Technology Advances for Crashwothiness Analysis

Technology Advances in ABAQUS for Crashworthiness and Occupant Safety HP CAE Symposium April 3, 2007 Marc Schrank [email protected]

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Outline • Company update • Crashworthiness update • Technology advances • BioRID dummy • Fastener modeling and calibration • Barriers • Summary

HP CAE Symposium Copyright 2007 ABAQUS, Inc.

Company Update

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SIMULIA and ABAQUS, Inc. • HQ in Providence, RI • Staff from DS simulation group in France, now part of SIMULIA / ABAQUS • Over 550 people, more than 430 technical staff • Worldwide presence – 28 offices and 9 representatives • 35% Americas* • 39% Europe* • 26% Asia*

*2004 revenue

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

ABAQUS Revenue HP CAE Symposium Copyright 2007 ABAQUS, Inc.

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Dassault Systèmes Strategy • DS strategy is to achieve democratization of a life-like 3D virtual experience • Simulation is a key step along the way which drove the acquisition of ABAQUS


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SIMULIA: the Vision •

An open multi-physics platform for scientific simulation

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A unified approach to what today can be a fragmented landscape of non-interoperable solutions in multiple simulation domains

… to collaborative scientific process based on an open integrated multi-physics simulation platform


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SIMULIA Ecosystem • The broadest community of simulation partners in the industry – focus on delivering complete solutions to customers


Crashworthiness and Occupant Safety Update

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Strategic Focus SIMULIA / ABAQUS strategic objective to develop strong leadership position in Automotive industry • Already substantial presence in certain areas • Powertrain • Tires

• “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 full vehicle structural simulation application (cpu cycles) • Similar initiatives underway for NVH and System Level Durability • Seeking to leverage full range of capabilities in both implicit and explicit FEA technology


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Automotive Unified FEA – Fundamental Concepts Managed Assemblies

Performance Attributes

Creating the right performance attribute model from the product assembly in a managed environment

Supporting the full range of simulation procedures types required for product validation

Body Powertrain Crash

NVH

Chassis Ride & Handling

Suspension Spotwelds

System-Level Integrity

Multi-Disciplinary Optimization

Multiple Abstractions/Target Cascade Supporting multiple part representations and intelligently connecting simulation data across all product granularity

Unified FEA Lumped model

P0

Engineering targets

Providing optimization for multiple performance attributes simultaneously Simulation execution and automated workflow management

Part System response

BRep

Calibrate

Mesh Substructure

[K]

HP CAE Symposium Lumped Copyright 2007 ABAQUS, Inc.

Submodel

Tires

Simulation chains and couplings

Decision

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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 initiated in mid 2001 • Aggressive milestones established • Continued strong partnership with BMW underway for 5½ 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 HP CAE Symposium Copyright 2007 ABAQUS, Inc.

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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 HP CAE Symposium Copyright 2007 ABAQUS, Inc.

Technology Advances BioRID Dummy Model

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BioRID Dummy • Neck injuries are most common serious injury 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 impact collisions

• BioRID-II dummy intended to provide biofidelic response for low speed rear impact events, to aid in developing effective head and neck restraints. • Based on Hybrid-III dummy • More sophisticated in its spinal construction • Articulated thoracic/lumbar spine


BioRID dummy (Photo courtesy of IIHS)

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BioRID Dummy • Vertebra simulators (24, same as human body) allow more natural seating posture, and to simulate neck movement observed in rear-end collisions. • Cervical (C1-C7), Thoracic (T1-T12), Lumbar (L1L5) 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. HP CAE Symposium Copyright 2007 ABAQUS, Inc.

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ABAQUS BioRID Model • Model developed by ABAQUS in cooperation with German Association for Research in Automobile Technology FAT (“the BioRID working group”) • Group members include: BMW, Audi, VW, DaimlerChrysler, Porsche, Keiper, JCI, CRH, Karmann

BioRID dummy (Image courtesy of DSD Linz) HP CAE Symposium Copyright 2007 ABAQUS, Inc.

ABAQUS BioRID-II

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ABAQUS BioRID Model • Most critical portion of the BioRID dummy is the fully articulated spine assembly • ABAQUS BioRID model uses state-ofthe-art ABAQUS technology that includes extensive use of connector elements • Cables, damper mechanism, vertebrae pins, joints, load cells, accelerometers, and various measuring devices • Over 200 connectors in the model • Connector elements first available in ABAQUS Version 6.1 • Enhanced and expanded in each subsequent ABAQUS release HP CAE Symposium Copyright 2007 ABAQUS, Inc.

ABAQUS BioRID neck/spine model

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ABAQUS Connectors

Assembled

Equivalent basic connection components (translational + rotational)

BEAM

JOIN

ALIGN

BUSHING

PROJECTION CARTESIAN

PROJECTION FLEXION-TORSION

CVJOINT

JOIN

CONSTANT VELOCITY

CYLINDRICAL

SLOT

REVOLUTE

HINGE

JOIN

REVOLUTE

PLANAR

SLIDE-PLANE

REVOLUTE

TRANSLATOR

SLOT

ALIGN

UJOINT

JOIN

UNIVERSAL

WELD

JOIN

ALIGN


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ABAQUS BioRID Model: Cable Mechanisms SLIPRING muscle substitute cables SLIPRING damper cable

• New SLIPRING and FLOW-CONVERTER connector elements used to model the muscle substitute and damper cables • SLIPRING enables modeling of material flow (in this case a flow of cables through rigid vertebrae)

Video Clip

• FLOW-CONVERTER enables conversion of material flow into a rotation (in this case a cable flow is converted into a drum rotation modeled with HINGE connector)

• Connectors provide for very efficient means to capture desired mechanism behavior FLOW-CONVERTER cable to damper mechanism HINGE damper mechanism HP CAE Symposium Copyright 2007 ABAQUS, Inc.

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ABAQUS BioRID Model: Instrumentation • ABAQUS connector elements being employed extensively to model the instrumentation in the BioRID dummy

Upper neck load cell

BioRID Accelerometers


Lower neck load cell

BioRID instrumentation: image from Denton

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ABAQUS BioRID Model: Joints • Connector elements used widely to model BioRID joints • Hinge connections: shoulder yoke, shoulder joint, elbow joint, knee joint • Ball-in-socket connections: hip joint, ankle joint • Joint friction – produces effect on dummy response • Dummy joints calibrated efficiently in ABAQUS/Standard

delrin

steel

HINGE connector

Shoulder joint calibration HP CAE Symposium Copyright 2007 ABAQUS, Inc.

ABAQUS BioRID joints Elbow joint calibration

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ABAQUS BioRID Model: Full Dummy Validation • ABAQUS BioRID-II Chalmers seat validation • Universal Chalmers seat employed to evaluate the response of the full BioRID dummy for three different pulses

Video Clip

Image from DSD Linz

ABAQUS BioRID model in Chalmers seat HP CAE Symposium Copyright 2007 ABAQUS, Inc.

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ABAQUS BioRID Model: Low severity pulse

Head x-acceleration

Head z-acceleration

ABAQUS EXPERIMENTAL HP CAE Symposium Copyright 2007 ABAQUS, Inc.

Technology Advances Fastener Modeling and Calibration

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Fastener Modeling • Modern automobiles can include several thousand spotwelds, as well as other “point” fasteners, 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 can fail, thus having an effect on the subsequent structural response during the event

www.kuka.com

• Constitutive model for the fastener must be able to accurately account for this behavior • Damage and failure response can be complex HP CAE Symposium Copyright 2007 ABAQUS, Inc.

Video Clip

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Fasteners and Calibration • ABAQUS provides a fastener modeling capability that can capture experimentally observed behavior

• Accurate calibration is the key to success


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Fasteners and Calibration • Fasteners in ABAQUS consist of a connector element and two distributing couplings • The entire connector element library is available • Virtually any imaginable type of fastener can be modeled

Radius of influence Connector

• All connector constitutive behaviors are available • Elasticity, rigid plasticity, progressive damage with failure, many others. . .

• Distributing couplings “smear” the connection across a region of the mesh • Provides mesh independence


End point of the connector

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Fasteners and Calibration • Self-piercing rivet calibration • Experimental tests show that the behavior of the rivet: • Elastic-plastic with hardening before the peak force is reached

Plasticity + Damage

• Plastic with damage after the peak force until ultimate failure. • Dependent on the loading direction

• This behavior can be described well with fasteners in ABAQUS. Elastic-plastic

Modeling of Self-Piercing Rivets Using Fasteners in Crash Analysis, S. Weyer, et. al. (BMW, ABAQUS Deutschland), ABAQUS Users’ Conference, 2006. HP CAE Symposium Copyright 2007 ABAQUS, Inc.

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Fasteners and Calibration • Self-piercing rivet calibration • Comparison of simulation results with test results for a sheet pair 15° 0°

45° 90°


60°

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Fasteners and Calibration • “Virtual” spotweld calibration • Constitutive model sophistication can lead to extensive calibration requirements • Numerous material, thickness, loading direction combinations • Full experimental testing can be prohibitively expensive • Virtual calibration using detailed continuum models provides an alternative


Technology Advances Deformable Barrier Models

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Deformable Barrier Models • Deformable barriers are a key component of vehicle crashworthiness assessments • Various loadcases: offset frontal, side impact, compatibility,… • Several different barriers used in various legislation

NHTSA barrier

IIHS barrier

• Accurate barrier representation is needed to obtain accurate crash simulation results • “Weakest link” in the chain (barrier, vehicle, dummy,…) will limit the solution accuracy HP CAE Symposium Copyright 2007 ABAQUS, Inc.

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Deformable Barrier Models • BMW and ABAQUS entering into formal agreement for joint development of improved barrier models • Intent to develop accurate, efficient, robust models to be made generally available to ABAQUS customer base • Preliminary development schedule (2007-2008)


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IIHS (IIHS side)

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AEMDB version 3.9

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NHTSA (LINCAP, FMVSS214 new, FMVSS 301)

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EEVC (EuroNCAP front)

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TRL or PDB (compatibility)

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Deformable Barrier Models • Physical testing program • Good simulation model will accurately predict the force history and distribution exerted by the barrier onto the car. • What are primary deformation mechanisms associated with this force? • Important for physical tests to replicate the relevant deformation mechanisms 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 important in car crashes. • Car crash examples shown on following slides


36 Relevant Deformation Mechanisms: IIHS barrier deformation kinematics

tearing of cladding

B-pillar imprint

Rotation of bumper


imprint of mirror

Bumper intrusion into mainblock

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cut

Relevant Deformation Mechanisms: Honeycomb deformations

• Honeycomb deformation critical to force level. • Due to fine structure of folding systems, substitute model required HP CAE Symposium Copyright 2007 ABAQUS, Inc.

38 Relevant Deformation Mechanisms: Tearing of cladding sheet

PDB barrier

IIHS barrier

• Tearing of cladding sheet may reduce membrane stresses and subsequent resistance against local intrusion into the main block. • Important influence on force exerted by barrier onto car structure. NHTSA barrier HP CAE Symposium Copyright 2007 ABAQUS, Inc.

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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. HP CAE Symposium Copyright 2007 ABAQUS, Inc.

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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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• Fine honeycomb construction cannot be exactly replicated from a modeling perspective • Prohibitive computational coast

• Classical continuum or solid elementbased approach • Smears complex behavior into overall stress-strain relations • Crash event shearing deformation mechanisms not sufficiently represented


19 mm (eevc, soll)

Modeling Approach: Honeycomb construction

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Modeling Approach: Honeycomb construction • New approach using shell elements • Honeycomb cells magnified by a factor of 2-3 • Two elements per honeycomb edge • One free node that allows for buckling deformation • Collapse load calibrated by tests • Prototypted by BMW


2-3x larger cell size

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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. HP CAE Symposium Copyright 2007 ABAQUS, Inc.

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Deformable Barrier Models: Development program

Test Institute • Conducts physical tests

External Engineering Service Suppliers • Designs and assembles impactors • Carries out simulations for test preparations


•Specifies tests • Specifies barrier model requirements • Manages & coordinates • Contributes crash experience • Validates models as applicable to car development process

•Develops simulation technology •Creates simulation models • Calibrates models against test data

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Deformable Barrier Models: End goal

Video Clip


Summary

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Summary • Dassault Systèmes ongoing strategy to democratize life-like 3D virtual experience • 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 ABAQUS crashworthiness simulation capabilities • Mutual objectives to continually improve accuracy and robustness, making crashworthiness 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 HP CAE Symposium Copyright 2007 ABAQUS, Inc.

Technology Advances for Crashwothiness Analysis

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