Direct numerical simulation of shock-to-detonation transition (SDT) in energetic materials using microstructure images

Energetic material microstructures contain pores, defects and cracks which function as sites for energy localization (hotspots, shear bands) when impacted by shocks. Chemical reactions are usually triggered at these sites, releasing further energy to support the shock which could eventually transit to detonation wave. Shock to detonation transition (SDT) study is usually done in a multi scale framework, which combines a reactive burn model at a macro scale with a microstructure informed meso-scale model. In this work, SDT for Class V HMX microstructure of the mm scale is studied using DNS of reactive pore collapse. The simulations are performed using a Eulerian sharp interface high order numerical solver SCIMITAR3D. Tarver-3 chemical reaction model and recently advanced MD-consistent material models are employed in the simulations. The collapse details of each arbitrary-shaped pore in the microstructure are well resolved. The numerical results display fully two-dimensional effects and heterogenous structure of shock waves, in contrast to the homogenized 1D simplifications typically employed in macro-scale reactive burn models. The simulations are performed for various shock strength and up to the time when a detonation wave is observed, which is indicated by the Von Neumann pressure spike and coupling of the reactive zone to the shock front. Impact sensitivity in terms of run-to-detonation distance (Pop-plot) is quantified for Class V HMX, which shows good agreement between experimental and numerical studies.