Ignition and burning mechanisms of RDX/HMX particles subjected to drop-weight impact

The mechanical and chemical response of explosives under low velocity impact is the basis for the evaluation of their sensitivity. The drop-weight impact apparatus equipped with the optical photography was used to achieve a frequency of 150 thousand seconds of real time observation. It was capable of distinguishing the samples of "Go" or "no Go" and observing such characteristics of deformation, crushing and breakage, jetting, ignition and combustion evolution, of RDX and HMX particles under low velocity impact. The selected photographic frames show that ignition occurred in the partially melted RDX phase. But for the HMX particles, ignition mainly occurred in the solid phase. A violent jetting phenomenon often occurs before the reaction of combustion. The occurrence of jetting primarily results from the energy released by gaseous products, which push the pulverized or melted explosives splash. The response characteristics of single and multiple granular explosives were compared. Because of the interaction of the hot spots broken, the combustion reaction of the particles is more intense than that of the single particles. The size ratio of the image to the actual length can be used to estimate combustion wave propagation velocity in each case, which is very suitable for characterizing the intensity of the macro-combustion reaction.