Development of Computational Model of Sport Utility VehicleSrdan Simunovic, Gustavo Aramayo and Thomas Zacharia

Computer Science and Mathematics DivisionOak Ridge National Laboratory

NHHTSA Project Review, October 20 1998

http://www-explorer.ornl.gov

OutlineStatusModeling ApproachAvailable ModelsThings to Finalize

StatusDeveloped parametric finite element model of 1998 Ford Explorer XLT 4x2Tested modelsfull frontal impactfrontal offset impactfrontal offset oblique impactDeveloped WWW-based model manipulationWWW based model generation available 12/98

Related Parametric FEM Projects at ORNLAluminum Intensive Vehicle Model DevelopmentUltra Light Steel Auto Body

Aluminum Intensive Vehicle

ULSAB

Fixed FEM Mesh ModelInitial FEM model was based on dirty geometryscanned geometry was not extensively modifiedregularity and connectivity of FEM mesh was enforced by direct placement of nodes on surfaces and by single FEM mesh realizationModel has varying degree of FEM mesh regularity and qualityframe - highbody - lowModel was tested in frontal and frontal-offset impact

Fixed FEM Model Features25k Nodes, 25k ElementsRelatively good resultsgood deformation, crash duration, accelerationmainly due to importance of frame in impact responseModel modifications not practicalregularity enforced by numerous ad-hoc constraints

Parametric FEM ModelObjectiveMore FEM meshes in less timeMethodology developed can be easily applied to other FEM modelsWant to learn more on vehicle impact simulationsHave not been done yet for such complex models

Advantages of Parametric ModelRapid generation of crash situation-specific modelsSimple model modification through parameter modificationAllows for investigation of convergence of simulation resultsBecomes possible to determine the best model for specific impact scenario

Disadvantages of Parametric Modeling ApproachLonger initial model development timeGeometry needs to be cleanSoftware not yet available for entire processManipulation of large number of parameters is cumbersome, therefore, model modification is usually limited to initial developers

Coarse FEM Mesh

Frontal Impact Model

Rear Impact

Frontal Impact

FEM Mesh ParametrizationClean up geometryconnections between CAD surfaces must be accurateCAD surfaces must be reorganized to fit FEM modelPick up general mesh topologyFor each part develop FEM mesh projection approachDetermine topology constrains enforced by neighboring partsCreate FEM mesh through projections on CAD surfaces

FEM Mesh ParametrizationEnforce FEM mesh connectivity through part boundaries by mesh topology constraintsMake FEM mesh projections using CAD entities, not coordinatesMake things as you goCAD, FEM mesh, mesh generator scripts, parsers, CAD-to-FEM-to-CAD, visualizationDebug!

Basic FEM Model

Coarse FEM Mesh

Basic Model - Results

Frontal Impact Model

Frontal Impact - Results

Model ModificationsImmediate fixesEngine mounts damping effectElevate frameReconnect left body mountBreak-off conditions for bumperUsers can specify needed modifications as they run simulations

Offset Impact Model

Offset Impact - Results

Pole Impact Results

Rear Impact

Detailed FEM Mesh in the Back

Rear Impact

Frontal Impact

Side ImpactModel

Detailed FEM Mesh on the Side

WWW Model InterfaceLarge number of mesh control parameters in basic model (> 200)very flexible FEM mesh topologydirect parameter manipulation intractable to anyone other than model developersModel modification can be facilitated through VRML interfaceUser access through API-like process

To Do - FEM Model RelatedFrame modificationsengine placement and mountstransmission placement and mountsdrive axle placementraise frameBody modificationsclose few minor gaps

To Do - Parametric FEM RelatedMesh topologyparameter placement evaluations (need suggestions)parameter propagation testsVerify with NHTSA testsWWW interface for FEM modelparameter propagation display (needs speed fix)connection between partssubpart displayparameter display and user input (speed fix)set up server for remote mesh generation (Unix, Win/NT)develop annotation procedure (primitives developed)

DeliverablesCurrent LS DYNA3D models available on WWWwww-explorer.ornl.govNext model release in early December 1998we can generate specific models in the meantime if needed, please help us to debug!Full verification with NHTSA testsmaterials property update as becomes availableWWW interface for model inspectionnew releases available daily