Frictional heating in cyclotrimethylene trinitramine during nanoscratching: Plasticity and localized melting

Abstract

Frictional heating in cyclotrimethylene trinitramine (RDX) can generate hotspots, which are local regions of elevated temperature that may trigger explosion. In this study, we quantified the characteristic size of the hotspot to be approximately 20 Å based on the width of the nanoscale shear band in shock loading simulations and further examined the temperature rise in RDX crystals during high-speed nanoscratching using molecular dynamics simulations. These simulations were performed under varying sliding velocities, normal loads, and sliding directions to explore the relationship between friction coefficient, shear stress, and localized hotspots. Our results revealed that, despite the anisotropic friction properties, the temperature rise exhibited a consistent dependence on shear stress, with a critical shear stress identified above which the hotspots experienced a sharp increase in the temperature. This temperature transition correlates with localized melting, as demonstrated by the analysis of atomic temperature and bond-length changes. These findings enhance our understanding of the mechanical and thermal stability of energetic materials.