Numerical Investigation of Residual Stress Field Induced by Array-Type Laser Shock Peening

Laser shock peening (LSP) increases fatigue strength and life while reducing crack propagation by creating compressive residual stress on the material's surface. The shock pressure generated by the laser and the target material surface is directly proportional to the laser power density. As the peak pressure induced by the laser pulse exceeds a threshold, a drop in compressive residual stress at the center of the round spot known as a “residual stress hole” is observed due to reverse plastic deformation. In the present paper, a numerical investigation is carried out to speculate the array type LSP (ALSP) with round spots for compressive residual stress generation. 3-D explicit numerical simulations with non-reflecting boundaries have been employed to study the influence of ALSP on the residual stress hole generation and compare it to the residual stress field induced by conventional LSP. The investigation included 1-D and 2-D arrays with different gaps between the spots and spot sizes. It is found that, with proper parameter selection, including the gap between spots, array dimension, and spot size, ALSP has the potential to reduce residual stress hole generation. The influence of ALSP with a large impact radius (R = 1 mm) is limited to no gap cases, but more pronounced for different array configurations with a small impact radius (R = 0.25 mm) ALSP.