Bulletin of the American Physical Society
2005 14th APS Topical Conference on Shock Compression of Condensed Matter
Sunday–Friday, July 31–August 5 2005; Baltimore, MD
Session Y1: Energetic Materials VIII |
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Chair: Kevin Vandersall, Lawrence Livermore National Laboratory Room: Hyatt Regency Constellation B |
Friday, August 5, 2005 8:00AM - 8:15AM |
Y1.00001: Ab-initio Prediction of Impact Sensitivity Peter Haskins, Malcolm Cook, Andrew Wood, Helen Flower An important goal of the energetic materials community has been to develop a first-principles technique for the prediction of sensitivity. There have been a number of attempts by previous researchers to develop a simple criterion that might achieve this, but they have only been partially successful. Here we review previous attempts and propose some alternative approaches. These are based, variously, on ab-initio quantum chemistry determinations of activation barriers, crystal packing predictions of the lattice energy, and estimates of the reaction energy. Using these basic parameters we have attempted to obtain correlations with experimental drop weight impact data for a wide range of explosives. We compare and contrast the methods and draw conclusions with regard to the most important factors. Finally, we use the best correlations to make predictions for novel, as yet un-synthesised, poly-nitrogen materials. [Preview Abstract] |
Friday, August 5, 2005 8:15AM - 8:30AM |
Y1.00002: Frictional heating and ignition of energetic materials Peter Dickson, Gary Parker, Laura Smilowitz, Blaine Asay, Jonathan Zucker For many years, powder friction tests have been an integral part of explosives sensitivity and safety testing. More recently, oblique impact tests have been used in the hazard assessment of monolithic charges. However, these tests are simply threshold tests for reaction, and relatively little work has been done to try to examine the processes that lead to frictional heating and ignition of energetic materials. We report the results from a series of experiments in which energetic materials and simulants are subjected to frictional heating under closely-controlled conditions (normal load, sliding speed, grit quantity and composition, substrate). The response of the energetic material (or simulant) and grit, if present, is observed by optical and infrared high-speed photography to determine the nature of the interactions between the test material, grit and substrate, and the mechanisms by which the energetic material may be heated to ignition. [Preview Abstract] |
Friday, August 5, 2005 8:30AM - 8:45AM |
Y1.00003: On the Detonation of an Explosive by the Shock Resulting from Projectile Impact Peter Lee, John Curtis, John Mills A model that addresses the shock physics resulting from high velocity projectile normal impact upon a layered target containing explosive, with a view to determining whether detonation occurs, is presented. Unlike many earlier entirely empirical criteria for shock-induced detonation, the formulation includes a simple treatment of the resultant chemistry in the explosive, while retaining the benefits of an analytical, as compared with hydrocode, formulation. The impact on the confined explosive generates shocks in the front target layer and in the projectile. The Rankine-Hugoniot relations are used to calculate the characteristics of these shocks and then to determine the shock propagation into the subsequent target layers. In particular the mechanical shock contribution to the internal energy in the explosive, is calculated. The total rate of supply of internal energy to explosive is then determined by the addition of an expression for the heating that would result from the chemical reaction, drawing upon the Lee and Tarver explosive burn model. Based on the total rate of energy supply and some asymptotic considerations, a semi-empirical detonation criterion is postulated. Predictions with the new model are in good agreement with the corresponding experimental data. [Preview Abstract] |
Friday, August 5, 2005 8:45AM - 9:00AM |
Y1.00004: Expanded Small-Scale Shock Reactivity Test Richard Granholm, Harold Sandusky Explosives react from a strong shock, even in quantities too small for detonation. The potential for a new material to be an explosive can be evaluated from this shock reactivity. The recently developed small-scale shock reactivity test (SSRT)\footnote{H. W. Sandusky, R. H. Granholm, D. G. Bohl, ``Small-Scale Shock Reactivity Test,'' NSWC Technical Report (in publication), Naval Surface Warfare Center, Indian Head, MD 20640} uses very high confinement to allow prompt reactions to occur in less than half-gram samples well below critical diameter, with the reactions quantified by a dent in a soft aluminum witness block. This test has been expanded to simultaneously measure both early and late-time reactions from a single sample subjected to the output from an RP-80 detonator. The sample apparatus is further confined within a small chamber instrumented with a pressure gage for internal air blast. This provides a measure of late-time reactions, such as from fuel/air combustion. Results are shown from several simultaneous early- and late-reaction measurements. [Preview Abstract] |
Friday, August 5, 2005 9:00AM - 9:15AM |
Y1.00005: LX-04 Violence Measurments: Steven Tests Impacted By Projectiles Shot From A Howitzer Gun Steven K. Chidester, Kevin S. Vandersall, Lori L. Switzer, Daniel W. Greenwood, Craig M. Tarver Characterization of the reaction violence of LX-04 explosive (85{\%} HMX and 15{\%} Viton by weight) was obtained from Steven Impact Tests performed above the reaction initiation threshold. A 155 mm Howitzer propellant driven gas gun was used to accelerate the Steven Test projectiles in the range of approximately 150-300 m/s to react (ignite) the LX-04 explosive. Blast overpressure gauges, acoustic microphones, and high-speed photography characterized the level of high explosive reaction violence. A detonation in this velocity range was not observed and when comparing these results (and the Susan test results) with that of other HMX based explosives, LX-04 has a more gradual reaction violence slope as the impact velocity increases. The high binder content (15{\%}) of the LX-04 explosive is believed to be the key factor to the lower level of violence. This work was performed under the auspices of the U. S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48. [Preview Abstract] |
Friday, August 5, 2005 9:15AM - 9:30AM |
Y1.00006: Mechanical Behavior of TNAZ/Hytemp Explosives During High Acceleration Y. Lanzerotti, J. Sharma The mechanical behavior of TNAZ/Hytemp (1,3,3- trinitroazetidine/polyacrylate) explosives subjected to high acceleration has been studied in an ultracentrifuge. Pressed plastic-bonded TNAZ/Hytemp was studied as a function of the percentage of Hytemp at -10\r{}C and 25\r{}C. The percentage of Hytemp in the samples varied from 1\% to 2\%. Failure occurs when the shear or tensile strength of the explosive is exceeded. The fracture acceleration of pressed plastic-bonded TNAZ/Hytemp decreases with the increasing percentage of Hytemp in the explosive at -10\r{}C and 25\r{}C. The fracture acceleration of pressed plastic-bonded 98%/2\% TNAZ/Hytemp at 25\r{}C is about 1/3 that at -10\r{}C. [Preview Abstract] |
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