The Legacy of Manfred Held with Critique
NAVAL POSTGRADUATE SCHOOL MONTEREY CA DEPT OF PHYSICS
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Impact initiation of explosives is one of the more frequent referred to topics of Prof Dr Manfred Held, an internationally renown ballistician, who passed away in 2011. This thesis includes a cross-referenced bibliography of most of his published papers and patents and focuses on one of his more frequently referred topics, the impact of initiation of explosives. Experimental data from impacts against bare explosives, covered and confined with and without air gaps, and explosive and projectile dimensions are first used to validate finite difference computations required to extend and properly evaluate the database. The analyses include explosives PBX 9404, Comp. B 6535, Octol 7030, H6, TNT and projectiles aluminum, steel, copper, tantalum of much varied properties and sensitivities. Assuming that close examination of the experimental data proposed by Held and others to rate the relative threshold sensitivity of explosives to impact incl., v2d, u2d, v2d and 12v2d deviate significantly from constancy, in some cases greater than 50 percent. It is found that the product of interfacial impact pressure and well-defined projectile diameter is a much more reliable predictor of the impact sensitivity of a bare explosive based on the smaller deviation from mean values relative to the aforementioned terms. Importantly, this energy term takes into account the density and Hugoniot properties of both impactor and explosive.