Effects of Die Shoulder on the Prolateness and Deformation in the Bulge Test

In the present investigation, the prolateness and the deformation of sheet metal deformed under lateral pressure with dies of different shoulder radii are analyzed. It is found that at the beginning of deformation, the bulge shape becomes more spherical with increasing polar height. Beyond a certain stage of deformation, its shape, however, begins to deviate more and more from that of a sphere until fracture at the polar region occurs. The present results show that the die shoulder radius has little influence on the shape of the bulge, but it tends to inhibit deformation so that formability may be improved by using a die of small shoulder radius.