Finite Element Analysis of the Effect of Friction in High Pressure Torsion

High pressure torsion (HPT) is one of the most important techniques among various methods that create severe plastic deformation in the production of bulk materials with nano/ultrafine grained microstructures. Since the driving force in deforming the workpiece in HPT is surface friction, understanding of the friction effect is critical for successful application of HPT. In this study, the friction effect in HPT was analyzed using the finite element method. The distribution of effective strain on the contact surface of the HPT samples under different friction conditions was investigated. The friction force influenced the effective strain more in the middle and edge regions than in the central region. The condition for the minimum friction factor that could achieve a sticking condition between the surfaces of the dies, and the samples in the middle and edge regions, was investigated. There was a critical friction coefficient in which the effective strain varies sharply with an increasing friction coefficient.