Effect of cutting process on the residual stress and fatigue life of the welded joint treated by ultrasonic impact treatment

Abstract

To obtain the final shape and ensure quality in the manufacturing of welded structural components, a cutting process is usually applied to remove the weld edges. Comparative tests were conducted with replicas of non-load-carrying cruciform joints in the as-welded and ultrasonic impact peened conditions, which were before or after cutting process at the two ends. Those contained the measurement of three types of residual stress distributions of various weld lengths by the cut-release method and relevant fatigue tests. The locations of fatigue crack initiation and fracture surfaces were also determined. The experimental results demonstrated that in the welded joint peened by the ultrasonic impact treatment, the welding residual stress component among the superimposed residual stresses relaxes after cutting. Owing to the original compressive welding residual stress in the peened welded joint, the cutting process has a distinct effect on the change of the superimposed residual stress distribution near the cutting edges. Furthermore, the cutting process reduces the fatigue life improvement of the peened welded joint and transfers the positions of the fatigue crack source. For the fatigue life improvement of welded structures, arranging ultrasonic impact treatment after the cutting process is better. Besides, the compressive superimposed residual stress in the UIT-welded joint will not relax completely under cyclic fatigue loading.