Hydroforming of sheet metal using a viscous pressure medium

Conventional sheet hydroforming uses water with additives as pressure medium. However, viscous pressure forming (VPF), using a viscous material can also be used in the hydroforming process and offers the advantages of improved sealing to reduce leakage and easier handling in prototype production of a small number of parts. This paper describes the application of VPF to the forming of a non-symmetric part from steel, aluminum and a nickel alloy. FEA simulation and blank holder force control are utilized to optimize the process conditions. The effect of process variables upon the achievable part geometry is discussed. Comparison of FEA predictions with experiments illustrated that metal flow and thinning can be estimated with good accuracy.