Studies of the TNT equivalence of silver azide charges |
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| Authors: | Email author" target="_blank">H?KleineEmail author JM?Dewey K?Ohashi T?Mizukaki K?Takayama |
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| Institution: | (1) School of Aerospace and Mechanical Engineering, University College, University of New South Wales/Australian Defence Force Academy, ACT 2600 Canberra, Australia;(2) Department of Aeronautics and Space Engineering, Tohoku University, 980-8579 Sendai, Japan;(3) Department of Physics and Astronomy, University of Victoria, V8W 3P6 Victoria, BC, Canada;(4) Department of Physics and Astronomy, Showa Kinzoku Kogyo Co. LTD, 309-1211 Ibaraki, Japan;(5) Shock Wave Research Center, Institute of Fluid Science, Tohoku University, 980-8577 Sendai, Japan;(6) 1st Research Center, Technical Research and Development Institute, Japan Defence Agency, 153-8630 Tokyo, Japan |
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| Abstract: | Schlieren photographs and shadowgrams have been evaluated to provide the radius-time histories of the shocks generated by explosions of silver azide charges with masses in the milligram range. Series of photographs of the flow field produced by a single explosion were obtained with an image converter camera, to yield a time history of the shock trajectory. These data were used to determine the shock Mach number and subsequently the peak hydrostatic overpressure as a function of radius. The pressure-radius profile was compared with that from a unit charge of TNT to determine the TNT equivalence of silver azide as a function of peak pressure and of distance from the centre of a
silver azide charge. The shock radius and time were also determined from single-shot visualizations of silver azide explosions. A new method of analysis was developed so that the charge mass and the TNT equivalence of an explosion could be derived from such a single radius-time measurement. The TNT equivalence factor for silver azide was shown to vary from 0.3 to 1.4, depending on the distance from the centre of the explosion. This agrees well with the generally reported equivalence factor of about 0.4 (Baker et al. 1983), which was probably based on the chemical composition of the material. Procedures are described by which the TNT equivalence factor can be calculated at any specified distance from a silver azide charge of known mass, or from a measurement of the shock radius and time, even when the charge mass is not known. This factor can then be used to determine the physical properties of the TNT blast wave which best describe those from the silver azide charge at the specified distance. A further result of these studies was that the scaling laws for blast waves, whose validity has been verified for charge masses ranging from a few grams to hundreds of tons, i.e., for charge masses varying over more than nine orders of magnitude, also apply for charges with masses of the order of one milligram.Received: 7 April 2003, Accepted: 1 July 2003, Published online: 5 August 2003 |
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| Keywords: | Blast waves TNT equivalence Milligram explosive charges Density-sensitive flow visualization techniques |
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