Effects of viscosity on viscous pressure bulging (VPB) of Al1060 sheet

Abstract

The properties of pressure-transmitting medium have a great effect on the formability of sheet metal in sheet flexible-die forming, such as rubber-pad forming and viscous pressure forming (VPF). In this study, viscous pressure bulging (VPB) experiments were used to investigate the effects of viscosity on Al1060 sheet. At the same dome height, the configurations of bulging specimen varied with three different viscosity viscous mediums (1#, 550,000 g/mol; 2#, 700,000 g/mol; and 3#, 900,000 g/mol). The thickness strain distributions of specimen formed by a higher viscosity medium had a relatively uniform distribution. In order to further study the effects of viscosity on VPB, a CDSB-FEM-EFGM program was used to analyze viscous pressure bulging process. The configuration, stress, strain, and wall thickness distributions of bulging specimen were obtained. The numerical analysis results had a good agreement with the experimental ones, which also showed that properties of the viscous medium had a great effect on the formed specimen. The formability of sheet metal can be further improved through increasing the viscosity of viscous medium.