Effect of blank holder pressure on viscous pressure forming aluminum alloy ladder parts

Viscous pressure forming(VPF) is suitable for forming difficult-to-form sheet metal parts. An investigation in the effect of blank holder pressure(BHP) on VPF aluminum alloy ladder parts was conducted. Based on experimental and numerical simulation results of the effect of BHP on dimensional accuracy, Wall-thickness reduction, forming pressure, material flow and defects(such as wrinkling and fracture) of specimens, the effect patterns of BHP load path on VPF ladder parts were explained. The limits of BHP corresponding to specimens with no defect and with wrinkling or fracture defect were determined. In the limits of formable BHP, the variable load path of BHP was beneficial to drawing blank into the die and decreasing wall-thickness reduction of specimens. The experimental result show that the ladder parts of good surface fineness and high dimensional accuracy can be obtained by variable load paths of BHP.