Analysis of die design for the stamping of a bathtub

The die design for the stamping of the base of an enameled bathtub was performed using the three-dimensional finite-element method. The difficulty encountered in the stamping process is the occurrence of both fracture and wrinkling. To facilitate the analysis, a series of experiments was conducted to obtain the material properties and the forming-limit diagram for the enamel steel used for the actual production and for the finite-element simulations, the latter being first performed to analyze the metal-flow causing the wrinkles on the draw-wall. The strain distributions obtained from the finite-element simulations were also used in conjunction with the forming-limit diagram ro predict the onset of fracture. In addition, the effects of blank-holder pressure and friction on the occurrence of fracture and wrinkling were investigated. An optimum drawbead distribution on the die face was then determined, according to the finite-element analysis, to avoid the formation of both fracture and wrinkles. (C) 1997 Elsevier Science S.A.