Investigation into the forming of a complex cup locally constrained by a round die based on an innovative hydromechanical deep drawing method

Sheet hydroforming has become a topic in the manufacturing fields in the world because of its many advantages. Based on the proposed hydromechanical deep drawing (HDD) with uniform pressure onto the blank, the forming process of a complex square cup was investigated. Different from the conventional concept, the forming die was a round die so that the effect of liquid pressure as a local constraint instead of a rigid die could be obtained. The forming process, wall thickness variation rules and the dimensional accuracy were investigated in details in both experiment and simulation. A conclusion was drawn on the failure types and the ways to remove the failure types were discussed. The forming process using square punch based on the round die was observed directly in simulation, and it proved that the simulated results kept reasonable agreement with the experiment.