Fracture mechanics-based method for prediction of safety factors of adhesive bondings
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Fracture mechanics-based method for prediction of safety factors of adhesive bondings

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The increasing pressure on reducing costs has lead to light-metal designs which demand diverse joining techniques, such as adhesives, riveting, screwing and welding. Over the last years the adhesive ...

The increasing pressure on reducing costs has lead to light-metal designs which demand diverse joining techniques, such as adhesives, riveting, screwing and welding. Over the last years the adhesive joint technology has seen a significant increase in interest, due to remarkable advantages compared to other joining techniques. The growing usage of adhesive joints i.e. in the automotive industry also leads to increased demand for simulation methods for structure, crash and fatigue analyses of bonded components. The awakened interest is reflected by the growing number of CAE-based methods for durability designs of bonded components. The lecture introduces a fracture mechanics-based method to predict the durability of bonded metal components applying on the J-integral solution approach, which is implemented in the modern, process-oriented software nCode DesignLife of HBM. Inputs of the analysis are results of a standard FE solver, material fatigue data and cyclic loading. The energy release rate is determined at the crack tip, where a concentration of local plastic deformation is observed. Based on these conditions the line integral (J-integral approach) could be employ to the combination of adhesive and bonded metal components. In the conventional analytical way the combination can be regarded as a layered composite. The theoretical principles of the method were developed in a research project in UK.

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Fracture mechanics-based method for prediction of safety factors of adhesive bondings Presentation Transcript

  • 1. European Altair Technology Conference, June 24 – 26, 2014 Fracture mechanics-based method for prediction of safety factors of adhesive bondings Dr.-Ing. Stephan Vervoort Hottinger Baldwin Messtechnik GmbH
  • 2. Agenda 1. Motivation 2. CAE based analysis process 3. FEM Guidelines 4. Adhesive Joints Calculation Method 5. Example 6. Correlation 7. Acknowledgements 2European Altair Technology Conference, June 24 – 26, 2014
  • 3. 3 • Lightweight designs • Weight minimization induced by material utilization • Material substitution (sheet metals -> composites) • Component designs consist of multiple material (steels, aluminum, composites, plastics) • Increased use of adhesive joints in automotive engineering: • 15 kg adhesives in average car • 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 Motivation European Altair Technology Conference, June 24 – 26, 2014 Source: Audi
  • 4. 4 • Example: Adhesive joints in automotive engineering Motivation Source: www.volkswagen-forum.com European Altair Technology Conference, June 24 – 26, 2014 Bond seams of Audi TT Source: http://wiki.zimt.uni-siegen.de
  • 5. 5 • Advantages • Nondestructive joining technology • Preservation of material properties • Prevention of thermal damage • Cold-heat equalization • Integration of additional functions • Tightness • Damping (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 • Repairing of bonded car • Aging Adhesives European Altair Technology Conference, June 24 – 26, 2014 Welds Rivets Adhesive Joints Source: TU Dresden, Fraunhofer, IWS, 3.Workshop, TGZ, 2009
  • 6. 6 CAE based analysis process Transfer line forces to analytical sandwich model Line forces and moments on flange edge Global model Simple joint modeling European Altair Technology Conference, June 24 – 26, 2014
  • 7. 7 FEM Guidelines • FE Guidelines: • Congruent homogeneous mesh • 4-node linear shell elements are preferred for the sheets (approx. 10 mm) • Adhesive joint is modeled by beam elements (radius approx. 5 mm) • Beam elements represent the edge of the adhesive joint • Required FE results: Grid Point Forces Upper shell Lower shell Shell normal Local coordinate system Calculation point European Altair Technology Conference, June 24 – 26, 2014
  • 8. 8 Adhesive Joint Calculation Process European Altair Technology Conference, June 24 – 26, 2014 L2 L1
  • 9. 9 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) European Altair Technology Conference, June 24 – 26, 2014
  • 10. 10 Adhesive Joint Calculation Process • Sandwich model • Shell elements Rotation of the cross beam section Second moment of area Shear moduli with European Altair Technology Conference, June 24 – 26, 2014
  • 11. 11 Adhesive Joint Calculation Process • J-integral equation: • for each point of loading time series • Calculation of safety factor: Gth = Threshold strain energy release rate European Altair Technology Conference, June 24 – 26, 2014
  • 12. 12 Automotive Example European Altair Technology Conference, June 24 – 26, 2014 • Typical kind of adhesive joint • CAE based process for coach peel specimen • Initial condition • Technical crack size: 0.4 mm • Adhesive thickness: 0.3 mm
  • 13. 13 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) European Altair Technology Conference, June 24 – 26, 2014
  • 14. 14 • 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 Uni- versity, 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 estab- lished 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 European Altair Technology Conference, June 24 – 26, 2014
  • 15. 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: stephan.vervoort@hbmncode.com Thanks for Your Attention Questions ?!