Growth of Creamed TNT on Thermal Cycling
MATERIALS RESEARCH LABS ASCOT VALE (AUSTRALIA)
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Growth or irreversible thermal expansion of creamed TNT on thermal cycling is described. Growth of TNT charges appears to correlate with the quantity of impurities present, and increases linearly with the maximum temperature expereienced in a manner which suggests the existence of a critical upper temperature which must be exceeded for any growth to occur. This temperature is close to the eutectic temperature for a ternary mixture of 2,4,6- TNT, 2,3,4-TNT and 2,4-DNT. On the basis of these results and changes in the external appearance of TNT specimens subjected to thermal cycling, a ratchet mechanism to account for growth is proposed, in which the stresses generated by anisotropic thermal expansion of TNT are relieved above the eutectic temperature by a mass transfer process such as grain boundary sliding or dynamic recrystallisation.
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