Investigation of the effect of process parameters in sheet hydroforming process

In this study, the effect of the process parameters in hydraulic deep drawing (HDD) of the cylindrical cups is investigated using design of experiments (DOE) and finite element (FE) methods. First, the experiments have been designed using fractional factorial design. In this design maximum pressure of the fluid, punch speed, punch nose radius, die entrance radius, the friction coefficient between the sheet and punch, and friction coefficient between the sheet and die are considered input variables. Also, punch force and thinning ratio are considered response functions. Designed experiments were performed by a verified FE model. Finally, effective parameters on the response functions were specified using the analysis of variance (ANOVA). Results demonstrate that the maximum pressure and the punch nose radius are the most significant parameters for the punch force. The punch force increases by 55% with increasing both the maximum pressure and punch nose radius (from low level to high level). Furthermore, investigating the interaction effects of the input parameters on the punch force illustrated that the interaction between the punch nose radius and the punch friction coefficient is notable and should be considered. In addition, increasing the punch nose radius and die entrance radius causes a decrease in the thinning ratio by almost 54 and 40%, respectively. On the other hand, increasing the die friction coefficient leads to an increase of 40% in thinning ratio.