Research On The Affect Of Strain Rate Sensitivity Of Viscous Medium On Formability Of Sheet Metal

Viscous pressure forming (VPF) is one of the sheet flexible-die forming process. Using a kind of semi-solid, flowable and viscous material as pressure-carrying medium, VPF is especially suitable for the deformation of difficult-to-form materials and parts with complex shapes. The forming process is the interaction and coupled deformation between viscous medium and sheet metal. The viscosity and the strain rate sensitivity of viscous medium have great effect on the deformation of sheet metal.Tensile tests under different strain rate at the room temperature had been carried out to analyze the strain rate sensitivity of the tested sheet metals firstly. The results show that strain rate has a little effect on aluminum 1060-O and little effect on aluminum 1060-H. Viscous pressure bulge equipment had been designed. Using two kinds of viscous medium which have different strain-rate sensitivity indexes, viscous pressure bulge (VPB) tests had been carried out under two loading speeds. FLDs of the tested sheet metals were determined. The results show that in the range of strain rates used in this paper, loading speed and strain-rate sensitivity of viscous medium have great effect on the formability of the tested sheet metals.Viscous pressure bulge process had been analyzed by numerical simulation. The effect of loading speed and mechanical properties of viscous medium on the formability of sheet metal was determined. The results show that when loading speed changes, the viscous medium with higher strain-rate sensitivity index has greater effect on the formability of sheet metal. Under higher loading speed, the difference of formability between parts bulged by different viscous mediums is greater. The results got by numerical simulation are consistent with the conclusions made by VPB tests.