The critical thresold for shock initiation in explosives

There are a series of observations of explosive response that remain difficult to explain using the present approaches. In particular, consistent explanations for phenomena such as dead pressing, observations of electrical influences on initiation and requirements for an unphysical pressure dependence of the reaction rate in detonation suggest another approach may be necessary. One approach explicitly considers the stress threshold required to shock an explosive so that it runs to full detonation. At present it is assumed that a reaction zone within an explosive is formed of localised burning regions that increase in density as pressure is increased. However, a series of burn rate experiments and shock investigations of the shock response of explosives indicate a critical stress level at which response changes. The stress at which the theoretical shear strength is exceeded is called the Weak Shock Limit and represents the gateway to the strong shock region. It is hypothesised here that there is a change in physical properties above the weak shock limit that allows the reaction to move from localised burning to homogeneous reaction. This work presents this new approach and tests a range of implications that may be tested in further experiments. If explicitly proven, the weak shock limit is a vital quantity to consider for the safe handling of energetic materials.