Effects of ultrasonic peening on fatigue strength of out-of-plane gusset joints

Effect of high frequency peening treatment with a small radius tip pin, which is less than 3mm radius tip pin, still remains unclear, although the effect of ultrasonic impact treatment on fatigue strength has been investigated. The objective of this study is to investigate the effect of ultrasonic peening with a 1.5mm radius tip pin on fatigue strength of out-of-plane gusset welded joints. Plate bending fatigue tests of those joints carried out. The results show that the peening can improve fatigue strength, when mean stress does not change or already changes before the peening is carried out. It also shows that the effect of the ultrasonic impact peening become less with increasing mean stress after the ultrasonic peening was carried out, and when the ultrasonic peening is not sufficient for the weld toe.