Influence of residual stress on fatigue strength of non-load-carrying fillet welded joints

In this paper, the influence of plate thickness on the fatigue strength of non-load-carrying fillet welded joints is examined both experimentally and analytically, from the viewpoint of weld residual stresses. In order to control the longitudinal residual stresses (in the direction of the weld line), rib-cruciform joint specimens with various plate widths were prepared. On the one hand, specimens of which heat input for each pass was varied were also prepared to control the transverse residual stresses (in the perpendicular direction to the weld line). Using these specimens, both residual stress measurements and fatigue tests were carried out. It was found that the plate width of specimen had great effects on the longitudinal residual stresses and little effect on the transverse residual stresses. And it was also found that the transverse residual stresses increased as the heat input decreased. As far as the heat input was constant, the plate width had no effect on the fatigue strength. On the other hand, the heat input significantly influenced the fatigue strength of joints with the same thickness of main plate. That is, the fatigue strength in the case of high heat input was much higher than in the case of low heat input. From above results, it is concluded that the fatigue strength of non-load-carrying fillet welded joints depends on the transverse residual stresses and that the tensile residual stresses increase as the plate thickness increases and/or the heat input decreases, causing a reduction of fatigue strength.