Shock initiation of an explosion. II. Critical energy

Summary

• 1) The critical energy for initiating an explosion in TNT, introduced by the impact of a plate, has been determined. Critical velocities and the corresponding critical energies have been obtained for sample densities of 1.43, 1.54, and 1.60 g/cm³.

• 2) Critical plate velocities have been, determined for various explosives: TNT, RDX, tetryl, picric acid, and TNT-RDX mixtures (50∶50). The accuracy of determination is defined by deviation of the plate velocity from the critical value by ±0.5%. An increase in critical velocity by 0.5% gives 100% explosions and a decrease by 0.5% gives 100% failures (no explosion).

• 3) The shock velocity has been measured and the principal dynamic characteristics at the shock front determined for TNT with the densities given above (p, V, u, E−E_o). The relationship between the velocity of the material and the critical plate velocity has been obtained

  $$\begin{gathered} u = \frac{a}{{a + \rho _0 D}} \cdot \mathcal{W},E - E_0 = \frac{{a^2 }}{{(a + \rho _0 D)^2 }} \cdot \frac{{w^2 }}{2}, \hfill \\ a = 0.4 \cdot 10^7 [g \cdot cm^{ - 2} \cdot \sec ^{ - 1} ], \hfill \\ \end{gathered}$$

  which enables one to make a quantitative analysis of the effect on the critical energy (or the velocity of the material u) of the velocity and mass of the impact plate, and also of the density of the explosive investigated. It follows from Eq. (4) that the energy of compression (E−E_o) is determined only by the plate velocity (w) and is independent of its mass, which does not enter into the equation.