Fatigue performance of Q345 steel welded joints by high temperature ultrasonic peening

In order to investigate the effect of high temperature ultrasonic peening on fatigue performance of Q345 steel welded joints, the weld toes were treated by self-developed ultrasonic peening device at room temperature(20℃), 250℃, 350℃ and 450℃, respectively. The results indicated that when the stress ratio R was equal to 0.1, both the conventional and hightemperature ultrasonic peening treatments greatly enhanced the fatigue performance of Q345 steel butt joints. Moreover, compared with the as-welded joints, the degree of improvement of fatigue performance of Q345 steel welded joint treated at 250℃was the highest, up to 99.41%. In addition, the degree of improvement of fatigue performance increased first and then decreased with the increasing peening temperature under the influence of residual stress and stress concentration.