FATIGUE STRENGTH OF OUT-OF-PLANE GUSSET TREATED BY ULTRASONIC NEEDLE PEENING WITH A SMALL RADIUS TIP PIN

Abstract

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 needle peening with a 1.5mm radius tip pin on fatigue strength of out-of-plane gusset by using bending fatigue tests. The results show that the treatment can improve fatigue strength, when mean stress is not changed after the treatment is carried out. It also shows that the effect of the treatment become less with increasing mean stress after the treatment is carried out, and when the treatment is not sufficient at weld toe.