A new proposal for assessment of the fatigue strength of steel butt‐welded joints improved by peening (HFMI) under constant amplitude tensile loading

Abstract

AbstractExperimental fatigue data for butt‐welded joints in as‐welded condition and under constant amplitude tensile loading were analysed using the effective notch stress system and a new master curve analysis that takes the local stress ratio, Rlocal, into account. The local stresses needed for computation of Rlocal are calculated with the notch strain approach in conjunction with the reference radius concept.The main focus was to predict with the derived master curve the fatigue strength of peened butt‐welded joints. The lowest surface residual stresses after peening were first estimated based on reported measurements and an analytical lower bound result. The predictions showed quite similar strength dependences and FAT values as reported for high‐frequency mechanical impact treated welds for applied stress ratio R = 0.1. The benefits of peening reduce faster for higher strength steels when R increases. When R = 0.5, the FATs are practically the same for all steel grades.