Pressure estimation in the hydroforming process of sheet metal pairs with the method of upper bound analysis

Hydroforming is one of the new technologies in the manufacturing processes, in which hollow pieces are formed under pressure of a fluid. The basic parameter in this process is the pressure control of the fluid. This article deals with the process of hydroforming of a pair of metal sheets. After obtaining the kinematically admissible velocity field, the pressure equation is obtained by the upper bound analysis. This equation can be applied for each part if the instantaneous geometry of the deformed sheet in the die cavity zone during the process can be analytically expressed. The effects of the parameters of work-hardening, friction and blank size have been taken into considerations. To validate the results of this work a hemispherical part formed in the hydroforming of single-sheet process has been considered. The results obtained by this analysis have been compared with the experimental results.