8th International LS-DYNA Conference

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Detroit, 2004
A Benchmark Study of CAE Sensor Modeling Using LS-DYNA

C. C. Chou, P. Chen, J. Le – Passive Safety R&A, Ford Motor Company, Nasser Tamini – ETA

This paper presents results from a benchmark study of CAE sensor modeling using LS-DYNA. Using the VPG translator, a sensor model was converted from a calibrated RADIOSS model into LS-DYNA input formats for frontal impact simulations carried out in this study. Since two codes have different material laws, element library and functionalities, those deemed to be as closed to RADIOSS were chosen in the translation process. For those that could not be translated directly into LS-DYNA, best engineering judgment was made in selection of appropriate LS- DYNA parameters. Three different frontal impact modes, namely, rigid barrier, pole, and Thatcham offset are simulated in this study. In frontal rigid barrier mode, both 90o barrier and 30o angular impacts are considered. Signals at nine (9) locations were monitored including two sensor signals obtained at the front crash sensor (FCS) and Restraint Control Module (RCM) locations. The quality of CAE data was evaluated using an assessment tool to give objective ratings for comparing results between LS-DYNA and RADIOSS. Sensor signals generated from LS-DYNA were compared with both the RADIOSS and test results. However, only the comparisons with RADIOSS results are presented. By comparing the ratings, LS-DYNA results were, generally speaking, comparable with RADIOSS’ counterparts. Observation of some high frequency response at the onset of acceleration time history obtained at the front crash sensor location at the early stage of this study was improved by LSTC. The study also pointed out areas, i.e. angular and Thatcham impacts, where the LS-DYNA model requires further improvement in the future

A FE Modeling and Validation of Vehicle Rubber Mount Preloading and Impact Response

Sae U. Park, Madhu R. Koka, Kevin R. Thomson, Jeffrey L. Robbins – DaimlerChrysler Corporation

A variety of rubber mounts are being used for vehicles as isolators/dampers between body and frame, on the engine cradle, etc. It has been the prevalent CAE practice in the auto industry to evaluate the mounts’ high-speed vehicle crash response by the means of nonlinear spring/beam models. However, the simplified models carry a risk of generating incomplete and erroneous results, especially under very complex crash loadings due to the absence of component contact and failure criteria. To alleviate the shortcomings of the simplified mounts, this paper presents a FE representation of a detailed vehicle rubber mount coupled with failure criteria and initial bolt wrenching (preloading) using LS-DYNA, as well as test validation of those mounts.

A Mesh-free Analysis of Shell Structures

C. T. Wu, Yong Guo – Livermore Software Technology Corporation, Hui-Ping Wang, Mark E. Botkin – General Motors

A mesh-free formulation based on the Mindlin-Reissner shell theory for geometrical and material nonlinear analysis of shells is presented. In this mesh-free formulation, two projection methods are developed to generate the shell surface using the Lagrangian mesh-free interpolations. The updated Lagrangian theory underlying the co-rotational procedure is adopted for the local strain, stress and internal force updating. A local boundary integration method in conjunction with the selective reduced integration method is introduced to enforce the linear exactness and relieve shear locking. Both nonlinear static and dynamic analysis of shell structures with finite rotations are considered. Several numerical examples are presented to demonstrate the accuracy and applicability of the proposed formulation.

A Model for Process-Based Crash Simulation

O.G. Lademo, T. Berstad, – SINTEF Materials and Chemistry, Norway., T. Tryland – Hydro Aluminium Structures, Norway., T. Furu – Hydro Aluminium R&D, Norway, O.S Hopperstad, M. Langseth – Norwegian University of Science and Technology

Manufacturing of a bumper system from aluminium extrusions often involves series of forming operations performed in the soft W temper condition, and then artificially age-hardening the components to the material’s peak hardness T6 condition. It is perceptible that correct numerical representation of the crash performance of the resulting systems must rely upon a geometry obtained from a model following the process route, i.e. including simulation of all major forming operations. However, the forming operations also result in an inhomogeneous evolution of some internal variables (among others the effective plastic strain) within the shaped components. Here, results from tensile tests reveal that plastic straining in W-temper results in a significant change of the hardening curves (alloy and ageing-dependent increase or decrease in strength) as a function of plastic pre- straining. In addition, the tests revealed that the plastic deformation led to a reduction of the elongation of the T6 specimens. These data were obtained by uniaxial stretching of plates in the W temper to different levels of plastic deformation, sub-sequent artificial ageing to obtain T6 characteristics, machining of uniaxial tensile test coupons and, finally, testing until failure. In the present work, these process effects have been included in a user-defined elasto-viscoplastic constitutive model incorporating a state-of-the-art anisotropic yield criterion, associated flow rule, non-linear isotropic and kinematic hardening rules, a strain-rate hardening rule as well as some ductile fracture criteria. To demonstrate and asses the modelling methodology, a ‘through-process analysis’ of the uniaxial tensile tests is performed. The pre-stretching of the plates in W temper is modelled with shell elements having an initial random Gauss- distributed thickness and stretched to different levels of plastic strain – comparable to the experimental ones – using the explicit solver of LS-DYNA. Then, uniaxial tensile specimens are trimmed from the deformed plates using the trimming option available in LS-DYNA. Next, strain dependent T6 properties are specified, after which the resulting specimens are stretched until instability and failure. Finally, the model assumptions are assessed by comparing engineering stress-strain curves obtained from the simulations and experiments.

A New Concept on Stamping Die Surface Compensation

Li Zhang, Jin Wu, Dajun Zhou – DaimlerChrysler Corporation, XinHai Zhu – Livermore Software Technology Corporation

This paper classifies existing die compensation methods into two general categories, geometry-based method and springforward method. To meet the challenge of increased application of AHSS and its associated severe springback problems, we propose a new concept by using the tooling mesh of design intent as reference during compensation iterations. Incorporation of this concept into these two original methods enhances the efficiency and accuracy of compensated die surface. The enhanced geometric method minimizes the “wrinkle” effect caused by traditional methods done on the blank mesh. The enhanced springforward method improves the convergent rate to a specified tolerance. The proposed scheme can start compensations on a die with either design intent surfaces or already modified surfaces. It is also capable to incorporate actual panel scan data into compensation process to achieve high compensation accuracy.

A Numerical Investigation into HIC and Nij of Children for Forward and Rearward Facing Configurations in a Child Restraint System

William Altenhof, Rita Turchi – University of Windsor

This study explores the various differences in potential for injury in 3-year-old children in the case of a frontal collision. A crash analysis between forward and rearward facing children, both restrained in a five-point child restraint, was performed using numerical simulation methods. This comparison was carried out by conducting numerical simulations of these situations using the criteria outlined in FMVSS 213. The injuries that were assessed included neck and head injury, as those types of injuries can be the most devastating and sometimes fatal. In this study, it was determined that when the 3-year-old Hybrid III dummy model is in a rearward facing position, the child sustains less neck loads and head accelerations than the forward facing dummy model. In other words, a 3- year-old child would sustain lower levels of Neck Injury Criteria (Nij) and Head Injury Criteria (HIC). In fact, the difference in the Nij values is quite significant. In North America, the standard for restraining young children states that for a child under the age of 12 months, the child should be restrained in a child seat facing the rear of the vehicle. After 12 months of age, the child can then face forward. This study has opened the forum to debate if this standard should be reconsidered as to save the lives of thousands of children being injured and dying unnecessarily at the hands of vehicle collisions.

A Process of Decoupling and Developing Optimized Body Structure for Safety Performance

John M. Madakacherry, Martin B. Isaac, Dr. Charles A. Bruggeman – General Motors, Dr. David Eby – CD-Adapco, Dr. Akbar Farahani – ETA, Inc., Dr. Ron C. Averill – Red Cedar Technology

A large class vehicle meeting NCAP front crash and 40-mph 40% Offset Deformable Barrier (ODB) Impact performance was modified and tested to verify a new load path strategy using hydroformed structure and new analytical tools to reduce the mass of the vehicle while meeting the same or better performance as in the original design. The new approach was used for developing the load path strategy of a complex system model by decomposing it into structural subsets. Components in the load path were developed primarily through decoupled structural simulations. The method facilitated evaluation of a large number of design choices compatible with other design constraints. The primary focus of mass reduction was efficiency of load path strategy and exploitation of unique geometrical shapes feasible in a motor compartment rail hydroforming process using new optimization techniques (HEEDS). In addition, the components were made insensitive to prescribed variations to insure robust system level performance. A subset of the new optimized design was incorporated into the ODB test vehicle for verifications. The test vehicle (original architecture and new hydroformed motor compartment structure) had comparable performance though the mass of new vehicle load carrying members was 20% less.

A Study on Shock Wave Propagation Process in the Smooth Blasting Technique

Masahiko Otsuka, Yamato Matsui, Shigeru Itoh – Kumamoto University, Kenji Murata, Yukio Kato – NOF Corporation. Aichi Branch, Taketoyo

Explosives can easily generate high energy and ultra-high pressure. In recent years, research on the advanced technological use of explosives is studied in various places. Here we focus on the Smooth Blasting Technique that is applied for tunnel blasting. This technique is performed to fracture concrete and to reduce the quantity of fragments, while avoiding stress concentration of ground pressure during tunnel blasting. When this technique is used, it is important to know what influence it will have. In our calculation code, the analysis of compressible substances, which cells transform greatly like air, was very difficult. In this study, we use LS-DYNA, an analysis code using a finite-element method. By analyzing the stress state of the air hole circumference, multilayer models such as air, Vinyl Chloride and water are analyzed and it aims to get the propagation process of the shock wave. The Arbitrary Lagrangian Eulerian (ALE) method is based on the arbitrary movement of a reference domain, which additionally to the common material domain and spatial domain, is introduced as a third domain. Three equations of state (EOS) are used in this study. The JWL equation of state is applied for the reaction of the explosive, and has form of a perfect gas equation of state. When the density becomes large, exponential terms modify the perfect gas equation of state. The Mie-Gruneisen equation of state is applied for water and poly vinyl chloride, and the linear polynomial equation of state is applied for air.

A Summary of the Space Shuttle Columbia Tragedy and the Use of LS-DYNA in the Accident Investigation and Return to Flight Efforts

Matthew Melis, Kelly Carney – NASA Glenn Research Center, Jonathan Gabrys – Boeing, Edwin L. Fasanella – US Army Research Laboratory/VTD, Karen H. Lyle – NASA Langley Research Center

On February 1, 2003, the Space Shuttle Columbia broke apart during reentry resulting in loss of 7 crewmembers and craft. For the next several months an extensive investigation of the accident ensued involving a nationwide team of experts from NASA, industry, and academia, spanning dozens of technical disciplines. The Columbia Accident Investigation Board (CAIB), a group of experts assembled to conduct an investigation independent of NASA concluded in August, 2003 that the cause of the loss of Columbia and its crew was a breach in the left wing leading edge Reinforced Carbon-Carbon (RCC) thermal protection system initiated by the impact of thermal insulating foam that had separated from the orbiters external fuel tank 81 seconds into the missions launch. During reentry, this breach allowed superheated air to penetrate behind the leading edge and erode the aluminum structure of the left wing which ultimately led to the breakup of the orbiter. In order to gain a better understanding of the foam impact on the orbiters RCC wing leading edge, a multi-center team of NASA and Boeing impact experts was formed to characterize the foam and RCC materials for impact analysis using LS-DYNA. LS-DYNA predictions were validated with sub-component and full scale tests. LS- DYNA proved to be a valuable asset in supporting both the Columbia Accident Investigation and NASA’s return to flight efforts. This paper summarizes the Columbia Accident and the nearly seven month long investigation that followed. The use of LS-DYNA in this effort is highlighted. Contributions to the investigation and return to flight efforts of the multi-center team consisting of members from NASA Glenn, NASA Langley, and Boeing Philadelphia are covered in detail in papers to follow in these proceedings.

ALE and Fluid Structure Interaction in LS-DYNA

M. Souli – Laboratoire de Mécanique de Lille, J. Wang, I. Do, C. Hao – Livermore Software Technology Corporation

Fluid-structure interactions play an important role in many different types of real-world situations and industrial applications involving large structural deformation and material or geometric nonlinearities. Numerical problems due to element distortions limit the applicability of a Lagrangian description of motion when modeling large deformation processes. An alternative technique is the multi-material Eulerian formulation for which the material flows through a mesh, fixed in space and each element is allowed to contain a mixture of different materials. The method completely avoids element distortions. With an Eulerian-Lagrangian (fluid-structure) coupling algorithm, Eulerian parts may interact with Lagrangian parts in the same model. The Eulerian method is limited by dissipation and dispersion problems associated with the fluxing of mass across element boundaries. In addition, the Eulerian mesh must span the whole active space covering all Lagrangian structures and the spatial range of their motions. This requires a large mesh and thus high computing cost. The multi-material arbitrary Lagrangian-Eulerian (MMALE) method improves upon pure Eulerian formulation by allowing the reference fluid mesh(es) to translate, rotate and deform, thus minimize the amount of flux transport, and reduce mesh size of the reference fluid mesh(es).

An Eulerian Finite Element Model of the Metal Cutting Process

A. Raczy, W. J. Altenhof, A. T. Alpas – University of Windsor

The Eulerian element formulation was employed in the modeling of the orthogonal metal cutting process of commercial purity copper. The constitutive material models elastic-plastic hydrodynamic and Johnson-Cook, were utilized in modeling the workpiece behavior. The capabilities of each model to replicate the experimental chip geometry, stress and strain distributions, and cutting forces, were investigated. The numerical strain distributions, were in good agreement with the experimental strain distribution. The maximum strains of ε p = 8.3 and ε p = 5.6 for the Johnson-Cook material and hydrodynamic material, respectively, occurred in the tool tip region, and were in good correlation with the experimental strain of ε p = 8.1 at this location. The experimental and numerical distributions, all predicted strains of approximately ε p = 3.5 to 3.6 beneath the machined surface and adjacent to the rake face. The stress distributions in both of the investigated materials were noticeable different. The Johnson-Cook model showed a stress increase of up to 425 MPa in the primary deformation zone, while the hydrodynamic model predicted increased stresses of 380 MPa in the secondary deformation zone. The hydrodynamic stress distribution was more consistent with experimental findings, which similarly showed a stress increase, up to 360 MPa, in the secondary deformation zone. The maximum stress in the hydrodynamic material (410 MPa) and in the Johnson-Cook material (438 MPa) were located at the tool tip, and showed good correlation to the maximum experimental stress of 422 MPa, also occurring at the tool tip. The sizes of both the primary deformation zone (350 μm), and the secondary deformation zone (50 μm) predicted by the hydrodynamic and Johnson-Cook material models were in agreement with the experimental observations. The steady state cutting force prediction of the hydrodynamic material was 1332 N, and was within 13% of the experimental findings. The numerical–experimental correlations indicate the Eulerian finite element approach is an effective way of modeling the metal cutting process.

An Evaluation of Active Knee Bolsters

Zane Z. Yang – Delphi Corporation

In the present paper, the impact between an active knee bolster system and occupant knees has been studied using finite element analysis. The active knee bolster system consisted of an inflatable molding part and a pair of EA supporting brackets. Also included in the FEA model was the entire vehicle cockpit. Both driver-side and passenger- side occupants were considered. The active knee bolster FEA model was first validated by test data including kinematics and femur loads. The performance of active knee bolsters was then compared with that of conventional structural knee bolsters

An Investigation of Structural Optimization in Crashworthiness Design Using a Stochastic Approach

Larsgunnar Nilsson, Marcus Redhe – Engineering Research Nordic AB, Sweden

In this paper the Response Surface Methodology (RSM) and the Stochastic Optimization (SO) are compared with regard to their efficiency and applicability in crashworthiness design. Optimization of simple analytic expressions and optimization of a front rail structure are application used in order to assess the respective qualities of both methods. A low detailed vehicle structure is optimized to demonstrate the applicability of the methods in engineering practice. The investigations reveal that RSM is favoured compared to SO for less than 10-15 design variables. A novel zooming method is proposed for SO, which improve its convergence behaviour. A combination of both the RSM and the SO is efficient. Stochastic Optimization can be used in order to determine an appropriate starting design for an RSM optimization, which continues the optimization. Two examples are investigated using this combined method.

Application of FEA in Stamping Auto Underbody Parts

Yuyuan Wang, Marcel Pillon, Ron Ouellette, Chris Pitre, John Laporte – Canadian Engineering and Tool

The complex auto underbody components need a long process of die design and tryout, some times need several to hundred times of costly trial-and-error to get required stamping parts. It is very critical to the die design how to decide and evaluate the die shapes of each forming stage and how to distribute the deformations between preform(s) and form for multi-stage forming. Combination of simulations for each forming stage using Dynaform and shape design using Catia can reduce the time and cost of die tryout, and make the die design optimization possible. The stampability of the part can be evaluated. The optimized die shapes and deformation distribution can be obtained. The main forming failures, such as wrinkles/double metals and cracks can be solved at die design stage. This paper attempts to show some applications of simulation techniques combined with shape design in the die design.

Application of LS-DYNA in Identifying Critical Stresses Around Dowel Bars

Samir N. Shoukry, Gergis W. William, Mourad Riad – West Virginia University

A detailed 3D Finite Element (3DFE) Model is developed to examine the triaxial state of contact stress that develops around the dowel bars due to both traffic and thermal loads. Dowel bars are modeled using 8-node solid brick elements. Sliding interfaces with friction that permit separation are modeled along the full cylindrical surface between each dowel and the surrounding concrete. The model results are validated through comparison with laboratory measured strains in dowel jointed concrete specimens. The model results reveal that under the standard axle load, tensile stresses of magnitude sufficient to initiate localized concrete failure may develop in the concrete surrounding the loaded dowel. Such stresses are responsible for initiating cracks in the concrete that lead to the rapid joint deterioration.


K. Lyle – NASA Langley Research Center, Hampton VA, E. Fasanella – ARL-VTD Langley Research Center, Hampton VA, M. Melis and K. Carney- NASA Glenn Research Center, Cleveland OH, J. Gabrys -The Boeing Company, Philadelphia PA

The Space Shuttle Columbia Accident Investigation Board (CAIB) made several recommendations for improving the NASA Space Shuttle Program. An extensive experimental and analytical program has been developed to address two recommendations related to structural impact analysis. The objective of the present work is to demonstrate the application of probabilistic analysis to assess the effect of uncertainties on debris impacts on Space Shuttle Reinforced Carbon-Carbon (RCC) panels. The probabilistic analysis is used to identify the material modeling parameters controlling the uncertainty. A comparison of the finite element results with limited experimental data provided confidence that the simulations were adequately representing the global response of the material. Five input parameters were identified as significantly controlling the response.

Benefits of Scalable Server with Global Addressable Memory for Crash Simulation

Christian Tanasescu, Nick Meng – SGI Inc.

A wide variety of industries rely on mechanical computer-aided engineering (CAE) to improve design quality, reduce design-cycle time, and control costs. In designing automobiles, the manufacturers must meet different government regulations for vehicle safety. The maturity of Explicit Finite Element methods and the increasing computational power of today’s computers have allowed the automotive industry to incorporate the Crash simulation technology in the critical path of the design process. As the application of Crash simulation moves from the component level analysis to the system level, the complexity and the size of the models increase continuously. By combining the capabilities of Intel® Itanium® 2 processors, the open-source Linux® operating system, and SGI® NUMAlink(tm) technology, the SGI Altix family of servers and superclusters with Global Addressable Memory (GAM) is uniquely able to meet the needs of advanced CAE simulation for product development. This paper will outline the features and benefits of using SGI Altix systems with Itanium® 2 processors running LS-DYNA. With the dramatic increase of the price performance of modern high performance computers, the model sizes of car crash and metal stamping simulations have been constantly increasing in recent years. Nowadays, a 1 Million element model is a common case. For large models, highly scalable computers and software play crucial roles in reducing turnaround time for simulations. The combination of the domain decomposition based LS-DYNA and the highly scalable SGI cc-NUMA system is an ideal solution for reducing simulation turnaround time. After briefly introducing the SGI cc-NUMA architecture and the benefits for scalable applications like LS-DYNA, based on recent performance data on the SGI Altix family of systems, we will address the simulation grid concept enabled by a large shared-memory architecture like the SGI Altix 3700. This aims at making the workflow more efficient, not only improving the solver performance. Multi-terabyte datasets can be loaded entirely into memory and operated upon without disk-swapping. In addition, expanding the processing paradigm with I/O and graphics pipes connected directly to the large memory, results in dramatically improved performance and foster collaborative engineering.

Blast Impact on Aluminum Foam Composite Sandwich Panels

Rajan Sriram, Uday K. Vaidya – The University of Alabama at Birmingham

Sandwich aluminum foam structures are being considered for energy absorption applications, crashworthiness, protection of transformer housings, and structural safety. Blast loading is one such phenomenon that is a potential threat to such structures. This study examines LS-DYNA modeling for aluminum foam sandwich composites subjected to blast loads. The sandwich composite was designed using polymer composite facesheets and aluminum foam as core. The core was modeled using material model 126 (*MAT_MODIFIED_HONEYCOMB). The facesheets were modeled using material model 59 (*MAT_COMPOSITE_FAILURE_SOLID_MODEL) and material model 161 (*MAT_COMPOSITE_MSE). 1 point corotational solid element formulation was used for the core and constant stress solid element formulation was used for the facesheets. LS-DYNA implementation of CONWEP blast equations (*LOAD_BLAST) was used to apply the blast load. The box design was evaluated using simulation and iterated until similar performance was achieved. The results were used to predict the modes of failure and energy absorption phenomenon. The simulation was also performed for different dimensions of box having different curvatures. The paper discusses details of the LS-DYNA simulation work and the parametric studies for the aluminum foam sandwich constructions.

Computer Simulated and Experimental Verification of Tooling for Progressive Deep Drawing.

Peter Kostka, Peter Cekan – Slovak University of Technology in Bratislava

The ability to predict different process conditions in deep drawing is essential for die face designers, tooling, stamping and manufacturing engineers. These predictions in turn affect the speed, accuracy and cost of the final produced product. This paper briefly discusses the possibilities of controlling the blankholder pressure distribution and shows some computer simulations done in DYNAFORM, with the results being experimentally verified with tooling designed by the authors.

Crashworthiness Design of Vehicle Structures via Equivalent Mechanism Approximations

Karim Hamza, Kazuhiro Saitou – University of Michigan

A new method for crashworthiness optimization of vehicle structures is presented. In the new method, early design exploration is done by the optimization of an equivalent mechanism approximating a vehicle structure. An equivalent mechanism (EM) is a network of rigid bodies connected by prismatic and revolute joints with special nonlinear springs. These springs are tuned to mimic the force-displacement characteristics of thin-walled beams often found in the vehicle body structures. The EM models can be regarded as a super-set of lumped models and thus they are capable of providing better insight to the design issues. Proper selection of the nonlinear spring parameters is essential to successful implementation of the EM models. Identification of the spring parameters involves pre-compilation of databases of the crash characteristics of frequently used structures via LS-DYNA simulations. The pre-compiled databases and EM models are then used in the initial design phase in order to explore the crash deformation patterns and identify the good crash mode (CM). Once the good crash mode is identified, it becomes the target for detailed design stage which uses higher accuracy LS-DYNA models of the vehicle structures. A case study involving design optimization of the mid and lower rails of a vehicle subjected to frontal crash test conditions is presented. The case study demonstrates the effectiveness of the proposed method.

Curved Barrier Impact of a NASCAR Series Stock Car

Eric A. Nelson, Li Hong – Altair Engineering

A detailed finite element model of a NASCAR Series stock car has been developed by Altair Engineering and used to study a curved barrier impact. This paper will review some of NASCAR’s capabilities in the area of motor sports safety research and provide an overview of a study that has been performed by Altair Engineering. Specifically, the author will compare and contrast results from a curved barrier impact in 3 different scenarios: • Controlled full vehicle crash test • On-track incident with very similar impact conditions • Detailed finite element analysis using LS-DYNA

Determination of Optimal Cutting Conditions in Orthogonal Metal Cutting Using LS-DYNA with Design of Experiments Approach.

David P. Masillamani, Jack Chessa – University of Texas at El Paso

Optimal selections of cutting conditions contribute significantly to the increase in productivity and reduction in costs of machining processes. The main objective of the present paper is to explore the resultant temperature formed due to complicated interactions and between rake angle, depth of cut and cutting speed. Finite element simulations using LS-DYNA is used as a numerical experiment in the construction of a Design of Experiment (DOE) empirical model of orthogonal machining process. This DOE model is then used to study the temperature formation in the work piece with respect to parameters such as speed, depth of cut and rake angle. The results are also compared with experimental results which have been done already.

Determining the MPP LS-DYNA Communication and Computation Costs with the 3-Vehicle Collision Model and the Infiniband Interconnect

Yih-Yih Lin – Hewlett-Packard Company

The least square error approach applied to LS-DYNA communication and computation costs for the Neon model was shown previously by this author to be useful in predicting performance on a given interconnect of known ping- pong latency and bandwidth, and both Gigabit Ethernet and HyperFabric 2 results were presented. In this paper, this prediction method is applied to a much larger public-domain crash model, the 3-vehicle collision model, to determine communication and computation costs for models representative of the most demanding requirements. Furthermore, the result is verified against the new, high-speed low- latency Infiniband interconnect. Users of this method may perform trade-off analysis for optimum hardware configuration decisions without the need for extensive benchmark testing.

Development of a Hybrid Energy Absorbing Reusable Terminal (HEART) Using Finite Element Modeling in LS-DYNA for Roadside Safety Applications

Nauman M. Sheikh, Dean C. Alberson, D. Lance Bullard – Texas Transportation Institute

The Hybrid Energy Absorbing Reusable Terminal (HEART) is a newly developed crash cushion or an end terminal to be used in highway safety applications that will mitigate injuries to occupants of errant vehicles. The HEART is composed of corrugated plates of High Molecular Weight/High-Density Polyethylene (HMW/HDPE), supported on steel diaphragms, which slide on a fixed rail. Kinetic energy from errant vehicles is converted to other energy forms through the folding and deformation of HDPE material. Many previous designs utilize the plastic or permanent deformation of plastics or steels to accomplish this goal. However, HEART is a reusable and self- restoring crash cushion, and therefore has a major cost advantage over the conventional crash cushion designs. HEART has been designed and optimized through an extensive use of finite element modeling. The objective of this paper is to present the finite element modeling and simulation approach adopted to arrive at the final design of the HEART cushion. In order to meet the National Cooperative Highway Research Program (NCHRP) Report 350 guidelines, all roadside safety devices need to pass the report’s requirements from an 820 Kg and a 2000 Kg vehicle impacting at 100 Km/h. For HEART to meet the NCHRP Report 350 evaluation criteria, a large number of design parameters were investigated. Among these were the thickness of the HDPE plates, the height of the plates, the length of the plates between two consecutive steel diaphragms, etc. Initially, simple finite element models were developed using beam elements as HDPE plates in LS-DYNA. A large number of configurations were tested with these simple models to gain an insight to the problem and to narrow down the number of parameters. Later on, detailed finite element models with shell elements as HDPE plates were developed to come up with the final configuration of the device. HEART crash cushion has passed the full-scale test requirements in accordance with guidelines presented in NCHRP Report 350. Development of the HEART cushion is a good example of the use of finite element analysis as a tool for analysis, design and optimization of roadside safety devices.

Development of an LS-DYNA Model of an ATR42-300 Aircraft for Crash Simulation

Karen E. Jackson, Edwin L. Fasanella – U.S. Army Research Laboratory

This paper describes the development of an LS-DYNA simulation of a vertical drop test of an ATR42-300 twin- turboprop high-wing commuter-class airplane. A 30-ft/s drop test of this aircraft was performed onto a concrete impact surface at the FAA Technical Center on July 30, 2003. The purpose of the test was to evaluate the structural response of a commuter category aircraft when subjected to a severe, but survivable, impact. The aircraft was configured with crew and passenger seats, anthropomorphic test dummies, forward and aft luggage, instrumentation, and other ballast. The wings were filled with approximately 8,700 lb. of water to represent the fuel and the aircraft weighed a total of 33,200 lb. The model, which consisted of 57,643 nodes and 62,979 elements, was developed from direct measurements of the airframe geometry. The seats, dummies, luggage, fuel, and other ballast were represented using concentrated masses. Comparisons were made of the structural deformation and failure behavior of the airframe, as well as selected acceleration time history responses.

Development of Shipping Package Drop Analysis Capability at Westinghouse

J. F. Staples – Westinghouse Electric Company LLC1, M. Pitzer, P. A. DuBois – Hermes Engineering

Westinghouse Electric Company LLC1 is currently developing a new shipping package for transporting nuclear fuel to customer sites. This new design is designated as the TravellerTM shipping package.2 One of the many licensing requirements for the Traveller package is to demonstrate it will always maintain the fuel assembly in a (nuclear) non-critical configuration after being dropped from 9 meters onto an unyielding surface and from 1 meter onto a 15 mm diameter pin. In meeting these regulations, package orientation(s) which will most damage: 1. the fuel assembly; and, 2. the shipping package must be considered. Westinghouse began the Traveller design effort with a need to supplement in-house analytical capability with experienced LS-DYNA consultants. However, the Traveller analysis was not simply “handed off.” Rather, a Westinghouse analyst worked closely with these consultants. This close interaction resulted in a shipping package model which included all features relevant to crashworthiness and correctly represented the final design. The resulting model was instrumental in the success of the drop tests and licensing efforts.

Drop Simulation for Portable Electronic Products

Raymon Ju, Brian Hsiao – Flotrend Co., Taiwan

The portable electronic devices are becoming smaller and lighter in recent years, and hence these products are easily damaged under the drop and impact conditions. Traditionally, manufacturers must have lots of mockups and samples to simulate the impact behavior through experiment. To minimize the development period and the try-and- error costs, ODMs in Taiwan begin to predict the impact behavior by LS-DYNA. For ODMs who want to establish CAE capability, there are two main challenges: (1) First challenge is to determine the opportune moment to introduce the CAE tools, which also implies the traditional design flow should be rearranged. (2) The maximum dimension of portable electronic devices is usually less than 30 cm, so mechanism features are relative small and difficult to build up a complete FEM model. The main theme of this present is to provide a prediction about drop behavior of the portable electronic products in the early design stage and verified with the experiment.

Dynamic FE Analysis of the High-Speed Planetary-Motion Mixer UM-500

Alexey I. Borovkov, Vladimir A. Palmov, Dmitriy S. Mikhaluk, Denis V. Shevchenko – St.Petersburg State Polytechnical University,

In the current paper the results of finite element non-linear mechanical analysis of the energy-saving high-speed planetary-motion mixer UM-500 are presented. The mixer is a system consisting of two milling chambers partly filled with substance to be milled. Milling chambers are in compound motion: rotation about vertical central axis and self-rotation about moving sloping axes. To perform dynamic analysis detailed finite element model is created based on CAD model. Finite element model considers nearly all features of the real construction. By means of LS- DYNA the detailed finite element analysis of dynamic non-linear process of mixer takeoff out of the casing in the result of emergency situation is performed with use of elasto-plastic material model with strain-based failure crite- rion. Dynamic analysis of the rigid-body motion stability of the mixer at speed-up regime is carried out for simpli- fied mathematical models

Effect of Triggering Mechanism on the Load-Displacement Response and Folding Pattern of Square Aluminum Tubes

H. El-Hage, N. Zamani – University of Windsor, Canada, P. K. Mallick – University of Michigan-Dearborn, USA

A systematic numerical investigation of the effect of triggering mechanism on the load-displacement characteristics and lobe formation of square aluminum tubes subjected to quasi-static axial compressive load is presented. Among the physical triggering mechanisms considered were chamfering, drilled holes, geometric imperfection and combinations thereof. The effect of corner radius was also considered. This study has shown that the triggering mechanism controls the load-displacement response as well as the folding pattern. Even though the folding initiation force varies significantly with triggering mechanism, the mean load does not vary greatly. The load- displacement response does not depend appreciably on the corner radius; however, the folding initiation force is lower when a rounded corner is used instead of sharp corners. The folding pattern is also influenced by the corner radius.

Effects of Pre-Pressurization on Plastic Deformation of Blast-Loaded Square Aluminum Plates

R.L. Veldman, C. Clum, J. Folkert – Hope College, J. Ari-Gur – Western Michigan University

The effects of static pre-pressurization on the blast-induced deformation of square aluminum plates were studied both experimentally and numerically. In this study, small (0.152 x 0.152 x 0.0016 meter) clamped plates were used as a basic model of the fuselage skin of a commercial aircraft. Both un-pressurized and pre-pressurized plates (static pressure of 62.1 KPa (9.0 psi)) were considered to simulate the minimum and maximum in-flight loads experienced by a commercial aircraft due to cabin pressurization. This work extends previous research on blast loading of plates to incorporate the effects of pre-pressurization. Experimentally, a vacuum vessel system was used to apply a pressure differential to the test plate. Bare spherical explosive charges of C4 were then detonated at fixed distances from the plate. The permanent plate deformations were measured for twenty-four explosive tests that considered four different blast load cases. In addition to the experimental work, numerical predictions of the permanent plate deformations were determined using finite element analysis and the commercial software ANSYS/LS-DYNA. A comparison of plate deformations determined experimentally with those predicted with the finite element method shows good correlation. For the four explosive load cases studied, no significant change in permanent plate deformations was observed as static pre- pressurization increased from 0.0 kPa to 62.1 kPa.

Energy Absorbing Sandwich Structures Under Blast Loading

Dong Kwan (David) Lee, Brendan J. O’Toole – University of Nevada, Las Vegas

A recent experimental study at the Army Research Laboratories shows that flat panels with various foam or honeycomb faceplates transferred more energy to a structure under blast loading relative to a structure without an energy absorbing faceplate. Ideally, the foam or honeycomb material should transfer less energy to the structure since it absorbs energy while it deforms plastically. Non-uniform deformation of the energy absorbing material may lead to increased pressure on the panel, causing kinetic energy transfer to the plate. One objective of this work is to simulate the non-uniform response of the honeycomb panel subject to blast loading. Most of the work involves an investigation into the optimum design of the honeycomb structure for energy absorption during blast loading. In this paper, only a square-celled honeycomb structure is studied. Variables under investigation for this paper are the core and face sheet thicknesses of the honeycomb sandwich structure. Results of a DOE study are attained, which evaluate the relative contribution of panel variables to energy absorption. Also, the results of a preliminary optimization study are discussed along with some of problems faced during this study.

Experiences with LS-DYNA Implicit MPP

Cleve Ashcraft, Roger Grimes, Bradley Maker – Livermore Software Technology Corporation

Explosive Welding of Light Weight Metal Sheets

Yamato MATSUI , Masahiko OTSUKA, Takeshi HINATA, Shigeru ITOH – Kumamoto University, Erik CARTON – TNO-Prins Maurits Laboratory

The technique of explosive line welding is one of the processing techniques and it can connect similar and dissimilar metal sheets using large energy of explosive during very short time. In this study we try to weld lightweight metal sheets by experiment and work on the numerical simulation concerning a series of the phenomenon. Materials involved are aluminum alloys Al5052-O, 6061T6 and 6M83, magnesium alloy AZ31B-O and commercially pure titanium TP270C. After welding samples were taken to perform shear strength test and the welding interface was analyzed using optical microscopy. The strength test indicates a remarkable good bonding between similar welded metals. Particularly, the use of line welding shows a high strength to explosive mass ratio, making it a good candidate to be scaled up and used in commercial applications.

Fast New Methodology for Regulatory Test Simulation

Velayudham Ganesan, David Piesko, Jean-Louis Duval – ESI Group

Preparing a simulation model for a crashworthiness or occupant safety regulatory test is often a time consuming task. This paper describes a new methodology that significantly reduces this modeling time, down to minutes. Using predefined FMVSS standards, EASi-Process allows users to access ready made test templates for common runs (such as FMVSS 201, 208, 581…). With the integration of EASi-Process, EASi-CRASH DYNA, premier pre and post processor for multi-body and finite element occupant safety simulations using LS-DYNA, allows the user to select the type of test to perform and the structure to perform it on, and the technology takes care of the rest. This technology, combined with EASi-CRASH DYNA, has proven to have dramatic benefits regarding cost and productivity for engineers and the enterprise.

FE Analysis of Contact Interaction Between Rigid Ball and Woven Structure in Impact Process

Alexey I. Borovkov, Igor B. Voinov – St.Petersburg State Polytechnical University

The current paper presents the results of finite element solution of the problems simulating contact interaction between woven structures and striker in the form of rigid ball. The woven structure is represented by a great number of the fibers braided in such way that each of them can come into contact interaction with others. In this paper the analysis results for ball impact direction effect on the woven structure dumping properties was demonstrated. For simulation of the impact process and subsequent multiple contact interaction between woven structure fibers FE mesh containing about 1 million degrees of freedom was used. The efficiency of contact algorithm realization in finite element software LS-DYNA is visually presented. The zone with largest contact pressure and redistribution of contact interaction zone in impact process was analyzed

FEA – Calculation of the Hydroforming Process with LS-DYNA

Michael Keigler, Herbert Bauer – Aalen University, Germany, David K. Harrison, Anjali K. M. De Silva – Glasgow Caledonian University, United Kingdom

The automotive industry is constantly searching for product improvements concerning weight reduction and the need for corrosion resistance. Currently aluminium alloys are of special interest because of their low density of 2.76 g/cm3, and good corrosion resistance. The disadvantage of aluminium alloys is poor formability in comparison to steel. Therefore, new forming methods are demanded such as the “tube hydroforming” process, which has been reasonably successful in creating complex parts in aluminium alloys. This process involves the concurrent pressurization and axial compression of a tube, causing the material of the tube to flow into a die cavity, achieving the form of the final component shape. Lightweight and complex forms of aluminium components have been achieved successfully, when the process parameters are calculated and controlled accurately. Due to its various shaping and design possibilities, the hydroforming process has been used for more than 10 years in the automotive industry for the production of complex carrier structure units. The requirements e.g. the shaping possibilities, respectively, the design space of unit geometry, the expansion relationship, as well as the maximum plastic deformation possibility has risen constantly over that time. This requires ever larger efforts to fulfil these requirements under the compliance of fixed time and cost goals. The contents of this work are the task of the FEA- Simulation of the hydroforming process. It consists in a general feasibility study for the forming behaviour of the semi-finished product and/or the tools. Due to the complex connections of the process influence parameters the non- linear finite elements (LS-DYNA) offers the condition to fulfil these requirements, in particular regarding plausibility check, general feasibility as well as adjusting quality and tolerance field promises (formation of wrinkles, springback, form and position tolerances). A quality increase can additionally be derived accompanying the increase of manufacturing security for series production by the evaluation of the manufacturing simulation.

FEA – Simulation of Bending Processes with LS-DYNA

Peter Gantner, Herbert Bauer – Aalen University, Germany, David K. Harrison, Anjali K. M. De Silva – Glasgow Caledonian University, United Kingdom

Over the past few years new car body concepts have space frame structures. The consequent application of space frames results in a reduction of weight, fuel consumption, and costs of a body while maintaining a high safety standard. These structures consist mainly of closed profiles and hydroformed components. Prior to the hydroforming process, the profiles are usually pre-bent. The bending of tubes is a crucial step in the hydroforming process chain. For a successful hydroforming the bending demands high precision, reproducibility, and process reliability. These bending operations are frequently performed with parameters which are already on their limit. For the design of hydroformed components it is unavoidable to ensure all process steps by means of FEA (Finite Element Analysis) – simulation. Especially for a precise prediction of the feasibility of the bending process and the subsequent process steps it is necessary to consider all parameters and tools (e.g. mandrel) in the simulation. This results in very complex simulation models which make great demands on the simulation programs concerning precision, contact and friction. The contents of this paper deals with the finite element simulation of complex bending processes by using the non- linear simulation program LS-DYNA. In the first part of the paper the simulation of the Rotary Draw Bending with a mandrel is shown by means of a practical component and the results from simulation are compared and validated with experiments. In the second part the new Free-Bending technique is introduced by an example. Both bending techniques offer new possibilities and application ranges in the field of hydroforming.

FEM for Impact Energy Absorption with Safety Plastic

Iulian Lupea, Joel Cormier, Sital Shah – The Oakwood Group

For the engineering design process to benefit from finite element modeling (FEM), it must adequately represent any condition being studied. This paper presents methodologies for using the LS-DYNA non-linear finite element solver to model a patented energy absorbing technology called SafetyPlastic®. SafetyPlastic® offers a performance, cost, and mass competitive energy management solution, and has been embraced by the automotive industry in both head and side impact occupant protection applications. It is characterized by a connected plurality of structural recesses that repeatedly give resistance, and then buckle when impacted. Due to the nature of SafetyPlastic® and its preferred manufacturing method, a somewhat unique FEM challenge presents itself. The paper provides details related to: • Modeling the strain rate dependent polymeric materials used in SafetyPlastic® • Using a proper mesh size; • Specification of the mesh pattern suitable for the assumptions made when manually inputting thickness profile; • Predicting the wall thickness profile for thermoformed designs via FEM with T-SIM® software; • Transferring and mapping data between T-SIM® and LS-DYNA for FEM; • Selecting the proper responses to evaluate the FEM versus experiment results; • Validating the FEM via quasi static and dynamic impacts with a flat plate; • Validating the FEM via dynamic impacts with a free motion headform; • Assessing the correlation of FEM with experimental results; • Optimizing the size and shape of recesses to promote annular buckling. The data presented show that FEM with LS-DYNA can be performed today with a degree of accuracy that will aid upfront SafetyPlastic® design. This leads to the prospect of conducting optimization studies via design of experiments or otherwise without prototype tooling expenses. However, there is room to improve the overall synchronization of a simulated SafetyPlastic® impact response with a real one. Work to refine and better the FEM methodology is an ongoing effort.

Finite Element Analysis of Unanchored Structures Subjected to Seismic Excitation

Sreten Mastilovic – Bechtel SAIC Company, LLC

The objective of this analysis is threefold: (1) to determine the residual stress distribution in two unanchored structures, the waste package and drip shield, subjected to seismic excitation; (2) to estimate the extent and spatial distribution of the area of the two structures for which the residual first principal stress exceeds certain limits; (3) to determine whether or not separation of interlocking drip shield segments occurs during the vibratory ground motion.

Finite Element Modeling of Material Damage in Axially- Loaded Aluminum Tubes with Circular Hole Discontinuities

Bryan Arnold, William Altenhof – University of Windsor

Finite element simulations of the axial crushing of extruded aluminum tube structures were conducted using LS-DYNA in order to investigate their load management and energy absorption characteristics. The structures under consideration were made from aluminum alloy 6063-T5 and contained dual centrally located circular hole discontinuities. The results of the finite element simulations are compared to the results of quasi-static experimental crush tests conducted on structures of similar nominal geometry and material properties. Due to the presence of significant cracking and splitting in the crushing modes observed during the experimental crush testing, a material model employing damage mechanics was assigned to the structure models. This material model was calibrated using the experimental crush testing results as well as tensile tests conducted using specimens extracted from the extrusion stock material. A good correlation was observed between the results of the quasi-static crushing experimental results and the results of the finite element simulations. The experimental peak buckling loads of the structures were predicted to within 10% by the finite element simulations.

Formability Modeling with LS-DYNA

Torodd Berstad, Odd-Geir Lademo, Ketill O. Pedersen – SINTEF Materials and Chemistry, Odd S. Hopperstad – Norwegian University of Science and Technology

This paper presents how the process of loss of stability, as described by the classical theory of Marciniak and Kuczynski, can be represented in non-linear finite element analyses with LS-DYNA. As will be seen, this is strongly dependent upon proper constitutive equations and parameters for the sheet material at hand. Of this reason two user-defined sub-routines for weakly and strongly textured aluminum alloys, respectively, have been implemented. Further, a non-local instability criterion has been implemented in order to detect incipient plastic instability. Next, some inhomogeneity must be introduced in the finite element model. In further analogy to the work of Marciniak and Kuczynski the inhomogeneity can be introduced either to the material properties or to the thickness. In order to perform the calculations in an efficient way, an automated procedure – called an FLD-calculator – has been created. Finally, the FEM-based calculations are compared with analytical and experimental results.

Horizontal Tailplane Subjected to Impact Loading

M. Hörmann, U. Stelzmann – CAD-FEM GmbH, Germany, M.A. McCarthy – University of Limerick, Ireland, J.R. Xiaoc – University of Delaware, USA

The European Union Research Programme CRAHVI (CRashworthiness of Aircraft for High Velocity Impact) is concerned with the high velocity impact of aircraft due to flying objects, e.g. bird, hailstone, tyre and engine debris as well as concerned with survivable crash landings on different surfaces, e.g. rigid inclined surfaces (slopes) and water with different sea states. The simulation is naturaly a complex task due to the high number of variables involved. Such variables include material characteristics of the impacted media, impactors and surfaces at high strain rate, and the interaction between the aircraft structure and the impactors or surfaces. But with the increase of software and hardware computing power, it is now becoming more realistic to predict the behaviour of aircraft structures subjected to high velocity impact scenarios. Within the CRAHVI-Programme finite element models of a clamped horizontal tailplane (HTP) in an airliner are developed, which are subjected to impact loading with different impactor models. The HTP model composed of advanced composite material has been delivered by the University of Limerick [2],[3] whereas the HTP model representing metallic material was provided by the University of Patras [4]. Based on these models, the National Aerospace Laboratory NLR delivered an input file for the impact of a Lagrangian bird model on the HTP [8]. All files have been provided in form of PAM-CRASH input. It was the task of CAD-FEM to transfer those models into LS-DYNA input files, whereby special attention must be paid on a proper translation of the corresponding material models and the automatic generation of spotwelds. In case of the used composite bi-phase material the *MAT_LAMINATED_COMPOSITE_FABRIC model of LS-DYNA [11] is used. Based on those translated input files selective simulations for the composite and metallic structure are performed including bird strike on the leading edge (LE) of the HTP. For the bird strike simulation a Lagrangian as well as an ALE formulation is used. Additionally LS-OPT [10] was used in the Lagrangian bird strike simulation performing a thickness optimization of the LE. The optimization goal for bird strike is shortly speaking a non- rupture of the LE. The current contribution presents simulation results of rigid pole impact on composite HTP model, bird strike within Lagrangian formulation on metallic HTP model and bird strike within ALE formulation on metallic HTP model. Moreover the results are compared with other numerical results available within the CRAHVI-Programme. Additionally optimization results of the LE obtained from LS-OPT in combination with LS-DYNA are shown, which fulfill the desired optimization criterion of a non-ruptured leading edge.

IIHS Side Impact Analysis Using LS-DYNA/Madymo Coupling

Jiri Kral – TNO Madymo North America, Prabhu Setru, Swarna Rajeswaran – General Motors

The LS-DYNA/Madymo coupling has a growing popularity in the field of vehicle crash analysis as it allows the users to merge an existing occupant simulation subsystem model and a full car structural model into one system. The extended coupling feature introduced in late 2002 has significantly enhanced this model fusion capability. This paper demonstrates the application of such a coupling technique for the simulation of the IIHS (Insurance Institute for Highway Safety) side impact condition on one of General Motor’s vehicle development programs. However, when this analytical work was originated, the test configuration was new and still not completely defined. The baseline model consists of the vehicle structure and barrier model in LS-DYNA, and occupant and airbag models in Madymo. The baseline model was modified to demonstrate an enabler that helped improve side impact performance.

Immersive Visualization and Collaboration with LS-PrePost-VR and LS-PrePost-Remote

Todd J. Furlong – Inv3rsion, LLC

This paper describes two new branches of LS-PrePost that are designed to work together to extend LS-PrePost with immersive visualization and collaboration capabilities. LS-PrePost-VR supports immersive visualization on a wide range of immersive displays, including CAVE-like devices, large-screen displays, and head-mounted displays. The software can run on either a single computer, a visualization cluster, or an SMP machine. By itself, LS-PrePost-VR supports command-line reading of supported file types as well as playback of command files generated by desktop versions of LS-PrePost. A VR input device provides an intuitive interface that includes animation control, an interactive clipping plane, and selection capability. LS-PrePost-Remote is a client application that connects to the LS-PrePost-VR application and allows input to the application through the traditional LS-PrePost GUI. Multiple remote clients can connect to and synchronize with a VR session, allowing collaborative analysis on a corporate intranet. The paper discusses software design and implementation, as well as possible future directions for this software. LS- PrePost-VR and LS-PrePost-Remote are developed and supported by Inv3rsion, a software engineering firm located in Goffstown, New Hampshire.

Implementation of a Constitutive Model for Aluminum Foam Including Fracture and Statistical Variation of Density

A. Reyes, O. S. Hopperstad, T. Berstad, M. Langseth – Norwegian University of Science and Technology

An existing constitutive model applicable to aluminum foam was implemented in LS-DYNA. One main objective in the present project was to implement a model that could handle fracture in the foam. Therefore, two simple fracture criteria were also implemented in the model. Additionally, the possibility to include initial statistical variation of the foam density was incorporated in the model so that inhomogeneities in the foam properties could be represented. Foam subjected to both simple and more complex loading conditions where fracture was of varying importance have been analyzed, and some representative results and comparisons with experimental data are presented. The implemented model is efficient and robust, and gives good results. The model including one of the fracture criteria and without the possibility of statistical variation of density is at present available in version 970 of LS-DYNA.

Implementation of Modal Representation for Full Vehicle VPG Simulations

Xianggang Zhang – Engineering Technology Associates, Inc.

The modal representation method matured in LS-DYNA 970. It is a useful tool for full vehicle, long duration Virtual Proving Ground (VPG) analyses. The CPU time for VPG analysis could be dramatically reduced with such application. Modal representation method uses linear combination of the pre-calculated mode shapes to represent portion of the full vehicle model in transient dynamic analysis. The linear modal response of this portion of vehicle is superimposed to the full vehicle’s nonlinear explicit analysis. The explicit element processing is only applied to the rest of the model and thus reduces the total CPU time. A pickup vehicle was used in this study to demonstrate the application of this method to full vehicle VPG analysis. The mode shapes of the pickup box were calculated and superimposed to full vehicle VPG analysis. While the results were compatible to the results from a traditional explicit analysis, significant CPU time was also reduced by using this method.

Implicit and Explicit Finite Element Simulation of Soft-Pad Grinding of Silicon Wafers

A.H. Zhao , Z.J. Pei, X.J. Xin – Kansas State University

Silicon wafers are used to fabricate more than 90% of all integrated circuits. Surface grinding is the preferred technique used to flatten wire-sawn wafers. While conventional grinding is not effective in removing the waviness induced by wire-sawing process, experiments and finite element analysis indicated that soft-pad grinding is a promising method to remove waviness effectively. This paper presents the simulations of the process of the waviness removal of wire-sawn wafers by both implicit and explicit finite element methods using ANSYS and LS-DYNA respectively. Contact algorithms are important in the simulation of wafer grinding. Since the wafer thickness and pad thickness are in the range of millimeters which is thin in comparison with the wafer diameter (in the range of hundreds of millimeters), and the waviness height is usually in the range of tens of micrometers, selecting suitable penetration values in the contact algorithm is challenging. This paper is focused on the selection of contact model, element type, and other solution control parameters in both implicit and explicit methods. The study will be helpful for finding a generalized methodology in similar simulations of contact analysis.

Improved LS-DYNA Parallel Scaling From Fast Collective Communication Operations on High-Performance Compute Clusters

Lars Jonsson, Tim Prince – Intel Corporation

Fast collective communications are a key to maintaining high parallel efficiency as the number of nodes increases on a cluster of high-performance servers. Profiling of LS-DYNA message traffic demonstrates that good parallel scaling requires fast communications of short messages – up to a few kilobytes – and in particular of collective operations involving short messages. Fast collective operations require both an efficient implementation of the message-passing operations in terms of message primitives and a high-bandwidth, low-latency interconnect. This paper demonstrates both these aspects by presenting parallel-scaling measurements on Intel Architecture based compute clusters with MPICH2 implemented over fast interconnects. The analysis evaluates both the benefits, at application level, of the emerging MPICH2 work from Argonne National Laboratories relative to MPICH1, and the benefits from the single-digit microsecond latencies offered by todays fastest interconnects. The paper also outlines how next- generation interconnect technologies and new, efficient, and flexible MPI implementations can even further improve both application performance and adaptability.

Improved LS-DYNA Performance on Sun Servers

Youn-Seo Roh, Henry H. Fong – Sun Microsystems, Inc.

Current Sun platforms which are very competitive in price/performance include Linux servers using either the Intel Xeon or AMD Opteron processors. Benchmark results using the industry-standard Neon model are presented. Performance and scalability up to 32 CPU’s are discussed, as well as a comparison of use of gigabit Ethernet (GBE) interconnect versus Myrinet in a Linux Xeon cluster. Current status of Solaris x86 porting of LS- DYNA is also presented.

Improving Crash Analysis by Increasing Throughput of Large-Scale Simulations

Dale I. Dunlap, Shawn Freeman – Platform Computing

Numerical simulation is an important tool used by engineers to design and develop safe automobiles. As engineers study larger and more complex models, demand for computational throughput increases. Grids allow a company to utilize its existing hardware investment to build a cost-effective platform for simulating automotive crash testing. This paper will discuss how grid technology can substantially increase computational throughput of large-scale parallel simulations without having to upgrade the existing compute infrastructure. This leads to significant payback since customers can complete more work, while also deferring capital and operational costs.

Influence of Pre-Stressed Parts in Dummy Modeling – Simple Considerations

Ulrich Franz, Peter Schuster, Sebastian Stahlschmidt – DYNAmore GmbH

New regulations and consumer tests for passive safety in passenger cars have increased the de- mand on accurate models for occupant analysis. Thus, effects that have been neglected or mod- eled rather coarsely in recent occupant models might necessitate a more detailed modeling in order to capture the dummy behavior sufficiently accurate. This paper contributes to the discussion of the importance and the modeling techniques of pre- stressed parts in dummy models for occupant analysis. The authors present solutions provided by LS-DYNA to handle the pre-stressed parts like mapping, pre-simulation, or implicit time-step- ping for positioning. Finally, the paper discusses sources of pre-stress in different parts of side impact dummies (SID), Hybrid III adult and child dummies. With simple examples the influence of the pre-stress is estimated.

Investigation of dsDNA Stretching Meso-Mechanics Using LS-DYNA

C. A. Yuan, K. N. Chiang – National Tsing Hua University,

This paper proposes a novel mathematical model for studying the entropic elasticity and cooperative extensibility of double strand DNA (dsDNA) using LS-DYNA and equivalent theory. Through the proposed model, the dynamic structural transitions of the dsDNA under external force/torque can be accurately simulated within an affordable CPU time. Moreover, the proposed dsDNA model comprises the meso-mechanics equivalent theory of single molecule dsDNA, including the base-stacking interaction between DNA adjacent base pairs, the Hydrogen bond of complementary base-pairs and electrostatic interactions along double-helix sugar-phosphate backbones. Good agreement is achieved between the numerical simulation and the single molecular manipulation experimental result, and the mechanical behavior of stretching nicked dsDNA could be revealed.

Investigation of the Arbitrary Lagrangian Eulerian Formulation to Simulate Shock Tube Problems

C.P. Salisbury, D.S. Cronin, F.S. Lien – University of Waterloo

A critical step in modeling complex problems using numerical simulations is validating the numerical approach using simplified problems. The current study investigates application of the Arbitrary Lagrangian Eulerian (ALE) formulation, as implemented in LS-DYNA, to simulate a pseudo 1-D shock tube problem. The shock tube problem was selected since analytical results can be directly determined from the initial conditions. A shock tube is modeled as two regions of fluid at two different pressures separated by a thin membrane. The two regions are usually, but not necessarily, comprised of the same fluid. One region, know as the driver, is at a higher pressure than the other. Ideally, the thin membrane is completely destroyed to initiate flow, allowing the high pressure region to interact with the low pressure region. If the difference in pressures between the two regions is sufficient, a shock wave will propagate into the low pressure region and an expansion wave will propagate into the high pressure region. The current study is conducted to test the ability of the ALE formulation in LS-DYNA to correctly predict the shock and expansion wave propagation seen in a shock tube test. The results of this study are dependent on a number of factors such as the size and orientation of the mesh. A convergence study to determine the minimum mesh density to correctly simulate the shock phenomena was also conducted. This is of special importance when the ALE formulation is used in real world problems where the required mesh size can become quite large, and therefore computationally prohibitive.

Learning Module for using Dynaform® to Study the Effects of Die-Entry and Punch-Nose Radii on Drawing Cups

W.K. Waldron, R. Echempati, C.J. Hoff, P. Zang – Kettering University

The new model for an entry-level engineer in the United States automotive industry is that of a design engineer, one who is capable of part design and analysis using advanced CAE tools such as solid-modeling, mechanical systems dynamics (MSD), finite element analysis (FEA), and computational fluid dynamics (CFD). Since this will require a major change and enhancement of the current undergraduate engineering curriculum, the Mechanical Engineering Department at Kettering University (formerly GMI) is developing a comprehensive set of Learning Modules that can be woven into all Mechanical Engineering courses so that students use the tools often and in various contexts to solidify their knowledge of the computational tools and meet the learning objectives of the courses. The modules will be self-paced and self-explanatory, can be used by students and faculty outside of the classroom, and include meaningful examples that use CAE and existing laboratories to study real-life problems. This paper describes one of the first prototype modules for Manufacturing and Mechanical Engineering students in a senior-level course in sheet metal forming. The students investigated the effects of changes in the die-entry radius and punch-nose radius versus depth of draw for cylindrical cups using various ring dies and flat bottom punches. The experimental data consistently showed that the die-entry radius has a very marked effect on depth while the punch-nose radius has very little effect. For a change in die-entry radius, once a minimum value has been exceeded, the material flows smoothly over the radius to generate a full depth cup. Simulation results using Dynaform® are presented that show that the experimental observations can be modeled by assigning appropriate values for the process parameters (die entry radius, clearance, friction, and binder). The Design of Experiments (DOE) method is used to develop guidelines for the selection of the process parameters for drawing cylindrical cups based on Forming Limit Diagrams from the simulations data.

LS-DYNA Communication Performance Studies

Ananthanarayanan Sugavanam, Guangye Li – IBM

In recent years, MPP-DYNA, the message passing parallel version of LS-DYNA, has become more and more popular in car crash and metal stamping simulations due to its good scalability which may reduce the turn-around time significantly when more processors are used. However, so far, most users only use 16 or less processors for LS-DYNA simulation because of the limitation of the scalability on a larger number of processors. This paper analyzes the communication patterns, message sizes and costs of simulation of two models. It is concluded that the unbalanced work load among processes is the bottleneck for scalability. Our study shows that some special decomposition techniques including sliding interface decomposition and scaling on certain directions may produce more balanced work load and, therefore, improve scalability. It is our hope that this study provides some insight for the algorithm improvement which may lead to better MPP-DYNA scalability on a larger number of processors.

LS-DYNA Implicit for Dent Performance Evaluation

Gagan Tandon, Venugopal Bachu – Altair Engineering Inc.

Present day engineering design involves complex CAE analyses using both linear and non-linear methods. Mos companies use multiple software tools for different types of analyses. Several reasons, including cost are driving companies to investigate lesser number of FEA tools so that they can use a single solver for most of their structural analyses. LS-DYNA has been traditionally used for explicit analysis like crash and metal forming. Recent enhancements in the versions of LS-DYNA enable us to evaluate it for implicit analysis. The success of an automotive design is determined by its ability to meet the expectations of the customer with respect to cost, performance and styling. Dent performance is an important factor in designing automotive outer panels due to increased customer sensitivity to surface finish and durability. Dent performance is defined as the deflection under certain external loads at the panel outer surface. The external loads can be from many sources like shopping carts or from an adjacent vehicle door in a parking lot. Dent performance prediction assumes a quasi-static equilibrium solution eliminating the effects of inertia, thereby making it an implicit analysis. Dent prediction analyses are traditionally performed using specialized implicit solvers. In this study, LS-DYNA implicit was used to predict dent performance on several outer panels (doors & hoods). The results were then compared to the corresponding experimental results and to the results from a competing solver. This paper also describes the setup using Altair HyperMesh, various analysis parameters and element formulations used for dent analysis.

LS-OPT Capabilities for Robust Design

Nielen Stander, Willem Roux – Livermore Software Technology Corporation

This paper presents a number of new features available in LS-OPT Version 2.2. As a step toward robust design, the code has been extended to enable reliability assessment and the identification of sources of unpredictability in the FE model. In the latter feature, deterministic and stochastic effects can be separated.

Material Modeling of Space Shuttle Leading Edge and External Tank Materials For Use in the Columbia Accident Investigation

Kelly Carney, Matthew Melis – NASA Glenn Research Center, Edwin L. Fasanella – US Army Research Laboratory/VTD, Karen H. Lyle – NASA Langley Research Center, Jonathan Gabrys – Boeing

Upon the commencement of the analytical effort to characterize the impact dynamics and damage of the Space Shuttle Columbia leading edge due to External Tank insulating foam, the necessity of creating analytical descriptions of these materials became evident. To that end, material models were developed of the leading edge thermal protection system, Reinforced Carbon Carbon (RCC), and a low density polyurethane foam, BX-250. Challenges in modeling the RCC include its extreme brittleness, the differing behavior in compression and tension, and the anisotropic fabric layup. These effects were successfully included in LS-DYNA Material Model 58, *MAT_LAMINATED_ COMPOSITE_ FABRIC. The differing compression and tension behavior was modeled using the available damage parameters. Each fabric layer was given an integration point in the shell element, and was allowed to fail independently. Comparisons were made to static test data and coupon ballistic impact tests before being utilized in the full scale analysis. The foam’s properties were typical of elastic automotive foams; and LS-DYNA Material Model 83, *MAT_FU_CHANG_FOAM, was successfully used to model its behavior. Material parameters defined included strain rate dependent stress-strain curves for both loading and un-loading, and for both compression and tension. This model was formulated with static test data and strain rate dependent test data, and was compared to ballistic impact tests on load-cell instrumented aluminum plates. These models were subsequently utilized in analysis of the Shuttle leading edge full scale ballistic impact tests, and are currently being used in the Return to Flight Space Shuttle re-certification effort.

Modeling Crushable Foam for the SAFER Racetrack Barrier

Robert W. Bielenberg and John D. Reid – University of Nebraska-Lincoln

One of the key components in the new SAFER barrier being installed at many IRL and NASCAR racetracks is the foam blocks placed between an outer steel tube structure and the existing concrete wall. Simple polystyrene insulation foams were proven to have good energy absorbing capabilities and were used as a primary means of energy absorption in the barrier. This foam is very low cost and easy to obtain. Foam research began with obtaining several samples of cubic foam blocks and then performing static and dynamic testing on them. Simulation of the dynamic test with LS-DYNA concentrated on the use of the *MAT_CRUSHABLE_FOAM material model. After successfully modeling of the bogie tests, the component model of the foam was placed in the full-scale model of the SAFER barrier. Later in the research program, the cubic shape foam blocks were replaced with a trapezoidal shape. These trapezoidal shapes were also tested and then, successfully simulated.

Modeling of Fuel Sloshing Phenomena Considering Solid-Fluid Interaction

Jean Ma, Mohammad Usman – Plastics Products and Processing CAE Visteon Corporation

The sloshing phenomenon in partially filled fuel tanks is more pronounced when vehicles experience a sudden start or stop. Sloshing is un-desired because it produces noise, high impact force on the tank walls and the challenge of low fuel handling. Today, the solution for containing sloshing is to incorporate baffles inside the tank. The presence of baffle dissipates the energy that is induced by the fuel motions. Design of baffles is a necessary step during the design of a fuel tank to meet required performance specification in service. A methodology to simulate sloshing phenomenon that incorporates solid-fluid interaction is presented in this paper. The methodology makes use of both Eulerian and Lagrangian formulation. Eulerian domain includes both air and fuel inside the tank, and the space around the tank. Lagrangian domain includes the tank shell and baffle structure. A concept of coupling surfaces is introduced in Eulerian domain to build the boundary of the inner and the outer of tank structure. The coupling surfaces also act as interactive surfaces between both Eulerian and Lagrangian domains to prevent penetration. A computational method is employed to simulate the sloshing phenomenon in tank when the vehicle is in motion. The simulation results are compared with the sloshing test results.

Modeling of Welded Structures Residual Strains

Sergey Medvedev, Maria Petrushina, Oleg Tchij – National Academy of Sciences of Belarus

This paper explores simulation techniques for prognosis residual strains of welded structures, which consist of common steel parts joined together by means of arc welding. The approach is based on longitudinal and transversal shrinkage forces, applied to the 3d-model of plastic weld zones. The calculations were made on ANSYS – LS-DYNA 970 MPP version on supercomputer SKIF-family located in United Institute of Informatics Problems of National Academy of Sciences of Belarus. The obtained results find good agreement with literature and practice data. Residual welding strains techniques approved for welding tubes, beams and some machine building constructions.

Modeling the Nonlinear, Strain Rate Dependent Deformation of Shuttle Leading Edge Materials with Hydrostatic Stress Effects Included

Robert K. Goldberg, Kelly S. Carney – NASA Glenn Research Center

An analysis method based on a deformation (as opposed to damage) approach has been developed to model the strain rate dependent, nonlinear deformation of woven ceramic matrix composites, such as the Reinforced Carbon Carbon (RCC) material used on the leading edges of the Space Shuttle. In the developed model, the differences in the tension and compression deformation behaviors have also been accounted for. State variable viscoplastic equations originally developed for metals have been modified to analyze the ceramic matrix composites. To account for the tension/compression asymmetry in the material, the effective stress and effective inelastic strain definitions have been modified. The equations have also been modified to account for the fact that in an orthotropic composite the in-plane shear response is independent of the stiffness in the normal directions. The developed equations have been implemented into LS-DYNA through the use of user defined subroutines (UMATs). Several sample qualitative calculations have been conducted, which demonstrate the ability of the model to qualitatively capture the features of the deformation response present in woven ceramic matrix composites.

Moving Beyond the Finite Elements, a Comparison Between the Finite Element Methods and Meshless Methods for a Ballistic Impact Simulation

Murat Buyuk, Cing-Dao Steve Kan, Nabih E. Bedewi – The George Washington University, Ali Durmus, Sedat Ulku – Uludag University

For the past several decades, finite element techniques have been used extensively for the analysis of computational solid mechanics problems. However, when the distortions become very severe, especially Lagrangian finite element algorithms are not always adequate. More recently meshless methods (or particle methods) have been developed and applied to solid mechanics problems since they can efficiently be used to represent severe distortions and are more robust for dynamics problems such as high energy impacts and penetrations that involve large deformations and even erosions. Impacts at higher speeds are also challenging because of the high strain rate behavior of the materials and the significant importance of the stress wave propagation through the material. In this paper, the deformation pattern and characteristics of a thin (50 μm) foil is investigated both numerically and experimentally under impact loading of a 9 mm standard NATO bullet, at several speeds by using a 3D non-linear explicit numerical code, LS-DYNA. Different element and particle algorithms are used to obtain the best numerical representation of the problem. The differences between Lagrangian, Eulerian, ALE (Arbitrary Lagrangian- Eulerian) and SPH (Smoothed Particle Hydrodynamics) formulations are briefly compared and discussed under ballistic impact conditions. The results obtained from these different numerical models are also validated with a series of tests and are in good agreement with the experimentally measured values.

Nonlinear Finite Element Analysis of Airport Approach Lighting Structures under Impact Loading

M. Nejad Ensan, D.G. Zimcik – National Research Council Canada, S.T. Jenq, F.B. Hsiao – National Cheng Kung University, Taiwan

This paper describes computer simulation of the impact of airport approach lighting structures using the LS-DYNA nonlinear finite element analysis (FEA) software. Two tower designs were investigated in this simulation. First, a finite element model (FEM) was developed to simulate the impact of a representative tower typical of those used at Canadian airports. This was 6.6 m tall tower with a triangular cross section made of aluminum. The analysis simulated an aircraft wing striking the tower triangular cross section 1 m from the top in two different orientations of the tower, at the apex and on the side. Top mass of 2.72 kg or 5.44 kg, representative of lights and/or light fixtures was included in the model which was impacted at three different impact velocities: 50, 80 and 140 km/h. Further simulation was carried out on a second model of an approach light masts with different geometry and made of a different material typical of those used at some European airports. These were 6 m tall masts, and contained a dummy top mass of 15 kg, simulating the effect of a cross-bar with three approach lights. The masts were configured as a composite lattice structure with a square cross section made of glass/epoxy. The impact of the mast at a height of 4.1 m above the ground due to an impact of the moving aircraft wing at velocity of 140 km/h was simulated. The duration of the simulation in both cases was 100 milliseconds to captured the phase in which most of the damage to the tower took place. Simulation results were used to predict the deformation mode and magnitude, location and timing of failure, impact force and energy absorption curves as a function of time during the impact. These results were compared to experimental data from full-scale tests to validate the accuracy of the models. These data were necessary for the development of simplified requirements and test methods for the design of frangible structures that minimize the impact hazard to aircraft.

Numerical Modeling of Ballistic Penetration of Long Rods into Ceramic/Metal Armors

Khodadad Vahedi, Najmeh Khazraiyan – Louisiana Tech University

Penetration into ceramic/armor targets are of prime importance in research as well as industry and military applications. The recent advances in this field shows considerable improvements in the design of armor and civilian technology. Due to complexity of the problem and interdisciplinary of the subject, most of the works in this respect are experimental in nature. The cost of experimentation is high and the results obtained cannot be extrapolated to a large number of cases. However due to the advances of computer simulation, the field of numerical analysis is becoming highly attractive for application and research. Numerical modeling of ballistic impact of long rod penetrators into ceramic armor with semi-infinite backing targets is considered in this paper. An explicit, three-dimensional finite element code LS-DYNA is used in the analysis of the problem. The behavior of ceramic and backing materials are modeled as Elastic-Plastic Hydrodynamic with pressure cutoff and failure strain. The projectile is modeled as Johnson-Cook. Mie-Gruneisen and linear polynomial equation of state are used for materials. The impact velocity range is from 750 to 1350 m/s. The results of investigation are in a very good agreement with experimental data. Keywords: Ballistic impact; Ceramic armor; Finite element model; Long rod; Penetration depth

Numerical Modeling of Woven Carbon Composite Failure

Paul F. Deslauriers, Duane S. Cronin – University of Waterloo, Alex Duquette – Multimatic Technical Centre

This paper presents application of a MLT-based (Matzenmiller, Lubliner, Taylor) approach to model damage in woven carbon composite materials. The MLT formulation has been adapted to shell elements to model individual composite plies. The implementation of the model is discussed along with simple test cases to demonstrate the material response and limitations within the original MLT model. One of these limitations has been addressed through implementation of different damage parameters for tensile and compressive loading. In addition, this damage-based approach has been modified by the use of a non-local damage treatment to distribute accumulated damage across element boundaries. Application of this model to simple test cases indicates that the model demonstrates expected behaviour.

Numerical Simulation of Aluminum Alloy Forming Using Underwater Shock Wave

Hirofumi Iyama – Yatsushiro National College of Technology, Kousei Takahashi – Kumamoto Industrial Research Institute, Takeshi Hinata, Shigeru Itoh – Kumamoto University

In recent years, on automobile industry, the car has body using aluminum alloy. As for this material, #5000’s, 6000’s and 7000’s aluminum alloy is used well. However, the sheet metal forming of these materials by the static method, such as the hydro bulge forming and general punching, is very difficult, because these are little elongation compared with major steel. We considered application of the explosive forming. Therefore, we have tried free forming of aluminum alloy as the basic study. We compared the elongation of aluminum alloy by the explosive forming with punching. Consequently, it was larger for the amount of deformation of aluminum alloy by the explosive forming. In addition, we have done a theoretical elucidation. It is important the investigation of deformation process of aluminum plate by the explosive forming. Therefore, we solve using the numerical simulation by LS-DYNA. In this simulation, it carried out detonation process of the explosive, propagation process and deformation process of aluminum alloy.

Prediction of Seat Deformation in Rear Crash Using LS-DYNA

Biswanath Nandi, Dinesh Jain – Lear Corporation, USA

It has always been a challenging task to simulate occupied rear crash for seating system. To design an ideal seat for resisting the load during rear impact is also a difficult task for the seat suppliers. Seat Suppliers are in continuous search of newer methods and techniques to reduce number of prototypes and testing cost. Analytical methods of predicting structural behavior using computer aided engineering (CAE) has been in place for quite sometime. A CAE method using LS-DYNA has been developed at Lear Corporation to simulate the rear impact and to predict the seat deformation. Rear Crash simulation has been performed on a six-way power driver seats using this procedure and back frame deformation predicted by the simulation has been validated to the physical test and a good correlation has been achieved. This paper discussed the methodology adopted and the correlation achieved.

Predictive Numerical Modeling of Foreign Object Damage

Pierangelo Duó, David Nowell – University of Oxford

During service aircraft engines may suffer foreign object damage (FOD) from ingestion of small hard particles and then are subjected to a range of HCF-LCF cycles. Manufacturers are seeking to improve the FOD tolerance of engines at the design stage and thereby reduce the costs of ownership. A design methodology is therefore required with which to assess the loss of fatigue strength resulting from FOD on blades or vanes. This work describes progress in the prediction of the residual stresses left from the impact in a specimen which resembles a compressor blade. The FE package LS-DYNA has been used to analyse the problem. Initially different material models were considered, each including a strain rate dependence, and a calibration based on a tensile test was performed. The Bamman Damage (Mat 52) was then chosen and used in the numerical model of impact on an aerofoil leading edge. The model has proved capable of recreating the damage geometry and gives a valuable insight into the likely residual stress distribution around the notch. A subsequent fatigue analysis of the impacted blade has been run using the same material model. A methodology based on a posteriori analysis and comparison with post-impact fatigue experiments has been used to confirm the results obtained.

Preliminary Assessment of Non-Lagrangian Methods for Penetration Simulation

Leonard E. Schwer – Schwer Engineering and Consulting Services

Lagrangian, Eulerian, and Smooth Particle Hydrodynamics formulations are applied to the simulation of a rigid fragment impacting a concrete panel. An effort is made to keep much of the computational model constant across the simulations. All three methods are shown to be appropriate for this class of ballistic impact simulation. The results and conclusions are preliminary, but the paper serves as an introduction to these alternative forms of penetration analysis.

Rapid Development of Multiple Fold Patterns for Airbag Simulation in LS-DYNA Using Oasys Primer

Miles Thornton, Richard Sturt, Anastasia Kalabina – Arup

The creation of folded meshes for airbag deployment simulations is a time consuming task. The fold pattern has a significant effect on the speed and shape of deployment of the airbag, and therefore should be modelled when prediction of deployment timing is required, as is the case with out of position analysis for FMVSS 208. To investigate changes in fold patterns or airbag shape involves repeating the entire airbag mesh process for each modification. This paper describes a new mesh-independent folding tool in Oasys Primer that can speed up the modelling process. The time required for each operation is quantified for a variety of fold patterns on a thorax bag. Finally, a driver airbag is inflated using LS-DYNA’s ALE gas flow capability, and the deployment timing compared between mechanical and traditional zig-zag fold patterns.

Review of Sheet Metal Forming Simulation Progress to Date, Future Developments

Trevor Dutton – Dutton Simulation Ltd

Sheet metal forming simulation is a well established application of LS-DYNA. Originally used for trouble shooting, it is now increasingly accepted as a method for testing tooling design prior to manufacture; however, there are further opportunities to apply such methods as early as possible, even in the product design stage. This paper reviews the advances of recent years and presents an example of typical current applications; the tools now offered for die face creation are then discussed. The paper also looks ahead to see how application of these methods might develop and indicates areas for research, in order to achieve the maximum benefit from simulation.

Robustness Study of an LS-DYNA Occupant Simulation Model at DaimlerChrysler Commercial Vehicles Using LS-OPT

Dr. Frank C. Günther – DaimlerChrysler, Dr. Heiner Müllerschön, – DYNAmore GmbH, Dr. Willem Roux – Livermore Software Technology Corporation

The robustness properties of crash simulation models are emerging as an important criterion in today’s simulation driven vehicle development process. We consider it relevant to any study of highly non-linear crash problems to obtain measures for the repeatability and reliability of both experimental and numerical tests. In 2003, we conducted a robustness study of a structural front impact model (JAPAN LS-DYNA Users Conference 2003) using the Meta-Model concept of LS- OPT. This study seemed to indicate that there is an inherent, residual randomness in crash problems. In the present paper, we present a new robustness study of a frontal sled test occupant model with a 50th percentile FTSS dummy. Our goals were: • Determine variations of typical occupant safety responses such as HIC, chest intrusion, and others due to uncertainties in the experimental setup, including dummy position, airbag mass flow, and acceleration. • Separate deterministic and residual, random variations of responses using the Meta-Model technique. • Get a feeling for random variations inherent in occupant studies. • Evaluate the generality of these robustness results through a convergence study varying the number of simulation experiments and variables for the Meta-Model.

Simulation and Analysis of the Beverage Can Necking Process Using LS-DYNA

A. Jordan-Cordera, J.C. Miranda-Valenzuela – ITESM Campus Toluca

Due to their large production quantities, beverage cans have been the subject of many studies. Such studies have as objectives to increase the level of understanding of the structural behavior of the can as well as its manufacturing process. In this work, the necking process is studied by means of a parameter response study carried out with the help of LS-DYNA. Even when the necking process is affected by many factors including can geometry, material properties, tool geometry, friction coefficient between the tools and the can, punch speed, etc., in this study only four variables are taken into account: friction coefficient, punch speed, can thickness and can radius.

Simulation and Verification of the Drop Test of 3C Products

Hsing-Ling Wang – Chinese Air Force Academy, Shia-Chung Chen, Lei-Ti Huang, Ying Chieh Wang – Chung-Yuan Christian University

Drop test performance has become one of the most crucial evaluations for Computer, Communication, and Consumer (3C) products. Both simulation tool and practical platform for drop test must be established for detailed study. A patented drop test platform is designed for the purpose of impact angle repeatability and instantaneous drop image capture at impact instance. These parameters are two crucial computer-aid-engineering (CAE) inputs used for drop impact simulations. Post data processing procedures such as sampling rate, and signal filtering specifications was also studied and found to be important for the accurate interpretation of drop simulations as well. It was found from simulations that a small angle variation ( 5°) may result in up to 36% difference in predicted ± internal stress. Accurate identification on the impact angle, therefore, is recommended as an important parameter on internal component stress calculation. Good consistency between measured acceleration data and simulated results verifies the practicality of the developed data processing procedure and numerical methodology.

Simulation of Cure Volume Shrinkage Stresses on Carbon/Vinyl Ester Composites in Microindentation Testing

Tom Mase, Lanhong Xu, Lawrence T. Drzal – Michigan State University

Composites made with carbon fibers and vinyl ester have significant higher processing volume shrinkage compared to composites made with epoxies. During the curing, vinyl esters experience as much as three times the volume shrinkage as compared to epoxies (10 %Vol versus 3-4 %Vol). This difference in cure volume shrinkage may be the reason that the mechanical properties of carbon/vinyl esters are low compared to that of carbon/epoxy. Cure volume shrinkage of neat resins have been measured using a dilatometer. Interfacial shear strength (IFSS) measurements for different cure volume shrinkage were completed showing a reduction in strength as the cure volume shrinkage increased. LS-DYNA was used to model the volume cure shrinkage and resulting interface/interphase properties. Modeling results are dependent on the specific representative volume element (RVE) and boundary conditions used in the simulation. Cure volume shrinkage was modeled using a temperature drop on thermoelastic material (*MAT_ORTHOTROPIC_THERMAL). Following the temperature drop, the fiber was loaded with a rigid, spherical indenter to simulate the IFSS test (at constant temperature). Simulated resultant fiber-interphase, interphase-matrix, and fiber-matrix (in the case of no sizing) are reported as a function of cure volume shrinkage. Shearing stress distributions at the fiber-interphase and interphase-matrix are also presented.

Simulation of Energy Absorbing Materials in Blast Loaded Structures

Michael J. Mullin, Brendan J. O’Toole – University Nevada Las Vegas

Energy absorbing materials such as foam or honeycomb are of interest in blast protection because of their ability to absorb energy through plastic deformation. After reaching their yield stress, these materials exhibit a region of constant stress for increasing strain until the material is completely compacted. The energy needed to crush the material is proportional to the area under the stress-strain curve. Because foams and honeycombs have this “plateau” region, they absorb a considerable amount of energy relative to their low density. These materials are investigated to determine if their energy absorbing abilities can be used to mitigate the load and shock transferred to a vehicle structure subject to blast loading. Ballistic pendulum experiments show that energy absorbing materials increase the imparted impulse from a blast. This behavior was contrary to expected results so computational models were created in LS-DYNA to understand the phenomenon that causes an increase in imparted impulse. ConWep and Arbitrary-Lagrangian- Eulerian (ALE) techniques were used in simulations to demonstrate their efficiency and accuracy. An additional ConWep aluminum foam model was created to directly compare simulations against ballistic pendulum experiments found in the literature.

SPH Performance Enhancement in LS-DYNA

Gregg Skinner, Dennis Lam – Advanced Technical Computing Center, Masataka Koishi – Yokohama Rubber Corporation, Hiroki Shimamoto – NEC Corporation

The Smoothed Particle Hydrodynamic (SPH) method had been implemented in LS-DYNA for some time. However, SPH had not been used extensively; therefore, performance issues were never highlighted and never addressed. Recent efforts to run SPH on NEC SX systems revealed substantial performance problems. NEC, Yokohama Rubber Corporation and LSTC collaborated to enhance the performance of SPH. As a result, the performance of SPH function in LS-DYNA has been improved on NEC SX-6 vector-parallel supercomputer by a factor of four. This article provides some background information about the code tuning effort, the SX series vector-parallel supercomputers, and the performance improvement achieved

Strain Rates in Crashworthiness

Moisey B. Shkolnikov

Strain rates related tests, strain rates measurements, strain rates states during vehicle collisions, crashworthiness tests and simulations are discussed in the paper. Several papers (on which some of LS-DYNA strain rates options in constitutive models for metals are based) are considered in this paper from an automotive vehicle crashworthiness point of view. Strain rates effect on structure’s metals during explosions are mathematically described in the papers. The objective of crashworthiness is not (like under explosion) to save a structure, but to sacrifice (making failing in a control manner) the structure to save its occupants during vehicle collisions. Sufficiently taking (during crashworthiness design) into account strain rates in vehicle structures during collisions will increase the structures energy absorption capability and increase their occupants’ survival probability.

Study of a Driver Airbag Out-Of-Position Using ALE Coupling

Wenyu Lian – General Motors, Dilip Bhalsod – Livermore Software Technology Corporation

The new FMVSS 208 regulation specifies the airbag performances under Out-of-Position conditions. During the past 10 years, the thermodynamic-based airbag models have been successfully used in analyzing the occupant interaction with the airbag under regular crash conditions (in-position). However, these models are not suitable for the airbag OOP applications since they can not accurately predict the flow forces that dominate the occupant-airbag interactions under these conditions. Recently, new computational fluid dynamic features were developed, validated and implemented into the current version (v970) of LS-DYNA [1,2,3]. These features, such as the MAT_GAS_MIXTURE gas model, and the POINT_SOURCE inlet flow model, enable users to simulate airbag OOP applications using the ALE coupling techniques. Thus, the influence of design changes, such as the inflator orifice direction, vent locations, and the flow diverse straps in the bag can be investigated. The study of a driver airbag with a 5th%ile dummy under the ISO P2 OOP condition using the ALE coupling techniques is presented here. In this study, the modeling methods for the inflator gas jets, vents, and bag folds are discussed. The results of ALE model are compared with the AIRBAG_HYBRID model and the test data. The ALE simulations show a significant improvement over the HYBRID model. The technical issues associated with OOP simulations, merit & limitations of the current ALE model, and future works are also discussed.

Test and Analysis Correlation of Foam Impact onto Space Shuttle Wing Leading Edge RCC Panel 8

Edwin L. Fasanella – US Army Research Laboratory, Vehicle Technology Directorate, Hampton, VA, Karen H. Lyle – NASA Langley Research Center. Hampton, VA, Jonathan Gabrys – The Boeing Company, Philadelphia, PA, Matthew Melis and Kelly Carney – NASA Glenn Research Center, Cleveland, OH

Soon after the Columbia Accident Investigation Board (CAIB) began their study of the space shuttle Columbia accident, “physics-based” analyses using LS-DYNA were applied to characterize the expected damage to the Reinforced Carbon-Carbon (RCC) leading edge from high-speed foam impacts. Forensic evidence quickly led CAIB investigators to concentrate on the left wing leading edge RCC panels. This paper will concentrate on the test of the left-wing RCC panel 8 conducted at Southwest Research Institute (SwRI) and the correlation with an LS- DYNA analysis. The successful correlation of the LS-DYNA model has resulted in the use of LS-DYNA as a predictive tool for characterizing the threshold of damage for impacts of various debris such as foam, ice, and ablators onto the RCC leading edge for shuttle return-to-flight.

The Dynamic Problems in High Speed Transfer Stamping System

Ming-Chang Yang, Hsing-Chih Tsai and Tien-Chi Tsai – Metal Industries Research and Development Centre

In this paper the authors would like to disclose the application of LS-DYNA, the dynamic explicit finite element method, in high speed transfer stamping system development. Transfer stamping process has the advantages of material saving and automation especially for stamping parts with complicated geometry. The dynamic effects will be induced as the stamping speed up to 200 SPM i.e. the contact dynamics of barrel cam and followers, transient dynamic effect as grippers contact with blanks and the die swell caused dimension inaccuracy problems, etc. According to the numerical results, we have modified the original design for barrel cam structure and dimension, roller size and transfer bar diameter to enhance the component endurance life. We used the NURBS curves in the cam curves design, which reduced the impact force as the rollers crossed over the contact sides at each groove and traveled smoothly. The gripper designer referred the simulation results to avoid the parts tilting after the grippers closed. All the dynamic problems of transfer system were under controlled via the computer simulation and we have designed our system stamping speed up to 250 SPM successfully.

The Effects of Numerical Result and Computing Time Due to Mass Scaling in Rolling Analysis

J.Y. Chin, S.W. Lee, S.H. Paik, W.S. Chung – Theme Engineering Inc.

To enhance the structural performance for vehicle, a patch is attached. For various section shapes, each patch has different performance in energy absorption. In despite of efficient patch, formability may be a problem. Because the depth of groove is about 0.2mm, it needs a large FEM model for rolling analysis and has very small time step. We have to choose a method to reduce analysis time. This paper presents the effects of mass scaling in rolling analysis of a reinforcement patch for vehicle. We examined applicable mass or velocity scaling range. Besides to resolve severe mesh distortion in the sharp pattern forming, we apply efg formulation that is a new function in LS-DYNA version 970 and compare it with standard method.

The Use of LS-DYNA in the Columbia Accident Investigation and Return to Flight Activities

Jonathan Gabrys, Josh Schatz – The Boeing Company, Kelly Carney, Matthew Melis – NASA Glenn Research Center, Edwin L. Fasanella – US Army Research Laboratory/VTD, Karen H. Lyle – NASA Langley Research Center

During the launch of the Space Shuttle Columbia on January 16, 2003, foam originating from the external tank impacted the shuttle’s left wing 81 seconds after lift-off. Then on February 1st, Space Shuttle Columbia broke- up during re-entry. In the weeks that followed, the Columbia Accident Investigation Board had formed various teams to investigate every aspect of the tragedy. One of these teams was the Impact Analysis Team, which was asked to investigate the foam impact on the wing leading edge. This paper will describe the approach and methodology used by the team to support the accident investigation, and more specifically the use of LS-DYNA for analyzing the foam impact event. Due to the success of the analytical predictions, the impact analysis team has also been asked to support Return to Flight activities. These activities will analyze a far broader range of impact events, but not with just foam and not only on the wing leading edge. The debris list has expanded and so have the possible impact locations. This paper will discuss the Return to Flight activities and the use of LS-DYNA to support them.

The Use of LS-DYNA to Simulate the Water Landing Characteristics of Space Vehicles

Benjamin A. Tutt, Anthony P. Taylor – Irvin Aerospace Inc

Irvin Aerospace, Inc. has been involved with the recovery/landing systems of re-entry and interplanetary space vehicles spanning a number of years. A significant aspect in the assessment of recovery and escape systems is the performance of such vehicles in the event of a water landing. One method used to reduce the loads imparted to the crew as the vehicle enters the water is to increase the drag area of the falling body. Increasing the drag area of the recovery system is a simple resolution, however, integration leads to an unfavorable increase in the total system mass and volume requirements. An alternative solution, utilized by the Apollo Earth Landing System, is to dictate the orientation of the vehicle prior to water impact. The results of an exhaustive test program showed that the accelerations experienced by the crew could be reduced by a factor of five simply by changing the vehicle water entry angle. This paper presents an application of the Eulerian-Lagrangian penalty coupling algorithm and multi- material ALE capabilities within LS-DYNA. Documented in the report are the results of a series of validation simulations undertaken by Irvin in an IRAD program to ascertain the capacity of LS-DYNA to replicate the water- landing characteristics of an Apollo Command Module and predict the performance of future landing systems

Theory and Evaluation of Concrete Material Model 159

Yvonne D. Murray – APTEK, Inc.

The roadside safety community supplements real world crash test data with LS-DYNA simulations performed on the computer. The accuracy of the simulations depends, in part, upon the material models that are formulated to simulate the behavior of the roadside structures and vehicle materials. One important roadside structural material is concrete. A comprehensive concrete material model was developed, implemented in the LS-DYNA finite element code, and evaluated for simulating the deformation and damage to reinforced concrete beams from dynamic impact. For ease of use, default material properties for concrete are incorporated into the model as a function of concrete compressive strength. Correlations with drop tower and bogie vehicle impact tests are used to evaluate the model and finalize the default material properties.

Through Process Modelling of Self-Piercing Riveting

R. Porcaro, A.G. Hanssen, M. Langseth, A. Aalberg – Norwegian University of Science and Technology

Self-piercing riveting is a relatively new process for joining sheet metals in automotive structures. Information obtained from the riveting process simulation can lead to an improvement in the process design achieving reduction in cost and improvement in the quality of the joint. The process data can also be used to set initial parameters for a 3D simulation of the self-piercing rivet connection under combined tensile and shear loading conditions. Comparison of the results from the 3D simulation with experimental data will give a further proof of the quality of the self-piercing riveting process simulation and a better understanding of the behaviour of the connector. Such information can then lead to an improvement of a numerical model of self-piercing riveted joints using shell elements in crash analysis. In this paper, simulations of the self-piercing riveting process using LS-DYNA are presented. An implicit solution technique with r-adaptivity has been used. The advantages and the limits of using r-adaptivity in this class of metal forming process are discussed. In addition, parametric studies on important parameters for the forming process, i.e. friction, mesh size and failures criteria are presented. Finally, the mapping of data, the 3D simulation of the rivet specimen and the comparison with experimental results are presented.

Transient Response of a Projectile in Gun Launch Simulation Using Lagrangian and ALE Methods

Ala Tabiei – University of Cincinnati, Mostafiz R. Chowdhury – U.S. Army Research Laboratory

This paper describes the usefulness of Lagrangian and arbitrary Lagrangian/Eulerian (ALE) methods in simulating the gun launch dynamics of a generic artillery component subjected to launch simulation in an air gun test. Lagrangian and ALE methods are used to simulate the impact mitigation environment in which the kinetic energy of a projectile is absorbed by the crushing of an aluminum honeycomb mitigator. Issues related to the effectiveness of these methods in simulating a high degree of distortion of Aluminum honeycomb mitigator with the commonly used material models (metallic honeycomb and crushable foam) are discussed. Both computational methods lead to the same prediction for the deceleration of the test projectile and are able to simulate the behavior of the projectile. Good agreement between the test results and the predicted projectile response is achieved via the presented models and the methods employed.

Validation of LS-DYNA Computer Code for Seismic Qualification of Reactivity Control Mechanisms

A.S. Banwatt, C. Manu, C. Yao – Atomic Energy of Canada Ltd.

Reactivity control mechanisms of CANDU reactors fall under two categories: The first are mechanisms to control the reactivity and power output of the reactor and the second are mechanisms to control the reactor and provide instrumentation for indication. In this paper the shut off mechanism, which is of the second category, is analyzed to seismically qualify it using LSDYNA, a general-purpose finite element computer code based on the explicit time integration method. One of the objectives of this work is to determine the drop time of the shut off mechanism that ensures the safe shut down of the reactor when required. This mechanism consists of a slender structure that extends over a relatively long travel. During the mechanism’s drop, the shut off rods are guided by stationary components, which results in surface-to-surface contact and friction. Drag and damping forces are also acting on the moving parts. Due to a built-in eccentricity in the mechanism, it generates forces in the horizontal directions while the reactivity mechanism is dropping. Maximum stresses during the drop of the mechanism are evaluated to demonstrate that the jurisdictional requirements for the various components are met. The results obtained from the finite element analysis are compared with those from static drop tests performed in the laboratory. The drop test results are used to modify the finite element model by fine-tuning various variables such as the drag force, spring constants, damping and friction coefficients between the components, etc. Once the model has been verified, the seismic motion is applied and the results are compared with test data from similar reactors. It is shown that the results of the analysis of the reactivity mechanism compare well with the test data and the deformation and stresses are well within the acceptable values. These results demonstrate that the LSDYNA code can be successfully applied to seismically qualify a CANDU reactivity control mechanisms.

Virtual Try Out and Process Optimization for an Innovative Conic Poles Production Concept

A. Anglani, G. Papadia – University of Lecce, Italy, A.Del Prete – Altair Engineering s.r.l.

This paper describes how the production Process for conic poles has been reviewed in order to provide innovative solutions for the forming process which has been considered the most critical operation. Finite Element Analysis using an explicit code has provided a virtual way to investigate possible solutions evaluating advantages or disadvantages before that any prototype tool has been developed. More than one solution was possible, FEA has given the chance to evaluate the more promising one which was based on a different forming philosophy, that is the usage of profiling forming, which has an innovative aspect if it is applied on conic shapes like in this case. Tools shapes and process parameters were tuned through a massive usage of numerical simulations. The defined innovative solution allows to cut the production times of a considerable amount with an higher quality for the final product.

VPG Solutions Using MotionView

Michael White – Altair Engineering

The MotionView® product has been extended in version 6.0 to support LS-DYNA input and output. MotionView is a template based pre and post processor with a long history in the automotive industry. An example of an automotive handling event, and several examples of durability events will be shown. A vehicle model with a complete powertrain (engine and transmission) will be simulated, to demonstrate the “plug and play” templated model methods used by MotionView. The Altair Swingset benchmark problem will be run in LS-DYNA, and the results of this will be shown, to illustrate a consumer products application of the tool.

Vulnerability of Bridge Piers to Impact by Heavy Vehicles

Sherif El-Tawil – University of Michigan

My talk presents work undertaken to investigate the effects of vehicle collision on bridge piers. Inelastic transient finite element simulations are used to investigate the structural demands on bridge piers generated during such events, which have occurred in the past, sometimes with catastrophic consequences. Two different types of trucks and two different bridge/pier systems are used in the simulations. The approach speeds for the trucks range from 55 to 135 kph. Various quantities of interest are extracted from the finite element results and used to develop a better understanding of the vehicle/pier crash process and to critique current specifications addressing such events.