MINIMIZATION OF THE SHEET THINNING IN HYDRAULIC DEEP DRAWING PROCESS USING RESPONSE SURFACE METHODOLOGY AND FINITE ELEMENT METHOD

A B S T R A C T In most of sheet forming processes, production of the final parts with minimum thickness variation and low required force is important. In this research, minimization of the sheet thinning and forming force in the hydraulic deep drawing process was studied. Firstly, the process was simulated using the finite element method (FEM) and the simulation model was verified compared to experimental results. Then the sheet thinning ratio and punch force were modeled as objective functions using the response surface methodology (RSM). In this model, process parameters including punch nose radius, die entrance radius and maximum fluid pressure were the input variables. Required experiments for the RSM were designed using the central composite design (CCD) method and performed by FEM. Finally, optimum point of the parameters was obtained by multi-objective optimization of the objective functions using the desirability function method based on response surface model and then evaluated. In addition, optimum ranges of the parameters were determined using overlying contour plots. Results showed that the response surface models had good adequacy. According to this model, increasing of the punch nose radius and die entrance radius lead to decreasing of thinning ratio and increasing the maximum punch force. Also the maximum punch force increases by increasing the maximum fluid pressure. Optimization results represent reduction of the thinning ratio almost 10% compared with conventional results.