Experimental investigation of initial internal pressure on hydroforming multi-stepped shaft

To investigate the effect of process parameter in tube hydroforming, internal pressure of hydroforming three-stepped shaft was studied experimentally in this paper. The general equation of the calculation of initial internal pressure is developed, corresponding experiment was carried out respectively, and the reasons of failure format, wrinkle and burst, were discussed. It is shown that during the process, blank was formed under axial compression stress and circumferential tensile stress. The selection of initial internal pressure can refer to equation (1). For the three-stepped shaft of this paper, 30 MPa is reasonable value. When the pressure is lower than 20 MPa it tends to wrinkle, and when the pressure is more than 40 MPa it inclines to burst.