11th International LS-DYNA Conference

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Detroit, 2010
A Brief Look at *MAT_NONLOCAL: A Possible Cure for Erosion Illness?

Leonard Schwer – Schwer Engineering & Consulting Services

The computational mechanics literature dealing with damage and failure is filled with work addressing what is termed mesh regularization techniques. These various techniques seek to eliminate, or minimize, the numerical artifact of strain localization. LS-DYNA® provides a technique for attempting to regularize meshes with damage and failure via the keyword *MAT_NONLOCAL. The non-local implementation in LS-DYNA is based on the work of Pijaudier-Cabot and Bazant (1987). The non-local treatment basically attempts to average damage/failure values of neighboring elements to minimize the mesh dependency of the results

A Comparison of recent Damage and Failure Models for Steel Materials in Crashworthiness Application in LS-DYNA

Dr. André Haufe (Dynamore GmbH), Frieder Neukamm, Dr. Markus Feucht (Daimler AG), Paul DuBois (Consultant), Dr. Thomas Borvall (ERAB)

With increasing requirements on crashworthiness, and light-weight car body structures being a central issue in the future of automotive development, the use of high strength steel grades has become wide-spread in modern vehicles. Since these materials all too often show significantly lower ductility than conventional steels, it is of great importance to precisely predict their failure in crash loading conditions. Hence constitutive models in crashworthiness applications need to be able to correctly predict damage and failure mechanisms. These aforementioned, enhanced models are regularly based on a larger number of variables that define the loading history based on stress or strain measures and on accumulated plastic strain and damage variables more or less accurate. Moreover, these models may require initialization with locally computed history properties prior to a crashworthiness simulation in order to predict the subsequent loading response correctly. Furthermore it should be mentioned that orthotropic properties of steel sheets play a major role in the forming process. Hence one may expect that orthotropic behaviour in damage accumulation may also be a major mechanism when failure prediction along the forming-to-crash process chain is evaluated. It is therefore of great importance to not only evaluate the many available models in LS-DYNA based on their performance achieved in crash loading scenarios but also take the production step with mapping of history data into account. The present paper will focus on the different models available in LS-DYNA, e.g. Gurson, Johnson-Cook, GISSMO etc. and discuss the advantages and disadvantages in application, calibration and predictive performance in the light of the producibility-to-servicability simulation chain.

A Contribution to New ALE 2D Method Validation

Nicolas VAN DORSSELAER, Vincent LAPOUJADE – Alliance Services Plus,

Since LS-DYNA® v971 r4, a new ALE 2D method is available. Several finite element studies were performed by AS+ to evaluate the precision of this method in pure Multi-Materials Euler studies . Pure Multi-Materials Euler was tested on Impacts and Explosives studies from Defense and Spatial fields. A High Velocity Impact, a Long Rod Penetration, an Explosively Formed Projectile, a Shaped Charge Jet and an Air Blast were modeled using 2D axisymmetric models. Results were compared to experimental data extracted from reference papers. The very good precision obtained with the 2D ALE method and its ability to represent very dynamic phenomenon will be shown.

A New Development in Pedestrian Safety: The FLEX-PLI GTR LS-DYNA Model

Chirag S. Shah, Fuchun Zhu, Roel Van De Velde, Robert Kant – First Technology Safety Systems

The lower limb is one of the most frequently injured body regions in crashes involving pedestrians. A biofidelic FLEXible-Pedestrian Legform Impactor Global Technical Regulations (FLEX-PLI GTR) device has been developed under directions of the Flex-PLI Technical Evaluation Group (FLEX-PLI TEG). First Technology Safety Systems (FTSS) is developing a LS-DYNA model in addition to the hardware counterpart. The FLEX-PLI GTR is the latest development and successor of the earlier GT version. The FLEX-PLI GTR device has three regions: femur, knee and tibia. Outer rubber and neoprene foam layers represent the skin and flesh. The femur and tibia regions are segmental to achieve flexible bending behavior representing human like responses during pedestrian crashes. The central bone cores of the tibia and femur have bending moment measuring capabilities at several locations. The knee region has ligament elongations measuring capabilities to be used as injury criteria in regulations. This paper documents the development and dynamic validations of the FTSS FLEX-PLI GTR LS-DYNA model. The model geometry and inertia properties are obtained from available drawings and hardware. The model connectivity and structural integrity are inspected by experiments and verified against hardware. The model material properties are implemented from material test data. The model is then validated against dynamic calibration test for FLEX-PLI assembly without outer skin, and a full legform test against a flat rigid impactor (called inverse test). The femur and tibia bone bending moments and knee ligament elongations from the model output are compared to test data to evaluate model performance and injury predictability. The FTSS FLEX-PLI GTR LS-DYNA model revealed very promising performance in all validation cases and can be potentially used in future pedestrian safety regulations. The model has a 0.85 micro second time step and was found to be very cost effective (in terms of CPU times) and reliable for pedestrian safety simulations.

A New Method for the Structural Optimization of Product Families

Larsgunnar Nilsson – Engineering Research Nordic AB, Michael Öman – Scania CV AB

This paper discusses the problem of structural optimization of product families subjected to multiple load cases, evaluated by computationally costly finite element analysis. Product families generally have a complex composition of shared components that makes individual product optimization difficult as the relation between the shared variables is not always intuitive. More optimal is to treat the problem as a product family optimization problem. For product families subjected to multiple and computationally costly crash loads, however, the optimization problem takes too long time to solve with traditional methods. Therefore, a new optimization algorithm is presented that decomposes the family problem into sub-problems and iteratively reduces the number of sub-problems, decouple and solve them.

A New Strain Rate Dependent Spot Weld Model for Automotive Crash Applications

Dr. P.K.C. Wood – University of Warwick, Mr. M.A. Buckley – Jaguar and Land Rover, Dr. B. Walker – Ove Arup and Partners, Mr. T. Dutton – Dutton Simulation

New spot weld failure models in a range of sheet steels have been developed for use in the virtual testing of automotive crash structures to ensure compliance to international safety requirements. The desire to balance the cost to develop the data input to spot weld failure models and their capability to predict failure in simulation tools is central to the method. Full vehicle crash simulations suggest confidence in the predictive capability of the models. This paper describes a strain rate dependent spot weld failure model for use with hexahedron (solid) elements. A spot weld may comprise one, or a cluster of four, eight or sixteen solid elements. The enhanced functional capabilities of the new spot weld model allow a force-based failure for a solid element in which maximum shear force and tension force may be a function of strain rate, and each may each be defined uniquely using a load curve. Further the strength hardening effect at higher strain rate may be defined for the solid element using a simple constitutive expression which relates the properties of the spot weld to plastic strain rate. The new model has been programmed and tested in the finite element software code LS-DYNA®. The results suggest the new spot weld model is capable of reproducing the quasi-static and high rate physical test responses with a high degree of accuracy.

A Simple, Efficient and Robust Way to do Binder Wrap Simulation with LS-DYNA Implicit Solver

Kaiping Li, Yang Hu – ASME, Chrysler Group LLC, Xinhai Zhu – Livermore Software Technology Corp.

With the newly improved LS-DYNA implicit solver, the possibility to use it for binder wrap simulations of Stamping Process becomes reality. The importance of binder wrap simulation can never be overly emphasized since it will not only approve or disapprove the concepts of binder shape design, hence the whole addendum development of stamping process, but also impact the final results of stamping process simulations.

A Study of Mapping Technique for Air Blast Modeling

Vincent LAPOUJADE, Nicolas VAN DORSSELAER – Alliance Services Plus, Sandrine KEVORKIAN, Karine CHEVAL – Institut de Radioprotection et de Sûreté Nucléaire

Since LS-DYNA® v971 r4, a new 2D ALE method with an associated Mapping technique is available. Mapping enables the decomposition of a calculation in several steps: at the end of a 2D ALE calculation, data from the last cycle can be mapped into another 2D or 3D mesh. Several finite element studies of Air Blast were modeled to evaluate efficiency and potential of this new LS-DYNA feature. First, an influence study was performed to evaluate the impact of the mesh characteristic length variation during the Mapping on shock wave both on pressure peaks and impulses. The analysis is focused on the evaluation of the loss due to the Mapping technique. Then, a comparison with experimental data on a simple 2D study of air blast using Mapping technique was performed. The very good precision obtained with the 2D ALE method and its ability to represent air blast phenomena will be shown.

A Study on the Scalability of Hybrid LS-DYNA on Multicore Architectures

Yih-Yih Lin – Hewlett-Packard Company

In this paper, the effects of differences in problem size, number of cores per processor, and interconnect on the Hybrid LS-DYNA’s performance are studied. The result shows that combination of these three factors determines when Hybrid LS-DYNA has a performance advantage over the MPP LS-DYNA.

Advanced Mode Analysis for Crash Simulation Results

Clemens-August Thole

Potential scatter of simulation results caused for exampleby buckling, is still a challenging issue for the predictability. Principle component analysis (PCA) is a well-known mathematical method for data analysis. In order to characterize scatter PCA analysis was applied to the simulation results from a number of runs using all node positions at all time steps. For industrials relevant problems the size of the data base is larger than 100 GBytes (even, if compressed by FEMzip1[7]) . As a result the major components dominating the differences between the simulation results are available. Since PCA is a mathematically based method, the selected modes do not separate different physical effects like buckling at different parts of the model. PCA rather tries to maximize the variations by combining several physical effects into one mode. Difference PCA(DPCA) applies PCA analysis to the results for each part and time step. By analysis of the related covariance matrices, the local dimension of the scatter subspace can be identified and correlation between the scatter at different places can be analyzed. Using DPCA, different origins of scatter can be identified and physically meaningful components can be determined. The paper introduces the approach and shows results for an industrial model.

Advancements in Material Modeling and Implicit Method for Metal Stamping Applications

Xinhai Zhu, Li Zhang – Livermore Software Technology Corporation

A review of recent developments in stamping manufacturing will be conducted. The review will be focused on discussions surrounding new features related to static implicit binder wrap, advanced material modeling with Yoshida’s non-linear kinematic hardening in conjunction with Hill’s 1948, Barlat 1989 and Barlat 2000 yield criteria.

Advances on the Incompressible CFD Solver in LS-DYNA

Facundo Del Pin – Livermore Software Technology Corporation

The present work will introduce some of the resent developments in the Incompressible CFD (ICFD) solver currently under development in LS-DYNA. The main feature of this solver is its ability to couple with any solid model to perform Fluid-Structure interaction (FSI) analysis. Highly non-linear behavior is supported by using automatic re-meshing strategies to maintain element quality within acceptable limits. In this work we will introduce the additional features for conjugate heat transfer, turbulence model, biphasic flow, some new feature in terms of mesh generation like boundary layer meshing and MPP.

ALE Incompressible Fluid in LS-DYNA

Mhamed Souli – University of Lille

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

An Assessment of the New LS-DYNA® Multi-Layered Solid Element: Basics, Patch Simulation and its Potential for Thick Composite Structural Analysis

Thorsten Schütz – Adam Opel GmbH, Anton Matzenmiller – Univ. of Kassel, Madhukar Chatiri – CADFEM GmbH

Limitation of fossil fuels and global warming favor the introduction of new powertrain concepts for road vehicles with highest efficiency and low greenhouse gas emissions. Fuel cell vehicles offer the highest potential for sustainable mobility in the future. One major component of fuel cell vehicles is the hydrogen storage system. A promising and currently the most-used approach is to store hydrogen in wet-wound carbon fiber reinforced plastic (CFRP) vessels manufactured by a filament winding process with an operating pressure of up to 70 MPa (hereafter referred as H2 vessel). Due to the inherent complexity and the 3-dimensional nature, accurate behavior of such thick composite structures in impact simulations needs an adequate representation of the composite plies. Modeling thick composite structures with two-dimensional elements will produce inaccurate results in transverse normal direction. Therefore, 3D modeling should be used but the idealization of each ply with one solid element leads to undesirably large models and is impractical for large structures. Hence, representation of several plies in one solid element and more such elements across the thickness is aspired. An improved multi-layered solid element showing excellent efficiency of CPU time is implemented in the code of LS-DYNA® Version 971 R4. Like any brick element, it resolves the 3D stress state necessary for impact directions normal to the outer vessel surface. The element allows the definition of multiple integration points through the thickness in order to account for stacks of plies with arbitrary fiber orientation. By defining several layers with different material properties and ply orientations inside one multi-layered solid, the number of elements through the thickness is remarkably reduced and still, the result is close to the one obtained from the detailed finite element model of one brick element per layer. As depicted in Fig.1.2, a complex laminate configuration consisting of 18 different plies with varied fiber angles is represented by one multi-layered solid element with 18 integration points through the thickness. The above new element formulation is presented in this paper describing simulation results for both, different patches and for thick composite structures such as for hydrogen storage H2 vessels.

An Improved 3D Adaptive EFG Method for Forging and Extrusion Analysis with Thermal Coupling in LS-DYNA

Hongshneg Lu – Shanghai Hengstar Technology Co. Ltd., C. T. Wu – Livermore Software Technology Corporation

The 3D adaptive EFG method using conventional moving least-square approximation or fast transformation method [1] has been successfully applied to metal forging and extrusion analysis thanks to its high accuracy in dealing with large material deformation [2] in LS-DYNA. Recently, a meshfree convex approximation [3-5] was developed to be an alternative in the large deformation analysis. However, its application to the adaptive method has not been investigated. In this paper, an improved version of 3D adaptive EFG method with emphasizing on the modified maximum entropy approximation, whose approximation is non-negative and owns Korncker-Delta propriety at the boundary, is presented. The thermal effect in forging and extrusion problem is considered, and a scheme to interpolate the thermal state variables during the adaptive procedure is proposed.

An Integrated Process for Occupant Safety Simulations with LS-DYNA & MADYMO Coupling

Cédric Canadas, Tom Van Langenhove, Christophe Liefooghe – LMS International, Paul van Catz, Peter Ritmeijer – TASS

This paper presents an innovative integrated process to perform occupant safety simulation with LS-Dyna & Madymo coupling. More than ever before, the automotive industry operates in a highly competitive environment. Manufacturers must deal with competitive pressure and with conflicting demands from customers and regulatory bodies regarding the vehicle functional performance, which forces them to develop products of increasing quality in even shorter time. To address these challenges and deliver optimal collaboration between design and engineering, the integration between CAD and CAE is key. Through a strong link between CAD and CAE, along with the integration of all simulation steps in one environment, new methodologies are developed, allowing the full utilization of parametric geometry based analysis, enabling quick “what if” scenarios simulation, and thus front-loading design with simulation. Complex CAD based assembly is fully automated, reducing the risk of modeling mistakes. Moreover, repetitive tasks such as definition of the model symmetry, are performed automatically. These functionalities allow crash engineers to focus on the impact/safety simulations set up and not on the model construction. LMS Virtual.Lab is fully integrated with Dassault System CATIA V5, therefore seamlessly linking CAD with CAE. In the field of occupant safety, Virtual.Lab pushes the integration a step forward through the support of Madymo Coupling Assistant. Tedious dummy positioning and coupling contact creation becomes straightforward with the visualization of the Madymo dummy in its LS-Dyna FE model environment. A real life industrial case is presented consisting of a CAD based assembly of a door sub-system is performed automatically through automation, and then integrated within a quarter body in white. A Madymo dummy is then positioned wrt the vehicle model, allowing to define coupling simulation of a side impact with LS-DYNA and MADYMO solvers. Back to back comparison of traditional CAE and the proposed new methodology is highlighted to provide a measure of the savings that can be realized.

An LS-DYNA Model for the Investigation of the Human Knee Joint Response to Axial Tibial Loadings

Dr. Chiara Silvestri, Doug Heath, Prof. Dr. Malcolm H. Ray – Worcester Polytechnic Institute

Automotive accidents frequently involve fracture of the knee joints which can be related to either bone or soft tissue injuries. Previous studies show that the degree of anterior-posterior constraint of the femur bone along its longitudinal axis plays a crucial role in determining the knee-joint-fracture mechanism and internal tibial-femoral load distribution. Also, the anatomical tilt of the tibial plateau, tibial-femoral joint compression results in anterior displacement of the tibia, which has important implications in the prediction of knee injury and might lead to anterior cruciate ligament rupture. This study aimed at validating an existing finite element LS-DYNA® human knee joint model for replication of these complex failure mechanisms when the joint is subjected to tibial axial compression loads. Simulations were run with the joint at 90 ̊ flexion to investigate the effects of anterior-posterior joint constraint on the injury patterns. Comparisons between simulations findings and test outcomes from literature were compared in terms of anterior- posterior and medial displacements of the femur, proximal rotation of the tibia and tibial-femoral load distribution. The finite element model predicted similar injury patterns and internal loads resulted with cadaveric specimen testing. The validated numerical model can be integrated in a complete replication of the human lower extremity and employed in simulations of knee-bolster impacts with the human leg during car crashes. It would be used to predict leg injury patterns with the knee joint subjected to simultaneously axial loading of the femur and the tibia bones.

An MPP Version of the Electromagnetism Module in LS-DYNA for 3D Coupled Mechanical-Thermal-Electromagnetic Simulations

P. L’Eplattenier, C. Ashcraft – Livermore Software Technology Corporation, I. Ulacia – Mondragon Goi Eskola Politeknikoa

A new electromagnetism module is being developed in LS-DYNA for coupled mechanical/thermal/electromagnetic simulations. One of the main applications of this module is Electromagnetic Metal Forming (EMF). The electromagnetic fields are solved using a Finite Element Method (FEM) for the conductors coupled with a Boundary Element Method (BEM) for the surrounding air/insulators. Both methods use elements based on discrete differential forms for improved accuracy . Recently, a Massively Parallel Processing (MPP) version of the EM module was developed allowing sharing the CPU and memory between different processors and thus faster computations on larger problems. The implementation of the FEM and BEM in MPP will be presented. The EM module will then be illustrated on an actual EMF case. Experimental and numerical results will be compared and the speed-up of the MPP version will be studied. Finally, a new contact capability for the electromagnetic fields will be presented and illustrated on a rail gun simulation.

An Overview of LS-OPT Version 4.1

Nielen Stander, Tushar Goel – Livermore Software Technology Corporation

The main focus of the LS-OPT V4.1 development has been to further expand the graphical postprocessor and to significantly improve reliability, usability and transparency when distributing solver jobs across networks. Much of the latter has been accomplished through industrial collaboration. While LS-OPT originated as an LS-DYNA® based tool, new features are increasingly being developed to facilitate interfacing with non-LS-DYNA solvers. This is necessitated by the increasing requirement for conducting multidisciplinary optimization, thereby involving more than one solver type. Therefore, in V4.1, LS-OPT now has MSC NASTRAN support for mode tracking and frequency extraction. A generic extractor has also been added to aid result extraction from text files.

Analysis and Design of Large-Scale Civil Works Structures Using LS-DYNA

David DePolo, Eric Kennedy, Thomas Walker, Ryan Tom – US Army Corps of Engineers

The Folsom Joint Federal Project (JFP) Auxiliary Spillway is a high profile addition to the Folsom Dam, located approximately thirty miles upstream of Sacramento, California. Total concrete placements on the project will exceed 140,000 cubic yards at a projected cost of nearly $1 billion. The main component of the JFP is a large concrete control structure with steel bulkhead gates, submerged tainter gates, and post-tensioned anchorage. As a critical piece of the flood control system in a densely populated, active seismic region, the JFP demanded a rigorous analysis of a scale never before used by the U.S. Army Corps of Engineers to design a civil works structure. The Sacramento District of the Corps developed a three-dimensional LS-DYNA model of the control structure, foundation, and reservoir in order to capture the fluid-structure and soil-structure interaction during a seismic event, something not possible with standard dam analysis procedures. The model incorporated anomalies within the foundation; their effects were significant and could not have been established and properly accounted for without the LS-DYNA model. The analysis examined seven suites of ground motions and two pool elevations that envelope the expected demand on the structure. Results from the model were used for both evaluation and design purposes. This paper presents suggestions on the modeling of large scale civil works structures such as the JFP. Included is an overview of lessons learned regarding contact definitions and troubleshooting, the application and scaling of seismic input, and methods for accurately modeling the behavior and load paths. Extensive verification of the LS- DYNA results was conducted using another widely used finite element analysis program; the procedures and results are discussed. Additionally, the paper advises on items to be considered during model development, with a focus on generating output suitable for design.

Application of Topology Optimization for Crash with LS-OPT/Topology

Heiner Müllerschön, Katharina Witowski – DYNAmore GmbH, Nikolay Lazarov – University of Karlsruhe

Since end of 2009 a new software tool LS-OPT/Topology is available from LSTC. With LS-OPT/Topology nonlinear topology optimization with LS-DYNA can be applied for static and even for dynamic problems. The underlying method is Hybrid Cellular Automata (HCA) which is a heuristic, gradient-free approach. The objective is to obtain a structure with uniform internal energy density subject to a given mass fraction. In the current version LS- OPT/Topology-1.0, topology optimization with hexahedron solid elements, material *MAT_024 and some established contacts is possible for single and for multiple load cases. In this paper, first experience with the HCA-methodology and the application of LS-OPT/Topology to industrial problems is demonstrated. Capabilities and limitations of the new implementation will be highlighted.

Applying the Dynamic Relaxation Step to Determine Influence on Global Model Response from Shock Tube Loading for Mounted Hybrid III Head Neck Assembly

Emily Ward, Tim Harrigan – The Johns Hopkins University

Blast-induced traumatic brain injury (bTBI) is a critical issue for warfighter protection. Since bTBI has many features in common with injuries due to impact loading, the Hybrid III crash test dummy can be used to study many aspects of this injury, and the head-neck assembly of the Hybrid III dummy can provide a relevant initial bench test for computational studies of traumatic brain injury. LS-DYNA® has provided finite element models (FEM) of various Anthropomorphic Test Dummies (ATDs), and in this study the head-neck subassembly from the LSTC- NCAC 50th% Full FE H-III Dummy was used. To study the effects of blast on the head a shock tube experiment was simulated and the relevant loading conditions were applied to the head-neck assembly of the Hybrid III dummy FEM. The results were then compared to similar experimental test data. Since the initial tension in the neck cable of the Hybrid-III head-neck assembly is a key factor in the experimental response, simulating the initial tension in the neck cable is required in order to maintain a consistent boundary condition for the model. The neck cable definition in the Hybrid-III FEM was modified to include an initial stress, which was implemented using a dynamic relaxation step applied to initialize the model. The dynamic relaxation step is applied using explicit techniques and a sensitivity study is explored to understand impact of the initialization on the global response. The relative influence on the resulting global behavior response depends on the loading conditions.

Bolted Joint Representation in LS-DYNA to Model Bolt Pre-Stress and Bolt Failure Characteristics in Crash Simulations

Shailesh Narkhede, Nitin Lokhande, Bhavesh Gangani, Ganesh Gadekar – Tata Motors Ltd.

During the vehicle crash event (especially vehicles involving light and heavy commercial vehicles where bolted connections are predominantly used) bolted joints behavior, in terms of deformation and failure, play significant role in detecting the level of occupant protection offered by the vehicle structure. The current FE modeling techniques, for bolted joint representation in crash FE models, pose various limitations in terms of simulating the real life bolted joint behavior with explicit codes like LS-DYNA. The present bolt modeling techniques do not address the important aspects of bolted joint like • pre-load/pre-stress representation in the bolt, • bearing stresses between bolt shank and clamped plates, clamping forces between plates • Friction between bolts and plates and failure modeling of bolting joints. This paper describes FE modeling methodology, for bolted joint representation in crash FE models, for crash simulations using LS-DYNA. Two alternative options are proposed for modeling of bolted joint, either with beam element or with solid hexa elements so as to address the above mentioned aspects of bolted joint in crash simulations. The proposed FE modeling methodology is validated with theoretical calculations and experimental test results. The proposed bolt modeling methodology will help to achieve accurate prediction of structural behavior in crash load cases where bolted joints are predominantly used in crash load paths, such as cabin structure assessment with pendulum impacts, assessment of under run protections devices etc.

Book of Abstracts.pdf
Capabilities of Result Visualization in LS-OPT V4.1 – Demonstrated by Means of Industrial Problems

Katharina Witowski, Heiner Müllerschön – DYNAmore GmbH

During the last decade the optimization software LS-OPT has been used for design optimization, for DOE-studies, for system identification and for stochastic investigations in many industrial projects. LS-OPT became over the years a highly sophisticated software tool with very effective and reliable optimization methodologies particular suitable for highly nonlinear problems. This paper illustrates the capabilities of LS-OPT by means of several industrial applications. The focus is on the new post processing features of LS-OPT 4.1 such as visualizing results of multi-objective optimization, multiple load case optimization, sensitivity analysis and the visualization of curve data evaluated on the basis of meta-models. Of course, the objective and the setup of the optimization problems is discussed and demonstrated.

Comparison of FEM and SPH for Modeling a Crushable Foam Aircraft Arrestor Bed

Matthew Barsotti – Protection Engineering Consultants, LLC

Passenger aircraft can overrun the available runway area during takeoff and landing, creating accidents involving aircraft damage and loss of life. Crushable foam arrestor bed systems are often placed at runway ends to mitigate such overruns. As the aircraft tires roll through the bed, the material compaction dissipates energy, bringing the aircraft to a controlled stop. A detailed two-year analysis was conducted for the TRB Airport Cooperative Research Program to develop improved arresting systems (Barsotti, et al., 2009). A major thrust of the effort was the development of validated numerical models for crushable arrestor bed materials and deformable aircraft tires. Finite element models for the crushable material manifested several problems due to the unusual mode of deformation experienced, which included significant element skewing, heavy compaction (~90%), and high hourglass energies (~19%). Many meshing and hourglass mitigation strategies were attempted, but they produced only marginal improvement. The Smoothed Particle Hydrodynamics (SPH) method was adopted as a replacement, and detailed performance comparisons of the FEM and SPH versions were made. Error convergence studies using mesh refinement were performed for 1-D, 2-D, and 3-D cases, culminating in the comparison of full tire & arrestor models for each formulation.

Comparison of Lagrangian, SPH and MM-ALE Approaches for Modeling Large Deformations in Soil

Cezary Bojanowski – Argonne National Laboratory, Ronald F. Kulak – RFK Engineering Mechanics Consultants

Ongoing research at the USDOT funded Transportation Research and Analysis Computing Center (TRACC) at Argonne National Laboratory on bridge stability for bridges with piers in scour holes relies greatly on LS- DYNA® capabilities for modeling large deformations in soil and fluid structure interaction. When it comes to soil modeling, material model MAT_005 Soil and Crushable Foam is often used as a first approximation. It is especially useful when little material characterization is performed–which is usually the case for riverbed soil. Although an abundance of reports can be found where MAT_005 was used with the Lagrangian approach, its use in Smoothed Particle Hydrodynamic (SPH) and Multi Material Arbitrary Lagrangian – Eulerian (MM-ALE) approaches is considerably less documented. This paper presents a comparative study of the performance of MAT_005 with Lagrangian, SPH and MM-ALE approaches for predicting large deformation soil response. For the purpose of validation, simulations were performed for the in-situ experiment of a steel loading pad penetrating into silty clay sand. Using LS-OPT® metamodel based sensitivity analysis was conducted to identify the most relevant material and loading parameters. The results show that the three formulations can produce reasonable predictions at large penetrations. Although very suitable for soil penetration problems, MM-ALE requires iterative adjustments of contact parameters to eliminate spurious leakage. The LS-OPT sensitivity analysis on material parameters indicates the yield function parameters have the greatest influence on the results. Further important parameters are the soil density and appropriate modeling of the soil island boundaries. It was also noted that the choice of the type of domain decomposition greatly affects the compute time.

Crashworthiness Analysis of Finite Element Truck Chassis Model Using LS-DYNA

Yucheng Liu – University of Louisiana

This paper presents a detailed multi-purpose finite element model of a light duty truck chassis and evaluates this model in computational simulations of full frontal, offset frontal, and corner impacts. The simulation results are analyzed which correctly describe the characteristics and performance of a truck chassis during under impact scenarios. Through the validation and computational simulations, the presented model is proved to be computationally stable, reliable, repeatable, and useful for vehicle crashworthiness analysis. LS-DYNA is used for finite element modeling and crashworthiness analysis

Crashworthiness of Composite Structures with Various Fiber Architectures

Nageswara R. Janapala, Fu-Kuo Chang – Stanford University, Robert K. Goldberg, Gary D. Roberts, Karen E. Jackson – NASA Glenn Research Center

Advanced textile composite structures, such as braids and fabrics, are showing promising characteristics for energy absorption. However, modeling of these composite structures is quite challenging because of their complicated architecture, varied fiber/matrix combinations, and the failure mechanisms associated with them. Unfortunately, none of the existing material models is capable of simulating diverse failure behaviors observed during crushing of these composite structures. This paper will present a material model that can simulate the crushing response of composite structures with different fiber architectures. The material model identifies a smallest repeatable unit (i.e. unit-cell) within the textile composite and considers fiber modeling, strain rate effect, tow rotation and progressive failure criteria at tow level. The composite tow is assumed to be transverly isotropic, and modeled using an elastic- viscoplastic constitutive law. A DyCrash (Dynamic Crash) module is developed and implemented in LS-DYNA® as a user routine. The module is currently being validated for Kevlar fabrics. Results are presented for 00/900 and ± 450 Kevlar fabric coupons. A methodology is developed to back calculate the yarn properties from available Kevlar fabric test data using DyCrash.

Development of Hail Material Model for High Speed Impacts on Aircraft Engine

Yann CHUZEL,Alain COMBESCURE – LaMCoS INSA Lyon, Marco NUCCI, Yann PERRIN – Snecma Villaroche, Roland ORTIZ – Onera Lille

Hail impacts represent a threat for aircrafts and their engines. As experimental tests on aircraft engines are expensive and they can not be done in early stages of the development, numerical simulations to predict hailstone impacts on engine blades have to be developed. The purpose of this work is to present a new material model for simulating hailstone impacts on engine blades. Aeronautical industry has already developed numerical models for similar problems of bird impacts using LS- DYNA®. They simulate the bird using SPH particles to predict projectile failure and Lagrangian solid elements for the blade.. In order to simulate hail impact, numerical model for bird strike is used and projectile material is replaced by a new material model. Experimental results show hail has a brittle behavior which is similar to concrete’s, so mechanical behavior may be simulated by an elastic damage model based on Mazars’ law used for concrete. Damage Mazars’ model is improved by adding traction and compression damage and a delay effect is added in order to reduce mesh dependence. This hail law is developed in LS-DYNA code through a user defined material (UMAT), tested on simple cases of plate impact and used for impacts on the aircraft engine blade. This paper presents the existing LS-DYNA models simulating hail impact and their limits and describes hail tests used to study the material law and to develop the numerical model. Validation tests are presented to show out the behavior of hail, effects of model parameters, and the role of delay effect. Hailstone impact tests on an aluminum plate carried out by British Royal Aircraft Establishment (RAE) and Office national d’études et de recherches aérospatiales (ONERA) are used in order to identify the model. An impact on a blade is then simulated with the identified model and is compared with Snecma’s test.

Development of Parachute Simulation Techniques in LS-DYNA

Benjamin Tutt, Scott Roland – Airborne Systems, Richard Charles, Greg Noetscher – Natick Soldier Center

Parachute design often relies heavily on historical experimental data, and parachute development frequently requires numerous test campaigns. Although both of these techniques eventually result in successful parachute systems, such an approach will rarely result in any true advance to parachute engineering knowledge. Consequently, an unusually high emphasis is placed on experienced parachute design personnel, and often similar lessons have to be re-learnt over and again. Airborne Systems has been at the forefront of parachute modeling using Fluid Structure Interaction (FSI) techniques for the past 7 years. Significant advances have been made in parachute modeling using this powerful technology, many of which have been a direct result of US Army Natick Soldier Research, Development and Engineering Center funding and support. This paper presents the current “state of the art” parachute modeling at Airborne Systems using LS-DYNA. It discusses recent advances in simulating parachute performance and areas of future study. It documents fabric material modeling, wind tunnel class parachute analysis, parachute inflation studies, and comparisons with drop test data. A description of the modeling methodology is included as well as the application of the technology in a number of real world parachute applications including the old T-10 and the new T-11 US Army mass tactical assault parachutes.

Development, implementation and Validation of 3-D Failure Model for Aluminium 2024 for High Speed Impact Applications

Paul Du Bois, Murat Buyuk, Jeanne He, Steve Kan – NCAC-GWU

FAA William J Hughes Technical Center (NJ) conducts a research project to simulate failure in aeroengines and fuselages, main purpose is blade-out containment studies material testing performed by OSU ballistic testing performed by NASA/GRC numerical simulations performed by GWU-NCAC involved the implementation in LS-DYNA of a tabulated generalisation of the Johnson-Cook material law with regularisation to accommodate simulation of ductile materials previously published results in : A Generalized, Three Dimensional Definition, Description and Derived Limits of the Triaxial Failure of Metals, Carney, DuBois, Buyuk, Kan, Earth&Sky, march 2008

Developments in Line-Die Simulation and Exterior Surface Quality Check

Klaus Wiegand – Daimler AG, Li Zhang, Xinhai Zhu – Livermore Software Technology Corporation

A review of recent developments in stamping manufacturing will be conducted. The review will be focused in area surrounding the new line die simulation capabilities and in exterior surface panel quality check.

Drop Test into Water and Wave Impact Simulations of a Novel 7-Meter Plastic Boat with LS-DYNA

Martin Vézina, Arash Firoozrai – SimuTech Group Inc.

The US Congress, in its desire for a safer boat for the US Navy, contracted Stanley Widmer Associates Inc. to design and build a novel rotationally molded 7-meter boat using a patented “kiss-off” design. A first ever made prototype will be ready for trial in 2010. The material used for most of the boat, high density cross linked polyethylene, and the double hull with “kiss-off” design should, among other advantages, increase the boat’s impact resistance compared to fiberglass and aluminum boats. This paper presents numerical fluid structure interaction simulations done on the 7-meter boat, utilizing LS-DYNA, in order to investigate its structural integrity under water impact. Drop test into water simulations were done in the first phase of this numerical investigation. The boat was dropped at different heights and angles. A modal analysis was also done in Phase 1. A procedure to generate realistic waves was developed in the second phase. Explicit simulations with the boat going through waves at different velocities were done. A similar fiberglass boat was finally compared to the plastic design. Results from the drop test simulations and the modal analysis in Phase 1 clearly showed a critical flexural area. A modified design was run in Phase 2. LS-DYNA analysis results from Phase 2 predict that the plastic boat can go through 3-foot waves at 40 knots without damage while the fiberglass one has predicted damage at 30 knots. Overall, the numerical simulations show that high density cross linked polyethylene could be the new age of boating material.

EMAS Core Material Modeling with LS-DYNA

Yijian (Jack) Shi – Engineered Arresting Systems Corporation

With Lagrangian meshes and the LS-DYNA FEA explicit solver, Mat #63 – Crushable Foam is used to simulate the Phenolic foam – a candidate material for an EMAS core [7]. The simulated conditions include three scenarios: unconfined uniaxial compression, confined uniaxial compression and plate penetration into a large block. The three scenarios are purposely chosen for utilizing test data and validating simulation results. The simulations reveal that when an hourglass control is needed, the parameters for the control can significantly affect the results. The simulations with element formulations ELFORM=2 and 3 deliver better results than ELFORM=1. However, ELFORM=1 is the least expensive due to savings in computation time. ELFORM=3 is much more expensive than ELFORM=2 even with similar accuracy. When there is a symmetrical modeling condition, a reduced model size not only can save computational cost, but also sometimes can achieve greater accuracy. The simulation results are very sensitive to the value of TSC. For the very weak crushable material, a proper small value of TSC is preferred, instead of absolute zero. At extreme large deformation, the Lagrangian meshes may not work well because of extreme element distortion, which is observed in the scenario of plate penetration into a large block.

Engine Impeller Sub-Fragmentation Simulation Using EFG Method

Shoufeng Hu – Hamilton Sundstrand, C. T. Wu, Yong Guo – Livermore Software Technology Corporation

Engine impeller burst containment test may lead to the impeller sub-fragmentation. The containment of the impeller debris from sub-fragmentation presents a new challenge, because of the unpredictable pattern of dynamic fracture. In this study, the capability of EFG failure method in predicting the dynamic fracture of the ductile material, used for the engine impeller under impact loading, is demonstrated. In the EFG method, the combination of fast transformation method and meshfree visibility approach with cohesive fracture is proven to be an efficient way to model the progressive fracture in a general three-dimensional problem. In this study, the Mode-I fracture is adopted and the crack is assumed to propagate cell-by-cell in the direction of maximum principal stress. The meshfree visibility approach is introduced to impose the strong-discontinuity in the meshfree approximation as well as to compute the displacement jump in the initially rigid cohesive model.

Experimental and Numerical Testing of the V50 Impact Response of Flexible Fabrics: Addressing the Effects of Fabric Boundary Slippage

Gaurav Nilakantan, Michael Keefe, John W. Gillespie Jr. – University of Delaware, Eric D. Wetzel, Richard Merrill, Travis A. Bogetti, Rob Adkinson – US Army Research Laboratory

The impact testing of woven fabrics comprised of high strength and high modulus yarns is probabilistic in nature. This paper presents results from the experimental impact testing of 50.8 mm×50.8 mm scoured Kevlar S706 fabric samples held on four sides and impacted at the center by a 0.22 caliber ball bearing projectile. The V50 velocity response is obtained by performing impact experiments over a range of velocities and fitting the data to a normal distribution function. The impacted fabric samples show varying extents of slippage from underneath the fixtures. The effect of clamping pressure on the extent of fabric slippage is studied by varying the torque on the four bolts used to hold the fixtures together. Results from the experimental testing are compared against numerical predictions which did not consider fabric slippage effects. A simple new method to numerically model fabric slippage is developed and implemented into our computational probabilistic framework. Simulations are run using a Langlie method to obtain the new V50 velocity response of a Kevlar S706 fabric with spool based strength mappings and with boundary slippage present. Comparisons are then made between the experimental and numerical results.

FE Modeling of Innovative Helmet Liners

D. Hailoua Blanco, A. Cernicchi – Dainese S.p.a, U. Galvanetto – University of Padua

A key component of a safety helmet is the energy absorbing liner, which absorbs the greatest portion of impact energy during an accident. The aim of the present work was to study innovative structures for energy absorption that minimize the likelihood of head injuries for standard impact cases. The innovative helmet liner consists of an ABS plastic lamina with deformable cones on it. Energy is absorbed via a combination of folding and collapsing of the cones. The main advantage that such liner may introduce over common EPS pads is that it allows a better optimization of energy absorption for different impact sites and configurations. Numerical crash simulations of the novel liner employed in a ski helmet were carried out with LS-DYNA®. The model reproduced the testing conditions defined by the standards EN1077. Experimental and numerical results were compared and possible causes of discrepancies were discussed. The finite element model so validated paves the way for a future numerical parametric optimization of the novel structure. Keywords: Helmet, Crashworthiness, Energy Absorbing Structures, Drop testing

Finite Element Modeling and Validation of Guardrail Steel Post Deflecting in Soil at Varying Embedment Depths

Nauman M. Sheikh, Akram Y. Abu-Odeh, Roger P. Bligh – Texas A&M University System

This paper presents finite element modeling and validation of roadside guardrail steel posts deflecting in soil. The soil model was validated for posts embedded at various depths. Prior to finite element modeling, several drop- pendulum impact tests were conducted to determine the actual response of the soil-post interaction in dynamic impacts. A decrease in the depth of the post significantly increased the deflection in soil, which complicated the modeling of the soil behavior. Finite element model of the post and soil setup was developed to capture the post-soil behavior observed in the tests. Two material models, Geological Cap and Jointed Rock, were evaluated for use in the finite element model. Additionally, Lagrangian and Smoothed Particle Hydrodynamics (SPH) methods were briefly compared to determine suitability of use. It was determined that the Jointed Rock material model is better capable of capturing the soil-post interaction in cases where the post embedment was reduced and the resulting soil deformation was large.

Fluid Structure Interaction (FSI) Applications to Consumer Products

Jean V. Seguro – The Procter & Gamble Co.

Manufacturing consumer products and among them disposable absorbent products is very complex, not only due to the number of components that are assembled together, modified and packed but also because it has to be done at very high speed in order to compete in the ever more competitive disposable absorbent products industry. Creating models to represent such complex processes is very challenging for the above reasons and others like the very small thickness of the materials and their particular properties. Representing these processes using Finite Element Analysis (FEA) has been a growing practice at The Procter & Gamble Co. (P&G) for quite some time and in recent years complexity has been added to the models by including fluid representations, therefore developing Fluid Structure Interaction (FSI) models which in many cases are needed to better represent the processes we want to model. In this paper some basic settings of FSI models are described. By using the *Constrained_Lagrange_In_Solid keyword and other necessary keywords it is possible to simulate the interaction of the flimsy structures representing the disposable absorbent products materials with the air that surrounds them, while traveling at high speed. Then the paper goes on to showcase some of the models that have been successfully developed and validated (trim removal, folding and component ribbon handling), all of these models involve the interaction between flimsy structures and air. Validation of the models has been very important to gain confidence in the capabilities and some of the validation data is shared in this paper which shows great agreement between the models’ predictions and the data collected during the experiments. This paper demonstrates how FSI models developed using LS-DYNA® successfully represented manufacturing processes of disposable absorbent consumer products involving flimsy structures and fluids interacting at high speed.

Heat Transfer Simulation to Determine the Impact of Al-5Mg Arc Sprayed Coating onto 7075 T6 Al Alloy Fatigue Performance

G. D’Amours, B. Arsenault, F. Breton – National Research Council Canad, D. Dubé – Université Laval

Aluminum-5% magnesium coatings was deposited by arc spraying onto aircraft Al 7075 T651 structural alloy for corrosion protection while required to maintain the substrate material fatigue performance integrity. Fatigue performance of coating system is complex and in order to better understand the variability of the fatigue performance of coatings, heat flow in substrate was studied and simulated to determine the temperature evolution during arc spraying in both substrate and coating for different process parameters. Experimental temperature measurements, theoretical calculations and simulation were carried out to extrapolate the coating temperature with respect to coating process variables and surface preparation. Both flux and conductance were identified by an inverse method to reproduce experimental temperature measurements. The thermal transient solver of LS-DYNA® was used to simulate the time-dependence of heat flux in the coating during successive depositions. The benefit of that model is its capability to predict the temperature distribution and evolution in time in a sample. Samples were made of Al 7075 T651 alloy and were 80 mm in length by 25 mm wide and 7 mm thick. A coating thickness of 250 μm was reached. It was the spray thermal energy that was taken into account in the model as the thermal load. The quality of the thermal contact between the substrate and coating was also included in the model and conductance was defined to control the amount of heat transferred at the interface. Coating performance was evaluated in term of fatigue properties, bond strength, and interface quality of as deposited coatings. The superior fatigue resistance of the coated alloy relies on low heat input process parameters and surface preparation that favor high interface conductance to keep low coating temperature during the coating process. Surface preparation, arc current and atomizing gases play all a key role to provide a fatigue resistant coating.

High Fidelity In-Bore Pressure Modeling

Michael M. Chen – U.S. Army Research Laboratory

Significant research efforts have been conducted to gain an in-depth understanding of projectile-weapon interactions at the U.S. Army Research Laboratory. The objective of this paper is to increase the fidelity of in-bore modeling and simulations that will facilitate the development of component and system models for U.S. Army weapon systems. Specifically, the in-bore pressure as a projectile travels through a gun tube, which has been known to be spatially and temporally varying distribution, will be programmatically taken into account in finite element analysis of launch dynamics. A computer program that embeds IBHVG2 Interior Ballistics code was implemented to automate the process. This tool can apply a substantial number of pressure curves to the corresponding barrel locations and generate LS- DYNA® compatible keyword files for analysis. The approach yields better accuracy and eliminates tedious manual efforts. In short, the development greatly streamlines the modeling efforts and significantly increases the fidelity of in-bore pressure modeling.

How to Use the New CESE Compressible Fluid Solver in LS-DYNA

Zeng-Chan Zhang – Livermore Software Technology Corporation

This new solver is based on the conservation element and solution element (CESE) method[1, 2]. The CESE method is a novel numerical method for solving conservation laws, and it has many nontraditional features, such as: space- time conservation; high accuracy (2nd order for both flow variables and their spatial derivatives); novel shock- o capturing strategy; both strong shocks and small disturbances can be handled very well simultaneously, etc. o Because of these advantages, this CESE solver is a good choice for high-speed compressible flows with complex shocks and acoustic (noise) problems (near field). The solver has also been used to solve fluid/structure interaction (FSI) problems. For these problems, the fluid solver is based in an Eulerian frame while the structure solver is a Lagrangian frame. Their meshes are independent of each other, and the structural boundaries (fluid-structure interfaces) are tracked by the fluid solver automatically. The fluid solver gets the displacements and velocity of the interfaces from the structural solver and feeds back the fluid pressures (forces).

Implementation of the Tanimura-Mimura’s Strain Rate Dependent Constitutive Model in LS-DYNA Using User Defined Material Model

Dr. T. Tsuda – ITOCHU Techno-Solutions Corporation, Dr. S. Tanimura – Aichi University of Technology, Dr. A. Abe, Dr. M. Katayama, Dr. T. Sakakibara – ITOCHU Techno-Solutions Corporation

Tanimura-Mimura constitutive model covers a wide range of the strain rates and of a large strain, and enables us to use unified and common material constants to simulate the dynamic behaviors of materials and/or bodies. In this paper, dynamic behaviors of high speed tensile tests, buckling tests and crash test of a full vehicle are simulated by implementing this model in LS-DYNA®. Obtained numerical results are in good agreement with the experimental ones and the validity of the model has been demonstrated

Improvement of Energy Absorption for the Side Member Using Topography Optimization

Iku Kosaka – Vanderplaats R&D Inc.

This paper describes a design system to optimize the non-linear responses computed from LS-DYNA® using various optimization techniques, especially with large-scale (large number of design variables) optimization, and demonstrates the system as it improves the energy absorption for the side member of the vehicle. The proposed design system uses the equivalent static load (ESL) method, which requires the iterative process of non-linear structural analysis (LS-DYNA) and linear structural optimization (Genesis®). Unlike general-purpose optimization software packages, it does not require many analysis calls when a large number of design variables are used to design a structure. Therefore, non-parametric techniques, such as Topology, Topometry, and Topography optimizations, which often require thousands of design variables, can be easily employed. To demonstrate, the side member of the Dodge Neon was optimized to improve its energy absorption using Topography optimization.

Improvement of the Energy Absorption Capacity of an Intercity Coach for Frontal Crash Accidents

Muhammed E. Cerit, Mehmet A. Guler, Uğur Yolum – TOBB University of Economics and Technology Ankara, Bertan Bayram – TEMSA AR-GE VE TEKNOLOJİ A.Ş.

According to the accident statistics for buses and coaches, accidents involving frontal crash constitute an important percentage among all bus accidents. In this type of accidents, front body of the bus structure gets severely damaged and this puts the driver and crew in great injury risk. And most of the frontal crash accidents result in death of the bus driver. Because of this, the safety of both the bus driver and the crew should be ensured in the case of frontal crash accidents. Providing the driver’s safety is crucial since the driver is the key person for keeping the control of the bus in the event of an accident so that the safety of the passengers will be ensured. Even though the most of the passive safety standards are related to the safety of the passengers, some international regulations exist for the driver’s safety for heavy vehicles. The European regulation ECE-R29 is arranged to provide the safety of the truck cabin and the driver. This regulation involves a frontal crash pendulum test in which a plate with a specified mass strikes the cabin of the vehicle. A regulation specifically arranged for the safety of bus/coach in the case of frontal crashes does not exist, but some proposals similar to ECE-R29 are being discussed in Working Party on Passive Safety (GRSP) in United Nations Economic Commission for Europe (UNECE). Presumably, a similar regulation for buses will be imposed in the near future. In this paper, frontal crash analysis of the structure of a bus front body was performed according to the ECE-R29 European regulation requirements and the strength of the bus structure was checked whether the safety requirements are satisfied. The nonlinear explicit finite element code LS-DYNA® was used for the crash analyses. The first stage of this study involves the frontal crash analyses of the baseline bus structure without any improvements. At this stage the weak parts of the front end structure of the bus body were determined. In the next stage some improvements were made on the bus structure in order to strengthen the front body. These modifications include the rearrangement of the weak profiles forming the bus front structure. Finally the modified bus structure was compared with the baseline model if the requirements for the driver’s survival space were satisfied according to ECE-R29.

Investigation of *MAT_58 for Modeling Braided Composites

Brina J. Blinzler, Wieslaw K. Binienda – University of Akron, Akron Ohio, Robert K. Goldberg – NASA Glenn Research Center, Cleveland Ohio

An in-depth analysis is needed to simulate the impact behavior of triaxially braided composite materials. Before an impact simulation can be generated, all material input parameters must be found. The objective of this work is to use static tests conducted on axial and transverse coupons to determine these input parameters. In particular, analysis methods that capture the architecturally dependent damage observed in these tests in a computationally efficient manner are required. A macromechanical shell element based model for braided composites has been developed, in which the braid architecture is approximated as a series of four parallel laminated composites with varying fiber orientations. The composite damage model *MAT_58, available within LS- DYNA®, is used in this investigation. Careful investigation of the model’s global response, and local stress and strain distribution within each element of the composite unit cell are examined parametrically using various input strength parameters. From these studies, relatively small changes in the input parameters have been found to have a significant effect on the overall response, sometimes in non-intuitive ways. Thru this investigation the predictive capability of the developed braid model will be improved and a greater understanding of the functionality of the MAT_58 material model will be obtained.

Investigation of LS-DYNA Modeling for Active Muscle Tissue

Sebastian Mendes, Dr. Chiara Silvestri, Prof. Dr. Malcolm H. Ray – Worcester Polytechnic Institute

This study is aimed at investigating and comparing one-dimensional and three-dimensional finite element models of active muscle tissue. Skeletal muscle is a very complicated biological structure to model due to its non- homogeneous and non-linear material properties as well as its complex geometry. Additionally, forces generated from muscle activation are directly related to the muscle length and contraction velocity. Finite element discrete Hill-based elements are largely used to simulate muscles in both passive and active states. There are, however, several shortfalls to utilizing one- dimensional elements, such as the impossibility to represent muscle physical mass and complex lines of action. Additionally, the use of one-dimensional elements restricts muscle insertion sites to a limited number of nodes causing unrealistic loading distributions. These limitations are partially solved with a three-dimensional solid muscle model, where discrete Hill-based elements are combined in series and parallel to solid elements possessing hypo-elastic material properties. Despite some instability, the model was concluded to be an improvement over purely one-dimensional muscle models

Investigation of the Shear Thickening Fluid Dynamic Properties and its Influence on the Impact Resistance of Multilayered Fabric Composite Barrier

P.A. Mossakovsky – Moscow State University, A.M. Bragov – University of Nizhniy Novgorod, M.E. Kolotnikov, F.K. Antonov – FSUE “MMPP “Salut”

The results of experimental and computational study of properties of shear thickening fluid (STF) are observed. Two series of dynamic tests by the Split Hopkinson Pressure Bar method in rigid and soft casings are carried out to determine the dynamic bulk and shear properties of STF. A simplified mathematical model of the STF is formulated for the use in computer simulation of ballistic impact tests of multilayered fabric composite protective shells (Kevlar + STF). Numerical simulation is conducted with nonlinear LS-DYNA® code using ALE approach. The study confirmed the hypothesis about the possibility to describe STF behavior by a Newtonian fluid model in the characteristic range of strain rates. The parameters of shear viscosity and bulk compressibility of the model are defined. It is concluded that the contact interaction between STF and Kevlar basis is described by Coulomb friction law which is unnatural for fluid interactions. It is shown that the effectiveness of the STF impregnation is due to the facts of composite layers collapsing prevention and presence of internal friction.

Investigations of Generalized Joint Stiffness Model in LSTC Hybrid III Rigid-FE Dummies

Shu Yang, Xuefeng Wang – IMMI

The joint restraint model *CONSTRAINED_JOINT_STIFFNESS_GENERALIZED in LS-DYNA® provides users a way to define stiffness characteristics for joints defined by *CONSTRAINED_JOINT_OPTION. Based on the relative angles between two coordinate systems, moments are generated according to user-defined curves. It has been defined in LSTC Rigid-FE dummy models to describe the joint behaviors at limb joints such as hip, elbow and knee joints. There are two approaches in LS-DYNA® to calculate the relative angles, incremental update (default) and total formulation (option defined in *CONTROL_RIGID). In this paper, differences of the angular calculation of the two methods were investigated. In LSTC Rigid-FE dummy models, the default (incremental update) is used for the joint stiffness model. It demonstrates the shortcoming of the incremental update method for the joint that rotates about more than one axis. Consequently, joints at elbows and wrists in the Rigid-FE dummy models are limited to a single axis rotation, which are capable to rotate along two axes in a physical hybrid III dummy. Alternatively, a modified Rigid-FE dummy model with the total formulation method defined for the joint stiffness was then suggested.

Isogeometric Analysis in LS-DYNA

David J. Benson – UCSD

Isogeometric analysis: finite element analysis performed using the same basis functions as in computer aided design (CAD). CAD basis functions Implementing elements for specific basis functions Desire an ability to rapidly prototype new elements

Isogeometric Analysis: Introduction and Overview

T.J.R. Hughes – The University of Texas at Austin

Outline: Isogeometric analysis B-splines, NURBS T-splines Bezier extraction Research progress

Latest Developments in Crash Pre Processing and Post Processing – Innovative Ideas Brought to the Industry

L. Rorris – BETA CAE Systems SA

The increasingly demanding and complex requirements in Crash Analysis, call for continuous and innovative software development. BETA CAE Systems in an effort to meet and exceed the requirements of the industry is introducing new cutting edge technologies, both in the pre-processing area with ANSA, and in post-processing with μETA. This paper presents these new technologies. With the introduction of a new version of ANSA in 2009 a new user interface was presented. The new interface is a long-term effort to give the CAE engineer the capacity to work in a modern software interface environment leading in increased productivity and “ease-of-use”. Taking the burden of the hard pre-processing tasks away, it allows the user to take full advantage of the solvers capabilities. The effort is ongoing and further enhancements and developments throughout 2010 and the 13.x versions will lead to a totally new user workflow. At the same time, the development of highly specialized tools can greatly reduce the re- processing time by automating various difficult operations. A characteristic example is the introduction of an integrated multi-body solver that allows the manipulation of complex kinematic mechanisms of crash models (i.e. suspensions, seats, dummies, roof tops etc.). In the field of occupant and pedestrian safety, advanced tools that automate the procedures of target identification and impactor positioning allow the easy creation of corresponding load cases. Additionally, these tools give the possibility of further analysis types such as Robustness Analysis. In the area of post-processing, the advances are equally impressive in the latest μΕΤΑ versions. Better utilization of system resources, such as smaller memory footprint and a huge speedup in graphics performance, guarantee that the responsiveness and feel of the software environment won’t be compromised even by the largest models. Additionally, advanced functionality, like the direct calculation of section forces, provides the tools that are needed for the evaluation of the results. Recently, process automation tools are introduced, which together with advanced report generation features make the automation of post-processing much easier.

LS-DYNA “Model Compare” in Visual-Environment

Shivakumara H. Shetty, Velayudham Ganesa – ESI Group, Milind Parab – Mindware, Sreedhar Kandagatla – ESI Software (India) Pvt Ltd

A downturn in the industry drives companies to execute projects with fewer resources. The demand for product innovation and productivity improvements has increased exponentially. In order to meet the customers’ demand, ESI’s Visual-Environment provides new features and improvements to achieve productivity, better usability and workflow. One such new feature is “Model Compare”. Using “Model Compare”, a user can compare models to identify the changes in geometry and LS-DYNA entities such as material, section, contact and, constraints. These differences can be copied from one model to another. This feature improves productivity by eliminating manual bookkeeping. In this paper, the key features of Visual-Environment for LS-DYNA and usefulness of these features in FEA simulation are discussed with examples of productivity improvements and process automation.

LS-DYNA Analysis of a Full-Scale Helicopter Crash Test

Martin S. Annett – NASA Langley Research Center

A full-scale crash test of an MD-500 helicopter was conducted in December 2009 at NASA Langley’s Landing and Impact Research facility (LandIR). The MD-500 helicopter was fitted with a composite honeycomb Deployable Energy Absorber (DEA) and tested under vertical and horizontal impact velocities of 26 ft/sec and 40 ft/sec, respectively. The objectives of the test were to evaluate the performance of the DEA concept under realistic crash conditions and to generate test data for validation of a system integrated LS-DYNA® finite element model. In preparation for the full-scale crash test, a series of sub-scale and MD-500 mass simulator tests was conducted to evaluate the impact performances of various components, including a new crush tube and the DEA blocks. Parameters defined within the system integrated finite element model were determined from these tests. The objective of this paper is to summarize the finite element models developed and analyses performed, beginning with pre-test and continuing through post test validation.

LS-DYNA and JMAG Coupling Simulation for Change of SPM Motor Magnetic Properties Due to Press-Fitting

Kazuya Sato, Kazuyuki Narita, Hiroyuki Sano – JSOL Corporation

Press-fitting is one of the methods to keep the laminated structure of the motor core. It is known that the compressive stress due to press-fitting causes an increase of the core-losses. In this paper, the influence of the press- fitting stress on the motor magnetic properties was investigated using LS-DYNA and JMAG coupling simulation. JMAG is a comprehensive software suite for electromechanical equipment design and development. In this investigation, using LS-DYNA for press-fitting analysis, passing the results of the element data to JMAG, finally core-losses analysis was carried out by JMAG. From the results, the change of the magnetic properties due to press- fitting was clearly obtained.

LS-DYNA Best-Practices: Networking, MPI and Parallel File System Effect on LS-DYNA Performance

Gilad Shainer – HPC Advisory Council, Tong Liu – Mellanox Technologies, Jeff Layton, Onur Celebioglu – Dell

From concept to engineering, and from design to test and manufacturing, the automotive industry relies on powerful virtual development solutions. CFD and crash simulations are performed in an effort to secure quality and accelerate the development process. The recent trends in cluster environments, such as multi-core CPUs, GPUs, cluster file systems and new interconnect speeds and offloading capabilities are changing the dynamics of clustered- based simulations. Software applications are being reshaped for higher parallelism and multi-threads, and hardware configuration for solving the new emerging bottlenecks, in order to maintain high scalability and efficiency. In this paper we cover best practices for achieving maximum productivity through MPI optimizations, efficient networking utilization and usage of parallel file systems.

LS-DYNA Durability Load Cases: An Automated Template Driven Process Using the ANSA Task Manager

Yianni Kolokythas – BETA CAE Systems SA, Dietmar Fels, Matthias Weinert – Ford-Werke GmbH

Process organization and standardization are essential in a CAE turnaround cycle. In an era, where the vehicle development time is getting reduced and the number of load case analysis is getting increased, the need for automatic standard processes is increasing. Ford-Werke GmbH and BETA CAE Systems SA are cooperating to develop streamlined, automatic processes, using the ANSA Task Manager. The goal, of these template driven processes, are to create realistic, repeatable and robust durability simulation models. The ANSA Task Manager supervises the generation of the simulation models, while ANSA Data Management, in the background, facilitates the components management, ensuring that the engineering teams will always work with the most up-to-date data. The simulation model set-up becomes a repeatable and user-independent procedure, safeguarding the model quality and fidelity.

LS-DYNA Implemented Multi-Layer Fabric Material Model Development for Engine Fragment Mitigation

S. D. Rajan, B. Mobasher, A. Vaidya – Arizona State University

The development of a robust and reliable material model for dry fabrics is the main subject of this paper. Dry fabrics are used in a number of applications such as propulsion engines fan-containment systems, and soft body armor. A mechanistic-based material behavior model capturing the behavior of fabrics when subjected to impacts from high-velocity projectiles would make a powerful predictive tool. In this paper, the constitutive model for Kevlar® 49 is developed. Experimental static and high strain rate tensile tests have been conducted at Arizona State University (ASU) to obtain the material properties of Kevlar fabric. Results from laboratory tests such as Tension Tests including high-strain rate tests, Picture Frame Shear Tests, and Friction Tests yield most of the material properties needed to define a constitutive model. The material model is incorporated in the LS-DYNA commercial program as a user-defined subroutine. The validation of the model is carried out by numerically simulating actual ballistic tests conducted at NASA-GRC.

LS-DYNA Meshfree Interactive Adaptivity and Its Application

Wei Hu, C. T. Wu – Livermore Software Technology Corporation, Kei Saito – Engineering Technology Division, JSOL Corporation

The meshfree adaptive method has been developed and widely used as an important tool to deal with large topology change with severe local deformation in the application of 3D metal forming analysis. However, due to the complexity of material deformation, it is impractical to predefine the adaptivity before the actual analysis is performed. The interactive adaptivity will be an alternative to dynamically detect distortion and maintain the quality of meshfree discretization. In this work, we are going to present a new development on meshfree interactive adaptivity. Several control indicators are introduced to measure the local distortion in discretization as material deforms. When one or more indicators are beyond certain tolerance, which indicates the occurrence of severe shear deformation, large volumetric change, or unbalanced nodal distribution, meshfree interactive adaptivity is triggered. The user defined tolerance is carefully adjusted according to the history of material deformation to avoid the over-activation of interactive adaptivity. Several numerical examples will be presented to demonstrate the advantages of interactive adaptivity and compared to the traditional approach.

LS-DYNA on Advanced SGI Architectures

Olivier Schreiber, Scott Shaw, Brian Thatch – SGI Applications Engineering, Bill Tang – SGI Systems Engineering

LS-DYNA’s implicit solver integration with explicit software allows large time steps transient dynamics as well as linear statics and normal modes analysis. Until recently,this capability could only be run on large Shared Memory Parallel (SMP) systems,where the application had access to large memory address space of the model. Distributed Memory Parallel (DMP) implementation of LS-DYNA’s implicit solver now allows the factorization of smaller mass and stiffness matrices of the decomposed problem domain by corresponding tasks in less memory. Performance enhancement through SMP processing is moreover also available in the recently introduced ‘hybrid’ mode. This paper demonstrates how advanced SGI computer systems, ranging from SMP servers addressing large memory space through multi-node clusters can be used to architect and accelerate solutions to meet complex analysis requirements.

LS-OPT/Topology Version 1

Willem Roux, Tushar Goel – Livermore Software Technology Corporation, David Björkevik – Engineering Research AB

This paper presents LS-OPT/Topology, a new topology optimization tool. Topics such as its capabilities, current development directions, and integration into an industrial design environment are discussed.

LSTC / NCAC Dummy Model Development

Pradeep Mohan, Chung-Kyu Park, Dhafer Marzougui, Cing-Dao Kan – The George Washington University, Sarba Guha, Christoph Maurath, Dilip Bhalsod – Livermore Software Technology Corporation

This paper presents the modeling and validation status of the most commonly used crash test dummies in the regulatory and consumer crash test programs, the Hybrid III family of crash test dummies. Systematic modeling and validation procedures are established and adopted to ensure the accuracy, efficiency, robustness, and ease of use of the models. The procedures are based on the premise that the model must be based on the fundamentals of mechanics, focusing directly on component geometry and material mechanical properties. The dummy models are created and validated at the component level. The models are then integrated and re-evaluated at the system level. The paper presents the component and system level validation results of the HIII 50th and 5th percentile dummy models.

Mathematical Modeling of Asteroid Falling into the Ocean

A.V. Abramov, O.V. Voikina, I.V. Minaev -LLC “STRELA” Open Computer Center, V.A. Simonenko – RFNC Zababakhin Research Institute of Technical Physics, E.A. Abramov – South-Ural State University, N.A. Skorkin National Research Nuclear University “MIFI”

Today, experimental information about large-scale collision tsunami is not available. That is why one of the main tools of studies is mathematical modeling. This paper considers falling of stone asteroid with diameter 1 km into the ocean 4 km deep. This asteroid collides with the Earth at a speed of 22 km/s at angles 30, 60 and 90 degrees. Calculation of space body collision with a barrier is split into two stages. At the first stage, using finite-element code LS- DYNA® [1] and super computer SKIF-URAL of South-Ural State University under the support of OCC “STRELA”, the process of interaction of body with the barrier was calculated. Analysis of calculation data shows that for the angle of incidence 60 and 90 degrees, the results differ slightly. Even for the angle of incidence 30 degrees, we do not have big difference. That is why, one is to expect that the impact of tsunami on the sea shore for these angles of collision will be practically the same. Due to this reason, at the second stage of calculations, we considered the case of axisymmetric penetration of asteroid into the ocean. For describing cylindrically diverging surface wave and its impact on the shore with regard for the shelf profile, a special code was developed, in which approximation of shallow water was realized [3, 4]. It was given empirical formulae for calculation of the height of remote wave that is formed with underwater nuclear explosions [5]. Compared values are in good agreement. This means that using the approach to assessing the parameters of tsunami, which is proposed in this paper, is acceptable both for qualitative and quantitative description of this physical phenomenon. As tentative assessments showed, the aftereffects of the falling of a stone asteroid with diameter ~1 km may be destructive for the ocean shore. Calculations showed that the wave height on the shelf increases from 60 to 100 m. Then the wave height on the shallow water decreases.

Meshfree Analysis Using the Generalized Meshfree (GMF) Approximation

Chung-Kyu Park, Cing-Dao (Steve) Kan – The George Washington University, Cheng-Tang Wu – Livermore Software Technology Corporation

Meshfree methods are becoming widely used in many industrial fields since the finite element method (FEM) has inherent limitations, such as mesh quality and related distortion problems, to analyze sophisticated problems under large deformation. However, the meshfree methods also have their own deficiencies, mainly the high CPU cost. Recently, the generalized mesh-free (GMF) approximation is developed to improve the efficiency and accuracy in the conventional meshfree methods for solid analysis. The GMF approximation is the integrated formulation to generate existing approximations, such as moving least square (MLS), reproducing kernel (RK), and maximum entropy (ME) approximation, as well as new approximations based on the selection of a basis function. The GMF approximation has two excellent features. The one is that the GMF approximation naturally bears the weak Kronecker-delta property at boundaries, which makes the imposition of essential boundary conditions in meshfree methods easier. The other is that the GMF approximation can be extended to higher-order approximations, which can improve the accuracy of meshfree methods. In this study, some meshfree analyses are performed by LS-DYNA® to demonstrate the performance and accuracy of the GMF approximation. The results show that the convex approximation gives better performance and accuracy than the non-convex approximation in meshfree analysis.

Mode-based Frequency Response Function and Steady State Dynamics in LS-DYNA

Yun Huang – Livermore Software Technology Corporation, Bor-Tsuen Wang – National Pingtung University of Science and Technology

Two new features used for frequency domain structural analysis — frequency response function (FRF) and steady state dynamics (SSD), have been implemented in LS-DYNA, based on mode superposition techniques. As a characteristic of a structure, FRF is the transfer function which represents structural response resulting from applied unit harmonic excitations. The harmonic excitations can be given in the form of nodal force, base acceleration or pressure. The FRF feature provides user the opportunity to acquire a spectrum of structural response (displacement, velocity and acceleration) for the applied unit excitation. As a direct extension of FRF, SSD calculates the steady state dynamic response of a system subjected to a given spectrum of harmonic excitations. Both FRF and SSD give results in complex variable form, enabling user to obtain not only amplitude of response, but also phase angle. A benchmark example of a rectangular plate is included to demonstrate the effectiveness of both features. Some discussions regarding the effect of damping and individual mode contributions are also included.

Modeling Bird Impact on a Rotating Fan: The Influence of Bird Parameters

M. Selezneva, K. Behdinan, C. Poon – Ryerson University, P. Stone, T. Moffat – Pratt and Whitney Canada

The ability to withstand bird impact is one of the major requirements of the modern aircraft jet engine. In fact, rigorous certification procedures are put in place to assess the engine’s ability to sustain severe impact loads developed during bird impact. Full scale bird tests are expensive and time consuming, and call for the use of accurate numerical approximations during the design stages of engine development. The main difficulties encountered in achieving accurate finite element (FE) analysis are related to modeling of the bird which undergoes severe deformations, and modeling of the contact between the bird (soft) and blade (stiff) materials. Thus far Smooth Particle Hydrodynamics (SPH) modeling in LS-DYNA®, which is a meshless method, had shown potential in adequately modeling the bird and the bird-blade interactions. Recent publications also show the ability of SPH based models to capture impact strains and forces seen by the rotating fan blades [1, 2]. The current study further investigates the interaction of the SPH bird with the FE blades, and the ability of the model to capture realistic blade deformation. The main emphasis is placed on the effect of the bird related parameters on the damage sustained by the blades.

Modeling Blast Damage of Composite Structures

Bazle A. Gama, Venkat S. Chiravuri, and John W. Gillespie Jr. – University of Delaware

Blast loading on monolithic materials, sandwich structures, and composite flat plates and cylinders are investigated using LS-DYNA blast loading function and the progressive composite damage model MAT162. Energy dissipating damage mechanisms, momentum transfer, resistance forces, accelerations, and dynamic displacements are analyzed to understand the blast resistance behavior of the flat plates and the cylinders.

Modeling the Effects of Laser Peening on Friction Stir Welding Residual Stresses

Dr. Kelly Carney, Dr. Omar Hatamleh – NASA Glenn Research Center and Johnson Spaceflight Center

An analytical framework for predicting the residual stresses which result from the laser peening of a friction stir welded sample, using the finite element software LS-DYNA®, is presented, using a 2195 Aluminum alloy as an example. The pressures resulting from the laser peening are directly applied in an explicit transient analysis as forces. At the completion of the transient analysis, an implicit springback analysis is performed to determine the final residual stresses. This cycle is repeated for the appropriate number of peen applications, including the appropriate overlap of application areas. To validate the analytical framework, a comparison of residual stresses between analysis and a test specimen is made using laser peened base material which was not friction stir welded. Friction stir welding causes residual stresses and material property variations which increase the difficulty of modeling beyond the already complex modeling of the laser peening. In the analysis, the varying material properties regions are somewhat simplified and defined as discrete, separate materials. The residual stresses resulting from the welding are introduced directly as initial conditions in the peening transient analysis and so are combined within the analysis with the residual stresses from the peening. An additional challenge in the modeling of laser peening is the uncertainty in the yield strength of metals at the very high strain rates (>5000 1/sec) which result from the very short loading pulse duration. The strain rate sensitivity of the example metal, Aluminum 2195, is low at strain rates of less than 5000 1/sec, but its behavior higher than this rate is unknown. The effect of this uncertainty in the very high rate behavior is studied parametrically.

Modeling the Low Velocity Impact on Thick-Section Composite Cylinder

Sang-Guk Kang, Bazle A. Gama, Shridhar Yarlagadda, John W. Gillespie Jr. – University of Delaware, Thorsten Schütz, Stephan Fell – Adam Opel GmbH

Composite materials frequently have been applied to axi-symmetric filament-wound cylinder structures due to their specific stiffness and strength properties. When these structures are subjected to low-velocity impact (LVI), there exists a possibility of significant material damage which can drastically reduce the structural performance. The main objective of this paper is to predict the low velocity impact damage in thick composite cylinders using MAT162 progressive damage model implemented in LS-DYNA®. In this paper, damage prediction of a thick composite cylinder under low-velocity impact using uni-directional (UD) composite model of MAT162 is presented. A finite element model (FEM) of a thick composite cylinder with appropriate boundary conditions is developed to predict impact damages under different impact energies of a cylindrical steel impactor. Dynamic deformation, damage progression, and energy dissipation of the composite cylinder under LVI loading as a function of impact energy are presented

Modeling Wire Rope Used in Cable Barrier Systems

Cody S. Stolle, John D. Reid – University of Nebraska-Lincoln

An improved LS-DYNA® model of 19-mm diameter 3×7 wire rope commonly used in roadside cable guardrail installations has been developed. A Belytschko-Schwer beam element was selected along with material *MAT_MOMENT_CURVATURE_BEAM. Based on physical testing, total axial load vs. true strain and bending moment vs. curvature were generated for use in the model. Since wire rope displays internal damping due to friction of strands and wires, damping was incorporated into the model using the LS-DYNA command *DAMPING_FREQUENCY_RANGE to damp low-frequency bending oscillations. The proposed model was implemented to simulate a dynamic bending test; results compared favorably.

Module Development of Multiphase and Chemically Reacting Flow in LS-DYNA® Compressible Flow Solver

Kyoung-Su Im, Zeng-Chan Zhang, Grant Cook, Jr. – Livermore Software Technology Corp.

We reported a significant progress of the simulation module developments such as the cavitation, supersonic heterogeneous combustion, and gaseous detonations for the compressible flow solver. The homogeneous equilibrium model (HEM) based on the acoustic speed of the mixture of liquid and vapor was implemented for automotive diesel injectors, where the cavitation effects should correctly predict for the nozzle design. The heterogeneous combustion based on an Eulerian-Lagrangian model was developed for thermobaric explosive (TBX) applications in which a stochastic particle technique in conjunction with a probability density function (PDF) is adopted. In modeling of gaseous detonation, we implemented various combustion modules depending on the reaction model: one-step reaction (ZND model), reduced reaction of intrinsic low-dimensional manifolds (ILDM), and detailed chemistry model. Application results validated with experimental data are demonstrated with detailed discussion.

Multi-Disciplinary Optimization of a Sedan Using Size and Shape Parameterization

Nitin Sharma, Suthan, Jim Colins, Basant Sharma – Detroit Engineered Products Inc., Troy, MI

In vehicle development activity there are different disciplines with their own set of requirements that need to satisfied in order to get a successful product. Traditionally, the simulations were performed for different disciplines but at the time of optimization, Single Discipline Optimization (SDO) was usually performed and later confirmatory runs were done for the other disciplines. This process resulted in a time consuming loop of running several iterations with different disciplines and engaged people from these disciplines to make the optimized design meet the performance targets. Quite often these approaches led to tradeoffs made for design requirements or significant deviations from the optimized design obtained by running SDO. Multidisciplinary Optimization (MDO) addresses this shortcoming and takes into account different disciplines for optimization, thus reducing the need to iteratively evolve the design for different disciplines. Though this process has its benefits but those benefits are overridden with the setup time required for MDO. The major proportion of the setup time is consumed in defining shape variables on full vehicle FE model that has all types of connections as the process needs to be repeated for different disciplines. As a result an alternate methodology is sometimes pursued to create concept models from the full vehicle FE models thereby reducing the complexities of a full vehicle FE model. This approach not introduces approximation in the entire process by idealizing the detailed FE model but also requires this definition of shape variables separately for each discipline. In this paper, the MDO was performed on a full vehicle by considering Crash and NVH load cases. These two disciplines were considered to provide a process and to demonstrate its benefits. LS-DYNA® was used for crash simulations and Nastran was the solver used for NVH load cases. This process of MDO has been successfully applied to different vehicle programs including disciplines like durability, vehicle dynamics, occupant simulations, CFD etc. Due to IPR restrictions, the program specific work is not shared in this paper. The present process demonstrated on a sedan with different types of design variables defined for Crash and NVH load cases. The MDO is performed with the objective to reduce mass of the vehicle without any significant performance degradation. The approach presented here uses advance features of DEP’s Meshworks and provides the processes through which MDO could be carried out without sacrificing the complexity of the full vehicle FE model. It expedites the entire process by offering faster turnaround time.

New Developments of Frequency Domain Acoustic Methods in LS-DYNA

Yun Huang – Livermore Software Technology Corporation, Mhamed Souli – University of Lille, Rongfeng Liu – JSOL Corporation

This paper presents the new developments of finite element methods and boundary element methods for solving vibro-acoustic problems in LS-DYNA. The formulation for a frequency domain finite element method based on Helmholtz equation is described and the solution for an example of a simplified compartment model is presented. For boundary element method, the theory basis is reviewed. A benchmark example of a plate is solved by boundary element method, Kirchhoff method and Rayleigh method and the results are compared. A dual boundary element method based on Burton-Miller formulation is developed for solving exterior acoustic problems which were bothered by the irregular frequency difficulty. Application of the boundary element method for performing panel contribution analysis is discussed. These acoustic finite element and boundary element methods have important application in automotive, naval and civil industries, and many other industries where noise control is a concern.

New Features in LS-DYNA HYBRID Version

Nick Meng – Intel Corporation, Jason Wang, Satish Pathy – Livermore Software Technology Corporation

Numerical noise arising from different MPP core counts compels users to fix the number of cores used by LS- DYNA® MPP e.g. during a vehicle development program. This fixed core count limits job turn-around time and flexibility in managing computing resources. In addition, using a large number of cores for calculations diminishes scalability with pure MPP. LS-DYNA® HYBRID addresses these issues through the use of both MPI + OpenMP technology. LS-DYNA HYBRID is able to produce consistent numerical results when changing the number of OpenMP threads thereby reducing job turnaround time. In addition, LS-DYNA HYBRID can greatly reduce the number of processors involved in message passing and achieve much better scalability over large number of cores. Furthermore, for the implicit applications LS-DYNA HYBRID not only reduces the memory requirement per node but also decreases IO activity. Currently, LSTC and Intel® teams are working together with a customer to evaluate LS-DYNA HYBRID code using a custom QA (Quality Assurance) suite. The consistency and performance will be discussed in this paper.

Numerical Prediction of the Dynamic Response of Prestressed Concrete Box Girder Bridges Under Blast Loads

Ahmed Ibrahim, Hani Salim – University of Missouri

Significant research has been performed on the response and retrofit of buildings under blast loads. Limited research exists on the response prediction and protection of bridges under near-field blast loads. This research focuses on the evaluation and assessment of box girder bridges under blast loads. The objective of this research is to develop a numerical model to predict the damage level in a concrete deck under blast loading and the corresponding dynamic response of the damaged bridge system. The damage level will be function of spalling/cratering the bridge will suffer under the near field detonations. The numerical analysis conducted using the explicit dynamic software LS-DYNA®, which has the abilities to model the blast load propagation towards bridge structures and to its response to these types of impulsive loads. The bridge has a simply supported span of 100 ft (30.48 m) and was designed according to the LRFD manual under HL-93 truck load. Different charge weights were located at a height of 30 inches (0.762 m) between the main vertical webs at the mid-span. The study shows that LS-DYNA predicted the damage severity under blast loads, especially since the testing under these loads might not be feasible. The studied Key parameters were the weight of the charge, and concrete deck properties. The results of this study make the finite element modeling an attractive alternative for blast testing when it is not feasible like the case of bridges. Comparisons of the numerical results are still necessary for code verification before this study can be expanded for additional parametric studies and design recommendations

Numerical Simulation and Experimental Study of Electromagnetic Forming

Jianhui Shang, Larry Wilkerson, Steve Hatkevich – American Trim LLC, Pierre L’Eplattenier – Livermore Software Technology Corporation

Compared to traditional sheet metal forming, electromagnetic forming (EMF) has several advantages, such as increased formability, cost savings and improved flexibility. There are many EMF applications in sheet meal forming, especially for aluminum alloys, because aluminum alloys have relatively low formability and high conductivity when compared to steel. The EMF process uses magnetic field generated by a conductive actuator upon large capacitor discharge to accelerate workpiece to high velocity. It is a complex coupled mechanical-thermal- electromagnetic phenomenon, which makes it difficult to numerically simulate. However, to save time and cost, numerical simulation is needed to accurately predict results of EMF. The Electromagnetism (EM) module of LS-DYNA® has been developed by LSTC, which can be used for numerical simulation of EMF. American Trim has applied this module to assist in its EMF designs. In this paper, to access the capability of EM module, the numerical and experimental results of sheet metal formed with EMF were compared. The experiment was to apply EMF for straight-edge flanging of Al 6061-T6 sheet. Then this flanging process was modeled using both SMP and MPP version of LS-DYNA EM module. The comparison between the final shapes of flanged samples and the numerical simulation showed the good correlation between experimental and numerical results, which indicates the good predictive ability of the LS-DYNA EM module for EMF.

On the Prony Relaxation Function

William W. Feng, John O. Hallquist – Livermore Software Technology Corp.

For solving viscoelastic problems, the constitutive equations involve convolution integrals with relaxation functions. The relaxation function, G (t ) , is often written in Prony series…

Optimization Techniques in Conjunction with Complex ATD FE Models Using LS-DYNA

John Cooper, Dr. Hyunsok Pang, Matthew McCann, Dr. Ron Averill – Denton ATD, Inc and Red Cedar Technologies, Inc

This paper discusses the optimization methods used by Denton to create FE ATD models. Anthropomorphic Test Devices (ATDs also known as Dummies) are manufactured with a variety of hyperelastic and viscoelastic materials. The production processes used to manufacture ATD’s result in variations between dummies that can have a significant influence on dummy performance. In addition the load cases present during testing with ATDs are very complex and of short time duration. A typical frontal crash test may last 100ms but the load cycle on an ATD body region may last only 10ms. The end result is a complex series of issues that can be very difficult to solve in an FE model, using conventional techniques. The number of potential variables (sample list) associated with a specific performance metric (time history, acceleration, etc) can be very large. The settings for a given variable and the effect of that variable setting are difficult to determine given the complexity and short duration of the simulated event. In particular, the use of the hybrid adaptive SHERPA algorithm in the HEEDS software in conjunction with LS-DYNA for determining parameter values is discussed.

Overview of LSTC’s LS-DYNA Anthropomorphic Models

Christoph Maurath, Sarba Guha, Dilip Bhalsod, Mike Burger, Jacob Krebs, Suri Bala – LSTC, Sebastian Stahlschmidt, Reuben D’Souza – DYNAmore GmbH, Pradeep Mohan, Dhafer Marzougui – The George Washington University

The paper gives an overview of LSTC’s LS-DYNA crash test dummy model development effort. The model development process is outlined. Details of all released models are presented. The development status of models currently under development is addressed. Outlook to future models is given.

Predicting the Dynamic Crushing Response of a Composite Honeycomb Energy Absorber Using Solid-Element-Based Models in LS-DYNA

Karen E. Jackson – NASA Langley Research Center

This paper describes an analytical study that was performed as part of the development of an externally deployable energy absorber (DEA) concept. The concept consists of a composite honeycomb structure that can be stowed until needed to provide energy attenuation during a crash event, much like an external airbag system. One goal of the DEA development project was to generate a robust and reliable Finite Element Model (FEM) of the DEA that could be used to accurately predict its crush response under dynamic loading. The results of dynamic crush tests of 50-, 104-, and 68-cell DEA components are presented, and compared with simulation results from a solid-element FEM. Simulations of the FEM were performed in LS-DYNA®* to compare the capabilities of three different material models: MAT 63 (crushable foam), MAT 26 (honeycomb), and MAT 126 (modified honeycomb). These material models are evaluated to determine if they can be used to accurately predict both the uniform crushing and final compaction phases of the DEA for normal and off-axis loading conditions.

Prediction of Springback in CNC Tube Bending Process Based on Forming Parameters

Levent Sözen, Mehmet A. Guler, Recep M. Görgülüarslan, Engin M. Kaplan – University of Economics and Technology

CNC tube bending machines are commonly used in several industries such as automotive, aerospace and shipping. Especially in automotive industry, usage of tube formed geometries is common because they provide weight reduction without loss of strength. Obtaining desired dimensions and geometries is a necessity for design engineers to achieve high quality end-products. One of the easiest ways of having high quality tube formed end- products without the need of welding operations is using CNC tube bending techniques. The most common problems encountered during tube bending operations are thickness reduction, ovalisation, wrinkling and springback. Especially; springback which is defined as the deviation from the predefined bend angle after the bending operation performed is an undesirable condition that causes some difficulties in the assembly process. It depends on various geometrical parameters such as thickness of the tube, bend angle and effect of mandrel type used. Occurrence of springback is also dependent on forming parameters such as friction coefficient between dies and tube, internal pressure that is applied to the tube and axial loading. In the design stage, determination of springback and various parameters affecting springback behavior by experimental methods is quite cumbersome and costly. Therefore, prediction of springback by virtual methods such as finite element method (FEM) would shorten the time and reduces the cost of the pre-determination of springback.

Process Modeling of Freeform Incremental Forming Using LS-DYNA

Feng Ren, Zhen Cui, Z. Cedric Xia – Ford Motor Company, Todd Slavik, Li Zhang and Xinhai Zhu – Livermore Software Technology Corporation

Incremental Sheet Forming (ISF) is a manufacturing process for sheet metal prototyping where the blank is incrementally deformed into a desired shape by one or more stylus tools traveling along a prescribed path. Conventional ISF can be categorized into two types, Single-Point Incremental Forming (SPIF) where the sheet metal is formed from one side by a single stylus tool; and Double-Point Incremental Forming (DPIF) where a die positioned underneath a stylus tool pushes the sheet metal to wrap around the die. More recently a Freeform Incremental Forming (FIF) is developed at Ford Motor Company where two stylus tools synchronized in motion and deform the sheet metal from opposite sides as they are traveling to form a product shape. The new technology provides significant advantages for sheet metal fabrication process in terms of cost and flexibility because forming dies are completely eliminated and complex geometries can be formed. However the uniqueness of the process also brings significant challenges to its process design. This paper presents new capabilities developed in LS-DYNA for simulating Freeform Incremental Forming (FIF). The rigid stylus tools can move arbitrarily in both translational and rotational Degrees-of-Freedom (DOF). Challenges for numerical simulations and their modeling techniques are addressed in the paper. Numerical and experimental examples of Freeform Incremental forming processes are presented. It is demonstrated that the simulation results correlates very well with laboratory measurements.

Recent Developments in JSTAMP/NV for the Best Stamping Simulation Environment

Yuji Kato, Yasuyoshi Umezu, Yuko Watanabe – JSOL Corporation

In recent years, expectations for stamping simulation systems have increased in stamping die design process, as the needs for lightweight products and short production lead time have grown. Aiming at the best stamping simulation environment, JSOL Corporation has been developing JSTAMP/NV since 1996. One of the most competitive advantages of JSTAMP/NV is accurate prediction of deformation and formability by explicit and implicit solutions in LS-DYNA®. JSTAMP/NV also incorporates the implicit solver JOH/NIKE and the one-step inverse solver HYSTAMP developed by JSOL Corporation. This integrated system has been enjoying a good reputation in stamping die industry, especially Japanese automotive, appliance, and electronics manufactures and their suppliers. The recent needs towards stamping simulation software can be classified as: accurate results and their evaluation, short computation times, easy-to-use features for iterative process improvement, and support for modern stamping technologies. JSTAMP/NV continues to evolve to meet such requirements. In this paper, we present the recent developments in JSTAMP/NV, including ironing analysis support using solid elements, Yoshida-Uemori model material database, advanced trimmed mesh, enhanced springback compensation, easy-to-start reanalysis feature, free 3D viewer for collaboration, and hot stamping analysis capability.

Recent Improvements to Release III of the K&C Concrete Model

Joseph M. Magallanes, Youcai Wu, John E. Crawford – Karagozian & Case, L. Javier Malvar – Naval Facilities Engineering Service Center

Recent improvements are made to Release III of the Karagozian & Case (K&C) concrete model. This three- invariant plasticity and damage-based constitutive model is widely used to model a number of materials, including normal and lightweight concrete, concrete masonry, and brick masonry, to compute the effects of quasi-static, blast, and impact loads on structures. This most recent version of the model, made available starting with LS-DYNA® v971 as *MAT_CONCRETE_DAMAGE_REL3, incorporates a number of improvements to the original model that are described in this paper. The model now exhibits: (a) an automatic input capability for generating the data for generic concrete materials and (b) methods to reduce mesh-dependencies due to strain-softening. A simple method is implemented to regularize the fracture energy by internally scaling the damage function for the generic concrete model parameters. For user-defined material parameters, a method is developed that can preserve fracture energy using the results of either single-element or multi-element simulations. Finally, concrete loading rate effects are discussed and guidance is provided on properly modeling such effects with the model.

Response of the Enhanced Polar Outflow Probe (e-POP) Instrument Under Shock Loading

M. Nejad Ensan, D.G. Zimcik – National Research Council Canada

Spacecraft components encounter mechanical shock from a variety of sources. Components must withstand a series of flight shock pulses, and must be designed and tested accordingly to ensure reliability. This paper presents simulation of the response of the Enhanced Polar Outflow Probe (e-POP) instrument to the shock loading, during payload separation, using LS-DYNA® nonlinear finite element analysis software. Details of the model and simulation approach and the results obtained from that analysis are included in this paper. The mission science objective of the e-POP is to study plasma and atmospheric outflows in the polar region and the wave generation, particle interaction, and propagation associated with these outflows. The e-POP Instrument payload is a part of the “CASade, Smallsat and IOnospheric Polar Explorer” (CASSIOPE) mission. The CASSIOPE mission is a joint mission for the development and demonstration of key CASCADE technologies for future global bulk data delivery system, the development and demonstration of a generic SmallSAT Bus for future Canadian Space Agency (CSA) space missions.

Safety Assessment and Multi-Objective Optimization of a Paratransit Bus Structure

Cezary Bojanowski – Argonne National Laboratory, Ronald F. Kulak – RFK Engineering Mechanics Consultants

Paratransit buses are used in the U.S. as a complementary service for regularly scheduled routes and are usually designed to transport disabled passengers in their wheelchairs. Paratransit buses consist of custom passenger compartments mounted onto separate cutaway chassis–usually built by reputable manufacturer like Ford or GM– by a secondary manufacturer called a “body builder”. The lack of dedicated national crashworthiness standards, along with different construction methods used by paratransit fleet manufacturers, can result in a wide variance of passenger compartment structural strength. To ensure adequate crashworthiness performance, in August 2007 the Florida Department of Transportation (FDOT) introduced a standard stipulating that newly acquired buses must be tested for rollover and side impact conditions. The rollover test is performed using a tilt table test according to UN-ECE Regulation 66. The side impact test involves the impact of a bus by a common SUV or pickup truck. In the current study, a detailed FE model of a paratransit bus was used to perform LS-DYNA® explicit simulations of both rollover and side impact testing procedures per FDOT standard. LSTC IIHS solid movable barrier was adapted for the side impact test. Based on the results, the safety level of the bus was assessed. Subsequently, the response of the bus structure in the two impact scenarios together with the total mass were used as three separate objectives in a trade-off optimization study within LS-OPT®. The Pareto solutions were identified and presented using the newly implemented Hyper-Radial Visualization method in LS-OPT. The simulation results show that the original bus design would pass the FDOT testing procedure. However, appropriate redistribution of the mass can noticeably increase its strength.

Side Impact Occupant Modeling Practices in Comparison to Test Results

Skye Malcolm, Brian O’Hara, Craig Markusic, Bryant Whitcomb – Honda R&D Americas, Inc., Ram R. Songade – Altair Engineering, Inc.

A methodology to obtain and estimate the second row dummy response during the FMVSS 214 Barrier Side Impact test is described. Because of the limited amount of space between the occupant and the car structure, it is challenging to manage and predict the energy distribution in the FMVSS 214 crash mode. Increasing use of Finite Element models provides an edge in product development and its use is increasing as development time is reducing. For increased correlation with the test and more realistic dummy response, several factors are important, including the effect of restraint systems and representation of interacting components. This paper describes a methodology by which the second row occupant injury can be well-correlated to the test and used to help enhance occupant protection during vehicle development. A commercially available SID-IIs dummy and a Moving Deformable Barrier from LSTC are used in this study.

Simulation of a Thin Walled Aluminum Tube Subjected to Base Acceleration Using LS-DYNA’s Vibro-Acoustic Solver

Ofir Shor, Yoav Lev -Rafael, Yun Huang – LSTC

A shaker table test, where a simple thin walled aluminum tube was base accelerated at two geometrical locations, was simulated using the vibro-acoustic solver of LS-DYNA. It was shown that the method of modeling the fixture of the tube to the shaker table’s moving plate had a great impact on the simulation result. Three modeling methods of the fixture were tested, and acceleration PSD results at various points along the tube were compared to test data. A simple, numerically low-cost method, of modeling the fixture was found which gave very good agreements with the experimental data.

Simulation of Granular Ceramic Armor Under Impact from Bullets

James G. McLean, Seth Frutiger, Robert Dabek, Jeremy Reeves – State University of New York at Geneseo

Ballistic impact is studied for a novel form of armor, granular ceramic armor. Ceramic granules, in the millimeter size range, are closely packed and bonded together using a relatively soft polymer. This composite layer rests on a rigid backing. In field tests such panels have already shown the capability to stop armor piercing rifle rounds. The goal of the study is to determine the detailed mechanisms of energy and momentum dissipation. Because of the granular structure, the armor performance depends on the exact impact position. We are particularly interested in determining the weakest points for further design improvements. Mapping of exit velocities indicates that some of the stronger and weaker points are at surprising impact positions due to grain tumbling.

Solid Elements with Rotational Degree of Freedom for Grand Rotation Problems in LS-DYNA

Hailong Teng – Livermore Software Technology Corporation

The goal of this paper is to further enhance the solid elements with rotational degree of freedom (DOF). Three- dimensional finite elements with rotational degree of freedom have been proposed elsewhere, however, these elements are restricted to linear analysis. In this paper, by improving the mid-side node velocity update algorithm, we enhance the elements performance. Numerical results are presented, showing that the enhanced elements are capable of dealing with grand rotation problem. The enhanced formulation has been implemented into LS-DYNA® for solid element 3 and solid element 4.

Stone Skipping Simulation by ALE and SPH

Mitsuhiro Makino – Dynapower Corporation

Stone skipping is the play at sea shore and river. The flat stone, which is thrown, skips on the surface of water. This phenomena is simulated by ALE and SPH capability of LS-DYNA®. The dependency of the parameters such as the angle between stone and water, incident angle of stone will discuss.

Structure-Fluid Interaction Analysis of an Existing Water Tank

Mohammad Ghorbanie, Glen Norlander – AMEC Americas

An analytical study was completed investigating the cause and consequences of significant vibrations resulting from the operation of a hot water storage tank. Deformations and strain readings of the tank wall were measured during the operation and used to calibrate and validate results from the analytical model. The steel storage tank is supported on a concrete foundation. The diameter of the tank is 18 meters and the height is 28 meters. The shell wall thickness varies in steps as plate segments reduce in thickness from 16.2mm at the bottom to 6.7 mm near tank mid height and above. A 64 inch diameter pipe at the top of the tank supplies the inflow water. Three 42 inch and two 36 inch diameter discharge nozzles are located near the bottom of the tank. The tank wall has been observed to be “breathing” at low water levels. These vibrations reduce as the tank water level increases. In order to evaluate the deformations and stress level of the tank, optical measurement of the deformations and strain gauge readings for inflow rates of 4500, 6000 and 8500 m3/hr were performed. The results were then used within a calculation to check for fatigue failure. To study the dynamic behavior of the hot water tank, a set of FE (Finite Element)-CFD (Computational Fluid Dynamics) models were prepared at flow rates of 4500 to 12500 m3/hr. Standard shell elements were used to model the tank shell and both content and inflow water were modeled using the SPH (Smooth Particles Hydraulics) elements available in LS-DYNA®. Interaction between the structure and fluid was defined using contact scenarios. These models were calibrated using the results of strain gauge readings and optical measurements. The size of the elements, geometry and physical properties were decided after numerous test analyses results were adjusted for consideration of certain variables. The final model represented the most critical arrangement considered. Results of the analyses were within an acceptable range of the readings from the strain gauges. Scale factors were used to calibrate the FE results for better compliance. Field measurements and results from the analysis demonstrate stress levels and displacement increase with higher inflow rates.

Study of Thin-Walled Box Beams Crushing Behavior Using LS-DYNA

Yucheng Liu – University of Louisiana

This paper investigates the dynamic crushing behaviors of steel beams with box cross sections. Systematic parametric studies were conducted in order to reveal the effect of material properties, including strain hardening ratio and strain rate effect, length of the beam, and initial impact velocity on the crushing behaviors of the steel beams. A number of finite element models were constructed with various sets of parameters and used for crashworthiness analyses. Maximum crushing force, mean force, and specific energy absorption (SEA) were recorded after analyses and compared to reflect the influences of parameters. An explicit finite element solver, LS-DYNA®, was used in this study for modeling and analyses.

The Performance of Car Crash Simulation by LS-DYNA Hybrid Parallel Version on Fujitsu FX1

Kenshiro Kondo – Fujitsu Limited, Mitsuhiro Makino – DYNAPOWER Corporation

The number of elements of car simulation for crash analysis has increased rapidly over recent years in order to achieve better accuracy. Several MPP versions of LS-DYNA using variations of MPI have been widely applied to car crash simulation for better job turnaround. The modern computing hardware has been exploring multi-core CPU technology since the performance of single-core can not meet the current and future demands. The Hybrid Parallelization version of LS-DYNA, taking the advantage of multi-core computing platforms, provides an efficient tool for large- model car crash simulation. This hybrid version combines threads parallelization using OpenMP across multiple cores within a node as well as process parallelization using MPI between nodes to achieve maximum parallelization of the analysis. In this paper, we revealed performance bottle neck of MPP version for highly parallelization first; then we showed performance and examined accuracy of solution of LS-DYNA Hybrid version. We tested both 2-million and 10-million elements Caravan crash models on both LS-DYNA MPP and Hybrid versions. The superior performance of Hybrid version demonstrated the feasibility of car crash simulation using massively parallel processors.

The Potential Impact of GPUs on LS-DYNA Implicit

Roger Grimes, Robert Lucas, and Gene Wagenbreth – Livermore Software Technology Corp.

This talk will report the on-going efforts of LSTC to study the impact of GPUs on LS-DYNA. GPUs offer very high performance computational power at the cost of importing and exporting of data between the host computer and the GPU. The GPU has restricted memory, requires programming in a special language, and suffers performance reduction for double precision arithmetic. Still GPUs appear to offer a potential speed-up of a factor of 2 to 3. Initially our study is focusing on the impact on Implicit Mechanics. The most important computational kernel for Implicit Mechanics is in the direct solution of the sparse systems of linear equations. We will focus on how one can use GPUs for this computational kernel and the probable performance improvement.

The Recent Progress and Potential Applications of Corpuscular Method in LS-DYNA

Hailong Teng, Jason Wang, Dilip Bhalsod – Livermore Software Technology Corporation

The corpuscular method is a coarse-grained muti-scale method developed for gas dynamics simulation. It is based on the kinetic molecular theory, where molecules are viewed as rigid particles obeying Newton’s laws of mechanics. Each particle in the corpuscular method represents a group of gas molecules. The only particle-particle and particle–fabric interactions are perfectly elastic collisions. The corpuscular method has been applied to airbag deployment simulation. This paper describes the recent progress of corpuscular method in LS-DYNA®; its application to airbag deployment simulation and other gas related process.

Usage of LS-DYNA in the Development of Professional Hammer Drills

A. Syma – Black & Decker GmbH, M. Hörmann – CADFEM GmbH

The development of modern electric power tools for professional use requires special attention. Characteristic aspects such as efficiency and user comfort along with robustness and durability are always of importance to the manufacturer. For the fulfillment of these attributes computer-aided simulation combined with the finite element software LS-DYNA® is a central point during the development process at Black & Decker GmbH, i.e. from the predevelopment phase up to testing near series prototypes. The area of application of LS-DYNA® is not limited to classical drop test cases for devices (see Figure 1), but goes far beyond that. DeWALT uses LS-DYNA® for their hammer drill development in order to account for different hammer sub-assemblies and various structural mechanical concerns. Particularly during the hammer work interpretation regarding unwanted idle impacts, LS-DYNA® can simulate harmful shock waves in the drilling spindle and tool holder for the equipment. Further LS-DYNA® allows the computational illustration of the entire hammer drive train (see Fig. 2) as well as the simulation of comprehensive misuse. Based on case examples from the daily employment of LS-DYNA® in development practice the various types of applications at Black & Decker GmbH, DeWALT are shown.

Use of LS-DYNA to Assess the Energy Absorption Performance of a Shell-Based KevlarTM/Epoxy Composite Honeycomb

Michael Polanco – NASA Langley Research Center

The forward and vertical impact stability of a composite honeycomb Deployable Energy Absorber (DEA) was evaluated during a full-scale crash test of an MD-500 helicopter at NASA Langley’s Landing and Impact Research Facility. The lower skin of the helicopter was retrofitted with DEA components to protect the airframe subfloor upon impact and to mitigate loads transmitted to Anthropomorphic Test Device (ATD) occupants. To facilitate the design of the DEA for this test, an analytical study was conducted using LS-DYNA®* to evaluate the performance of a shell-based DEA incorporating different angular cell orientations as well as simultaneous vertical and forward impact conditions. By conducting this study, guidance was provided in obtaining an optimum design for the DEA that would dissipate the kinetic energy of the airframe while maintaining forward and vertical impact stability.

Using LS-DYNA to Computationally Assess the V0-V100 Impact Response of Flexible Fabrics Through Probabilistic Methods

Gaurav Nilakantan, Michael Keefe, John W. Gillespie Jr. – University of Delaware, Eric D. Wetzel, Travis A. Bogetti, Rob Adkinson – US Army Research Laboratory

The probabilistic nature of the impact performance of flexible woven fabrics arises from a number of sources. The statistical nature of yarn tensile strengths on impact response is modeled in this study. Currently the probability of penetration of a fabric at a given velocity (Vx is the impact velocity having a probability of penetration of x ranging from 0 to 100%) is determined experimentally, by shooting fabric panels over a range of velocities and fitting the response data to a likely probabilistic function. This approach requires a large number of experimental test shots associated with significant cost, labor, and time in order to generate statistically meaningful results. In this study, we use the finite element (FE) analysis to study the impact response of flexible woven fabrics. A probabilistic framework is developed, that maps experimentally obtained yarn tensile strength distributions directly onto the FE model comprised of a yarn level architecture. Multiple impact simulations are run using a Monte Carlo approach. Through this novel probabilistic approach, the V0-V100 response of flexible woven fabrics can be predicted numerically. Further, a direct relationship between the statistical nature of yarn material properties and the probabilistic impact response of fabrics is established. This correlation allows an investigation into the effects of weaving and scouring degradations on the impact performance.

Validation of Material Models for the Numerical Simulation of Aluminum Foams

Marco Perillo, Vito Primavera – EnginSoft SpA, A. Carofalo, M. De Giorgi, R. Nobile – University of Salento

In the last years a lot of studies dealt with the material modeling of metallic foams, especially for the Aluminum ones. All these activities were performed especially for automotive field applications because the high energy- absorbing property of such foams fits very well the requirement to carry impacting loads efficiently. In spite of this, the industrial applications are not yet so widespread both for manufacturing costs and for a lack of knowledge regarding a whole mechanical characterization. The anisotropic properties of the foams induced mainly by the manufacturing processes, like the continuous casting procedure [1,2] is the reason due until now it has not been possible to assess in a well-known way the foams mechanical performances. In function of the wide spectrum of loading configurations, foaming direction, open and closed cells typology, cells morphology, density, thickness, etc., the output data regarding the mechanical tests are largely scattered (e.g. the stress/strain curves change according to the direction along the experimental test is performed), so a numerical model designed to reproduce accurately the foam behavior needs to take into account the parameters affecting the foam response…

Variable Screening Using Global Sensitivity Analysis

Tushar Goel, Christoph Maurath – Livermore Software Technology Corporation

The cost of optimization increases with the dimensionality of the problem irrespective of using metamodels or direct methods. It is recommended to explore the opportunities to reduce the number of variables. One method to reduce the dimensionality is to fix the variables that do not influence the response significantly. ANOVA based on polynomial response surfaces is often used to identify the least important design variables. The global sensitivity analysis, proposed by Sobol, is another very useful technique to reduce the dimensionality. This method can be used with any surrogate model and is often used as a variable screening tool. While the dimensionality reduction based on a single response is widely used, this study presents an easy approach, facilitated by LS-OPT®, to reduce the number of design variables when a system comprising of multiple responses is considered. The benefits of reducing the problem dimensionality are demonstrated using a crashworthiness example.

Vehicle Structures Experimental Analyses

Moisey B. Shkolnikov

This paper is a summary of previous developments, publications and usage of special strain gages sets (referred to here as experimental finite elements, FEs) in experimental analyses of vehicle structures. The experimental FEs developments were based on Structural Mechanics, Math Statistic theories and experience of their applications in vehicle structures analyses and tests. The summary’s objective is to describe the LS-DYNA® optional participation in experimental analyses by using experimental FEs for confirmation of analytical simulation results. Currently LS- DYNA (and its pre and post processors) have enough capability to use experimental measurement results for analytical results confirmations. However not always LS-DYNA users are familiar with the details of strain gage technology, and experimental specialists are not always familiar with the details of LS-DYNA usage of measured strains. Experimental FEs in LS-DYNA would provide a bridge between those analytical and experimental technologies. LS-DYNA users would be able to generate experimental FEs based on a vehicle structure analytical FEs model simulations results and defining structure’s areas needed the simulation results experimental confirmations. That information and information specifying types of strain gages and rosettes and their locations on a vehicle structure under tests may be provided by the LS-DYNA users to experimental specialists. Based on that information the experimental specialists will conduct the structure tests and provide to the LS-DYNA users the required types and amount of strain gage measurements results.

WorldSID 50th vs. ES-2 A Comparison Based on Simulations

Sebastian Stahlschmidt, Alexander Gromer – DYNAmore GmbH, Matthias Walz – Daimler AG

For testing side impact performance of vehicles two recent male-sized dummies are available. Currently only the ES-2(re) is used in regulations and consumer test. It is expected that the WorldSID will be used for some load cases as substitute or in addition to the ES-2(re). Since only limited experience with the WorldSID is available, simulation is a ideal tool to face the upcoming challenge. The comparison employs detailed finite element dummy models of the ES-2(re) and WorldSID which have been developed in cooperation with the German Association for Automotive Research (FAT) and the Partnership for Dummy Technology and Biomechanics (PDB) during the last years. The paper compares the behavior of the dummy in selected body regions. It showcases in different load cases if the experiences gained with the ES-2(re) can be used to design a vehicle for tests with the WorldSID.

XFEM and EFG Cohesive Fracture Analysis for Brittle and Semi-Brittle Materials

Yong Guo, C.T. Wu – Livermore Software Technology Corporation

The finite element analysis of dynamic fracture in solids and structures is challenging due to the modeling of arbitrary crack growth in the continuum domain. The well-known mesh size and mesh orientation dependences add more difficulties into the analysis of this type of problems. In this presentation, we are going to introduce two numerical methods in modeling the dynamic fracture in brittle materials for solid and structures in LS-DYNA®. Both methods were developed by Belytschko and his group [1, 14] and were based on a strong discontinuity approach combined with cohesive forces for the crack initiation and propagation. In EFG method, a visibility method is utilized to define the cracks in the solids and a fast transformation method [18] is applied to handle the boundary conditions in the cracked media. The XFEM method is implemented to model the dynamic fracture in structures. The XFEM method can be viewed as a combination of level sets method and partition of unity method [15] in the description of cracks