Finite-element simulation of the elliptical cup deep drawing process by sheet hydroforming

Abstract

This paper presents the development of an elastoplastic finite-element method (FEM) program dedicated for the sheet hydroforming (SHF) process and the simulated results of the elliptical cup deep drawing process using the program. First, the development of the SHF simulation program based on the home-made static FEM code STAMP3D is described. Several new techniques to give a sheet the proper hydraulic pressure are proposed and implemented in STAMP3D. Then, simulations of the elliptical cup deep drawing process are carried out and the simulated results are compared with those of experiment. Local thinning is observed at the punch shoulder and at the wall part in the simulated thickness strain distribution, which is in good agreement with the experimental observations. The formability of the product is also carefully examined by comparing with the result of the conventional press forming in which much larger thinning is observed at the punch shoulder. It is clarified that the difference in the thickness strain distribution between the SHF and the conventional press forming is due to the friction increasing effect which is one of the major features of the SHF process. The result shows that the simulation predicts the friction increasing effect well, verifying the validity of the developed program. Moreover, it is clarified that the SHF process gives much better formability than the conventional press forming process for the present product.