Nonequilibrium Thermodynamics of Amorphous Materials III: Shear-Transformation-Zone Plasticity

TL;DR

This paper reformulates the shear-transformation-zone theory of amorphous plasticity using effective-temperature thermodynamics, deriving constraints on transition rates and an equation of motion for the effective temperature.

Contribution

It introduces a thermodynamic framework for STZ theory, explicitly deriving transition rate constraints and an effective temperature evolution equation.

Findings

STZ transition rates follow an Eyring form due to thermodynamic constraints

Derived an equation of motion for the effective temperature in amorphous materials

Reformulated STZ theory within an effective-temperature thermodynamics framework

Abstract

We use the internal-variable, effective-temperature thermodynamics developed in two preceding papers to reformulate the shear-transformation-zone (STZ) theory of amorphous plasticity. As required by the preceding analysis, we make explicit approximations for the energy and entropy of the STZ internal degrees of freedom. We then show that the second law of thermodynamics constrains the STZ transition rates to have an Eyring form as a function of the effective temperature. Finally, we derive an equation of motion for the effective temperature for the case of STZ dynamics.