A boundary element analysis of axisymmetric upsetting

Abstract

Interfacial conditions at the tool-workpiece interfaces play crucial roles in various metal forming operations. Axisymmetric upsetting and ring compression tests provide useful means for investigating interfacial friction conditions analytically and experimentally. A unique feature of deformation in ring compression, as well as in rolling and forging, is the existence of a neutral point (or region) along the tool-workpiece interface where the tangential relative velocity between the deforming material and the die becomes zero. The frictional stresses usually change direction at the neutral point (or region). The location of this point (or region), however, is not known a priori. It is demonstrated here that the boundary element method (BEM) can be used to analyze, efficiently and accurately, this class of axisymmetric problems involving both material and geometric nonlinearities to investigate the effects of interfacial conditions on the stress and deformation histories. Numerical results for sample problems of axisymmetric upsetting of solid and hollow cylinders are presented. The BEM results are compared against those obtained from FEM analyses.