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

Transcription

1 Industry Sector RTD Thematic Area Date Land Transport Education and Dissemination 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

2 Introduction of BEHR GmbH & Co Use of FEA in the company Overwiev: parts simulated with FEA Material data aluminum Material data plastics

3 BEHR GmbH One of the leading original equipment manufacturers Passenger cars, commercial vehicles Engine cooling Vehicle air conditioning Sweden Subsidiaries and affiliated companies Licensees France Czech Republic Germany USA Spain Italy Egypt South Korea Japan India Thailand Malaysia Brazil South Africa

4 General contractor for thermal management Integration levels from component supply to system partner Installation Integration Cockpit Module A/C Unit Cooling Module Front-end Module Complete A/C System Complete Engine Cooling System Complete Vehicle Thermal Management System Components Physical Integration

5 FEA and associated software in BEHR development cycle Optimization of parts and components starting in concept phase FE model (Concept) FE model (detailed) FEA Model Building Feasability studies Dimensioning Optimization Check up Simulation Geometry model (Design) Geometry model (detailed) CAD Concept Design Development

6 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)

7 BEHR parts and assemblies FEA simulation with PERMAS

8 FEA of BEHR parts and assemblies Technical barriers Light weight and thin walled structures Different parts fit together in complex fabrication processes Local failure of parts depends from global component behaviour Different materials: steel, aluminum, fiber reinforced plastic Wide range of temperature Different material suppliers from all over the world Material data depend on fabrication process Target is prediction of failure Urgent need of various material data, standard data and test correlated from parts

9 Aluminum Description of parts Questions of material data

10 Aluminum: Cooling liquid coolers and charge air coolers Description of parts Aluminum core(tubes and fins), header, Plastic tank Tank foot with bumps on the outside Header is crimped corrugating along the bumps Rib Tank Foot Bump Header Bead Crimp Cutout

11 Aluminun: Charge air cooler Typical failure in the header bead under pulsating internal pressure and temperature Crack starting Stress peak in header bead

12 Aluminum: Header/tube connections of coolers Examples for stress and strain peaks Bending of tubes: Stress peak in brazed material Plastic strain in tube under internal pressure

13 Aluminum Summary 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 Wide scatter of all data, sensitivities PERMAS and others Reliable measurements on tube material with thickness < 2 mm is not possible, we have thickness of 0.35 mm Is there a reliable correlation between material as delivered and brazed? Combination of yield curve + E-Modulus from different test sources? Durability behaviour under temperature

14 Material data aluminum High scatter of yield and failure

15 Material data aluminum Examples for behaviour under temperature

16 Material data aluminum Examples for difference of delivered and brazed material

17 Material data aluminum Determination of Youngth Modulus by standard tension tests is not possible Stress [ MPa ] Tension Test Strain [ % ]

18 Material data aluminum Dynamic determination of youngth modulus needed

19 Material data aluminum Validity of theory doubtful Derive yield curve of aluminum under higher temperature? Correlation of logarithmic (true) strain and true(cauchy)stress valid? Derive E-modulus and yield curve from different test for input of non linear analysis?

20 Material data aluminum Durability behaviour under temperature operation pressure p max p min creep fatigue time t aìê~äáäáíó=íüéçêó=åçìåíë=äç~ç=åóåäéëi=åçí=íáãé lh=ñçê=op ç`i=äìí=åçí=ñçê=üáöüéê=íéãééê~íìêé qéãééê~íìêé=çéééåçéåí=åêééé=éññéåíë=ìåâåçïå

21 Plastics Description of parts Questions of material data

22 Plastics: Cooling module Deformation of parts under internal pressure

23 Plastics: Housings of climatisation units Dynamic analysis

24 Plastics Summary of material questions Environment dependent material data needed Difference between supplieres ideal data and parts Material data dependent from fabrication Material data dependent from load Wide scatter of all data PERMAS RA and others Damping effects? Durability behaviour? Overlapping of different dependencies?

25 Material data plastics Behaviour under temperature and humidity räíê~ãáç íóéé Ñçê Ñ~åëW=jçÇìäìë=çÑ=Éä~ëíáÅáíó ÇÉéÉåÇÉåí=Ñêçã=íÉãéÉê~íìêÉ ~åç=üìãáçáíó aêó========= NKO=B=ÜìãáÇáíó OKP=B=ÜìãáÇáíó

26 Material data plastics Example for behaviour under temperature and humidity

27 Material data plastics Example for difference between ideal and real life data Ideal DIN sample Test samples taken from expansion tank Material supplieres data taken from ideal DIN test samples are always much better Safe excess charges are needed

28 Material data plastics Material 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

29 Material data plastics Example for strain rate dependent material (example PP TV) 3) Trend(Excel) 2) 50 mm/min 1) 5 mm/min 1. E = 2500 Mpa 2. E = 2900 Mpa 3. E = 5300 Mpa

30 Material data plastics Example for strain rate dependent material (example PP)

31 Material data plastics Material data dependent from injection molding process Weld line during flow process Weld line at end of flow process Stiffness depends from flow direction Only 30 % of tensile strength in real life weldlines Correct would be molding simulation before FE simulation

32 Material data plastics What is durability? DIN standard for fatigue tests does not exist (in Germany) Result of alternating load will always change during test! Looking at interesting number of load cycles plastic won t really break! Overlap with creep, even at ambient temperature?

33 Material data plastics Damping influenced by temperature

34 Material data plastics Example for dependencies Humidity Damping Temperatature Amplitude Strain rate Friction Stiffness Frequency Time, creep

35 Stainless steel Is the problem solved?

36 Stainless steel Summary of fatigue information from different sources

37 Lack of material data Barrier 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 FEA Evaluation of results Time and people needed to Get material data Do (long time) test correlation FEA engineers have to be allround experts!

38 Thank you!