Martin N. Raftenberg – U.S. Army Research Laboratory
A brittle damage model developed by M. A. Grinfeld was implemented in the LS-DYNA finite element code and applied to the simulation of normal plate-on-plate impact. The model introduces a state variable measure of damage that evolves in proportion to the elastic strain energy. The model degrades the elastic shear modulus in proportion to the state variable’s current level. The implementation procedure by means of the LS-DYNA user- material interface is described. In a simulation of normal plate-on-plate impact, the model produced a gradient in elastic properties within the initially homogeneous target, and this gradient led to a partial reflection of the unloading wave. For a range of values for the material constants introduced by the damage model, the target’s free-surface velocity showed a gradual increase over time following the arrival of the initial compressive shock. This observation is discussed in light of the phenomenon of failure waves.
S. Kolling, M. Feucht – DaimlerChrysler AG, A. Haufe – Dynamore GmbH, P.A. Du Bois – Consulting Engineer
Reliable prediction of the behavior of structures made from polymers is a topic under considerable investigation in engineering practice. Especially, if the structure is subjected to dynamic loading, constitutive models considering the mechanical behavior properly are still not available in commercial finite element codes yet. In our paper, we present a new constitutive law for polymers which recovers important phenomena like necking, crazing, strain rate dependency, unloading behavior and damage. In particular, different yield surfaces in compression and tension and strain rate dependent failure, the latter with damage induced erosion, is taken into account. All relevant parameters are given directly in the input as load curves, i.e. time consuming parameter identification is not necessary. More- over, the models by von Mises and Drucker-Prager are included in the description as special cases. With the present formulation, standard verification test can be simulated successfully: tensile and compression test, shear test and three point bending tests.
S. S. Akarca, W. J. Altenhof, A. T. Alpas – University of Windsor, Canada
Sliding wear of aluminum alloys induce plastic deformation below the contact surfaces even at light loads. Experimental evidence exists for damage accumulation in the form of nucleation of voids and microcracks around the second phase particles in the material layers adjacent to the contact surface. Crack propagation at a certain depth below the surface may lead to the creation of long and thin wear debris particles. The objective of this work was to study deformation and damage accumulation processes in aluminum alloys during sliding wear. LS-DYNA was used to model multiple sliding contacts between an aluminum alloy and a steel counterface. The material model used in the finite element analysis was based on the stress/strain behaviour of a 356 Al (Al-7%Si) alloy determined directly from the analysis of the deformation state of the subsurfaces generated during sliding wear tests. Strain rate and thermal effects were also considered through a coupled thermal and mechanical analysis using material type 106 in LS-DYNA (*MAT_ELASTIC_ VISCOPLASTIC_THERMAL). The accumulation of stresses and strains were studied as a function of contact cycle number. The Lagrangian thermal and mechanical coupled finite element model developed in LS-DYNA was successful to simulate deformation of the aluminum alloy during sliding contacts. Subsurface distributions of the hydrostatic pressure, strain rate and temperature, which are difficult to characterize experimentally or theoretically for work hardening materials, were determined for different loading conditions during sliding contacts. Predicted distributions of stresses and strains were used to model subsurface damage gradient and delamination of subsurface layers. Numerical investigation of a void growth model based on a ductile void growth theory showed the presence of a damage gradient and a critical depth at which delamination cracks might initiate and propagate.
H. S. Lu, C. T. Wu – Livermore Software Technology Corporation
Procedures to adaptively refine meshes are emerging as an important tool for improving accuracy and efficiency in large deformation and fracture analysis. Comparing to the mesh- based adaptive method, the grid-based adaptive mesh-free method has several built-in advantages including naturally conforming in shape functions, smoothed interpolations in surface construction and state variable transfer, and the results are less sensitive to the unstructured grids. In this paper, a grid-based adaptive scheme is proposed for the Element Free Galerkin method in the large deformation analysis of three-dimensional forging and extrusion simulations. To precisely account for the effect of kernel functions during adaptive procedure, we consider the meshfree adaptivity in the framework of arbitrary Lagragian-Eulerian meshfree method with an operator-split time integration. A grid-based interpolation scheme adopted from the meshfree approximation is developed for the state variable transfer after mesh refinement to improve conservation and monotonic properties. Several industrial problems have been solved and compared to the existing numerical methods.
Kelly S. Carney – NASA Glenn Research Center, David J. Benson – University of California, Paul Du Bois, Ryan Lee – The Boeing Company
Modeling the high velocity impact of ice was a requirement in the safety calculations for the return-to-flight of the Space Shuttle on July 26, 2005. Ice, however, is not a common structural material and commercial finite element programs didn’t have any appropriate models. A phenomenological model with failure was developed to match experimental ballistic tests. The model has a relatively small number of material constants, most of which have been measured experimentally. A description of the model and comparisons of calculations to experiments are presented.
Karen E. Jackson, Edwin L. Fasanella – US Army Research Laboratory, VTD, Karen H. Lyle – NASA Langley Research Center, Regina L. Spellman – NASA Kennedy Space Center
A study was performed to examine the influence of varying mesh density on an LS-DYNA simulation of a rectangular-shaped foam projectile impacting the space shuttle leading edge Panel 6. The shuttle leading-edge panels are fabricated of reinforced carbon-carbon (RCC) material. Nine cases were executed with all possible combinations of coarse, baseline, and fine meshes of the foam and panel. For each simulation, the same material properties and impact conditions were specified and only the mesh density was varied. In the baseline model, the shell elements representing the RCC panel are approximately 0.2-in. on edge, whereas the foam elements are about 0.5-in. on edge. The element nominal edge-length for the baseline panel was halved to create a fine panel (0.1-in. edge length) mesh and doubled to create a coarse panel (0.4-in. edge length) mesh. The element nominal edge- length of the baseline foam projectile was halved (0.25-in. edge length) to create a fine foam mesh and doubled (1.0- in. edge length) to create a coarse foam mesh. The initial impact velocity of the foam was 775 ft/s. The simulations were executed in LS-DYNA for 6 ms. Predicted structural deformations and time-history responses are compared for each simulation.
Xudong Xin – Karagozian and Case
The kinetic feature of weapon fragment is many small masses traveling at extremely high velocities and scattering radially from the explosion center. To simplify the fragment impact analysis, people often convert the fragment momentum into a triangular pressure load with very high magnitude and very short duration, and apply the load directly onto the target. This method may over- or under-predict the impact response due to the complicacy of fragment behaviors such as embedment, perforation and ricochet. It might encounter more difficult situation when involving multi-layer impact and penetration problem. This paper proposes a new method for fragment simulation using the contact technique provided in LS-DYNA. A program was developed which can automatically generate the LS-DYNA keyword input of node, part, initial velocity and contact surface cards for multiple pieces and sets of fragments, based on the given information about mass, location, velocity of each fragment, and other user-defined parameters. This method can be applied not only on multi-piece fragment impact simulation, but also on multi-hit problem in a realistic way. Examples of fragment impact on structure are demonstrated.
Qian Wang, Tanya Kapoor, William Altenhof – University of Windsor, Andrew Howard – The Hospital for Sick Children
This research focuses on the injury potential of children seated in forward facing child restraint seats during side impact crashes. Side dynamic sled tests were conducted by NHTSA using the existing FMVSS 213 seat fixture oriented at both 90° and 45° relative to the motion of the sled buck. A half sine pulse and a scaled FMVSS 213 pulse were used in the tests. All the tests were conducted at a test velocity of 32 km/h (20 mph) and a peak acceleration of 17 g’s. A forward-facing Hybrid III 3-year-old child dummy positioned in a child restraint seat (CRS) with LATCH and the top tether in far side configurations were used in the tests. Details of the sled tests were stated in FMVSS 213 ANPRM. A finite element model of the child restraint seat was developed using FEMB for simulation in LS- DYNA. The child seat model, which included all CAD surfaces provided by Century/Graco Corporation, was fully deformable and was previously validated for frontal impacts. Three side impact simulations were completed for data comparison. (i) using the half sine acceleration pulse with the seat oriented at 90° relative to the motion of the sled, (ii) using the half sine acceleration pulse with the seat oriented at 45° relative to the motion of the sled, and (iii) using scaled FMVSS 213 acceleration pulse with the seat oriented at 90° relative to the motion of the sled. Validation of the numerical model was completed by comparing the head injury criteria (HIC) values and chest accelerations from the experimental and numerical tests. The simulation results were generally in good agreement to the experimental observations. Further studies were conducted to confine lateral movement of the dummy’s head by adding energy absorbing foam blocks in the head region of the CRS. It was observed from the simulation results that foam padding was effective in reducing the injury potential of the child dummy.
Jingyun Cheng, Wieslaw K. Binienda – The University of Akron, Akron OH
A simplified methodology has been developed for modeling 2D tri-axially braided composite plates impacted by a soft projectile using an explicit nonlinear finite element analysis code LS-DYNA. Fiber preform architecture is modeled using shell elements by incorporating the fiber preform architecture at the level of integration points. The soft projectile was modeled by an Equation of State (EOS). An arbitrary Lagrangian-Eulerian (ALE) formulation is used to resolve numerical problems caused by large projectile deformation. The computed results indicate that this numerical model is able to simulate a tri-axially braided composite undergoing a ballistic impact effectively and accurately, including the deformation and failure with a reasonable level of computational efficiency.
D.J. Benson – University of California, S. Kolling- DaimlerChrysler AG, P.A. Du Bois – Consulting Engineer
Simulation of rubber-like materials is usually based on hyperelasticity. If strain-rate dependency has to be considered viscous dampers are added to the rheological model. A disadvantage of such a description is time- consuming parameter identification associated with the damping constants. In this paper, a tabulated formulation is presented which allows fast generation of input data based on uniaxial static and dynamic tensile tests at different strain rates. Unloading, i.e. forming of a hysteresis, can also be modeled easily based on a damage formulation. We show the theoretical background and algorithmic setup of our model which has been implemented in the explicit solver LS-DYNA -. Apart from purely numerical examples, the validation of a soft and a hard rubber under loading and subsequent unloading at different strain rates is shown.
Kaushik Sinha – DaimlerChrysler Research and Technology
This paper presents a holistic simulation-driven system design methodology considering multiple performance objectives, performance constraints including formability criterion defined herein, using a genetic algorithm based multi-objective optimization software GDOT, developed in-house. This tool treats multiple objective functions separately without combining them in any form. A decision-making criterion is subsequently invoked to select the “best” subset of solutions from the obtained non-dominated Pareto optimal solutions under multiple performance constraints along with a formability index. Geometric properties, associated material properties (yield strength / plastic strain to failure) are considered as design variables. An example involving the frontal impact on a rail section is used to demonstrate the methodology. This process can further suggest requirements for synthesizing new materials that will result in optimal product performance. The objective of this study is to establish an ‘optimized’ set of design parameters with the dual aim of (i) minimizing the structural weight and (ii) maximizing energy absorption efficiency of the front rail system during frontal impact. The performance constraints being maximum transmitted force, maximum intrusion, pulse efficiency and formability criterion. This study also looks at the effect of parameter uncertainty on the optimal design. This study is composed in two stages. The first stage attempts to solve the multi-objective optimization problem, which is attempted using proprietary GDOT optimization code. Stage two performs reliability-based multi-objective optimization to generate a ‘reliable’ pareto optimal front. A 2nd order meta model is developed using responses, including formability index, computed from physics-based finite element models using LS-DYNATM analysis code. Looking at a broader picture, this methodology can potentially fill the gap between numerically optimized system development and simulation-driven digital product development. This, in turn, will help realize numerical simulation-driven product development process by aiming to achieve designs that are “first time right”.
Soon-Young Seo, Jae-Woo Jeong, Dong-Hyeob Cho, Hyuk Kim – Samsung Electronics Co. Ltd.
In the mobile electronic appliances market, the feature of products is getting smaller, thinner and more multi- functional. Therefore, mobile products are easily damaged from drop/impact and thermal cycling load. To make them more reliable under these conditions, the junction area between chips and PCB should be designed to bear up under drop/impact. And the heat caused by main chip (Memory & DMB channel chip) should be dissipated as quickly as possible. From the viewpoint of CAE simulation, although those two problems (drop & heat) should be considered simultaneously, they should not. Because the outline of PCB mainly depends on the location of main chip, positioning the main chip is one of the most important steps in the initial design stage. And the dynamic stress from free drop and heat caused by main chip are the one of the most critical factors to position the main chip. This paper presents the design process for positioning the main chip on PCB of PMP using MDO method. That is, the trade-off design variables between drop and thermal loading analysis were identified and system level optimization is performed in parallel. The main theme of this paper is to provide a way to get MDO solution of the PMP model in the early design stage.
Thomas Borrvall – Engineering Research Nordic AB
The user-defined features in LS-DYNA are powerful tools that allow users in academia or industry to verify research results in the context of general and complicated finite element applications. Implementation work concerns only the special field of interest, and there is no need for the comprehensive task of developing and maintaining the complete finite element software. One of the new user-defined features in LS-DYNA v971 is the possibility to define structural solid and shell elements. Up to a total of ten element formulations can be implemented in a single LS-DYNA executable both for explicit and implicit analyses. A high abstraction-level interface is in particular provided for numerically integrated elements, and stabilization schemes can easily be incorporated. There is also the option to implement discrete elements, and property parameters and history variables can be associated with the element. The interface is equipped with additional features that facilitates research on element technology, but also makes it perfectly suited for educational purposes. An overview of the procedure of implementing an element in the new interface as well as invoking it from the keyword input file will be presented.
M. Raguraman and A. Deb – Indian Institute of Science, Bangalore
The present paper deals with the simulation of impact of jacketed projectiles on thin to moderately thick single and multi-layered metal armor plates using explicit finite element analysis as implemented in LS-DYNA. The evaluation of finite element modeling includes a comprehensive mesh convergence study not previously reported in literature, using both shell and solid elements for representing single-layered mild steel target plates. It is shown that the proper choice of contact algorithm, mesh density, and strain rate-dependent material properties is crucial as these parameters significantly affect the computed residual velocity. The modeling requirements are initially arrived at by correlating against test residual velocities for single-layered mild steel plates of different depths at impact velocities in the range of ~800-870 m/s. The efficacy of correlation is adjudged in terms of a ‘correlation index’, defined in the paper, for which values close to unity are desirable. The experience gained for single-layered plates is next used in simulating projectile impacts on multi-layered mild steel target plates and once again a high degree of correlation with experimental residual velocities is observed. The study is repeated for single- and multi-layered aluminum target plates with a similar level of success in test residual velocity prediction. To the authors’ best knowledge, the present comprehensive study shows in particular for the first time that, with a proper modeling approach, LS-DYNA can be used with a great degree of confidence in designing perforation-resistant multi-layered steel and aluminum armor plates.
Phone drop simulation is an important application of LS-DYNA in electronics industry. The application has been widely used in all leading companies to produce electronic handsets, like Nokia, Motorola, and Samsung. Since more new features complemented in 970 version of LS-DYNA, phone modeling and drop simulation strategy has changed a lot to obtain more accurate and quick results. This paper introduces new methods, and recent development of phone modeling and drop simulation, based on author’s experiences in recent years. The paper is focused on using right element type in LS-DYNA element library and some new strategies to establish better phone model and drop simulation. The paper provides benchmarks to verify the modeling strategies. The paper still gives an example for advanced application of LS-DYNA in multiply impact simulation.
Hubert Lobo – DatapointLabs
High strain-rate properties have many applications in the simulation of automotive crash and product drop testing. These properties are difficult to measure. Previously, we described a novel inferential technique for the measurement of the properties of polycarbonate. In this paper, we demonstrate that the technique appears to work for a variety of polymers. We also show that plastics exhibit different kinds of high-strain rate behaviors. It is important to use an appropriate LS-DYNA material model for valid simulation results.
Dr. Tore Tryland – Hydro Automotive Structures
The deformable barriers consist mainly of honeycomb blocks with highly anisotropic behaviour. These parts are made from several layers with aluminium foil that is glued and stretched to form the honeycomb structure. Simple compression tests show high stiffness and strength when the cell structure is folded while both stiffness and strength are significantly lower when the deformation mode is mainly bending of the thin foil. Remember that the typical deformation mode involve also transverse displacement of barrier parts, and when the honeycomb structure is folded this may be seen as the interaction between local and global buckling. Therefore, shell elements are used to model the honeycomb structure, and alternative models of the offset and the side impact deformable barriers are made. Note that scaling is used extensively to limit the number of elements and thereby the computational time that is required. These models with about 30 000 shell elements seem able to predict the global response of the deformable barriers, and they may be easily refined to represent more local behaviour as well.
Tim Keer – Arup
The automotive safety community is currently facing the challenge of new pedestrian impact requirements, introduced in Europe in 2005. These requirements necessitate considerable changes to the vehicle front end (bumper system, hood and fenders). LS-DYNA models of the pedestrian impactors (head, upper leg and leg) are an important tool for analysis of the various tests that comprise the new requirements. One of the criticisms of the current tests concerns repeatability. Physical testing with the leg impactor, in particular, shows considerable scatter of results. This lack of repeatability can cause the system to be over-designed to give sufficient confidence that the vehicle will meet the pedestrian safety requirements during compliance testing. Lack of repeatability in the results from physical leg impact tests can be caused by three main groups of factors: – variations in the vehicle (e.g. build tolerances) – variations in the legform impactor (e.g. properties of the Confor foam “skin”) – variations in the test set-up (e.g. impact velocity) This paper describes an LS-OPT study designed to assess these issues. An LS-OPT Monte Carlo simulation was used to perform a series of LS-DYNA analyses and to assess the relative importance of the different factors in these groups. The results give insight into the parameters which should be controlled most tightly in order to improve the repeatability of leg impact testing. The paper concludes with a discussion of the benefits of this approach and the potential for further application.
Ali Shahkarami, Reza Vaziri – The University of British Columbia, Canada
An efficient shell element based computational model is developed to capture the mechanical response of fabrics. The approach considers a single yarn crossover as the basic building block (unit-cell) of the fabric panel and uses a specially formulated shell element within LS-DYNA to capture the essential features of the membrane response of this unit-cell accounting for both geometrical and material characteristics of the yarns. The shell element so developed is used to simulate the impact response of single and multi-ply packs of Kevlar® 129 fabric. The predictions are successfully compared with the measurements obtained from instrumented ballistic impact experiments.
Kadir Elitok, Dr. Mehmet A. Guler, Bertan Bayram – Product Development Dept., TEMSA A.S., Dr.-Ing. Ulrich Stelzmann – CADFEM GmbH
A roll-over event is one of the most crucial hazards for the safety of passengers and the crew riding in a bus. In the past years it was observed after the accidents that the deforming body structure seriously threatens the lives of the passengers, thus the roll-over strength has become an important issue for bus and coach manufacturers. Today the European regulation “ECE-R66” is in force to prevent catastrophic consequences of such roll-over accidents thereby ensuring the safety of bus and coach passengers. According to the said regulation the certification can be gained either by full-scale vehicle testing, or by calculation techniques based on advanced numerical methods(i.e. non-linear explicit dynamic finite element analysis). The quantity of interest at the end is the bending deformation enabling engineers to investigate whether there is any intrusion in the passenger survival space(residual space) along the entire vehicle. In this paper, explicit dynamic ECE-R66 roll-over crash analyses of a stainless-steel bus under development were performed and the strength of the vehicle is assessed with respect to the requirements of the official regulation. Subsequently, different considerations which are not currently mentioned in the regulation (i.e. passenger and luggage weight) and some worst case assumptions such as the influence of the seat structure were investigated. The non-linear explicit dynamics code LS-DYNA as a solver and ANSA and LS-PREPOST softwares as FEA pre/post- processors were utilized throughout the bus roll-over analysis project. The FEA model was generated by using PCs running on Linux Suse operating system whereas the LS-DYNA solutions were performed on a multiple-processor workstation running on an AIX UNIX operating system. During the first stage, a verification of the calculation procedure following regulation ECE-R66 was performed. The verification of calculation is a compulsory requirement of the regulation, as it is the technical service’s responsibility(TÜV Süddeutschland in this case) to verify the assumptions used in the finite element analysis.
Mauricio V. Donadon, Lorenzo Iannucci – Imperial College London
Predictive techniques for the analysis and design of metallic or composite components and structures subject to severe loading can lead to significant mesh sensitivity if cracking or tearing or penetration occurs. This is especially important for composite materials in which the material has an elastic brittle response with little or no plastic behaviour, in which energy could be dissipated. Hence, the full potential use of composite in the design of advanced composites and structures has not yet been exploited fully. This work constitutes an effort directed towards the development of an objectivity algorithm for strain softening material models based on the ‘smeared cracking formulation’. The algorithm has been implemented into LS-DYNA for hexahedron solid elements and correctly accounts for crack directionality effects. Thus enabling the control of energy dissipation associated with each failure mode regardless of mesh refinement and element topology. The advantage of the present technique is that mesh size sensitivity on failure is removed leading to results, which converge to a unique solution, as the mesh is refined. If such a scheme were not introduced results could change significantly from mesh to mesh leading to an incorrect structural response. The proposed algorithm has been validated by a series of benchmark tests using different degrees of mesh refinement and element topologies.
Ashish Bhargava, W.M. Kim Roddis, Dhafer Marzougui, Pradeep K. Mohan – The George Washington University
Moment-Resisting Frames (MRF’s) are widely used as lateral-force resisting systems in buildings. Their successful performance depends on the behavior of their moment-resisting beam-column connections. In regions at risk for earthquakes, MRF’s need to resist large cyclic forces and displacements. A variety of beam-column connections are used in practice. Most, including end plate connections, are designed assuming the MRF seismic capacity is based on the ability of the connection to allow inelastic rotation through the development of plastic hinges within the beam elements of the structure. In this paper, Finite Element (FE) computer analysis is used to simulate the behavior of the joint region of an MRF. A computer model of the MRF’s extended end plate beam-column connection was created and its performance was analyzed under cyclic loading condition. The LS-DYNA implicit solver was used in this study. Results from these simulations were compared to previously conducted physical tests. The results show good correlation with the measured test data. The work demonstrates the ability of LS-DYNA to simulate the cyclic behavior of this type of beam-column connection and is a step toward using physically calibrated computational model to complement physical testing for the future evaluation of this type of structural detail.
Samir N. Shoukry, Gergis W. William, Mourad Riad – West Virginia University
This paper describes the application of the dynamic relaxation technique implemented in LS-DYNA in analyzing large transportation structures as dowel jointed concrete pavements under the effect of temperature variations. The main feature of the pavement model is the detailed modeling of dowel bars and their interfaces with the surrounding concrete using extremely fine mesh of solid elements, while in the bridge structure, it is the detailed modeling of the girder-deck interface as well as the bracing members between the girders. The 3DFE results were found to be in a good agreement with experimentally measured data obtained from instrumented pavements sections constructed in West Virginia. Thus, such a technique provides a good tool for analyzing the response of large structures to static loads in a fraction of the time required by traditional implicit finite element methods.
Akram Abu-Odeh – Texas Transportation Institute
The subject of roadside safety has been seeing a healthy growth in the use of nonlinear finite element analysis in designing and analyzing roadside hardware systems. Some factors that helped researchers include the expanded capabilities of LS-DYNA commercial finite element code, the availability of several public domain vehicle models and the availability of material models explicitly built and modified for roadside safety applications. One of these new material models is *MAT_CSCM (and the short input version *MAT_CSCM_CONCRETE) incorporated in LS- DYNA version 971 as material type 159. Material model *MAT_CSCM which was developed by APTEK INC. is a continuous surface cap material model with the ability of capturing concrete material behavior using minimal input like the compressive strength of concrete and maximum aggregate size. In this paper two examples of using LS- DYNA to simulate impacts with concrete barrier are presented. They are two different pendulum simulations of a concrete parapet with a steel railing on top. The deformation and damage profiles along with the force time history were used as measures for comparing tests and simulations. Both examples indicate a reasonable correlation between tests and simulations. Figure 1a shows the response of the concrete parapet as tested and figure 1b shows the response calculated from the LS-DYNA simulation.
S. Stahlschmidt, B. Keding, U. Franz – DYNAmore GmbH, Germany, A. Hirth – DaimlerChrysler AG, Germany
Whiplash injuries frequently occur in low speed rear crashes. Many consumer and insurance organizations use the BioRID II dummy, to assess the risk of whiplash injuries in car accidents. An LS-DYNA model of the BioRID II dummy has been developed by DYNAmore GmbH in cooperation with the German Automotive Industry. In the consortium a huge effort has been made to build a test database for the development of the FE-dummy. This paper describes the effort performed to generate the experimental data for material, component and full dummy validation. The dummy contains a considerable number of pre-stressed parts which can not be neglected since it stiffens the neck significantly. In order to capture the occurring pre-stresses appropriately the modeling techniques require the application of new features in LS-DYNA and specific handling during pre-processing. The paper describes the model and shows its performance in validation tests. Finally, different whiplash simulations are used to emphasize influences of selected parameters on injury criteria of the BioRID II model.
Lorenzo Iannucci, Mauricio Donadon – Imperial College London
The bird strike impact problem is an increasing menace to the composite aerospace designer, especially since more aerospace components are being manufactured from composite materials. The LS-DYNA FE code is often used to model such an event as it can accurately represent the bird material behaviour and the contact between the bird and the structure. However, numerical simulations are usually accompanied by a parallel testing programme to validate the numerical simulations for some of these impact scenarios. The present paper described the implementation of an improved damage mechanics based material model to simulate the progressive failure of woven glass composites. A series of bird strike impacts on flat panels fabricated from low cost woven glass composite materials are used to validate the material model for practical composite component applications. The panels are modelled with shell elements only. The new material model can capture the strain rate enhancement to strength and strain observed for woven glass materials using a damage lag concept. A hydrodynamic model for the bird, based on 90% water and 10% air, is used to represent the behaviour of the bird for all impact scenarios considered. The bird is heterogeneous in nature, however, a uniform material behaviour is assumed with a geometry based on a 2:1 length: diameter ratio with a cylindrical body and spherical end caps using mesh less Smooth Particle Hydrodynamic (SPH) techniques. Appropriate contact definitions are used between the bird and the composite panel. The simulations results are compared to experimental results and conclusions drawn.
Cheng-Ho Tho, Michael R. Smith – Bell Helicopter Textron Inc.
Bird strike incidents are not uncommon and cost the U.S. civil aviation industry approximately $495 millions and 631,341 hours of downtime annually . The development test to meet the bird strike certification requirements is very costly and time-consuming. This paper presents the bird strike analysis using the Arbitrary Lagrangian- Eulerian (ALE) technique in LS-DYNA for the BA609 spinner and rotor controls assembly shown in Figure 1. The objective is to reduce the development costs and cycle time while achieving weight-efficient resistant design by accurately predicting the composite failures and structural impact performance – with the ultimate goal of certifying by analysis only. The spinner assembly provides the swashplate drive load path and aerodynamic fairing for the rotor hub and controls. The failure of the spinner assembly could result in loss of the aircraft. Therefore the assembly must show compliance with “continued safe flight and landing” requirements following the high-energy bird impact. An idealized cylinder with hemispherical ends surrounded by air, which is modeled as 1-point ALE solid elements, is used to represent the bird model. The bird strike finite element model is validated through correlation with the tests conducted at the Southwest Research Institute of San Antonio in February 2005. This paper analyzes three most load-critical test conditions and evaluates the structural failures of the spinner assembly subjected to the bird strike dynamic loads. Figure 2 shows the correlation of one of the airplane mode shots for a 4.0-lb [1.8-kg] bird fired from a compressed gas gun at 240 kts [127.3 m/s] impact velocity targeting at the upper spoke of the spinner controls. Numerical results showed favorable correlation in terms of composite failure modes on the spinner cone, and the secondary impact fracture of the controls components such as upper spoke and cyclic link. The validated analytical model is used as a design support tool to produce useful information on the load mechanisms to guide the program for redesign.
Guangtian Gavin Song, Rana Sanghera, Surya Yerva, Hamid Keshtkar – DaimlerChrysler Corporation
In automotive industry, CAE fatigue life analysis is very important in durability evaluation and product optimization to dramatically reduce the design period and minimize the expensive durability testing. In the past time, CAE fatigue life analysis is constrained to the linear stress based methodology in the local strain approach. Generally, the linear stress based methodology is stress analysis with linear material properties. Contact surface could be defined if needed for large deformation and rotation dynamic problem. Then, the stress time history result is retrieved to input to further fatigue life analysis or firstly converted to nonlinear stress with Neuber’s rule with considering plastic deformation effect. But in some cases, the structure’s large deformation and rotation movement can make large area plastic deformation. Under those cases, the linear stress based methodology can’t precisely predict the load path, and further affect the following fatigue analysis accuracy. Nonlinear dynamic method with material nonlinearity should be used in stress prediction for those cases, and the principal strain time history retrieved from nonlinear stress analysis can be directly input to fatigue analysis. This investigation takes door slam as example with LS-DYNA as solver in both the linear and the nonlinear methodology based stress analyses and with Fe-Fatigue in fatigue life analyses to show the linear stress based methodology more conservative and the nonlinear stress based methodology more accurate together with strain life method for low cycle fatigue in nonlinear dynamic problem.
Stefano Magistrali – Omega Srl, Research and Innovation Centre, Marco Perillo – EnginSoft SpA
Experimental quasi-static tensile and impact tests were conducted over two different types of composite laminates and four different types of sandwich laminates, in order to evaluate their basic mechanical characteristics and energy adsorption capability. The second phase of this research work approaches and resolves the calibration of the mechanical parameters included into the LS-DYNA composite material models. This calibration starts and is based on the material physical properties derived from the test results. LS-DYNA model parameters, model constrains and objectives defining the problem have been studied and analysed by using modeFRONTIER. modeFRONTIER is a multi-objective and multi-disciplinary integrated platform. Input parameters were varied into a controlled range. This allows to find quickly and to define accurate model configuration as well as model sensitivity to those parameters, leading to reliable numerical models for impact simulations. Accurate comparison of simulation results with experimental material results is crucial to achieve optimum and precise material models. The present research study offers also an understanding of the effect of numerical input parameters and variables on sandwich laminates structural response in terms of absorbed energy, maximum energy, maximum force and curve morphology. Calibration of material models, able to reproduce the effective impact behaviour of real composite materials, is fundamental in order to simulate general crashworthiness problems. This kind of approach allows either to understand variable influences on composite dynamic structural response or to get improved solution for industrial case studies.
Haipeng Han, Farid Taheri – Dalhousie University, Canada
In this paper the dynamic pulse buckling of laminated composite beams was analyzed using LS-DYNA and another widely used commercial FE code, namely NISA (Ver.12), developed by EMRC (Engineering Mechanics Research Corp). Two types of impact loadings that could induce dynamic pulse buckling of composite beams were analyzed. The first one was a force applied to the structure in a very short duration (i.e., an impulse load). The other one was the impact of a moving mass having a certain initial velocity. This problem brings considerable challenges if one is to simulate the phenomenon accurately. The main objective of this technical exercise was to investigate the influence of certain numerical parameters on the integrity of the out coming results. The objective was also to assess the performance of a “conventional, general purpose” type FEM program versus LS-DYNA, which is considered as a leading FEM code for the analysis of highly nonlinear phenomena. This was an interesting exercise in demonstrating why one should use codes like LS-DYNA, as oppose the general purpose FEA codes when considering such highly non-linear phenomena. Both abovementioned loading types were considered in this study. In the analysis using LS-DYNA, the force function was introduced by applying an impulse force at one end of the FRP beam. The moving object was also modeled in LS-DYNA by means of a rigid wall having a mass and an initial velocity. The impact by moving object could not be accommodated by NISA, so only the pseudo-impulse type loading could be considered in NISA. Parametric studies were also conducted to investigate the effect of the slenderness ratio, the curvature and the stacking sequences of the FRP beams, as well as the examination of the influence of the initial imperfection used to promote structural instability.
Stanley Posey – HPC Applications Development
Manufacturing industry and research organizations continue to increase their investments in structural analysis and impact simulations such that the growing number of LS-DYNA users continues to demand more from computer system environments. These LS-DYNA workflow demands typically include rapid single job turnaround and multi- job throughput capability for users with diverse application requirements in a high-performance computing (HPC) environment. Additional complexity arises from the need for many LS-DYNA HPC environments to coexist with other computer aided engineering (CAE) software for a variety of multi-physics and multi-scale structural and computational fluid dynamics analyses that all compete for the same HPC workflow resources. For today’s economics of HPC, these resources such as CPU cycles, memory, system bandwidth and scalability, storage and I/O, and file and data management – must deliver the highest levels of CAE productivity and HPC reliability that is possible from a Linux platform environment. This presentation examines workflow efficiencies of CAE simulations for relevant applications in LS-DYNA for an HPC Linux platform developed by SGI. LS-DYNA modeling parameters such as model size, element types, schemes of implicit and explicit (and coupled), and a variety of simulation conditions can produce a wide range of computational behavior and data management requirements, such that careful consideration should be given to how system resources are configured, deployed, and allocated to meet increasing user demands. The HPC system technology of the SGI® AltixTM clusters and servers, based on Linux® and Itanium® 2 from Intel®, have demonstrated both LS-DYNA turnaround and throughput achievement that includes industrial-sized examples. In addition, SGI simulation data management technology of HPC file systems and data storage tools, are providing the LS-DYNA workflow management necessary to maximize user productivity, and enable a user roadmap of increasing LS-DYNA modeling fidelity.
Hui-Ping Wang, Ye-Chen Pan, Yi-Pen Cheng – General Motors Corporation
This paper demonstrates applications of a coupled meshfree/finite element solver of LS-DYNA in the analysis of crashworthiness components. Two examples are employed in the study. The first one is a European side impact dummy component test problem. It is used to show the robustness of the coupled meshfree/finite element solver in handling large deformation since the finite element analysis of this problem fails due to numerical instability caused by negative element volume. By applying the meshfree formulation to the large distortion area, we successfully complete the simulation and obtain very reasonable solutions. The second problem is an engine cradle drop tower test. Various background meshes are created for this problem to study the effect of different element connectivity on accuracy of the meshfree solutions. The study shows that, with the same particle distributions the meshfree analysis yields more consistent solutions than the finite element analysis when the background connectivity varies.
L.J. Deka, S.D. Bartus, U.K. Vaidya – University of Alabama at Birmingham
High velocity transverse impact to laminated fiber reinforced composites is of interest in military and structural applications. Damage evaluation of the targets during impact based upon experimental work can be prohibitively expensive. However recent advances in the field of numerical simulation provide a means of predicting the performance characteristics of layered materials for ballistic protection. There is however, limited information about the ballistic response of reinforced thermoplastic composite materials. The overall objective of this work is to investigate the behavior of a plain weave laminated composites of varying thicknesses under high velocity impact both from an experimental and modeling view point. To analyze this problem, a series of ballistic impact tests have been performed on plain weave E-glass/polypropylene laminated composites of different thicknesses with a 0.50 caliber cylindrical shaped flat nose projectiles. A gas gun with a sabot stripper mechanism is employed to impact the panels. To analyze the perforation mechanism, ballistic limit and damage evaluation, an explicit three- dimensional finite element code LS-DYNA is being used. Selecting proper material models and contact definition is one of the major criteria for accuracy of the numerical simulation. During high velocity impact, composite laminates undergo progressive damage failure and hence, Material Model 161, a progressive failure model based on Hashin’s criteria, has been assigned to predict failure of the laminates. The projectile is modeled using a Material Model 3 (MAT_PLASTIC_KINEMATIC). The laminates and the projectile are meshed using brick elements with single integration points. The impact velocity ranged from 187 to 332 m s-1. A good correlation between the numerical and experimental results has been drawn in terms of predicting ballistic limit, delamination and energy absorption during impact.
Gary Owen – Autoliv
This paper describes a demand driven product development method that applies a synergetic combination of numerical simulation and physical test techniques to guide the development of side impact restraint systems and associated simulation procedures and physical test devices.
J.S. Bergström, A.E. Bowden – Exponent, Inc, C.M. Rimnac – Case Western Reserve University, USA, S.M. Kurtz – Drexel University, USA
Ultra-high molecular weight polyethylene (UHMWPE) is a semi-crystalline polymer with excellent strength, impact resistance, and abrasion resistance. These mechanical properties have led to extensive use of UHMWPE as a bearing material in total joint replacements. In order to accurately capture the experimentally observed response of this important polymer we have developed a new advanced material model—the Hybrid Model (HM). This constitutive model is physically motivated and based on a decomposition of the deformation gradient into elastic and viscoplastic components. The elastic response of the underlying molecular network is captured using the eight- chain hyperelastic model, and the viscoplastic response is represented using energy activated flow driven by the molecular reorganization that occurs during large deformations. The constitutive theory for the HM has been implemented as a user-material model (UMAT) for ls971 and is available for both explicit and implicit simulations. For optimal accuracy and numerical efficiency the UMAT uses a forward Euler integration scheme for explicit simulations, and a higher order backward differentiation formula (BDF) method for implicit simulations. The HM was calibrated to data from uniaxial tension experiments performed at different strain rates and with different loading-unloading segments. For validation, the calibrated HM was then used to simulate a small punch test. A direct comparison between the experimental data and model predictions of the calibration and validation data demonstrate that the HM accurately captures the non-linear response of UHMWPE. The ability to simulate large-scale contact problems was examined by simulating the deformation behavior of a total knee replacement component and the CharitéTM artificial discs.
Costin Untaroiu, Jaeho Shin, Jeff Crandall, Scott Crino – University of Virginia
Head injuries are the most common cause of pedestrian deaths in car-to-pedestrian collisions. To reduce the severity of such injuries, international safety committees have proposed subsystem tests in which headform impactors are impacted upon the car hood. In the first part of the paper, the development and validation of an adult headform impactor finite element (FE) model is presented. The skin material model was assumed as viscoelastic and its parameters were identified by FE optimization to match the quasi-static and dynamic test data reported in literature. Overall, it was shown that the geometrical and inertial characteristics of the headfom FE model developed in this study satisfy the regulations of international safety agencies. The second part of the paper presents results of a hood optimization using simulations of the headform-hood impact test. A generic hood design was assumed consisting of two plates connected by buckling structures. The reductions of head injury risk under impact and the under-hood clearance space were included in an optimization problem which considered the geometry of connecting spools and the panel thicknesses as design variables. The automatic design process was shown to converge to an optimum design after several iterations. The methodology and recommendations for future work presented in this paper may assist in the hood design of new car models to reduce pedestrian head injuries and meet new safety requirements.
Shigeki Kojima – Toyota Technical Development Corporation, Japan, Tsuyoshi Yasuki – Toyota Motor Corporation, Japan
This paper describes a new finite element modeling method of aluminum honeycomb using shell elements. It is our new modeling method that cell size of honeycomb structure is enlarged to keep minimum mesh size, and compressive strength is controlled by thickness of shell elements. New modeling was applied to an offset deformable barrier model, and full vehicle crash analysis was performed. The result of offset frontal collision analysis with a new honeycomb model showed much better correlation with test results than with modified material type-126 solid elements.
Nauman M. Sheikh, Roger P. Bligh, D. Lance Bullard, C. Eugene Buth, Dean C. Alberson, Akram Y. Abu-Odeh, Hayes E. Ross Jr. – Texas Transportation Institute
An energy absorbing end terminal was developed for use with the European box beam guardrail system. The European box beam rail sections have an open architecture that is different from what is used in North America. The overall design effort utilized finite element simulation, individual component testing using the bogie and pendulum, and performance validation by full scale vehicle crash testing. The design process involved addressing several individual component performance issues. Of these were the design of an extruder head, splice connections for attaching adjacent rail segments, the post to rail attachment connection and anchorage of the rail. The research approach and results are presented in this paper.
Yucheng Liu, M. L. Day – University of Louisville, USA
In this paper bending resistance of thin-walled channel beam is applied to create simplified model for truck chassis. In the simplified model, beam and nonlinear spring elements are used to model the side-rails, and equivalent beams are applied to represent the cross members. Both detailed and simplified models are used for crashworthiness analyses, and the results are recorded and compared. Relatively good agreement is achieved between these analyses, while the computing time is significantly reduced for the presented modeling method.
David M. Fox – US Army Tank Automotive Research, Warren, MI
In order to streamline the product development process, the design space for FMVSS 201U impact performance of a steel mechanical energy absorber assembly was investigated by means of LS-DYNA 970 explicit finite element simulation methods in conjunction with statistical analytical procedures. A sequence of response surfaces, based on various levels of design parameters, was developed and used to determine minimal stopping distance for which it would be possible to achieve acceptable impact attenuation performance under various impact loading conditions given a worst case assumption of rigid vehicle interior body panels. A model was also developed, based on the variation of deterministic variables, in order to estimate and minimize, by means of a robustness analysis, the range of deviation of product response that would be expected as a result of variability in manufacturing and installation processes.
Dan Neumayer – Bosch-Siemens-Hausgeräte, Madhukar Chatiri, Matthias Höermann – CADFEM GmbH
The present work deals with the numerical simulation of a drop test of a cooker including packaging foam and plastic foil wrapping. Additionally the pre-stressing of cooker and packaging due to thermal shrinkage of the plastic foil has been taken into account in the numerical investigation. For this, a thermal pre-stressing simulation of the plastic wrapping has been included before the actual drop test of the whole assembly has been conducted. The permanent deformations of the cooker nearby the impacted edge as well as the deformation of package foam in the vicinity of the impacted edge were the primary areas of interest and compared with experimental data. LS-DYNA  was used to perform the drop test simulation of the cooker as well as the thermal pre-stress simulation of the plastic wrapping.
Mike Yaksh, S. Alan Lin – NAC International Inc.
Evaluations are performed for the structural component of a fuel basket in a sealed container which is used for maintaining the configuration of spent nuclear fuel during storage. Spent fuel assemblies are placed into a basket structure which is comprised of separate tubes whose positions are maintained by a series of pins and sockets and an exterior frame work of stiffeners. The canister is placed in a vertical storage cask. The controlling condition is associated with lateral impact of the tip over of the storage cask which results in deceleration being applied normal to the axis of the basket and spent fuel. It is necessary to investigate the potential geometric instability of the array of tubes as well as the potential for a pin-socket component to fail in shear. The angular orientation of the basket affects the development of potential instabilities as well as the level of shear developed in the basket tubes at the pin- socket. In this paper the impact analyses for a system to store 87 BWR fuel assemblies are presented.
Alexey Borovkov, Oleg Klyavin, Alexander Michailov – St.Petersburg State Polytechnical University,, Martti Kemppinen, Mikko Kajatsalo – Mikkeli Polytechnic Research Centre YTI, Finland
Three Finnish associates, Tehomet Ltd, Fibrocom Ltd and Mikkeli Polytechnic Research Center YTI developed an internationally awarded energy absorbing lighting column product family in 2005. The design and dimensioning were assisted with static FEM computations, preliminary impact tests and full-scale impact tests made by YTI. The CompMechLab helped these associates in product optimization and further development by developing lighting column FE-models with sufficient energy absorbing properties, by fitting the model to obtain similar deceleration curves with real car crash tests, and to provide recommendations concerning the design of new, higher columns. Developed fully 3-D CAD and FE models of different column types featured the simulation of the following nonlinearities: dynamic impact at different vehicle speeds, plasticity in column and vehicle parts, contact interaction between the simulated objects and progressive damage in column laminates. 3-D FE model of the impact car was based on FHWA/NHTSA National Crash Analysis Center prototype including radiator, engine, front and rear suspensions, brake system and many other parts with ability of contact interaction and nonlinearities in material behavior. Prototype design was modified to get approximate similarity with the Peugeot 205 car used in the experiments. Column 3-D FE model includes column stand, reinforced composite laminates and bracket with lanterns (single or double). Al together 216 different materials were used in the FE- model of the car and the lighting column. The resulting simulated deceleration curves allowed calculating Head Injury Criteria – conforming Federal Motor Vehicle Safety Standard – and estimating safety reliability for all columns crush tests. Computed Head Injury Criteria values combined with maximal deceleration values proposed the constructions to be safe ones.
Anup A. Kuldiwar
Finite element techniques have been used to decouple some of the major causes of strip curvature in the finishing stages of a hot strip mill. A plane strain elastic-plastic finite element model (HYPERMESH5.0) is used to predict the direction and severity of strip curvature caused by asymmetrical factors at each pass of the finishing mill. Predictions have been obtained using the elastic-plastic facilities of LS-DYNA Version 960. A full factorial experiment was then designed and performed, using finite element predictions, to identify which asymmetrical factors are most influential to strip curvature and to determine the interactions, between factors. The result show that some of the asymmetrical factors are significant to strip curvature, but their influence depends on the rolling pass. This study will allow the rolling operator to identify which asymmetrical factor may be causing strip curvature and, thus, provide a suitable course of action.
Casey Heydari, Ted Pawela – MSC.Software Corporation, Tim Palmer, Arthur Tang – Engineering Technology Associates, Inc.
Automobile durability and fatigue life prediction depend on road load generation approaches including proving ground testing, laboratory measurement and CAE simulations. Traditionally, the road load simulations are done with ADAMS using rigid body and modal flexible body approaches. With the newly available MD Nastran SOL700 capability, a new approach of using FEA-based flexible body modeling for suspension systems will be an attractive supplemental solution. MD Nastran SOL700 is an LS-DYNA based explicit solution which is capable to correctly simulate FEA flexible body structure, motions, and kinematics while accurately accounting for the material and geometric non-linearity of a suspension system. This paper will focus on the methodology development to enable efficient conversion from an ADAMS model in XML format into MD Nastran SOL700 or LS-DYNA format in ETA’s VPG environment. In the VPG environment, a rigid body suspension model can be easily changed to FEA based flexible body model for either MD Nastran SOL700 or LS-DYNA solution. A demonstration case will also be provided to illustrate the process and approach.
Facundo Del Pin, Grant O. Cook, Jr. – Livermore Software Technology Corporation
The present work discusses a new Fluid Mechanics approach that will be introduced in future versions of LS-DYNA to solve incompressible flows. The objective of this new formulation will be to solve fluid-structure interaction problems using Lagrangian interfaces. In this way large deformations of structures are treated in a more natural fashion making it simpler to define the physical domain. Furthermore the proposed approximation will also deal with free surfaces and breaking waves. In a Lagrangian approach the mesh of the discrete problem moves together with the material particles. Thus for large deformations a very robust and fast re-meshing tool is being created. This tool will be incorporated in the software and all the re-meshing operations will be done automatically. Another key feature of this solver is that given an error estimator the re-meshing steps will also adapt the mesh to provide error control within the fluid solver.
Shokri El Houssini – Daan Engineering s.n.c
During a vehicles frontal crash, passengers jeopardize high acceleration and energy opposite to the mass follow direction of their bodies. This fact causes high injury to the passengers’ whole body; head, neck, chest, and legs. We started thinking of reducing this deceleration effect on passengers during the crash. This is because succeeding in reducing mass deceleration effect on the passengers’ bodies will lead to save passengers form serious injuries. Increasing the length of the front bumper crash boxes was a method to improve the impact energy absorption. However, increasing the geometry (the length of the crash box) of the front bumper assembly will lead to an endless chain of structure subassembly changes. Our methodology works on combing different types of materials and design optimization to control the crash deceleration while maintaining the geometry of the front bumper . This methodology works on absorbing or discharging the energy of the impact before the energy being transmitted in full to the passenger. On other word, we protect the passengers from the excessive energy which is generated by the crash before it reaches them. By having the control over these variables, our vehicles become safer to insure the safety for everyone. This methodology has a high potential to be applied to improve the side impact crash worthiness as well.
S. Heimbs, P. Middendorf – EADS, M. Maier – Institute for Composite Materials (IVW)
An approach for modeling sandwich structures with a Nomex® honeycomb core and phenolic composite faces in the commercial finite element code LS-DYNA with solid elements for the core and shell elements for the thin faces is presented, which accounts for the major sandwich failure modes. Extensive material testing was conducted to determine the parameters for the composite face material model and for the orthotropic honeycomb material model. Strain rate dependency of the material parameters as well as face-to-core debonding phenomena were also investigated and included in the model. In order to design aircraft interior components for dynamic loads, finite element models of lateral and center bins of a widebody aircraft cabin were created and simulations of different load cases were performed. A good correlation to experimental dynamic test results could be achieved.
Torodd Berstad – SINTEF Materials and Chemistry, Odd Sture Hopperstad, Arild H. Clausen – Norwegian University of Science and Technology, Norway, Håvar Ilstad, Bjørn Melve – Statoil ASA
This paper presents an implementation of a material model for thermoplastics. Such materials have a quite complex behavior involving large elastic and plastic deformations, strong viscous and temperature effects, possible true stress softening and deformation-induced anisotropy. The demand of reliable constitutive models for thermoplastics is increasing, and a promising approach is due to Haward and Thackray (1968), who separated the response in two processes: one flow process related to motion of polymer chain segments, and one extendable spring based on the conventional theory of elastomers. Several researchers have extended the Haward and Thackray model, and in particular, the group headed by Boyce at MIT has worked with modeling of polymers for years. The implementation in this paper is mainly based on a paper by Boyce et al. (2000). Recognizing the large elastic deformations in polymers, we have used a framework with a Neo-Hookean hyperelastic material description. The semi-implicit stress update algorithm is as proposed by Moran et al. (1990). Predictions using the implemented model is compared with results from uniaxial tension and compression tests on polypropylene. The agreement is satisfactory in both cases of loading, as the main features of the force-deformation curve and yield stress difference in compression and tension are reproduced by the model.
J.W. Yoon, R.E. Dick – Alcoa Technical Center
Robustness, accuracy and good computational performance for large scale models are some of the salient requirements for general purpose finite element programs. A new one point quadrature shell element that meets these requirements has been previously developed in the works of Cardoso & Yoon (2005). In the theory, the finite element strain-displacement matrices are described in a convective coordinate system for the efficient implementation of a physical stabilization procedure. In order to increase the computational efficiency of the shell element, in this work the resultant-stress equations are formulated by reducing dimensionality to the shell’s mid- surface. In order to improve the simulation accuracy of sheet metal forming simulation utilizing commercial software, the proposed one-point quadrature element and a typical fully integrated element have been implemented to LS-DYNA using the user element interface. In addition, a plane stress yield function (Yld2000-2d, Barlat et al. (2003)) and a new anisotropic model (Yld2004-18p, Barlat et al. (2005)) that accurately describe the anisotropic behavior of aluminum alloy sheets were also implemented to LS-DYNA user material option (UMAT). Several examples including sheet forming are presented to demonstrate the element’s robustness and efficiency and to verify the interface.
Pierre L’Eplattenier, Grant Cook, Cleve Ashcraft, Mike Burger, Art Shapiro – Livermore Software Technology Corporation, Glenn Daehn, Mala Seth – The Ohio State University
A new electromagnetism module is being developed in LD-DYNA for coupled mechanical/thermal/electromagnetic simulations. One of the main applications of this module is Electromagnetic Metal Forming. The physics, numerical methods and capabilities of this new module are briefly presented. This module is then illustrated on different simulations. A first set of simulations corresponds to a ring expansion experiment, which was performed at The Ohio State University, for which the code is compared with experimental results. A second example corresponds to a typical Electromagnetic Metal Forming of a thin metallic sheet.
Alexander Siebert, Gunther Blankenhorn, Karl Schweizerhof – University Karlsruhe, Germany
A numerical investigation of the vibration behavior and the sound of a specific bell is performed and validated by experimental modal analysis. In the numerical simulations a number of modifications of the geometry mimicking or- naments and reliefs is investigated as such ornaments have lead to mistunes in a very popular case in Germany. It is also shown, how the influence of ornaments on the modification of eigenfrequencies can be reduced. The numerical results obtained by eigenvalue analyses as well as transient analyses with LS-DYNA compare very well with the experimental results. It is shown that LS-DYNA- Finite Element analysis can be well used for bell de- sign .
Ning Zhang, Linhuo Shi – Toyoda Gosei North Amercia, Bruce Tzeng – Dynamax, Inc.
Computer Aided Engineering (CAE) has been deployed to help developing effective occupant restraint systems, such as airbags, in automotive industries for decades. Until recently, control volume method, which assumes a uniform pressure and density inside airbag, is still widely adapted in most airbag applications. Control volume method allows use of simple thermodynamic equations to efficiently model airbag. Using control volume method to simulate fully deployed airbags interacting with crash dummies, such as In-Position (IP) simulation, is appropriate. However, with the stringent safety regulations for protecting occupants with widely distributed sizes and sitting positions, as well as the implementation of side and knee airbags, Out-Of-Position (OOP) simulation becomes more and more important for airbag suppliers and OEMs. In OOP simulation, airbag starts to interact with occupants long before it is fully deployed. The non-uniform distribution of gas pressure inside airbag and the highly dynamic characteristics of airbag cushion invalidate the control volume method. To address this issue, fluid-solid interaction (FSI) is implemented in various codes in different forms. The very high speed gas interacts with soft fabric in airbag simulation is quite a challenge for conventional Computational Fluid Dynamic (CFD) codes, and special treatment to deal with this FSI problem should be carefully planned and developed. Arbitrary Lagrangian Eulerian (ALE) approach from LS-DYNA provides a possibility to model this multi-phrase highly dynamic problem. For OOP simulation, the ALE should be computationally efficient with acceptable accuracy. Normally, gap between layers of airbag is about the same order of magnitude of fabric thickness for flat or folded airbag model. To be computationally efficient, the size of Eulerian elements should be much larger than the fabric gap. This introduces the difficulty for code to handle gas-fabric interaction properly. Larger Eulerian element size slows down the gas propagating speed and causes discrepancy between simulations and testing for airbag deployment. Properly use of initial volume fraction definition from LS-DYNA to introduce gas into cushion fabric gap at time zero, can improve the results without using ultra small Eulerian elements for flat airbag model. However, for folded airbag, the application of initial volume fraction is not so successful. In present study, issues using ALE for airbag simulation will be investigated using several simple test cases. Recommendations for further improving the ALE code for airbag OOP simulation are presented.
Arthur B. Shapiro – LSTC
LS-971 has several new features to model the hot stamping process. A thick thermal shell formulation allows modeling a temperature gradient through the thickness of the shell. The new keyword, *MAT_ADD_THERMAL_EXPANSION, allows calculating thermal strains for all the mechanical material models. A new feature has been added to thermal contact which turns off thermal boundary conditions when surfaces come in contact. A new thermal one-way contact algorithm has been added which more accurately models heat transfer between a blank and die. New features have been added to thermal-mechanical contact which allows modeling the coefficients of friction as a function of temperature and thermal contact resistance as a function of interface pressure.
Mark Rentschler, John D. Reid – University of Nebraska
In vivo surgical robot wheels were studied to develop a better wheel design using finite element analysis. A liver material model, derived from component testing, was implemented as a viscoelastic material. LS-DYNA simulation of this testing confirmed the accuracy of the liver material model. This material model was then used as the tissue model to study wheel performance. A helical wheel moving on the liver model was used to replicate laboratory experiments. Drawbar forces required to move the wheel across the liver for various slip ratios produced in simulation showed good agreement with the physical tests. The wheel design was then adjusted in the simulation to study how changes in the wheel diameter and the pitch of the helical tread affected the drawbar force. Results showed that an increased diameter and decreased pitch angle increased drawbar force. These results will be used in future surgical robot wheel designs.
Michael A. Burke, Youn-Seo Roh, Henry H. Fong – Sun Microsystems, Inc.
This paper describes AMD Opteron -based x64 systems of Sun Microsystems(TM), primarily the server (TM) family. Performance and scalability are shown for the refined Neon standard LS-DYNA benchmark problem – for both gigabit Ethernet and Cisco/Topspin(TM) InfiniBand(TM/SM) interconnects. The Sun Fire(TM) X2100 server, which can be easily installed in a Sun Grid Rack System, is seen to be a very attractive solution based on price- performance considerations. A continued effort on improving LS-DYNA performance on Solaris x64 platform is described. A brief mention is made of future benchmark work planned.
Tim Prince, Hisaki Ohara, Nick Meng – Intel Software and Solutions Group
Benchmark performance of a cluster based on the newly introduced 64-Bit Intel® Xeon® Procesessor-based clusters is presented. Car2car and 3cars benchmarks from topcrunch.org are evaluated, using OpenIB based interconnects. Effect of shared memory options under Intel® MPI is evaluated. Improvement from optimizing 3cars P-file decomposition is demonstrated. Intel® Cluster Tools profiler is discussed.
Emily Nutwell, Dylan Thomas – Honda R&D Americas
A recently developed pick-up truck has a unique bed structure which includes an under bed storage system. This truck bed and storage system design is made of sheet molded composite (SMC) material. SMC is a composite material where chopped glass fiber is laid on a poly(vinyl)ester sheet and run through a compaction process. SMC sheets are then loaded into a press to mold the desired part. During the molding process, certain design features such as molded-in ribs can cause the random orientation of the glass fibers to become directional, causing non- homogeneous material properties in the final product. A finite element material model of the SMC material was developed using material tests performed on flat SMC specimens and SMC specimens with molded-in ribs. This paper presents the details of the SMC material model development and application of the model to static and impact strength simulations on the truck bed design. The truck bed design did not include molded-in ribs, as simulations showed these ribs would crack during impact requirement tests. Furthermore, simulation was able to validate the final design prior to test without having to re- work the tooling.
Yvonne D. Murray, Carolyn M. Yeager – Aptek, Inc.
The mixed-mode constitutive driver is a software package that is dedicated to the efficient development, evaluation, and parameter identification (fitting) of material models used in finite element codes. The core driver calculates the stress-strain behavior of material models driven by combinations of strain increments and stress boundary conditions. Graphical user interfaces facilitate selection of the material model constants and desired load histories, and plot model output in two (stress-strain curves compared with test data) and three (yield surfaces) dimensions. Optimization routines fit the material models to test data. Optimization is accomplished by interfacing the driver with the LS-OPT code. The driver complements the performance of finite element codes. Its intended use is to help analysts efficiently fit and evaluate material models, with consistent results, prior to performing large-scale finite element analyses.
V. Ignatkov, S. Klambozki, S. Medvedev, M. Petrushina – UIIP NAS of Belarus
In this paper some modal and vibration properties of turbocompressor elements are studied. Natural frequencies of turbokompressor rotor shaft with turbine and compressor wheels and bearing unit elements are calculated. Their spectrum dependence on the material properties of the elements and on the constructive variants of the bearing unit components are studied. Shape modes of the system are obtained . The vibrations of the system at the maximal angular velocity are estimated. The oscillations of the turbine and compressor blades are found for that angular velocity . The natural frequencies and shape modes of the separate blades of the turbine and compressor are found. The blades response to short pressure pulses are studied. The conditions of resonance are investigated.
S.W. Kirkpatrick, R.T. Bocchieri, R.A. MacNeill, B.D. Peterson – Applied Research Associates, Inc., USA, Fahim Sadek – National Institute of Standards and Technology, USA
The Federal Building and Fire Safety Investigation of the World Trade Center Disaster was recently completed by the National Institute of Standards and Technology (NIST). A critical component of the investigation was to analyze the aircraft impacts into the World Trade Center (WTC) towers to evaluate the impact-induced damage to the towers. This impact damage established initial conditions for the fire dynamics modeling, thermal-structural response, and collapse initiation analyses performed as part of the NIST investigation into the collapse of the WTC towers. This paper presents the development of the WTC tower and aircraft models and associated analysis methodologies used to simulate the aircraft impact response. The analyses performed span the range from laboratory-scale material testing up to the global aircraft impact response of the WTC towers. Simulations were performed at various levels of refinement. Component analyses were performed using small portions of the aircraft and tower. In these analyses, components were modeled with a fine resolution to investigate the details of the initial impact and breakup behavior. Results from the component analyses were used to develop the simulation techniques required for the global analysis of the aircraft impacts. The global impact simulation techniques were aimed at reducing the overall global model size while maintaining fidelity in the impact response. The accuracy of the calculated aircraft impact damage was evaluated by comparison with observed impact damage to the towers.
Kaiping Li, Yang Hu – DaimlerChrysler Corporation
With the continuous improvement of MPI protocols, for example, Lam-MPI, MPICH, etc.., even fast computer hardware and network connections, the applications of MPP technologies in multi-stage stamping simulations for auto industries becomes more and more attractive, not only because of their scalability, but also for their ability to re-use the older equipments without sacrifice the speed of simulations. In this paper, we will present our study results on the MPP version of LS-DYNA in our stamping simulations and our ultimate goal with this technology. Nowadays, in order to reduce operation costs and maintain high quality of products, FEA simulations of stamping processes become de-facto in the auto industries. With the continuous improvement of FEA technology and computer hardware, numerical simulations of multi-stage stamping operations have become a reality. Because the deliverability of simulations is one of our five major quality measurements, we need even faster simulation speed to catch up with new product style changes.
Nielen Stander, Willem Roux – Livermore Software Technology Corporation
An overview of LS-OPT features is given with special emphasis on new features available in LS-OPT Version 3.1. The main features added to Version 3 include discrete optimization, 3-D metamodel plotting, additional statistics features, and a simplification of parameter identification. LS-OPT is now available for MS Windows®.
Dr. Rahul Gupta, Dr. Ajit D. Kelkar – North Carolina A & T State University
The fatality analysis report system of the National Highway Traffic Safety Administration reported that approximately 42,000 people in the United States are killed annually in motor vehicle crashes. Approximately 30 percent of the fatalities are from run-off-the-road crashes involved in collisions with roadside objects. Energy absorbing barriers (EABs) such as concrete median barriers, guardrails, guardrail end treatments, impact attenuators, crash cushions and bridge rails are designed to absorb and dissipate the kinetic energy of run-off-the- road vehicles efficiently. The main purpose of EABs is to increase vehicle occupant survivability while reducing injury levels by smoothly redirecting an errant vehicle to bring it to a controlled stop and to prevent deadly rollover or crossover accidents. Non-linear, three-dimensional, FEA code LS-DYNA is used to perform realistic and predictive virtual crash simulations for analyzing the large-deformation dynamic responses of elastic or inelastic structures using implicit as well as explicit time integration schemes. This paper presents a novel airbag technology, fluid-structure interaction effect based patented EAB designed and tested by the researchers at North Carolina A&T State University primarily for high velocity impacts. Simulation and testing have shown marked improvements compared to the current generation of EABs. The analysis consists of a crash deformation profile, acceleration records at different locations, and energy absorptions by different components.
Daihua Zheng, Wieslaw K. Binienda, Jingyun Cheng, Marcin Staniszewski – The University of Akron
It has been shown by experiments that frictional effects play an important role in the energy absorption of fabrics subjected to ballistic impact. However, the specific role of friction is not well understood and established. In this paper, a detailed finite element model was developed, using LS-DYNA®, to parametrically study the frictional effects during the ballistic impact of a square patch of single-ply 2D tri-axially braided fabric. The individual yarns (bias and axial direction) in the fabric were modeled discretely and considered as a continuum by considering the measured properties of the braided fabric (weave architecture, crimp, yarn cross-section etc.). The friction between yarns at their crossovers and the friction between projectile and fabric were taken into account. The damage of a single yarn model were compared with the experimental data and included in the material model of the fabric. It was shown that the friction contributes to decreasing of the residual velocity of the projectile more quickly than the one without friction. Thus the fabric energy absorption capacity can be increased by 18%. The results from the simulation also indicated that the frictional sliding energy starts to play more important role when the fabric begins to get damage and more movements between axial yarns and braider yarns are involved.
Alexander A. Ryabov, Vladimir I. Romanov, Sergey S. Kukanov, Sergey G. Skurikhin – Joint Stock Company SarovLabs, Russia
The PAT-2 package is designed by Sandia National Laboratories  for the safe transportation of plutonium and/or uranium in small quantities, especially as transported by air. The package consists of an outer container and an inner absorber. The outer container is made of 304 stainless-steel sheet metal. The inner absorber assembly consists of redwood and maplewood layers and is used for decreasing the mechanical loads onto the inner capsule with a radioactive material. The PAT-2 package is resistant to high-speed jet aircraft crash. That was verified by the experiments. The package was tested in several orientations and subjected to impacts at a velocity of >129m/s onto a flat unyielding surface. Some obtained results of the package dynamic deformations are described in . It is also noticed in  that the worst impact orientation could not be proven by the stress analysis before the tests. That’s why it’s very important to conduct a numerical simulation of the package behavior in high-speed impacts to compare the numerical results with the experimental data. Such a numerical expertise opening “an internal deformation world” of the construction behavior allows understanding the weakest and the strongest features of the design and can show the ways on how to improve the structure. It’s also an additional experience of LS-DYNA® applications for such problems as well. The computer model description and the numerical calculations results of the dynamic deformations of the package subjected to top-end, bottom-end, top-corner, bottom-corner and side impacts at a speed of >129 m/s are presented in the paper. Furthermore, U.S. Legislation (U.S. Public Law 100-203) also requires that the foreign shipments of plutonium through U.S. airspace be able to withstand a worst-case aircraft crash, therefore the requirements for packages used for these applications is expected to be even more severe . In accordance with this requirement, the stress analysis of the package at arbitrary impact speed of 200 m/s was performed using the computer model of PAT-2.
F. Grytten, T. Børvik, O.S. Hopperstad, M. Langseth – Norwegian University of Science and Technology
This paper presents numerical simulations of quasi-static perforation of circular AA5083-H116 aluminium plates. The perforation process was analysed with 2D-axisymmetric elements, brick elements and shell elements. Slightly modified versions of the Johnson-Cook constitutive relation and fracture criterion were used in the finite element simulations to model the material behaviour. A factorial design was used to investigate the influence of varying plate thickness, boundary conditions, punch diameter and nose shape. Comparisons between LS-DYNA simulations and experiments were made and good qualitative agreement was in general found. However, some quantitative differences were observed.
Marko Thiele, Heiner Mullerschön – DYNAmore GmbH, Marcel van den Hove and Bernd Mlekusch – AUDI AG
The purpose of this paper is to explore some interesting aspects of optimization for crashworthiness occupant safety applications and to propose optimization strategies for highly nonlinear problems. With the today’s state of technology i t is possible to identify specific load cases and different types of occupants i n the car. System parameters of the restraint system, such as trigger time for seat- belt, airbag and steering column can be adapted to particular load cases. This is referred to an adaptive restraint system. I n the first part of the paper different optimization strategies are discussed and pros and cons are compared. I n addition, a methodology to get a reliable surrogate model using neural networks is introduced. The surrogate model (Meta-Model or Response Surface Model) approximates the relationship between design parameters and a physical response and can be used to visualize and explore the design space. I n the second part the application of the Successive Response Surface Scheme (SRSM) for the optimization of an adaptive restraint system is conducted. For this, several front crash load cases are considered. This is performed using LS- OPT (Stander et al. ) as optimization software and PAM-Crash as solver for the finite element occupant safety simulations. The procedure of generating an advanced meta-model to get an approximation of the global design space using neural networks is demonstrated for this example. Furthermore, the visualization of multi-dimensional meta-models i n two- and three-dimensional design space is illustrated by using the matlab application D-SPEX. The program D-SPEX interfaces with LS-OPT as an advanced optimization and stochastic post-processor.
Bill McLundie – Jaguar and Land Rover, Mike Twelves – Corus Automotive UK, Mike Howe – Jaguar Land Rover IT.
Knowledge-based Engineering (KBE) has been used in industry in for some time. Companies such as Jaguar initially used KBE to automate well-understood, but repetitive, man-intensive engineering issues at the early phases of a programme. These were / are mainly based around geometrical problems (e.g. ergonomic design). Airbus (UK) in particular over the last few years has taken this to a new level by using ICAD as a method of not only generating geometry, but interacting with other existing programmes and creating a method of ‘glueware’ that takes initial input data, and runs through a design and analysis sequence that would normally take human processing much longer to achieve. The next logical step is to control the overall process using a piece of optimization software
Leonard E. Schwer – Schwer Engineering and Consulting Services, Kurt Hacker, Kenneth Poe – Naval Explosive Ordnance Disposal Technology Division
The Naval Explosive Ordnance Disposal Technology Division has a requirement to establish a modeling capability to simulate render safe procedures for unexploded ordnance. To aid in establishing this capability, the Navy has initiated a research and development program that includes modeling studies, research on applicable impact related material parameters, and comparison of the modeling results with experimental results. This paper presents a summary of the progress during the first six months of this effort including a selection of laboratory experiments and their numerical simulation.
Jason Wang, Nicolas Aquelet, Ian Do, Hao Chen – Livermore Software Technology Corporation, Benjamin Tutt – Irvin Aerospace Inc., Mhamed Souli – Laboratoire de Mécanique de Lille
A newly developed approach for tridimensional fluid-structure interaction with a deformable thin porous media is presented under the framework of the LS-DYNA® software. The method presented couples a Arbitrary Lagrange Euler formulation for the fluid dynamics and a updated Lagrangian finite element formulation for the thin porous medium dynamics. The interaction between the fluid and porous medium are handled by a Euler-Lagrange coupling, for which the fluid and structure meshes are superimposed without matching. The coupling force is computed with an Ergun porous flow model. As test case, the method is applied to an anchored air parachute placed in an air stream
Fen Ren, Yinong Shen, Z Cedric Xia – Ford Motor Company, David J. Wynn, Philip Ho – Livermore Software Technology Corporation
Impact marks are the visible damage to the metal surface left by stamping tools sliding across a formed panel. The severity of such impact marks is an important quality measure in part buyoff, particularly for class A panels such as doors, body sides, hoods and deck lids. This paper presents a predictive simulation tool which has been developed to characterize and quantify the impact marks. It is based on the concept of accumulative frictional energy density between the panel/tool interface during a forming cycle. The tool itself provides an indication of the relative severity of the tooling impact on the panel surface, and can be used to fully assess production panel quality during draw development and also help a draw developer seek alternative design if necessary. The simulation tool has been implemented in LS-DYNA and the impact mark can be visualized and animated in LS-PrePost.
H.M. Yang, Raymon Ju – Flotrend Corporation, Taiwan, H. Ouyang, T. Palmer – Engineering Technology Associates, Inc., USA
Consumer products are many times used under extreme use conditions which have the potential to damage a device in a manner such that the internal components become damaged, and non-functioning. Designing engineers must consider these shock, impact and vibration conditions when designing products, as well as the shipping containers or packaging of the product for transport to the end user. In addition, there are many different variations of the impact condition, including height, and angle of impact. Drop Tests are performed to test physical prototypes for such inputs. LS-DYNA analyses can be used to simulate these tests, thereby reducing the number of tests and improving the product design prior to prototype construction. A case study of how process automation within eta/VPG has enabled engineers to consider many different drop test simulation scenarios in an efficient manner will be presented.
Jiang Hua, Xiaomin Cheng, Rajiv Shivpuri – The Ohio State University
During the fabrication of very small or fine hole, usually referred to as micro-hole, technical difficulties often arise due to limitation on the precision capability of tooling systems including those associated with alignment. The present project attempts to develop a new process for piercing micro-hole, using high pressure water beam. In this paper, a numerical model for the micro-hole manufacturing is developed which provides helpful insight into the mechanics of the micro-hole forming process and the tooling design. The ALE (Arbitrary Lagrangian-Eulerian) method of dynamic FEM model is used to simulate water hammer and the water beam penetration into the workpiece material. An experiment for hydro-piercing process is also developed to validate the numerical model. The effects of micro-hole parameters, diameter and workpiece thickness, and water pressure on the micro-hole formation are investigated. It is found that the fracture occur near the die corner in workpiece material and that the pressure increases dramatically when the ratio of hole diameter to thickness is less than 1.
Shivakumara H Shetty, Velayudham Ganesan, Nagesh B L, Jean Louis Duval – ESI Group
The current trend of Product Development Cycle needs to be optimized to meet the growing demand for robustness, quality and fast to market. High competition, mandatory regulations and global norms are forcing the engineers and researchers to evolve with innovative ideas and solutions to meet demands. CAE plays a crucial role in the product development cycle where the FE modelling and simulations are preformed for virtual evaluation of the products. Commercially available CAE tools and software are used for such problems. ESI’s EASi-CRASH application is one of the tools widely used in CAE world mainly by automotive industries. In order to meet such CAE users expectation of fast paced product development, ESI’s Open VTOS (Virtual Try-Out Space) solution provides a platform for achieving the desired productivity and results in the virtual prototyping environment. Visual-Environment (VE) is the major enhancement of EASi-CRASH application. Virtual Prototyping methodology has made significant contribution in enhancing the productivity, reliability, usability and robustness. VE is an integrated suite of solutions, which has different contexts seamlessly linked for Crash and Safety simulation. Visual- Crash DYNA (VCD)-a pre processor for LS-DYNA, Visual-SAFE-an advanced pre-processor for safety features, Visual-Mesh a general purpose mesher, Visual-Viewer (VVI)-a general purpose plotting and simulation application, Visua-Life Nastran (VLN)-a general purpose pre processor for NASTRAN, Visual-Process Executive-an application for process customization and repetitive tasks automation are the contexts to name a few. This paper describes the key modelling features and usefulness of Visual-Environment in Crash and Safety simulation with productivity examples and process automation.
Pramod Rustagi, Ilya Sharapov – Sun Microsystems, Inc.
We use a benchmark dataset of a jet-engine impeller to study the performance characteristics of the LS-DYNA Implicit solver, as a function model size and the number of processors available in the system. We analyze a range of models with an increasing number of fans in the jet-engine impeller, from the smallest model of three fans composed of 300,000 nodes to the largest model of ten fans with 1 Million nodes. The resulting stiffness matrices are of sizes .9 and 3 Million Degrees of Freedom (DOF) respectively. These sizes are typical for today’s LS-DYNA runs, but in the coming five years, model sizes will to grow upwards of 50 Million DOF. In addition, the computational system available at that time will offer much higher degree of parallelism. In this paper we estimate the performance and scalability of large LS-DYNA runs on these future machines.
Clemens-August Thole, Rodrigo Iza-Teran, Rudolph Lorentz, Helmut Schwamborn – Fraunhofer Institute for Algorithms and Scientific Computing
In crash simulation, small changes of the model or boundary conditions may result in substantial changes of the simulation results. For the Neon test case , small variations of the barrier position result in substantial scatter of the intrusion. Detailed investigations of several models have shown that in some cases numerical effects might be responsible for the scatter in the results. In most cases, however, the instable behaviour of the simulation results is caused by bifurcations. These bifurcations result from numerical algorithms or are a feature of the car design. In the Neon model the scatter is a result of the interaction between the axle and the engine block. DIFF-CRASH1 is a tool, which allows one to measure scatter and to trace this scatter back to its origin. It allows the engineer, to understand the mechanisms of propagation and amplification of scatter during the crash itself as a basis for the improvement of the stability of the car design. For this analysis, DIFF-CRASH uses the complete result files of several simulation runs with a fine time resolution of the states. Storing these result files requires a substantial amount of disk space. FEMzip2 allows the reduction of this disk space by a factor of between 5 and 10. One can then store not only key results but the complete result files from optimisation experiments which can also be used for stability analysis. In this paper we discuss the accuracy required by DIFF-CRASH for a precise analysis and its implication on the data compression performance of FEMzip.
Carla McGregor, Reza Vaziri, Anoush Poursartip – The University of British Columbia, Canada, Xinran Xiao, Nancy Johnson – General Motors Corporation
Composite tubular structures are of interest as viable energy absorbing components in vehicular front rail structures to improve crashworthiness. Desirable tools in designing such structures are models capable of simulating damage growth in composite materials. CODAM (COmposite DAMage), which is incorporated into LS- DYNA as a user material model, is a continuum damage mechanics based model for composite materials with physically based input parameters. In this paper, the CODAM model is used to simulate tube crush experiments. It is shown that the damage propagation, fracture morphology and energy absorption predictions correlate well with the experimental results.
Ø. Fyllingen, O.S. Hopperstad, M. Langseth – Norwegian University of Science and Technology
Stochastic simulations of square aluminium tubes of 6060 T6 aluminium alloy subjected to axial crushing have been performed in LS-DYNA and compared to existing experiments. The main variables of the experimental study were the extrusion length, the wall thickness and the impact velocity. Three different buckling modes were observed; progressive buckling, a transition from progressive to global buckling and global buckling. In the present study it has been investigated if it is likely that geometric imperfections modelled by assumed Gaussian random fields can explain the experimentally observed behavior. Variation of the random field parameters by use of a factorial design resulted in variations in especially the buckling modes and consequently the average force.
Tim Lim, Tim Dietrich – Dofasco Inc, Canada
This study uses a design of experiments (DOE) methodology to investigate the sensitivity of springback prediction to various numerical parameter for the Numisheet 2005 cross member (Benchmark II). The parameters investigated are; through thickness integration points (21 Gaussian integration points through the thickness vs. 7), using a static implicit finish in the forming simulation, element size (number of adaptive levels), and coulomb friction. The average effect of these parameters on the resulting springback was then quantified. Overall, it was found that element size and friction have the greatest effect on the predicted springback and that little is gained by using an implicit finish and 21 integration points through the thickness. Possible reasons for this are discussed and it is then stressed that, these results cannot be generally applied to all situations. In other words, the results point to the possibility that some parts (such as this one) are not sensitive to increasing integration points (from 7 to 21) or an implicit finish. It was also found that despite all combinations of numerical parameters, the wall curl on one side of section I of the Benchmark could not be reproduced
Michael M. Chen – U.S. Army Research Laboratory
This paper introduces the very first step on the development of a guided ammunition system. It presents high level physics based simulations of a guided 60-mm projectile system, which intention is to enable the sub-projectile to hit and kill an incoming hostile missile at an extended range within a very limited time frame. The projectile requires a very high muzzle exit velocity in order to carry out the mission. Due to high inertia loads derived from immense breech pressure, understanding the survivability of the projectile system during launch becomes very important. The structural system of interest includes sub-projectile body, sabot, penetrator and electronics. This study focuses on overall projectile system configuration design and addresses the concern of structural integrity among components due to propellant pressure forces. LS-DYNA, a popular transient dynamics finite element program, will be adopted to perform in-bore dynamic analysis. The topology of the projectile was initiated based on gun barrel specifications and certain aerodynamics characteristics. Preliminary structural design of sabot and sub-projectile was then performed with pseudo-static analysis. Subsequently, a 3-D finite element model was created and validated by LS-DYNA explicit dynamic analysis. A characteristic centerline variation of a gun barrel was also taken into account in the study. From simulation results, the muzzle velocity reached only 85% of target value due to 25% overweight of the launch package. However, the projectile system shall survive according to effective stress responses. No material failure is anticipated through in-bore travel. It should be noted that the structural configuration is not optimal as far as the launch package mass is concerned. In the next development phase, rigorous optimization efforts will be made on the projectile system, particularly sabot component.
Mohamed Sahul Hamid, Minoo J. Shah, Jason R. Ridgway, Richard K. Riefe – Delphi Corporation, Troy, MI
In this paper, the design and development of the Delphi Driver Protection Module (DDPM) using a systems and virtual engineering approach is presented. LS-DYNA software tool was used in virtual prototype studies. The DDPM consists of driver side energy absorbing components. The components included in this module are 1) an adaptive Energy Absorbing (EA) steering column, 2) driver air bag, 3) steering wheel, 4) energy absorbing knee bolster, and 5) adjustable pedals. Each individual component was designed virtually and the virtual design was validated with limited test results. Further, a sub-system mini-sled model using a Blak Tuffy dynamic test was developed to study the functioning of the module due to upper torso loading during a crash. The results of this mini sled model were correlated with actual physical tests. For system level response study, a full finite element sled model was developed. The results of these studies using virtual engineering approach are presented.
Edwin L. Fasanella, Richard L. Boitnott – US Army Research Laboratory, VTD, Sotiris Kellas – General Dynamics
During the space shuttle return-to-flight preparations following the Columbia accident, finite element models were needed that could predict the threshold of critical damage to the orbiter’s wing leading edge from ice debris impacts. Hence, an experimental program was initiated to provide crushing data from impacted ice for use in dynamic finite element material models. A high-speed drop tower was configured to capture force time-histories of ice cylinders for impacts up to approximately 100 ft/s. At low velocity, the force-time history depended heavily on the internal crystalline structure of the ice. However, for velocities of 100 ft/s and above, the ice fractured on impact, behaved more like a fluid, and the subsequent force-time history curves were much less dependent on the internal crystalline structure.
Yih-Yih Lin – Hewlett-Packard Company
The standard portable message-passing library MPI is the software tool that drives the parallelism in MPP LS- DYNA. MPI is required to operate in a complex environment: Currently, the major computer architectures include X86, X86_64, and Intel Itanium 2; the major operating systems include Linux, Window, and UNIX; diverse interconnects and switches, using different protocols, are offered by various vendors; and furthermore, in recent years most computer architectures have been evolved into multiple-core from single-core architecture. A well- implemented MPI should achieve the following goals in such a complex environment: (1) supporting all major computer architectures, operating systems, interconnects and switches; (2) being user friendly; (3) being optimized for the performance of the application. In this paper, an in-depth demonstration, using MPP LS-DYNA, on how HP- MPI achieved these goals is presented.
Benjamin Tutt – Irvin Aerospace Inc.
This paper documents the simulation of parachute performance and the role of LS-DYNA in the design of parachutes at Irvin Aerospace Inc. It has long been known that fabric permeability is an important weapon in the arsenal of a parachute designer. In the careful balance of payload rate of descent and parachute stability, the permeability of the parachute material often plays a vital role. The substitution of an impervious material with a highly permeable fabric can turn a parachute from a wandering sloth into a plummeting stabilizer. An accurate consideration of fabric permeability has long eluded the parachute designer. The implementation of a penalty coupling method to describe the interaction of components defined by Eulerian and Lagrangian formulations permits the effect of fabric permeability to be accounted for within the coupling definition. The majority of this paper discusses the implementation of a new porosity algorithm that allows the effect of fabric permeability to be accurately assessed. Correct consideration of material permeability has existed within LS-DYNA for many years, however, these methods were only accurate for the applications originally conceived, namely the airbag. Although both parachute and airbag analyses investigate fabric structures, they differ in many respects, perhaps most significant is that the parachute designer is as concerned about the air that has passed through the parachute as he is with that remaining inside the parachute. Whereas the air that has passed through the airbag is of minimal concern to the automotive engineer. The influence of the air once it has passed through the structural medium can now be assessed within LS-DYNA. This paper provides a level of validation for the technique when considering parachute applications and discusses the importance of this breakthrough to the parachute designer.
Arthur Tang, Wing Lee , Jeanne He – Engineering Technology Associates, Inc., Michigan, C. C. Chen – Dyna Forming Engineering & Technology Sdn. Bhd., Malaysia
The field of sheet metal forming has experienced numerous innovative changes over the past few decades, such as new forming techniques and application of computer technologies. New forming techniques include application of tailor-welded blank, high strength steel forming, hydroforming, press automation and so on. One of the computer technologies is the implementation of Computer Aided Engineering (CAE), such as sheet metal forming simulation. The application of sheet metal forming simulation has been commonly utilized in the stamping industry to predict the forming feasibility of a wide variety of complex components, ranging from aerospace and automotive components to household products. Since the early 1990s, engineers have adopted LS-DYNA, because of its “incremental solution” capabilities, as their solver of choice for sheet metal forming simulations. Through continuous improvement and implementation, the incremental solution has proven to be accurate, reliable and effective. eta/DYNAFORM with its engine driven by the powerful LS-DYNA solver, has over the years been developed and changed from a FEA oriented approach to a process oriented environment that is most suitable for the tool & die industry. It is widely utilized by the tool and die industry to troubleshooting stamping defects, improving tooling design and product quality. Combining the strengths of the solver accuracy, enhanced computer processing speed, and user-friendly graphic user interface (GUI), eta/DYNAFORM has greatly assisted the tool and die industry in shortening tool making lead time and reducing it’s associated cost. As the demand for sheet metal forming simulation technology accelerates, the need for new technology and requirements have also grown rapidly. In this paper, the evolution of LS-DYNA based sheet metal forming simulation technology from a FEA based environment has been changed to a tooling process based application. The key features include Blank Size Engineering (BSE), Die Face Engineering (DFE), Die Structure Analysis (DSA), Springback Compensation Process (SCP) and Tubular Hydroforming (THF).
Zeng-Chan Zhang, Grant O. Cook, Jr. – Livermore Software Technology Corporation
In this paper, we will discuss a new compressible fluid solver (it will be included with the release of LS980) and its fluid/structure coupling strategy. This fluid solver is based upon the Space-Time Conservation Element and Solution Element Method (or the CE/SE method for short), while a quasi-constraint method is used in the fluid/structure couplings.
Mitsuhiro Makino – Fujitsu Limited
In order to get the accurate results, the car models become large and the computational time becomes long. I developed 1.2million elements car models based on NCAC Caravan model, for studying the performance of large number of elements models and large number of CPUs on MPP version of LS-DYNA. 1., The selection of parts of surface to surface contact is sensitive for the large number of CPUs. 2. Soft=2 contact is good performance compared with Soft=1 contact for large number of CPUs
Zhiyuan Shi – ShouGang Steel Group, Guoming Zhu – University of Science and Technology Beijing
Today CAE technology is seeing its rapid development and got widely application in nearly all industries. For metallurgy CAE is also becoming the highlight in many specialties and playing important roles in process optimization and property prediction for R&D of new product development. In this paper a typical example, i.e. thermal-structure coupling simulation analysis on rolling process of H-shape steel with LS-DYNA is introduced.
M. Petrushina, S. Klambozki, O. Tchij – UIIP NAS of Belarus
On SKIF k-1000 supercomputer the temperature fields in turbo-compressor sliding bearings were defined. Dynamic temperature loads were estimated by calculating of heat conduction in the rotor shaft from 600 C heated turbine to the compressor wheel. Conduction and radiation losses were taken into account. The role of friction in heating the contacting parts of the bearing mount assembly was estimated. The calculation of heat conduction through the rotor shaft were made for different exploitation regimes namely for the starting and working regimes and for the lubrication absence conditions. Different constructive shaft variations were used that made it possible to smooth the temperature peaks in thickening ring of the shaft. The temperature fields in bearing mount assembly details were calculated and the thermal stresses were estimated. The role of lubrication was estimated in two ways. In preliminary calculations its influence was estimated by taken into account only its convection and radiation properties as the properties of the environment in the bearing unit. Then the whole process of the oil- bearing unit parts interaction was modeled. The problem was solved in ALE formulation. The gap between rotor shaft and sliding bearing was filled with lubrication. The areas of the ALE- mesh that corresponded to the inflow of the oil was prescribed its initial cool temperature. Then the incoming oil was taken with rotating rotor shaft, the later conducting the heat from the turbine wheel.
Moisey B. Shkolnikov
An integrated warped FEM beam element has been implemented in LS-DYNA and is considered here as a very important beginning. Accounting for warping is a fundamental part of Thin-walled beam theory, having more than three quarters of century history of research and developments, which are still active. Information related to thin- walled beams looks to be very useful to LS-DYNA users, may define steps for further beam FEM elements implementations and wider usage, and therefore some of the information is presented in this paper. The principal idea of the Thin-walled beam theory to represent three-dimensional thin-walled cylindrical shell structures as one- dimensional thin-walled warping beams was very useful in the past and very important today taking advantage of that beams computational efficiency. So far, however, thin-walled beams are modeled mostly using shell FEM elements, which is computationally more expensive
Feixia Pan, Jiansen Zhu, Antti O. Helminen, Ramin Vatanparast – NOKIA Inc.
In this article, the 3 point bending analysis of a mobile phone using LS-DYNA explicit integration method is discussed. Since there are a large number of contact pairs defined in the FEA model, and the FEA model is very large in a 3 point bending analysis of a phone, it is much more convenient to use the explicit method than the implicit method. However, using explicit procedure to a quasi-static analysis requires some special consideration. Since a quasi-static solution, is by definition, a long-time solution. It often requires an excessive number of small time increments. It is computationally impractical to conduct the simulation in its natural time scale. In real analysis, the quasi-static event is artificially accelerated by two approaches to reduce the computation time. One approach is to use mass scaling. Another approach is to increase the loading rate. These two approaches are closely related and should work together. If they are properly used, the speed of the analysis could be increased substantially without severely degrading the quality of the quasi-static solution. We discuss in this article how the loading rate and mass scaling factor affect each other, how to select proper values of these two parameters, and how to use these two approaches in the 3 point bending analysis of a mobile phone.
Dale Dunlap, Joseph Cieslak P.E. – Platform Computing, John Picklo – DaimlerChrysler Corporation
Computer aided engineering (CAE) tools are an important part of the product development lifecycle. These tools are used to perform complex simulation and analyses during the design phase. CAE requires significant computational resources in order to meet the response time requirements of the design engineers that use these applications. The speed and volume of CAE work provides a competitive advantage to the manufacturer by helping to bring products to market faster, reducing the need to build costly prototypes, and by increasing the quality of the end product. This paper documents a comprehensive approach to extending the HPC cluster grid to DaimlerChrysler’s engineering workstations. This approach will allow DCX to transparently make use of idle workstation CPU cycles and thereby significantly increase overall computing power at a fraction of the cost of a comparable dedicated HPC solution. This solution will also provide the foundation for further grid deployment to the DCX infrastructure so that additional benefits can be achieved in the future. By collectively harnessing the latent power of existing resources, Platform and DCX feel it maximizes the value of assets already owned while it gains compute power to accelerate and refine research and analysis, without any impact on the daily usage of these workstation users. The typical utilization of a desktop in the enterprise is about 5-7%, and large enterprises have tens of thousands of desktops. This will provide a cost effective path for increasing computing power while avoiding additional procurements of HPC cpu’s during usage spikes.
K.C. Wood, C. A. Schley, S. Kenny – University of Warwick, IARC, T. Dutton – Dutton Simulation, M. Bloomfield – Land Rover, R. Bardenheier – Inston Ltd, J. R. D. Smith – ARRK Technical Services
This paper investigates sources of performance variability in high velocity testing of automotive crash structures. Sources of variability, or so called noise factors, present in a testing environment, arise from uncertainty in structural properties, joints, boundary conditions and measurement system. A box structure, which is representative of a crash component, is designed and fabricated from a high strength Dual Phase sheet steel. Crush tests are conducted at low and high speed. Such tests intend to validate a component model and material strain rate sensitivity data determined from high speed tensile testing. To support experimental investigations, stochastic modeling is used to investigate the effect of noise factors on crash structure performance variability, and to identify suitable performance measures to validate a component model and material strain rate sensitivity data. The results of the project will enable the measurement of more reliable strain rate sensitivity data for improved crashworthiness predictions of automotive structures.
Liang Xue, Tomasz Wierzbicki – Massachusetts Institute of Technology
Several fracture models are available in the material library of LS-DYNA. This paper is concerned with a newly developed constitutive model that covers the full range of plasticity till the onset of fracture. It is understood that the fracture initiation in uncracked solids is an ultimate result of a complex damage accumulation process. Such damage is induced by plastic deformations. A new damage model is proposed to incorporate the pressure sensitivity and the Lode angle dependence through a nonlinear damage rule using a reference fracture strain on a restricted loading path. The onset of fracture is predicted by integrating incremental damage along the actual loading path. In this cumulative fashion, fracture can be predicted for complex loading paths, which are not limited to the restricted loading in which the pressure is constant. This modified model also incorporates the coupling between the damage and the strain hardening function. The new fracture model is implemented to LS-DYNA as a user defined material subroutine. A series of benchmark tests and simulations have been performed to verify this model. The loading situations of these tests cover a wide range of standard laboratory testing, which include uniaxial tension of a round bar, uniaxial tension of a hollow bar and the three-point bending of a rectangular bar. A remarkable agreement between the experimental and numerical results is achieved.