Author Description

The test developed at the Materials Research Laboratories to assess the sensitivity of both covered and bare explosives to the copper jet from 38 mm diameter shaped charge is described in detail. Sensitivities of covered explosives were measured in terms of the critical thickness of a steel cover in contact with the explosive that allowed detonation in 50% of a series of firings. Bare explosive sensitivities were similarity assessed except that the steel barrier was separated from the explosive by an air gap. The steel cover thickness was calibrated in order that sensitivity values can be expressed as a function of the critical jet velocity at the detonation/failure threshold. Some explosive sensitivity values are reported for both the covered and bare configurations. Generally, explosives in the bare state were found to be significantly more sensitive than when covered. A method of instrumenting the test with multiple flash radiography is described and the mechanisms of jet initiation of explosives are summarized.