SHOCK EVOLUTION AFTER SHAPED CHARGE JET IMPACT AND ITS RELEVANCE TO EXPLOSIVE INITIATION

When a shaped charge jet impacts a target containing explosive, the ex plosive may be initiated by one of three shocks: the impact shock, a b ow shock that forms in the inert plate covering the exlosive, or a bow shock that forms in the explosive. In this paper, numerical calculati ons are used to determine how thick the cover plate must be to prevent initiation by the impact shock and how much time (or distance) is req uired to form a bow shock in the explosive. The results show that the cover plate must be from 4 to 12 jet diameters (depending on jet veloc ity) thick to sufficiently attenuate the impact shock so that it will not cause initiation in a common secondary explosive. For a 7-km/s cop per jet, a distance of about 8 jet diameters was required to form a bo w shock in the explosive. This corresponds well to experimental data r eported elsewhere.