The peak stress method to summarise the fatigue behaviour of fillet-welded steel joints subjected to axial or bending loading

The Peak Stress Method is an engineering, FE-oriented application of the local approach based on the Notch-Stress Intensity Factors (N-SIFs), which quantify the intensity of the local, linear elastic stress field at the potential crack initiation points (either the weld toe or the weld root). All effects due to plate thickness, joint shape and loading mode (axial or bending) are fully included in the N-SIFs, such that a single design curve is sufficient to assess the fatigue strength of arc-welded, fillet-welded joints in structural steels, tested in the as-welded conditions. The design stresses to analysed the fatigue strength are the peak stresses evaluated by FEM at the weld toe or the weld root, which are modelled as sharp notches with a tip radius equal to zero. The mean value of the FE size adopted to calculate the singular peak stresses can be chosen within a range of applicability, while the FE pattern of elements to use is the free mesh generated automatically by Ansys numerical code. Due to the rather coarse meshes required to apply the PSM and its suitability to be used directly with results of three-dimensional FE analyses, it seems that the method is rather useful in the everyday design practise.