Effects of residual stresses on the fatigue performance of welded steels with longitudinal stiffeners

Residual stresses may affect the behavior of welded steels under fatigue loading. However, for design of welded structures the height and distribution of residual stresses from welding are often not known so that tensile residual stresses in the order of the yield strength are conservatively assumed. Here presented results focus on the influence of residual stresses on the fatigue strength of longitudinal stiffeners made from a mild steel S355NL and a high strength steel S960QL. The initial residual stress conditions were measured using X-ray and neutron diffraction. In order to characterize the influence of residual stresses on the fatigue strength, specimens were tested in the as-welded condition and after a stress relieving heat treatment. The fatigue testing was conducted under alternating constant amplitude loading with a stress ratio of R=-1.