A mechanistic model for shock initiation of solid explosives

Abstract

This paper is devoted to the building of a model for the ignition and growth of a detonation in pressed solid explosives. The ignition model describes the various phenomena occurring at the microscopic scale during viscoplastic pore collapse. The growth stage is represented by a model combining inner combustion inside the pores and outer combustion on the surface of the grains. These microscopic models are incorporated into a macroscopic one. The macroscopic model reproduces waves propagation and takes into account the various couplings between the microscopic and macroscopic scales. Pores and grain size distributions are also considered. The governing equations are solved using a shock tracking high resolution scheme, in order to avoid numerical smearing of the shock front. The role of microscopic topology of the explosive is investigated. Results are validated on pressure gauge records and shock to detonation transition distance (Pop-plots).

Mechanistic Reactive Burn Modeling of Solid Explosives

“…We have not been able to find measured in situ profiles, but features of particle velocity histories shown in Fig. 5(b) are comparable to those seen for HMX-based explosives (Gustavsen et al 1999 andMassoni et al 1999). Similarly, Fig.…”

“…This is a severe simplification, but we find it necessary at this stage of model development. Similar idealizations are used in other attempts where identical hot spots are multiplied by the density of identical hot spots to represent the whole (see for example, Massoni et al 1999). There is, however, one important difference in that in our modeling, the aggregation of hot spots is imagined in terms of reacting surface areas.…”

“…Then it is known that the assumption of partial pressure equilibrium leads to the mixture pressure in the same form (Massoni et al 1999) in which Γ and P * are related to constituent quantities by 1/Γ= φ g /Γ g + (1-φ g )/Γ s , and (3.46)…”

“…Here we will follow the formulation by Massoni et al (1999). We believe that their formulation will be useful in their basic form even for advanced models.…”

“…If "hot spots" are mentioned in these models, they are used only empirically to reproduce certain characteristics such as shock-induced ignition temperature and induction time for global reactions. The second type, represented by Kang et al (1992), Massoni et al (1999), and Bennett et al (1998), is an extension of the first type to include a microscopic description of the origin of hot spots, such as void collapse and frictional sliding. The evolution of reacted mass fraction is now modeled by simplified chemical kinetics occurring on the microscale.…”