Thermomechanical conversion in metals: dislocation plasticity model evaluation of the Taylor-Quinney coefficient

TL;DR

This paper develops a thermodynamic framework linking the Taylor-Quinney coefficient to effective temperature, and validates it through finite-element analysis of aluminum alloy deformation experiments, revealing material-dependent and strain-dependent heat conversion.

Contribution

It introduces a thermodynamic dislocation theory-based model that relates the Taylor-Quinney coefficient to effective temperature, providing a new understanding of heat generation during plastic deformation.

Findings

The Taylor-Quinney coefficient depends on the effective temperature.

Finite-element simulations match experimental stress-strain and temperature data.

The coefficient varies with material and strain, increasing as deformation progresses.

Abstract

Using a partitioned-energy thermodynamic framework which assigns energy to that of atomic configurational stored energy of cold work and kinetic-vibrational, we derive an important constraint on the Taylor-Quinney coefficient, which quantifies the fraction of plastic work that is converted into heat during plastic deformation. Associated with the two energy contributions are two separate temperatures -- the ordinary temperature for the thermal energy and the effective temperature for the configurational energy. We show that the Taylor-Quinney coefficient is a function of the thermodynamically defined effective temperature that measures the atomic configurational disorder in the material. Finite-element analysis of recently published experiments on the aluminum alloy 6016-T4 \citep{neto_2020}, using the thermodynamic dislocation theory (TDT), shows good agreement between theory and experiment for both stress-strain behavior and temporal evolution of the temperature. The simulations include both conductive and convective thermal energy loss during the experiments, and significant thermal gradients exist within the simulation results. Computed values of the differential Taylor-Quinney coefficient are also presented and suggest a value which differs between materials and increases with increasing strain.