Effect of Laser Peening on Fatigue Properties of Butt-Welded Joints with Angular Distortion

Abstract

Laser peening (LP) is a well-established technique for introducing compressive residual stress (RS) near the surface of metal components to improve their high-cycle fatigue properties. In this study, butt-welded joint specimens of SBHS500 steel with angular distortion were prepared and treated with LP. X-ray diffraction showed that the maximum compressive RS over 400 MPa was introduced near the surface by applying LP with an irradiated pulse energy of 7.5 mJ, a spot size of 0.42 mm, and a pulse density of 800 pulses/mm2. The effect reached a depth of approximately 0.15 mm from the surface. The specimens were subjected to a uniaxial fatigue test with a stress ratio of 0.1 together with specimens without LP. The results showed that the fatigue life was prolonged by LP. However, in the stress range of 300 MPa, the detrimental effect of angular distortion predominates over the beneficial effect of LP, showing that the fatigue life extension by LP is not evident.