High explosive shock initiation model with shear band reactivity and carbon condensation effects

Hot spot formation in shocked high explosive materials, usually due to local heat generation around collapsed pores and other defects, has commonly been used to explain the onset of chemical decomposition in the shock initiation regime. Many ignition and growth reactive flow models employ this concept, by assuming that local reaction at hot spots, and the subsequent thermally driven consumption, or growth, into the surrounding cooler explosive, is responsible for the build up to detonation. Past computational investigations have shown, however, that in addition to localized heating, pore collapse may also yield non-local effects, in particular shear band formation in the vicinity of collapsed pores and in the bulk. Recent molecular dynamics simulations of shocked TATB have shown that such shear bands lose much of their crystallinity, and have significantly lower reaction energy barriers compared to the bulk crystal. We therefore hypothesize that the increased reactivity of shear bands may play a crucial role in the shock to detonation transition. We present a reactive flow model that incorporates the enhanced reactivity of shear bands, in addition to other reaction pathways common to ignition and growth, such as the aforementioned hot spot reaction and growth, and carbon condensation kinetics. The model is applicable to both shock initiation and detonation experiments.

Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344.

LLNL-ABS-833315