Numerical and experimental study on the deformation of aluminum alloy ring treated by ultrasonic shot peen forming

Ultrasonic shot peen forming (USPF) is a promising and widely used forming technique for thin metallic parts. In this paper, detailed deformation behavior of the aluminum alloy ring caused by USPF was studied, which is of a great significance to industrial applications for roundness correction and reshaping of the ring parts, such as wheel hub, petrochemical containers, pressure vessels, and spacecraft shells. Firstly, the motion of the single pin during USPF was recorded by a high-speed camera. Then, by combining the recorded results and the stress wave theory, the firing pin motion was approximately described as an effective impact of 100 times per second and the average impact velocity of 5 m/s. By considering the firing pin movement, the 3D USPF FE model of a cell AA6061-T6 sheet was developed successfully for obtaining the accurate plastic strain field. Subsequently, a 2D USPF FE model of the ring part was developed, which is able to obtain similar residual stress profiles with the 3D cell’s FE model by inputting the plastic strain profiles induced by the firing pin impact. Based on the results of experimental and numerical simulation, it was observed that the convex deformation of the ring part increases as the wall thickness decreases and the central angle of the treatment area increases. In addition, a wave contour and a local deformation with a little influence on the other area of the ring part can be achieved by three USPF treatment areas distributed in one-sided surface and two-sided surface, respectively.