Analysis of plastic deformation behavior of HDPE during high pressure torsion process

High pressure torsion (HPT) is an effective tool to modify microstructures via severe plastic deformation. In order to optimize the process conditions and then to control the change in microstructure, the estimation of the plastic strain achieved in the processed material is of utmost importance. Noting that the key parameters of HPT process are essentially the imposed pressure and the number of revolutions applied to the samples. The goal of this work is to numerically investigate the effects of these parameters on the plastic strain homogeneity during HPT of a typical semicrystalline polymer (high-density polyethylene: HDPE). To this end, compressive tests at different strain rates were used to estimate the material parameters of a phenomenological elastic-viscoplastic model. Then, the HPT process was analyzed by 3-dimensional finite element method to highlight the distribution of the plastic strain, the equivalent plastic strain rate and the mean normal stresses. It was found that the optimal strain homogeneity was obtained by a weak vertical displacement and a high torsion angle. (C) 2012 Elsevier Ltd. All rights reserved.