METAL JET INITIATION OF BARE AND COVERED EXPLOSIVES; SUMMARY OF THE MECHANISM, EMPIRICAL MODEL AND SOME APPLICATIONS

The paper summarises an investigation aimed at determining the mechanisms and factors that control the sensitivity of bare and covered explosives to attack from shaped charge jets. The mechanism of the initiation process has been studied using multiple flash X-radiography. A test is described that assesses the sensitivity of explosives to a jet in terms of the thickness of a steel barrier that will allow detonation in 50 % of the firings. The general mechanism proposed is illustrated by systems that produce strong initiating shocks, weak initiating shocks and failure shocks in Composi.tion B. An empirical model is described which calculates the pressure of jet impact, and follows the shock produced through the steel covering and into the explosive. Calculated shock pressures and corresponding velocities in Composition B are in good agreement with those determined experimentally. The shock pressure profile through the steel barrier in the empirical model is used to convert the measured critical barrier thicknesses to the critical initiating shock pressures fo