Cyclic viscoplasticity of high-density polyethylene: Experiments and modeling

Abstract

Observations are reported on high-density polyethylene in uniaxial cyclic tensile tests. Two deformation programs are considered. In tests with a strain-controlled program, each cycle of deformation involves tension up to a maximum engineering strain ϵ max and retraction down to the zero stress. In tests with a stress-controlled program, any cycle of deformation consists of tension up to a maximum engineering stress σ max and retraction down to some minimum engineering stress σ min. The study focuses on low-cycle programs with a constant cross-head speed and small strains. A constitutive model is derived in viscoplasticity of semicrystalline polymers at isothermal three-dimensional cyclic deformations. Material constants in the stress–strain relations are found by fitting the experimental data. Good agreement is demonstrated between the observations and the results of numerical analysis. Some interesting phenomena are revealed by means of numerical simulation of cyclic deformations.