Analyses of metal forming problems by the boundary element method

Abstract

Forming is one of the most common manufacturing processes. This paper reviews the applications of the boundary element method (BEM) to analyses of various forming processes, e.g. extrusion, rolling, profile rolling, etc.The boundary element formulations for elastic-plastic and elastic-viscoplastic problems involving large strains and rotations are considered first. The elastic strains are assumed to remain small. The rotations and nonelastic strains, however, are allowed to be large. Bulk compressibility effects, which are often ignored for finite strain problems of metallic solids, are explicitly included here.An updated Lagrangian approach is adopted for the BEM analyses of forming processes. The frictional conditions at the tool-workpiece interface are introduced through a smeared interface element. For several forming problems, the frictional stresses change direction at the neutral region, and the location of this region is not known a priori. It is demonstrated here that the BEM can be used to efficiently and accurately analyse this class of planar and axisymmetric forming problems involving both material and geometric nonlinearities, along with complicated interface conditions. The numerical results obtained from the FEM analyses are also compared to those obtained from FEM with regard to efficiency and accuracy.