A 3-D Model of Cold Drawing in Engineering Thermoplastics

This article presents a 3-D multiplicative finite strain model for cold drawing (necking) in engineering thermoplastics. Amorphous as well as semi-crystalline polymers are considered. The notion of intermediate (local) stress-free configuration, that is associated with the multiplicative decomposition of the deformation gradient, is shown to provide an appropriate framework for the modeling and analysis of this class of materials. A hyperelastic stored energy function is written with respect to the intermediate configuration to yield the finite elastic response. It is then combined with the J ₂-flow theory to model the finite inelastic response. The constitutive integration procedure is based on a product formula algorithm with elastic-predictor/inelastic-corrector components. Numerical results are presented to show the behavior of the three dimensional model in the finite strain range.