Effects of material and process parameters on wrinkling of conical parts in modified hydroforming process

摘要

Hydrodynamic deep drawing assisted by radial pressure with inward flowing liquid, proposed as a benchmark in the Shemet2017 conference, is selected to analyze the influence of the process parameters on wrinkling behavior. The radial pressure can reduce forming force and increase drawing ratio in hydrodynamic deep drawing, but at the same time can cause wrinkling. The wrinkling in the wall area of conical parts is a challenge because the sheet is not supported in this region. The side wall wrinkling of St13 and copper conical cups is investigated through numerical simulation and experimental measurements. After preliminary experimental validation, the FEM simulation was performed to explore the process parameters. The effects of radial and cavity pressures, sheet thickness, punch velocity, and friction coefficient on wrinkling were studied based on the developed FEM model and using a geometric method. Maximum wrinkling height was presented as a parameter for wrinkling investigation for conical parts. It was demonstrated that the severity of wrinkles predicted by the numerical model is influenced strongly by the process parameters. Finally, according to the obtained results, and by controlling the maximum wrinkling height parameter as a result of pressure change, a piece without wrinkling and rupture was properly formed.