Understanding the shock and detonation response of high explosives at the continuum and meso scales

Abstract

The shock and detonation response of high explosives has been an active research topic for more than a century. In recent years, high quality data from experiments using embedded gauges and other diagnostic techniques have inspired the development of a range of new high-fidelity computer models for explosives. The experiments and models have led to new insights, both at the continuum scale applicable to most shock and detonation experiments, and at the mesoscale relevant to hotspots and burning within explosive microstructures. This article reviews the continuum and mesoscale models, and their application to explosive phenomena, gaining insights to aid future model development and improved understanding of the physics of shock initiation and detonation propagation. In particular, it is argued that “desensitization” and the effect of porosity on high explosives can both be explained by the combined effect of thermodynamics and hydrodynamics, rather than the traditional hotspot-based explanations linked to pressure-dependent reaction rates.

Multiscale Approach to Shock to Detonation Transition in Energetic Materials

“…In our simulations, however, we have used a cutoff diameter of 70 μm, so that all particles below this are not considered. Ideally the discarded HMX would be lumped with the binder to create a homogeneous blend, sometimes referred to as a “dirty binder” . However, since the detonation properties for the blend are not known, we treat the blend as a single material of inert binder (Estane).…”

“…Our approach has been to develop a multiscale approach where the details at the microscale are connected to the mesoscale, since the microstructure can play an important role in detonation initiation [1][2][3][4][10][11][12][13][14][15][16]. As a first step, we run simulations of void collapse and collect ignition times and total power output as a function of shock pressure and void diameter [17][18][19].…”

Modelling the Fluctuations of Reactive Shock Waves in Heterogeneous Solid Explosives as Stochastic Processes

“…Reaction then develops into a “hump” or “spike” behind the leading wave, similar to what is observed in the embedded velocity gauge data . We note that while experimental data more closely resembles that of a rounded “hump,” the “spike” is a characteristic of the Lee‐Tarver reaction rate , and this particular feature could be improved via adaptation of a current burn model . Regardless, the effective heat release allows the material impedance to grow, so that energy is propagated forward along the right‐running characteristics; this increases the strength of the leading wave.…”

“…Thus, the application of stochastic process modelling to current burn models (e. g. CREST, SURF, AWSD, SHS, etc. ) is beyond the scope of this work. Instead, it is thought that the stochastic nature of the SDT problem will have its greatest influence near the impact surface and at early times, and a simplified description of the early stages of shock initiation is considered here in a one‐dimensional scenario.…”

“…A third approach, atomistic simulations, is acknowledged here as it pertains to the mesoscale, but it is not discussed in detail. These efforts are summarized in a recent review paper by Handley et al [22], which provides for additional context and identifies some of the knowledge gaps within the field. From this body of literature, it is clear that a large gap exists between the data being generated at the mesoscale and the calibration of continuum burn model parameters; indeed, the current work is focused on finding a link between the meso and continuum scales in some meaningful way.…”