technology advances for crashwothiness analysis

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Technology Advances in ABAQUS forCrashworthiness and Occupant Safety

HP CAE Symposium

April 3, 2007

Marc Schrank

[email protected]


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Copyright 2007 ABAQUS, Inc.

Outline

Company update

Crashworthiness update

Technology advances

BioRID dummy

Fastener modeling and calibration

Barriers

Summary


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Company Update


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HQ in Providence, RI

Staff from DS simulation group inFrance, now part of SIMULIA /

ABAQUS

Over 550 people, more than 430technical staff

Worldwide presence 28 offices and9 representatives

35% Americas*

39% Europe*

26% Asia* *2004 revenue

Consistent, long-term growth,$100M+ revenue in 2005

ABAQUS Revenue

SIMULIA and ABAQUS, Inc.


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Dassault Systmes Strategy

DS strategy is to achievedemocratization of a life-like 3Dvirtual experience

Simulation is a key step alongthe way which drove theacquisition of ABAQUS


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SIMULIA: t h e V i s io n

to collaborative scientific process

based on anopen integrated multi-physics

simulation platform

An open multi-physics platform forscientific simulation

A unified approach to what todaycan be a fragmented landscape of

non-interoperable solutions inmultiple simulation domains


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SIMULIA Ecosystem

The broadest community ofsimulation partners in the industry focus on delivering completesolutions to customers


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Crashworthiness and Occupant SafetyUpdate

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Strategic Focus

SIMULIA / ABAQUS strategic objective to develop strong leadership

position in Automotive industry

Already substantial presence in certain areas

Tires

Powertrain

Severe load durability

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Strategic Focus

Strong leadership position in Automotive can only be attained with

adoption for major full vehicle applications

Crashworthiness represents probably the largest ful l vehicle structuralsimulation application (cpu cycles)

Similar initiatives underway for NVH and System Level Durabili ty

Seeking to leverage full range of capabil ities in both implicit and explicitFEA technology

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Automotive Unified FEA Fundamental Concepts

Performance AttributesSupporting the full range of simulation procedurestypes required for product validation

NVHCrash

System-Level Integrity

Ride & Handling

Multi-Disciplinary Optimization

Providing optimization for mult ipleperformance attributes simultaneously

Simulation chains and couplings

Engineeringtargets

Simulation executionand automated

workflow managementDecision

Managed AssembliesCreating the right performance attribute model from

the product assembly in a managed environment

Body

Spotwelds Tires

Suspension

Chassis

Powertrain

Multiple Abstractions/Target Cascade

Supporting multiple part representationsand intelligently connecting s imulation dataacross all product granularity

P0

Part

Substructure

Mesh

BRep

Lumped Submodel

Calibrate

Lumpedmodel

Systemresponse

[K]

Unified FEA

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BMW Partnership

Early focus on component level crashworthiness (1999-)

Crushable foam material development

Free motion headform impact (FMVSS 201)

Formal partnership init iated in mid 2001

Aggressive milestones established

Continued strong partnership with BMW underway for 5 years

In-depth, open technical exchanges

Weekly teleconferences (200+ and counting)

Management briefings

Status/update meetings (~2-3 per year)

ABAQUS delivering for BMW according to established schedule

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BMW Partnership

Commitment to migrating to ABAQUS for Crashworthiness (Oct. 2005)

Exclusive usage in major new vehicle program for 2+ years

All relevant full vehicle load cases successfully simulated

In process of converting all other vehicle programs


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Technology Advances

BioRID Dummy Model

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BioRID Dummy

Neck injuries are most common seriousinjury reported in automobile crashes

Account for more than $8.5 billion each year 25% of all auto insurance claims (IIHS)

Occur most commonly in rear impactcollisions

BioRID-II dummy intended to providebiofidelic response for low speed rear impactevents, to aid in developing effective headand neck restraints.

Based on Hybrid-III dummy

More sophisticated in its spinal construction

Articulated thoracic/lumbar spine

BioRID dummy (Photo courtesyof IIHS)

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http://a332.g.akamai.net/f/332/936/12h/www.edmunds.com/media/ownership/safety/crash.test.on.suvs.and.pickups/dummy.seat.500.jpg


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BioRID Dummy

Vertebra simulators (24, same as human body)allow more natural seating posture, and to simulateneck movement observed in rear-end collisions.

Cervical (C1-C7), Thoracic (T1-T12), Lumbar (L1-L5) vertebrae

Neck muscle substitutes (tensioning cables)represent the posterior and anterior muscles in the

human neck

BioRID-IIc Rear Impact Crash Test Dummy

James R. (Randy) Kelly, Robert A. Denton, Inc.


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ABAQUS BioRID Model

Most critical portion of the BioRIDdummy is the fully articulated spineassembly

ABAQUS BioRID model uses state-of-the-art ABAQUS technology thatincludes extensive use of connectorelements

Cables, damper mechanism,vertebrae pins, joints, load cells,accelerometers, and variousmeasuring devices

Over 200 connectors in the model Connector elements first available in

ABAQUS Version 6.1

Enhanced and expanded in eachsubsequent ABAQUS release

ABAQUS BioRID neck/spine model

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HP CAE SymposiumCopyright 2007 ABAQUS, Inc.

ABAQUS Connectors

AssembledEquivalent basic connection components

(translational + rotational)

JOIN

PROJECTIONCARTESIAN

JOIN

SLOT

JOIN

SLIDE-PLANE

SLOT

JOIN

JOIN

BEAM ALIGN

BUSHINGPROJECTIONFLEXION-TORSION

CVJOINT CONSTANT VELOCITY

CYLINDRICAL REVOLUTE

HINGE REVOLUTE

PLANAR REVOLUTE

TRANSLATOR ALIGN

UJOINT UNIVERSAL

WELD ALIGN

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ABAQUS BioRID Model: Cable Mechanisms

SLIPRING muscle substitute cables

New SLIPRING and FLOW-CONVERTERconnector elements used to model themuscle substitute and damper cables

SLIPRING enables modeling of materialflow (in this case a flow of cables throughrigid vertebrae)

FLOW-CONVERTER enables conversionof material flow into a rotation (in this casea cable flow is converted into a drumrotation modeled with HINGE connector)

Connectors provide for very efficientmeans to capture desired mechanismbehavior

SLIPRING damper cable

FLOW-CONVERTER cable to damper mechanism

Video Clip

HINGE damper mechanism

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ABAQUS BioRID Model: Instrumentation

ABAQUS connector elements being employedextensively to model the instrumentation in theBioRID dummy

BioRID Accelerometers

Upper neck load cell

Lower neck load cell BioRID instrumentation: imagefrom Denton

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ABAQUS BioRID Model: Joints

Connector elements used widely to model BioRID joints

Hinge connections: shoulder yoke, shoulder joint, elbowjoint, knee joint

Ball-in-socket connections: hip joint, ankle joint Joint friction produces effect on dummy response

Dummy joints calibrated efficiently in ABAQUS/Standard

steel

delrin

HINGEconnector

Elbow joint calibration

ABAQUS BioRID joints

Shoulder joint calibration

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ABAQUS BioRID Model: Full Dummy Validation

ABAQUS BioRID-II Chalmers seat validation

Universal Chalmers seat employed to evaluatethe response of the full BioRID dummy for threedifferent pulses

ABAQUS BioRID model in Chalmers seat

Video Clip

Image from DSD Linz

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ABAQUS BioRID Model: Low severity pulse

Head x-acceleration

ABAQUS

EXPERIMENTAL

Head z-acceleration


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Technology Advances

Fastener Modeling and Calibration

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Fastener Modeling

Modern automobiles can include severalthousand spotwelds, as well as other pointfasteners, such as rivets

Finite element modeling of spotwelds and

other point fasteners must be user-friendly Mesh independence is essential

In a crash event, these point fasteners canfail, thus having an effect on the subsequent

structural response during the event Constitutive model for the fastener must be

able to accurately account for this behavior

Damage and failure response can be

complex

www.kuka.com

Video Clip

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http://en.wikipedia.org/wiki/Image:KUKA_robots_in_car_production.jpg


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Fasteners and Calibration

ABAQUS provides a fastenermodeling capabil ity that cancapture experimentallyobserved behavior

Accurate calibration is thekey to success

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Fasteners in ABAQUS consist of a connectorelement and two distributing couplings

The entire connector element library isavailable

Virtually any imaginable type of fastener can bemodeled

All connector constitutive behaviors areavailable

Elasticity, rigid plasticity, progressive damagewith failure, many others. . .

Distributing couplings smear the connectionacross a region of the mesh

Provides mesh independence

Connector

End point ofthe connector

Radius ofinfluence

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Self-piercing rivet calibration

Experimental tests show that thebehavior of the rivet:

Elastic-plastic with hardening beforethe peak force is reached

Plastic with damage after the peakforce until ultimate failure.

Dependent on the loading direction This behavior can be described well

with fasteners in ABAQUS.

Elastic-plastic

Plasticity + Damage

Modeling of Self-Piercing Rivets Using Fasteners in Crash Analysis,

S. Weyer, et. al. (BMW, ABAQUS Deutschland), ABAQUS UsersConference, 2006.

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Self-piercing rivet calibration

Comparison of simulation results with test results for a sheet pair

045

90

15

60

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Virtual spotweld calibration

Constitutive model sophistication can lead to extensive calibrationrequirements

Numerous material, thickness, loading direction combinations Full experimental testing can be prohibitively expensive

Virtual calibration using detailed continuum models provides analternative


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Technology Advances

Deformable Barrier Models

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Deformable barriers are a key component of vehicle crashworthinessassessments

Various loadcases: offset frontal, side impact, compatibility,

Several different barriers used in various legislation

Accurate barrier representation is needed to obtain accurate crashsimulation results

Weakest link in the chain (barrier, vehicle, dummy,) will limit the

solution accuracy

NHTSA barrier IIHS barrier

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BMW and ABAQUS entering into formal agreement for jointdevelopment of improved barrier models

Intent to develop accurate, efficient, robust models to be made generallyavailable to ABAQUS customer base

Preliminary development schedule (2007-2008)

IIHS (IIHS side)

AEMDB version 3.9

NHTSA (LINCAP, FMVSS214 new, FMVSS 301)

EEVC (EuroNCAP front) TRL or PDB (compatibility)

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Physical testing program

Good simulation model will accurately predict the force history anddistribution exerted by the barrier onto the car.

What are primary deformation mechanisms associated with thisforce?

Important for physical tests to replicate the relevant deformationmechanisms that occur when vehicle impacts the barrier

Test design:(1) Two test series per barrier(2) Each test series consists of three equal tests

(3) Triggers relevant deformation mechanisms that are importantin car crashes.

Car crash examples shown on following slides

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Relevant Deformation Mechanisms:


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IIHS barrier deformation kinematics

tearing of cladding

B-pillar imprint

imprint of mirror

Bumper intrusioninto mainblock

Rotationof bumper

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Relevant Deformation Mechanisms:


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Honeycomb deformations

cut

Honeycomb deformation critical to forcelevel.

Due to fine structure of folding systems,

substitute model required

38Relevant Deformation Mechanisms:


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Tearing of cladding sheet

IIHS barrierPDB barrier

Tearing of cladding sheet may reducemembrane stresses and subsequentresistance against local intrusion into the

main block.

Important influence on force exertedby barrier onto car structure.

NHTSA barrier

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Test Design: Example of inferior test design

Common test with IIHS barrier

Barrier against plane wall. Bumper does not rotate (like in car crashes). Tearing

of the top cladding does not occur in IIHS car crash tests.

Deformation not representative of car crashes.

Better approach: deformation mechanism-based test design.

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Test Design: Example of good test design

Test on IIHS barrier.

Ram exerts force on lower half of the bumper of IIHS barrier

Causes bumper to intrude into main block and rotate

Representative of deformation mode observed in car crashes

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Modeling Approach: Honeycomb construction

Fine honeycomb construction cannotbe exactly replicated from a modelingperspective

Prohibitive computational coast

Classical continuum or solid element-

based approach

Smears complex behavior intooverall stress-strain relations

Crash event shearing deformationmechanisms not sufficientlyrepresented

19

mm

(eevc,soll)

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Modeling Approach: Honeycomb construction

2-3x larger cell

size

New approach using shell elements

Honeycomb cells magnified by afactor of 2-3

Two elements per honeycomb edge One free node that allows for

buckling deformation

Collapse load calibrated by tests

Prototypted by BMW

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M d li A h F il d li


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Modeling Approach: Failure modeling

Multiple mechanism damage and failure modeling

* A phenomenological failure model for sheet metals and extrusions, H. Werner, et al. (BMW), Annual Review

Meeting and Workshop, Impact and Crashworthiness Laboratory, MIT, USA, Oct 7-8, 2004.

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D f bl B i M d l D l t


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Deformable Barrier Models: Development program

Test Institute

Conducts physical tests

Develops simulationtechnology

Creates simulation models Calibrates models against

test data

Specifies tests Specifies barrier model

requirements

Manages & coordinates Contributes crash

experience Validates models as

applicable to cardevelopment process

External EngineeringService Suppliers

Designs and assembles impactors Carries out simulations for test

preparations

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Deformable Barrier Models: End goal


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Deformable Barrier Models: End goal

Video Clip


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Summary

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Summary


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Summary

Dassault Systmes ongoing strategy to democratize life-like 3D virtualexperience

Realistic simulation is key aspect of that strategy

SIMULIA vision to provide an open multi-physics platform for scientific simulation

Partnership with BMW has played key role in developing ABAQUScrashworthiness simulation capabilities

Mutual objectives to continually improve accuracy and robustness, makingcrashworthiness simulation more predictive

Barrier models represent latest endeavor

ABAQUS technology being leveraged throughout crashworthiness functionality.Examples include:

BioRID dummy model

Connector elements efficient and accurate

Point fasteners spotwelds, rivets,

Sophisticated connector constitutive options to capture complex damage

and failure behavior

technology advances for crashwothiness analysis

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