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IIW recommendations for the fatigue assessment of welded structures by notch stress analysis: IIW-2006-09

W Fricke, Hamburg University of Technology, Germany

Woodhead Publishing Series in Welding and Other Joining Technologies No. 78

 - provides detailed recommendations for the number analysis of notch stress by the finite or boundary element method
 - discusses structural weakening by keyhole-shaped notches and the consideration of multiaxial stress states
 - provides four comprehensive examples, illustrating the variety of structures which can be analysed and the range of results that can be obtained from different models

The notch stress approach for fatigue assessment of welded joints is based on the highest elastic stress at the weld toe or root. In order to avoid arbitrary or infinite stress results, a rounded shape with a reference radius instead of the actual sharp toe or root is usually assumed. The present guideline reviews different proposals for reference radii together with associated S-N curves. Detailed recommendations are given for the numerical analysis of notch stress by the finite or boundary element method. Several aspects are discussed, such as the structural weakening by keyhole-shaped notches and the consideration of multiaxial stress states. Appropriate S-N curves are presented for the assessment of the fatigue strength of different materials. Finally, four examples illustrate the application of the approach as well as the variety of structures which can be analysed and the range of results that can be obtained from different models.

Published in Association with the International Institute of Welding (IIW)

£115.00 / US$195.00 / €140.00

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About the author

Professor Dr-Ing. Wolfgang Fricke is Head of the Institute for Ship Structural Design and Analysis at Hamburg University of Technology, Germany.

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Contents

Introduction

Background to the approach
 - Overview
 - Notch rounding approach
 - Modified notch rounding approach
 -  Small size notch approach for plates with thickness < 5 mm
 - Approaches for multiaxial stress states

Numerical analysis of notch stresses
 - Numerical methods (FEM, BEM)
 - Links to the structural stress analysis
 - Modelling of welds for notch stress analysis
 - Stress analysis using mesh refinement
 - Stress analysis using sub-models or super-elements
 - Special aspects
 - Parametric formulae for notch stress concentration factors

Fatigue strength
 - Design S-N curves for reference radius of 1 mm
 - Correction for mild weld notches with reference radius of 1 mm
 - Design S-N curves for mild weld notches with larger radii
 - Design S-N curves for the small size notch approach with reference radius of 0.05 mm for plates < 5 mm thick

Demonstration examples
 - Fillet welded cruciform joint
 - T-Joint between two RHS members with weld toe failure
 - Fillet-welded end connection of a RHS member with non-fused weld root Faces
 - Spot-welds in an automobile door

Acknowledgement

References