Simulation of prestressed ultrasonic peen forming on bending deformation and residual stress distribution

Elastic prestressed ultrasonic peen forming (UPF) is beneficial to obtain sufficient bending deformation and decrease spherical deformation. Numerical models of free UPF and prestressed UPF are established in this study to analyze effects of forming parameters (prebending curvature, firing pin velocity, offset distance, and plate thickness) on bending deformation and residual stress distribution. Meanwhile, the comparisons between free UPF and prestressed UPF are studied. The results show that increasing prebending curvature is beneficial to enlarge spanwise bending deformation and decrease spherical deformation of the plate. Large firing pin velocity, small offset distance, and small plate thickness play positive roles in the increase of spanwise bending deformation. Larger and deeper compressive residual stress can be obtained in prestressed UPF due to prebending deformation before shot peening process. Large prebending curvature, large firing pin velocity, and small plate thickness significantly increase surface and maximum compressive residual stress and total depth of compressive residual stress, while descending offset distance only slightly increases these values. Experiments are conducted and the simulated results agree with experiments. This study provides guidance for parameter selection in prestressed UPF and sufficient deformation for wing plate with large thickness.