Thermal analysis in the diamond turning of HMX crystals: An entropy-based approach for safety evaluation

To prevent thermal explosions in octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) crystals during diamond turning, it is essential to manage the energy dissipation process at cutting hotspots located at the tip of the diamond tool. In this study, a comprehensive model is developed to analyze the friction-induced thermal safety of HMX crystals during diamond turning, incorporating both heat conduction and entropy generation mechanisms. The temperature distribution and the entropy generation at the hotspots are further validated through equivalent heat conduction experiments. The underlying cause of the friction hazard is identified from both temporal and spatial perspectives. The results demonstrate that there is an intrinsic relationship between entropy generation and hazardous energy: an increase in entropy generation generally corresponds to a decrease in the quality (i.e., chaos level) of the hazardous energy during the diamond turning process. Compared to temperature distribution, entropy generation offers a more effective and reliable indicator for safety evaluation in both time and space domains. Therefore, the integrated use of temperature distribution and entropy generation as safety criteria is of great significance in elucidating the ignition mechanism of friction hotspots in HMX crystal machining.