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Batch Meshing for Car Crash Test Simulations Dream or Reality?Author Guillaume Minault, Numerical Simulation Engineer PSA Peugeot Citron - Vlizy-Villacoublay (78) Phone : + 33 1 57 59 27 23 / E-mail : [email protected]
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Abstract In a very competitive cars and light commercial vehicles market, accelerating the development of new models is a key factor of success. Computational analysis has become an efficient tool for this. PSA Peugeot Citron is investigating how to improve the efficiency and quality of the major steps used in this process. Among them, meshing must be much faster using batch technologies. Recently, we have performed a benchmark with three major software editors among which Altair. It has shown that by using HyperMesh and BatchMesher for example, we could mesh typical body in white models faster provided the three following conditions are fulfilled. First, the process must guaranty good orthogonal property of the resulting mesh (software editor part). Second, we have to use finer mesh than today in our RADIOSS crash simulation models (PSA Peugeot Citron part). Third, the use of batch meshing in our complete simulation process must be validated. For this validation, we are working with Altair on a step by step program, from a single part to a complete body in white analysis. This presentation gives our conclusions (efficiency and quality) on one of the first validation cases: axial compression of a part component of the body in white.
Guillaume Minault
27/08/2007
Batch Meshing for Car Crash Test Simulations Dream or Reality?Introduction Problem Definition & Chosen Approach Analysis & Discussions Batch Meshing Process & Vocabulary Main Conclusions of our Benchmark Presentation of the First Step of our Validation Program Conclusions & Perspectives Acknowledgements
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Guillaume Minault
27/08/2007
IntroductionContext A highly competitive market : Cars and light commercial vehicles market A constant need of accelerating our new models development Today, computational analysis are systematically used on our projects We investigate how to improve the efficiency and the quality of the major steps of our numerical process. Among them : Meshing & AssemblyPost Processing Analysis Meshing Assembly
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Goal & Objectives Reduce the length of our meshing phases Maintain or improve quality of meshes First Applications targeted Crash Computation Body in White & Openings
Computation
Pre Processing
How ? Using Batch Technologies Using Process Automation
Simplified process of a crash test simulationGuillaume Minault 27/08/2007
Batch Meshing for Car Crash Test Simulations Dream or Reality?Introduction Problem Definition & Chosen Approach Analysis & Discussions Batch Meshing Process & Vocabulary Main Conclusions of our Benchmark Presentation of the First Step of our Validation Program Conclusions & Perspectives Acknowledgements
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Guillaume Minault
27/08/2007
Problem Definition & Chosen MethodProblem Definition How to use Batch Technologies & Process Automation : to reduce the duration of our meshing phases with no decrease of quality Chosen Method An internal analysis of our different needs for meshing A Batch Meshing Benchmark with different Software EditorsPart 1 with 3 editors including AltairVarious types of meshes Meshing single parts Based on CatiaV4 CADs* only Subframe ( Part 1 ) Rear Quarter Inner ( Part 1 )
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Part 2 with 2 editors including AltairMeshes for Durability, NVH** and Crash Simulations An industrial case of meshing : a Body in White Based on CatiaV4 and CatiaV5 CADs Body in White ( Part 2 )
A step by step Validation Program with AltairBatch Meshing and Computation of a SideMember under axial compression Batch Meshing and different Computations of a Body in White with Openings
Compression of a SideMember (Validation Program)
Guillaume Minault
* CAD = Computer Aided Design ** NVH = Noise, Vibration and Harshness
Batch Meshing for Car Crash Test Simulations Dream or Reality?Introduction Problem Definition & Chosen Approach Analysis & Discussions Batch Meshing Process & Vocabulary Main Conclusions of our Benchmark Presentation of the First Step of our Validation Program Conclusions & Perspectives Acknowledgements
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Guillaume Minault
27/08/2007
Batch Meshing Process & VocabularyCAD Meshing Assembly Pre-Processing Computation Post-Processing PSA Data : Mesh Specifications, CATIA CADs, Part Information (name, thickness, material)
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PSA Data ExploitationData check, data organisation
Manual / Automatic Batch Meshing Pre-ProcessingCreate BOM File, offset to mid-plane, allocate proprieties, prepare geometry (split surfaces, preserve edge) BM Batch Meshed ModelBM-MI Batch Meshed with Manual Improvement Model
Batch MeshingRun BatchMesher, export results (mesh, quality summary)
Batch Mesh Analysis & Manuel ImprovementFix elementary quality, minimize trias, improve mesh orientation
Guillaume Minault
* BOM File (Build Of Material File) = necessary input file of BatchMesher with parts information. 27/08/2007
Main Conclusions of our Benchmark (Parts 1 & 2)Altair BatchMesher & HyperMesh are among the best tools on the market
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Batch Meshing with Altair products : Is already fully operational on CAD with simplified geometry Can be quicker than usual hand-meshing (with a substantial gain of time) Leads generally to a Good Elementary Quality (warp, skew, taper) Is efficient when proceeded on high quality CADs Can deliver incorrect results which need Manual Improvement in particular : Correction of mesh orthogonality Is not available for volumes meshing with HEXA To Batch Mesh CADs with accurate geometry efficiently, we need: A smaller element size (around 5mm) than the one used today A good Data Organisation (CADs, Thickness, Material Vector, Material)
Guillaume Minault
27/08/2007
Batch Meshing for Car Crash Test Simulations Dream or Reality?Introduction Problem Definition & Chosen Approach Analysis & Discussions Batch Meshing Process & Vocabulary Main Conclusions of our Benchmark Presentation of the First Step of our Validation Program Conclusions & Perspectives Acknowledgements
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Guillaume Minault
27/08/2007
First Step of our Validation Program (1/6) : Problem DefinitionProblem Definition To validate Batch Meshing for the crash computation of a sidemember front edge under single axis compression. Physical Test SimulatedSidemember reinforcement Load Cells
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Axial Compression
Wooden Plate Subframe connection
Mobile PartGuillaume Minault
Sidemember Front Edge27/08/2007
Fixed Part
First Step of our Validation Program (2/6) : 4 different Meshes~ 1.8mm ~2.5mm ~ 1.8mm
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~3mm Thickness (mm)
Four different meshes realized : HM_12mm : 12mm Hand-Mesh HM_5mm : 5mm Hand-mesh BM_5mm : 5mm Batch-Mesh BM-MI_5mm : 5mm Batch-Mesh with Manual Improvement
CADs meshed for our validation test
Statistics on our four meshed models
Batch Meshes (with or without Manual Improvement) have : A correct percentage of triangular elements A very good elementary qualityGuillaume Minault 27/08/2007
First Step of our Validation Program (3/6) : Element SizeNumber of Elements
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HM_5mm 5.25mm
4.75mm
Analysis : All fine meshes have a very little dispersion of element sizes Altair Batch Meshes have a symmetric distribution around the element size target Our 5mm Hand Mesh has a great number of elements under the element size target
Element Size Intervals Number of Elements
BM_5mm
Element Size Intervals Number of Elements
BM-MI_5mm
Legend : = Element Size Target
Element Size Intervals
Guillaume Minault
27/08/2007
First Step of our Validation Program (4/6) : To be improved
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5mm Batch Mesh of our sidemember
5mm Batch Mesh of a multi constrained area : Global Mesh Flow versus Hole Representation 5mm Batch Mesh of 3 stiffeners
A better Batch Meshing Repeatability Stronger Mesh Patterns Philosophy ?Guillaume Minault 27/08/2007
An improved algorithm for multiconstrained areas
First Step of our Validation Program (5/6) : ResultsHM_12mmNon Physical Behaviour
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HM_5mm Radioss Computation
Good representation of buckling
Good representation of buckling
BM_5mm
BM-MI_5mmGuillaume Minault 27/08/2007
Good representation of buckling
50ms
First Step of our Validation Program (6/6) : ResultsForce in Mobil Wall Load Cells (mm)
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Force / Displacement Graph
HM_5mm BM_5mm BM-MI_5mm HM_12mm
Displacement of Sidemember Front Edge (mm)Guillaume Minault
All Batch Meshes lead to a good representation of first buckling peaks 27/08/2007
Batch Meshing for Car Crash Test Simulations Dream or Reality?Introduction Problem Definition & Chosen Approach Analysis & Discussions Batch Meshing Process & Vocabulary Main Conclusions of our Benchmark Presentation of the First Step of our Validation Program Conclusions & Perspectives Acknowledgements
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Guillaume Minault
27/08/2007
Conclusions On the first step of our Validation Program, the 5mm Batch Meshing leads to :A substantial gain of meshing time A very good elementary quality A very little element size dispersion A symmetric distribution of element sizes around the targeted size A correct orthogonality due to an efficient manual pre-processing A good geometric representation of buckling An accurate computation of the first buckling force peaks
Conclusions & Perspectives
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So, we validate the use of 5mm Batch Meshing on this first step. We also found several points to be improved such as:Batch Meshing Repeatability (Mesh Patterns) Batch Meshing of multi-constrained areas (preserving orthogonality)
Perspectives At present, due to these first encouraging results, we are proceeding with our Validation Program in order to make in 2008 :
Guillaume Minault
27/08/2007
Conclusions On the first step of our Validation Program, the 5mm Batch Meshing leads to :A substantial gain of meshing time A very good elementary quality A very little element size dispersion A symmetric distribution of element sizes around the targeted size A correct orthogonality due to an efficient manual pre-processing A good geometric representation of buckling An accurate computation of the first buckling force peaks
Conclusions & Perspectives
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So, we validate the use of 5mm Batch Meshing on this first step. We also found several points to be improved such as:Batch Meshing Repeatability (Mesh Patterns) Batch Meshing of multi-constrained areas (preserving orthogonality)
Perspectives At present, due to these first encouraging results, we are proceeding with our Validation Program in order to make in 2008 :
our dream of Batch Meshing for Car Crash Test Simulations a realityGuillaume Minault 27/08/2007
AcknowledgementsI would like to thank all the people from ALTAIR who worked on this project. In particular: Stephano Deiana, Mauro Guglielminotti and Arnaud Stauffer.
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Many thanks to the other editors teams who performed our Benchmark.
Many thanks also to all my PSA colleagues who are also working on this topics.
Finally, very special thanks to Jrme Thibaut (from ALTAIR) for his strong involvement both on our Benchmark and our Validation Program.
Guillaume Minault
27/08/2007
