Compaction shock dissipation in low density granular explosive

Abstract

The microstructure of granular explosives can affect dissipative heating within compaction shocks that can trigger combustion and initiate detonation. Because initiation occurs over distances that are much larger than the mean particle size, homogenized (macroscale) theories are often used to describe local thermodynamic states within and behind shocks that are regarded as the average manifestation of thermodynamic fields at the particle scale. In this paper, mesoscale modeling and simulation are used to examine how the initial packing density of granular HMX (C4H8N8O8) C4H8N8O8 having a narrow particle size distribution influences dissipation within resolved, planar compaction shocks. The model tracks the evolution of thermomechanical fields within large ensembles of particles due to pore collapse. Effective shock profiles, obtained by averaging mesoscale fields over space and time, are compared with those given by an independent macroscale compaction theory that predicts the variation in effective thermomechanical fields within shocks due to an imbalance between the solid pressure and a configurational stress. Reducing packing density is shown to reduce the dissipation rate within shocks but increase the integrated dissipated work over shock rise times, which is indicative of enhanced sensitivity. In all cases, dissipated work is related to shock pressure by a density-dependent power law, and shock rise time is related to pressure by a power law having an exponent of negative one.

In Situ Imaging during Compression of Plastic Bonded Explosives for Damage Modeling

“…Hu et al have used 2D simulations to evaluate the debonding of HTPB binder from ammonium perchlorate (AP) particles and compared them with corresponding experiments to validate a CFEM approach [ 33 ]. Gonthier’s group has developed a coupled FEM-discrete element modeling (FEM-DEM) approach to identify energy dissipation and hotspot generation in microstructure simulations that are used to inform macroscale models of explosive response [ 34 , 35 , 36 ]. The 2D modeling employed in this research is a pre-cursor to guide the judicious development and use of 3D models.…”

Modeling and Simulation of RDX Powder Thermo‐Mechanical Response to Drop Impact

“…Commercially‐based DEM techniques [25–28] are powerful for their computational practicality in modeling macroscale particulate flow behaviors governed by the elastic or rigid body collisions of thousands of highly mobile particles. However, powdered EM materials have been shown to behave as highly plastic particles under drop hammer dynamic loads [14–29]. Modeling those types of impacts require that the plasticity of the particles be considered in the numerical treatment.…”

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