Head‐To‐Head Comparison of Molecular and Continuum Simulations of Shock‐Induced Collapse of an Elongated Pore in an Energetic Molecular Crystal
Yen T. Nguyen, Dilki Perera, Puhan Zhao, Thomas D. Sewell, H. S. Udaykumar
Abstract
Abstract Shock‐induced collapse of an elongated pore in the energetic crystal β ‐HMX ( β ‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazoctane) is examined using all‐atom molecular dynamics (MD) and continuum mechanics. The continuum simulation employs a recently proposed MD‐guided material model for β ‐HMX. Collapse‐induced shear band formation and hotspot‐zone properties are calculated using both MD and continuum mechanics, for nearly identical simulation domains and identical impact conditions. The continuum model predicts shear band patterns and pore collapse behavior in good agreement with MD results; shear localization, plastic heating, and hydrodynamic impact‐generated temperature rise lead to geometrically complicated hotspot zones in the vicinity of the collapse site. This work demonstrates that—for the ≈10 GPa shock pressure studied—isotropic rate‐dependent Johnson‐Cook‐type elastoplastic models for HMX can provide physically consistent pore‐collapse dynamics and hotspot features in comparison to MD, for nontrivial pore shapes. Such physically accurate models are required for reliable predictions of detonation sensitivity and performance for shocked energetic crystals. Opportunities for further model improvement are identified.