Prediction of Nonlinear Specific Heat During Single Crystal HMX Phase Transition

TL;DR

This paper introduces a new continuum mechanics-based model for predicting the highly nonlinear specific heat behavior during the phase transition of HMX crystals, including critical temperature and heat capacity variations.

Contribution

It presents a novel thermodynamically consistent model that derives specific heats directly from continuum mechanics, improving upon previous simplified or calibrated approaches.

Findings

Predicts order of magnitude changes in specific heat during phase transition

Provides a new expression for critical temperature with extremum in chemical heating rate

Demonstrates highly nonlinear specific heat behavior through numerical simulations

Abstract

We develop a thermodynamically consistent chemo-thermo-mechanical model for the $\beta\rightarrow\delta$ phase transition of energetic HMX crystals. In contrast to previous models, which either considered specific heat to be a constant or utilized a calibrated function, this model provides novel expressions for the specific heats at constant volume and constant elastic strains derived directly from continuum mechanics. In addition, the model provides a novel prediction for the critical temperature at which the chemical heating rate achieves its extremum for Arrhenius kinetics. The numerical solution predicts highly nonlinear specific heat behavior including order of magnitude changes.