Application of Laser Peening on Welded Rib-plate of Mild Steel

摘要

Laser peening is an innovative surface enhancement technology to introduce a compressive residual stress on metallic materials. Experimental results showed that laser peening was effective to prevent SCC and enhance fatigue strength. However, effects of laser peening to steel for structure and its welded zone are not clarified. In this paper, residual stress of welded toes in rib-plates and fatigue life with laser peening was investigated by comparing to that without laser peening. X-ray diffraction was used to measure the residual stress. The main results are summarized as follows. 1) Laser peening can change the tensile residual stress to large compressive residual stress in welded toes. The nearer from the welded toe, the larger the effect by laser peening was. 2) Fatigue crack was not initiated from peened parts, even though stress amplitude of the peened part is twice stress amplitude of crack-initiated parts. 3) Fatigue life of the rib-plates with laser peening was prolonged at least three times or more compared to that without laser peening.