Publications

The solubility of RDX (hexahydro-1,3,5-tri-nitro-1,3,5-triazine) in TNT (2,4,6-trinitrotoluene) at elevated temperatures is required to accurately predict the response of Comp-B3 (60:40 RDX:TNT) during accidents involving fire. As the temperature increases, the TNT component melts, the RDX partially dissolves in the liquid TNT, and the remaining RDX melts (203 ∘C) as the Comp-B thermally ignites. In the current work, we used a differential scanning calorimeter (DSC) to estimate the solubility of RDX in TNT at the melting point of RDX. Most DSC measurements of Comp-B3 do not show an RDX melt endotherm. The absence of an endotherm associated with the RDX melt has been interpreted as RDX being completely dissolved in TNT before reaching the melting point. We have observed that the endotherm is not absent, but is masked by exothermic reactions occurring at these elevated temperatures. We have inhibited the exothermic reactions by venting our DSC samples and measuring the RDX melt endotherm in our Comp-B3 samples at about 203 ∘C. Using the measured heat flow associated with the RDX melt and the latent melting enthalpy of RDX, we have approximated the solubility of RDX in TNT to be roughly 50–100 g RDX per 100 g TNT. The broad range is based on corrections for exothermic reactions occurring as the RDX melts.

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A series of compaction experiments was conducted to evaluate the mechanical, reactive, and deflagration-to-detonation transition behavior in Alliant Bullseye powder. Using a novel application of photonic Doppler velocimetry and light fibers, the experiments measured both compaction and combustion waves in porous beds of Bullseye subjected to impact by gun-driven pistons. Relationships between initial piston velocity and transition distance are shown. Comparison is made between the Bullseye response and that found in classic Type I DDT.

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The "DaMaGe-Initiated-Reaction" (DMGIR) computational model has been developed to predict the response of ideal high explosives to impulsive loading from non-shock mechanical insults. The distinguishing feature of this model is the introduction of a damage variable, which relates the evolution of damage to the initiation of a reaction in the explosive, and its growth to detonation. This model development effort treats the non-shock initiation behavior of explosives by families; rigid plastic bonded, cast, and moldable plastic explosives. Specifically designed experiments were used to study the initiation process of each explosive family with embedded shock sensors and optical diagnostics. The experimental portion of this model development began with a study of PBXN-5 to develop DMGIR model coefficients for the rigid plastic bonded family, followed by studies of the cast, and bulk-moldable explosive families, including the thermal effects on initiation for the cast explosive family. The experimental results show an initiation mechanism that is related to impulsive energy input and material damage, with well defined initiation thresholds for each explosive family. These initiation details will be used to extend the predictive capability of the DMGIR model from the rigid family into the cast and bulk-moldable families. © 2010 Society for Experimental Mechanics Inc.

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A detonating explosive in contact or in close proximity with a material can impart an extremely strong impulsive load that nucleates the growth of cracks and voids at multiple sites simultaneously. This paper uses experimental results to show void nucleation and fractures that developed during the impulsive loading of a mild steel plate. Additionally, a numerical simulation that matches the experimental results shows the the progression, amplitude, and interaction of the stress wave as it propagates through the thickness of the plate. Through this simulation, one can see where the fractures might initiate due to large triaxial stresses. Finally, the paper discusses the possible mechanisms that initiate and generate the fracture surfaces found in the mild steel plate experiment.