Generation of residual stress field in metal by an interference shock wave

In recent years, laser peening technique has been used for the purpose of improving the fatigue strength of metal materials. However, the compressive residual stress field created by laser peening has characteristic differences in the stress value and the thickness of the stress field layer compared to conventional technologies. We conducted experiments to clarify the peening mechanism of metals when irradiated with nanosecond laser pulses. Austenite stainless steel was irradiated with a laser pulse of 2.5 ns, and the compressive residual stress inside the recovered sample was examined by x-ray diffraction. Using the dislocation density model, we analyzed the experimental results and showed that the residual stress field due to the nanosecond laser can be explained by the local stress generated by the shock wave.