GROWTH OF BURNING TO DETONATION IN LIQUIDS AND SOLIDS
CAMBRIDGE UNIV (UNITED KINGDOM) CAVENDISH LAB
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Studies were made of the growth of burning to explosion in a homogeneous thin film of nitroglycerine about 0.1mm thick and 3 cm in diameter which is confined between two solid discs and initiated as its centre by an electric spark. Reaction grows from the initiation site first as an accelerating burning, which advances into a region of bubble-free liquid that is under high pressure generated by the central burning. Standard shocks were applied to single crystals of P.E.T.N., R.D.X., H.M.X., and silver azide by explosive detonators separated by thin baffles from the crystals under study. The processes leading to fragmentation, deflagration and detonation have been followed at microsecond framing rates using a Beckman and Whitley high-speed camera. The shock strengths were found either by using piezocrystals or by measuring separately shock velocities in water or lucite. Research on the fracture of inert crystals was made. Fracture was followed both by high-speed photography, and an ultrasonic technique. The fracture work was with magnesium oxide and lithium fluoride. The maximum velocities of cleavage in all these materials have been recorded this is of theoretical interest. The appearance of a fracture surface varies markedly along its course. Factors which affect the surface markings include the dislocation density of the material, the velocity of fracture and stress waves. The theoretical work was concerned with studies of the explosion process from the viewpoint of thermal explosion theory.
- Combustion and Ignition