ON THE VIOLENCE OF THERMAL-EXPLOSION IN SOLID EXPLOSIVES

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 (TATE ) were heated at rates varying from 2 degrees C/min to 3.3 degrees C/h . Fourteen of the cylinders were hallow, and inner metallic liners wit h small heaters attached were used to produce uniform temperatures jus t prior to explosion. A complex thermocouple pattern was used to measu re the temperature history throughout the charge and to determine the approximate location where the runaway exothermic reaction first occur red. The violence of the resulting explosion was measured using veloci ty pin arrays placed inside and outside of the metal confinement cylin ders, flash x-rays, overpressure gauges, and fragment collection techn iques. Five cylinders were intentionally detonated for violence compar isons. 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 decomposi tion models. The acceleration of the confining metal cylinders by the explosion process was accurately simulated using a two-dimensional pre ssure dependent deflagration reactive how hydrodynamic model. The most violent HMX thermal explosions gradually accelerated their outer case s to velocities approaching those of intentional detonations approxima tely 120 mu s after the Onset of explosion. The measured inner cylinde r collapse velocities from thermal explosions were considerably lower than those produced by detonations. In contrast to the HMX thermal rea ctions, no violent thermal explosions were produced by the TATE-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 plat e. (C) 1997 by The Combustion Institute.