fracture mechanical approach for fatigue of adhesive...

Automation Simulation World Congress, October 29 – 30, 2013

Fracture Mechanical Approach for Fatigue of

Adhesive Joints

Dr.-Ing. Stephan Vervoort

Hottinger Baldwin Messtechnik GmbH

Agenda

1. Background/Motivation

2. Analysis Process

3. FEM Guidelines

4. Adhesive Joints Calculation Method

5. Example

6. Correlation

7. Acknowledgements

2 Automation Simulation World Congress, October 29 – 30, 2013

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• Increased use of adhesive joints in automotive engineering:

• 15 kg adhesives in average car

• Adhesive joining technique build base for material substitution

(sheet metals -> composites)

• Lightweight design

• Examples of automotive engineering:

• Audi A6: Bond seam approx. 90 m

• Daimler A-Class: Bond seam approx. 120 m

• BMW 7-Series: Bond seam approx. 150 m

Background/Motivation


Bond seams of Audi TT

Source: http://wiki.zimt.uni-siegen.de

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• Example: Adhesive joints in automotive engineering


Source: www.volkswagen-forum.com


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• Advantages

• Nondestructive joining technology

• Constant stress distribution across adherent

• Elastic characteristic (cold-heat equalization)

• Damping characteristic during crash

• Disadvantages

• Long-term set-up times (e.g. for cleaned surfaces)

• Long cure times (could be improved by use of weld/adhesive- or rivet/adhesive-

combinations)

• Need clarification in respect of fatigue

• Aging

• Repairing of bonded car



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Analysis Process


Transfer line forces to

analytical sandwich model Line forces and moments

on flange edge

Global model Simple joint modelling

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FEM Guidelines

• FE Guidelines:

• Congruent mesh

• Linear shell elements

• 4-node shell elements are preferred (approx. 10 mm)

• Adhesive joint is modeled by beam elements (radius approx. 5 mm)

• FE results: Grid Point Forces

Upper shell

Lower shell

Shell normal

Local

coordinate system

Calculation point


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Adhesive Joint Calculation Process


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Initial Condition: Initial flaw size has to be specified

Thickness

Moduli

Poisson Ratios

Local

coordinate system

Path for J-integral

evaluation

Sandwich model (schematic)


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• Sandwich model

• Shell elements

Rotation of the cross beam

section

Second moment of area

Shear moduli

with


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• J-integral equation:

• for each point of loading time series

• Calculation of safety factor:

Gth = Threshold strain energy release rate


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Example


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Correlation

Fatigue test simulation results and

corresponding cracking on test

Test rig with Jaguar XJ body-in-white

SAE Paper 2012-01-731

A Fracture Mechanics Approach to Durability Calculations for Adhesive Joints

Peter Heyes (HBM UK, Ltd.),

Gunnar Björkman (Volvo Technology),

Andrew Blows and Tim Mumford (Jaguar/Land Rover Cars),

Paul Briskham (Coventry University)


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• The testing and software implementation work described in this

paper was carried out as part of the “Bonded Car” collaborative

research project, the partners being Jaguar Land Rover, HBM UK

Ltd (nCode), Coventry University, Warwick University, Innoval

Technology, Henrob and Stoke Golding Applied Research.

• The project was co-funded by the Technology Strategy Board's

Collaborative Research and Development program, following an

open competition. The Technology Strategy Board is an executive

body established by the UK Government to drive innovation. It

promotes and invests in research, development and the

exploitation of science, technology and new ideas for the benefit of

business - increasing sustainable economic growth in the UK and

improving quality of life.

• The theoretical basis of the work presented here was developed as

part of an earlier project conducted by the Volvo Group, whose

contribution is gratefully acknowledged.

Acknowledgements


measure and predict with confidence

www.hbm.com/ncode

Dr.-Ing. Stephan Vervoort

HBM nCode Produkte

Tel: +49 (0)89 9605372 18

Fax: +49 (0)89 9605372 21

Email: [email protected]

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Thanks for Your Attention

fracture mechanical approach for fatigue of adhesive...

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