Bulletin of the American Physical Society
15th APS Topical Conference on Shock Compression of Condensed Matter
Volume 52, Number 8
Sunday–Friday, June 24–29, 2007; Kohala Coast, Hawaii
Session B6: Detonation Properties |
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Chair: Terry Salyer, Los Alamos National Laboratory Room: Fairmont Orchid Hotel Promenade I/II |
Monday, June 25, 2007 10:30AM - 11:00AM |
B6.00001: Microenergetics: Combustion and Detonation at Sub-Millimeter Scales Invited Speaker: At Sandia National Laboratories, we have coined the term ``microenergetics'' to describe sub-millimeter energetic material studies aimed at gaining knowledge of combustion and detonation behavior at the mesoscale.[1] Our approach is to apply technologies developed by the microelectronics industry to fabricate test samples with well-defined geometries. Substrates have been fabricated from materials such as silicon and ceramics, with channels to contain the energetic material. Energetic materials have been loaded into the channels, either as powders, femtosecond laser-micromachined pellets, or as vapor-deposited films. Ignition of the samples has been achieved by simple hotwires, integrated semiconductor bridges, and also by lasers. Additionally, grain-scale patterning has been performed on explosive films using both oxygen plasma etching and femtosecond laser micromachining.[2] We have demonstrated simple work functions in microenergetic devices, such as piston motion,[1] which is also a relevant diagnostic to examine combustion properties. Detonation has been achieved in deposited explosive films, recorded by high-speed photography.[3] A review of progress on manufacturing and testing will be presented, as well as historical perspectives and future directions. \newline [1] A. S. Tappan, et al., 12th International Detonation Symposium (San Diego, CA, 2002). \newline [2] A. S. Tappan, et al., 36th International Annual Conference of ICT, combined with 32nd International Pyrotechnics Seminar (Karlsruhe Federal Republic of Germany, 2005). \newline [3] A. S. Tappan, et al., 13th International Detonation Symposium (Norfolk, VA, 2006). [Preview Abstract] |
Monday, June 25, 2007 11:00AM - 11:15AM |
B6.00002: Micro-Gap Experiments and Insensitive Explosives Ralph Menikoff Early research on shock desensitized plastic-bonded explosives (circa 1970) also studied large single crystals of explosive. High quality crystals --- free from voids that serve as nucleation sites for hot spots --- have been found to be very insensitive to shock initiation. In fact, experiments were not able to initiate a large single crystal of HMX ($\sim$ 10\,mm) with a detonation wave in PBX~9404, which is 94 weight\,\% HMX and has a Chapman-Jouget pressure of 35\,GPa. Yet a single crystal of HMX can be initiated by a flyer plate that drives a shock at a similar pressure. This is especially puzzling since the detonation wave in PBX~9404 has a peak pressure at the von~Neumann spike of nearly 60\,GPa. An important difference between the two drive systems is a small gap at the PBX~9404/HMX interface due to surface roughness of the PBX; estimated to be 30 to 50 microns. Conceptually, the experiment is equivalent to the gap test used to compare the sensitivity of different explosives; albeit with a micro-gap and a very insensitive explosive. The inability of a PBX~9404 detonation wave to initiate a single crystal of~HMX is due to the reaction zone in the PBX~9404 being of comparable length to the gap in the experiment and the rarefaction or Taylor wave behind the detonation wave. [Preview Abstract] |
Monday, June 25, 2007 11:15AM - 11:30AM |
B6.00003: The Incidental Effects of Gaps in Detonating PBX 9501 Terry Salyer, Larry Hill The incidental effects of gaps in detonating explosives have been observed for many years, yet the root cause of peripheral damage due to these features has been a partial mystery. To evaluate such damage for PBX 9501, a test series has been performed that examines single and multiply-directed detonations both crossing and moving along gaps of varying widths, lengths, and angles relative to the detonation wave fronts. Damage is evaluated with steel witness plates and quantified through trench profiling, volume, and mass decrement measurements. In addition, streak camera traces are used to track detonation wave speeds along explosive material surfaces and across gaps. Such traces allow the quantification of timing delays due to gap reinitiation processes for both confined and unconfined explosives. For some reinitiation tests, a second detonation wave is directed to interfere at varying times with the post-gap run-up process of the first wave, thus allowing complex wave-wave interactions to be investigated in detail. With these cumulative observations, further insight into the mechanism of extrinsic damage due to gaps is gained. [Preview Abstract] |
Monday, June 25, 2007 11:30AM - 11:45AM |
B6.00004: Shock Separation and Dead-Zone Formation from Detonations in an Internal Air-Well Geometry John Molitoris, Henry Andreski, Raul Garza, Jan Batteux, Peter Vitello, Clark Souers Here we report on measurements of dead-zone formation due to shock separation from detonations attempting to corner-turn in an internal air-well geometry. This geometry is also known as a ``hockey-puck'' configuration. These measurements were performed on detonations in LX-17 and PBX9502 using time sequence radiography to image the event with surface contact timing pins as an additional diagnostic. In addition to an open corner in the high-explosive component we also examined the effects of steel defining the corner. In these experiments we find a long lived dead-zone consisting of shocked explosive that persists to very late times. Data and numerical modeling will be presented in addition to a comparison with previous work using an external air well. This work was performed under the auspices of the U.S. Department of Energy by University of California, Lawrence Livermore National Laboratory under Contract W-7405-Eng-48. [Preview Abstract] |
Monday, June 25, 2007 11:45AM - 12:00PM |
B6.00005: Supra-Pressure Detonation of Aluminized Explosive Ronald Brown, B. Karosich, J. Gamble, J. Stork, A. Biesterveld, T. Moore, J. Sinibaldi, M. Walpole, A. Lindfors, K. Jackson, R. Koontz, D. Thompson Results suggest that there is a continuum of reactions induced behind a supra-pressure convergent shock front in explosive cores of coaxial charges. The pressures in convergent fronts continually increase at an increasing rate from the circumference to the charge axis. Furthermore the unreacted explosive enveloped within the front is pre-pressurized at Von Neumann states much greater than from divergent detonation. For the case where the initiating sleeve detonates at constant velocity, the convergent front in the core moves at comparable velocity, suggesting a nearly common Rayleigh line behavior along the front. The sustained chemistry across the front, however, differs along the radii because of the pressure-dependent equilibria. The velocity of a sustained front in a PBXN-111 core circumferentially initiated by thin sleeves of either PBXN-110 or PBXN-112 is increased by approximately 40 percent. Measured peak pressure is approximately 600 times greater than that in a divergent front resulting from point initiation. [Preview Abstract] |
Monday, June 25, 2007 12:00PM - 12:15PM |
B6.00006: An Experimental study of Corner Turning in a Granular Ammonium Nitrate Based Explosive Susan Sorber, Peter Taylor A novel experimental geometry has been designed to perform controlled studies of corner turning in a ``tap density'' granular explosive. It enables the study of corner turning and detonation properties with high speed framing camera, piezo probes and ionization probes. The basic geometry consists of a large diameter PMMA cylinder filled with the granular explosive which is initiated on axis from below by a smaller diameter cylinder of the same explosive or a booster charge. Four experiments have been performed on a granular Ammonium Nitrate based non ideal explosive (NIE). Two experiments were initiated directly from a PE4 booster charge and two were initiated from a train including a booster charge and a 1'' diameter Copper cylinder containing the same NIE. Data from the four experiments was reproducible and observed detonation and shock waves showed good 2-D symmetry. Detonation phase velocity on the vertical side of the main container was observed and both shock and detonation velocities were observed in the corner turning region along the base of the main container. Analysis of the data shows that the booster initiated geometries with a higher input shock pressure into the NIE gave earlier detonation arrival at the lowest probes on the container side. The corner turning data is compared to a hydrocode calculation using a simple JWL++ reactive burn model. [Preview Abstract] |
Monday, June 25, 2007 12:15PM - 12:30PM |
B6.00007: ABSTRACT WITHDRAWN |
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