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7th International LS-DYNA Conference
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3D Numerical Simulations of Penetration of Oil-Well Perforator into Concrete Targets
Qiankun Jin, Zheng Shigui, Gary Ding, Yianjun, Cui Binggui - Beijing Engineering Software Technology Co., Ltd.
The oil-well perforator and its interaction with concrete targets are simulated with fluid-structure coupling algorithm and the new mesh motion option of the multi-material ALE formulation of LS-DYNA[1] in Version 960. Comparison of the simulation results to the experimental test data has been conducted. The simulation results show good correlation with data in tests and indicate that LS-DYNA can be used as an engineering tool to help in the prediction of perforation depth.
Andreas Hirth - DaimlerChrysler, Paul Du Bois, Dr. Klaus Weimar - DYNAmore
Recently new materials were introduced to enhance different aspects of automotive safety while minimizing the weight added to the vehicle. Such foams are no longer isotropic but typically show a preferred strong direction due to their manufacturing process. Different stress/ strain curves are obtained from material testing in different directions. A new material model was added to the LS-DYNA code in order to allow a correct numerical simulation of such materials. Ease-of-use was a primary concern in the development of this user-subroutine: we required stress/ strain curves from material testing to be directly usable as input parameters for the numerical model without conversion. The user-subroutine is implemented as MAT_TRANSVERSELY_ANISOTROPIC_CRUSHABLE_FOAM, Mat law 142 in LS-DYNA Version 960-1106. In this paper we summarize the background of the material law and illustrate some applications in the field of interior head-impact. The obvious advantage of incorporating such detail in the simulation lies in the numerical assessment of impacts that are slightly offset with respect to the foam's primary strength direction.
Larsgunnar Nilsson, Anders Jernberg - Engineering Research Nordic AB
The vehicle to moose impact constitutes a serious traffic problem in the Nordic Countries. Thus, in addition to the conventional requirements on crashworthiness, a Swedish car is also supposed to protect the occupants in the case of a moose impact. The Swedish National Road and Transport Research Institute (VTI) has developed a moose crash test dummy, which has shown to have a similar impact behaviour on the vehicle as a real moose. The main components of the test dummy are 36 rubber plates, but there are also various steel parts holding the pieces together. Due to the height of the moose, the main body will hit a normal size passenger car in the A-pillar and front window region. The legs will hit more frontal parts of the vehicle and make the moose body rotate. In a typical moose impact the A-pillars and the frontal roof are severely deformed into the passenger compartment. A FE-element model of the moose crash test dummy has been developed for LS-DYNA. The FE-model closely replicates all components of the physical dummy. About 30.000 elements are used for the model, which has a critical time step of about 1.5 microsecond. The FE-model of the moose is complete and only the contact interfaces between the moose and the vehicle need to be defined. Simulations of passenger car to moose impacts have been conducted and the results are evaluated and compared to physical test data.
A Virtual Golf Robot for Golf Equipment Simulation
Tom Mase - Michigan State University
The equations of motion for a two-lever pendulum are developed using Lagrange's equation. An assumed kinematic golf swing is used to generate generalized forces to drive the golf robot. These moments are used to generate a golf robot swing using LS-DYNA. The LS-DYNA model is flexible enough so that the model can be used as a virtual laboratory.
Aircraft Engine Blade-Out Dynamics
Kelly S. Carney, Charles Lawrence, Dorothy V. Carney - NASA Glenn Research Center
A primary problem in the design of aircraft gas turbine engine internal and support structures is the accurate simulation of the fan blade-out event and the subsequent windmilling of the engine. Reliable simulations of the blade-out event are required to ensure structural integrity during flight as well as to guarantee successful blade-out certification testing. A model and procedure has been developed which successfully predicts the key physical behavior of a generic engine structural dynamics. The key procedures and modeling techniques for this application are given.
ALE and Fluid-Structure Interaction Capabilities in LS-DYNA
M'hamed Souli - Universite des Sciences et Technologie de Lille, Lars Olovsson, Ian Do - Livermore Software Technology Corporation
A new Eulerian-Lagrangian coupling algorithm and improved multi-material ALE-capabilities have made LS-DYNA an efficient tool for analyzing large deformation processes, such as bird strike events, forging operations and penetration problems. This paper contains four example problems that illustrate the current features of the code.
An Application of LS-DYNA for the New FMVSS 208 Front Impact Tests
Charlotte Jamte, Tim Keer, Richard Maloney, Joshua Weage - Arup
The automotive safety community is currently facing the challenge of new front impact legislation (FMVSS 208), to be introduced in the USA in 2004. Vehicles will be subjected to an increased number of and type of barrier tests. This paper describes a new technique, using LS-DYNA, to aid the vehicle development process. A virtual "sled" has been developed for analysis of the different FMVSS 208 impact scenarios. This sled model would typically be created and exercised early in the vehicle development process, before a full vehicle model can be created. The sled can incorporate the target structural response of the occupant compartment (translational and rotational accelerations; intrusion; yaw and pitch; steering column motion), the restraint systems (airbags and seat-belts) and the occupants (driver and passenger; different percentile dummies). This modular approach allows different barrier configurations (rigid; rigid angled; deformable offset), impact speeds and occupant sizes (Hybrid III 5th and 50th) to be modeled with simple changes to the input file. The benefits of this approach are the ability to obtain a preliminary assessment of vehicle compliance for a wide range of impact scenarios at a time when the vehicle package is still being determined.
Marlin Brueggert, Romil R. Tanov - Center for Advanced Product Evaluation, Division of IMMI
The behavior of loosely woven fabrics (LWF) differs significantly from other types of woven fabric materials, the major difference being the significant change that the angle between the weft and warp fibers undergoes as the fabric stretching forces change. These unique characteristics have made the LWF a very important part for the functionality of some recently developed occupant protection safety devices for the automotive and heavy machine and truck industry. To efficiently model and analyze the behavior of such devices within an occupant protection model, an accurate representation of the characteristics of the LWF is needed. However, none of the many available LS-DYNA material models seem to fit well with the unique kinematics of the LWF. Therefore, the aim of this work is to present the basics of a formulation for a material model for the analysis of LWF and its implementation as a user defined material in LS-DYNA. To assess the performance of the model, results from the simulation are presented. Although relatively simple, the developed model seems to represent very well the behavior of the LWF and the simplicity of the formulation attributes to the efficiency and stability of the user defined material subroutine.
An Optimization Procedure For Springback Compensation Using LS-OPT
Nielen Stander, Mike Burger, Xinhai Zhu, Bradley Maker - Livermore Software Technology Corporation
The purpose of this study is to develop a methodology for springback compensation in sheet metal stamping operations. An optimization method is employed to minimize the difference between the simulation results and the intended design. This procedure results in an optimized die shape. LS-DYNA, LS-OPT and TrueGrid are used to input original tool geometry, material, and process parameters, identify design variables, perform springback simulations, and output optimized tool geometry. It is found that springback trends are consistent with changes in the die shape, which provides an effective strategy for springback compensation. The standard NUMISHEET'96 S-Rail is used as a benchmark example in this study.
Keng C. Yap, G. Wije Wathugala, Timothy K. Hasselman - ACTA Inc.
It is becoming commonplace to use numerical simulations supported by limited experimentation for the characterization of physical phenomena. This trend, with its perceived potential for reducing costs, is the basis for the simulation-based procurement initiatives currently gaining momentum within the government and industry. Insuring the quantitative viability of a simulation-based procurement still requires some experimental data upon which the assessment of simulation accuracy can be based. In addition, it requires minimizing the differences between corresponding analytical and experimental results in physically meaningful ways, and characterizing the ability of the models to predict future events. The purpose of model validation and uncertainty quantification is to confirm the correctness and credibility of numerical simulations, so that the underlying models may be used with greater confidence to extrapolate limited test experience to a range of practical applications. In this paper, an advanced principal components-based computational procedure is demonstrated by validating the DYNA models used to achieve HFPB numerical simulations of physical processes important to assessing weapon- target interaction. Bayesian statistical parameter estimation is used to estimate material parameters that cannot be measured directly, such as strain rate enhancement and shear dilatency in reinforced concrete structures. This demonstration is performed using an updated MATLAB® Nonlinear Model Validation and Verification Toolbox. The work reported in this paper has resulted in improvements to the original Toolbox. A multi-level parameter estimation procedure is implemented to sequentially accumulate information from prior estimates in a Fisher information matrix for use in subsequent parameter estimates. The use of a generic uncertainty model in estimating the predictive accuracy of future DYNA simulations is enhanced through the use of a reduced set of principal component metrics and a basis augmentation technique.
Analyzing Elastomer Automotive Body Seals Using LS-DYNA
Linhuo Shi - TG North America Corporation
Several different elastomer automotive body seals (weatherstrips or weather seals) are analyzed using explicit solver of LS-DYNA. The results are compared with those obtained from non-linear finite element analysis (FEA) solvers widely used for elastomer analysis as well as the experimental results. It is found that properly modeled LS-DYNA can be a very good tool for elastomer body seal analysis, especially for the analysis with potential instabilities, such as snap-through, loss-of-contact, severe slip-stick, and complicated contact problems.
Jerry W. Wekezer - FAMU-FSU College of Engineering, Krzysztof Cichocki - Technical University of Koszalin
Errant vehicles may pose a serious threat to neighboring traffic of pedestrians, bicyclists, and even to their drivers in a densely populated urban environment. Accident reconstructions have indicated that street curbs do not offer any meaningful protection against errant vehicles, which can easily traverse street curbs even at small velocity and shallow angles. The paper presents research results of a study, in which computational mechanics was utilized to predict vehicle trajectories upon traversing standard Florida DOT street curbs. Computational analysis was performed using LS- DYNA computer code and two public domain, finite element models of motor vehicles: Ford Festiva and Ford Taurus. The suspension systems of the original vehicle models were evaluated and additional suspension components were identified and developed. The finite element models of the required suspension systems were developed using geometry from the actual suspension parts, captured using a digitizing arm. Due to complex geometry of these parts, the MSC-PATRAN preprocessor was used to create data for LS-DYNA code. Shock absorbers were modeled using discrete spring and damper elements. Connections for the modified suspension systems were carefully designed to assure proper range of motion for the suspension models. Inertia properties of the actual vehicles were collected using tilt-table tests and were used for LS-DYNA vehicle models. A standard FDOT street curb model was developed using rigid wall option in LS-DYNA. Initial, computational mechanics analyses suggest that vehicles tend to retain larger amount of their kinetic energy after traversing street curbs. It is therefore dangerous to anticipate that performance of street curbs would be comparable with that demonstrated by guardrails. In order to validate the assumed discrete numerical models and the results of LS-DYNA analyses, full-scale experimental tests have been performed at Texas Transportation Institute. Two types of vehicles have been tested: Ford Festiva and Ford Taurus, both for two values of approach angle: 15 and 90 degrees, with impact velocity of 45 mph. Experimental results including accelerations, displacements and overall vehicles behavior were registered by high-speed video cameras and have been compared with numerical results and computer animations. Verification results indicated a good correlation between computational analysis and full-scale test data. The study also indicated a strong importance of properly modeled suspension and tires on resulting vehicle trajectories. The major goal of the research was to study the behavior of various vehicles (from small Ford Festiva to pickup truck Chevrolet C2500), for different approach angles, velocities and curb profiles. Experiences gained in preliminary numerical analyses and experimental tests allow studying a matrix of critical cases without time- consuming and costly additional experimental testing.
Applications of LS-DYNA in Electronics Products
Hanks Hsu, Brian Hsiao - Flotrend Corporation
Portable electronic devices have become smaller and lighter but they are also easily damaged during accidentally drop situation. Therefore, new electronic products are usually needed to pass requirements of shock and drop test before actually delivering to customers. FEM simulation provides engineers a useful and powerful approach to identify the potential weakness of products before the prototype is even made. The report will introduce the applications of the Ls-dyna in a virtual lab which simulates the experiment conditions of shock and drop tests in computers. It also shows Ls-dyna can be a very effective tool for engineers to improve the performance of their design in the shock and drop test.
Benjamin A. Tutt, Anthony P. Taylor - Irvin Aerospace Inc.
Irvin Aerospace Inc., has used the LS-DYNA Explicit Finite Element Analysis (FEA) tool for over five years for the analysis of static and dynamic fabric problems. The References provide many examples of this previous work. Our first application was the analysis of airbag landings for several spacecraft programs, including Reusable Launch Vehicles (RLV's), various Unmanned Air Vehicles (UAV's), Military Airdrop Systems, and planetary exploration systems. These are all covered in the references. This paper presents some current results along the lines of the above, and other recent developments. These include an air beam supported structure, which was evaluated for both snow and wind loads, and a fabric blanket system that was somewhat optimized by a combination of FEA analysis and testing. While these applications appear rather bland, the air beam structure is designed to house military fighter and rotary aircraft and must withstand significant snow and wind loads. The blanket system is used to constrain a target-missile that performs a unique 'Air Launch' mission, involving extracting the target from a cargo aircraft and allowing it to stabilize prior to release and ignition.
Automotive Door Sealing System Analysis
Rosa Zhao, Frank Lee, Thomas Oetjens - General Motors Corp.
Door sealing system is one of the most important automotive quality issues. Problems with door seal system could cause water leakage, wind noise and hard to open or close, which impair customer's satisfaction of the vehicle. That is why the door seal problem is always among the Hardy Perennial Top 10 list in JD Power Tracking Study. The design rationality and manufacturing process are important aspects for the functionality and performance of a sealing system. However, the door sealing system involves many design variables and manufacturing variables. It is almost impossible to precisely confirm individual quantitative effects on functionalities of these variables. Therefore, computer based simulation of door sealing system is more practical since it can isolate the critical factors and it is cost effective and time efficient. LS-DYNA was used to simulate door seal system. The key structural component, the rubber seal, was modeled and simulated. Different types of elements, material models and contact algorithms from LS-DYNA element, material and contact libraries were tried and compared. Consequently, the best modeling and simulation technology was developed for the door sealing system analysis. The newly developed method showed the great potential of comprehensive studies of door sealing system. The analysis results provided some major parameters, such as seal deformation, contact pressure and energy transformation, which would influence the functionality and performance of the door sealing system. The analysis results have been compared with some available test data, and very good correlations were obtained. The analysis also evaluated the influence of manufacturing deviations. With the results obtained from this analysis, the relationship between the major parameters could be established and used as a tool to derive a better sealing system design at early stage. This analysis method could also be used to evaluate the influence of certain type of process error. Eventually, this analysis method will be developed into a tool that is capable of predicting water leakage, wind noise and hard to open/close problems caused by either product design or manufacturing process.
Chian-Fong Yen - Materials Sciences Corporation
A computational constitutive model has been developed to characterize the progressive failure be- haviors of composite laminates under high velocity ballistic impact conditions. The composite failure model has been implemented within LS-DYNA as a regular material subroutine. The inte- grated code was successfully utilized to predict the damage and ballistic behavior of composite laminates subjected to various ballistic impact conditions. The availability of this design tool will greatly facilitate the development of composite structures with enhanced ballistic survivability.
Characterization of Water Impact Splashdown Event of Space Shuttle Solid Rocket Booster Using LS-DYNA
Matthew E. Melis - NASA Glenn Research Center, Khanh Bui - Livermore Software Technology Corporation
The ALE capability in LS DYNA is used to predict splashdown loads on a proposed replace- ment/upgrade of the hydrazine tanks on the thrust vector control system housed within the aft skirt of a Space Shuttle Solid Rocket Booster. Two preliminary studies are preformed in working towards conducting a full comprehensive analysis: An analysis of the proposed tank impacting water without supporting structure, and an analysis of actual space capsule water drop tests conducted at NASA's Langley Research Center. Results from the preliminary studies provide confidence that useful predictions can be made by applying the ALE methodology to a detailed analysis of a 26-degree section of the skirt with proposed tank attached. Results for all three studies are presented and compared to limited experimental data. The challenges of using the LS DYNA ALE capability for this type of analysis are discussed.
Ala Tabiei, Ivelin Ivanov - University of Cincinnati
This work presents a computational material model of flexible woven fabric for finite element impact analysis and simulation. The model is implemented in the nonlinear dynamic explicit finite element code LSDYNA. The material model derivation utilizes the micro-mechanical approach and the homogenization technique usually used in composite material models. The model accounts for reorientation of the yarns and the fabric architecture. The behavior of the flexible fabric material is achieved by discounting the shear moduli of the material in free state, which allows the simulation of the trellis mechanism before packing the yarns. The material model is implemented into the LSDYNA code as a user defined material subroutine. The developed model and its implementation is validated using an experimental ballistic test on Kevlar woven fabric. The presented validation shows good agreement between the simulation utilizing the present material model and the experiment.
Continuous Surface Cap Model for Geomaterial Modeling: A New LS-DYNA Material Type
Leonard E Schwer - Schwer Engineering & Consulting Services, Yvonne D Murray - APTEK, Inc.
The Continuous Surface Cap Model is a new addition to the LS-DYNA geomaterial modeling library of constitutive models (Material Type 145). This new model should replace the use of the Geological Cap Model (Material Type 25) for most applications. The Continuous Surface Cap Model maintains all the functionality of the Geological Cap Model with the addition of the third stress invariant, strain rate effects, and damage modeling. The Continuous Surface Cap Model has also been reported to be about three times faster than the Geological Cap Model in a large scale application. This article briefly describes some of the model features and illustrates its application.
Correlation of the Federal Motor Vehicle Safety Standard 225 (FMVSS225) Requirement of an Automotive Seat System Using LS-DYNA
Frank Xu, Partha Chowdhury, Babushankar Sambamoorthy, Tuhin Halder - Lear Corporation
The National Highway Traffic Safety Administration (NHTSA) has issued a final rule for a new safety standard related to child seats and their anchorage systems in vehicles. FMVSS 225 – Child Restraint Anchorage Systems (CRAS) requires that motor vehicle manufacturers provide a new method for installing child restraints that are standardized and independent of the vehicle seat belt. The requirements for CRAS can ensure their proper location and strength for the effective securing of child-occupants in an automotive seat system. There are four pull tests for FMVSS 225 - forward pull with top tether, forward pull without top tether, lateral pull to the right, and lateral pull to the left. The tests are performed by applying a specified load to the child seat anchorage system using Static Force Application Devices (SFAD), mandated by NHTSA. The regulation requires that the displacement of the load application point on the SFAD, along the horizontal plane, should be less than 125 mm and there should not be any structural separation [1][2]. LSDYNA is widely used for the "quasi-static" simulation of the automotive seat systems and plays a key role in improving design and saving cost. Due to the dynamic effects in quasi-static simulations, correlating the displacement for FMVSS 225 using LSDYNA becomes a challenge. At Lear Corporation's test lab, physical tests were conducted on number of different seats and the results were correlated by simulating the tests in LSDYNA. Based on the knowledge and data collected over a period of 3 years, the authors have established a methodology to simulate FMVSS 225 and correlate accurately with the physical test.
Magdy Samaan - University of Windsor, Ahmed Elmarakbi - University of Toronto, Khaled Sennah - Ryerson University
The objective of this paper is to generate research information to enhance energy absorption characteristics in transportation infrastructures involved in vehicle crash accidents. A finite-element computer model, using the available LS-DYNA software, was developed to simulate crashes of a vehicle and a traffic light steel pole in frontal impact. The finite-element vehicle model was based on a 1991, 4-door, Ford Taurus. The steel pole was modeled using shell elements to capture the three-dimensional effect of the structure. Four configurations of steel pole supports were examined. The first support type was the typical steel base currently used over concrete foundation, with anchor bolts as specified by the Canadian Highway Bridge Design Code of 2000. The second support type was similar to the first one but with stressed springs between the nuts, over and under the steel base plate. In the third case, rubber-bearing pads were utilized between the base plate and the concrete foundation. In the fourth case, the steel pole was embedded into the soil with a certain embedding length (no concrete foundation is used). The structural response focused on energy absorption as well as the deformation of the steel pole. The fourth system of steel pole supports was proved to be strong enough to offer protection during minor impacts and under service loading, and to remain flexible enough to avoid influencing vehicle occupants, thus reducing fatalities and injuries resulting from the crash.
Developing FE-Tire Model Library for Durability and Crash Simulations
Masaki Shiraishi, Naoaki Iwasaki - Sumitomo Rubber Industries, LTD, Tomoharu Saruwatari, Kimihiro Hayashi - The Japan Research Institute,Ltd.
Cheng-Tang Wu - Livermore Software Technology Corporation, Mark E. Botkin, Hui-Ping Wang - GM R & D Center
Fuminori Oshita - The Japan Research Institute Ltd., Kiyoshi Omori, Yuko Nakahira, Kazuo Miki - Toyota Central R&D Labs, Inc.
A finite element human model, THUMS (Total HUman Model for Safety), was developed in order to study human body responses to impact loads. This paper briefly describes the structure of the human model, as well as some of the results of the simulations conducted to validate the model.
Ala Tabiei, Jin Wu - University of Cincinnati
Numerical simulation of cracked structures is an important aspect in structural safety assessment. In recent years, there has been an increasing rate of development of numerical codes for modeling fracture procedure. The subject of this investigation is implementing automated fracture models in the DYNA3D nonlinear explicit finite element code to simulate pseudo 3-D crack growth procedure. The implemented models have the capabilities of simulating automatic crack propagation without user intervention. The implementation is carried on solid elements. The methodology of implementing fracture models is described. An element deletion-and- replacement remeshing procedure is proposed for updating the explicit geometric description of evolving cracks. Fracture parameters such as stress intensity factors, energy release rates and crack tip opening angle are evaluated. The maximum circumferential stress criterion is utilized to predict the direction of crack advancement. Seven crack problems are presented to verify the effectiveness of the methodology. Mesh sensitivity and loading rate effects are studied in the validation of the presented procedure.
Anthony P. Taylor - Irvin Aerospace Inc.
Irvin Aerospace Inc. has used the LS-DYNA Explicit Finite Element Analysis (FEA) tool for over five years for that analysis of static and dynamic fabric problems. The references provide many examples of this previous work. Our first application was the analysis of airbag landings for several spacecraft programs, including Reusable Launch Vehicles (RLV's), various Unmanned Air Vehicles (UAV's), Military Airdrop Systems, and planetary exploration systems. These programs are thoroughly covered in the references, including comparisons between simulation and test. Our database of test to simulation comparisons and understanding model details where simulation does or does not apply continues to grow. Additional static and dynamic simulations include various pressurized fabric beams and fabric impact analysis; these are also covered in the references, including another paper presented at this conference. In the past year, Irvin has begun to explore the FSI capability within LS-DYNA through the explicit Navier-Stokes solver, the ALE solutions technique, and the various coupling options. This capability begins to provide Irvin with a capability, which in our industry is currently only available in Government Labs. The interaction of fluid systems and fabric is both the most basic of recovery system (parachute) problems, and perhaps the most difficult fluid structure interaction problem to solve. By beginning with simple problems, and continuously increasing the complexity, we have created early examples of where this simulation technology may lead. Along the way, we will include model size, solution time, and project to problems that will be solvable in the next two years. Additionally, we will report on required algorithmic enhancements and our suggestions on how to approach these. We will also present examples where we begin to apply the recently added Incompressible Navier-Stokes solver in LS-DYNA 960. Unfortunately, we will not report on comparisons to test data as, at the time of this writing, these are not available.
Alexander V. Konyukhov, Sergey A. Mikhaylov - Kazan State University, Russia
The analysis of helicopter during landing includes both complicated experimental tests and numerical calculation. Up to now very simple models in helicopter engineering have been used in Russia. Contemporary investigation of these problems involves using modern engineering software. The mechanical models included in these software allow to describe highly nonlinear dynamic behavior of engineering structure. This article contains rudimentary step-by-step development of numerical model to analyze behavior of skid landing gear in order to obtain optimal numerical model. Main points of the optimal numerical model are related to reducing cost of the verification experiment as well as hardware requirements. The base software for numerical activities is LS-DYNA with pre- and post- processors in ANSYS.
Dynamic Pulsebuckling Analysis of FRP Composite Laminated Beams Using LS-DYNA
Zheng Zhang, Farid Taheri - Dalhousie University
Buckling and post-buckling of composite structures have been important research topics since composite materials became widely used in engineering. As a result, significant volume of research has been done on their static stability, while relatively less has been devoted on characterizing their dynamic buckling and post-buckling response. The literature became particularly scares when considering the dynamic pulsebuckling and post buckling of axial components subjected to axial impact. This paper, therefore, presents the findings of our finite element analysis of dynamic pulsebuckling response of slender laminated fiber reinforced plastic (FRP) composite beams, with initial geometric imperfection, subject to axial impulse using LS-DYNA. Dynamic pulsebuckling, as an instability form, or in the form of excessive growth of lateral or out of plane displacements, is resulted from a transient loading function of a single pulse with a magnitude greater than the static Euler buckling load. The FRP laminated composite beam with initial geometric imperfection, subject to axial impact of a moving object, is modeled by the Belytschko-Tsay shell element. The moving object is defined as a rigid wall with a mass and initial velocity. Dynamic pulsebuckling of an imperfect beam is characterized by the sudden and drastic increase in the lateral deflection while the axial load bearing capacity remains unchanged relatively when the impact momentum reaches a critical value. Numerical results show that momentum of the moving object may be considered as a viable parameter for predicting the dynamic pulsebuckling limit of the beam. In this investigation, the effect of initial geometric imperfection used to promote instability was investigated and was shown to be a significant factor in promoting pulsebuckling. The effect of boundary conditions was also investigated and the significances of the axial and rotational restraints were demonstrated with numerical examples. A predictive criterion for the onset of pulse buckling was also presented.
Economically Improving Crash Worthiness of a Large Propane Tanker
Phillip H. Burnside - PPG Industries, Ed Hampton - Engineering Applied Sciences Inc.
Approximately every three years a 65,000 lb propane tractor-trailer crashes resulting in explosion that usually kills several people. The study presented in this paper first simulates the effects observed at one of these accident sites. This was simulated in LS-DYNA by building a full length model of the tanker trailer and also including the liquid in the tanker. The presence of the liquid in the model provide the initial effects of liquid on the tanker. The resulting model correlated very closely with the actual observation seen at the crash site. Then a variety of options where explored to determine how to improve the crash worthiness of the tanker for several crash scenario's. The result of this work illustrated that for less than $20,000 the velocity that would cause failure could be raised from 20 mph to over 55 mph through the use of energy absorbing materials.
Energy-Absorbing Wheel Tethers for Racecars
Brian A. Coon - M.S.C.E., E.I.T., John D. Reid - University of Nebraska-Lincoln
Wheel tethers are frequently used on racecars to prevent detached wheels from flying freely away from the car and injuring spectators. Extremely stiff tethers may cause the wheel assembly to be either yanked back toward the car, putting the driver in danger or to be snapped free at an uncontrolled trajectory, exposing spectators, other drivers, and workers to danger. Conceptual design of energy absorbing wheel tether systems was performed using the finite element program LS- DYNA. Two major approaches to energy absorption were explored, both of which involved metal bending. For absorbing energy through sheet metal bending, parametric studies showed that a minimum of 4 through-the- thickness integration points were required to capture good elasto-plastic behavior of shell elements. Additionally, for absorbing energy through solid tube bending, it was found that a circular cross-section in elasto-plastic bending must be modeled with a minimum of 12 solid elements in the cross-section. The developed tether design was able to absorb a total of 10 kJ of kinetic energy from the wheel assembly. This amount of energy is equivalent to reducing the trajectory height and distance of a 68-kg w
Gernot Oberhofer, Harry Dell, Dmitri Dell, Helmut Gese - MATFEM
In sheet-metal-forming the forming limit curve (FLC) is used for ductile sheets to predict fracture in deep drawing. However the use of the FLC is limited to linear strain paths. The initial FLC cannot be used in a complex nonlinear strain history of a deep drawing process or a successive stamp and crash process including a significant change in strain rate. The CRACH software has been developed to predict the forming limit of sheets for nonlinear strain paths [1]. It has been validated to predict instability for bilinear strain paths with static loading in the first path and dynamic loading in the second path for mild steels [2]. As the postprocessing of strain paths from single finite elements in CRACH is not economic for industrial applications MATFEM initiated a project to couple CRACH directly with FEM-Code LS-DYNA using a user- defined material model. This allows a prediction of possible failure during the simulation for all elements with respect to their complete strain history. A special strategy has been developed to include CRACH without extensive increase in total CPU time. The developed interface to LS-DYNA allows also the implementation of other failure criteria demanding the history of deformation like for example a tensorial fracture criterion. In order to test the reliability of the calculated safety factor experimental tests for bilinear strain paths have been simulated [2]. In this case the experimental and numerical investigations have been made on two-stage forming processes (static in the 1st stage and both static/dynamic in the 2nd stage) . The static-static case should simulate a stamping process with bilinear strain path. The static-dynamic case should simulate a successive stamp and crash process. The simulation of a complex deep drawing problem including areas with significantly nonlinear strain paths has been simulated with LS-DYNA/CRACH-coupling. It can be shown that the prediction of CRACH can differ significantely from a "standard" prediction based on the initial FLC. The coupling of LS-DYNA and CRACH showed the potential to predict possible fracture in deep drawing and crash loading at an early design stage and allowed to optimise geometry and material quality to significantly reduce later problems in real components.
eta/VPG: A Virtual Crash and Safety Environment for FMVSS and ECE Standards
Akbar Farahani, Arthur Tang, Tim Palmer, Zubair Uddin - Engineering Technology Associates, Inc.
Vehicle manufacturers, in an effort to reduce costs and meet the demand of customers are constantly reducing product development time. At the same time we see more regulations from governments, primarily aimed at vehicle safety. In additions there are variations in global regulations, such as ECE and FMVSS regulations. In order to meet the objective of reducing time and costs, manufacturers are forced to rely more and more on the virtual prototype to avoid the time and cost of constructing and testing prototypes, and to gain the insight necessary to make the current vehicle design better than past products in the area of performance and efficiency. These, in the minds of the engineering community, may be contradicting objectives. We have less time to perform more analyses, and not only that, but more critical analyses which may have more impact on the success of the vehicle when compared to the commercial impact of the analyses performed 5-10 years ago. The automotive industry is legally required to design vehicles to meet the Federal Motor Vehicle Safety Standards (FMVSS) or ECE/EEC Homologation Regulations as well as Corporate/Industry Standards. These standards are ever-increasing due to consumer awareness and the industry focus on vehicle safety, resulting in a conflict – we are increasing the simulation workload, and shrinking the time available to perform the analysis. Therefore, there exists a need to streamline all routine processes, and gain maximum efficiency from the engineer's limited time. This paper describes the development of a set of tools which enable engineers to automate many routine crash and safety analysis tasks, gaining efficiency, accuracy and productivity.
Evaluation of the Dropping of a Propeller Shaft During Installation on the USS COLE a DDG 51 Class Destroyer
Phillip Burnside - United States Naval Reserve
A terrorist bomb damaged the USS COLE by putting a hole in the side of the ship that was over 30 feet in diameter and flooded the forward engine room. After the ship was stabilized it was placed on the heavy lift ship, the BLUE MARLIN. The BLUE MARLIN brought the USS COLE back to Ingalls shipyard in Pascagoula, Mississippi for repair as seen in figure 1. The Navy wanted to expedite the repairs to the USS COLE and so parts from the battle damage spare inventory were used to obtain components that needed to be replaced to significantly reduce the lead-time needed. During the repair it was determined the shafts needed replacement. To do this each section of the shaft is slowly slid into the hull of the ship using rigging to swing it through the openings in the bulkheads. It was during one of these rigging moves that a section of the shaft was being temporarily suspended by rigging during installation into the ship just short of a bulkhead shaft clearance opening. While in this configuration the rigging at the inboard end of the shaft failed. This dropped the shaft about 12 inches onto a temporary channel that was welded to the bulkhead to support the shaft while it is passed through the bulkhead opening.
William Altenhof, Rita Turchi - University of Windsor, Anne-Marie Harte - Cymat Corp
This research deals with the experimental and numerical testing of aluminum foam filled mild steel tubular hat sections under axial compression conditions. The presence of aluminum foam within the tubular hat section provides a means of stabilizing the buckling process of the tube under axial compression. This method of applying internal support allows for a greater number of folds to be observed in the axial crushing of the hat sections and hence an increase in the energy absorption of the tube filled with aluminum foam, compared to a regular hat section without the presence of metallic foam. Experimental testing was conducted on mild steel tubular hat sections with and without the presences of aluminum foam within the tube. Load/displacement curves were developed from the experimental tests and integrated to determine the energy absorption capabilities of the tubular hat sections and the influence of the metallic foam. Finite element simulations, using LS-DYNA, were conducted on numerical models of the experimental testing procedure. An acceptable engineering correlation between the experimental and numerical testing methods was observed. This paper will present and compare the experimental and numerical observations from the compressive tests and also provide information on the energy absorption capacity of the tubular hat sections.
S. Subutay Akarca, Dr. William J. Altenhof, Dr. Ahmet T. Alpas - University of Windsor
Wear is a critical phenomenon affecting service life of products. Therefore, wear prediction is an important concern of study. In this study, sliding contact was modeled using LS-DYNA. FEMB was used to create the geometry of the model and the input file was manually modified as necessary. Studies were done to test, calibrate, and validate the model in LS-DYNA before simulation of the sliding wear by an asperity sliding over a plastically deforming and work hardening material surface. A flat half-space with dimensions of 30μm depth and 100μm width is subjected to sliding contact by a semicircular asperity of radius 10μm. The third dimension of the model was assumed to be infinite and therefore a plane strain condition was studied. Elastic indentations were performed to validate the finite element model. Elastic indentation results were compared to the predictions of the Hertz theory of elastic contact. With the help of mesh convergence study the best conditions to simulate sliding wear were determined. Mesh dimensions, hourglass control, contact algorithm, application of the normal load, and mass scaling were the main issues of the study. According to the Hertz theory, the maximum contact pressure and the maximum shear stress were calculated as 2684 and 805 MPa for the conditions studied. Numerical models predicted 10-15% higher values higher values for those stresses. However, normalized stress values show a very good agreement with the theoretical predictions.
Finite Element Modeling of Cable Hook Bolts
John D. Reid - Brian A. Coon - University of Nebraska-Lincoln
Component analysis of any complex system is frequently required to determine the true accuracy of a finite element model. Although a composite system may yield the "correct" final results, the system is not truly accurate unless individual components are performing correctly. The purpose of this paper is to describe the component testing and finite element modeling of a standard 5/16"-18 x 2" galvanized shoulder hook bolt used in cable barrier systems. These bolts hold the cable to the post of a cable barrier system. During a vehicle impact with the system, the cable loads many of the restraining hook bolts in different directions. Several of the hook bolts will reach their bending yield limits and "open up," allowing the cable to disengage. This is designed behavior which allows the cable to capture the impacting vehicle. Successful modeling of these bolts is essential to have an accurate finite element model of a complete cable barrier system.
Finite Element Simulations and Testing of Washington State Precast Concrete Barrier
Akram Abu-Odeh, D. Lance Bullard - Texas Transportation Institute, Richard B. Albin - Washington State Department of Transportation
Since the early 1970's, the Washington State Department of Transportation (WSDOT) has used precast concrete barrier (as shown in Figure 1) for both temporary and permanent installations. The use of this barrier in high impact areas has increased through the years and is one of the primary barriers currently used on Washington State highways due to its inherit ease of installation and repair.
High Performance Computing with Microsoft Windows: Meeting the Computational Requirements of Engineering Applications
David A. Lifka - Cornell University
The Cornell Theory Center (CTC) ran proprietary UNIX-based systems from IBM, SGI and others for over ten years as a national supercomputing center. Today, CTC is operating the world's largest Windows® scale-out systems with improved reliability, manageability, and total cost of ownership. This presentation focuses on the experience, benefits, and issues and key components for success CTC had moving from proprietary big-iron to industry-standard Windows clusters, to serve the midrange to high-end computing needs of their business, government and education clients. Of these clients, engineering applications are often the most computationally intensive and thus serve as good acid tests for the performance, reliability, and usability of HPC systems. The presentation will also include some representative performance results of LS-DYNA and other engineering codes running on Windows based computational clusters.
Honeycomb Modeling for Side Impact Moving Deformable Barrier (MDB)
Moisey B. Shkolnikov
Usually honeycomb is used as an energy absorber under impact loads. LS-DYNA constitutive model MAT-26 (*MAT_HONEYCOMB) is to mathematically model honeycomb as an energy absorber. The NHTSA MDB is a physical model of a typical impacting vehicle in side impact tests. The frontal part of MDB is made of honeycomb not just as an energy absorber but as a physical model of a typical car front end. Therefore, here the use of MAT-26 has some particularities, which are described in the paper. The MBD LS-DYNA model has been successfully used at GM for the last ten years.
Robert E. Dick - Alcoa Technical Center
In the United States, in the year 2000, over 100 billion aluminum beverage cans were manufactured. Lightweighting of these aluminum D&I beverage cans has been a continuous process for more than 35 years. Aluminum beverage can "ends" have been made progressively smaller over the years in order to reduce costs. Likewise, cost control efforts have resulted in continuous reduction of the net metal requirements for the can body. To reduce the weight and cost of the "bodies", cans with thinner sidewalls, reduced neck diameters and smaller base diameters have been developed. The reduction in cost has been achieved while maintaining functionality, structural performance, and formability of the can. Today, the gauge of can body stock is as low as 0.0098 inches. With small base diameter cans and a sheet thickness that continues to decrease, the likelihood of profile wrinkling during can forming increases, particularly in the redraw process. Redraw wrinkling is influenced by many factors such as mechanical properties of the aluminum sheet, tooling geometry, contact conditions including the effects of lubrication, and process boundary conditions. These factors are readily handled using the finite element method. A numerical technique for calculating the severity of the redraw wrinkling or wrinkle factor from an LSDYNA finite element analysis is employed. Using this wrinkle factor, and a fully parametric input generator, improvements to the beverage can redraw process are developed.
Improving Crash Analysis Through the Estimation of Residual Strains Brought About by Forming Metal
William Broene - Brown Corporation of America
This paper describes a method that can be used to estimate the residual strains from the forming of sheet metal without running forming simulations. For a first-order crash analysis, using estimated residual strains rather than the strains reported from several forming simulations increases the speed of the design process. The method estimates residual forming strains from the part geometry itself and assumes that the part was formed from a planar sheet of metal. The importance of considering the forming history of a part is demonstrated by comparing crash analysis results with and without the consideration of these residual strains. Along with this, physical test results will be compared of a part as formed and an identical part which was heat treated to relieve some of the cold working strains. Once the importance of considering forming history has been established, an alternative method of estimating residual strains will be examined. Crash analysis results using forming simulation residual stresses and strains will be compared to analysis results using estimated strains from the alternative method. Finally the scope of application of this strain estimation method will be discussed.
Incorporation of Material Model into LS-DYNA Implicit to Model the Shear Behavior of Uncured Woven-Fabric Composite Materials
Jennifer L. Gorczyca, James A. Sherwood, Darin S. Lussier, Julie Chen - University of Massachusetts Lowell
A shear-frame FE model for use in the LS-DYNA implicit code was created to predict the forming behavior of an uncured woven-fabric composite material. This FE model contains fully integrated shell elements and beam elements. A material model developed by McBride and Chen for plain-weave woven composite materials and later refined by Bulusu and Chen to account for different fabric weaves was incorporated into LS-DYNA implicit to model the behavior of a 40-60 glass-polypropylene satin-weave fabric as the fabric deformed in a shear-frame experiment. The normalized force-displacement results from the FE model were compared to the experimental results.
Interpretation of Deformation Pattern in Automotive Rails in Frontal Impact
Joseph Hassan, K. Ding, G. Nusholtz - DaimlerChrysler Corp. USA
Two barriers are commonly used to evaluate the response of a vehicle in a frontal impact: the rigid barrier and the offset deformable barrier. They produce different deformation patterns, which opens up the possibility that at least one of them does not represent real world crashes. One possible cause of the difference is that an impact into a rigid barrier generates significantly greater stress waves than impacts in the real world resulting in final deformation patterns that are different from those seen in the field. To evaluate this conjecture models of two types of rails each undergoing two different types of impacts, are analyzed using an explicit dynamic finite element code. Results show that the energy perturbation along the rail depends on the barrier type and that the early phase of wave propagation has very little effect on the final deformation pattern. This implies that in the real world conditions, the stress wave propagation along the rail has very little effect on the final deformed shape of the rail.
Materially & Geometrically Nonlinear Woven Composite Micro-mechanical Model with Failure for Finite Element Simulations
Ala Tabiei, Ivelin Ivanov - University of Cincinnati
A computational micro-mechanical material model of woven fabric composite material is developed to simulate failure. The material model is based on repeated unit cell approach. The fiber reorientation is accounted for in the effective stiffness calculation. Material non-linearity due to the shear stresses in the impregnated yarns and the matrix material is included in the model. Micro- mechanical failure criteria determine the stiffness degradation for the constituent materials. The developed material model with failure is programmed as user defined subroutine in the LS-DYNA finite element code with explicit time integration. The code is used to simulate the failure behavior of woven composite structures. The results of finite element simulations are compared with available test results. The model shows good agreement with the experimental results and good computational efficiency required for finite element simulations of woven composite structures.
Bradley N. Maker, David J. Benson - Livermore Software Technology Corporation
Modal analysis methods offer an opportunity for tremendous cost savings compared to traditional explicit approaches to transient dynamic analysis. Modal methods approximate the structural response of a body by a linear combination of pre-computed mode shapes, eliminating the need for explicit element processing. LS-DYNA's new modal analysis capability is combined with existing rigid body features to offer the additional advantage of large rigid body motion with superimposed linear modal response. This allows a portion of an LS-DYNA model to be represented by modes, while other parts of the model are treated with standard nonlinear explicit methods. LS- DYNA has also been enhanced to compute several types of modes, including eigen modes, constraint modes, and attachment modes. These modes are written to binary databases which can be viewed using LS-POST, and used as input to subsequent modal analyses. This paper introduces these new features for modal analysis, focusing on modeling procedures, input parameters, and examples of potential cost savings.
Jason J. Tao - Delphi Automotive Systems
A suspension damper module is an integration of the vehicle chassis components that control suspension motion. Various analytical tools are currently used in vehicle suspension analyses and component designs. However, these tools are not particularly useful for analysis of proposed damper module designs since they typically do not accurately represent component interactions and force distributions within the module. This paper describes a finite element model of a suspension damper module using an explicit finite element code, LS-DYNA. The modeling techniques used to construct the components within the modular assembly are presented. The LS-DYNA model was first correlated with a side load test of the damper module on an MTS machine. The analysis results were also compared with those from an ABAQUS model of the same module. A parametric study was then conducted to investigate the effects of some design parameters on the piston side load in the damper system.
Modular Strategy To Build Full Vehicle Finite Element Mode
Subrato Dhar, William E. Hohnstadt, Jeffrey D. Green - General Motor Corporation
The modular approach developed is a unique methodology for building a full vehicle finite element model which allows the use of a single vehicle model, assembled using component modules, to simulate multiple test configurations. This concept allows multiple users to efficiently contribute to construction of a model that can be used to run any number of test configurations. The benefits of a modular approach to full-vehicle finite element model were demonstrated by the C/K (full size truck) product line. While some configuration must be validated using physical tests, these tests can also be used to correlate a finite element model. Perturbation of the model can then be used to evaluate similar configurations and increase confidence in the design, without requiring additional hardware. This modular process can be implemented on all platforms as well, but with lesser savings for less complex products.
Multi-body Dynamic Simulation of Acti-Valve
Cunjiang Cheng, GEO Widera - Marquette University, Michael Fassett - Acti-Valve Inc.
A computer simulation of a valve (Acti-Valve) is generated using LS-DYNA. Fluid-structure interaction is considered in the finite element analysis (FEA). The stress, displacement and pressure distributions are analyzed during the opening movement of the valve under 1000 psi line pressure.
K.J. Craig - University of Pretoria, Nielen Stander - Livermore Software Technology Corporation, D.A. Dooge - DaimlerChrysler Corporation, S. Varadappa - Quantum Consultants, Inc.
This paper describes the multidisciplinary design optimization of a full vehicle to minimize mass while complying with crashworthiness and Noise, Vibration and Harshness (NVH) constraints. A full frontal impact is used for the crashworthiness simulation in the nonlinear dynamics code, LS-DYNA. The NVH constraints are evaluated from an implicit modal analysis of a body-in- white vehicle model using LS-DYNA. Seven design variables describe the structural components of which the thickness can be varied. The crashworthiness constraints relate to crush energy and displacement, while the torsional frequency characteristics are obtained from the modal analysis. The Multidisciplinary Feasible (Fully Integrated) formulation, in which full sharing of the variable sets is employed, is used as the reference case. In an attempt to investigate global optimality, three starting designs are used. Based on a Design of Experiments analysis of variance of the fully-shared variable results for each starting design, discipline-specific variables are selected from the full set using the sensitivity of the disciplinary responses. The optimizer used in all cases is the Successive Response Surface Method as implemented in LS-OPT. It is shown that partial sharing of the variables not only reduces the computational cost in finding an optimum due to fewer, more sensitive variables, but also leads to a better result. The mass of the vehicle is reduced by 4.7% when starting from an existing baseline design, and by 2.5% and 1.1% when starting from a lightest and heaviest starting design respectively.
New LS-DYNA Fluids Solvers
Grant O. Cook, Zeng-Chan Zhang - Livermore Software Technology Corporation
This paper discusses two new fluid solvers that will be included with releases of LS-DYNA after LS960. The first one is a new compressible solver based upon the Space-Time Conservation Element and Solution Element Method (or the CE/SE method for short), and the second one is an incompressible fluid FEM solver.
Non-Penetrating Impact Simulation of Stitched Resin Film Infused Composites
A. M. Floyd, R. Vaziri, A. Poursartip - The University of British Columbia
The CODAM constitutive model has been implemented in LS-DYNA as a user-defined material model (UMAT). Using this material model, quasi-static over-height compact tension (OCT) tests on a stitched resin film infused (S/RFI) carbon/epoxy composite material were simulated, and the results demonstrated good agreement with the measured force and crack mouth opening displacement (CMOD). The same CODAM inputs were then used to simulate non-penetrating impact events on the S/RFI material. The simulations successfully predicted the peak force and event durations for targets oriented in one direction, but under-predicted the peak force and over-predicted the event duration for the opposite target orientation.
Numerical Differences Observed Due to Different Binaries of LS-DYNA and Due to the Use of Various Compiler Options
Guangye Li, Wei David Chen, Jeff Zais - IBM
This paper compares the numerical results generated with different versions of LS-DYNA, including SMP versions ls950d, ls950e, ls960 (all with single precision), SMP version ls960 with double precision, and the MPI version mpp960. The car crash simulation model used in this study is the Neon model generated by the National Crash Analysis Center. The plotted results include internal energies, sliding interface energies, displacements, velocities and accelerations. Most of the results were obtained on IBM AIX systems with POWER3-II and POWER4 processors. To show the effect of different floating point round off methods, results are compared between binaries generated from the exact same LS-DYNA source code, but compiled by using different compiler floating point options. Furthermore, the comparisons also included the numerical results from a Linux cluster based on the Intel Pentium III processor, using the LS- DYNA MPI version mpp960 binary compiled by using the Intel compiler.
Numerical Simulation of Light Armoured Vehicle Occupant Vulnerability to Anti-Vehicle Mine Blast
Kevin Williams - Defence R&D Canada - Valcartier, Francois Fillion-Gourdeau - Université Laval
An ongoing program at Defence R&D Canada to reduce the vulnerability of Light Armoured Vehicle (LAVs) to anti-vehicular blast mines is relying heavily on numerical simulation to help design and optimize add-on armour systems. One of the greatest challenges faced during the evaluation of the vulnerability of a given vehicle to blast mines is not only assessing the structural response of the vehicle but also evaluating the injuries sustained by the vehicle occupants due to the accelerations induced by the blast. Anthropomorphic test devices (ATDs such as the Hybrid III) are used in the experimental program but these human surrogates were developed specifically for automotive crash tests. The loading conditions observed during a mine detonation, particularly where there is a breach in the hull of the vehicle, are such that extensive damage can be caused to the ATD. In addition, placing more than 2 or 3 ATDs in a vehicle is prohibitively expensive. As a result, the use of ATDs is somewhat limited. Numerical techniques allow any number of vehicle occupants to be simulated even in scenarios where there is potentially catastrophic failure of the hull. This paper presents the results of a series of simulations performed with LS-DYNA. A finite element model of the Canadian Cougar AVGP LAV, previously validated against experimental data for mine blast, was modified to include details of the rear crew compartment. The vehicle occupants were modelled using the GEBOD simplified ATD model incorporated in LS-DYNA. A simulated blast from a 6-kg C-4 mine surrogate was used to load the vehicle model. The predicated accelerations and velocities for various parts of the GEBOD dummies were compared to injury threshold criteria.
David J. Benson,Morten R. Jensen - University of California, San Diego, Nielen Stander - Livermore Software Technology Corporation, Kenneth J. Craig - University of Pretoria
A response surface optimization algorithm for structural material or parameter identification is evaluated. The algorithm used is the Successive Response Surface Method (SRSM) available in LS-OPT. To illustrate the robustness of SRSM as a material identification tool, two test cases are presented. The first concerns the identification of the power-law material parameters of a simple tensile test specimen. The second test case involves the identification of a model to characterize the brittle damage in a composite laminated structure. It is shown that SRSM is an effective tool for material parameter identification involving strongly nonlinear materials.
Optimum Design of a Cellular Phone Using LS-OPT Considering the Phone Drop Tes
Jung Woo Kim - R & D Center, In-Yong Jo, Young-Gu Chung, Jae Moon Lim - KOSTECH Inc.
The main factor of the cellular phone fracture is the impact due to the phone drop. Two cases of design criteria are assigned to reduce the damage of the phone for the drop test. One is that the main part and the battery should not be separated, being dropped at a height of 30 cm. The other is that they should be separated, being dropped at a height of 150 cm. The separation between them could reduce the damage of the cellular phone. However, it is undesirable for the battery to be frequently separated from the phone at a low height. The purpose of this study is to optimize the locking knob of the cellular phone considering the phone drop test at a height of 30cm. The design variables are the width and the thickness of the locking knob. LS-INGRID is adapted to automate the optimum design process because the shape of the locking knob could be changed in the design process. The optimum design is performed using RSM (response surface method) in the LS-OPT. The optimum design values are determined to optimize the displacement at the certain position of the locking knob of the cellular phone.
Optimum Design of a Steel Bar Breaking System in a Sled Test Facility Using LS-OPT
In-Yong Jo, Young-Gu Chung, Hyung-Joo Lee, Jae Moon Lim - CAE Team, KOSTECH Inc.
The steel bar breaking system is a component of sled test system for the automobile crashworthiness. The purpose of this study is to optimize the steel bar breaking system in order to extract the crash pulse close to the barrier test result. The design variables are the height, the thickness and the number of each array of the steel bar plates. The optimum design is obtained using DOE (design of experiments) and RSM (response surface method) in the LS-OPT. LS-INGRID is adapted to automate the optimization process because the dimensions of the steel bar plates could be changed in the design process. The optimum design values of the steel bar breaking system are determined to minimize the difference between the crash pulses of the test result and the simulation result.
PAB Deployment Simulation with Curved Retainer
Linhuo Shi - TG North America Corporation
Some passenger side airbags (PAB) are mounted on the cylindrical inflator directly through retainer with similar curvature of the inflator. To accurately simulate the deployment of such a PAB, a fine-tuned model using additional constraints in LS-DYNA are employed in this paper to simulate the curved mounted PAB. The results from the fine-tuned model are compared with the simulation results from the PAB models with simply fixed bag mouth. It is found that by approximating the curved mounting with simply fixed airbag mouth introduces negligible error in airbag deployment simulation.
Gustavo A. Aramayo - Computation Materials Science Group, Matthew H. Koebbe - XYZ Scientific Applications, Inc.
As part of the NCAP (New Car Assessment Program) a finite element model of a Ford Explorer SUV has been developed using a formulation that results in a model with arbitrary element size and element size distribution. This correct Abstract. model enables the developer and analyst to choose a finite element model most applicable to the specific crash scenario under study. The element size and element distribution are parametrically defined at the time of the model generation. The general model is verified against several specific models with different element size densities and distribution, and compared with experimental results of crash tests. In the analytical study, models are generated for several crash scenarios and for several degrees of vehicle engagement with the stationary obstacle.
Jin Wu, Ala Tabiei - Department of Aerospace Eng. & Eng. Mechanics
The G4(1S) strong post guardrail system is the most common guardrail system in the USA. Full- scale crash testing indicated that the vehicle rolled onto its impact side after exiting the guardrail system. This collision behavior of the roadside structure increases the occupant risk and is considered unsatisfactory for safety. Improvement of the G4(1S) guardrail system becomes an important issue concerned by the FHWA. The subject of this investigation is to understand the system behavior through parametric study and present a feasible approach for structural improvement. This paper provides a roadmap for simulation of highway safety structures. Some of the noteworthy observations are presented and discussed. The approach of reducing the embedment depth of post is investigated through both FE component simulation and full system crash simulation. This approach is recommended and is anticipated to be favorable for minimizing the risk of rollover of vehicles impacting the G4(1S) guardrail system.
Performance Analysis and Tuning of LS-DYNA* for Intel® Processor-Based Clusters
George Chaltas - Intel Corporation, W. R. Magro - Intel Americas
Using Intel software tools, including Intel® VTuneTM Performance Analyzer and Intel® Fortran Compiler, we analyze and tune the performance of MPP LS-DYNA* for clusters of Intel processors. We discuss the impact of various performance features of Intel processor-based systems, including vector/streaming instructions, on real LS- DYNA workloads. We compare single-precision performance and measure the impact of various cluster interconnect technologies.
Performance Evaluation on the ALE Formulation in MPP LS-DYNA
Yih-Yih Lin - Hewlett-Packard Company
The ALE fluid-structure coupling capability in LS-DYNA has become the main tool to accurately simulate the airbag-inflating process. However, it is very time-consuming: Running serially, it has been observed to take more than ten days on various computer platforms. Hoping to obtain speedup by parallelization, LSTC has been making efforts to implement the ALE formulation with MPP LS-DYNA. In this paper, the scalability of this implementation, with the number of processors up to 64, is investigated on an HP Superdome. While the result indicates the current scalability of MPP LS-DYNA is inadequate and its improvement is needed, a preliminary study predicts the McKinley processor of the Intel Itanium Processor Family will make the goal of simulating a full airbag-inflating process within 24 hours possible.
X.M. Chen - United States Steel Corporation, K. Palanisamy - ETA, Inc., X.H. Zhu - Livermore Software Technology Corporation
Finite element analysis (FEA) has proven to be a useful tool for stamping process analyses. FEA has also been used increasingly for hydroforming analysis in the industry. In this paper, some examples for various hydroforming process simulations using LS-DYNA are presented. The effects of material characteristics and process parameters on tubular hydroforming are discussed. A sensitivity study has been conducted on a simple geometry. Three steel grades: DS, HSLA and DP, and process parameters such as internal pressure, end feeding and lubricant are included in this study. Simulation results are also compared with experimental data. It is demonstrated that computer simulation can be used as an aid for optimal selection of those parameters to reduce time and cost in tool tryout. In addition, some of the simulation limitations are discussed in this paper.
Processing of Equality Constraints for Implicit in LS-DYNA v. 970
C. Cleve Ashcraft, Roger G. Grimes, Bradley N. Maker - Livermore Software Technology Corporation
LSTC is committed to building an implicit capability into LS-DYNA that is as capable as the flagship explicit capability. Over the years LSTC has added many different types of constraint handling capabilities in explicit that now have to be handled by implicit. The vast majority of these constraints are equality constraints imposed on the linear or nonlinear solution required at each time step. We will describe a new approach for handling equality constraints that has allowed us to robustly process them without placing unnecessary restrictions on how the user poses the constraints. Our new approach effectively and efficiently processes the constraints for the linear, nonlinear, and eigenvalue problems that have to be solved by the users of Implicit LS-DYNA. We compute a transformation based on the Jacobian matrix of the constraint equations and apply that transformation to form a reduced stiffness and, if necessary, reduced mass matrices. The transformation is also used to transforms vectors from the unconstrained space to the constrained space and back again. The only restriction placed on the structure of the constraint matrix is that it is full rank. We will also highlight the various constraints now supported for implicit solution in LS-DYNA v. 970 and demonstrate the solution of some problems illustrating these constraint features.
Quasi-Static Finite Element Analysis (FEA) of an Automobile Seat Latch Using LS-DYNA
Song Chen, Yuehui Zhu - Fisher Dynamics Engineering
In the present automotive industry, all suppliers and OEMs are focusing on designing, developing and manufacturing products and automobiles with higher quality, lower cost and faster delivery to the customers. The automobile industry has placed a significant amount of efforts including time and funding into developing products that can meet these challenges. This is probably one reason that in recent years Finite Element Analysis (FEA) has been widely used and become a mainstream design and developing process in automotive industry. This is especially true in the Noise, Vibration, Harshness (NVH) and safety fields. This paper presents a project of Fisher Dynamics in the system level Quasi-static FEA using LS-DYNA effectively directed the design of an automotive seat latch to meet the stringent high load requirements. The analysis successfully predicted the results of physical tests including the ultimate load. Hence the company was able to deliver a design in conformance with the specifications of the customer on time.
Recent Developments in LS-DYNA for Civil Engineering
Brian Walker - ARUP
• LS-DYNA has well-known applications for earthquake and blast/impact engineering – Building design development – Site response studies – Development of isolators and energy absorbers • Arup have recently added new features: – Damping model for vibration studies – Material model - Rock and general Mohr-Coulomb – Staged construction – Pore water pressure analysis • This paper will show some applications of the new features
Reduction in Time to Market of Automotive Seating System Using LS-DYNA
Hurshkumar G. Donde, Rakesh K. Lad, Prabal Kumar Biswas, Praveen B. Patil - Infosys Technologies Limited, Gordon Stace - Johnson Control Automotive UK Limited
The worldwide automotive industry is going through a sea change in order to get the share in the global market, which is becoming highly competitive & dynamic. The automotive OEM's are faced with conflicting demands & challenges. There is an increasing demand for cost & weight reduction, fuel economy & reduction in time to market on one hand and on the other hand there is even more increasing demand towards assuring improved occupant safety and comfort in complex crash & driving conditions besides the pressure from environmental regulations. The safety and environmental regulations are becoming increasingly stringent in the developed economies & the developing economies are catching up. These factors are driving the change in entire automotive industry value chain and the major sub systems suppliers are directly affected by this. One such sub-system is seating system, as it is major contributor to the occupant safety & comfort. The automotive seating system development process is becoming highly complex and challenging as the regulations pertaining to NVH (Noise, Vibration & Harshness)/ durability/ fatigue, static/dynamic strength and crash safety are becoming increasingly stringent besides OEM's pressure to reduce weight and cost. One of the major challenges is to reduce the time and the cost of developmental prototyping and testing. As a result most of the forward-looking organisations are beginning to move towards Virtual Product Development Environment (VPD). One of the most useful tools available to virtually simulate product performance under various dynamic conditions is LS-DYNA. This paper depicts the evolution of a rear seat system for the Ford Focus vehicle through effective use of LS-DYNA and other CAE tools, throughout the developmental life cycle. This program demanded a reduced program timeline of 18 months.
Nielen Stander - Livermore Software Technology Corporation, K.J. Craig - University of Pretoria
This paper evaluates the robustness of LS-OPT for response surface and design sensitivity-based optimization. The methodology uses linear response surfaces constructed in a subregion of the design space. These are constructed using either a design of experiments approach with a D-optimal experimental design or the available analytical or numerical gradient. The approach utilizes a domain reduction scheme to converge to an optimum. The scheme requires only one user-defined parameter, namely the size of the initial subregion. To test its robustness, the results using the method are compared to SQP results of a selection of the well-known Hock and Schittkowski problems. Although convergence to a small tolerance is predictably slow when compared to SQP, LS-OPT does remarkably well for these, sometimes pathological, analytical problems.
D. J. Eby, R. S. Sidhu - Applied Computational Design Associates, Inc., R.C. Averill, E.D. Goodman - Department of Mechanical Engineering
Crashworthiness problems, which are highly dynamic and nonlinear, do not lend themselves well to classical gradient optimization techniques. Evolutionary-based design approaches that employ a form of guided stochastic search algorithm have been successfully applied to these problems. While many design optimization approaches are limited to a small number of continuous design variables, the approach described here can productively search over hundreds at a time. The power of classical evolutionary algorithms can be increased by allowing flexible design variable decomposition and incorporating classical local optimization methods and/or by embedding them within adaptive agents, which communicate but work semi-independently on a common problem. The authors have developed a system that allows for flexible design variable decomposition while combining evolutionary algorithms with local optimization. Within this approach, autonomous agents break down a problem hierarchically, using problem-specific divide-and-conquer rules to organize design variables and design criteria into a set of highly decomposed, overlapped relationships. These agents simultaneously search a discretized design space at various levels of resolution and use different design variable representations, performance measures (combinations of objectives and constraints), and local search methods. The agents exchange information about the decomposed solution space with each other, helping them jointly to satisfy multiple constraints and objectives. This technology has been implemented into a software code called HEEDS (Hierarchical Evolutionary Engineering Design System), which can be run on a single processor or in a networked computing environment, including clusters of personal computers or simple networks of workstations. Using LS-DYNA explicit as the finite element solver within the HEEDS optimization environment, this process has been applied to several automotive lower compartment rail designs, resulting in significant gains in performance along with up to 20% reductions in mass compared to baseline rails designed by experienced engineers. An example application of this method is described herein.
Mark Z. Vulitsky, Zvi H. Karni - John J. McMullen Associates
Predicting the structural response of a naval vessel to a high explosive detonation is an important requirement in naval shipbuilding. Unfortunately, current analysis methods do not provide high level of confidence leading to the utilization of large structural design safety factors. As a result, ships are heavier and more expensive to construct and maintain than may actually be required. Moreover, more reliable predictions can support innovative structural configurations, which provide lower life-cycle costs with increased survivability. In the currently used approaches, pressure-time history is initially generated from empirical equations and/or test data, and then the time dependent pressure is applied to the structure. These approaches have many limitations and use various approximations. This paper highlights a numerical simulation procedure for the prediction of the effect of the detonation of high explosive compounds on steel structure. The dynamic simulation interfaces the blast wave predicted by the Jones-Wilkins-Lee (JWL) equation of state for high explosives (built-in the LS-DYNA equation of state library), with time dependent spatial response of the structure. The air surrounding the structure is modeled to represent the medium in which the blast propagates using the LS-DYNA multi-material elements. A linear polynomial equation of state is used to simulate the proper behavior of air. Several explosion tests with different configurations (internal and external) were conducted in order to quantify the effect of a detonation on different structurally representative test articles. It was established that the numerical simulation demonstrates good correlation with the empirical results.
Simulation and Validation of FMVSS 207/210 Using LS-DYNA
Vikas Patwardhan, Tuhin Halder, Frank Xu, Babushankar Sambamoorthy - Lear Corporation
Federal Motor Vehicle Safety Standard 207 and 210 applies to automotive seats, their attachment assemblies, and seat belt anchorage assemblies. These regulations ensure their proper location for effective occupant restraint, and it also minimizes the possibility of anchorage failure due to the forces resulting from a vehicle crash. These requirements are the most critical in seat development process and are generally considered the benchmark for an automotive seat's safety performance. Finite Element Analysis (FEA) is widely used to simulate the FMVSS 207/210 on a component level as well as on a complete seat system level. Quasi-static simulation using LSDYNA is one of the chosen methods to simulate the requirement. This paper will discuss a simple but accurate method to simulate and validate the FMVSS 207/210 test. The methodology describes the use of lighter body blocks to reduce the dynamic effect, simpler seat belt formulations, and the right use of element formulations and contact interfaces.
Per-Olof Marklund - Linköping University, Larsgunnar Nilsson - Engineering Research Nordic AB and Linköping University,
This paper explores simulation techniques for airbag inflation using a coupled fluid-structure approach. The application is to be seen as an initial study on the phenomena occurring in an airbag during an Out of Position occupant impact. The application problem is an airbag that is set to impact a head form. The head form is positioned at a very short distance from the airbag. A Multi Material Arbitrary Lagrangian Eulerian technique in LS-DYNA is used for the fluid and it is coupled to the fabric structure using a penalty based fluid structure contact algorithm. The results of the head form acceleration and velocity show good agreement to the corresponding experimental results. The results also show that at the early stages of the inflation a high-pressure zone is built up between the inflow and the head form. The consequence of this is that the pressure difference between the inflow and the high pressure zone is too low for an a priori assumption of sonic flow at the inlet.
Stochastic Analysis and Optimization of Full Vehicle System for Offset Crush
Hassan El-Hor, Nagappan Sekappan, Hamid Keshtkar - DaimlerChrysler Corporation
This paper attempts to account for the uncertainties inherited in the parameters involved in the offset crush of full vehicle system. The main objective of this work is to perform a reliability-based analysis to obtain the statistical characteristics of dash and toe intrusion responses in a 40 mph offset crush for a full vehicle system due to manufacture, material and design variability that will be defined in this study. Monte Carlo simulation Method (MCS) will be used in the analysis. Also, a reliability optimization will be performed to search for design solutions for the intrusion that meet the specified requirements on probability of constraint violation on an existing design. Single Loop, Single Variable (SLSV) approach will be used for this analysis. Finally, Six Sigma robust design will be performed to reduce the sensitivity of performance to uncertainties and therefore reduce the probability of constraint violation.
Strain Rate Dependent Micro-Mechanical Composite Material Model for Finite Element Impact Simulation
Ala Tabiei, Weitao Yi - University of Cincinnati, Robert Goldberg - NASA Glenn Research Center
The present study aims at implementation of a strain rate dependent, non-linear, micro- mechanics material model for laminated, unidirectional polymer matrix composites into the explicit finite element code LSDYNA. The objective is to develop an accurate and simple micro- mechanical, rate dependent material model, which is computationally efficient. Within the model a representative volume cell is assumed. The stress-strain relation including rate dependent effects for the micro-model is derived for both shell elements and solid elements. Micro Failure Criterion (MFC) is presented for each material constituent and failure mode. The implemented model can deal with problems such as impact, crashworthiness, and failure analysis under quasi- static loads. The developed material model has a wide range of applications such as jet engine jackets, armor plates, and structural crashworthiness simulation. The deformation response of two representative composite materials with varying fiber orientation is presented using the described technique. The predicted results compare favorably to experimental values.
Marcus Redhe - Linköping University, Larsgunnar Nilsson - Engineering Research Nordic AB and Linkoping University
The aim of this paper is to determine if Space Mapping technique using Surrogate Models in combination with the Response Surfaces Methodology (RSM) is useful in optimization of crashworthiness applications. In addition, the efficiency of optimization using Space Mapping will be compared to conventional structural optimization using the Response Surface Methodology (RSM). To determine the response surfaces, several evaluations must be performed and each simulation can be computationally demanding. Space Mapping technique uses surrogate models, i.e. less costly models, to determine these surfaces and their associated gradients with respect to the object and constraint functions. The original full model is used to correct the gradients from the surrogate model for the next iteration. Thus, the Space Mapping technique makes it possible to reduce the total computing time, needed to find the optimal solution. Two application problems are used to illustrate the algorithm. All examples are constrained optimization problems with one or two design variables. In all applications, the algorithm converged to the optimum solution. For the crashworthiness design problems the total computing time for convergence was reduced with 53% using Space Mapping compared to the conventional RSM. The conclusions are that optimization using Space Mapping and Surrogate Models can be used for optimization in crashworthiness design with maintained accuracy but with a significant reduction in computing time compared to traditional RSM.
Study on Optimal Design of Automotive Body Structure Crashworthiness
Wang Hailiang, Lin Zhongqin, Jin Xianlong - Shanghai Jiao Tong University
In this paper the optimal model of thin-walled sections of automotive body for structural crashworthiness is built. With computer design of experiment (DOE), the response surface model (RSM) of design can be obtained by carefully choosing a small quantity of samples in the design space. Pareto genetic algorithm (GA) is used in subsequently optimal design. With optimal design of thin-walled sections, the effects of the section parameters such as dimension and thickness on crashworthiness property are researched.
The Future of CAE Software How to Achieve Process Automation
Brian Huf - Ford Motor Company
Achieving Process Automation is goal of all software – Automatically do what a user needs to get done. CAE software is no exception. In previous years, technological advances have driven most of the progress in CAE software. CAE software development is now starting to follow the lead of many other software companies by leveraging the concept of Process Guidance (a.k.a. Wizards). This approach has been found to be very effective as well being an advantageous resting spot on the road to Process Automation. Developing and deploying Process Guidance software introduces new questions and opens new possibilities. Several scenarios and strategies are discussed and analyzed. Also included is a list of criteria that could be used to rate prospective software companies on their ability to successfully lead Ford on the path to Process Automation via Process Guidance.
P. Christopher Galbraith, Dylan N. Thomas - Medusa Computing Corporation
Sheet forming simulations have been shown to have a profound impact on the tool and die industry, but accurate solutions for large panels often require large amounts of CPU time. The development of MPP-DYNA has allowed a large number of CPUs to be applied to a single problem thus reducing total elapsed time. This paper discusses the use of MPP-DYNA for obtaining accurate solutions in small amounts of elapsed time using inexpensive PC-based clusters of computers
Amit Sharma, Ashok Deshpande, Raviraj Nayak - General Motors Corporation
The FMVSS210 regulation establishes requirements for seat belt assembly anchorage. The Federal government mandate requires use of Pelvic and Torso Body Blocks for testing belt anchor strengths for lap and shoulder belts respectively. The belt anchorages are to be designed to withstand loads of 13.34 kN if both lap and shoulder belts are used and 22.24 kN if only lap belts are used. The analytical simulation of the hardware test is done using LS- DYNA. Hardware testing is of quasi-static nature while the simulation uses the dynamic code. However the analysis could be made to approach the quasi-static test by adjusting some input parameters in the simulation. In addition, some input parameters need adjustment for making the model more robust and to make it correlate with the hardware test. This study involves the use of Optimal Symmetric Latin Hypercube Design to explore the design space, and to develop a fast surface response model. This response model can be viewed as a surrogate model to the actual LS- DYNA simulation. This response model is used to rank the input parameters by its percent contribution towards the variation of the output responses. After determining the fit of the response model, it is used to perform the stochastic simulation. The confidence interval for test correlation prediction can then be estimated. This technique can further be used for design sensitivity studies and for improving the vehicle structure with respect to FMVSS210 regulation.
USGA Rule 4-1e Optimization of a Golf Driver Head Using LS-DYNA and Altair HyperStudy®
Tom Mase - Michigan State University, Eric Nelson, Jeff Brennan - Altair Engineering, Bruce Pettibone - Independent Consultant
A simulation of USGA's test procedure for Rule 4-1e was optimized using 3 shape and 10 size design variables. The optimized solution increased the coefficient of restitution from 0.845 to 0.917 while maintaining stresses below 150 ksi and club head mass at 200 g.
Validation of a Loading Model for Simulating Blast Mine Effects on Armoured Vehicles
Kevin Williams, Robert Durocher, Benoit St-Jean, Jocelyn Tremblay - Defence R&D Canada - Valcartier, Scott McClennan - University of British Columbia
An ongoing program at Defence R&D Canada to reduce the vulnerability of Light Armoured Vehicle (LAVs) to anti-vehicular blast mines is relying heavily on LS-DYNA to help design and optimize add-on armour systems. A significant challenge in the numerical modelling work is the development of an accurate, or at least representative, loading history for the pressure and momentum transfer from the detonation of a buried blast mine. Arbitrary Lagrange-Eulerian (ALE) techniques offer some promise but the analysis is very computationally intensive. Another option that is more attractive from the point of view of simplicity (implementation and computation time) is an empirically based loading model. The LS-DYNA implementation of the CONWEP blast equations (*LOAD_BLAST) is one such example. While some authors have used this model to predict the effects of mine blasts on vehicle structures, there are significant limitations in this model. A more advanced empirical model for predicting the effects of blast mines on structures was developed for the U.S. Army Tank Automotive Command (TACOM) by Southwest Research Institute. This model has been implemented by the Defence R&D Canada - Valcartier (DRDC - Valcartier) in a pre-processor for LS-DYNA. A parameter study has been conducted using this implementation of the impulse model and the results are compared to those obtained from the CONWEP blast model. Validation is based on a series of experiments conducted at DRDC - Valcartier using square aluminium and steel test panels subjected to detonations of buried charges (surrogate mines) of 6 kg of C-4 explosive.
Web-Centric LS-DYNA - Development of a Technical Computing Portal
Dan Fraser, Youn-Seo Roh, Henry H. Fong - Sun Microsystems, Inc.
The development of a Technical Computing Portal (TCP) for monitoring and managing of LS- DYNA runs is described. The Sun TCP is a new collaborative tool for High Performance and Technical Computing. It facilitates access, workload distribution, job monitoring, and management of LS-DYNA and other technical application jobs in a heterogeneous computing environment. It can be easily customized by LS-DYNA users, and by LSTC and its distributors. TCP is based on Sun's iPlanet Portal Server, Java, and Sun Grid Engine technologies.


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2024 Black
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Coach Jess Onheiser
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Jess Onheiser graduated from Vanderbilt University, where she was a two-time All-American Lacrosse Conference member, a two-time IWLCA All-South Region First Team honoree, a two-time Academic All-American, and three-time member of the Southeastern Conference Scholar-Athlete Honor Roll. From 2004 to 2008, Jess was a member of the United States National Developmental and Elite team. Jess was inducted into the Vanderbilt Hall of Fame in 2013 and the Greater Baltimore Hall of Fame in 2017. She is also the founder and owner of Recruit-Her LLC, offering services to improve individual and team skills through personal training sessions and recruiting consulting in order to educate players and parents about the multifaceted recruiting process.
Jess joined Check-Hers in 2013 and is on the Board of Directors. Previous coaching experience includes being the Varsity Head Coach at Garrison Forest School, and Division I lacrosse at the Ohio University and Loyola University Maryland.
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Assistant Coach Alanna Wray
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