Constitutive relations for a viscoelastic body under crystallization conditions

The problem of describing the thermomechanical behavior of viscoelastic polymer materials under conditions of their post-production cooling accompanied by crystallization is considered. A variant for constructing phenomenological constitutive relations, which continuously reflect the relation between the stress and strain tensors in a wide range of temperature variation, is suggested. The relations are based on representation of the medium in the form of a composition of a melted material and a completely crystallized material with allowance for the history of permanent incipience and deformation of the new phase in the interval of phase-transformation temperatures. To determine the material functions and constants, experiments are planned on specimens at temperatures corresponding to particular phase states. Results of experiments and numerical analysis of the fields of displacements generated by solidification of a circular polyethylene plate are given.