A novel viscoplastic model of high-density polyethylene pipe material

Abstract

A nonlinear three-component elastic viscoplastic strain-rate-dependent model was developed for a high-density polyethylene pipe material. In this model, the stress at any point is assumed to be a unique function of the instantaneous irreversible strain, its rate and acceleration, irrespective of any intermediate stress and strain history. However, a reference strain rate was assumed and below this the response was independent of the strain rate. Parameters of the model were determined using published data on strain-rate-dependent material responses. The model was developed within the elasto-viscoplastic framework so that it could be used in solving boundary value problems. The return mapping algorithm of strain-rate-dependent elasto-plastic material is described with the detailed derivation of the consistent tangent operator for quadratic convergence. The model was successfully implemented in an existing finite-element code. Finite-element analyses using this model were capable of simulating the strain-rate-dependent stress–strain relation, the response to a jump in the strain rate and an unloading–reloading response for a high-density polyethylene pipe material published in the literature.