Craig M. Tarver

Detonation waves in triaminotrinitrobenzene

Fabry–Perot laser interferometry is used to obtain nanosecond time resolved particle velocity histories of the free surfaces of copper, tantalum, or magnesium disks driven by detonating triaminotrinitrobenzene (TATB)-based charges and of the interfaces between detonating TATB and transparent salt crystals. Detonation reaction zone profiles are measured for self-sustaining detonation waves propagating through various thicknesses of LX-17 (92.5% TATB and 7.5% KelF binder) and pure ultrafine particle size TATB. The experimental records are compared to particle velocity histories calculated with the DYNA2D hydrodynamic code using the ignition and growth reactive flow model. The calculations yield excellent agreement with the experimental records for LX-17 using an unreacted von Neumann spike pressure of 33.7 GPa, a reaction rate law which releases 70% of the chemical energy within 100 ns, and the remaining 30% over 300 additional ns, and a reaction product equation of state fit to cylinder test and supracompr...

Detonation waves in pentaerythritol tetranitrate

Fabry–Perot laser interferometry was used to obtain nanosecond time resolved particle velocity histories of the free surfaces of tantalum discs accelerated by detonating pentaerythritol tetranitrate (PETN) charges and of the interfaces between PETN detonation products and lithium fluoride crystals. The experimental records were compared to particle velocity histories calculated using very finely zoned meshes of the exact dimensions with the DYNA2D hydrodynamic code. The duration of the PETN detonation reaction zone was demonstrated to be less than the 5 ns initial resolution of the Fabry–Perot technique, because the experimental records were accurately calculated using an instantaneous chemical reaction, the Chapman–Jouguet (C-J) model of detonation, and the reaction product Jones–Wilkins–Lee (JWL) equation of state for PETN detonation products previously determined by supracompression (overdriven detonation) studies. Some of the PETN charges were pressed to densities approaching the crystal density and e...

Sensitivity of 2,6-Diamino-3,5-Dinitropyrazine-1-Oxide

ABSTRACT The thermal and shock sensitivities of plastic bonded explosive formations based on 2,6-diamino-3,5-dinitropyrazine-1-oxide (commonly called LLM-105 for Lawrence Livermore Molecule #105) are reported. The One-Dimensional Time to Explosion (ODTX) apparatus was used to generate times to thermal explosion at various initial temperatures. A four-reaction chemical decomposition model was developed to calculate the time to thermal explosion versus inverse temperature curve. Three embedded manganin pressure gauge experiments were fired at different initial pressures to measure the pressure buildup and the distance required for transition to detonation. An Ignition and Growth reactive model was calibrated to this shock initiation data. LLM-105 exhibited thermal and shock sensitivities intermediate between those of triaminotrinitrobenzene (TATB) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazine (HMX).

On the violence of thermal explosion in solid explosives

Abstract Twenty large scale experiments were conducted to determine the levels of violence of thermal explosions produced by various confinement and heat flow conditions. Heavily confined cylinders of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and triaminotrinitrobenzene (TATB) were heated at rates varying from 2°C/min to 3.3°C/h. Fourteen of the cylinders were hollow, and inner metallic liners with small heaters attached were used to produce uniform temperatures just prior to explosion. A complex thermocouple pattern was used to measure the temperature history throughout the charge and to determine the approximate location where the runaway exothermic reaction first occurred. The violence of the resulting explosion was measured using velocity pin arrays placed inside and outside of the metal confinement cylinders, flash x-rays, overpressure gauges, and fragment collection techniques. Five cylinders were intentionally detonated for violence comparisons. The measured temperature histories, times to explosion, and the locations of first reaction agreed closely with those calculated by a two-dimensional heat transfer code using multistep chemical decomposition models. The acceleration of the confining metal cylinders by the explosion process was accurately simulated using a two-dimensional pressure dependent deflagration reactive flow hydrodynamic model. The most violent HMX thermal explosions gradually accelerated their outer cases to velocities approaching those of intentional detonations approximately 120 μs after the onset of explosion. The measured inner cylinder collapse velocities from thermal explosions were considerably lower than those produced by detonations. In contrast to the HMX thermal reactions, no violent thermal explosions were produced by the TATB-based explosive LX-17. A heavily confined, slowly heated LX-17 test produced sufficient pressure to cause a 0.1 cm bend in a 2 cm thick steel plate.

On the low pressure shock initiation of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine based plastic bonded explosives

In large explosive and propellant charges, relatively low shock pressures on the order of 1–2 GPa impacting large volumes and lasting tens of microseconds can cause shock initiation of detonation. The pressure buildup process requires several centimeters of shock propagation before shock to detonation transition occurs. In this paper, experimentally measured run distances to detonation for lower input shock pressures are shown to be much longer than predicted by extrapolation of high shock pressure data. Run distance to detonation and embedded manganin gauge pressure histories are measured using large diameter charges of six octahydro-1,3,5,7–tetranitro-1,3,5,7-tetrazocine (HMX) based plastic bonded explosives (PBX’s): PBX 9404; LX-04; LX-07; LX-10; PBX 9501; and EDC37. The embedded gauge records show that the lower shock pressures create fewer and less energetic “hot spot” reaction sites, which consume the surrounding explosive particles at reduced reaction rates and cause longer distances to detonation....

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

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 measu...

Effect of confinement and thermal cycling on the shock initiation of LX-17

Abstract The shock initiation of the insensitive high explosive LX-17, which contains 92.5% triaminotrinitrobenzene (TATB) and 7.5% Kel-F binder, was studied under two simulated accident conditions: initially confined charges were heated to 250°C and shocked; and unconfined charges were thermally cycled between 25° and 250°C and shocked. Previous research on unconfined TATB-based explosives heated to 250°C revealed increased shock sensitivity. This increase was attributed to both the increased porosity caused by the unsymmetrical thermal expansion of TATB, which resulted in more hot spot ignition sites, and the faster growth of hot spot reactions due to the increased surrounding temperature. In this study, aluminum confinement was used to decrease the thermal expansion of LX-17. The shock sensitivity of confined LX-17 at 250°C was observed to be less than that of unconfined charges at 250°C but greater than that of unconfined, ambient temperature LX-17. The thermal cycling results showed that the LX-17 heated to 250°C and then shocked at 25°C was more sensitive than pristine LX-17, because irreversible growth had produced more ignition sites. LX-17 held at 250°C for an hour or fired at 250°C after two thermal cycles did not appear to be significantly more shock sensitive than LX-17 heated to 250°C and shocked immediately. Therefore it is unlikely that TATB is thermally decomposing into less stable intermediate species at 250°C. The Ignition and Growth reactive flow model for shock initiation of LX-17 was normalized to these experimental results to provide a predictive capability for other accident scenarios that cannot be tested directly.

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

A model comparison with measurements for the thermal, chemical, and mechanical behaviors in a thermal explosion experiment is presented. 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 (ALE3D) code that can handle a wide range of time scales that vary from a structural to a hydrodynamic time 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 octahydrotetranitrotetrazine (HMX)-based explosives, LX-04 and LX-10, are considered, whose chemical-thermal-mechanical models are constructed based on measurements of thermal and mechanical properties along with small-scale thermal explosion measureme...

Detonation Reaction Zones in Condensed Explosives

Experimental measurements using nanosecond time resolved embedded gauges and laser interferometric techniques, combined with Non‐Equilibrium Zeldovich ‐ von Neumann ‐ Doling (NEZND) theory and Ignition and Growth reactive flow hydrodynamic modeling, have revealed the average pressure/particle velocity states attained in reaction zones of self‐sustaining detonation waves in several solid and liquid explosives. The time durations of these reaction zone processes are discussed for explosives based on pentaerythritol tetranitrate (PETN), nitromethane, octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX), triaminitrinitrobenzene(TATB) and trinitrotoluene (TNT).

Shock initiation experiments with ignition and growth modeling on low density HMX

Shock initiation experiments on low density (~1.2 and ~1.6 g/cm3) HMX were performed to obtain in-situ pressure gauge data, characterize the run-distance-to-detonation behavior, and provide a basis for Ignition and Growth reactive flow modeling. A 101 mm diameter gas gun was utilized to initiate the explosive charges with manganin piezoresistive pressure gauge packages placed between packed layers (~1.2 g/cm3) or sample disks pressed to low density (~1.6 g/cm3). The measured shock sensitivity of the ~1.2 g/cm3 HMX was similar to that previously measured by Sheffield et al. and the ~1.6 g/cm3 HMX was measured to be much less shock sensitive. Ignition and Growth model parameters were utilized that yielded good agreement with the experimental data at both initial densities.