An internal state variable thermodynamic model for determining the Taylor-Quinney coefficient of glassy polymers

The evolution of β exhibits the same tendency at different stain rates: β first increases to the maximum value and then decreases with increasing strain. β is maximized when the plastic strain is nearly 0.4 at strain rates of 0.1 and 1 s−1. However, this does not accord with the location of the minimal post-yield stress. As shown in Fig. 3, for the low-strain rate case, when the true plastic strain is smaller than 0.35, the strain-softening part dominates, whereas the strain-hardening part dominates when the true plastic strain is larger than 0.6. This indicates a competition mechanism.193