Numerical estimation of frictional effects in equal channel angular extrusion

Abstract

The purpose of this study is to numerically estimate the friction coefficient for equal channel angular extrusion with and without back pressure. Three-dimensional finite element analysis is employed to estimate the coefficient of friction from the maximum pressing load, a crucial variable in die design. The finite element model consists of a billet, a plunger, a ram, and a die, where the interface between the billet and the die is modeled by the Coulomb friction model with truncated shear stress. The numerical model was validated by comparing the grid deformation patterns in the extrusion symmetry plane, and by comparing the load versus stroke curves for the ram (pressing load) and for the plunger (back pressure). Results indicate that the coefficient of friction can be accurately estimated from the maximum pressing load, but it is necessary to modify the traditional Coulomb friction model.