Fatigue Strength of Non‐load‐carrying Fillet Welded Joints: Effects of Weld Residual Stresses and Stress Concentration

The fatigue strength of non‐load‐carrying fillet welded joints of KE36(TMCP) steel was studied. Both residual stress measurements and fatigue tests were carried out, with the plate thickness, the plate width and the heat input being varied. Specimens given a Post Weld Heat Treatment (PWHT) were also prepared. The plate width had no effect on the fatigue strength, because it hardly affected the transverse residual stresses at the weld toe. However, the heat input influenced the transverse residual stress distribution, and a significant difference in fatigue strength due to the heat input was observed, especially when N ≥ 10 6 cycles. It was also found that PWHT removed almost all the residual stresses at the weld toe, improving the fatigue strength drastically. In this study, the values of stress concentration factor K 2 were estimated by Machida's method and it was concluded that the thickness effect resulted from a combination of both stress concentration and residual stresses with the contribution of the latter being particularly significant for N ≥ 10 6 cycles.