ON THE EFFECT OF GRAIN-SIZE ON SHOCK SENSITIVITY OF HETEROGENEOUS HIGH EXPLOSIVES

Analysis of available data on dependence of the critical detonation di ameter d(cr) of various heterogeneous condensed explosives on mean siz e of grains and voids demonstrated that in many cases surprising corre lations between d(cr) and the initial specific surface area of heterog eneous explosives A(o) exist, namely, d(cr) = alpha(1) + alpha(2)/A(o) or 1/d(cr) = beta(1) + beta(2)A(o). The run distance to detonation in wedge test with sustained strong shock of constant amplitude also lin early correlates with 1/A(o), i.e. L-P=(Const) = gamma(1) + gamma(2)/A (o). At the same time, the shock sensitivity reversal effect is often observed when grain size of HE is reduced. Apart from that Moulard (19 89) found that detonation critical diameter of plastic bonded explosiv e with mono- and bimodal RDX grain size distribution depends nonmonoto nously on mean grain size, Complicated dependence of shock sensitivity of heterogeneous explosives on their specific surface area can be exp lained based on comparison of the critical hot spot size a(P) at give n characteristic pressure behind shock wave P with the mean heterogene ity size (a) over bar. At high characteristic pressure (relative to th e critical ignition pressure) a is small compared with (a) over bar a nd all specific surface area of heterogeneous explosive is available f or the hot spot growth process in accordance with the grain burn conce pt. However, when characteristic pressure of shock wave decreases, a( P) increases and can become comparable with (a) over bar. In this case only relatively large potential hot spots (with size a > a) can resu lt in self-supported hot spot growth process and shock sensitivity is controlled by the specific surface area which corresponds to only larg er heterogeneities and can be significantly smaller than initial speci fic surface area.