高分子材料の粘弾性と粘塑性を考慮した速度形構成モデル

抄録

A constitutive model to describe the rate-dependent nonlinear behavior for a class of solid polymers is developed from phenomenological points of view. A particular emphasis is placed on a unified multiaxial formulation of viscoelastic and viscoplastic deformation of polymers. The constitutive model is based on irreversible thermodynamics and it is systematically derived from thermodynamic potentials, i.e., free energy and dissipation energy functions. A capability to describe the viscoelastic nature is incorporated into the present model through the Ziegler's thermodynamic reconstruction of the classical rheology models. The rate-dependent nonlinear viscoplastic behavior of polymers is described using the combined isotropic and kinematic hardening format of the Chaboche type. The effect of hydrostatic pressure on the viscoplasticity of polymers is also taken into account. The present model enables us to describe a rate-dependence of the initial tangent modulus, that of the flow stress in the subsequent nonlinear regime and a tension-compression asymmetry of the viscoplastic dilatational yielding of polymers. Validity of the present model is evaluated on the basis of stress-strain responses of a thermoplastic resin (PEEK) under different strain-rate conditions.