Cavity Collapse Ignition of Composition B in the Launch Environment
ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
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A series of experiment was conducted in which controlled cavities in cast Composition B are subjected to deformation both with and without simultaneous air compression as well as air compression without deformation. Dimple tests were designed to accomplish this. There are three variations of the dimple test. In the standard dimple test a cylindrical cavity or dimple of controlled depth and diameter is cast into one end of the explosive sample. In another variation, vacuum hardware is used. In a third variation, the dimple is cast into a piece of Dow Corning Sylgard 182 which is placed in contact with an undimpled explosive sample. In the vaccume dimple test, only air compression heating occurs. Both heating mechanisms are combined in the standard dimple testing. Thus far we have found that, when the air compression and deformation heating mechanism are combined, the dominant ignition mechanism is compressive heating of air strongly influenced by the cavity collapse geometry and possibly by alteration of the state of the explosive surface. The hypothesis of a transition form axial to radial cavity collapse with increasing dimple depth seems to explain the observed behavior. Deformation heating is the dominant mechanism only for high aspect ration dimples. Keywords Premature ignition, High explosives, Explosive sensitivity, Setback, Adiabatic compression, Compressive heating, Deformation heating.
- Ammunition and Explosives
- Combustion and Ignition