Fatigue probabilistic assessments on a circular lap welding joint of stainless steels under axial loading

Under axial tensile-compression loads, fatigue behaviors of a circular lap welding joint of the cone and pipe using stainless steels of different grades with a circular stress raiser were examined. The internal stress raiser caused root fatigue cracks. The fracture starting site was at the weld interface, which had a small weld toe radius inducing stress concentration. When the weld toe radius approached zero, the fatigue strength and scatter depended on the weld opening angle. The failure criteria and prediction under axial loading could be based on the effective stress concentration factor. The uniform scatter band model was used to examine the test data. With the highest coefficient of determination of 0.8164, the semi-logarithmic bilinear model best fitted the actual data. The 3P Weibull distribution most closely matched the Benard's estimate with a coefficient of determination of 0.9728. The strength scatter bands of the welded joint were much larger than those of the plane sheet, depending on the degrees of stress concentrations and defects. The plane sheet to welded joint's fatigue strength ratio rose with fatigue life and was particularly high at low failure probability.