dagmar links behr gmbh & co, stuttgart, germany … of parts and components starting in concept...

FENET THEMATIC NETWORKCOMPETITIVE AND SUSTAINABLE GROWTH(GROWTH) PROGRAMME

Lack of material data for FEA from an automotive suppliers point of view

Dagmar Links

BEHR GmbH & Co, Stuttgart, Germany

Summary:Questions of material data (aluminum, plastics) for thin walled cooling and climarisation parts

Industry Sector RTD Thematic Area DateLand Transport Education and Dissemination 14.06.02

Introduction of BEHR GmbH & Co

Use of FEA in the company

Overwiev: parts simulated with FEA

Material data aluminum

Material data plastics

BEHR GmbHOne of the leading original equipment manufacturers

Subsidiaries andaffiliated companies

Licensees

Czech Republic

South Africa

SpainUSA

Brazil

Sweden

GermanyFrance

MalaysiaThailand

South Korea

• Vehicle air conditioning

• Engine cooling

• Passenger cars, commercial vehicles

General contractor for thermal management Integration levels from component supply to system partner

Cockpit Module

Front-end Module Complete VehicleThermal Manage-ment System

CompleteA/C System

Complete EngineCooling System

A/C Unit

Cooling Module

Components

InstallationIntegration

Physical Integration

Concept Design Development

FEA and associated software in BEHR development cycleOptimization of parts and components starting in concept phase

FE model(Concept)

Geometry model(Design)

FE model(detailed)

Geometry model(detailed)

Dimensioning Optimization Check up Simulation

Model BuildingFeasability studies

FEA and associated software in BEHR development cycle

PERMAS (since 1988)

• linear statics

• contact analysis

• eigenvalues

• frequency response

• time history

• optimization

• heat transfer

• non linear material

MEDINA (since 1994)

• Pre- und Postprocessing

LMS Gateway (since 1998)

• correlation with modal analysis tests

• pre test, generation of test model

• sensitivities

LMS FALANCS (since 2000)

• fatigue analysis

Interfaces

• CATIA (direct)

• VDAFS, IGES, STEP,...

• UNIVERSAL (ASCII standard for FEM data)

• NASTRAN (interface FEM/EMA)

BEHR parts and assembliesFEA simulation with PERMAS

FEA of BEHR parts and assembliesTechnical barriers

• Light weight and thin walled structures

• Different materials: steel, aluminum, fiber reinforced plastic

• Different parts fit together in complex fabrication processes

• Different material suppliers from all over the world

• Wide range of temperature

• Local failure of parts depends from global component behaviour

• Material data depend on fabrication process

Target is prediction of failure

Urgent need of various material data, standard data and test correlated from parts

Aluminum

Description of parts

Questions of material data

Aluminum: Cooling liquid coolers and charge air coolersDescription of parts

• Aluminum core(tubes and fins), header, Plastic tank

• Header is crimped corrugating along the bumps• Tank foot with bumps on the outside

Crimp Cutout

Bump Header Bead

Tank Foot

Aluminun: Charge air coolerTypical failure in the header bead under pulsating internal pressure and temperature

Stress peakin header bead

Crackstarting

Aluminum: Header/tube connections of coolersExamples for stress and strain peaks

Bending of tubes:Stress peak in brazed material

Plastic strain in tube under internal pressure

AluminumSummary of material questions

• Temperature dependent material data needed

• Difference between data from material as delivered and brazed

• Youngth Modulus from cheap tension tests is not ok

• Is there a reliable correlation between material as delivered and brazed?

• Wide scatter of all data, sensitivities

• Combination of yield curve + E-Modulus from different test sources ?

• Durability behaviour under temperature

PERMAS and others

• Reliable measurements on tube material with thickness < 2 mm is not possible, we have thickness of 0.35 mm

Material data aluminumHigh scatter of yield and failure

Material data aluminumExamples for behaviour under temperature

Material data aluminumExamples for difference of delivered and brazed material

Material data aluminumDetermination of Youngth Modulus by standard tension tests is not possible

Tension Test

Strain [ % ]

ss [ M

Material data aluminumDynamic determination of youngth modulus needed

Material data aluminumValidity of theory doubtful

• Derive E-modulus and yield curve from different testfor input of non linear analysis ?

• Derive yield curve of aluminumunder higher temperature ?

• Correlation of logarithmic (true) strain and true(Cauchy)stressvalid ?

Material data aluminumDurability behaviour under temperature

time t

fatigue

√ aìê~Äáäáíó=íÜÉçêó=Åçìåíë=äç~Ç=ÅóÅäÉëI=åçí=íáãÉ

√ lh=Ñçê=OPç`I=Äìí=åçí=Ñçê=ÜáÖÜÉê=íÉãéÉê~íìêÉ

√ qÉãéÉê~íìêÉ=ÇÉéÉåÇÉåí=ÅêÉÉé=ÉÑÑÉÅíë=ìåâåçïå

Plastics

Description of parts

Questions of material data

Plastics: Cooling module Deformation of parts under internal pressure

Plastics: Housings of climatisation unitsDynamic analysis

PlasticsSummary of material questions

• Environment dependent material data needed

• Difference between supplieres ideal data and parts

• Material data dependent from fabrication

• Overlapping of different dependencies ?

• Durability behaviour ?

• Wide scatter of all dataPERMAS RA

and others

• Damping effects ?

• Material data dependent from load

Material data plasticsBehaviour under temperature and humidity

räíê~ãáÇ íóéÉ Ñçê Ñ~åëW=jçÇìäìë=çÑ=Éä~ëíáÅáíóÇÉéÉåÇÉåí=Ñêçã=íÉãéÉê~íìêÉ ~åÇ=ÜìãáÇáíó

aêó=========

NKO=B=ÜìãáÇáíó

OKP=B=ÜìãáÇáíó

Material data plasticsExample for behaviour under temperature and humidity

Material data plasticsExample for difference between ideal and real life data

• Test samples taken from expansion tank

• Material supplieres data taken from ideal DIN test samples are always much better

• Safe excess charges are needed

Ideal DIN sample

Material data plasticsMaterial data depending from load

• Correlation of FEA modal analysis and modal analysis test with hammer

• Good MAC for important global modes

• Natural frequencies differ about 30 %

• Reason: dynamic youngth modulus

Material data plasticsExample for strain rate dependent material (example PP TV)

2) 50 mm/min

1) 5 mm/min

3) Trend(Excel)

1. E = 2500 Mpa2. E = 2900 Mpa3. E = 5300 Mpa

Material data plasticsExample for strain rate dependent material (example PP)

Material data plasticsMaterial data dependent from injection molding process

• Stiffness depends from flow direction

• Only 30 % of tensile strength in real life weldlines

• Correct would be molding simulation before FE simulation

Weld line at end of flow process

Weld line during flow process

Material data plasticsWhat is durability ?

• DIN standard for fatigue tests does not exist (in Germany)

• Overlap with creep, even at ambient temperature ?• Looking at interesting number of load cycles plastic won‘t really break !• Result of alternating load will always change during test !

Material data plasticsDamping influenced by temperature

Material data plasticsExample for dependencies

Frequency

Friction

Damping

Amplitude

Strain rate

Stiffness

Temperatature

Humidity

Time, creep

Stainless steel

Is the problem solved ?

Stainless steelSummary of fatigue information from different sources

Lack of material dataBarrier for uptake of FEA

FEA analysis in industry is service - ‚not possible‘ is impossible !

Analyses with inexact input are done !FEA results and reality may differ !Precise statement ‚Work/Does not work‘ is not possible resp. a lie !Parts sometimes are oversized or fail ! FEA is comparison only, not prediction ! Loss of confidence in FEA !

High financial efforts in gaining data needed for Input of FEAEvaluation of results

Time and people needed to Get material dataDo (long time) test correlation

FEA engineers have to be allround experts !

Thank you!

dagmar links behr gmbh & co, stuttgart, germany … of parts and components starting in concept...

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