Evaluation of sheet metal formability, viscous pressure forming (VPF) dome test

Viscous pressure forming (VPF) offers a versatile approach to low volume stamping of difficult-to-form sheet metal alloys. The process entails the use of a highly viscous medium as a forming tool. Compared with solid metal punch forming, the necking in the sheet metal can be postponed in the VPF process, i.e. the VPF can improve the formability of sheet metal due to low friction effect at sheet/medium interface. In this study, the process of sheet stretching with VPF has been simulated by the finite element-based code DEFORM. The predictions were compared with the experimental measurements conducted at the ERC/NSM. An approach to determine the formability of sheet metal in stretching using a critical damage value concept has been proposed. It has been found that the formability of the sheet stretched with VPF is higher than that of the sheet stretched with a hemispherical solid metal punch.