LASER GENERATION OF STRESS WAVES IN METAL

Today surface treatments are very important in the mechanical industry to increase the fatigue life of metal components. In addition to classical treatments such as shot peening, a new process is being developed. The laser shock surface treatment permits the creation of plastic strains and induction of compressive residual stresses in metals. It consists in irradiating a metallic sample with a short but intense laser pulse. As a consequence a high temperature high pressure plasma is created at the sample surface. An elastic-plastic wave propagates in the sample, creating plastic strains. The present study deals with the effects of laser-induced stress waves on residual stresses, microhardness and surface quality of a standard steel (0.55% C). The residual stresses generated are compressive for a depth of up to 1 mm. With optimum conditions, we can produce homogeneous cover strips without surface deterioration.