Optimisation of the distribution of wall thickness in the multistage sheet metal forming of wheel disks

The distribution of wall thickness in the multistage sheet metal forming of wheel disks having a distribution of requisite strength was optimised in order to reduce the weight of the disks. Because high strength around the corner of the inner flat region of the formed disk is desirable, the decrease in wall thickness at the corner was minimised. The first two stages in which the wall thickness around the corner of the inner flat region in the final disk is determined were dealt with. Axisymmetric deformation in the two-stage forming process of disks is simulated by the rigid–plastic finite element method. The calculated distribution of the wall thickness after forming was in good agreement with the experimental results. The effects of the drawing ratio and the punch corner radius in the first stage, on the decrease in wall thickness at the inner corner after the second stage were examined by both finite element simulation and experiment. It was found that the drawing ratio and the punch corner radius in the first stage have optimal values for the decrease in wall thickness, respectively.