-learning process inevitable. The long-term objective of this method and the vision of this work are to learn the possible spectrum of the whole material model in advance in order to be able to finally predict the material properties based on only a few experiments with minimal effort.

• Fluid-Composite Structure-Interaction in Underwater Shock Simulations

  B. Özarmut, A. Rühl, B. Hennings, O. Nommensen, A. Paul (thyssenkrupp Marine Systems)

  Fiber reinforced plastics (FRP) and sandwich components are widely made use of in today’s submarines owing to their advantages such as high strength-to-weight ratio and durability in marine environment over conventional submarine building materials. Fig. 1 shows a state-of-the-art conventional submarine with an upper deck consisting of mostly composite components.

• High Velocity Impact Response of High Strength Aluminum using LS DYNA

  G. Başaran, E. Özbayramoğlu, O. Bütün, E. Öney (FNSS Savunma Sistemleri), Prof. E. Gürses (Orta Doğu Teknik Üniversitesi)

  Experimental and numerical studies were conducted to determine the impact response for high strength aluminum armor. A series of ballistic impact tests were carried out for the impact of a 20mm Fragment Simulating Projectile (FSP) with 25.4mm high strength aluminum armor plate at 960m/s impact velocity. This study deals with the measurement of ballistic limits of the deformable FSP against high strength aluminum armor material. The numerical models were developed using the explicit finite element code LS-DYNA®. All parts in the model are modeled with Modified Johnson-cook material model calibrated with performed tests in the company. Material properties are not shared due to confidential issues. A high-speed camera was used for calculation of projectile residual velocities and projectile output images. The numerical model was validated with live test results and a good agreement was achieved between experiments and numerical results. Parameter sensitivity analyses were performed to examine the effect of material model‘s parameters on the response.

• High-Strength Alloyed Steel: Modelling Dynamic and Multiaxial Loading Conditions

  A. Trippel (Institut für nachhaltige technische Systeme), W. Harwick (Fraunhofer EMI)

  This work reports on the modelling of failure behaviour in case of a high strength alloyed steel, experimentally subjected to a range of strain rates and states of stress triaxiality. This material combines high strength with exceptionally high ductility, which makes it difficult to describe material behaviour based on well-known constitutive models such as Johnson-Cook [1] [2]. To solve this challenge, extensive experimental investigations were performed to record stress-strain relations and, in particular, failure behaviour. Different states of triaxiality were attained based on the specimen geometry. Experiments with flat, unnotched and notched specimens yielded triaxial stress-states under uniaxial loading conditions. Stress-states due to shear stress and combinations of shear and tensile stresses were studied with biaxial tensile specimens. The triaxiality of the uniaxial tensile specimens was calculated based on the approximation suggested by Bridgman [3]. Based on the detected data, the material models suggested by Johnson-Cook [1] [2] was parameterized. Parameterization was carried out with the software LS-OPT [5]. The parameters of the constitutive models were found in an optimization procedure which minimized the difference between simulation prediction and experimental results. The discretization and element size was varied in order to study discretization effects. Smaller element sizes enabled a more constant triaxiality over the duration of the simulation. The parameter space of the Johnson-Cook model allowed for a satisfactory agreement in case of uniaxial experiments with a value of the stress triaxiality ≥ 1/3. However, the more complex problem of accurately modelling failure at other values of stress triaxiality between 0 (pure shear) and 1/3 (uniaxial tension) could not be solved. We discuss possible reasons for the apparent inability of the Johnson-Cook failure model to describe the effects induced by triaxiality at large failure strains and under shear stresses.

• Impact Analysis of Polymeric Additive Manufactured Lattice Structures

  G. Laird (Predictive Engineering), P. Du Bois (Consultant)

  This work was sponsored by the US Army’s Natick Soldier Systems Center to investigate additively manufactured lattice structures for improved blunt impact protection for helmets. The idea is simple enough, modern helmets are designed to deflect or mitigate the impact forces due to bullets (high velocity) but not so much for blunt force impacts (lower velocity). In military operations, blunt force impacts are common, albeit sometimes accidently, due to falls or in the rush to enter-exit buildings and vehicles. In combat, flying debris also present challenges to helmet designers where the impacts can be both high- and low-velocity. Our work was to set the foundation for the exploration of polymeric 3D lattice structures to create the next generation of energy-absorbing helmet liners for military applications. Current foam liners, whether multi-layer or sculptured, all exhibit more-or-less the same energy-absorbing response which is fine for high-energy impacts but lacks the sensitivity for low-energy impacts. If one can move away from the use of foam and toward that of a 3D polymeric lattice structures, then it should be possible to engineer a helmet liner to have a more variable or tailored energy-absorbing response. To create such structures, the additive manufacturing process was used.

• Impact Simulations of Fiber Reinforced Plastics with LS Dyna and Digimat

  M. Palm (Husqvarna Group)

• Implementation of a Method for the Generation of Representative Models of Polycrystalline Microstructures in LS-PrePost

  S. Falco (Imperial College London), N. Bombace, N. Petrinic (University of Oxford), P. Brown (DSTL)

  The capability of accurately reproducing the microstructural features of polycrystalline materials is of fundamental importance for the correct simulation of the micromechanical behaviour of materials. This paper describes the development and the implementation of VorTeX algorithm for the generation of numerical models representative of real polycrystalline microstructures, and its integration within LS-PrePost. The method presented offers high control over the grain size distribution of the final structure by adopting the so-called Laguerre-Voronoi tessellation techniques. Additional features implemented allow constraints to be imposed on the structure such as symmetrical boundaries and enables the introduction of interface entities (i.e. contacts and cohesive elements) on the grain boundaries to model inter-granular crack propagation.

• Implicit SPH in LS-DYNA for Automotive Water Wading Simulations

  E. Yreux (LSTC)

  The explicit SPH solver implemented in LS-DYNA is well fitted for numerical simulations involving hypervelocity impacts, explosions and other transient events, but is unsuitable for slower fluid-flow simulations such as water wading. In this work, we introduce an implicit SPH formulation specifically developed for handling large-scale incompressible fluid simulations. The method is based on a traditional projection scheme: Intermediate velocities are first predicted based on external and viscosity forces contribution, and a Poisson equation is then solved to obtain pressure forces such that incompressibility is maintained up to a given tolerance. All the surfaces composing the structure are automatically sampled with SPH particles by LS-DYNA using a user-supplied maximum interparticle distance, and the fluid-structure interaction is embedded in the SPH solver directly. This aspect of the simulation does not require any contact card to be setup. As the simulation evolves, the initial domain decomposition performed by LS-DYNA can become inefficient, triggering increasing communications across processors and poor load balancing, resulting in an increasing CPU time per simulation cycle as the SPH fluid particles intermix. A new feature has been developed based on the full-deck restart capability of LS-DYNA. The objective is to re-decompose the domain across processors at regular intervals, based on the updated geometry of the problem. This results in a more constant simulation time and overall improved performance.

• Improvement of Satellites Shielding under High Velocity Impact using Advanced SPH Method

  T. Legaud, M. Le Garrec, N. Van Dorsselaer, V. Lapoujade (DynaS+)

  A huge number of debris coming from human activities is currently gravitating around Earth. Their size, their nature, their orbit and their velocity can highly vary, but they all represent an increasing risk of collision and a threat for the current and future space activity [1]. The space actors are looking for solutions in order to limit these risks and to protect the structures from impacts and generation of new debris (spacecrafts conception, limitation of the debris multiplication, waste life stage strategies…).

• Increasing CAE Productivity – Airbag Model Verification using Visual-Environment

  N. Möwe (iSi Automotive), M. Sommer, A. Gittens (ESI)

  Technological advancement, customer expectations and globalization have increased the need for higher productivity in any industry. In general, productivity is a measure of performance or output. There are various proven methods/techniques to increase and improve productivity. One such proven method is through adoption of Automation, the technology by which a process or procedure is performed with minimum human assistance and interaction.

• Influence of Strain Rate on Deformation and Failure Behavior of Sheet Metals under Shear Loading

  S. Klitschke, A. Trondl, F. Huberth (Fraunhofer IWM)

  In order to improve the reliability of deformation and failure prediction of automotive lightweight con-structions in real crash situations, appropriate input data for crash simulations are necessary which re-present the material behavior under high strain rates and complex multiaxial loading situations. Espe-cially under shear dominated loading failure is difficult to reach and there is still a lack of information concerning the strain rate dependency under these loading conditions. Therefore an experimental pro-cedure for strain rate dependent shear tension tests on sheet metals was developed which bases on asymmetrical notched shear tensile specimen geometries without surface processing. The specimen design of the shear zone was optimized by varying the shear length dependent on the sheet thickness and the notch position dependent on material data of uniaxial tension tests. For different advanced high strength steels (AHSS) numerical and experimental investigations were performed regarding the evolution of load paths in the shear zone and near the notch region as well as the failure location. Based on these experimental results and related numerical simulations recommendations are derived for an optimized design of asymmetrical notched shear tensile specimens. These recommendations are dependent on the sheet thickness and on material properties. The experiments should be carried out comparable to strain rate dependent flat tension tests with an appropriate mounting. The sugges-ted specimen design procedure is validated by experiments on steels in a wide range of strength as well as on exemplary batches of aluminum and copper. The shear characterization for AHSS results in large strain values in the shear zone up to failure under quasi-static loading with a significant negative strain rate effect. These experimental results of improved strain rate dependent shear characterization can be used for enhanced failure prediction in the future.

• Investigation on Parameter Identification and Coarse Graining Models using Discrete Element Capability in LS-DYNA

  S. Tokura (Tokura Simulation Research)

  Processes such as transportation, flowing and processing of powder materials can be seen in the manufacturing process of various industrial products and are important processes for manufacturing high quality products. Discrete Element Method (DEM)[1] is widely used as a simulation method to handle powder materials, and excellent DEM function is also implemented in LS-DYNA. The DEM model can be used intuitively, and there is an advantage that stable computation can be performed. On the other hand, the DEM model is a hypothetical model based on the spring-mass model, and in order to reproduce the real phenomenon with high accuracy, it includes many numerical parameters that the user must decide beforehand. In this paper, the simulation of a compression experiment of polymer pellets were performed and the result of the parameter identification using optimization software LS-OPT is reported. In addition, when DEM is applied to fine powder material, the number of particles becomes enormous, and in many cases it cannot be processed in a common computational environment. In such a case, a coarse graining model is used to reduce the number of particles and computational load. Various ideas have been proposed for the method of coarse graining so far, and in this paper several coarse graining models were tested to compare powder behavior in drum mixing problem.

• IRIS 3 Program: Study of the Vibrations Induced by a Missile Impact on a Reinforced Concrete Structure

  N. Van Dorsselaer, T. Legaud, V. Lapoujade (DynaS+), B. Richard (Institut de Radioprotection et de Sûreté Nucléaire)

  The IRIS program (Improving Robustness assessment of structures Impacted by a large miSsile at medium velocity) consists in an international benchmark under the hospice of OECD/NEA. After two first phases of this benchmark realized in 2010 and 2012 which aimed at assessing the ability of numerical simulations to describe the experimental structural response of the mock-up when subjected to impacts, the IRIS Program is now in its third phase. The main objectives of this phase are to assess the effect of a local damage caused by a missile impact on the induced vibrations and to assess the propagation of these vibrations to other parts of the structure, especially to pseudo-equipments which are anchored on it.

• Isogeometric Analysis using the *IGA_INCLUDE_BEZIER Keyword in LS-DYNA

  M. Sederberg (Coreform), M. Scott (Brigham Young University/Coreform)

  In contrast to the laborious and error-prone process of translating computer-aided design (CAD) into computer-aided engineering (CAE) models, isogeometric analysis (IGA) performs the finite element analysis (FEA) simulation directly on CAD geometry, using smooth spline basis functions. LS-DYNA is a leader in the industrial adoption of IGA, and has recently made a significant enhancement to broaden the possible use of IGA within LS-DYNA.

• Leveraging LS-DYNA Explicit and Implicit on Latest Intel Technologies

  N. Meng (Intel), J. Wang, R. Lucas (LSTC)

  In this paper we discuss Intel’s continued optimization efforts with LS-DYNA® and demonstrate the impact of new Intel technologies. Two different approaches to exploit Intel® Advanced Vector Extensions 512 (AVX-512) are shown: LS-DYNA® Explicit using Intel compiler vectorization techniques and LS-DYNA® Implicit using Intel® Math Kernel Library (MKL) for accelerating dense matrix computational kernels. Numerical accuracy of simulation results for LS-DYNA® Explicit comparing Intel® SSE2 and Intel® AVX-512 is also explored. Finally, we reveal the benefits of Intel® Optane™ DC Persistent Memory technology for LS-DYNA® Implicit simulations. For our studies we used the Topcrunch benchmarks, ODB-10M & car2car models, for LS-DYNA® Explicit and AWE benchmarks, CYL1E6 & CL2E6 models, for LS-DYNA® Implicit

• Lithium-Ion Battery Models and Thermal Management in LS-DYNA

  K.-S. Im, Z.-C. Zhang, G. Cook Jr. (LSTC)

  We have developed two Lithium-ion battery models in LS-DYNA®: i) a single insertion lithium metal model, and ii) a dual insertion composite model. Our models are intended to assist users in tackling problems ranging from the fundamental battery cell physics to very complex situations such as thermal management (TM) of electric vehicle (EV), and eventually, battery-structure-interaction (BSI) problems. The battery models in LS-DYNA® are based on the following multiphysics aspects: 1) thermodynamics, 2) kinetics, and 3) transport. In thermodynamics, the role of electrochemical potential, which is the driving force in the concentrated solution will be discussed, and an example will be provided as to how to set up the open-circuit potential card in the keyword input. Detailed presentation of Bulter-Volmer kinetics illustrates how to correctly evaluate the surface overpotential at the interface between electrode and electrolyte, and also the pore-wall flux from the insertion materials in compsite electrodes. In addition, comprehensive keyword set up for the transport properties in both aqueous and polymer electrolyte will be provided, including the concentrated material transport theory. For the thermal treatment of the battery model, we have coupled with existing thermal solver and structure solver and thus, we will present a keyword example showing how to simulate a thermal problem in a battery cell stack, module and pack in the practical scaled-up EV application. Finally, we will provide the future development plan to handle more complex problems confronting the battery related industries by using BSI solver in LS-DYNA®.

• Load Case Preference Patterns based on Parameterized Pareto-Optimal Vehicle Design Concept Optimization

  S. Ramnath (Ohio State University), N. Aulig, M. Bujny, S. Menzel (Honda Research Institute Europe), I. Gandikota (LSTC), K. Horner (Honda R&D Americas)

  Classical Topology Optimization (TO) methods aim to optimize the distribution of material within a design space for one given objective function and constraints. However, in the vehicle design process, there are many different load cases and several different objectives. Among them maximizing stiffness of components for regular working conditions, and maximizing energy absorption in exceptional loading conditions, for instance in crash events, are important. Recently, the Scaled Energy Weighting Hybrid Cellular Automata (SEW-HCA) [1], [2] method was adopted in LS-TaSC™. The SEW-HCA is a practical multidisciplinary TO approach for devising concept structures based on the intuitive choice of preferences leading to the desired trade-off between crash performance and stiffness. In this paper, we propose an integration of the SEW-LS-TaSC method into LS-OPT® to perform a design of experiments (DOE) on the load case preference parameters. The integration into LS-OPT® results in a convenient user interface that facilitates application in an industrial development process with non-expert users. This integration enables quick studies on many different concept designs based on preference samples generated by the DOE. The results from the sensitivity analysis provide data for a better understanding of the influence of load case preferences on the design space. By comparing the performance of structures obtained for different load case preferences, the user will be able to find a desired trade-off solution within the concurrent optimization runs. For further development, the proposed LS-OPT® workflow can potentially include 1) NVH load cases as additional discipline and 2) optimizations of other topology optimization hyperparameters for further concept exploration.

• Low-Velocity Impact Behaviour of Plain Concrete Beam

  D. Memon (Ghent University), D. Lecompte (Royal Military Academy of Brussels)

  Concrete structures are designed and constructed to serve their anticipated service life, generally with minimal consideration of accidental loads such as impact or explosion. The behaviour of reinforced concrete structures under impact loads has been widely discussed in the last decades, however, there are few studies on the behaviour of plain concrete under impact loading. This paper presents a finite element model of plain concrete beams using nonlinear finite element analysis. The numerical results are compared to experimental data taken from an existing study. The experiments consist of drop-weight tests with varying drop-heights. A parametric study is conducted with respect to the concrete material model and mesh size of elements in order to fine-tune the model and to understand the dynamic response of the beam under low-velocity impact load.

• LS-DYNA Automatic Re-Decomposition

  E. Yreux, C. Tsay, J. Wang (LSTC)

  The default decomposition method for LS-DYNA/MPP is RCB which dividing the model based on the initial geometry. If the geometry does not severely distorted during the simulation, this decomposition gives reasonable scaling upto few hundreds cores. LS-DYNA also provides additional “pfile” options which relies on user’s knowledge of deformation to achieve better MPP efficiency. Unfortunately, there are many problems cannot be easily treated by those options, i.e. bird strike, water wading, FBO, etc. The simulations involve parts with relative motion which are difficult to decompose only once and those jobs are usually suffer from the scaling. Furthermore more cores are used in the simulation, a load unbalancing effects will be amplified and results in poor scalability. To Achieve better computational load balancing, a new automatic re-decomposition algorithm has been implemented recently. The new method can readjust the load balancing during simulation based on the current geometry. In this study, we will give some typical examples to show how to regain the load balancing and improve the parallel efficiency.

• LS-DYNA Simulations of the Impacts of a 38-Ton Heavy Goods Vehicle into a Road Cable Barrier

  K. Wilde, D. Bruski, S. Burzyński, J. Chróścielewski, Ł. Pachocki, W. Witkowski (Gdańsk University of Technology)

  Nowadays, more and more attention is being paid to safety on roads and motorways. It is due to the continuous development of road and motorway network and a significant increase of the number of vehicles on roads. To meet the expectations of improving road safety in Poland, the Road Innovations Development (RID) research programme was implemented in 2016. The aim of the RID 3A - Road Safety Equipment (RoSE) project is a comprehensive analysis of various road restraint systems and various types of road safety equipment installed on roads and bridges. The RID 3B - Effect of time and operating conditions of the durability and functionality of the elements of road safety (LifeRoSE) complementary project is aimed at developing innovative and comprehensive road management methodology for road safety equipment and traffic management measures. Part of the aforementioned projects is a thorough study of safety barriers based, among others, on full-scale crash tests and a number of numerical simulations using LS-DYNA. The aim of the paper is to assess the crashworthiness of a road cable barrier during an impact of a Heavy Goods Vehicle (HGV) weighing 38 tons. A numerical model of the safety device was developed and validated with a full-scale crash test. Based on this computational model, a series of virtual crash tests were carried out in which the HGV collides with the barrier under various impact conditions. Some of the cases will be compared with real accident outcome that took place on highway in Poland.

• LS-TaSC 4: Designing for the Combination of Impact, Statics and NVH

  K. Witowski (DYNAmore)

  The projected subgradient method is major new methodology development for the topology optimization of huge, multi-disciplinary structural problems; for example, the combined impact, statics, and NVH design of a whole body in white. This paper accordingly discusses the projected subgradient method in LS-TaSC 4, with specific reference to the basic theory, the ability to combined impact and NVH load cases, and the performance for huge models. Also mentioned is how the method has been enhanced to handle generalized constraints using the multi-tensor numerical scheme.

• Mainframe Computer Connector Wear Correlation and Prediction Analysis

  I. Karpov, I. Demiyanushko, B. Tavshavadze (Moscow Automobile and Road Construction State Technical University (MADI)

  Mainframe computers are expected to be highly reliable and available. To achieve this high level of reliability and availability, care must be taken from the initial development cycles to insure robust software and hardware. Here, the discussion will be focused on the structural aspect, namely the hardware assembly. A mainframe computer’s hardware structure consists of the rack, processor drawer, cooling assembly, input and output (I/O) assembly, power supply assembly, memory assembly and storage drawers. A typical mainframe computer with a single drawer installed is shown in Figure 1. The total height is 2.0 m where a total of 42 units (U) of many different types of mountable assemblies or drawers can be installed in the rack; 1U is 44.45 mm in vertical height. The height of the assemblies varies from 88 mm to 440 mm. The rack is an EIA (Electronic Industries Alliance) standard 19-inch-wide rack (482.6 mm), where the actual width of the mounting rails where the assemblies or server drawer is installed is 17 ¾” (450.85 mm). The total width of the rack is equal to 600 mm, which provides space to accommodate the cabling and vertical structure outside the width of the server drawer. The rack depth is 1070 mm. The drawer shown in Figure 1 is a 4U server drawer installed in the bottom of the rack, with a total drawer mass of 73 kg.

• MAT_291: A New Micromechanics-Inspired Model for Shape Memory Alloys

  J. Karlsson (DYNAmore Nordic) S. Kari, R. Dhume, S. Kashyap (Medtronic)

  This paper presents a new micromechanics-inspired constitutive model for shape memory alloys (SMAs) based on [1]. Shape memory alloys, e.g. Nitinol (Nickel-Titanium alloy), are widely utilized in the medical device industry because of their superelasticity. Superelastic properties of Nitinol enable its use in self-expanding stents and heart valve frames that can be inserted through a vein or artery using a thin delivery device and expanded at the target location. Motivated by the increased use of SMAs in the medical device industry, *MAT_291 (*MAT_SHAPE_MEMORY_ALLOY) is a first step towards more accurate and reliable material modeling. This material is currently available for solid elements and for explicit and implicit analysis. SMAs consist of two solid crystallographic phases, austenite (a high symmetry crystal structure, stable at high temperatures) and martensite (a low symmetry crystal structure that can be twinned or de-twinned, stable at low temperatures). Reversible transformation between the different phases gives rise to the shape-memory effect and superelasticity. The former implies that seemingly permanent deformation in the martensite phase can be recovered upon transformation to austenite by heating. The latter implies the material can undergo large strains in tension which can be recovered upon unloading. However, the superelastic stress-strain cycle will show elastic hysteresis similar to rubber-like materials, resulting from the transformation between twinned martensite, detwinned martensite, and austenite, see Figure 1.

• Material Parameter Identification with LS-OPT

  K. Witwowski (DYNAmore)

  In this workshop a short introduction to LS-OPT will be given, and the application of LS-OPT for calibration of material parameters will be presented. The new LS-OPT version 6.0 features for the usage of digital image correlation data for calibration of material parameters will be discussed by means of an application example.

• Measurement of Electromagnetic Launcher Muzzle Velocity with Induced Voltage of B-Dot Probe

  H.-K. Kim, M.-A. Woo, J. Kim (Pusan National University)

  Recently (early 2013), LS-DYNA has released EM module to solve transient electromagnetic-structural coupled problem. The ‘transient’ means that this software is able to consider shape, deformation and movement of objective model. Until now, there is few commercial software what supports electromagnetic-structural coupled transient problem despite of much necessity. Especially, to facilitate the coupled transient problem, LS-DYNA adopts boundary element method (BEM) what does not need air field mesh manually. By supporting this ability, eddy current, induced heating and resistive heating problems in transient can be successfully and easily solved. In this paper, by using LS-DYNA EM, conduct B-dot probe performance prediction as install positions and directions. Also, measrue muzzle velocity of an electromangetic laucher by the probe.

• Modeling and Validation of Static and Dynamic Seat Cushion Characteristics

  D. V. Dorugade (Concordia University), P.-E. Boileau (McGill University)

  Automotive seat cushions contribute considerably to static and dynamic comfort of the drivers. Design of a cushion is highly challenging due to its highly nonlinear viscoelastic behavior that is dependent on the seated body mass, and magnitude and rate of the vibration excitation. In this study, a dynamic seat cushion model is developed in the LS DYNA platform to determine its static and dynamic properties. The material model *MAT_FU_CHANG_FOAM_DAMAGE_DECAY (083_1) was used, which showed capability to predict nonlinear dynamic cushion behavior under different preloads, and excitation frequencies and amplitudes. This material model, available in the LS DYNA library, permitted evaluations of the nonlinear rate-dependent viscoelastic behavior of the cushion. The effectiveness of the model in predicting static and dynamic responses is demonstrated by comparing the simulation results with the laboratory-measured data in terms of force-deflection characteristics. The comparisons revealed reasonably good agreements between the simulation and measured responses. Contact pressure distribution on the seat cushion was further obtained, which also showed good qualitative agreement with the reported measured data.

• Modeling of Bolts using the GISSMO Model for Crash Analysis

  F. Schauwecker (Daimler/University of Stuttgart), M. Feucht, M. Beck, D. Moncayo (Daimler), F. Andrade (DYNAmore), Prof. P. Middendorf (University of Stuttgart)

  The prediction accuracy of bolted connections is becoming increasingly important in the automotive sector. The requirements and thus the vehicle architectures are changing due to the electrification of vehicles and the high weight of batteries as well as their low permissible intrusion depth. Bolts are required as detachable fasteners to connect batteries with the body in white. The energy absorption concepts of vehicles with internal combustion engines have been continuously developed over the past decades. Thanks to many years of experience, the bolt connection behavior and load transfer are well known. Energy absorption concepts for electrically powered vehicles are in a comparatively early development phase. For the evaluation and further development of new crash concepts, a reliable simulation method is a basic requirement to predict joint failure in bolted connections.

• Modeling of Microcellular Short Fiber Reinforced Plastics for Pedestrian Safety Analysis

  M. Landervik (DYNAmore Nordic), U. Westberg (Volvo Cars), S. Gastl (Borealis Polyolefine)

  For efficient vehicle development there is a strive to reduce prototypes and shorten development times which leads to the need to rely on CAE methods for continuous evaluation of product performance. This puts demands on the CAE methods, not only in terms of predictability but also in terms of how well they integrate in the development process. Model preparation, material characterization and computational costs are important aspects for successful integration. New materials and production methods are other drivers for CAE method development as current methods may not be adequate. Short fiber reinforced polymers (SFRP) have found their way into more automotive applications in recent years. Weight, the geometrical possibilities, part production cycle times and cost are some of the potential benefits. The injection molding process, however, leads to an inhomogeneous distribution of fiber orientation throughout a part. As the fiber orientation distribution has significant impact on the mechanical properties it causes anisotropy and spatial variations of the material response. This paper addresses the modeling of an SFRP part which is produced by gas assisted injection molding leading to a porous, microcellular, material consisting of three phases, i.e. matrix-, fiber- and pore phases.

• Modeling the Energy Absorption Characteristics of Wood Crash Elements

  E. F. Akbulut Irmak (Paderborn University)

  Wood is a natural and highly anisotropic material. Therefore, mechanical characteristics of the material depend on the direction and type of the load (e.g. deformation behavior of wood is ductile in compression and brittle in tension). The mechanical behavior of crash elements made of wood material was investigated experimentally and numerically at quasi-static and dynamic strain rates for load-carrying and energy absorption characteristics. For detailed investigations on the mechanical properties of wood, specimens were modeled and *MAT_WOOD (*MAT_143) was selected in LS-DYNA. The process of parameter identification for the *MAT_143 was clarified. In the scope of the experimental studies, quasi-static compression, tension and bending tests as well as dynamic drop tower tests were performed to characterize the material at low and medium strain rates, respectively. It was found that the investigated wood material is highly strain rate sensitive what can be captured by enhancing *MAT_143 by strain rate dependent fracture energy parameters. All material model parameters used in numerical studies were validated according to the experimental results for the *MAT_143. Since wood is a natural composite material, it was modeled with 2D shell element formulation and analyzed with single element simulations by composite material models by referring to material parameters used in *MAT_143. The investigated material models are *MAT_54, *MAT_58 and *MAT_261. The aim is to present a base study to enlighten the damage mechanism of wood for further investigations on the potential of wood-based structural automotive components.

• Modelling Back Face Deformation of Woven Layered Composite Targets under Oblique Impact

  M. Seidl, N. Faderl, M. Becker (ISL)

  Body armour is the only protection a dismounted soldier has against projectiles or fragments in case of combat. Perforation is prevented in body armour as the kinetic energy of the projectile is transformed to deformation work in the armour material. This dynamic material response upon impact is especially crucial for helmets, as it acts directly on the human head. One potential threat nowadays a foot soldier faces during missions is the 7.62x39 mm projectile fired from a rifle. Helmets are not designed to withstand a direct impact of such a projectile, which is launched at an initial velocity of vi=720+/10 m/s. Under an obliquity angle of θ>65 degrees (NATO) projectile ricocheting is observed. The aim of the ongoing project is to promote the projectile ricochet off helmets to increase the likelihood of projectile deflection and the survivability of the wearer. The focus of this paper is the target back-face deformation (BFD) upon oblique high velocity impact. Experiments were conducted on projectile impact on plane aramid plates. These plates have the same material properties, such as layer number, as used for manufactured helmets – other ballistic helmet materials are covered in future research. Upon impact, the dynamic BFD of the aramid targets was measured, using digital image correlation (DIC). Additionally, the experiments were repeated to capture the projectile trajectory through the target thickness, using X-ray cinematography. The BFD and trajectory results are used for the qualitative comparison of a numerical model, defined within the LS-DYNA® explicit Lagrangian solver. Model components, the projectile and target plate are defined using fully integrated hexahedral elements. The projectile deformation is represented by *MAT_JOHNSON_COOK and its failure criterion; and the target plate is represented by *MAT_COMPOSITE_DAMAGE. The projectile and the composite target are in a symmetric contact defined by *CONTACT_ERODING_SURFACE_TO_SURFACE. The aim of this paper is an investigation on the most suitable modelling approach for a numerical validation of the BFD response obtained from the DIC measurements. This work is a first step to implementing experimentally and numerically achieved BFD data in a LS-DYNA® Finite element (FE) head model, using a head injury criteria (HIC).

• Modelling of Bonded Component Tests, Comparing MAT_240 to State of the Art Models

  J. F. Berntsen, D. Morin, A. Holm Clausen, M. Langseth (NTNU)

  Modelling of adhesively bonded joints is still an active field of research, aiming for a more accurate description and simpler calibration processes without significant increase in computational costs. There are two different approaches typically applied to model adhesives depending on the size of the problem and required accuracy. For smaller problems where the computational cost is of less relevance, the adhesive line can be finely discretized and modelled with a mesoscopic material model. This mesoscopic model is characterized by a constitutive law describing the relation between stresses and strains in the material.

• Modelling of Polypropylene Subjected to Impact Loading at Low Temperatures

  E. Schwenke (NTNU)

  The use of thermoplastics in structural applications requires that engineers can reliably predict their mechanical behaviour. Depending on the intended use, a component must withstand various load cases and environmental factors. This paper seeks to investigate the capabilities of a phenomenological material model to represent polypropylene (PP) plates subjected to a dropped weight impact at low temperatures. The dropped weight tests were performed with an Instron CEAST 9350 Drop Tower Impact System, shown in Figure 1. An incorporated environmental chamber injected with liquid nitrogen enabled sub-room temperature conditions. A total of 11 drop tests were made at five different impact velocities. The material was found to experience moderate plastic deformations until failure through plugging. By comparison of force displacement curves, the tests are found to show good repeatability. Some variations are found with respect to initiation of failure, possibly caused by small variations between the plates or misalignments during tests.

• Modelling of the Overcasting Reinforcement Process using the LS-DYNA ICFD Solver

  J. Burt, O. Tomlin (GRM Consulting), D. Howson, T. Fleet (Alvant)

  The overcasting reinforcement process is a complex casting technique for creating lightweight aluminum components with additional strength from an aluminum matrix composite (AMC) insert. Empirical work to date has shown there are opportunities to further enhance the quality of adhesion between this AMC insert and cast aluminum. It is also evident that developing a predictive tool of bond quality will reduce the need for invasive measuring techniques.

• Modelling of Thermo-Viscoplastic Material Behavior Coupled with Nonlocal Ductile Damage

  M. Nahrmann, Prof. A. Matzenmiller (University of Kassel)

  The postcritical behaviour due to mechanical loading of the high strength steel HX340LAD (ZStE340), typically used for cold forming of complex structures is modelled by means of a yield curve in the softening part of the material. Due to local heating, caused by viscoplastic deformations particularly for high strain rates, a thermo-mechanical coupled simulation is carried out by taking into account the conversion of plastic work into heat. Moreover, a temperature and rate dependent material model, coupled with ductile damage, is applied to allow the prediction of damage and failure of metal components caused by large plastic deformations during forging or sheet metal forming. The constitutive equations are implemented as a user defined material model into LS-DYNA and include the temperature dependency of the material parameters such as for the YOUNG's modulus, the initial yield stress, the nonlinear isotropic hardening parameter, the strain rate sensitivity as well as for the moduli of a continuum damage mechanics based approach. The nonlocal damage option *MAT_NONLOCAL in LS-DYNA is used to prevent localisation of the damaged zone for small elements. Test data of tensile specimens are considered under different strain rates from 0.006 1/s (quasistatic) up to 100 1/s for identifying the model parameters with the optimisation software LS-OPT. Finally, the numerically predicted stress-strain curves are compared to the according test data for the model verification. In addition, the computed heat evolution due to plastic flow is compared to the experimental measured data in terms of time-temperature courses. Finally, the plastic necking of the tensile specimen is investigated by means of the spatial strain distribution.

• Multi Material Modeling with ANSA: An Application in the Automated Assembly Process in FORD

  T. Fokylidis, V. Karatsis (BETA CAE Systems), U. Tunc, H. Wuestner (Ford-Werke), N. Pasligh (Ford Forschungszentrum Aachen), C. Ping, M. Ng (Ford Australia)

  The simulations of virtual models hold a key role during the design process of a vehicle. The numerus different components in a CAE model make its assembly one of the most demanding tasks during the model buildup. Over the last years, the effort to achieve higher accuracy in crash test simulations has resulted in more detailed models. As a result, the FE representations used to connect the different parts vary a lot and get complex sometimes. To support effectively such time-consuming and error-prone modeling processes, the available tools should offer increased automation and standardization levels. A commonly used method is to simulate the area of these connections by using different material properties representing effectively not only the material of the connecting flanges but also the heat affected zones in each flange. Ford-Werke GmbH in cooperation with BETA CAE Systems has come up with a fully automated process within ANSA pre-processor that reads the CAE and its connection file, assigning the proper connectivity to each connection. Additionally, with the use of external files assigns the needed materials in the area of each spotweld using the respective LS-DYNA keywords. Finally reports to the user the results of the assembly procedure and the final status of each connection. The current paper explains the basic terms of the automated process mentioned above. Moreover, it presents the techniques used within ANSA to assembly a full analysis model in a fast and robust way combining different FE-representations and multi material assignment in the area of a connection.

• Multi Objective Optimization Approach for Biomedical Stent using Parametric Optimization

  M. Seulin (DynaS+), P. Balu (DEP)

  Stent deployment process and its long-term usage requires to meet multiple objectives like final stent diameters for cardiovascular disease treatments, and minimalistic plastic strain during the deployment to meet the fatigue life. Achieving an exact dilation diameter and maintaining minimal plastic strain values are mainly based on stent geometric design, cross section, material, amount of crimping and expansion diameter. This paper presents an effective stent finite element (FE) modelling and parametric optimization method using DEP MeshWorks stent rolling and parametric tools, LS-DYNA and LS-OPT optimization tools. Controllable design and deployment process parameters are considered for optimum random sampling using a Design of Experiments (DOE) approach, and using a parametric tool, designs are generated, on which analysis and optimization is performed using LS-DYNA explicit solver. The result is an optimum design solution which meets the required diameter criteria, without exceeding the minimal plastic strain limit, and within the foreshortening and flexibility limits.

• New developments in material testing at very high strain rates

  R. Grams (University of Siegen)

  The determination of material properties under high-speed loading has been a challenge for many years. Structural vibrations, also called system ringing, in conventional testing machines deteriorate the quality of force measurement, which makes a precise determination of stress-strain curves and corresponding mechanical properties impossible. In this work, a new specimen geometry with its basic mechanical principle and the corresponding measurement technique are presented and discussed. The new method allows the determination of true stress-strain curves at high strain rates free from oscillation. Due to the additionally minor plastic deformation area in the new Generation III specimen, a quasi-movable bearing condition for the specimen fixation was created. Forces, based on the natural frequency of the specimen, deform the cross-section and create a displacement, which keeps the kinetic energy of the measurement area high. In this way, the elastic ringing effect has been reduced significantly. Any kind of filtering, smoothing or similar manipulations of the result are no longer needed. This new method has been validated on three steels types and one type of aluminium alloy with different strain hardening behavior through measurements and numerical analysis. The Generation III specimen can also be used for the quasi-static test and cover the strain rate range from 4.4·10-4 - 103 /s accordingly.

• New Features in LS-DYNA Part I

  J. Wang (LSTC)

• New Features in LS-DYNA Part II

  T. Erhart (DYNAmore), T. Borrvall (DYNAmore Nordic)

• New Methods for Compression Molding Simulation and Component Strength Validation for Long Carbon Fiber Reinforced Thermoplastics

  S. Hayashi (JSOL), C.T. Wu, W. Hu, Y. Wu, X. Pan, H. Chen (LSTC)

  Composite materials like fiber reinforced plastics (FRP) are becoming more widely used in the automotive industry and have been found very effective in reducing vehicle weight. Recently, long carbon fiber reinforced thermoplastics are increasingly being used for lightweight structural parts with high stiffness, strength and energy absorption performance. Compression molding is considered one of the most efficient manufacturing processes to mass produce FRP parts for automotive applications. Compression molding can form FRP into complex shapes with relatively low manufacturing cost and short process time. However, this often generates unwanted fiber orientation, uneven distribution of fibers and fillers, weld lines and matrix rich regions. These forming effects strongly affect mechanical strength. To analyze these complex phenomena, LSTC and JSOL developed new compression molding simulation techniques for long fiber reinforced plastics using a beam-in-adaptive EFG coupling function in LS-DYNAⓇ. In this paper, a compression molding simulation for long carbon fiber reinforced thermoplastics is introduced and new component strength analysis method with a beam-in-SPG coupling model using deformed beams calculated in the compression molding simulation is presented.

• New Options in Frequency Domain Analysis and Fatigue Analysis with LS-DYNA

  Y. Huang (LSTC)

  A series of frequency domain analysis and fatigue analysis features have been implemented to LS-DYNA, since version 971 R6 [1]. The frequency domain features include FRF (Frequency Response Function), SSD (Steady State Dynamics), random vibration, response spectrum analysis, and acoustic analysis based on BEM (Boundary Element Method) and FEM (Finite Element Method). The fatigue analysis features include fatigue damage solvers in both time domain and frequency domain (based on random vibration and steady state vibration). The main applications of these features are in NVH and durability analysis of structures and components [2]. A bunch of new options were implemented to the frequency domain analysis and fatigue analysis features since the last European LS-DYNA Conference in Salzburg, Germany, 2017.

• New Testing in Support of LS-DYNA MAT 224 Material Model

  A. Gilat, J. Seidt, N. Spulak, J. Smith (Ohio State University)

  LS-DYNA MAT224 is a tabulated plasticity and failure model. The plasticity part of the model can include strain rate, strain hardening and temperature effects, and the failure part is based on a failure surface of the equivalent plastic strain to failure as a function of triaxiality and the Lode parameter. The present paper presents two new experiments that have been developed recently in order to support the model. The first experiment adds new points to the failure surface in a region that is important in simulations of projectile impact and penetration. The second experiment is used for determining the Taylor-Quinney coefficient (β), which controls the magnitude of the temperature increase due to plastic deformation. Simulations of impact and penetration events show that failure occurs under a stress state of biaxial tension and out-of-plane compression. This state of stress on the failure surface is not in the region that is populated with data points obtained from typical experiments (tensile tests of flat and round, parallel and notched specimens, tensile tests of wide parallel and notched specimens, pure shear tests, combined tension-compression/shear tests, and compression tests.) In order to obtain an independent measurement of the equivalent strain to failure under a state of stress of biaxial in-plane tension and out-of-plane compression a new experiment was developed. In this experiment a small diameter punch penetrates a thin specimen plate that is backed by another plate. The deformation of the back surface of the plate is measured with DIC. The value of the equivalent strain to failure is determined from measuring the force and matching the LS-DYNA simulation with the measured deformation and force.

• Numerical and Experimental Investigation of SPH, SPG and FEM for High Velocity Impact Applications

  M. Becker, M. Seidl (ISL), M. Mehl (University of Stuttgart), M. Souli (University of Lille)

  During a high-velocity impact event large pressure, strain rate, and deformation occur. This is a very demanding scenario for mesh-based approaches like the FEM (Finite Element Method). In particular, for the description of fracture, special techniques like erosion or node splitting are required. For a comprehensive validation, we have designed a projectile surrogate and conducted impact experiments at different oblique angles in our laboratories. These experiments are observed with X-ray cinematography and physical properties for validation are extracted from the images. For the highly dynamic behavior during the impact, an alternative to mesh-based approaches are particle-based methods. LS-DYNA® offers two pure particle methods, SPH (Smooth Particle Hydrodynamics) and SPG (Smooth Particle Galerkin). This study compares SPH to the FEM results and the experimental data. Since the discretization requirements for the numerical approaches are different, it is not possible to compare exactly the same discretization. Instead, the number of nodes is chosen similarly. The accuracy is investigated qualitatively, using X-ray images, as well as quantitatively, using the extracted properties from the experiments.

• Numerical Investigation of Parameters Affecting Crush Mode of Triggered FRP Tube

  R. Akita (Itochu Techno-Solutions Corporation), A. Koike (Isuzu Advanced Engineering Center), A. Yokoyama (Kyoto Institute of Technology)

  When a quasi-static axial compressive load is applied to a Fiber Reinforced Plastics (FRP) tube, a continuous and stable fracture phenomenon called “Progressive Crushing” which shows highly effective energy absorption appears. The authors have constructed a cohesive element FEM model that can reproduce the process to this phenomenon. The purpose of this paper is to investigate the most stable chamfer shape for progressive crushing of the FRP tube, by using Cohesive Zone modeling technique. In the study, cross-sectional shapes of triangle type, chevron type and M-type were selected for the simulation of axial crushing test to confirm crush mode. Five geometric shapes of flat plate FEM model were considered to conducting a fundamental investigation. Furthermore, the 3D finite-element models of FRP tube using reasonably cross-sectional shapes were intended to obtain a well-balanced chamfer shape, therefore, providing useful suggestions for FRP tube design and/or manufacture.

• Numerical Methods for the Analysis of Behind Armor Ballistic Trauma

  P. Zochowski (Military Institute of Armament Technology)

  The asymmetric character of current military conflicts causes that soldiers are often exposed to projectile impacts. Body armor (helmets, vests, etc.) protects them from the negative effects of highly dynamic loads by absorbing and dissipating kinetic energy of a projectile. However, severe local and distant injuries can occur in the human body, even in case of a non-perforating impact. A large amount of energy and momentum is converted into deep back face deformation (BFD) of the armor and dynamic acceleration of the body walls. In case of high-velocity impacts a trauma may be caused also by the stress waves generated and propagated through the tissues. Injury of the human body as a result of non-perforating projectile impact into the armor is defined as Behind Armor Blunt Trauma (BABT) [1].

• Numerical Modeling of Honeycomb Structure Subjected to Blast Loading

  M. Stanczak, T. Fras, L. Blanc (ISL), P. Pawlowski (Polish Academy of Sciences, Warsaw/ISL), A. Rusinek (Lorraine University)

  The main objective of this study is related to the modeling of an aluminum thin-walled honeycomb structure under blast loading. The blast test is performed by means of an explosively driven shock tube (EDST). A planar shock wave is generated by a small amount of an explosive charge detonated in front of the tube. The honeycomb core is compressed by a movement of the steel plate located at the end of the tube. In the experiment, the honeycomb deformation is recorded by a high-speed camera and the absorbed loading by the structure is measured by a force sensor fixed on the rear sample face. The simulation of the material behavior is carried out using the Lagrangian approach implemented in LS-DYNA, ver. R9.0.1. The shock pressure generated by the explosion is recalculated to define the force applied to the plate being in contact (*AUTOMATIC_SURFACE_TO_SURFACE with friction) with the honeycomb and causing its deformation. The honeycomb is meshed by shell elements with a default formulation ELFORM: BELYTSCHKO-TSAY. The front plate is assumed as a rigid body to induce a uniform deformation of the honeycomb structure modeled using *MAT_SIMPLIFIED_JOHNSON_COOK 098 with parameters published in, [1-2]. The simulations are performed for different number of unit cells to define the honeycomb, from a single cell to fifty-three cells, aiming to indicate a minimal cell number required to model properly the entire structure. A dependence of numerical results on the mesh size, unit cell dimensions, friction conditions and the strain rate has been verified. The comparison between values of the load absorbed by the sample crushed numerically and experimentally shows a good agreement providing an insight into mechanisms of blast wave absorption by honeycomb structures. Such an analysis may be further applicable in development of advanced cellular structures applied to dissipate blast energy.

• Numerical Simulation of Electrohydraulic Forming using Coupling of ALE and Lagrangian Elements

  M. Woo, J. Kim (Pusan National University)

  Electrohydraulic forming is a high-speed forming process that employs high-pressure shock wave in fluid. When the electric energy is discharged from a capacitor bank, it is transferred to the water through the electrode bar and it makes the fluid into a high-pressure plasma state. Due to the high-pressure water, the sheet can be deformed into the die shape. Because the numerical model of electrohydraulic forming deals with fluid and structural models at the same time, it needs coupling mechanism for parts. Therefore, in this study, numerical model for electrohydraulic forming was developed using the coupling of ALE (Arbitrary Lagrange-Eulerian) and lagrangian mesh. The fluid parts, plasma, vacuum and water, were modelled with ALE elements and structural parts, die, chamber and sheet metal were modelled with general lagrangian mesh. The results of the numerical simulation showed that the plasma and water parts expanded due to the input energy, and the sheet metal was deformed with a speed above 100 m/s due to the pressure wave of the fluid parts.

• Numerical Simulations in Vehicle Restraint System Development

  M. Šebík, M. Popovič (SVS FEM), M. Drdlová (Research Institute for Building Materials)

  Since 2016 there has been a research project going on which is focused on development of new design of portable road barriers with integrated anti-noise walls. The key feature of the new barrier design is a material selection for anti-noise panels. New panels made of wood and cement-bonded wood-chip material called Velox significantly improve noise absorption properties of the barrier. However, the question is: what are their qualities from mechanical point of view? And will such barrier be able to withstand crash tests required by the highest containment level, H4b according to EN1317 standard? Numerical simulations are being utilized in this research at all levels in order to reduce costs and to predict how particular design modifications influence restraint capabilities of the barrier. As a starting point there were crash test simulations with original barrier design performed and after achieving sufficient correlation between the simulations and the real crash tests, modified systems were designed and tested. Firstly, there were the new panels. From mechanical point of view, Velox is very complex material so an extensive investigation of its mechanical properties had to be performed. This investigation covered small scale tests (quasistatic and dynamic) and large scale dynamic tests as well. Based on the experiments there was an appropriate material model chosen and its parameters determined to faithfully describe behavior of the material. Since crash test simulations with the first Velox wall design identified several weaknesses, certain preventive measures had to be introduced. Besides design changes of the bottom part of the barrier, several kinds of Velox boards back face treatment were proposed in order to enhance resistance and keep overall integrity of the structure after crash load exposure. All these design changes are now being analyzed and further developed based on crash test simulations but also with regard to production processes and mobility of the barrier.

• Numerical Simulations of Vacuum Packed Particles using LS-DYNA

  P. Bartkowski, R. Zalewski (Warsaw University of Technology)

• On the Setup and Simulation of Large Scale LEGO Models Build with LS-DYNA and LoCo

  T. Gerlinger, D. Koch, A. Haufe (DYNAmore), N. Karajan (DYNAmore Ohio), M. Thiele, A. Sahurnean (SCALE)

  Playing with LEGO® bricks is something many engineers might have enjoyed during their childhood. Building any kind of mechanical construction allows creativity and complexity to an extent which probably contributed to their fascination and finally to their decision of becoming engineers. It’s interesting to see how many of them are still fascinated by LEGO® even in their adult life. Especially for children, or for those with an active inner child, crashing these models into each other is even more fun, because seeing all those bricks fly all over the place is just fascinating, beyond any scientific or professional aspect.

• Parachute Deployment Simulations using LS-DYNA ICFD Solver and Strong FSI Coupling

  M. Le Garrec, A. Poncet, V. Lapoujade (DynaS+)

  The main goal of military airdrops is the accurate delivery of cargo released from a moving air vehicle via parachute. The airdrop trajectory results from the movement of the dropped package and the dynamics of the parachutes deployment (Fig.1:). After having treated the freefall of a rigid object in the near flow of an airplane ([8]), the present paper focuses on the parachute deployment modelling and its challenges in LS-DYNA.

• Polypropylene Composites under Impact: Anisotropy, Mapping and Failure Criteria in Simulations, and Validation on a Part for Building and Construction Industry

  M. Nutini, M. Vitali (Basell Poliolefine Italia, a LyondellBasell Company), M. Benanti, S. Formolo (Polytech)

  Part and component design with Polypropylene Compounds can create several challenges for simulation methods. When Short Glass Fibers Polypropylene (SGF-PP) is considered, fiber orientation prediction, process-induced anisotropy and rupture criteria must be properly addressed in the structural analyses. The time frame is also relevant, as industrial environment simulations often need to provide fast solutions to designers in order to limit the time to market. Responding to the needs of a simulation tool for an early stage design, this paper describes a methodology based on an orthotropic material law (Ls-dyna MAT_157), embedded interactive criteria and a mapping tool (LS-DYNA ENVYO). This approach has been applied in the design of a part used in the building and construction industry, for which an experimental validation on an impact test has been also carried out. This study is here reported.

• Postprocessing of the 2020 EU-NCAP Frontal Impact Test in META

  N. Tzolas, D. Siskos (BETA CAE Systems)

  New cars are continuously becoming safer thanks to improvements in crash test regulations and standards. Currently crash test regulations and standards assess the safety performance of vehicles in frontal impacts under the precondition that the vehicle’s supporting structure is hit in such a way that the crumple zone absorbs energy during the crash. The General German Automobile Club (ADAC) accident research data shows, however, that in a car-to-car impact, the vehicle’s supporting structures might not hit in the same way as in the standard frontal impact tests. In these cases, the crumble zone of the vehicle cannot be fully utilized and this can lead to severe injuries. In 2010, the ADAC introduced a new test to assess the compatibility of vehicles in a car-to-car impact. In this test, a special honeycomb-shaped barrier is used, and its surface is scanned for evaluation after the test. This test with a progressive deformable barrier was named ADAC compatibility test or MPDB test.

• Prediction of Load-Bearing Capacity of Composite Cylinders with Impact Damage

  A. Cherniaev (University of Windsor), V. Komarov, S. Pavlova, A. Pavlov (Samara University)

  Impact damage induced by hailstone impact, tool, or equipment dropping can lead to severe reductions in composite structures’ load-carrying capacity. Aerospace companies and manufacturers of other products, in which composite materials are extensively used, spend considerable resources to determine the level of degradation of composite parts’ load-bearing capacity that have received impact damage during operation or during assembly, as well as the permissible degree of damage at which the replacement of an expensive structural member is unnecessary. Usually, such assessments are based on the integrated application of experimental destructive and non-destructive methods, which, in turn, also requires considerable financial and time investments. Understandably, the availability of a verified simulation approach capable of predicting the residual load-carrying capacity of composite parts with impact damage would provide significant costs savings and accelerate the decision making when such assessments are required. This preliminary study represents the first steps aimed at developing such a simulation approach using LS-DYNA software and is focused on the load-bearing capacity of damaged composite structural members designed to work primarily under the action of compressive loads.

• Prediction of Spot Weld Failure for Automotive Steels

  J. Lim, J. Ha (Posco)

  Spot weld failure has a great influence on the crashworthiness of a vehicle since an automotive body is mostly assembled by spot welding. Spot weld failure was not a serious problem when using low strength steel, but as the strength of steels increases, spot weld failure became a hot issue for crash performance due to the low spot weld strength compared to material strength. Nowadays, the car design is based on CAE, and the crashworthiness is evaluated from crash simulation. Spot weld failure is a critical factor causing the discrepancy between the actual crash performance and simulation result. Of course, car designers want to get accurate simulation results and design to avoid spot weld failure based on simulation. There are a lot of studies on spot welding failure, but It is necessary to further enhance the accuracy. In this paper, we study how to predict accurate spot weld failure by macroscopic analysis of spot weld failure. Normal, shear, bending, and torsional load components act on spot welds, and many spot weld failure model consider that they act independently, destroying the spot weld. In this paper, normal and bending load components are considered together because loading direction and plane of normal and bending components are same. Spot weld failure model that normal and shear load components act independently and there is the interaction of normal and bending components, is newly proposed. Here, torsional component is ignored because of low influence on an automotive body. Spot weld failure tests are performed for various automotive steels, and coefficients of spot weld failure models are derived. Since an automotive body has mostly heterogeneous stack-ups of the strength and the thickness, the spot welding failure tests for heterogeneous stack-ups are also performed and it is verified that the new model describes dissimilar stack-ups well. Compared to conventional models, the new model has an advantage in the simplicity and the accuracy. Finally, the predicting method of coefficients of spot weld failure models is developed to consider spot weld failure in the crash simulation without experiments.

• Random Vibration Analysis for a Gunner Platform Frame using Experimental Data

  S. E. Yılmaz (FNSS Savunma Sistemleri)

  Remote controlled weapon systems have gained great importance in defense industry as they maximize crew safety with accurate shooting capabilities. On the other hand, vibration levels are of great consideration because of its effect on crew comfort and system reliability especially for tracked armored vehicles. In this study, vibrational evaluation is performed for a remote control gunner platform frame, which is mounted to the top plate of an armored tracked vehicle. Vibrational response of the gunner platform is critical for a successful completion of especially mobile missions. In order to perform random vibration fatigue evaluation, the experimental data obtained from the top plate of an armored tracked vehicle is used and random vibration analysis are performed using LS-DYNA®. Power Spectral Density (PSD) profiles provided in NATO AECTP 400 document are also included in the random vibration analysis with a degree of modification in order to make a comparison. Finally, random vibration analysis results from LS-DYNA® are compared with the results of another commercial software using similar analysis parameters.

• Recent and Future Developments for the ICFD Solver in LS-DYNA

  F. Del Pin, I. Caldichoury, R. R. Paz, C. Huang (LSTC)

  Since its release in R7 the Incompressible CFD solver (ICFD) has been rapidly improving and increasing its functionality. In this paper a summary of the latest and current developments will be presented. The focus will be on four topics. First the steady state solver and its coupling capabilities for fluid-structure interaction (FSI) or conjugate heat transfer (CHT) will be presented. In second place the recent modifications to the boundary layer mesh generation will be introduced where some default parameters have changed. The possible implications of these changes in the solution will be mentioned. Third a short introduction to coupling ICFD with LS-OPT for shape optimization will be presented. The idea is to use ANSA to morph the surface mesh driven by LS-OPT to provide an optimal solution. Finally some of the current developments will be enumerated like immersed interfaces, periodic boundary conditions, porous media through shell elements for parachute simulation, etc. These developments will be part of future LS-Dyna releases.

• Recent LS-DYNA Developments in the Structural Conjugate Heat Transfer Solver

  T. Klöppel (DYNAmore)

  Increasing demands for the simulation of complex, multi-physics problems in crashworthiness and manufacturing process analyses have necessitated new developments in the structural conjugate heat transfer solver in LS-DYNA®. Some of the most recent extensions and new implementations are presented and discussed in this contribution. The first block addresses the relatively new field of battery abuse simulations. Focus is put on a novel thermal composite thick shell element that is defined using *PART_COMPOSITE_TSHELL. On the one hand, the implementation allows for a relatively easy input definition. On the other hand, the formulation adds new temperature degrees of freedom for each layer of the composite structure and, thus, accurately resolves the internal lay-up of the structure, i.e. the battery cell. The reconstructed lay-up is also accounted for in the thermal contact routines. Consequently, the heat transfer through a stack of solid elements can be reproduced exactly by a single composite thick shell element with the corresponding lay-up definition. The second block presents the work on different thermal boundary conditions. A recent enhancement enables the “standard” boundary conditions (convection, radiation, and flux) to be transferred to newly exposed surfaces after element erosion. In general, this is sufficient for modeling laser cutting with a flux boundary condition, but the input of such a model can become very complex. Therefore, a new thermal boundary condition *BOUNDARY_FLUX_TRAJECTORY is introduced in the second part of this block, which is tailored for moving heat sources acting on the surface of a structure. In contrast to the standard flux boundary condition, the new implementation also accounts for the tilting of the heat source. The boundary condition is applicable in coupled thermal-structural and thermal-only simulations. The second block is completed by the presentation of a new temperature boundary condition *BOUNDARY_TEMPERATURE_RSW that is devised as a simplified modeling strategy for resistive spot welds (RSW). With the keyword, the temperature distribution in a weld nugget is defined directly.

• Roof-Crush Analysis of the Volvo XC40 using the Implicit Solver in LS-DYNA

  A. Jonsson (DYNAmore Nordic), M. Carlberg (ÅF/Volvo Cars (Consultant), T. Eriksson (Volvo Cars)

  During the development process of a new platform or car model, each design iterate is subjected to a large number of load cases, both dynamic as well as static. At Volvo Car Corporation, this process is almost entirely carried out using virtual testing by finite element analysis. The amount of physical prototypes is reduced to a minimum, and in many cases physical testing is limited to the component or sub-assembly level. Still, the final design must pass a number of physical tests and legal requirements, where roof crush is an important test of the structural integrity of the cab. The purpose of the FMVSS roof crush test is to “reduce deaths and injuries due to the crushing of the roof into the passenger compartment in rollover accidents” [6]. At Volvo Car Corporation, occupant safety is a fundamental element in all development projects since the start of the company, and the Volvo XC40 received a 5-star rating when tested by Euro NCAP [7]. The roof crush resistance is important with relation to safety in case of a roll-over accident, since the structural integrity of the car body makes the final line of defense, but many safety systems will interact in this case, from driver assist systems to electronic stability systems and restraint systems. The roof crush test will induce high stresses in many structural parts of the car body, for example the A-, B- and C-pillars, window frame and roof. This means that the analysis must be carried out meticulously, since the roof strength requirement may set design limits for many structural parts. Also new design concepts, such as composite roof panels or panorama glass roofs, imply new challenges for the roof crush analysis. The testing procedure according to FMVSS 216 [6] is specified as quasi-static (the time to complete the test is minimum 10, maximum 120 seconds), but has traditionally been run in explicit LS-DYNA in only a fraction of this time. From this viewpoint the roof-crush load case would be a typical application of implicit analysis, allowing the simulation of the test to get closer to the real test procedure. As a part of the ongoing method development work, it was decided to evaluate also the implicit technique, using the Volvo XC40 as a benchmark case. A previous study [5] indicated that it is possible to re-use FE-models originally created for crash load cases also for quasi-static load cases using the implicit solver in LS-DYNA with a reasonable modification effort. A previous study on implicit roof-crush analyses in LS-DYNA [1] indicated good correlation to explicit analyses, as well as reasonable performance with respect to solution time. Also, the publicly available examples [2][3] of implicit roof-crush analyses served as great inspiration in the present work.

• Running Jet Engine Models on Thousands of Processors with LS-DYNA Implicit

  R. Lucas, C. Ashcraft, R. Grimes, F.-H. Rouet (LSTC), J. Dawson, T.-T. Zhu (Cray), E. Guleryuz, S. Koric (NCSA), J. Ong, T. Simons (Rolls-Royce)

  Only time and resource constraints limit the size and complexity of the implicit analyses that LS-DYNA users would like to perform. Rolls-Royce is an example thereof, challenging its suppliers of computers and mechanical computer aided engineering (MCAE) software to run ever larger models, with more physics, in shorter periods of time. This will allow CAE to have a greater impact on the design cycle for new engines, and is a step towards the long-term vision of digital twins. Towards this end, Rolls-Royce created a family of representative engine models, with as many as 66 million finite elements. Figure 1 depicts a cross-section of the representative engine model.

• Setting up a Hot Stamping Simulation considering Tool Heating with OpenForm

  K. Kassem (GNS)

  The steadily growing requirements regarding the carbon footprint of vehicles has motivated the deployment of quenching (hot stamping) as a promisingly manufacturing process for lightweight car bodies in the series production of structural components. Very high part stiffnesses as well as formabilities can be achieved by means of this quenching process with significantly less forming energy and material consumption. This sets new standards both in vehicle safety and vehicle crash performance as well in sustainable and resource-saving mass production of car body components.

• Shell Models with Enhanced Kinematics for Finite Elements in Sheet Metal Forming Simulations

  T. Willmann, M. Bischoff (University of Stuttgart)

  Beyond the shell model of Reissner and Mindlin, which is available in LS-DYNA® for example in shell ELFORM=2/16, there have been many developments in the field of 3d-shell models in recent years [1]. 3d-shell models can be beneficial in sheet metal forming simulations because they allow for three-dimensional stress states. 3d-shell elements are available in LS-DYNA®, e.g. ELFORM=25. In the doctoral dissertation of Fleischer[2] it has been found that under certain conditions this element formulation suffers from an artificial stiffening effect. Although this finding dates back to 2009, this phenomenon has remained unexplained so far. In this contribution, the authors explain the reason for this stiffening effect and show a possibility to remove it. Moreover, an outlook on the development of higher order shell models for sheet metal forming simulation is given.

• Simulation of Concurrent Detonation of Multiple High Explosive Charges

  L. Schwer (Schwer Engineering & Consulting Services), S. Stojko, H. Bornstein (Defence Science and Technology Group)

  A 1D spherical LS-DYNA Multi-Material Arbitrary Lagrange Eulerian (MM-ALE) model was constructed to simulate the three single charge events reported in MABS 25 manuscript P-029 Stojko, et al. (2018). These three simulations were repeated using 2D axisymmetric meshes. Multiple charge simulations were made using 2D axisymmetric and 3D models of the double and triple charge experiments. As stated by Stojko et al. “The primary purpose of the experiments was to provide a database of results for the validation of numerical modeling of the effects from multiple high explosive charges.” The model results presented in this manuscript support this statement of the data representing a valuable validation database for both single and multiple charge explosions.

• Simulation of Process Dependend Properties with MAT_254 Demonstrated for the ‚Bake-Hardening‘ of an 6xxx Aluminum Alloy

  M. Merten, T. Klöppel (DYNAmore), S. Jurendic, Z. Liang (Novelis)

  Taking into account the strain and thickness distributions of cold formed parts is well established in LS-DYNA. Additionally, *MAT_TAILORED_PROPERTIES offers the possibility to use a tabulated set of flow curves dependent on a history variable. The physical quantity represented by the chosen history variable can be defined by the user. Getting the distribution of this history variable may be a difficult task. For press-hardening simulation exclusively, LS-DYNA offers *MAT_244/248 to calculate the distribution of mechanical properties based on the distribution of metallurgical phases. The phase distribution is a result of the thermo-mechanically coupled simulation of the production process. To overcome the limitations of these two material models, *MAT_GENERALIZED_PHASECHANGE was implemented. This material has been used successfully for the simulation of press-hardening, welding and 3D-Printing. The current work presents a new field of application for *MAT_GENERALIZED_PHASECHANGE, simulating the “bake-hardening”-effect of specific aluminium alloys. The local final strength of hardenable aluminum alloys for automotive applications depends on the local pre-strain from the forming process and the local time-temperature-profile during paint bake. An initial approach to model this behavior is given. Implemented extensions to *MAT_GENERALIZED_PHASECHANGE, which enable are more precise description of the underlining mechanisms, will be shown.

• Simulation of Self-Piercing Riveting Process and Joint Failure with Focus on Material Damage and Failure Modelling

  A. Rusia (Daimler/University of Stuttgart), M. Beck (Daimler), Prof. S. Weihe (University of Stuttgart)

  Weight reduction is one of the main objectives that has played a pivotal role in designing Automobiles in the past decades. Various methods can be employed in this direction such as replacing traditional steel with lightweight aluminum alloys or using a combination of multiple lightweight materials. Joining techniques like spot welding, which generally perform well for joining of steel body panels, do not yield satisfactory results in joining of aluminum sheets. Consequently, there has been an increasing interest in developing alternative joining techniques as a replacement for spot welding in the automotive industry.

• Simulation of Sheet Metal Forming using Elastic Dies

  M. Schill (DYNAmore Nordic), J. Pilthammar, M. Sigvant (Volvo Cars), V. Sjöblom, M. Lind (Blekinge Institute of Technology)

  Simulation of sheet metal forming is one of the major applications of LS-DYNA. Today, a majority of the forming industry is using Finite Element models to design the stamping dies in order to prevent excessive thinning, wrinkling and producing parts within tolerance by compensating for springback deformation. All these simulations are made using the assumption of rigid forming surfaces. Depending on the type of press, tool design and sheet metal part, this assumption could prove to be incorrect which yields a forming result that depends on the elastic deformation of the stamping die and in some cases the entire stamping press. Such deformations are usually compensated during die try-out by manual rework which is costly and time consuming.

• Simulation of the Temperature Distribution in Ship Structures for the Determination of Temperature- Dependent Material Properties

  J. M. Kubiczek, H. Herrnring, L. Kellner, S. Ehlers (TUHH), R. Diewald (TÜV NORD EnSys)

  Several Arctic waters are no longer ice-covered throughout the year. As a result, the Northern Sea Routes are getting into the focus of the maritime industry [1]. In addition less ice coverage in other sea areas such as the Baltic Sea leads to increased shipping traffic in the winter season. This repeatedly leads to damages to ships when sailing in ice-covered waters, but also when colliding with ice floes and icebergs but also with ships, such as icebreakers, in convoys [2, 3]. It is of great importance for the structural simulation of these events to model the material properties of the ship structure under consideration of the environmental conditions. These material properties such as yield strength and tensile strength as well as fracture strain, however, are strongly influenced by the material temperature [4]. Therefore the question arises how cold a ship structure can actually become in winter and in arctic waters and how this affects the structural response in the event of a collision. In the rules and guidelines of the classification societies -60 °C can be found as the lowest temperature for material tests on steels used in shipbuilding [5]. This value corresponds well with different temperature measurements where extreme values below -50 °C were measured in the area of the Northern Sea Route [6, 7]. In contrast, liquid seawater cannot become colder than -2 °C [8]. If the interaction with ice is considered, the structural temperature in the waterline area is of particular interest. It is influenced by both water and air temperature. Therefore, the structure temperature is estimated by thermal simulations in order to determine suitable temperature depended material curves and to predict the influence on the structural response in the collision scenario.

• Sled Tests and Simulation Results with Q10 Update Kit Euro NCAP 2020

  H. Ipek (Daimler)

• Solution Explorer in LS-PrePost – a GUI for Nonlinear Implicit FE

  T. Borrvall (DYNAmore Nordic)

  The evolvement of multiphysics capabilities in LS-DYNA has made it a very powerful, albeit somewhat complicated, simulation product. To this end, the Solution Explorer was introduced to simplify modeling setup in fluid mechanics, and this has now been complemented with a framework for nonlinear implicit mechanics. The vision of the Solution Explorer is to combine simplicity and power in an integrated pre- and post-environment, and this workshop presents its current state. We cover pre- and post-processing for single and multiple cases, in hope that it will provide a clear picture of its future potential.

• Springback in Assembly of Mirror Panels with Stamped Supports for Concentrating Solar Power Applications

  J. Pottas, J. Coventry (The Australian National University)

  Solar collector fields consisting of a large number of heliostats are used to reflect and concentrate sunlight onto a tower receiver (Figure 1a) in concentrating solar power (CSP) plants. In the most common tower CSP configuration, shown in Figure 1b, the concentrated light is used to heat a recirculating molten salt heat transfer fluid. A portion of this flow is used to generate steam immediately to drive a Rankine power cycle, while the remainder is stored in insulated tanks to enable 24 hour dispatchable power generation.

• Study on Blast and Ballistic Loading of Auxetic Composite Sandwich Panels with LS-DYNA

  N. Novak, L. Starčevič, M. Vesenjak, Prof. Z. Ren (University of Maribor)

  Response of novel structures designed for impact, blast and ballistic protection can be enhanced using composite sandwich panels, which are able to extend the energy absorption capabilities [1]. Cellular metals offer very good energy absorption to weight ratio and are consequently used as the core of such composite structures [2]. One of the most promising for this kind of application are auxetic cellular structures, which are modern metamaterials with some unique and superior mechanical properties [3]. They exhibit a negative Poisson’s ratio, i.e. they get wider when stretched and thinner when compressed, as a consequence of their internal structure deformation. The effect of negative Poisson’s ratio is useful for many different applications to enhance properties in density, stiffness, fracture toughness, energy absorption and damping [3]. In case of impact the auxetic material moves towards the impact zone and thus increases the penetration resistance. The conventional cellular materials with a positive Poisson’s ratio in contrast move away from the impact area. The benefits of using auxetic materials as core layers in sandwich panels are obviously crucial to increase the impact energy absorption capability.

• The 3rd Generation Crash Barrier Modeling Method and Application on MPDB

  Y. Wang (VAYU-TECH)

  As the car crash protocol evolves, crash barrier becomes stronger and stronger, Figure 1 shows the deformation comparison of frontal barrier ODB and MPDB, side barrier EU-MDB and IIHS-Side after crashing with a compact SUV, ODB bottoms out while MPDB has half depth left, EU-MDB has very large deformation while most part of IIHS-Side barrier even does not deform.

• The ANSA / LS-DYNA approach for IGA Simulations

  L. Rorris (Beta CAE Systems)

  Isogeometric Analysis (IGA), is maturing and becoming capable to be incorporated in industrial applications. Widely used in the automotive industry for crash analysis, LS-DYNA is the first commercial solver to provide IGA features. Highest accuracy and shorter run times make IGA effective for crash analysis. Nevertheless, the complexity of the current automotive models and the maturity of the already established methods and processes require the development of the respective IGA tools and processes to reach and exceed the current levels of effectiveness. The new technical challenges offer the opportunity for new solutions and improvements in engineering simulation technology.

• The Benefit of True Fracture Strain on Material Model Parametrization

  M. Schneider, M. Teschner, S. Westhäuser (Salzgitter Mannesmann Forschung)

  By means of numerical simulation, cars have become much saver and lighter at the same time (when focusing on chassis and body in white). The ongoing improvement of steel grades for the automotive sector has additionally supported this development. Nowadays, the last percentages of improvements can only be obtained by using the latest steel grades and a very realistic modeling of their strain hardening and failure behavior. In case of hot rolled steels with a thickness of 4.0 mm, this leads more and more often to a modeling based on solid finite elements. Focusing hot rolled steels with high yield strength and high formability, there is in addition the need for a modeling of anisotropic hardening.

• The Effect of Element Formulation on FSI Heart Valve Simulations

  G. Luraghi, F. Migliavacca, J. F. R. Matas (Politecnico di Milano)

• The Effect of HDR InfiniBand on LS-DYNA Simulations

  O. Maor, G. Shainer, Y. Qin, D. Cho (HPC-AI Advisory Council)

  From concept to engineering, and from design to test and manufacturing, engineers from a wide range of industries face the ever-increasing need for complex and realistic models to analyze the most challenging industrial problems; Finite Element Analysis is performed to secure quality and speed up the development process. Powerful virtual development software aims to tackle the need for finite element-based Computational LS-DYNA simulations with superior robustness, speed, and accuracy. These simulations are designed to run effectively on large-scale computational High-Performance Computing (HPC) systems.

• The Use of LS-DYNA for the Development of a Topology-Optimized Thin-Walled Shell Structure Manufactured by Die-Less-Hydroforming

  A. Metzger, T. Ummenhofer (KIT)

  Within the framework of sovereign research at the KIT Steel & Lightweight Structure and an accompanying research project [1], the aim was, following an idea by Ummenhofer and Metzger, to develop a hinged column with a cross-section tapering from the centre to the two ends. The result is an elegant minimalistic pillar called “Hybridstütze PERFECTO” (in English: Hybridcolumn PERFECTO) that is made of an outer thin stainless steel shell, a core of ultra high-strength steel located in the cross section center and a filling of the space in-between by self-compacting concrete.

• Tool Cooling Simulation for Hot Forming II. Experiments and Simulations

  T. Kuroiwa (JSOL)

  To fulfill recent regulations for automobile fuel economy great demand on saving weight of automobiles is growing. Since making a lighter car with conventional material loses occupant safety, at least stiffer materials with the same weight are needed. For example, use of CFRP (Carbon Fiber Reinforced Plastics), Aluminum, Magnesium or Titanium is attracting our attention in these days. But technique to handle these materials is still under developmental stage. High-tensile steels made by hot forming is one of the most promising candidate since it can realize better balance between cost and weight saving. In hot forming technique, heated blank material is pressed by tools and then quenched by various methods to cause martensitic transition of the blank to obtain high tensile steel. It is not only stiff but also has good shape freezing property, causing smaller springback of the stamped materials. As an another advantage of hot forming, steels as raw materials can be easily obtained all over the world, compared with other materials listed above. On the other hand its disadvantages is relatively large investment in plant and equipment such as chiller or cooling tower and costs for prototyping production of tools with pipes to run cooling water. In order to cause the martensitic transition of the blank materials, one needs to quench it sufficiently fast. We, JSOL, think that a CAE tool to calculate and predict the stiffness of high-tensile materials contributes to ensure their strength in mass production stage. Important points in accurate prediction are following: (i) to calculate phase transition of the materials correctly (ii) to predict cooling performance of the tools to ensure (i). By making these uncertainties clear it is expected that CAE is capable of reducing trials-and-errors on prototyping, causing reduction of tool designing costs. LSTC, Dynamore and JSOL have been working on formulating a manufacturing CAE solution to the hot forming techniques. For example, development of phase transition material models (*MAT_244, *MAT_254) will overcome the uncertainty (i) described above. We also have been investigating simulation technique for thermal-structural-fluid coupling calculation to demonstrate the behavior of cooling water flowing in pipes of the tools, corresponding to item (ii) above. In this paper we report the results of recent solution developments on the latter point.

• Topology Optimization of a U-Bend Tool using LS-TaSC

  D. Aspenberg (DYNAmore Nordic), N. Asnafi (School of Science & Technology)

  Metal additive manufacturing of stamping tool and die has a potential of reducing the lead time of forming processes, while at least not increasing the cost. As a part of a research project exploring the possibilities to use this type of tool manufacturing techniques, topology optimization using LS-TaSC has been utilized and one example case is presented in this paper, namely a U-bend tool. This paper looks at the possible benefits from using nonlinear simulations in topology optimization, the effect of chosen target mass fraction value, the interpretations needed of optimal results and the effects on the formed specimen after using an optimized tool. Results show that accounting for the time dependent pressure on the tool, rather than applying a form of equivalent static load, gives a different optimal topology. Some manual interpretations of the optimal results are also recommended, as well as studying the effects on the specimen from removing material on the tool side.

• Transient Dynamic Implicit Analysis for Durability Testing of Bus Seats

  A. Jensen, G. Laird (Predictive Engineering)

  A core challenge to any finite element analysis (FEA) is figuring out loads and how to apply them. For static events, it is usually straightforward. In the case of durability testing, loads are obtained from accelerometers mounted on vehicles that are driven for hours, if not days on test tracks or routes that hopefully replicate the most severe road conditions possible. These accelerations can then be numerically processed and used for various frequency domain analyses such as a random vibration analysis (i.e., PSD), a frequency response analysis, or steady state dynamics. Although powerful and useful, these solution sequences are all based on the linear normal modes response and do not account for the nonlinear evolution of the structure as it shakes, rattles and rolls. As for a nonlinear material response, forget about it. Our approach is to describe how one can take the full acceleration time history and with little sacrifice in accuracy, perform a nonlinear, transient dynamic implicit analysis over a time span of 5 to 10 seconds. The reason for choosing implicit analysis is based on two factors: (i) the necessity for finely detailed meshes in regions of high-stress, and (ii) quick solution times. A series of bus seats was analyzed using this technique and showed good validation against test track data. From a simulation viewpoint, this work could not have been accomplished without the use of the implicit solver since run times were in hours whereas trial explicit runs indicated run times in days on equivalent hardware running with 32 CPU-cores.

• Undamped Extension of a Nose Landing Gear

  H. Frey (Liebherr Aerospace), W. Lietz, U. Stelzmann (Cadfem)

  In aviation, components are categorized based on the consequences of a failure. This categorization significantly determines the development costs, test quantities and maintenance cost. A simulation can show how serious such a failure can be and thus simplify the classification of the components and finally may reduce costs. This paper describes the simulation of the undamped extension of a nose landing gear of an aircraft. Normally, a hydraulic cylinder is used to extend the landing gear in a controlled manner. The simulation will investigate what happens when this hydraulic cylinder fails completely. Then the landing gear drops down when opening the flaps simply due to its own weight and pushes hard into its end stop. The simulation should show, if afterwards a safe landing is possible.

• Use of LS-DYNA for Structural Fire Engineering

  G. Flint, E. Rackauskaite, A. Maani, A. Temple, P. Kotsovinos (Arup)

  Structural response in fire is complex and can only be properly investigated using finite element analysis considering non-linear geometry and material properties. Full scale fire testing to investigate the real response of structural forms to severe fires represents significant risks to researchers and is also expensive and difficult to undertake effectively. Therefore, computational tools are necessary for the safe design of structures under fire conditions. The majority of the computational tools currently used for structural fire analyses use static solvers. Explicit dynamic solvers such as in LS-DYNA are rarely used even though they are capable of dealing with highly non-linear problems.

• Using a Rolls-Royce representative engine model to evaluate scalability of LS-DYNA thermal solvers

  G. Blankenhorn, J. Wang, R. Grimes, F.-H. Rouet (LSTC), J. Ong (Rolls-Royce)

  In the Finite Element Modeling community there is a trend to use models with increasing modeling details which raises the numbers of elements and solution variables. The increase in solution variables has a big impact on the run time of the analysis. Reducing wall clock time is an important item in using numerical analysis in production. The wall clock time can be reduced by using improved CPU technology and hardware with a higher throughput and lower latency for memory, storage and interconnect. On the software side, the use of parallel models to utilize more cores in an analysis reduces the wall clock time. Key measure for reducing wall clock time is scalability, which is in general expressed as the reduction of the run time due to an increase of cores used for the analysis. LSTC is currently offering LS-DYNA in three different parallel models, namely shared memory parallel (SMP), massive parallel processor (MPP) and the combination of both models (HYBRID). The focus on these developments is scalability for all three parallel models. Scalability is influenced by several factors. Beside the already mentioned hardware environment, main contributors are the decomposition (MPP and HYBRID) of the model, the model size and application type. Scalability can not only be evaluated on a global implementation level. It needs to be evaluated on the application at hand and the features utilized in this analysis. This contribution discusses the scalability of thermal solvers offered by LS-DYNA MPP using a surrogate engine model from Rolls-Royce. Three thermal solver types are used with three different MPP rank count (4, 8 and 16). The scalability is measured using the wall clock time summary of the LS-DYNA runs found in the d3hsp files.

• Validation of a Newly Developed Cross-Flow High Temperature Heat Exchanger (HT-HE) using Multiphysics Simulation

  M. Rübsam, Prof. R. Altensen, Prof. M. Pitzer (THM)

  Heat-exchangers are devices used to transfer heat between two or more fluids and can be found in both heating and cooling processes. At high temperatures during operation, thermal induced stresses occur and can lead to the failure of the device. The Technische Hochschule Mittelhessen has, in cooperation with the company WK, started a research project for the development of a HT-HE, which is designed for operating temperatures up to 1100°C and the contact with aggressive chemical media. In order to develop an efficient HT-HE regarding the heat recovery, semi analytical calculations have been carried out to optimize the geometry of the heat exchanger. This study focusses on the validation of these semi-analytical calculations by using Multiphysics simulation. Due to the time costly simulation of transient fluid-structure-interactions (FSI) while taking high temperatures into account, special emphasis has been placed on the reduction of simulation time without losing accuracy. Initially, a number of simplified models were set up to control the bug-free operation of the relatively new ICFD-Solver. It has been shown that the necessary workarounds, due to some implementation errors, only had a minor effect on the heat transfer. Modifications have been added to the input data in order to significantly reduce simulation time without affecting the quality of results. The results of the simulations done with LS-DYNA show a qualitatively good correlation with the semi analytical calculations and improve the understanding of the thermo- and fluid dynamic processes inside the HT-HE during operation.

• Validation of a Thermal Radiation Problem using *BOUNDARY_RADIATION_ENCLOSURE

  G. Blankenhorn, R. Grimes, F.-H. Rouet, I. Gandikota (LSTC), B. Gysei, S. Malcom (Honda R&D)

  Thermal radiation problems are gaining interest in the automotive industry. Examples include paint drying and curing processes, determining material characteristics and deformation due to heat treatment, temperature distributions in muffler systems and heat shields in engine compartments. LS-DYNA has capabilities to couple the thermal solver with mechanical and multi physics solver. Solving for thermal convection, conduction and contact in three dimensions are already available in all parallel models LSTC are offering, namely shared memory parallel (SMP), massive parallel processor (MPP) and the combination of both models (HYBRID). Lately the thermal radiation feature has been extended to be used with massive parallel processor (MPP) version and a new solver to solve for radiosity. New developments are tested with verification examples and small test cases to determine the code functionality and expected results. Furthermore they have to show their applicability with validations of numerical models with experimental data. They also need to be evaluated regarding their scalability of wall clock time to reduce costs of compute resources. This contribution addresses two of these subjects, the scalability and the validation. The validation example used here is a part of a B-pillar which is heated up in an oven. Temperatures were measured at several locations of the sheet metal. Test data was provided by Honda R&D Americas, Inc. The test was modeled as a thermal radiation problem in an enclosure. Thermal radiation was modeled using the keyword *BOUNDARY_RADIATION_ENCLOSURE and was performed in LS-DYNA MPP. An LS-DYNA MPP scalability study was performed. Due to missing data for the thermal parameters, the heat capacity, thermal conductivity and emissivity were determined with LS-OPT.

• Vehicle Restraint System Optimization and Robustness Assessment using the Coupling between LS-DYNA, LS-OPT and DEP MeshWorks Software

  C. Goubel (DynaS+)

  Road safety structures are CE (European Commission) marked safety systems which need to be crash tested. Structure performances during the crash tests and the associated rating have a significant marketing impact for the system manufacturer and unfortunately depend on parameters subjected to stochastic variation (raw material mechanical properties, test conditions, vehicle design, …). Numerical simulation has been widely used for several decades to assist in the design of these new road safety devices. Historically, in order to identify a design likely to pass the experimental tests, simulation has mostly been used without taking into account the variability of the modelled system parameters but only its nominal design. However, in too many cases, the great variability of such devices (materials characteristics, ground type, assembly conditions, impact parameters, etc…) leads to unexpected behaviour (and results) and jeopardizes the test validation. In the following sections the full process of one road safety system optimization will be presented starting with the correlation between the numerical model results and the corresponding real crash test results. Then, a design optimization on a reduced model will be performed using an innovative approach based on an advanced use of the DEP MeshWorks morphing capabilities coupled with LS-OPT© and LS-DYNA©. Finally, based on the optimal design found previously, an additional sensitivity study using LS-OPT and LS-DYNA will be conducted to better assess the device robustness and its sensitivity to material characteristics changes. The aim is to enable designers of new systems to better assess the risk of failure when performing the experimental tests required by the standard.

• Virtual Modeling of Forming Processes in Metal Packaging Industry

  I. Moldovan, M. Linnepe, L. Keßler (thyssenkrupp Steel Europe), M. Köhl (thyssenkrupp Packaging Steel)

  Nowadays the finite element method is technical standard in many industry sectors such as automotive manufacturing. Thus the material behaviour for steel applications in this field is extensively developed. In packaging industry, virtual approaches in process- and product development are more the exception. Instead, the cost-intensive and time-consuming trial-and-error method is commonly used to approach the limits of the material specific formability. Packaging steel is characterised by thicknesses between 0.1 to 0.49 mm and thyssenkrupp Packaging Steel offers strengths between 180 to 750 MPa. However, with tougher process limits, especially due to continuous thickness reduction, this method has its limitations. Speaking of material saving and optimisation simulation tools are gaining increasingly importance. In contrast to the automotive industry, established approaches for material characterisation do not exist and not all norms cover that low thickness range for sheet materials. The following work gives an indication of current possibilities for material characterisation of thin steel sheet. A completed validation ensures process and product designing with available material models.

• Virtual Testing of Curved Vehicle Restraint Systems

  B. Fröhlich (Bundesanstalt für Straßenwesen)

  Real crash tests against vehicle restraint systems according to the standard EN 1317 are performed with straight barriers. The objective of this study is to investigate the performance of a curved barrier. A validated model of a real tested vehicle restraint system was subjected to a modification. The straight barrier in the original simulation model was modified with different constant curvatures. Virtual crash tests with straight and differently curved barriers were carried out with the same boundary conditions as the real test. The results concerning the behavior of the vehicle and the barrier were compared. The expected consequences of a barrier in a curve are the following: The vehicle is contained by the barrier. The dynamic deflection of the barrier during the crash is lower than the dynamic deflection of the unmodified straight barrier. The acceleration severity increases due to the curvature of the barrier.