Prediction of wrinkling and fracturing in viscous pressure forming (VPF) by using the coupled deformation sectional finite element method

Viscous pressure forming (VPF), which uses a kind of semisolid, flowable and viscous material as pressure-carrying medium (PCM), is a new flexible-die forming (FDF) process of sheet metals. In VPF, wrinkling and fracturing are two major failure modes. It is more difficult to predict the occurrence of wrinkling and fracturing in VPF than the conventional sheet metal forming processes due to the coupled deformation of sheet metal and viscous medium. In this paper, a sectional finite element method (SFEM) for analysis of the coupled deformation of sheet metal and viscous medium is developed. The C-B wrinkling criterion based on the energy method and a ductile fracture criterion on the basis of Lemaitre damage theory are proposed to analyze the VPF process of aluminum ladder part via combining with SFEM. The wrinkling and fracturing defects occurred in VPF are thus predicted. The effects of blank holder pressure and the interface condition between sheet metal and viscous medium on the wrinkling and fracturing formation in VPF are investigated. Based on the simulation results of SFEM, the comparison with the experimental data is conducted and the efficiency of the developed approach is thus validated.