Rate of Reaction of TNT in Detonation by Direct Pressure Measurements

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Abstract
A description of an experimental method of obtaining pressure‐time data for the decomposition of coarse TNT following partial detonation is given. This method consisted of photographing (with a streak camera) the displacement of a slug shot from a smooth bore cannon. The velocity and acceleration of the slug were obtained by numerical differentiation of the displacement‐time data derived from the photograph. Pressure‐time curves were obtained which exhibited pressure maxima at times that were dependent upon the particle size of the TNT detonated in the cannon. Peak pressures for TNT of 4—6 standard mesh particle size occurred between 140—200 μsec, peak pressures for 8—10 mesh occurred between 115—140 μsec, and pressure maxima for ``fine'' TNT occurred between 50—70 μsec. The pressure‐time curves were analyzed, and reaction times of the coarse TNT were calculated by two different methods. One method yielded a value of the reaction time for each pressure‐time coordinate and the other a reaction time in terms of the time at which maximum pressure occurred. The results obtained by these two methods were not the same. However, when corrections were made for gas leakage from the cannon, rather good agreement resulted. The most probable value computed (after leakage corrections were made) for the 4—6 TNT was found to be about 300 μsec and for the 8—10 TNT about 200 μsec. On the basis of these reaction times the grain erosion velocity for the TNT in the cannon was evidently much greater than linear burning rates at the same pressure obtained experimentally for explosive deflagration.

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