A thermodynamic theory on the nonlinear viscoelasticity of glassy polymers, 2: An application to the yield mechanism

We have investigated yield conditions from the viewpoint of irreversible thermodynamics. We have found that the nonlinear viscoelastic constitutive equation developed in the first paper shows the maximum rate of entropy production near the yield point. From the constitutive equation and the condition of the maximum rate of entropy production, we have derived a yield equation that behaves like Eyring's model. This yield equation is equivalent to those derived from the condition of peak stress. In addition, the concept that yield occurs at the maximum rate of entropy production can be connected with Robertson's theory and the results of molecular simulation.