IIW Recommendations for the Fatigue Assessment of Welded Structures by Notch Stress Analysis

Abstract

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. Different proposals for reference radii exist, e.g. Radaj proposed a fictitious radius of 1 mm to consider micro-structural support effects for steel. The present guideline reviews different proposals for reference radii together with associated S-N curves. Detailed recommendations are given for the numerical analysis of the 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. Regarding the fatigue strength, appropriate S-N curves are presented for different materials. Finally, four examples illustrate the application of the approach, as well as the variety of structures that can be analysed and the scatter of results obtained from different models.