Abstract

Viscoelasticity exists widely in various materials, such as asphalt concrete and polymer, and is also an important part of time-dependent deformation of rock materials. Based on Rice irreversible thermodynamics, the viscoelasticity of material is discussed. A set of scalar internal state variable is introduced to characterize the structural rearrangement in material sample, and the general viscoelastic constitutive equation is derived by giving specific complementary energy function and kinetic law of internal state variables. The proposed equation covers constitutive equation from classical viscoelastic models, can describe nonlinear viscoelasticity scenes. The properties of fundamental thermodynamic function, on which the proposed constitutive equation is based, are analyzed. We point out the special conjugate relation between thermodynamic forces and internal state variable, prove the flow potential function has monotonic decreasing with time in constrained conjugate space, and indicate that flow potential relates to probability of states of material in statistical mechanics level.