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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
Automation Simulation World Congress, October 29 – 30, 2013
Bond seams of Audi TT
Source: http://wiki.zimt.uni-siegen.de
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• Example: Adhesive joints in automotive engineering
Background/Motivation
Source: www.volkswagen-forum.com
Automation Simulation World Congress, October 29 – 30, 2013
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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
Background/Motivation
Automation Simulation World Congress, October 29 – 30, 2013
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Analysis Process
Automation Simulation World Congress, October 29 – 30, 2013
Transfer line forces to
analytical sandwich model Line forces and moments
on flange edge
Global model Simple joint modelling
7
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
Automation Simulation World Congress, October 29 – 30, 2013
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Adhesive Joint Calculation Process
Automation Simulation World Congress, October 29 – 30, 2013
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Adhesive Joint Calculation Process
Initial Condition: Initial flaw size has to be specified
Thickness
Moduli
Poisson Ratios
Local
coordinate system
Path for J-integral
evaluation
Sandwich model (schematic)
Automation Simulation World Congress, October 29 – 30, 2013
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Adhesive Joint Calculation Process
• Sandwich model
• Shell elements
Rotation of the cross beam
section
Second moment of area
Shear moduli
with
Automation Simulation World Congress, October 29 – 30, 2013
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Adhesive Joint Calculation Process
• J-integral equation:
• for each point of loading time series
• Calculation of safety factor:
Gth = Threshold strain energy release rate
Automation Simulation World Congress, October 29 – 30, 2013
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Example
Automation Simulation World Congress, October 29 – 30, 2013
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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)
Automation Simulation World Congress, October 29 – 30, 2013
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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
Automation Simulation World Congress, October 29 – 30, 2013
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