Effect of viscosity of viscous medium on formability of Al1060-O sheet in viscous pressure forming (VPF): an experimental study

The viscosity of viscous medium used in viscous pressure forming (VPF) is one of the most significant processing parameters, which is rather complicated and lack of systematical investigation. In this paper, the viscosities of six kinds of viscous mediums with different molecular weights are measured and compared by using a dynamic shear rheometer. Then, extrusion tests for different viscous mediums are conducted, and the cavity pressures during different extrusion processes are acquired. The flow stresses of viscous mediums are determined by using a combination of extrusion test and FEM simulation, which can provide material parameters input for related FEM simulation of VPF. In addition, bulging specimens and three kinds of conic parts of Al1060-O sheet are obtained by VPF using different viscous mediums. The results show that the viscosity of viscous medium has a significant influence on specimen configuration. The viscosity difference leads to different flow stresses of viscous mediums, which further leads to the variation of stress loading and transmission in forming process. And the higher viscous adhesive stress generated by using viscous medium with a higher viscosity can make metal flow more easily and improve sheet formability.