The simulation of the viscoplastic forming process by the finite-element method

The rigid-viscoplastic FEM is used to analyze the viscoplastic forming process in this paper. The general rigid-viscoplastic FEM formulation is given and specific formulations of isothermal forging processes and superplastic forming are listed also. As an application, the combined extrusion process of pure lead, which is strain-rate sensitive at room temperature, is analyzed. The simulated results reveal the variation of the forming load with the stroke and its dependence on conditions. On the basis of the metal flow patterns defined by the rigid-viscoplastic finite-element method, the change of the position of the neutral layer is given and it is found that the occurrence of folding at the flange may be attributed mainly to an abnormal flow pattern. Moreover, the calculated results bring to light the rule of deformation distribution and its dependence on strain rate.