Mechanism of improvement of die corner filling in a new hydroforming die for stepped tubes

Seamless tubular components, such as stepped tubes, conical tubes and box shape tubes, are mainly produced in tube hydroforming process. In forming the components by this process, complete filling the die corners is very difficult or even impossible. In this paper, the mechanism of improvement of die corner filling in a new hydroforming die for cylindrical stepped tubes was studied by the finite element simulation. In this respect, the contact region between the tube and die, the material flow and the stress distribution in the die corner region were examined. The results obtained in this paper clarified the mechanism of improvement of die corner filling in the proposed die-set. In order to verify the simulation results, the new die-set was manufactured and experiments were performed. Experimental and simulation results demonstrated that by using the new die-set parts with sharp corners and with more uniform thickness distribution were produced.