Influence of unidirectional loading pusher head structure on the deformation law of bionic egg-shaped shell parts in internal high-pressure bulging

Abstract A solid particle medium flexible bulging technology is proposed to solve the problems of low molding precision, poor stability, and uneven deformation that may occur when processing bionic egg-shaped shells by the traditional bulging process. By optimizing the mold parameters, such as the angle and height of the pusher head, the flow characteristics of the granular material are improved, resulting in improved machining accuracy and surface quality when molding egg-shaped plastic shells. In this paper, we utilize a ø0.8-1 mm yttria-stabilized zirconia ceramic bead to serve as a pressure-transfer medium during the granular media forming process. Several different shapes of pusher heads with cone angles of 45°, 60°, 75°, and 90° and heights of 10mm, 25mm, and 40mm were designed and manufactured. The numerical model of simulation was verified by the analysis of strain inhomogeneity coefficient, and the maximum thinning rate at the apex of bulging of the egg-shaped test was measured and calculated. The results show that the maximum thinning rate at the apex of bulging is the largest for the pusher head with 45° cone angle and 25mm height, and the strain distribution is the most uniform and the expansion effect is the best. The study shows that the optimization of the process parameters of the pusher head shape can effectively improve the uniformity of the strain distribution and thickness distribution during the egg-shaped shell forming process, thus improving the machining accuracy of the plastic deformation of the bionic egg-shaped tube test piece.