FINITE-ELEMENT MODELING OF INELASTIC DEFORMATION OF DUCTILE POLYMERS

Two uniaxial constitutive models, a nonlinear viscoelastic (NVE) model and a viscoplastic (VP) model, have recently been developed for time dependent inelastic analysis of ductile polymers. This study extends t hese models to provide a multiaxial formulation. The new multiaxial mo dels are implemented in a general purpose finite element program, toge ther with a conventional treatment of geometrical nonlinearity. The so lution procedure is based on a simple explicit integration method that is suitable for the new material models and is easy to implement. Two example problems are studied to evaluate the performance of the new f inite element procedure. Finite element simulations of a perforated hi gh density polyethylene (HDPE) plate under remote uniaxial loading are performed, and finite element model simulations of an HDPE pipe secti on under parallel plate loading are also performed. The finite element modelling results are then compared with the measured experimental re sults. It is found that the finite element model provides good predict ions of the inelastic deformation of HDPE under various loading histor ies, including cases that involve a highly nonlinear material and geom etrical response.