A Generalized Finite Element Analysis of Sheet Metal Forming With an Elastic-Viscoplastic Material Model

A finite element analysis for elastic-viscoplastic problems in the presence of large strains is presented in this paper. The formulation is capable of using any of a class of combined creep-plasticity constitutive models with state variables for the description of material behavior. The specific problem considered is plane strain sheet metal forming using the constitutive model originally proposed by Hart. Numerical results are presented for sample problems and the effects of variations in several process parameters, such as velocity, friction at punch, and die interfaces, are investigated. The present report includes membrane, bending, and shear effects as well as the coupling among them and no a priori assumption is made about the strain distribution across the thickness. Thus, it unifies the earlier approaches used in sheet metal forming analysis and helps in gaining crucial insights into the process of sheet metal forming. It can also be extended to other large strain design and manufacturing problems.