12th International LS-DYNA Conference

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Detroit, 2012
A Comparison between Three Different Blast Methods in LS-DYNA: LBE, MM-ALE, Coupling of LBE and MM-ALE

Z. S. Tabatabaei (PhD Candidate, Missouri University of Science and Technology), J. S. Volz (Assistant Professor, Missouri University of Science and Technology)

A previous experimental test was modeled in LS-DYNA®. Three different methods of simulation were performed. These methods are empirical blast method, arbitrary Lagrangian Eulerian (ALE) method, and coupling of Lagrangian and ALE method. Free field pressure history recorded from experimental test was compared with the first method. Peak pressure for all these three methods were compared together and discussion of results is provided. Keyword: Blast, Lagrangian (LAG), Load Blast Enhanced (LBE), Multi-Material Arbitrary Lagrangian Eulerian (MM- ALE), LS-DYNA

A Comprehensive Study on the Performance of Implicit LS-DYNA

Y.-Y. Lin (Hewlett-Packard Company)

This work addresses four aspects of Implicit LS-DYNA’s performance. First, Implicit LS-DYNA’s scalability is characterized on multicore platforms. Second, the effectiveness of the GPU implementation is examined. Third, the effect of memory configuration on performance and information on how to configure optimal memory size for a system are presented. And fourth, the performance of out-of-core solutions is discussed.

A Finite Element Model of the Pelvis and Lower Limb for Automotive Impact Applications

C. D. Untaroiu (Virginia Tech), J. Shin, N. Yue (University of Virginia), Y.-H. Kim, J.-E. Kim, A. W. Eberhardt (University of Alabama at Birmingham)

A finite element (FE) model of the pelvis and lower limb was developed to improve understanding of injury mechanisms of the lower extremities during vehicle collisions and to aid in the design of injury countermeasures. The FE model was developed based on the reconstructed geometry of a male volunteer close to the anthropometry of a 50th percentile male and a commercial anatomical database. The model has more than 625,000 elements included in 285 distinct components (parts). The material and structural properties were selected based on a synthesis of current knowledge of the constitutive models for each tissue. The model was validated in seventeen loading conditions observed in frontal and side impact vehicle collisions. These validations include combined axial compression and bending (mid-shaft femur, distal third leg), compression/flexion/xversion/axial rotation (foot), and lateral loading (pelvis). In addition to very good predictions in terms of biomechanical response and injuries, the model showed stability at different severe loading conditions. Overall results obtained in the validation indicated improved biofidelity relative to previous FE models. The model may be used in future for improving the current injury criteria of lower extremity and anthropometric test devices. Furthermore, the present pelvis and lower limb was coupled together with other body region FE models into the state-of-art human FE model to be used in the field of automotive safety.

A New Method for Efficient Global Optimization of Large Systems Using Sub-models HEEDS COMPOSE Demonstrated on a Crash Optimization Problem

N. Chase, R. Sidhu, R. Averill (Red Cedar Technology)

Executing full vehicle finite element simulations can be very time consuming and expensive. Compound this with the large number of evaluations required for crash optimization problems due to their complicated design landscapes, and optimization of full vehicle crash simulations becomes very computationally expensive and difficult. An ideal solution is to reduce the full vehicle down to a manageable sub-model which runs significantly quicker while maintaining the boundary constraints as if utilizing the full vehicle model. The optimization process can then be managed with this sub-model while achieving significant improvements in computational requirements. This paper will demonstrate how to optimize the a-pillar, b-pillar, roof rail, rocker, front header, and roof bow components of a car for roof crush, utilizing Ultra High Strength materials. In addition to the gauge of the individual structural components, a soft zone trigger and its location within the b-pillar are introduced as design variables. LS-DYNA® is utilized as the simulation tool with the new COMPOSE (COMPonent Optimization in a System Environment) feature within the HEEDS-MDO optimization software utilized to perform the optimization. COMPOSE is a new module that enables the use of a sub-model for optimization in a way that significantly reduces the overall optimization time while encouraging the interactions of the optimal subsystem with the global model to be consistently maintained. This creates a design that gives a similar high performance in the global model as was found in the sub-model. It is shown here that the use of COMPOSE can significantly decrease the design time for finding high performing designs for the roof crush optimization, over a traditional global optimization approach. In addition, it is shown that performing an optimization on the sub-system level by using the original boundary conditions from the global model is not a robust approach for this optimization. The study shows that to take advantage of the reduced runtime in the sub-system model, the COMPOSE technology provides a robust solution for efficient optimization of the system.

A Pre-processor Software for the Calibration of Material Models for LS-DYNA

H. Lobo (Matereality)

LS-DYNA contains a wealth of material models that allow for the simulation of transient phenomena. These models are often quite complex and difficult to calibrate. We present CAE Modeler, a generalized pre-processor software used to convert material property data into material parameters for different material models used in CAE. In this paper, CAE Modeler is used to streamline the conversion of rate dependent stress-strain data into material parameters for the MAT_024 material model. The interactive software is capable of handling all three rate dependency options of MAT_024 and outputs a data file that can be read directly into LS-DYNA. Support for other material models is envisaged.

A Tutorial on How to Use Implicit LS-DYNA

R. Grimes (LSTC)

This talk will focus on the issues of using the Implicit features of LS-DYNA. Implicit has a profoundly different footprint regarding the computational resources required than an explicit simulation. This talk will especially focus on the management of those computational resources, especially for distributed memory computations. This talk will also include an overview of techniques for debugging models for use by Implicit.

Advance in Sheet Metal Forming – One-step Solution, Multi-Beads, Gravity Prebending, Auto Nets, and Local Compensation

X. Zhu, L. Zhang (LSTC)

Some of the new features developed since the last conference will be discussed. 1)A fast one-step sheet metal forming program Developed mostly for blank size estimation and forming effect initialization in crash simulation, this powerful feature allows hundreds of parts to be simulated in a very short time. 2)An improvement to the contact draw bead Developed together with Ford Motor Research and Advanced Engineering Laboratory, multiple beads can now be generated automatically based on the base draw bead definition, to represent the actual bead width and forces. This more realistic approach allows for a better blank size prediction and utilization. 3)Pre-bending for gravity simulation Developed together with Ford Motor Company, blanks can now be pre-bent to simulate the various scenarios of stamping press destacker loading of the sheet blank to the draw die. This new approach produces a more realistic gravity-loaded blank shape, resulting in shorter die travel and better stamping quality. 4)Automatic fixture nets for free-standing springback simulation This feature allows for automatic generation of fixture nets of user-specified sizes, in user specified locations, with contacts automatically established, for a free-standing springback simulation. 5)Springback compensation for localized multi-regions Developed together with Chrysler LLC, local compensation of stamping dies can be extended to multiple regions.

Advance in Sheet Metal Forming – Failure Criteria, Friction, Scrap Trimming and Adaptive Meshing

L. Zhang, X. Zhu (LTSC)

Some of the new features developed since the last conference will be discussed. 1)Directional and pressure sensitive friction model for metal forming Developed together with Ford Motor Research and Advanced Engineering Laboratory, this feature enables definition of Coulomb frictions in any directions in the sheet plane. The friction coefficients can also be scaled based on the contact pressure incurred during the stamping process. 2)Failure criterion for the non-linear strain path for *MAT_036 Developed as a part of the ASP-NSP project, the previously known Formability Index (F.I.) is now implemented together with *MAT_036. Verification of the model will be discussed. 3)Contact-based scrap trimming function Developed together with Ford Motor Company, this powerful feature allows realistic scrap trimming simulation and contact-based kinematic and dynamic transfer from the trim steels to the trimmed scraps. 4)Pre-adaptive along curves for line-die simulation Developed together with Chrysler LLC, a region of user specified size can now be defined for mesh adaptivity along a curve for subsequent line-die simulation.

ALE Adaptive Mesh Refinement in LS-DYNA

N. Aquelet (LSTC)

An adaptive mesh refinement capability was implemented in the 3D MMALE (Multi-Material Arbitrary Lagrange Euler) code. It automatically and locally refines (or coarsens) ALE hexahedral solid elements. The keyword *REFINE_ALE (or *ALE_REFINE) activating this feature has 3 lines of parameters that enable 3 different kinds of refinement. If the keyword has only one line, the refinement is static and only occurs during the initialization. If the second line is added, the refinement becomes dynamic. Adding the third line allows removing refined meshes.

ALE Incompressible Fluid in LS-DYNA

N. Aquelet, M. Souli (LSTC)

The computation of fluid forces acting on a rigid or deformable structure constitutes a major problem in fluid- structure interaction. However, the majority of numerical tests consists in using two different codes to separately solve pressure of the fluid and structural displacements. In this paper, a monolithic with an ALE formulation approach is used to implicitly calculate the pressure of an incompressible fluid applied to the structure. The projection method proposed by Gresho is used to decouple the velocity and pressure

ALE Modeling of Explosive Detonation on or near Reinforced-Concrete Columns

J. M. H. Puryear, D. J. Stevens, K. A. Marchand (Protection Engineering Consultants), E. B. Williamson (University of Texas), C. K. Crane (USACE Engineer Research and Dev. Center)

The detonation of explosive threats in contact with or near reinforced concrete columns was modeled using the Arbitrary Langrangian-Eulerian (ALE) capability of LS-DYNA, in support of the development of a software tool for assessing the vulnerability of structures subjected to terrorist attack. The explosive, air, and concrete were modeled as fluids, and the reinforcement was modeled using beam elements. *MAT_72R3 was used for the concrete, and column damage was characterized using the scaled damage measure, an output from the constitutive model that quantifies damage to the material. The model was initially validated against a large database relating spall and breach thresholds of reinforced concrete slabs to charge weight and standoff. It was further validated against a small database for explosive loading against reinforced concrete columns. A parameter study was then performed to populate a results space comprising four column shapes over a representative ra nge of dimensions. This results space was used to develop a fast-running algorithm that will be implemented in the structural vulnerability assessment software.

An Efficient Modeling Procedure for Simulation of Dynamics of Adhesively Bonded Joints

Anindya Deb, Indrajit Malvade (CPDM, Indian Institute of Science)

The present study is aimed at developing a new computationally efficient modeling procedure that predicts well the nonlinear mechanical behavior of adhesively bonded joints. The approach is thought to be particularly beneficial for computationally intensive vehicle crash simulations. Two other conventional modeling approaches are considered, that is, accounting for adhesive layer between shell-based substrates/flanges with monolithic solid elements, and defining a tied contact with failure condition in lieu of the solid elements. The approach presented here and not previously reported in the literature is an enhancement of the latter technique with equivalent properties being assigned to the substrates in the overlap segment of a joint model. A semi-analytical procedure is outlined in detail for arriving at the equivalent properties of substrates by accounting for shear properties of an epoxy adhesive which is geometrically not represented in the model. It is shown that the effect of strain rate on adhesive behavior can be elegantly incorporated in the proposed equivalent property-based approach via Material Type 24 in LS-DYNA for intended applications of dynamics such as vehicle crash safety assessment. The computational efficiency and accuracy of the present approach are established by comparing results yielded by it against experimental data and detailed shell-solid modeling technique.

An Efficient New Sequential Strategy for Multi-Objective Optimization using LS-OPT

N. Stander (LSTC)

®A new surrogate-assisted Multi-Objective Optimization algorithm has been implemented in LS-OPT . The algorithm, known as Pareto Domain Reduction, is an adaptive sampling method and an extension of the classical Domain Reduction approach (also known as SRSM). A Multidisciplinary Design Optimization (MDO) example involving a vehicle impact is used to demonstrate that the accuracy is very close to the NSGA-II “exact” method while using a small fraction of the computational effort.

Analysis of the Scatter of a Deploying Airbag

R. Brown, M. Bloomfield (JaguarLandrover), C.-A. Thole, L. Nikitina (Fraunhofer Institute SCAI)

This paper discusses some of the challenges faced by the automotive industry in dealing with the natural variation in input parameters and environmental factors that lead to scatter in results. We describe how a lack of consideration of this variation can lead to surprises during testing, with the associated risk of unplanned cost, and present a technique using Principal Components Analysis to improve the robustness of CAE crash models. In a purely virtual product development world, increasingly demanding functional requirements, and pressure on weight and cost, mean that analysis techniques must lead to designs that are robust with respect to external noise sources; large safety margins are no longer acceptable. Conventionally the CAE process has used nominal values for input parameters, and has been satisfied with single, deterministic solutions. However, virtual techniques have much to offer in understanding and managing scatter, and the consideration of variability in the CAE process is becoming more common-place. At the same time, the CAE method introduces its own issues associated with model stability, and these must also be addressed before design optimisation is attempted. Frequently, analysis approaches used to improve design robustness can also be applied to issues of model stability, and we describe an example where Principal Components Analysis within the Diffcrash software package has been used to identify a source of instability in an airbag model. The mathematical background to the PCA method is presented, explaining its application to the analysis of variation, and showing how it can help in locating a source of scatter in results. The airbag example illustrates how this can be applied to allow changes to the modelling technique (or to the design) to be made to reduce the scatter. In this example, the source of the different airbag behaviours shown in figure 1 was identified as being a contact issue at an earlier point in time (figure 2), and a modification to the contact definition led to a reduction in the dispersion in results. Lastly we offer insight into the requirements for deployment of such techniques, and describe how process integration is a fundamental necessity for a successful, sustained implementation.

Application and CAE Simulation of Over Molded Short and Continuous Fiber Thermoplastic Composites, Part I

P. S. Kondapalli, K. Grumm (BASF Corp.)

Short Fiber Reinforced Thermoplastics (SFRT) such as glass filled Polyamide 6 and 66 have been widely adopted as a metal replacement in a wide range of industries. The main advantage of using these materials is high strength to weight ratio, light weight, parts consolidation, easy manufacturability etc. Continuous Fiber Reinforced Thermoplastics (CFRT) are also gaining popularity because of its ability to achieve high directional stiffness/strength by tailoring the number of layers and angles. Applications which combine these two by over molding SFRT on CFRT inserts are still in its infancy. One of the hurdles is the lack of good CAE simulation capability for such applications. This paper describes the CAE tools that are developed using LS-DYNA to successfully model static and dynamic behavior of such parts. Material 58 in LS-DYNA is used for modeling the CFRT material while a User Defined Material Law models the SFRT material and they are coupled together through suitable contact definitions. Its applicability is verified through a number of examples varying from very simple to complex configurations

Application and CAE Simulation of Over Molded Short and Continuous Fiber Thermoplastic Composites, Part II

P. S. Kondapalli, K. Grumm (BASF Corp.), Y. Cao (Faurecia North America), V. Laurent (Faurecia Europe)

Automotive seating back frames for front row are mostly constructed from high strength steel in order to meet very rigorous crash requirements. The main requirements are meeting the rear impact and luggage retention behavior as specified by the standards. In this paper, seating back frames constructed from over molded Short Fiber Reinforced Thermoplastics (SFRT) on Continuous Fiber Reinforced Thermoplastics (CFRT) inserts are described. One of the challenges is accurate CAE simulation of the static and dynamic behavior of such parts. CAE tools using LSDyna were developed to model accurately the rear crash and luggage retention behavior. Designs validated through CAE analyses were used to cut the tool and build prototype parts. Physical tests on Prototype parts confirmed good correlation between the tests and FEA. They met all the required criteria without requiring any design changes.

Application of Crack Propagation Simulation of Windshield to Roof Strength Analysis

R. Chikazawa, T. Komamura, S. Yamamoto, T. Yasuki, S. Kojima (Toyota Technical Dev. Corp.)

This paper describes a new modeling method to represent the crack propagation of windshield, namely the laminated safety glass. In the roof strength analysis used for vehicle development process, it is not easy to accurately predict crack propagation paths with existing modeling method, e.g., improving material properties. If the windshield cracks in a test using a prototype vehicle, the body deformation in the simulation and that in the test might not match, resulting in a less accurate simulation of force transfer to vehicle frames through the windshield. Therefore, prediction of crack propagation in a windshield is significant in accurately estimating the deformation and improving the accuracy of roof strength simulation results. The new modeling method to represent the crack propagation of the windshield was applied using tied overlapping shell technique, one of the modeling methods for material fracture, which has been developed by Kojima et al. The tied overlapping shell technique consists of element groups made of base elements and overlapping elements which are rotated 45 degrees in the normal direction. The base and the overlapping elements are connected using tied contact. The physical laminated safety glass windshield is constructed by placing an adhesive polyvinyl butyral (PVB) interlayer between two glass panes, outer glass and inner glass. In this study, double overlapping shell parts and a PVB interlayer part were applied to a windshield model to represent the crack propagation of the glass. Consequently the model has three layers with five mesh plates. Each part is modeled with shell elements and positioned corresponding to the neutral location of each layer thickness respectively. Four-point bending tests using specimens cut out of windshield glass were carried out to determine the critical fracture strain of glass considering the loading mode in roof strength analysis. Thereafter, application of the windshield glass model developed in this study to a roof strength analysis model was carried out to validate against test data. This paper summarized the application of new modeling method to represent the crack propagation of windshield glass in a roof strength analysis. It was found that the first two cracks propagation and the maximum force of the roof strength could be simulated. In the model the first two cracks propagated in the same shape as seen in the test. However, the number of crack propagation paths observed in the simulation was just two while there were many crack paths observed in the test. In addition, the difference in the maximum force of the roof strength between in the simulation and in the test was approximately 1%. However, after the cracks occurred, the force dropped more rapidly in the simulation than in the test. With this consideration there may be room for correction of the elimination methods.

Automated Post Simulation Analysis, Mining, Reporting and Collaboration with d3VIEW

A. Nair, S. Bala (LSTC)

Data management, mining, comparison and presentation play vital roles in utilization of Finite Element Analysis for product design and decision making. Post simulation interpretation of results is largely a manual process and interpretation of data points is limited to only a handful of data points. The capability to perform such tasks seamlessly will reduce workload for an engineer and help focus his attention more on engineering rather than spend time generating reports. d3VIEW is a simulation data management and collaboration software that is tightly integrated with LS-DYNA to automate post-simulation analysis. This paper will discuss the evaluation of d3VIEW. Publicly available LS-DYNA finite element models are used to showcase d3VIEW’s capability. d3VIEW’s ability to extract LS-Dyna results, store and compare data, generate reports using templates, visualization and collaboration are highlighted. Collaboration of reports generated automatically with peers and management would give instant access to qualitative and quantitative post processing of simulation results.

Automated Post-Processing & Report-Generation for Standard Crash & Safety Tests Simulation

T. Nikolaos (BETA CAE Systems S.A.)

There are an increasing number of standardized tests, for which a vehicle should comply with. All these tests, usually, require the generation of a standardized report. For the generation of reports for simulated tests, after each solver run, the followed post-processing actions are always the same. Most of the tasks in the post-processing of simulation of road vehicles crash tests, involve repeated actions while, in certain cases, these actions may represent up to 90% of the total. This repetition is proven cumbersome, time-consuming and prone to errors. Therefore, the automation of the execution of those actions and the subsequent report generation is required. This paper presents software tools that automatically process and create reports, for Pedestrian Safety analysis, Occupant Protection in Interior Impact (FMVSS 201U), IIHS structural ratings and Bus Rollover (ECE R66), based ®on LS-DYNA results. These tools streamline the extraction of the results for the respective tests. They lead directly to reports and create overview models for supervisory evaluation in cases of a large number of simulation runs. The automation of complicated post-processing procedures in μETA (mETA), the Post-Processor of BETA CAE Systems S.A., not only saves time and eliminates user’s frustration but it also assures an error-free outcome. Keywords: Post-processing, process automation, reporting, Pedestrian Safety, FMVSS 201U, IIHS, Bus Rollover ECE R66.

BEM Methods For Acoustic and Vibroacoustic Problems in LS-DYNA

M. Souli, Y. Huang, R. Liu (LSTC, University of Lille Laboratoire Mecanque de Lille, JSOL Corp.)

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

Benchmark of Topology Optimization Methods for Crashworthiness Design

C. H. Chuang, R. J. Yang (Ford Motors Company)

Linear structural topology optimization has been widely studied and implemented into various engineering applications. Few studies are found in the literature which deals with nonlinear structures during vehicle impact events. One of the major challenges for nonlinear structural topology optimization is the unavailability of design sensitivities in impact simulations, due to the highly nonlinear and computationally intensive nature of these problems. In this paper, three commercially available methods are reviewed and discussed: Equivalent Static Loads (ESL), Hybrid Cellular Automata (HCA), and Inertia Relief Method (IRM). A vehicle structure, subjected to a full frontal impact, is used to compare the topology optimization results generated using HCA and IRM.

Boundary Element Analysis of Muffler Transmission Loss with LS-DYNA

Z. Cui, Y. Huang (LSTC)

This paper presents a case study of applying the boundary element method (BEM) in LS-DYNA for calculating transmission loss (TL) of mufflers. Both the three-point method and the four-pole transfer matrix method are used for calculating the transmission loss. The three-point method is easier to use, but it solves for the transmission loss only and nothing else. The four-pole method has the advantage of providing transfer matrix of the muffler, which contains important parameters when the muffler is connected to another muffler or other components in the silence system. Numerical predictions are examined by experimental results and theoretical results for all test cases. The results show that LS-DYNA can be used to perform muffler transmission loss analysis effectively.

Certification by Analysis of a Typical Aircraft Seat

N. Dhole, V. Yadav, G. Olivares (National Institute for Aviation Research)

Advancements in computer hardware in recent years have made it possible to solve complex real world problems using finite element methods (FEM). Full scale dynamic certification testing of aircraft seats is a very complex, expensive and time consuming process. A high acceleration pulse is applied on the seat structure in a short duration of period, and the seat structure has to pass stringent FAA certification criteria. FAA and the aircraft industry are working together to reduce the cost and time required for certification of the seat while improving occupant safety. This is being achieved by using a process known as Certification by Analysis or CBA where the seat is certified using finite element methods. The process and guidelines for CBA are described in advisory circular AC 20-146 developed by the FAA. As per the AC 20-146, FE models can replace the actual dynamic testing scenarios such as: 1) demonstrating compliance to standard test requirements for changes to a baseline seat design, 2) establishing the critical seat installation/configuration in preparation for dynamic testing. This paper describes in detail different techniques that can be used for the validation of a FE model of typical aircraft seat using the finite explicit code LS DYNA. As an example, the FE model of an aircraft seat is validated against the full scale dynamic test conducted as per AC 25.562.

Comparison between Experimental and Numerical Results of Electromagnetic Tube Expansion

J. Shang, S. Hatkevich, L. Wilkerson (American Trim LLC)

Electromagnetic forming is a complex coupled mechanical-thermal-electromagnetic phenomenon. To accurately simulate this high-velocity and high-strain-rate process, electromagnetism (EM) module of LS-DYNA has been developed. In this paper, the predictive ability of the EM module is assessed through a comparison between experimental and numerical results of electromagnetic tube expansion. The experiment was to apply electromagnetic forming for expansion of Al 6061-T6 tube. Photon Doppler Velocimetry (PDV) was used to measure the velocity during the tube expansion. This process was also modeled using LS-DYNA EM module. Different parameters of Johnson-Cook strength model for Al 6061-T6 were applied to verify the constitutive model parameters for Al 6061-T6. Moreover, 2D axi-symmetric simulations with different mesh densities were performed in this case. A comparison of the expansion velocity between experimental and numerical results is presented and discussed. The good agreement was found between the experimental and numerical results.

Computer Generation of Sphere Packing for Discrete Element Analysis in LS-DYNA

Z. Han, H. Teng, J. Wang (LSTC)

The constructive algorithms for sphere packing are based on the pure geometrical computation. They are very efficient and robust for building very large sphere packings with millions of spheres in a few minutes. A constructive algorithm has been developed in LS-DYNA for arbitrary 3D geometries with the size distribution control. The brief introduction of the algorithm is presented in this paper. The procedures and some generated sphere packings are also presented to demonstrate its application for the discrete element analysis by using LS- DYNA.

Consideration of Orientation Properties of Short Fiber Reinforced Polymers within Early Design Steps

G. Gruber, A. Haimerl, S. Wartzack (Chair of Engineering Design KTmfk. University of Erlangen-Nuremberg FAU)

Abstract Within the modern automotive industry there is an increasing application of parts made of short fiber reinforced polymers (SFRP). The reasons are their beneficial mechanical properties and their series production capability. However, the prediction of their crash behavior by simulation is very complicated, since a precise simulation requires considering the fiber orientation distribution. That’s why, in early design steps often only imprecise, isotropic simulation approaches are deployed in order to save calculation time and license costs for additional software tools. The aim of the present paper is to introduce a simplified simulation approach allowing an anisotropic simulation taking into account the orientation data obtained by an injection molding simulation. To ena ble its application in ®early design steps only standard functions already implemented in LS-DYNA are deployed. The complex material behavior of short fiber reinforced polymers is represented by overlapping two standard material models of LS-DYNA in one single shell definition. The input parameters of the resulting phenomenological material description are obtained by using optimization methods. The methodology being used to convert the orientation data in order to set up an executable input deck is supported by two self-developed software tools. The first software tool extracts the orientation angles from the process simulation by assigning fiber orientation tensors to corresponding shell elements of the mesh of the crash simulation. For each shell element the orientation data are averaged and projected on the shell. By doing so, the complex orientation state is reduced to just three values per shell element – one fiber orientation angle and two fiber orientation probability values. Based on these data, the second software tool creates the executable input deck. The legitimacy of the presented approach is proved by an experimental validation: SFRP-plates are analyzed within a drop weight test. Despite the mentioned simplification (reduction of the complexity of the orientation state) the numerical results show a strong correlation with the experimental data.

Crash Impact Modelling Of Security Bollard

S. K. Tay, B. Lim, S. H. Ng (Ministry of Home Affairs)

This paper presents the findings from vehicular crash test of a security bollard system, as well as findings generated from numerical simulations using two different loading approaches in LS-Dyna®. The differences between the results from numerical simulations and test observations are explored by examining the velocity-time history profiles of the vehicle and the rotational response of the bollard. The first approach involved a NCAC Chevrolet C2500 finite element pickup model impacting against the bollard model. Contact algorithm was defined to represent the contact of an impacting pickup with the bollard at the collision. In the second approach, the vehicle impact was instead represented by a force pulse generated from the actual crash testing. This approach greatly reduced the computational time required and the results showed good agreement with the vehicle model simulation applied in the earlier approach. These models can be useful tools for design work and provide alternative means to assess the performance of the security bollard system.

Design and Testing of an Easy to Use Pinned-down Temporary Concrete Barrier with Limited Deflections

N. M. Sheikh, R. P. Bligh (Texas Transportation Institute)

In work zones where the space available for placing a temporary concrete barrier is very limited, for example bridge replacement projects, the barrier must be strictly restrained to prevent lateral deflection due to vehicular impact. Among the few restraining or anchoring mechanisms currently available, most designs require through the deck bolting, anchor bolts, or other constraining straps. Such mechanisms are difficult to install, inspect, and remove and can result in damage to thin bridge decks. In this research, a new restrained F-shaped temporary concrete barrier was developed that is easy to install, inspect, and remove, and minimizes damage to the bridge deck or concrete pavements. The mechanism uses a pinned-down approach to restrain the barrier. Steel pins are simply dropped into inclined holes that start from the toe of the barrier and continue short distance into the bridge deck or concrete pavement. The pinned down anchorage design was developed through extensive use finite element analysis. The performance of the final design was evaluated by conducting a full-scale vehicle impact crash test. The pinned down barrier successfully passed the National Cooperative Research Program Report 350 Test Level 3 requirements. The maximum permanent and dynamic barrier deflections were 5.76 inches (146.3 mm) and 11.52 inches (292.6 mm), respectively.

Development of a Full Human Body Finite Element Model for Blunt Injury Prediction Utilizing a Multi-Modality Medical Imaging Protocol

F. S. Gayzik, D. P. Moreno, N. A. Vavalle, A. C. Rhyne, J. D. Stitzel (Wake Forest University School of Medicine, Virginia Tech)

Computational modeling is an increasingly important tool in the study of injury biomechanics. This paper describes the development and validation of a seated human body finite element model as part of the Global Human Body ®Models Consortium (GHBMC) project. The model was developed using LS-DYNA (LSTC, Livermore, CA) and is intended for blunt injury prediction. The geometry of the model is ba sed on a protocol that leverages the strengths of three clinical scanning methods; computed tomography (CT), magnetic resonance imaging (MRI), and upright MRI (i.e. subject in seated position). The protocol was applied to a living male volunteer (26 years, height, 174.9 cm, and weight, 78.6 kg) who met extensive anthropometric and health criteria. Computer Aided Design (CAD)) data were developed from the images, containing significant anatomical detail. Seventeen sub-substructures of the brain, 52 muscles of the neck, and all major organs of the thorax and abdomen, with associated vasculature, are represented in finite element model. The positioning of the axial skeleton and the location of organs were determined using upright MRI scans to represent the seated posture. A region-specific development approach was used, with five Body Region Centers of Expertise (COEs) focused on meshing and regional validation of the head, neck, thorax, abdomen, pelvis and lower extremity. The regional models were then integrated into a full body model. Mesh connections between neighboring body regions were assembled using techniques based on the geometry, element type, and anatomic purpose. This consisted of nodal connections for all 1-D beam and discrete element connections (e.g. ligamentous structures), 2D shells (e.g. the inferior vena cava to right atrium), and many 3D tetrahedral and hexahedral structures (e.g. soft tissue envelope connections between body regions). In cases where node-to-node connections were not made, (e.g. 3D muscle to bone insertions), contact definitions were implemented. The integrated full body model consists of 1.3 million nodes, and 1.9 million elements. Element types in the model are 41.0 % hexahedral, 33.8 % tetrahedral, 19.5 % quad shell, 5.1% tri shell, and 0.6 % others including beam and discrete elements. Non-linear and/or viscoelastic material models were used where appropriate. Simulations were conducted using MPP LS-DYNA R.4.2.1. The model has been validated against a number of frontal and lateral rigid impactor and sled tests. Two of these (a chest impact per Kroell and an abdominal impact per Hardy) are highlighted via computational benchmarking on a computational cluster running Red Hat Enterprise Linux 4.0. Benchmarking tests ranged from 8 to 88 nodes. Reductions in compute times are seen up to 80 CPUs. Using 64 CPUs, solution times for the 60 ms chest impact and 100 ms abdominal impact were 10 hours, 45 minutes and 12 hours, 10 minutes respectively. Through the use of a living subject, comprehensive image data, and extensive geometric validation, this model has the potential to provide a greater degree of accuracy in blunt trauma simulations than existing human body models. It will serve as the foundation of a global effort to develop a family of next-generation computational human body models for injury prediction and prevention.

Development of a New Software Architecture for LS-DYNA Applications

Tim Palmer (Engineering Technology Associates, Inc.)

Engineers and researchers are able to carry out complex, multi-physics simulations using LS- DYNA®. The scope of these simulations may include multiple solvers and multiple steps. The variety of simulations available in LS-DYNA® require a complete FE modeling software that allows for creation of all types of elements, materials, contacts and properties. While this complete coverage of all entities is critical, the ability to provide users a unique subset of the complete toolset, to address a specific simulation area, such as fluid-structure interaction or vehicle crash simulations. Inventium is a software architecture that provides both a complete coverage of all LS-DYNA® entities, but is configurable both by software architects and the user, to provide a set of streamlined tools to carry out a specific simulation task. Examples of customized menu systems and application tools will be presented for drop test, fluid structure interaction and vehicle crashworthiness simulations will be presented.

Development of Tied Overlapping Shell Technique to Simulate the Path of Crack Propagation in Polymer Parts

S. Kojima, K. Ishibashi (Toyota Tech. Dev. Corp.), T. Yasuki, H. Arimoto (Toyota Motor Corp.)

This paper describes a new finite element modeling technique to simulate the path of crack propagation in polymer parts. In this new technique “tied overlapping shell technique”, base and overlapping elements make up the finite element model surface. The overlapping elements are rotated 45 degrees with respect to the base elements and are connected by tied contact. Tied overlapping shell technique decreased mesh pattern dependency of FE crack propagation. Tied overlapping shell technique was applied to a polymer door trim model, and impactor crash FE analysis was performed. The result of the FE crack propagation path with the new technique correlated with the experimental result.

Drape Simulation: Textile Material Model for Correct Property Reproduction to Improve the Preform Development Process of Fiber-Reinforced Structures.

O. Döbrich, T. Gereke, Ch. Cherif (Institute of Textile Machinery and High Performance Material Technology, Technische Universität Dresden)

The deformation behavior of textiles requires unconventional assumptions for successful drape simulation. The ®special performances in shearing, stretching and bending were implemented in LS-DYNA with user friendly subroutines. The general deformation behavior was considered by particular strain rates. A fully nonlinear and orthotropic material model was implemented to reproduce the character of the deformation mechanisms, shearing and stretching. The nearly negligible bending resistance was realized within a laminate formulation, which allows to set up an independent bending performance. Additional features such as pseudo-plastic shearing deformation or bending rigidity controlled by the bending side and direction was included. The simulation model was used to carry out complex drape simulations. A special afford was made in dealing with textile pre-treatments, which have local effects on the deformation behavior. Fixations affect the drapability and improve the handling of textile preforms. The material model and consequently the drape simulation are tools for a complex development process for textile preforms. The complete virtual development chain can lead from the textile good, with its special mechanical behavior, over the caused localization for special pre-treatment zones to a fully shaped and self-stable preform for complex shaped fiber-reinforced structures. An approach for composing this development chain will be introduced and presented.

Dummy Model Validation and its Assessment

S. Stahlschmidt, A. Gromer, Y. Huang, U. Franz (DYNAmore GmbH)

This paper describes the dummy model validation process applied in several FAT and PDB pro- jects. The modeling activities started 19 years ago and the validation process was enhanced continuously during this period.

DYNAFORM 5.8.1 – New Features and Future Development

J. He (DYNAFORM Product Manager, Engineering Technology Associates Inc.)

This presentation will provide details regarding the recent release of DYNAFORM Version 5.8.1. DYNAFORM is an FEA software solution which guides the engineer through a wide range of stages in the manufacturing, from cost estimation and die face design to formability analysis, springback prediction and springback compensation. This version promises to deliver a robust environment for engineers to simulate and analyze the entire die system. Significant enhancements were included in this version, many of which are delivered through the Die Face Engineering (DFE) module. DFE now offers the capacity to parametrically build die faces for a symmetrical part. A new ‘product change replacement’ feature allows the user to retain the current die face design and simply drop in new product design surfaces, saving the user a great deal of time while providing greater flexibility. DYNAFORM 5.8.1 allows the user to set up a personalized ‘drawbead library’ which links the line bead force and the drawbead geometry shape. As a result, the user can elect to run the simulation with either the line beads or geometry beads. DYNAFORM future development will be focused on optimization which will significantly reduce the manual adjusting work for simulation engineers. This will ultimately make simulation analysis more automated.

Effect of Soil Material Models on SPH Simulations for Soil-Structure Interaction

R. F. Kulak (RFK Engineering Mechanics Consultants), L. Schwer (Schwer Engineering & Consulting Services)

Currently, civil engineering design practice uses liner elastic soil properties for many soil- structure interaction problems. However, this approach falls short for problems in which the structure and soil undergo large deformations. With the availability of the high-performance computing (HPC) cluster at the United States Department of Transportation’s Transportation Research and Analysis Computing Center [1], transportation researchers can investigate complex soil-structure interaction problems. One of these problems is the stability of bridge piers during flash floods [2]. For certain riverbed soils, the high-velocity water washes away the soil covering the bridge piers, and this scour action can eventually expose the bottom of the pier and footing. In order to simulate this complex behavior, it is necessary to model the response of the reinforced concrete column – including concrete material failure – and the nonlinear soil behavior. This paper addresses some of the issues related to soil modeling. The following four material models were studied: (1) MAT005, Soil and Crushable Foam; (2) MAT010, Elastic Plastic Hydro; (3) MAT025, Geological Cap; and (4) MAT079, Hysteretic Soil. The first step in modeling the soil is to choose an appropriate model. The second step is to obtain the material parameters required by the specific model chosen. Some basic models require only a few parameters while the more complex models require many more. For site specific analysis, soil testing is required and then skilled analysts extract the needed parameters. The parameters obtained from soil test are given for the above four soil models. The hydrostatic compression response predicted by each model is compared to experimental data. The MAT005 and MAT025 materials were used in a three-dimensional SPH simulation of a rigid platen being pushed into sand.

Engineering Analysis with Finite Elements – LS-DYNA for Undergraduate Student

J. D. Reid (University of Nebraska-Lincoln)

A typical college course in finite elements consists of learning the method in continuum mechanics (transient heat conduction and elastic stress analysis), from formulation of the governing equations to implementation in some software (such as Fortran or Matlab). This class is not such a course. Instead, this class concentrates on analyzing engineering systems; a challenging task regularly done by design engineers. Finite elements is the tool of choice for performing such analysis for many, many applications and corporations. Structural stress, heat transfer, fluid flow, and modal analysis are quite distinct from each other but can all be treated successfully with finite elements. Of course, some basic principles of the finite element method is required, as well as understanding of behavior, sensitivity and robustness relative to mesh density, boundary conditions, material properties and other influential parameters. But the emphasis is on the engineering analysis itself, not the tool. LS-DYNA is well suited for this endeavor because of its’ multi-physics capabilities.

Evaluation of Blast Mitigation Capability of Advanced Combat Helmet by Finite Element Modeling

S. Sharma, R. Makwana, L. Zhang (Wayne State University)

Primary blast wave induced traumatic brain injury and posttraumatic stress disorders have been observed in great number among military personnel in the recent Iraq and Afghanistan wars. Although combat helmets provide good protection against blunt/ballistic type threats, the current issue with military helmets is protection concerning the threats from primary blast wave. This study focused on investigating how combat helmets influence the blast- induced biomechanical loads in the human brain. Multi-Material Arbitrary Lagrangian Eulerian method was applied to simulate the wave propagation in the shock tube, the interaction of the shock wave with the human head, and the subsequent blast overpressure transformation through the head. The finite element model (FE) of Wayne State University shock wave generator (WSUSG) was developed and validated against experimentally measured side-on pressure time histories within the tube. Validated 3-D FE models of the human head and Advanced Combat Helmet (ACH) reported previously were used to predict the internal brain responses and assess the performance of the helmet in mitigating shock wave of various severities generated by WSUSG. Effectiveness of helmet with respect to various head orientations to oncoming shock waves was also evaluated. Biomechanical response parameters including the peak brain pressures and strains at various regions of the brain were calculated and compared between the heads with and without helmet. Wearing ACH was found to mitigate the intracranial pressures up to 33% at given blast loading conditions. The peak brain strain was reduced by 13-40% due to the use of helmet. In generally, ACH exhibited increased protective performance as the shock intensity increased. The current ACH helmet design offered superior protection to the brain in sideways blast than that in forward blast loading condition of same severity.

Evaluation of LS-DYNA Material Models for the Analysis of Sidewall Curl in Advanced High Strength Steels

A. Aryanpour, D. E. Green (University of Windsor)

Accurate modelling of the Bauschinger effect and anisotropic plasticity in advanced high strength steels (AHSS) is essential in order to accurately predict sidewall curl. In this study, the performance of several constitutive models from the LS-DYNA library was evaluated for the prediction of sidewall curl in a plane-strain channel draw process for two grades of AHSS (TRIP780 and DP980). Since the profile of the channel section after springback results from the recovery of elastic strains in a plastically deformed sheet metal, the stress distributions in the channel section after the forming stage were carefully examined. Deformation modes in the sheet metal included sliding under the binder pressure, successive bending-unbending through a drawbead and drawing over the die entry radius. Material types 24, 36, 37 and 125 were used with shell element formulation 16 in order to select the most accurate combination for predicting sidewall curl. An investigation of simulation results showed that MAT125 predicted the sidewall curvature more accurately than the other models.

Experimental Investigation and FE Analysis of Fiber Woven Layered Composites under Dynamic Loading

P. A. Mossakovsky, F. K. Antonov (Reaserch Institute of Mechanics of Lomonosov Moscow State University), M. E. Kolotnikov, L. A. Kostyreva (FSUE), A. M. Bragov, V. V. Balandin (Reaserch Institute of Mechanics of Lobachevsky State University of Nizhni Novgorod)

Woven composites are used in a wide range of industrial applications such as development of individual body armor, aviation, astronautics and others . Thus, it is important to learn the mechanical behavior of the composite and to perform it’s adequate modeling under dynamic impact loading. The paper is concerned with modeling of woven fabric composite made of aramid yarns. The experimental investigation including static tests, dynamic tests with the Split Hopkinson Bar and ballistic impact tests was performed. The full-scale model with yarn-level detalization was constructed using obtained experimental data. The method allows getting qualitative results on the small specimens but realistic analysis of real-size models consisted of billion elements requires huge computational resources. So the paper is focused on the development of the alternative homogenized macro-model of the layered composite.

Faster Metal Forming Solution with Latest Intel Hardware & Software Technology

N. Meng (Intel Corporation), J. Sun (LSTC), P. J. Besl (Intel Corporation)

Reducing part development time & cost and increasing quality & productivity have always been important goals in the metal forming industry. Quick response to frequent mould change is challenging metal forming simulation engineers in the modern high efficiency production environment. To achieve these goals, a requirement for nearly instant numerical simulation of metal forming processes is emerging. Unfortunately, poor scalability and slow I/O due to adaptive remeshing as well as long waiting times in corporate HPC job queues are all bottlenecks to instant numerical simulation of metal forming processes. Three optimized ®workstation solutions using new Intel hardware and software technology are proposed. The proposed solution addresses these issues through code optimization using the latest ® ® ® 1Intel compiler technology, Intel Xeon processor E5-2600 product family processor, the 2nd ®generation Intel Solid State Device (SSD) technology, and the new Advanced Vector Extension 3(AVX) instruction set. The proposed solution allows metal forming simulations to be run on a local workstation with promising turnaround times. The performance of optimal configurations is discussed for real customer workloads in this paper.

Finite Element Simulations of Blasting and Fragmentation with Precise Initiation

M. Schill (DYNAmore Nordic AB), J. Sjöberg (Luleå University of Technology)

By using blasting caps with electronic delay units, it is possible to control the time of ignition between the boreholes of a mine. This has opened up new possibilities to optimize the blasting in order to achieve a better fragmentation which would significantly reduce the costs for the mining industry. The potential benefits of being able to control the ignition times has been described by Rossmanith [1], where stress wave interaction should according to theory and experience result in higher fragmentation, throw, swelling and digability. This theory has in this work been tested through Finite Element simulations using the LS-DYNA software. The rock material used is Westerly granite, which has been modeled with the RHT material model and it uses damage mechanics to describe the fracture of the rock. Also, a 2D-fragmentation evaluation routine has been proposed that makes it possible to study the level of fragmentation in section cuts of the Finite Element model. A 3D FE-model of two boreholes was used to evaluate the influence from ignition times, borehole distance and the amount of explosives. The results show that there indeed is a stress wave interaction effect and in this region there is an increase in fragmentation. However, the zone with increased fragmentation is considered to be small. The main effect on the fragmentation comes from the distance to the explosive charge and the amount of explosives.

Fracture Prediction of High Strength Steels with Ductile Fracture Criterion and Strain Dependent Model of Anisotropy

Kenji Takada (Honda R&D Co.)

Cockcroft-Latham fracture criterion was applied to predict the fracture of high strength steels. Marciniak-type biaxial stretching tests of the four grades of high strength steels were carried out to measure the material constant of Cockcroft-Latham fracture criterion. Furthermore, in order to improve the simulation accuracy, the local anisotropic parameters depending on the plastic strain (strain dependent model of anisotropy) were measured by Digital Image Reconstruction system and incorporated into Hill’s anisotropic yield condition by authors. To confirm the validity of Cockcroft-Latham fracture criterion, the uniaxial tensile tests based on JIS No.5 tensile specimen were performed. The force-displacement history and fracture happening strokes were predicted with high accuracy. Then, Cockcroft- Latham fracture criterion was applied to predict the failure of four types of spot welded joints. To simulate the local bending and warping deformations around the heat-affected zone, the discrete Kirchhoff triangle element was adapted. FEM results for four grades of high strength steels and four types of spot welded joints had good correlation with experimental ones.

Full Cycle Simulation, Virtual Tryout and Reality Check

Y. Hu, H. Hu, K. Li (Chrysler Group LLC)

Full Process Simulation is the Simulation on all line dies (all nominal design dies) with formability results and final springback results at the end of the line. Full Cycle Simulation is the Simulation on all line dies (all compensated dies) with formability and springback results on panels from each operation. The final operation panel must meet the GD&T tolerance requirements. The final surface quality must meet the NC programming quality requirements. The operation panels must meet nesting/fitting tolerance requirements. This full process full cycle simulations presented tremendous challenges to Chrysler stamping simulation engineers. In Chrysler, we did full process full cycle simulation on all of our in house stamping line dies, hoping that we will achieve significant improvement in our stamping dimensional quality. The reality is a vailable now to be shared with the stamping simulation community. In this presentation, a typical full cycle simulation flow is included to show how the virtual tryout is iteratively performed to achieve dimensional accuracy. CMM data are collected after real tryout and summary of the CMM data is included to show the reality check. Room for improvement is obvious after reviewing the reality check.

General Approach for Concrete Modeling: Impact on Reinforced Concrete

N. Van Dorsselaer, V. Lapoujade (DynAS+), G. Nahas, F. Tarallo, J.-M. Rambach (Institut de Radioprotection et de Sûreté Nucléaire)

In the world of Numerical Simulation, concrete modeling is one of the most complicated aspect engineers have to carry out. In fact, damage and failure occurring during concrete deformation are very complex processes difficult to reproduce with material models. And to make matters worse, material information available for concrete is often much reduced, leaving engineers profess structure performance without sufficient data. ®LS-DYNA has several material laws to model concrete behavior, and other modeling choices like hourglass treatment and boundary conditions are crucial. All these possibilities lead to a problem of “engineering dependence” for simulation results. This paper offers a general modeling approach for concrete modeling, where the main goal is to try to understand the ins and outs of different modeling to be able to have an overall view of a problem. This general modeling approach will be showed with the example of an impact on a reinforced concrete structure, setting up DoE study investigating material models, Boundary Conditions ®and Hourglass aspects, and using LS-OPT to perform Sensitivity Analysis and Optimizations assessing concrete behavior.

Golf Ball Impact: Material Characterization and Transient Simulation

X. Liu, D. Quinn, J. Bergström (Veryst Engineering)

®This paper presents an LS-DYNA simulation of the impact event when a golf club hits a golf ball. This is a challenging subject for finite element simulations because it is characterized by high strain rate behavior: the impact occurs within milliseconds and the golf ball experiences very large deformation during this period because of the ball’s polymeric shell and core. The simulation strategy emphasizes on accurate material characterization and realistic model construction. Specifically, the Parallel Network Model (PNM), an advanced nonlinear viscoelastic and strain rate dependent material model from Veryst Engineering’s PolyUMod TM library is calibrated with high-rate testing data to accurately capture the highly nonlinear behavior of the golf ball core material during impact. At the same time, a detailed finite element model of the golf ball is constructed with multiple layers of structure. The complex dimple pattern on the ball cover as well as the grooves on the golf club are modeled, both potentially important factors in impact response. The simulation is validated by comparing the deformed shape at maximum impact to that in real experiments. The paper then discusses two important issues in material characterization: selection of the right material model and the availability of reliable high-rate testing data. The PNM material model is compared to a linear viscoelastic (LVE) model to demonstrate its superiority.

Heat Transfer with Explicit SPH Method in LS-DYNA

J. Xu (LSTC)

In this paper, we introduce an explicit formalism to model heat conduction with Smoothed Particle Hydrodynamics method. With Taylor series approximation and SPH kernel interpolation, a simpler SPH discretization of the Laplace operator can be obtained for the thermal conduction equation. The formulation manifestly conserves thermal energy and is stable in the presence of small-scale temperature noise. This formalism allows us to evolve the thermal diffusion equation with an explicit time integration scheme along with the ordinary hydrodynamics. A series of simple test problems were used to demonstrate the robustness and accuracy of the method. Heat transfer with explicit SPH method can be coupled with structure for thermal stress and thermal structure coupling analysis.

Impact Analysis of an Innovative Shock Energy Absorber and its Applications in Improving Railroad Safety

X. Xin, B. K. Parida, A. K. Zaouk, N. Dana, S. K. Punwani

Short Fiber Reinforced Thermoplastics (SFRT) such as glass filled Polyamide 6 and 66 have been widely adopted as a metal replacement in a wide range of industries. The main advantage of using these materials is high strength to weight ratio, light weight, parts consolidation, easy manufacturability etc. Continuous Fiber Reinforced Thermoplastics (CFRT) are also gaining popularity because of its ability to achieve high directional stiffness/strength by tailoring the number of layers and angles. Applications which combine these two by over molding SFRT on CFRT inserts are still in its infancy. One of the hurdles is the lack of good CAE simulation capability for such applications. This paper describes the CAE tools that are developed using LS-DYNA to successfully model static and dynamic behavior of such parts. Material 58 in LS-DYNA is used for modeling the CFRT material while a User Defined Material Law models the SFRT material and they are coupled together through suitable contact definitions. Its applicability is verified through a number of examples varying from very simple to complex configurations

Impact and Detonation of COMP-B: An Example using the LS-DYNA EOS: Ignition and Growth of Reaction in High Explosives

L. E. Schwer (Schwer Engineering & Consulting Services)

The LS-DYNA keyword *EOS_IGNITION_AND_GROWTH_OF_REACTION_IN_HE provides the ability to model the ignition and growth of the reaction in high explosives via shock initiation from an impact or donor explosive. In this preliminary assessment effort, the experimental results for projectile impact on COMP-B of Almond and Murray (2006) are simulated. In addition to reporting their experimental results, the authors also reported numerical simulations results. Further, Urtiew et al. (2006) reported numerical simulation results for this set of experiments, using the same ignition and growth of the reaction in high explosives equation of state, Lee and Traver (1980,) implemented in LS-DYNA, but using a different explicit hydrocode. The experiments reported by Almond & Murray were for a blunt brass projectile impacting COMP-B without and with cover plates made from steel, aluminum and high density polyethylene. The critical impact speeds were in the range 950 to 1350 meters/second (2000 to 3000 miles/hour). Their numerical simulations used AUTODYN with the Lee and Tarver ignition and growth model. Similar experiments are reported by Lawrence et al. (2002 and 2006) which also included impact of COMP-B with steel cover plates by projectiles. This series of experiments considered different cover plate thicknesses, projectile nose shapes, and impact obliquity of the projectile. Critical impact speeds ranged from about 1050 to 1600 meters/second for the normal impact cases. The experimental configurations were simulated using the CTH (Hertel et al., 1993) code with the History Variable Reactive Burn (HVRB) explosive initiation model (Kerley, 1995). These experiments are not simulated in the present manuscript, but recommend to interested readers. In this manuscript the ignition and growth of the reaction in high explosives equation-of-state is introduced along with model parameters for COMP-B. Some comments are included in this section concerning alternative versions of these model parameters that are available in the literature. The manuscript focuses on the experimental data of Almond and Murray, their simulations results, the simulations results of Urtiew et al. and the present results, which make use of the relatively new LS-DYNA axisymmetric Multi-Material Arbitrary Eulerian Lagrange (MM-ALE) capability and thus serve as a post-test form of model validation.

Introduction of a New Function, (CONTROL_FORMING_SCRAP_FALL),in LS-DYNA & Its Applications in Scrap Fall Simulation

J. Gu, Y. Hu, X. Lu (Ford Motor Co.), X. Zhu, L. Zhang (LSTC)

In stamping plants, one of the most common defects is scrap fall failure, in which some of the trimmed scraps do not fall according to the designed chutes or intended path. The scrap fall failure can damage dies or/and panels and cause stamping production line shutdown, which could easily result in millions of dollars lost. This paper is focused on developing effective analytical tools to detect potential scrap fall failures in tool/die design stages. Scrap cutting/separation from its parent sheet metal is an important step in properly simulating the scrap falling sequence. There are several critical characteristics which need to be properly captured by an analytical method in order to “detect” scrap fall errors. First, many broken-off scraps carry the initial kinematics and dynamics from the upper moving trim steel through contact during the trim process. Second, the trimming action is not simultaneous along the trim curve even in most simple direct trims. In complex cases such as multiple direct trim processes or mixture of direct trim and cam trim, the sequence of the scrap separation is very different from one design to another. In addition to the scrap separation sequence and the initial kinematics and dynamics of the scrap, contact between scrap and low trim steel and post is another very critical factor to the trajectory of the scrap fall. Some efforts ([1], [2], and [3]) have been made to understand and detect the root causes of scrap fall issues. To our best knowledge, there are no methods available today which could consider all three above factors accurately. Therefore, simulation results from those methods might not yield the results observed in the stamping plants (refering to some cases presented in the paper). To capture above mentioned three characteristics in simulation of scrap fall, a new function, called CONTROL_FORMING_SCRAP_FALL in LS-DYNA, has been jointly developed by Ford and LSTC. In this paper, we will first reveal the basic parameters employed in the new function, and illustrate how they are used to simulate the scrap separation & falling with a few simple cases. Then, several complex examples will be shown to illustrate how the new function along w/ LS-DYNA existing capabilities to be able to simulate real trimming processes accurately (to capture above mentioned three key characteristics) and detect scrap fall failures.

Inverse Engineering and Preliminary Simulation of a Closed Profile Roll-forming Line

R. Perez-Santiago, A. Garcia, C. Sarmiento, R. Berlanga, M. Castellanos (Metalsa S.A. de C.V., ), M. Hernandez, P. Zambrano, O. Lopez (Universidad Autónoma de Nuevo León)

Roll-forming is a key technology among Metalsa ́s manufacturing capabilities. The Company’s technology group is conducting research oriented to support future engineering changes and the development of new technology variants. The initial objective of the project is the development of a reliable simulation of one complete roll-forming line using LS-DYNA®. The roll-forming tools were digitized using an optical scanner, converted to 3D parts and finally assembled into the complete forming line. This geometry served as base to generate a finite element model, which was entirely set-up using LS-PrePost®. As a first trial, the elasto-plastic behavior of the sheet strip was modeled utilizing generic material properties. In order to validate the analysis procedure, the production line was halted to allow geometry measurement of cross sections at different forming stations. This article describes the whole procedure utilized along with the comparison of the numeric and physical profiles obtained from the forming process. The numerical model yielded an accurate prediction of the deformed profile. This methodology is used on all virtual validation of new designs before commissioning equipment modification or purchasing.

Investigation of the Effects of the Coil Design on Electro-Magnetic Forming of a Thin-Walled Aluminum Tubular Material

H. Kim, P. L’Eplattenier (Edison Welding Institute), I. Caldichoury (Livermore Software Technology Corp.), J. Shang (American Trim)

In this study, a thin-walled aluminum tube was expanded using the electro-magnetic forming (EMF) process. Two different designs of coil were developed using EMF simulations with LS-DYNA’s electromagnetic module in version 980. The initial thickness of the aluminum tube was 0.254 mm (0.01 in.) and the material of the tube was Aluminum 3000 (Al-3000). This aluminum material is known to be difficult to expand more than a 9% expansion ratio at a given thickness. To evaluate the performance of the coil to expand the tube without failures, two different coils were designed and manufactured to have two different gaps between the coil and the workpiece. Preliminary simulations were conducted to determine the baseline design of the coil and after some preliminary EMF tests, the coil design was changed. Tubular samples were tested with two different coils and two different die sets (e.g., 10 and 12% expansion ratios). The EMF process was numerically modeled with LS-DYNA and the simulation results were compared with experiments.

Investigation of the Thermal Effects of Magnetic Pulse Forming using LS-DYNA

D. Chernikov, V. Gluschenkov (Samara State Aerospace University), P. L’Eplattenier (Livermore Software Technology Corp.)

This paper shows the results o f LS-DYNA simulations and experimental studies of various sources of thermal effects occurring during magnetic pulse forming: theJoule heating of the eddy currents, the work of plastic deformation and the collision with the die. The obtained results allow quantifying the thermal effects and their influence on the mechanism of high-speed deformation: the technological plasticity of the forming process, the level of residual stresses during assembly operations, the mechanism of formation of welded joints, and so forth.

Large Scale Normal Modes and PSD Analysis with Nastran and LS-DYNA

George Laird (Predictive Engineering)

From its conception in 1976, LS-DYNA has become a world-renowned analysis code used for the simulation of complex, real-world problems. Its power stems from the simple fact that it was written early on with an eye toward harnessing the resources of a variety of computational platforms. This strategy has allowed LS-DYNA to solve large scale, multi-physics problems that were impossible just a few years ago. LS-DYNA developers have also been extending its classically nonlinear, scalable solution sequences to that of large scale, linear dynamics problems using an MMP (Massive Parallel Processing) approach. Benchmark solutions are provided showing how LS-DYNA handles the basic linear normal modes analyses using standard finite elements (beams, plates, solids and rigid links) with a comparison to an industry standard Nastran solver. Results are then presented showing how LS-DYNA multi-CPU scaling decreases solution times for the power spectral density (PSD) analysis of large scale FEA models having millions of DOFs.

Limitations of Smeared Crack Models for Dynamic Analysis of Concrete

Y. S. Khoe, J. Weerheijm (TNO)

Performance prediction of concrete structures under explosive loadings or impact is an essential part of the research that is being performed within TNO. One of the current research topics is the explosive safety of tunnel structures. In the context of this research we evaluate the capabilities and limitations of concrete material models in LS-DYNA. The evaluation focuses on the CSCM concrete model and in particular the damage and failure characteristics of the model under single and sequential compression and tensile loading. Like many existing concrete models, the CSCM uses a smeared crack approach to model the reduction in strength of damaged concrete. It will be shown that the smeared crack approach has an intrinsic limit that places a restriction on the minimum size of an element. Furthermore, it is predicted that the built-in fracture energy regularization further aggravates the situation. The regularization algorithm tries to maintain a constant fracture energy. When elements have a size that is smaller than the limit size, the fracture energy of the total structure is increased which causes non-physical behavior. The predictions are confirmed by analyses on a tunnel structure as well as analyses on concrete cylinders under tension and compression. In contrast to the established minimum width, high dynamic loads or very local loads such as explosions or impact require a very fine mesh that can accurately describe the stress state and the shockwaves that are induced during these events. Using a reference load of a BLEVE explosion, the desired element size is derived and it will be shown that the desired element size is far smaller than the lower limit of element size. The consequences of the conflicting restrictions on the element size by the material model and the dynamic loading are illustrated by the tunnel structure analysis.

LS-DYNA 980: Recent Developments, Application Areas and Validation Process of the Incompressible Fluid Solver (ICFD) in LS-DYNA – Part 1

F. Del Pin, I. Caldichoury (LSTC)

LS-DYNA version 980 will include CFD solvers for both compressible and incompressible flows. The solvers may run as standalone CFD solvers where only fluid dynamics effects are studied or they could be coupled to the solid mechanics and thermal solvers of LS-DYNA to take full advantage of their capabilities in order to solve fluid-structure interaction (FSI) problems. This paper will focus on the Incompressible CFD solver in LS-DYNA (ICFD) and will be divided in two parts. Part one will present some advanced features of the solver as well some recent developments or improvements. Part two will provide some insight on the validation process that is currently under way in order to better understand the present capabilities and state of advancement of the solvers. Several test cases and results will be presented that will highlight several main features and potential industrial application domains of the solvers. The future steps and the challenges that remain will also be discussed.

LS-DYNA 980: Recent Developments, Application Areas and Validation Process of the Incompressible Fluid Solver (ICFD) in LS-DYNA – Part 2

I. Caldichoury, F. Del Pin (LSTC)

LS-DYNA version 980 will include CFD solvers for both compressible and incompressible flows. The solvers may run as standalone CFD solvers where only fluid dynamics effects are studied or they could be coupled to the solid mechanics and thermal solvers of LS-DYNA to take full advantage of their capabilities in order to solve fluid-structure interaction (FSI) problems. This paper will focus on the Incompressible CFD solver in LS-DYNA (ICFD) and will be divided in two parts. Part one will present some advanced features of the solver as well some recent developments or improvements. Part two will provide some insight on the validation process that is currently under way in order to better understand the present capabilities and state of advancement of the solvers. Several test cases and results will be presented that will highlight several main features and potential industrial application domains of the solvers. The future steps and the challenges that remain will also be discussed.

LS-DYNA ALE Nodal Coupling

H. Chen, J. Wang (LSTC)

LS-DYNA ALE solver has been used extensively on modeling fluid and gas behaviors. The accompanying FSI solver has been successfully applied on series of engineering problems such as tank sloshing, tire hydroplaning, bottle dropping, HE blasting, etc. The FSI solver, invoked by the *CONSTRAINED_LAGRANGE_IN_SOLID card, is intended to couple between ALE fluid elements and Lagrange structure segments. The LS-DYNA Discrete Elements recently developed has been successfully simulating sand undertaking explosion shockwaves from land mine detonations. In such models, sand is modeled as a group of discrete rigid particles. The pressure wave propagates in the sand through the penalty springs between discrete sand particles. The land mine is modeled by *MAT_HE using ALE multi-material element formulation. However, the existing FSI package can not handle the coupling between the ALE high explosives and sand particles as the FSI algorithm is segment based. This means that the Lagrange structure has to be a set of segments. The new nodal based coupling was developed so that the interaction between ALE fluids and node-based discrete elements could be resolved. The constraint-based coupling algorithm was implemented as the first phase of the development. The keyword is named *ALE_COUPLING_NODAL_CONSTRAINT. It has a similar input format and parameter list as the *CONSTRAINED_LAGRANGE_IN_SOLID card. Preliminary studies of method effectiveness have been done through an in-house land mine blast problem. The results agreed well with empirical data obtained through *LOAD_BLAST_ENHANCED.

LS-DYNA Analysis of a Sacrificial Wall Designed to Protect Mechanically Stabilized Earth Retaining Walls

A. Abu-Odeh (Texas Transportation Institute), K.-M. Kim (Samsung C&T Corp.)

Mechanically Stabilized Earth (MSE) retaining walls are used to provide roadway elevation for bridge approaches, underpass frontage roads and other roadway elevation applications. Vehicular traffic may exist on the high (fill) side of the MSE retaining wall, on the low side, or both sides. For traffic on the high side, a conventional traffic barrier might be placed on or near the top of the wall and mounted on a moment slab or a bridge deck. For traffic on the low side, a conventional traffic barrier might be installed adjacent to the wall or the wall itself may serve as the traffic barrier. Typical MSE wall panels are not designed to resist vehicle impacts. Therefore, structural damage to the wall panels and the earth fill would require complicated and expensive repairs. A simple reinforced concrete crash wall constructed in front of the MSE wall panels can significantly reduce damage to them. It may prove practical to implement such a design in order to reduce costly repair to the MSE wall structure. In this paper, LS-DYNA was used to model and analyze a sacrificial crash wall design to determine its effectiveness of protecting the MSE retaining wall. Based on the LS-DYNA simulations, a 0.2 m. thick crash wall is considered adequately designed to reduce damage to the MSE wall.

LS-DYNA Applications in Simulating Impact Tests of Nuclear Fuel Spacer Grids and Drop Tests of Fuel Shipping Packages

W. Zhao, Z. Karoutas, P. Evans, O. McRae (Westinghouse Electric Company, LLC)

Presented in the paper are two of our recent LS-DYNA applications in developing simulation models for: (1) impact tests of spacer grid – a key structural component of nuclear fuel, and (2) drop tests of shipping packages for fresh nuclear fuel, as described in the following, in that order. Resistance of nuclear fuel structure to impact loads during postulated seismic and/or loss-of-coolant accident (LOCA) events needs to be demonstrated to show that no excessive fuel structural deformation would occur so that the three criteria are met: (i) fuel rod fragmentation does not occur, (ii) control rod insertion is ensured, and (iii) the core coolable geometry is maintained. The demonstration is accomplished through comparison of prediction through full core simulation with the strengths of the various structural components of the fuel. The impact tests of the spacer grids provide one such strength. As the impact test of the spacer grids requires significant lead time and effort, capability to simulate the spacer grid behavior under testing conditions is of great interest. More importantly, it provides a powerful tool for design. To meet shipping package safety requirements for transporting fresh nuclear fuel assemblies, structural performance of the shipping package under hypothetical accident conditions must be evaluated and demonstrated to have adequate protection to the fuel assembly it transports. To efficiently evaluate design changes in the shipping package, a simplified finite element model for the shipping package and fuel assembly has been developed using LS- DYNA. The development and validation of the finite element model, along with a few design analysis examples to illustrate its usefulness are described.

LS-OPT Version 5: A New Flowchart-Based Interface for Process Simulation and Optimization

D. Björkevik, C. Belestam (DYNAmore Nordic), K. Witowski(DYNAmore GmbH), N. Stander (LSTC), T. Eggleston (Leawood)

®This paper provides an overview of the new flowchart-based interface for LS-OPT . The primary purpose of this development was to provide an interface for process simulation and optimization. An example of a manufacturing process is used to demonstrate problem setup and GUI functionality.

LS-TaSCTM Version 2

W. Roux (LSTC)

This paper gives an overview of LS-TaSC version 2.1, a topology optimization tool using LS-DYNA® for the analysis of nonlinear structural behavior. The focus is on its capabilities, current development directions, and integration into an industrial design environment. Examples of using the new developments such as dynamic load scaling are given.

Matching LS-DYNA Explicit, Implicit, Hybrid Technologies with SGI Architectures

O. Schreiber, T. DeVarco, S. Shaw (SGI), S. Bala (LSTC)

LSTC has now integrated Explicit, Implicit solver technologies into a single hybrid code base allowing seamless switching from large time steps transient dynamics to linear statics and normal modes analysis. There are multiple computer architectures available from SGI to run LS- DYNA. They can all run LSTC solvers using Shared Memory Parallelism (SMP), Distributed Memory Parallelism (DMP) and their combination (Hybrid Mode) as supported by LS-DYNA. Because computer resources requirements are different for Explicit and Implicit solvers, this paper will study how advanced SGI computer systems, ranging from multi-node Distributed Memory Processor clusters to Shared Memory Processor servers address the computer resources required and what tradeoffs are involved. The paper will also outline the specifications of running LS-DYNA jobs on Cyclone, SGI’s HPC cloud computing infrastructure using d3View. d3View is a simulation data management and visualization software that extends the use of HPC by performing simulation data extraction and analysis on the compute nodes.

Material Model Evaluation of a Composite Honeycomb Energy Absorber

K. E. Jackson (NASA Langley Research Center), E. L. Fasanella (National Institute of Aerospace), M. S. Annett (NASA Langley Research Center), M. A. Polanco (ATK Space Systems)

Abstract A study was conducted to evaluate four different material models in predicting the dynamic crushing response of solid-element-based models of a composite honeycomb energy absorber, designated the Deployable Energy Absorber (DEA). Dynamic crush tests of three DEA components were simulated using the nonlinear, explicit ®transient dynamic code, LS-DYNA . In addition, a full-scale crash test of an MD-500 helicopter, retrofitted with DEA blocks, was simulated. The four material models used to represent the DEA included: *MAT_CRUSHABLE_FOAM (Mat 63), *MAT_HONEYCOMB (Mat 26), *MAT_SIMPLIFIED_RUBBER/FOAM (Mat 181), and *MAT_TRANSVERSELY_ANISOTROPIC_CRUSHABLE_FOAM (Mat 142). Test-analysis calibration metrics included simple percentage error comparisons of initial peak acceleration, sustained crush stress, and peak compaction acceleration of the DEA components. In addition, the Roadside Safety Verification and Validation Program (RSVVP) was used to assess similarities and differences between the experimental and analytical curves for the full-scale crash test.

Modeling and Simulation of Bridge – Track – Train Systems at High Service Velocities with LS-DYNA

M. Klasztorny, P. Szurgott (Military University of Technology, Department of Mechanics and Applied Computer Science)

The paper develops a new methodology of FE modeling and simulation of the bridge – track – train systems at high service velocities with the use of selected CAE systems. The methodology is presented on the KNI 140070 viaduct with composite (steel – concrete) superstructure and 14.40 m span length, located on the Central Main Line, Poland. A ballasted track and two types of high speed trains have been modeled physically and numerically. The study includes German ICE-3 (InterCityExpress) train with classic bogies and Korean KTX (Korea Train eXpress close to French TGV) train with classic and Jacobs bogies. A methodology of the FE modeling and simulation of the bridge – track – moving train system is based on the following concept. The physical and numerical modeling of the viaduct – track – train system was performed with Altair HyperMesh® and LS-PrePost® software. The FE model of the bridge superstructure consisted of 4-node shell elements (main beams) and 8-node 48 DOF solid elements (RC platform). In order to simulate the moving train – track interaction, RAIL_TRACK and RAIL_TRAIN modules available in LS-DYNA system were used. Hughes-Liu beam elements were used for rail modeling whereas rail fastenings were simulated using one-dimensional discrete spring and damper elements. Carbodies, bogie frames and wheelsets were considered as rigid bodies and they were modeled using shell and beam elements. Cylindrical and revolute constrained joints and discrete springs and dampers were applied to connect components of the FE model of rail-vehicles. In the longitudinal direction, the FE mesh of the system is based on a 600 mm length module. DYNAMIC_RELAXATION is omitted via applying the static wheel loads increasing in the cosine shape in the 2-sec initial time interval. The quasi steady-state wave in the track is generated after the initial time interval. Dynamic response of the bridge – track – train system is registered in the form of displacement and acceleration time- histories at the design cross-sections as well as displacement and stress contours in reference to main steel beams.

Modeling Mine Blast with SPH

John M. H. Puryear, David J. Stevens (Protection Engineering Consultants), Ryan M. Alberson (University of Texas), Pat McMahon (Land Systems-MTVR/LVSR)

Accurately and efficiently modeling the loads applied to a vehicle by buried explosive (mine blast) is a persistent need. In this study, Smoothed Particle Hydrodynamics (SPH) was used to effectively model mine blast. The buried explosive and soil were modeled with SPH, while Lagrangian FEM elements were used for the vehicle plate. The approach was validated against a series of mine-blast experiments performed by the Ernst Mach Institute (Freiburg, Germany), in which the momentum applied to different geometries of steel plate suspended above the soil was measured. The momentum predicted from the SPH models ranged from 14% to 18% above the measured values, depending on plate geometry. Therefore, predictions from the SPH model corresponded closely with measured momentum but were conservative, as would be desired for designing vehicles. Furthermore, the SPH approach has the potential to be computationally efficient relative to an Arbitrary Lagrangian Eulerian (ALE) approach because an Eulerian solid mesh was not needed to model expansion of the explosive. This advantage is particularly important for models that include large vehicle targets, as an ALE approach would require large Eulerian meshes, significantly increasing the memory and execution time demands.

MPI Optimizations via MXM and FCA for Maximum Performance on LS-DYNA

G. Shainer, T. Liu, P. Lui, T. Wilde (Mellanox Technologies)

From concept to engineering, and from design to test and manufacturing, the automotive industr y relies on powerful virtual development solutions. CFD and crash simulations are performed in an effort to secure quality and accelerate the development process. The recent trends in cluster environments, such as multi-core CPUs, GPUs, cluster file systems and new interconnect speeds and offloading capabilities are changing the dynamics of clustered- based simulations. Software applications are being reshaped for higher parallelism and hardware configuration for solving the new emerging bottlenecks, in order to maintain high scalability and efficiency. In this paper we cover a new co-design architecture with hardware based accelerations and offloads for MPI collectives communications and how it affects LS-DYNA performance.

New Electrode Design for GEPI Shot to Test Curved Sample

G. Le Blanc, P. L’Eplattenier, I. Caldichoury (LSTC)

This study is relative to material behaviour characterization using the GEPI pulsed power device. First, the GEPI device will be briefly described. At the moment, only planar samples can be tested on GEPI. However, it is very attractive to test curved samples to comply with operational requirements. The adaptation of GEPI to curved sample would allow the characterization of material samples directly extracted from operational cylindrical structures. The GEPI performance is mostly based on high-precision electrode manufacturing. The feasibility study is conducted with the help of LS-DYNA magneto hydrodynamic modelling. The influence of geometrical defects is studied. To insure the success of this kind of test, the gap between electrodes must be tightly controlled. Electrodes must be machined with a tolerance lower than ten microns.

Numerical Simulation of Impact on Solid Rocket Motors

N. Couroneau-Mortreuil (DGA EM)

Weapons safety and vulnerability have become a major field of activities for DGA EM in the past decades. It is now a major actor, along with its state and industrial partners, for the safety evaluation and the qualification of all missiles to be fielded in the French armed forces. While test activities were presented in a previous paper [1], the present paper focuses on the simulation activities and the numerical tools developed to assess the vulnerability of solid rocket motors (SRMs) under impact loading. Finite element models for low or high velocity impact are both developed using LS-DYNA but the methods and constitutive models differ.

Oil-canning Simulation of Outer Panel and Influence of Stamping Results

Y. Hu (Chrysler Group LLC), J. Sun, X. Zhu (LSTC)

Abstract Oil-canning test is one of the most important measurements for outer panel stiffness. The methodology to analyze oil-canning of automotive outer panels using LS-DYNA® is studied and presented. Dynamic explicit method is used for stamping simulation and static implicit method is used for oil-canning simulation. The stamping results are carried over to oil-canning simulation. In one of the studies, displacement controlled indentation was applied to the panel and the contact force between the indenter and the panel was recorded. The Riks method was used in an alternative approach. Both approaches give the similar critical oil-canning resistance force which has good agreement with the measurement data. The influences of stamping results, particularly thickness reduction and stress status, on oil- canning resistance were also studied. Firstly, oil-canning simulations with stamping result vs. without stamping result were compared. It’s been found that stamping results could lower the oil-canning resistance force. The oil-canning analyses of panel with various levels of stamping results were also compared. Based on the research, the procedure for oil-canning simulation with LS-DYNA® was established to help optimize product and process designs satisfying with stiffness requirements.

On Mooney-Rivlin Constants for Elastomers

W. W. Feng, J. O. Hallquist (LSTC)

The Mooney-Rivlin constitutive equation for rubber is W= C1(I1-3)+C2(I2-3) where material constants C1 and C2 must be determined through tests. The constant C1 can be determined by uniaxial tension or compression tests; however, C2 cannot be determined accurately by uniaxial tension or compression tests. In order to determine C, biaxial tests must be performed. A biaxial test, inflation of a circular 2membrane, is presented in detail here for determining both C1 and C2 .

On Parameter Identification for the GISSMO Damage Model

J. Effelsberg, A. Haufe (DYNAmore GmbH), M. Feucht, F. Neukamm (Daimler AG), P. Du Bois (Consultant)

In order to improve predictiveness of crashworthiness simulations, great effort has been made regarding the treatment of crack formation and propagation. To achieve this, a consistent prediction of pre-damage, accumulated during manufacturing of a sheet-metal part, can help to improve accuracy. The constitutive models used for crash simulations are usually isotropic and based on the von Mises flow rule or the Gurson, Tvergaard & Needleman approach. For forming simulations, a more sophisticated and anisotropic description of yield loci – often based on the Hill or Barlat (1989) criteria – is considered important, which makes it necessary to use different constitutive models for both parts of the process chain. A damage model suitable to be used for both disciplines therefore has to be able to correctly predict damage regardless of the details of the constitutive model formulation. To fill this gap the damage model GISSMO (Generalized Incremental Stress-State dependent damage MOdel) has been developed at Daimler and DYNAmore (Neukamm et al. (2009), Haufe et al. (2010)). It combines proven features of damage and failure description available in crashworthiness calculations with the possibility of mapping various history data from sheet metal forming to final crash loading. The meanwhile carried out applications in everyday simulation work show excellent results based on carefully fitted material parameters. The present paper will focus on the parameter identification for the GISSMO damage model in crashworthiness simulation. A correct indication of damage and failure requires material data gained from several experimental tests. Starting from the treatment of the raw data, a procedure will be given, that shows how to calibrate the elastic-plastic behavior. In the following, a method is introduced which allows to capture damage and failure characteristics of a material. Step by step the determination and validation of particular GISSMO parameters will be discussed from a practical point of view. The objective is to give a complete overview of the calibration of a GISSMO material card.

On the Experiences of Adding a Complex User-Material-Model to LS-DYNA

G. S. Kalsi (AWE)

LSTC’s DYNA codes (both SMP and MPP) have been extensively used at AWE over a period of many years since they represent state-of-the art computational analysis capability which is required for simulating most of our complex problems. Occasionally there is a requirement to enhance existing code capabilities. An example is a need to improve the simulation of the constitutive behaviours exhibited by Polymer-Bonded Explosives (PBXs). Most polymer-bonded explosives are dual-phase composites consisting of an explosive crystalline filler material bonded in an elastically softer polymer matrix, which results in a very complex heterogeneous material. This heterogeneity, and the non-linear properties of the matrix, can lead to very complicated constitutive responses being generated when a PBX is loaded. PBXs possess unequal properties in tension and compression, and show marked strain-rate and temperature dependency. In the explosives arena, it is generally the energetic response of PBXs that forms the subject of in-depth studies, particularly from a viewpoint of safety assessments, e.g. accidental insults such as shock loading or fragment impact. The treatment of PBXs as structural, load bearing materials is less well investigated, for the primary purpose of a PBX is to act as an energetic source, rather than as a constructional material. However, there can be occasions when the structural response of a PBX needs to be well understood and controlled, and this new material model, known as GPM (Generic Polymer Material), was developed for this purpose. The GPM model is a damage-based material model that can simulate some of the complex constitutive responses displayed by PBXs, with a particular emphasis on creep and viscous response. This paper will briefly describe the formulation and application of this model, but the focus will be on the implementation of this material model into the LS-DYNA codes as a user-material-model. This was a non-trivial exercise and its implementation required a good deal of effort, together with some internal code changes by LSTC to their codes in order for the model to function correctly, since the user-material-model interface was found to be inadequate to accommodate a complex, non- linear material model’s requirements. Our experiences will be of potential benefit to other users who might find themselves in a similar situation.

OpenForm – A New Intuitive Graphical User Interface for Industrial Forming Simulation

C. Kaulich, M. Wenzlaff (GNS mbH)

Since the mid nineties sheet metal forming simulation has been widely used to take the uncertainty out of the die design process. When forming simulation was first introduced into the work of die designers the main focus was on the prediction of thinning, cracking and draw-in of the sheet metal. Later, the prediction of wrinkling, springback and surface defects became challenges finite element forming simulation packages had to cope with. While the prediction of thinning, cracking and material draw-in has now become a relatively easy task for numerical simulation, springback prediction and the detection of surface defects are still great challenges requiring advanced finite element simulation software and considerable expertise and experience in its application. More recently, hot forming simulation has added to the complexity of numerical simulation in the field of sheet metal forming. Since thermodynamical effects also have to be considered in the simulation of hot forming processes, even more experienced users are necessary to ensure that reasonable results are achieved. However, as a rule die designers are not numerical experts, and the use of more advanced finite element software remains a hurdle. Therefore, in the past, forming simulation software packages were assessed not so much by the complexity of their underlying physical models or the integrity of their numerical algorithms as they were for their user-friendliness and the efficiency with which input data could be generated even by inexperienced users. This is particularly reflected by the widespread use of so-called inverse or one step solvers. However, there seems to be a growing awareness among die designers that a rise in the quality of simulation results demands more advanced physical and mathematical models and therefore requires the use of finite element software that is, inevitably, more difficult to handle. As such, in a growing number of companies, more than one software package is used for sheet metal forming simulation. There is forming simulation software that is widely and efficiently deployed for the prediction of thinning and cracking but that fails to deliver good springback results. On the other hand, software that is used for more challenging tasks is often considered inefficient in everyday work. However, the use of different simulation software products increases the costs of numerical forming analysis considerably: not only because of additional licence fees but also because of costly training of staff members or even the engagement of new staff. While OEMs might still be able to cope with the problem of additional costs for software and training, for most of the smaller part suppliers an increase of CAE costs is prohibitive. To overcome this problem GNS has developed a new intuitive graphical user interface for industrial sheet metal forming simulation, called OpenForm. OpenForm is extremely easy to handle and can be used as a pre- and post-processor independently of a particular finite element forming simulation package. The software was designed to enable those who are not finite element experts to carry out multi step forming simulations with even complex multi purpose finite element codes.

Parametric Study for Evaluating Damageability of Automotive Radiator by Impacting Stones

S. Singh, M. Usman, J. Raver (Ford Motor Company)

The performance of automotive engines depends on the adequate heat rejection by radiator. The durability of radiator under all road conditions is an important consideration during the design and development stage, specifically protection of radiators from impacting road debris and stones. A parametric study was conducted to investigate the damageability of radiators by small stone impacts. In this paper, radiator design parameters are studied for damage protection caused by stone impacts. The strain in the radiator material caused by stone impacts has been used as the measure of damageability. The parameters considered for the study are the fin thickness, fin pitch, tube height, tube thickness, tube nose radius, tube depth, stone size and stone speed. The results show that strain is dependent on fin thickness, tube thickness, stone size and stone velocity. Also strain is insensitive to Tube nose radius, tube construction type, and tube depth.

Performance of LS-DYNA Concrete Constitutive Models

Y. Wu, J. E. Crawford, J. M. Magallanes (Karagozian & Case)

LS-DYNA provides several constitutive models for concrete. To provide some guidance in selecting a proper one for users who have limited experience on concrete, this paper reviews the background theory and evaluates the performance of three popular ones, namely, MAT072R3 (KCC), MAT084 (Winfrith), and MAT159 (CSCM). The basic performance of concrete constitutive models in capturing key concrete behaviors, such as post- peak softening, shear dilation, confinement effect, and strain rate enhancement, is examined through single element simulations including both uniaxial and triaxial load paths. Subsequent to this presentation, the models are applied in analyzing structures subjected to quasi-static, blast, and impact loads and the responses are compared with available test data in order to investigate their capability to predicting and reproducing actual structural responses.

Prediction of Failure Behaviors in Polymers Under Multiaxial Stress State

S. Hayashi (JSOL Corp.)

Polymers are used in an increasing number of automobile parts to improve occupant and pedestrian safety as well as reduce weight and cost. Under impact, these parts are designed to effectively absorb energy through large deformation and failure. Failure phenomena are very important to predict because structural strength is drastically changed or lost after failure occurs. In this study, puncture tests for polypropylene sheets were performed at various impact velocities and frictions, and failure locations and timings in the sheets were investigated. Puncture tests generate a multiple stress state in the sheets and this heavily influences the failure behavior of the sheet material. CAE crash simulations using LS- DYNA were conducted to successfully predict deformation and failure behavior under a multiaxial stress state.

Random Vibration Fatigue Analysis with LS-DYNA

A. Ringeval (CIMES), Y. Huang (LSTC)

Fatigue damage assessment for components under random cyclic loading is an important concern in engineering. A new feature of random vibration fatigue analysis has been implemented to LS-DYNA, to perform the structural fatigue analysis in a random vibration environment. This feature computes cumulative damage ratio and expected fatigue life for structures, based on the Palmgren-Miner’s rule of cumulative damage ratio and material’s S-N fatigue curve. A series of fatigue analysis methods have been implemented. They include the Steinberg’s three band method, Dirlik method, Narrow band method, Wirsching method, Chaudhury and Dover method, Tunna method and Hancock method. Brief introduction of the analysis methods is provided. To facilitate post-processing of the fatigue analysis, a new binary plot file d3ftg has been implemented in LS-DYNA. This binary plot file provides fatigue analysis information including cumulative damage ratio, expected life, zero- crossing frequency, peak-crossing frequency and irregularity factor for the structure, based on the stress index adopted in the analysis and the load period. This file is accessible to LS-PREPOST. Several examples are given to demonstrate the effectiveness of the random vibration fatigue analysis feature with LS-DYNA. Some preliminary discussions on the different fatigue analysis methods are included.

Recent advancements in LS-DYNA Pre-processing for Crash Simulation

Lambros Rorris, Athanasios Lioras, Yianni Kolokythas (BETA CAE Systems SA)

The increasingly demanding and complex requirements in Crash Analysis, call for continuous and innovative software development. BETA CAE Systems in an effort to meet and exceed the requirements of the industry is introducing new cutting edge technologies, in the pre-processing area with ANSA. This paper presents these new technologies. As CAE comes to maturity the challenges and requirements for the CAE preprocessing software also evolve. Preprocessing should not be a manual job anymore. Automated processes and data handling is crucial for solving complex real world problems. In the area of Crash and Safety analysis we can find many such examples. FMVSS 201 226, and EURO NCAP pedestrian testing protocols demand highly specialized tools that can perform complex positioning operations that until now could only be done manually. With the introduction of the newer ANSA versions, all these operations can be performed, by the software, in a totally automated way. Automating such procedures leads to the next step. This is performing robustness and sensitivity analyses to gain confidence of the analysis results and deeper understanding of the designs and models. The advanced scripting environment along with the pre and post processing facilities provided by our products has been used to demonstrate such a use.

Recent Developments and Roadmap Part 5: ALE, DEM, SPH, Particle

Dr. Jason Wang (LSTC)

Recent Developments: ALE, DEM, SPH, Particle

Recent Developments and Roadmap Part 1: LS-PrePost

Mr. Philip Ho (LSTC)

Recent Developments: LS-PrePost

Recent Developments and Roadmap Part 2: Dummy Models

Dr. Christoph Maurath (LSTC)

Recent Developments: Dummy Models

Recent Developments and Roadmap Part 4: Electromagnetics

Dr. Pierre L’Eplattenier (LSTC)

Recent Developments: Electromagnetics

Recent Developments and Roadmap – Conclusions

Dr. John O. Hallquist (LSTC)


Recent Developments and Roadmap Part 3: Incompressible CFD

Dr. Facundo Del Pin (LSTC)

Recent Developments: Incompressible CFD

Recent Developments and Roadmap Part 0: Introduction

Dr. John O. Hallquist (LSTC)


Recent Developments in Mechanical Characterization (Deformation and Failure) of Materials

A. Gilat, J. D. Seidt (Ohio State University)

Several new testing methods that have been recently developed for mechanical characterization (deformation and failure) of materials are presented. The data from these tests is used for the development and calibration of ®material models (constitutive relations) in LS-DYNA . The first method involves the use of Digital Image Correlation (DIC) in tests that are used for generating data needed for using the MAT224 model. In these test specimens with different geometries are loaded and DIC is used for measuring full field strains and relative displacements. The second testing configuration is a shear test for sheet metals. The experiment is done by using a flat notched specimen in a tensile apparatus. The shear strain is measured by using DIC within and on the boundary of the notch. The third development is a high strain rate tensile testing technique for Kevlar cloth and Kevlar yarn in a tensile Split Hopkinson Bar (SHB) apparatus. The Kevlar cloth/yarn is attached to the bars by specially designed adaptors that keep the impedance constant. In addition to the traditional method of determining the specimen’s stress and strain from the recorded waves in the bars the strain is also measured with DIC. The fourth development is an apparatus for testing at intermediate strain rates in compression. In this -1 -1apparatus the specimen can be deformed at strain rates ranging from 20 s to 200 s . The apparatus is a combination of hydraulic actuator and a compression SHB. The stress in the specimen is determined from the stress wave in a very long (40 m) transmitter bar and the strain and strain rate is determined by using DIC. The results show very clean (no ringing) stress strain curves

Recent Research and Developments of LS-DYNA’s User Subroutine in JSTAMP/NV

T. Amaishi, N. Ma, Y. Umezu (JSOL Corporation)

Sheet metal forming simulation has been widely used in die design process, in order to make lightweight products ®and shorten production lead time. JSOL Corporation has been developing JSTAMP/NV since 1996 and continuously supplying the best stamping simulation environment for users. One of the most competitive advantages of JSTAMP/NV is its accuracy on the evaluation of formability when using explicit and implicit solutions in LS- ®DYNA . In this paper, new material model and user subroutine of anisotropic plasticity with temperature dependency were developed for hot forming simulation by authors. Using the developed material model, the formability of deep drawing of a magnesium alloy was estimated with the high accuracy compared with experimental results.

Retrofitting of Reinforced Concrete Beam-Column via Steel Jackets against Close-in Detonation

S. H. Tan, J. K. Poon, R. Chan, D. Chng (Ministry of Home Affairs)

This paper presents results from simulation, in comparison to findings from full-scale blast trials of Reinforced Concrete Beam-Column test specimens. 2 numerical approaches were adopted. First method was a 2-stage approach which involved applying segment pressure loadings, derived from Computational Fluid Dynamics (CFD) ®calculations, on LS-DYNA Lagrangian models to predict structural response. Second method was the use of *Load_Blast_Enhanced keyword to couple empirical blast loads to air domain in Arbitrary Lagrangian-Euler (ALE) environment for direct LS-DYNA Fluid-Structure Interaction (FSI) computations. Grid Convergence Index (GCI) principles were used to check adequacy of mesh refinement studies.

Rollover Simulations for Vehicles using Deformable Road Surfaces

T. Palmer (ETA), B. Honken (ETA), C. Chou (Wayne State University)

Vehicle Rollover simulations have been performed using LS-DYNA to predict both the vehicle dynamics and structural performance. However, these simulations do not consider a deformable road surface, affecting both the propensity of the vehicle to achieve a condition which will initiate a roll over or the effect of that surface to impart or mitigate damage to the structure. This study will highlight the capabilities of LS-DYNA for the simulation of deformable road surfaces as applied to rollover events.

Script for Automated One Step Forming Analysis using LS-DYNA and LS-PrePost

A. Nair, D. Bhalsod (LSTC)

Mapping of metal forming data on metal parts for Crash Simulations helps to simulate the widely known effect of stiffer physical properties due to manufacturing processes. LS-Dyna® has enhanced the previously available capability to simulate one step analysis on metal parts and can use the existing finite element geometry taken from a full vehicle model. This method is quicker than running an incremental analysis for hundreds of parts which would take a considerable amount of time. This analysis is done manually one part at a time along with some necessary preprocessing. For this process to be useful in a full vehicle crash analysis, where multiple parts have metal forming data mapped, an automated process with minimal user interaction in model set up is required. A script was written to facilitate this method. This paper discusses the algorithm used to automate the set up process.

Simulating the Joining of Composite Materials by Electromagnetic Induction

M. Duhovic, L. Moser, P. Mitschang, M. Maier (Institut für Verbundwerkstoffe GmbH), I. Caldichoury, P. L’Eplattenier (LSTC)

The development of the electromagnetism module in LS-DYNA (980 solver) was in the past primarily driven by the need for Electromagnetic Metal Forming (EMF) simulation capabilities. As the module matures, new applications in particular in the field of induction heating for thermoplastic composite welding/joining have appeared, providing a crucial simulation tool for composite manufacturing processes utilizing this technology. In this work, induction heating characterization tests involving static plate specimens using different induction heating processing parameters have been performed and then simulated. Finite element models have been built in both LS-DYNA and COMSOL and the results and capabilities of both software codes are discussed and compared.

Simulation and Test Validation of Windscreen Subject to Pedestrian Head Impact

Q. Liu, J. Liu, Q. Miao, D. Wang, X. Tang (SAIC Motor Technical Center)

Pedestrian head impact with windscreen is one of the major causes for pedestrian severe injury or fatality. A FE model is established with shell and solid elements representing different layers of a laminated windscreen. Major strain criterion is used to deal with the failure of windscreen. Simulation results are validated by Euro NCAP pedestrian head-to-windscreen impact tests. The results show that the FE modeling of windscreen can effectively predict the pedestrian head injury and the failure pattern of the windscreen. This method can be an effective tool for vehicle pedestrian safety evaluation and development.

Simulation for Forming and Performance Evaluation of Structures Developed Based on the Concept of “ORIGAMI Engineering”

Sunao Tokura (Tokura Simulation Research Corp.)

The “origami” is known as one of traditional Japanese craftwork. Origami is a technique of paper folding in which various complex shapes of birds, flowers and so on can be made from a simple sheet of paper. Origami is also considered as a technique to produce light weight three dimensional structures from two dimensional material. And the 3D structures of origami can be foldable and/or expandable. Recently origami engineering inspired by traditional origami has been advocated by some researchers. Although several excellent structures have been studied ideally and mathematically so far, from a viewpoint of engineering, formability of the origami structure is a very important engineering issue practically even if the structure has excessively elegant shape. There are two major origami structures, i.e., the “octet-truss core panel (shortly truss core panel)” and the “reversed spiral origami tube”. In this paper the formability, strength and crash performance of these origami structures are discussed. The explicit FE code LS- DYNA® is the main solver of these problems. The press forming simulation software JSTAMP is used for formability assessment and the optimization software LS-OPT® is used to study crash performance.

Simulation of a Railgun: A Contribution to the Validation of the Electromagnetism Module in LS-DYNA v980

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

A railgun is an electrical gun using electromagnetic forces in order to accelerate and launch projectiles at several times the speed of sound. Railguns have long belonged to the science-fiction world or existed as experimental and demonstrator technology. However in recent years, the U.S Navy has shown an increased interest for Railguns as they offer the potential for reduced logistics and firing power. The purpose of this paper is to simulate a railgun model using the Electromagnetism solver in LS-DYNA, to compare results with existing analytical models and to show how LS-DYNA may help to improve such existing models.

Simulation of Ball Impact on Composite Plate with PP+30% LGF

T. Sakakibara, R. Akita, Y. Ohnishi (ITOCHU Techno-Solutions Corp.), S. Kijima, Y. Kanki (UES Software Asia Inc.), M. Seto (Kanazawa Institute of Technology), K. Suda, K. Yamakawa, Y. Ayano (Toray Eng. Co.)

The failure prediction of the long glass-fiber (LGF) reinforced resin is difficult because of the complicated fiber orientation compare to the short fiber. In order to establish a simulation procedure to represent the failure behavior of the LGF reinforced resin, we have carried out simulations of ball impact on the composite plate with ®polypropylene and 30% LGF using LS-DYNA coupled to DIGIMAT. The fiber orientation was calculated by the mold flow code 3D TIMON and the composite material properties and failure criterion were estimated and verified by DIGIMAT based on mean-field homogenization. The stiffness reduction and fracture progress in the simulation are represented by the First Pseudo Grain Failure model (FPGF). The numerical results of the impact simulation are discussed through comparing the experimental results.

Simulation of Check Valve Flapper-Housing Impact Using LS-DYNA Fluid-Structure Interaction

S. Hu (Hamilton Sundstrand Corporation)

The flapper of a check valve in the aircraft air management system may hit the housing with a very high speed due to the sudden pressure differential caused by duct rupture, which may lead to the damage of the flapper. This event ®can be simulated using transient dynamic finite element tool, such as LS-DYNA . However, the flapper impact speed usually is unknown. The current study is focused on solving for the impact speed with the developed Fluid-Structure Interaction technology in LS-DYNA, using Arbitrary Lagrangian-Eulerian (ALE) formulation. With the aid of a concept of “Source”, “Moving Air”, and “Sink” for the ALE model, which represent the conditions of constant cabin pressure, airflow interacting with the flapper, and non-pressurized ambient environment, respectively, the proposed method successfully simulated the check valve fluid-structure interaction behavior. The predicted impact speed has an excellent agreement with the test. The developed methodology is accurate, easy to use, and applicable to all check valves regardless of size, material, and pressure differential.

Simulation of Impact Proof Testing of Electronic Sub-Systems

P. Glance (Naval Air Warfare Center Weapons Division)

The purpose of this paper is to document the development of a new simulation tool which is being employed to simulate the deceleration vs. time pulse imposed on electronic systems during impact tests as shown in Figure 1. The simulation tool has also been employed to predict the stress, strain, fracture, and structural failure of electronic sub-systems. Cannon tests and rocket propelled sled tests are the standard test methods employed to “proof test” the successful operation of hardened electronic systems under extreme operating conditions. The proof test consists of placing the electronic sub system into a generic steel carrier and launching into concrete or soil blocks. The peak deceleration is determined by the lower stiffness material which is the concrete / soil. Previous LS-DYNA and “Hydrodynamic” code simulations of these tests required super computers, expert consultants, extensive computer run times, and relatively high cost. The new LS-DYNA concrete material model (*MAT 159) with eroding contact option, allows rapid simulation of impact penetration and by-passes the need for excessive computer run times often required for Arbitrary Lagrangian Eulerian (ALE) LS-DYNA models and equation of state (EOS) material models. This paper describes a simple, robust, and fast running, LS-DYNA application for simulating high g cannon and sled tests. This application will run on a Dell workstation employing one Intel processor and accurately predicts; deceleration, stress, strain, fracture, and overall deformation and damage of electronic systems

Simulation of Loads from Drifting Ice Sheets on Offshore Structures

D. Hilding, J. Forsberg (DYNAmore Nordic AB), A. Gürtner (Statoil ASA)

In later years, there has been an increasing amount of work published regarding simulation of ice action on structures using finite element models of the ice. Here we will present results from a method development project aimed at evaluating the feasi- bility of full scale simulation of ice action from drifting ice sheets on offshore structures. The used methodology is presented including new developments, the implementation in LS-DYNA®, and results from a benchmark study where simulation results are compared with full scale meas- urements of ice forces. The methodology is based on using the cohesive element method for modeling the ice fracture in conjunction with an ad hoc homogenization method developed by the authors. The homogen- ization method is used to capture sub element size cracks in a cost efficient manner.

Simulation of Reinforced Concrete Structure under Impact Loading using Meshfree Cohesive Failure Approach

H. S. Lu, J. Y. Zhao (Shanghai Hengstar Technology Co), X. W. Wang, X. Lei (Shanghai Nuclear Engineering Research and Design Institute), C. T. Wu (LSTC), Y. C. Wu (Karagozian & Case)

Reliable numerical simulation of failure is important for the design and planning of new solids and structures, as well as for the safety assessment of existing ones. In the past two decades, gradient and non-local models for regularizing loss of ellipticity due to material failure using non-standard finite element method and more recently the meshfree method have been the topic of considerable research. Alternatively, discontinuous partition of unity enrichments and meshfree visibility concepts were proposed and used in finite element method (also called extended finite element method – XFEM) and meshfree method to model cracks. Due to the fact that the description of crack plane in XFEM using level set method still presents several difficulties in the three-dimensional simulation of solids, the meshfree method using visibility concept is tested for the solid failure analysis of reinforced concrete structure under impact loading. The current method incorporates the discontinuous field into the generalized meshfree approximation [1] by the introduction of visibility approach [2]. To determine the onset of fracture and subsequently the crack propagation, a stress-based initial-rigid cohesive cracking model was developed for the brittle and semi-brittle materials. After the insertion of new crack, the state variables are interpolated and transferred to the new stress point using second-order meshfree approximation [3]. To integrate the discrete equations involving the crack plane, the strain smoothing algorithm developed in SCNI method [4] was adopted in this development. A typical reinforced concrete structure under impact loading failure involving multi-cracks is modeled using the developed method and results are presented.

Simulation of Warm Forming of Aluminium 5754 for Automotive Panels

T. Dutton (Dutton Simulation Ltd), M. Mohamed, J. Lin (Imperial College London)

The work described in this paper has been carried out as part of a project investigating implementation of an innovative metal forming process into the automotive industry to produce lightweight, high accuracy, complex-shaped automotive Aluminium panel components using one operation. The project, lasting three years, is a collaboration between industrial and academic partners lead by a Premium Automotive Manufacturer with funding from the UK Technology Strategy Board. As part of the objective to not only investigate but also industrialize the technology, finite element simulation methods have been included in the scope of work. This paper will report on the extensive program of material characterization carried out by the academic partner Imperial College London in order to develop and correlate the simulation models. Focus is on the sensitivity of key material properties to both temperature and forming rate, as well as the variation of friction with temperature for various lubricants. The Simulation method has been developed on two fronts. The initial approach takes an existing model and applies it to warm forming processes, chiefly under isothermal conditions; the required input parameters will be discussed. In parallel, a new and more comprehensive user- defined material model incorporating not only thermal and strain rate parameters but also a continuum damage mechanics (CDM) approach has been developed at Imperial College. The capability of the model to predict Forming Limit Curve measurements of 5754 aluminium sheet at various temperatures will be shown. The project is now in its final phase of forming trials using a prototype tool that has been manufactured based on the simulation work to date.

Simulation Technique for Pre-forming of AHSS Edge Stretching

X. Chen (United States Steel Automotive Center), J. Sun, X. Zhu (LSTC)

Edge cracking in advanced high strength steels (AHSS) is one of the main failure modes in many sheet metal stamping processes. Pre-forming into a wave (or scallop) shape at the edge is a common technique used to gain material at high edge stretch regions in preparation for the subsequent edge stretch processes. The accurate simulation of this multi-stage forming process remains a challenging task since these edges experience complicated forming processes including bending, unbending, and stretching deformations. In this study, a simulation variable study is performed and the effect of various material models, hardening rules and solvers on the simulation results is also investigated. A simulation technique is established for this multi-stage forming process. Simulation results are compared to experimental data and reasonable agreement is achieved. Different failure criteria are also evaluated and discussed for use in this type of application.

Simulations of Axial Impact of Composite Structures with a Coupled Damage-Plasticity Model

X. Xiao (Michigan State University)

Under axial impact, a composite structure can split into pieces at the crush front while maintaining an apparent structural integrity in its uncrushed portion. In this way, the structure is capable of sustaining large deformation under a sufficiently high load. To simulate this behavior, the constitutive model must be able to describe the response of a substantially damaged composite under dynamic loading. The constitutive behavior beyond the peak loading is not well represented in common composite constitutive models. This paper presents the recent development of a coupled damage-plasticity model for composites and its applications in crush simulations.

Studies on the Efficiency of LS-DYNA in Sheet Metal Stamping for Feasibility and Formability Analyses

C. Roman (General Motor Company), J. Sun (LSTC), G. Hsiung (General Motor Company), X. Zhu (LSTC)

Feasibility and formability analyses serve different purposes in automotive panel designing. The turnaround cycle of forming simulation is essential, since the designs change very frequently in early stage of vehicle development. The goal of this study is to evaluate the feasibility by using LS-DYNA ® as an alternative to Autoform for both early product evaluations, as well as more detailed formability analysis in GM’s production developments. Targeting the requirements of feasibility and formability analyses, the key techniques of using LS-DYNA® in sheet metal forming simulations are systematically studied, such as element formulation, material model, adaptive meshing, and mass scaling, etc. The study shows that the simulation time is able to be significantly reduced by choosing proper combination of the numerical parameters, while the accuracy of the results remains satisfying. In this study, 21 production developments by Autoform were translated to LS-DYNA so that they could be run using the LS-DYNA solver on GM’s HPC server. These 21 parts encapsulate all three engineering modules and contain a wide variety of parts. Given the computational resources available in GM, the simulation time and results by LS-DYNA are competitively comparable to Autoform.

Techniques for Modeling Torque Transfer between Concentric Cylindrical Components

Richard Tejeda (InForm Product Development, Inc.)

Finite elements that use a piecewise linear approximation of geometry are perfectly adequate for modeling cylindrical components such as shafts and hubs in many applications. However, linear elements present a challenge to the assessment of contact interfaces between curved surfaces, namely that faceted surfaces have peaks and valleys that can interlock with each other. A good example is when torque is transferred between a shaft and a hub via a key, collar, pin, or some other means. In this case, it can be difficult or impossible to control how the applied torque is shared between the interlocking mesh and the intended torque transfer device. If the goal of the analysis is to determine the strength of the actual torque transfer features (e.g., a keyway or spline), then it is critical to apply the correct load to them by eliminating or at least minimizing mesh interlocking. This paper discusses various strategies for circumventing the mesh interlocking problem.

Tensile and Shear Element Erosion in Metal Foams

S. Szyniszewski (Dept. of Civil Eng., Johns Hopkins University), B. Smith, S. Arwade (Dept. of Civil and Env. Eng., University of Massachusetts), J. Hajjar (Dept. of Civil and Env. Eng., Northeastern University), B. Schafer (Dept. of Civil Eng., Johns Hopkins University)

The goal of this paper is to simulate fracture observed in tensile and shear tests of steel foam specimens. Deshpande-Fleck plasticity was employed for numerical modeling, and calibrated against compressive and tensile experiments. Steel foam has plastic yield stress, and can deform under compressive load beyond 60% engineering strain. Unlike in compression, steel foam fractures at a small strain in tension. Weak tensile behavior is captured with the element deletion. In order to enhance the realism of the simulated fracture patterns, yield stress, Young modulus, and failure strain were randomly varied between all elements. Unfortunately, default material erosion produced shear fracture patterns significantly different from the experiments. Thus, alternative element erosion was postulated, and it was based on the maximum principal strain. The proposed criterion was shown to give adequate agreement with the experimental results. Tensile and shear fracture modeling of steel foams may benefit from inclusion of spatial variability of material properties. The proposed principal strain based element erosion performed better than the principal stress fracture cut-off.

The ACP Process Applied to the FutureSteelVehicle: The Future of Product Design and Development

A. Farahani (ETA Inc.), J. R. Shaw (United States Steel Corporation)

WorldAutoSteel completed FutureSteelVehicle program (FSV) in May of 2011 with the aim to help automakers optimize steel body structures for electrified vehicles. The program objective was to develop detailed design concepts and fully optimize a radically different body structure for a compact Battery Electric Vehicle (BEV) in production in the 2015-2020 timeframe. This paper will provide an overview of the development of an multi- disciplined optimization product design methodology and how it was developed in concert with the WorldAutoSteel FutureSteelVehicle (FSV) program. This optimization technology combined with the advanced high strength steels and the design flexibility of these products enabled 35% BIW mass reduction, exceeding the mass reduction o previous steel programs. This methodology is being made commercially available through the proprietary Accelerated Concept to Product (ACP) ProcessTM. The ACP ProcessTM is a performance-driven, holistic product design development method, which is based on design optimization. ACP incorporates the use of multiple CAE tools (i.e; LS-DYNA) in a systematic process to generate the optimal design solution. The ACP ProcessTM is a methodology that provides solutions, which address the challenges facing the modern product development environment. It achieves this by synchronizing the individual facets of the product development process, resulting in an overall reduction in development costs and time to market. Material selection and utilization, product performance requirements and manufacturing and assembly processes are all considered as early as possible in the design cycle. The resulting design offers a robust and highly efficient solution; which when combined with the strength and design flexibility of Advanced High Strength Steel (AHSS) or other materials; facilitates significant mass reduction for the final design.

The new Topcrunch Benchmark Data CAR2CAR for LS-DYNA MPP971R5

M. Makino (Dynapower Corp.)

CAR2CAR-ver10 has been used as benchmark data of Topcrunch since 2006. By the enhancement of tied contact in MPP971R5, this data do not work, since the slave nodes of constrained tied contact are released when master segments contain rigid body. CAR2CAR is revised to work for MPP971R5. This paper summarizes tied contact, then explain how to modify the data.

Topology Optimization for Crash

K. Witowski, A Erhart, P. Schumacher, H. Müllerschön (DYNAmore GmbH)

This paper is contributed to the topology optimization of structures under highly nonlinear dynamic loading, e.g. crash. We present our experiences with two software tools: LS-TaSCTM (developed by LSTC, available since 2009, the first version was named LS-OPT/TopologyTM) and Genesis-ESL ® (developed by VR&D) and highlight the possible application areas, capabilities and limitations of the implementations. LS-TaSC nonlinear topology optimization with LS-DYNA can be applied to nonlinear static and dynamic problems. The underlying method is “Hybrid Cellular Automata” (HCA) which is a heuristic, gradient-free approach. The objective is to obtain a structure with uniform internal energy density subject to a given mass fraction. The basic idea of the “Equivalent Static Load”- Method (ESL) is, to divide the original nonlinear dynamic optimization problem into an iterative “linear optimization ↔ nonlinear analysis” process with linear static multiple loading cases for the optimization. The iterative optimization ↔ analysis process is to capture the nonlinearities and the multiple loading cases reflect the nonlinear dynamic deformation progress of the structure within the optimization.

Update on the Electromagnetism Module in LS-DYNA

P. L’Eplattenier, I. Caldichoury (Livermore Software Technology Corp.)

An electromagnetism module is being developed in LS-DYNA version 980 for coupled mechanical/thermal/electromagnetic simulations. The physics, numerical methods and capabilities of this module will be introduced. Some examples of industrial applications will be presented. These include magnetic metal forming and welding in different configurations, high pressure generation for equation of state studies and material characterization, induction heating, resistive heating, electromagnetic launchers, magnetic levitation and so forth.

Updates to LSTC’s LS-DYNA Anthropomorphic Models

C. Maurath, S. Guha (LSTC)

This paper shows the progress of LSTC’s LS-DYNA crash test dummy model development effort. It is an update to the presentation and paper “Overview of LSTC’s LS-DYNA ® Anthropomorphic Models”, presented at the 11th International LS-DYNA Users Conference. Updates and details of all released models are presented. The development status of models currently under development is addressed. Outlook to future models is given.

Use of the Combustion and Stochastic Water Spray Modules in the LS-DYNA Compressible Flow Solver

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

Recent development of the chemistry and stochastic water spray modules in the CESE LS-DYNA® compressible flow solver will be reported in this presentation. For the chemistry, detailed descriptions about CHEMKIN input files including the thermodynamics and transport data files will be presented. How to construct of the keyword files is also demonstrated for the various chemically reactive flows. Limitations of the current chemistry module and future development with reduced chemistry will be discussed. For the stochastic water spray, the concept of the stochastic particle, breakup models such as the TAB and KH&RT hybrid models, and collision models are described and corresponding keyword setups are explained with water spray flows. Limitation and current developments including fuel vaporization models will be also presented.

Using Cloud Computing to Reduce Simulation Turnaround Times and Increase Simulation Throughput

S. Yang (IMMA), A. Dittmer (Pengium Computing)

FEA simulation throughput directly impacts productivity in any engineering organization that uses computational simulations in their design workflows. In the typically iterative design process, higher simulation throughput and shorter turnaround times allow for exploring more design parameters which in turn results in product designs that are closer to the elusive ‘optimal’ solution. On the other hand, the limited availability of computational resources often limits simulation throughput and increases the turnaround time for simulations resulting in less optimal solutions or delayed schedules. Offering scalability and a pay-as-you go payment model cloud computing promises a way out of this dilemma. This paper provides an overview of Penguin Computing’s public cloud infrastructure Penguin on Demand (POD) including a discussion of POD’s security model. The paper then discusses how IMMI, a provider of advanced safety systems reduced job turnaround time and increased job throughput of LS-DYNA simulations, using a hybrid model of in-house compute resources and Penguin Computing’s public cloud offering Penguin Computing on Demand (POD). Specific examples such as design of IMMI’s FlexSeat, a three point belted seat for school buses, frontal crashing simulation of fire trucks as well as respective benchmark data will be provided.

Validation and Material Modeling of Polymers by Employing MAT_SAMP-1

K. Takekoshi, K. Niwa (Terrabyte Co.)

We have developed a method to determine plastic Poisson’s ratio and its corresponding stress – strain curves, where newly redefined true stress expression including elastic and plastic Poisson’s ratios is employed. The plastic Poisson’s ratio is used to predict permanent volumetric deformation which is one of the mechanical characters associated with crazing. Although the crazing is one of the most important issues to be tackled in analysis, methods to determine the plastic Poisson’s ratio and its corresponding data have not been discussed sufficiently in previous papers. Thus we show and discuss how we determine and validate these data. Additionally, in order to complement the method, we provide two techniques to utilize MLYS (Multi-Linear Yield Surface) and to evaluate damage property. We show MLYS could make analysis incorporating isochoric plasticity in compressive state stable. Furthermore we show that these methods are valid and useful through the numerical results.

Validation of LS-DYNA MMALE with Blast Experiments

Y. Huang, M. R. Willford (Arup), L. E. Schwer (Schwer Engineering & Consulting Services)

The general multi-material arbitrary Lagrangian-Eulerian (MMALE) solver is available in the finite element ®analysis software LS-DYNA . In the context of blast simulation, this solution approach involves explicit modeling of the explosive, the blast transmission media and the structure subjected to the blast within the MMALE solver. This paper presents a validation study of the LS-DYNA MMALE approach with existing experimental studies of blast wave clearing and blast in an urban environment, as well as numerical results from the finite volume method software Air3d. The overpressure histories, peak overpressures and impulses are compared. It is demonstrated that the results from LS-DYNA produce excellent correlation with experimental and Air3d simulation results. Whilst this is a validation with prior knowledge of the experimental results, it suggests that the LS-DYNA simulation capability is accurate for the cases studied.

Validation Process of the Electromagnetism (EM) Solver in LS-DYNA v980: The TEAM Problems

I. Caldichoury, P. L’Eplattenier (Livermore Software Technology Corp.)

LS-DYNA version 980 includes an electromagnetic (EM) solver that can be coupled to the solid mechanics and thermal solvers of LS-DYNA to take full advantage of its capabilities to successfully solve complex industrial applications such as magnetic metal forming or welding, induced heating, and so forth. This paper will provide some insight on the validation process that is currently under way and focus on the so-called TEAM (Testing Electromagnetic Analysis Methods) problems. TEAM Workshops are meetings of an open international working group aiming to compare electromagnetic analysis computer codes. A series of TEAM Workshops was started in 1986 and has been organized in two-year rounds, each comprising a series of “Regional” workshops and a “Final” Workshop, as a satellite event of the COMPAQ Conference. The TEAM problems consist in a set of test-problems, with precisely defined dimensions, constitutive laws of materials, excitations, etc., each backed by a real laboratory device, on which measurements can be made. The range of the TEAM problems cover a wide area of applications and features such as moving or non-moving conductor parts, magnetic elements, conductors in time dependent magnetic fields and so forth. Several TEAM test cases and their simulation results that are part of the global validation process of the solver will therefore be presented highlighting some features and application domains of the solver.

Virtual Prototyping for Safer Product Development: Integrated Marine Propulsion and Steering System Example

M. Perillo, D. Schiavazzi, V. Primavera (EnginSoft SpA), D. Sacchi (ZF Marine)

Abstract ZF Marine’s POD Drive is an innovative marine integrated propulsion and steering system with increased performances compared to traditional shaftline systems in term of efficiency, manoeuvrability, ease of control and dimensions. The system comprises an inboard/outboard transmission and double motor electrical steering pod system equipped with counter-rotating propellers. An electronic control system manages one or more PODs and each of them rotates independently, depending on maneuver typology, speed and turning circle. Due to their manoeuvring orbital functions ̧ operating conditions and under hull position, underwater impact risk assessment is demanded as important safety design requirement. To decode any potential impact scenario into its design specification is a technical challenge concerning the capability to predict structural consequences. A new design methodology, that incorporates statistical approaches to investigate non deterministic factors that affect design impact conditions (e.g. impact velocity and angle, debris mass and stiffness, etc.) and Virtual Prototyping tools is developed to increase safety reliability of the design choices respect to accidental underwater impacts. Sensitivity analyses, parametric numerical models with increasing complexity and different simulation methods are employed during design process to design different sacrificial components able to break or to shear below the hull for minimizing damage to POD system or to the primary boat structures. Complete 3D numerical simulations are performed through LS-DYNA and full scale experimental tests are carried out either to validate design process and numerical models or to compare numerical and experimental results.