APPLICATION OF AN ELASTIC MODEL TO THE LARGE-DEFORMATION, HIGH-TEMPERATURE STRETCHING OF POLYPROPYLENE

A physically based constitutive law for the deformation of polymers is applied to the stretching of polypropylene to large deformations at e levated temperatures. In this deformation regime, which is applicable to many forming processes, necking of the material is a persistent fea ture. The theory is elastic in nature, but includes the necking phenom enon as an inherent property. It is incorporated into a commercial fin ite element code and used to model a number of different experimental modes of deformation, both uniaxial and biaxial. Comparison is made wi th the experiments and it is found that both strains and forces are re presented realistically, even though the true nature of the material i s viscoelastic. Some of the discrepancies in the model predictions are traceable to its elastic nature. (C) 1997 Elsevier Science Ltd.