Investigation into the pre-forming's effect during multi-stages of tube hydroforming of aluminum alloy tube by using useful wrinkles

Tube hydroforming is a process for manufacturing of lightweight components, especially automotive parts, with advantages of cost and weight reduction, better structural integrity and increased strength and stiffness over the conventional stamping process. Generally, the hydroformed parts can be obtained by multi-stages made up of bending, pre-forming and finishing. Based on the characters of FEM and using the useful wrinkles, the process of multi-stages was investigated by using an aluminum alloy. For avoiding the typical failure modes such as folding back, wrinkling, buckling and fracture due to unreasonable selection of the internal pressure and the axial punch feeding, the optimization strategy was created and the process parameters were optimized by using "useful" wrinkles instead of "harmful" wrinkles in the pre-forming stage and in the finishing stage. The suitable pre-forming die cavity shape was discussed. The results from simulation keep a reasonable agreement with that from experiment.