LeRoy G. Green

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.

Apparent Molar Volumes of Salts and Metals In Liquid Ammonia at 0

Apparent molar volumes of some metals and salts in dilute liquid ammonia solutions at 0° have been measured with a direct‐mixing dilatometer. There is little volume change involved in dissociation of diamagnetic metal species, but a large volume decrease results from dissociation of ion‐pairs in salt solutions. Volumes are estimated for single ions and the solvated electron.

Heat of Formation of Deuterated Diborane

The head of decomposition of B/sub 2/D/sub 6/ was measured by explosion in mixtures with stibine. DELTA H/sub 298/ for the reaction 2B/sub (g)/+ 6H/sub (g) = B/sub 2/H/sub 6(g)/ was obtained as B/sub 2/H/sub 6/, -575.44, and ial energy functions of the isotopic molecules are very similar. The heats of decomposition of B/sub 2/D/sub 6/ are tabulated. (P.C.H.)

Heats of Solution of Alkali Metals in Liquid Ammonia at 25

Heats of solution in ammonia at 25° have been measured for Li, Na, and K at concentrations down to 0.005 M, and for Na in the presence of NaI. Dilution is endothermic, and the heat of dilution is greater in the presence of added Na ion; these results support the Becker‐Lindquist‐Alder theory of the solutions.

Improvements in the Signal Fidelity of the Manganin Stress Gauge

The manganin stress gauge has been and still is the primary diagnostic tool for measuring longitudinal stresses in materials shocked from 10 to 400 kb in one‐dimensional (1D) uniaxial strain experiments [1]. Its simple and robust design allows this gauge to survive in harsh environments. The manganin gauge has several limitations. For example, in the eventual failure mode, the manganin gauge has a reputation of being a noise generator to the remaining functioning manganin gauges at different lagrangian positions in the experiment. The manganin gauge also demonstrates undesirable signal effects when the front edge of the incoming shock first makes contact. These two limitations and the experiments for the mediation of these effects on shock experiments will be presented in this paper. Our ultimate goal is to provide practical manganin gauging that has true fast rise time and little or no noise generation on failure in explosive detonation waves. A device was found that mitigates the noise generation withou...

Pressure Wave Measurements in Cylinders of Detonating LX‐17

Manganin gauges with temporal resolution of less than 75 ns were used to measure the detonation wave pressure profile in a right cylinder of LX‐17 (TATB/Kel‐F: 92.5/7.5 wt.%). Three gauges at different Lagrange locations were on the centerline of the 5.08 cm diameter cylinder at distances greater than four times its diameter from the boosted end. At the last gauge plane, seven gauges were placed at the same Lagrange position but spaced radially across the cylinder diameter. Wave curvature and effects of lateral strain in these gauges were measured.