Simulating thermal explosion of cyclotrimethylenetrinitramine-based explosives: Model comparison with experiment

Abstract

We compare two-dimensional model results with measurements for the thermal, chemical, and mechanical behavior in a thermal explosion experiment. Confined high explosives (HEs) are heated at a rate of 1°C∕h until an explosion is observed. The heating, ignition, and deflagration phases are modeled using an Arbitrarily Lagrangian-Eulerian code (ALE3D) that can handle a wide range of time scales that vary from a structural to a dynamic hydrotime scale. During the preignition phase, quasistatic mechanics and diffusive thermal transfer from a heat source to the HE are coupled with the finite chemical reactions that include both endothermic and exothermic processes. Once the HE ignites, a hydrodynamic calculation is performed as a burn front propagates through the HE. Two cyclotrimethylenetrinitramine-based explosives, C-4 and PBXN-109, are considered, whose chemical-thermal-mechanical models are constructed based on measurements of thermal and mechanical properties along with small scale thermal explosion measurements. The simulated dynamic response of HE confinement during the explosive phase is compared to measurements in larger scale thermal explosion tests. The explosion temperatures for both HEs are predicted to within 5°C. Calculated and measured wall strains provide an indication of vessel pressurization during the heating phase and violence during the explosive phase. During the heating phase, simulated wall strains provide only an approximate representation of measured values indicating a better numerical treatment is needed to provide accurate results. The results also show that more numerical accuracy is needed for vessels with lesser confinement strength. For PBXN-109, the measured wall strains during the explosion are well represented by the ALE3D calculations.

The effect of polymer matrices on the thermal hazard properties of RDX-based PBXs by using model-free and combined kinetic analysis

“…One could use decomposition heat and charge density data in Table 3 for current materials. The heat conductivity of RDX is around 0.106 W.m -1 .K -1 while its PBXs is around 0.21-0.28 W.m -1 .K -1 [42,43], which indicates that the polymer could increase the heat conductivity to a similar extent (around 2 times). In this way, the dependence of critical half-thickness on the initial temperature was simulated and plotted in Fig.…”

“…The corresponding charge performance and sensitivity parameters of RDX and its PBXs are summarized in Table 3. [43][44][45]. D, Charge density, in g.m -3 ; Me, Molecular weight, g.mol -1 ; Im, Impact energy, in J; Hd, Heat of decomposition, J.g -1 ; Tb, Critical temperature for thermal explosion, in Celsius.…”

A historical and current perspective on predicting thermal cookoff behavior

“…We will return to a comparison of DSC and macroscopic thermal explosion experiments in a later section. Probably the most successful approach at predicting large-scale thermal explosions is due to Tarver and coworkers, who developed simple sequential and autocatalytic kinetic models for a variety of explosives over the past 25 years (13)(14)(15)(16)(17). The approach assumes temperature-dependent thermal properties of both the solid and gas phases, uses activation energies similar to those in more complicated mechanisms, and optimizes the kinetic parameters against ODTX experiments.…”

Kinetics Based Reaction Modeling for Heterogeneous Explosives

“…The range of possible scenarios run from slow events such as cook-off to the case of detonations. The recent, successful work in using multi-step, finite-rate models in simulating cook-off [40] provided a good point of departure.…”

“…It is a goal to eventually model the impact and shock-induced reactions using the same modeling approach [36]. This option will be explored here using a model proposed in [40]. In this earlier study, scaled thermal explosion experiment (STEX) scenarios are modeled using a multi-step, multi-species reaction mechanism.…”