The Peak Stress Method Applied to Fatigue StrengthAssessments of Load Carrying Transverse Fillet Welds with Toe or Root Failures

This paper deals with the local approach based on the Notch Stress Intensity Factors (NSIFs) to analyse the fatigue behavior of welded joints. In transverse load carrying fillet-welded joints, failure may occur either at the toe or at the root, depending on the geometry. At the toe, due to the flank angles that are usually encountered in practice, mode I local stresses are singular, while mode II stresses are not. Conversely, at the root of the particular joints analysed in the present paper both mode I and mode II stresses are singular and must be taken into account in fatigue assessments. Recently, a simplified finite element-based method to readily estimate the mode I NSIF and mode II SIF has been proposed (the so-called Peak Stress Method, PSM). According to the PSM, the mode I NSIF and mode II SIF are proportional to the finite values of the opening and sliding stresses, respectively, evaluated at the point of singularity by means of a finite element analysis, as soon as an appropriate mesh pattern is drawn. In this paper the PSM is first summarized and then applied to assess the fatigue strength of load carrying transverse fillet welds, where competition between toe and root failures exists.