Optimization of residual stresses induced by multiple laser shock processing

Laser shock processing (LSP), also known as laser peening (LP), proves to be superior to conventional surface treatments such as shot peening, including deeper penetration of the residual stresses. The LSP treatment, which uses a very short pulse (ns) of intense (GW cm^-2) laser beam to generate compressive residual stresses near the surface of the metallic samples, demonstrates a significant improvement of fatigue life and stress corrosion cracking resistance. In this paper, finite element analysis (FEA) combined with particle swarm optimization (PSO) method to predict the magnitude and distribution of optimized multiple LSP impacts on 304 stainless steel. The results of the simulation clearly show that optimized multiple LSP can mitigate residual stresses loss in the centre of the single impact zone and generate homogeneous compressive residual stresses at the surface. The results also reveal the optimized multiple LSP can lead to deeper penetration of the compressive residual stresses in the samples.