Impact initiation of an explosion

Abstract

1. A method is proposed for initiating an explosion by the impact of a plate against the surface of a charge. The accuracy of the method is characterized by deviation of the velocity of the plate from the critical value by \+-2 m/sec. When the critical velocity is exceeded by 2 m/sec there will be an explosion in every case, whereas if the velocity is 2 m/sec less than the critical value there will be 100% failures. The method makes it possible to investigate the initiation process in all its phases and over a wide range of variation of velocity and mass of the impacting body. 2. The different stages of explosive decomposition-smoke formation, flashing, combustion with a luminous flame along the front, deflagration (rapid combustion), focal combustion (hot spots), and explosion\3-can be observed, depending on the impact force, that is, on the quantity of heat introduced by the impact. The initiation time was determined. 3. The formation of hot spots in the explosion initiation process was detected for the first time. The increase in the number and size of these hot spots with time was investigated. In a TNT charge the hot spots had a diameter of 0.4 mm, and in RDX-0.35 mm. Two processes of focal combustion were discovered: a) the hot spots remain almost constant in diameter, but their number increases rapidly; b) individual hot spots develop which increase rapidly in diameter (the number remaining constant). Both processes of focal combustion occur simultaneously in the same experiment.