Stress Relief at Corner Joint and Effect of Stress Relief on Fatigue Strength

Abstract

Some series of large-scale fatigue tests have already been conducted on the longitudinal groove weld, which is familiar at the corner welded joint of box sectional members. It was cleared in these tests that the fatigue crack originated from the root blowhole and that the fatigue strength was considerably lower because of the effect of the tensile residual stress. When disallowable blowhole is detected at fabrication, the reduction of the tensile residual stress seems to be useful to improve the fatigue strength instead of the repair welding. In this study, firstly, techniques for the local reduction of the tensile residual stress at the corner welded joint were examined, namely, stress relief annealing, low-temperature stress relief and bead welding. This research proved that low-temperature stress relief was most efficiently and economically method. Secondly, the reliability of low-temperature stress relief was confirmed on a large-scale box member. Finally, the fatigue test was carried out to investigate the effect of low-temperature stress relieving on the fatigue strength of welded joints. The result verified that stress relief could improve the fationv ctrnnoth