Characteristics of stress distribution within the metal sheet bent by laser shock forming

Abstract

Laser shock forming(LSF) is an emerging method for metal sheet forming. Besides dimension accuracy, the stress distributions on the surface and within the target material are also important for the actual engineering applications. In this paper, the stress distributions along the sheet depth direction and parallel to the target surface have been made clear through simulations. The deformation mechanisms of two typical deformation modes, convex and concave, were directly verified and further explained by the temporal and spatial residual strain/stress distribution. For the convex deformation, the stress distribution along the thickness direction is roughly divided into three regions: the near surface layer, the intermediate layer and the bottom layer. Among these, both the top and bottom surface layers are mainly subjected to compressive residual stresses. For this case, the stress wave effect does not ‘penetrate’ the sheet material, and a stress gradient is induced along the depth direction of the sheet, which is responsible for final convex deformation. For the concave deformation, the stress distribution along the thickness direction is divided into two regions: the surface tensile stress zone and the lower compressive stress zone. The stress wave effect penetrates the sheet material, directly causing the overall tensile deformation of the sheet material, and finally causes the sheet material to undergo deep plastic deformation. The stress distribution characteristics of the two deformation modes can provide useful references for the practical application.