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Potential Metallographic Technique for the Investigation of Pipe Bombings

NCJ Number
Journal of Forensic Sciences Volume: 48 Issue: 5 Dated: September 2003 Pages: 945-960
Graham A. Walsh M.S.; Osman T. Inal Ph.D.; Van D. Romero Ph.D.
Date Published
September 2003
16 pages
This study sought to develop a metallographic method for investigating pipe bombings.
Eight fillers that consisted of five high explosives and three propellants were tested in pipes composed of ASTM A53 galvanized steel, AISI 304L stainless steel, and 6061-T6 aluminum. The explosives used were ANFO, Composition C4, C6 detasheet, nitroglycerine-based dynamite, and flake TNT. The propellants used were FFFFg black powder, Red Dot smokeless powder, and Turbo Fuel A. The fragments from these tests were collected in soft catch packets, which consisted of 24 rectangles of Celotex, 33x66cm, bound together to form a packet 33-cm thick. The resulting microstructures and hardness of the fragments were examined in an effort to correlate an explosive property, such as the detonation velocity, to a material response. The three main shock properties of interest in this study were the detonation velocity of the explosives, the generated pressure, and shock heating, which are functions of the metal/explosive combinations being studied. The post-blast microstructure, hardness, and, in the case of 304L, martensite content showed a sharp increase followed by a plateau as the shock pressure and detonation velocity increased. Although this technique of investigation is essentially qualitative, further research could enable these methods to be used in providing a range of detonation velocities and pressures of an explosive fill used in a pipe bomb. This could in turn be useful as a screening process for chemical examinations. 6 tables, 19 figures, and 30 references


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