Bulletin of the American Physical Society
16th APS Topical Conference on Shock Compression of Condensed Matter
Volume 54, Number 8
Sunday–Friday, June 28–July 3 2009; Nashville, Tennessee
Session T1: DC-2: Novel Phenomenon |
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Chair: Scott Stewart, University of Illinois at Urbana-Champaign Room: Tennessee Ballroom C |
Thursday, July 2, 2009 9:00AM - 9:15AM |
T1.00001: Experimental Measurements of the Chemical Reaction Zone of Detonating Liquid Explosives Viviane Bouyer, Stephen A. Sheffield, Dana M. Dattelbaum, Richard L. Gustavsen, David B. Stahl, Michel Doucet We have a joint project between CEA-DAM Le Ripault and Los Alamos National Laboratory (LANL) to study the chemical reaction zone in detonating high explosives using several different laser velocimetry techniques. The short temporal duration of the features (von Neumann spike and sonic locus) of the reaction zone make these measurements difficult. Here, we report results obtained from using and PDV (photon Doppler velocimetry) methods to measure the particle velocity history at a detonating HE (nitromethane)/PMMA interface. Experiments done at CEA were high-explosive-plane-wave initiated and those at LANL were gas-gun-projectile initiated with a detonation run of about 6 charge diameters in all experiments, in either glass or brass confinement. Excellent agreement of the interface particle velocity measurements at both Laboratories were obtained even though the initiation systems and the velocimetry systems were different. Some differences were observed in the von Neumann spike height because of the approximately 2 nanosecond time resolution of the techniques -- in some or all cases the spike top was truncated. [Preview Abstract] |
Thursday, July 2, 2009 9:15AM - 9:30AM |
T1.00002: A study of the time-dependent behaviour of the growth of reaction in a doubly-shocked explosive Hugh James A small number of experiments have previously been carried out where a double shock was propagated into an explosive, and in which the dominant variable was the time delay between the first and second shocks. Particle-velocity gauge traces show that the reaction grows with time between the shocks. This paper examines the effect of such time-dependent differences on the reaction growth behind the second shock. This growth provides insights into the apparent desensitization of the explosive when exposed to multiple shocks. [Preview Abstract] |
Thursday, July 2, 2009 9:30AM - 9:45AM |
T1.00003: Experimental Investigations of Multiphase Explosions Joel Carney, James Lightstone, Thomas McGrath Understanding the interaction of solid particles with the expanding gases of a detonating explosive is of great importance to blast applications. The addition of solid fuel particles in general reduces the detonation velocity, but their prompt (0 to 20 ms) combustion in the detonation products and surrounding air enhances the blast performance. Access to oxidizer gases being essential, the degree to which these fuel particles burn heavily depends on their dispersal throughout the explosion field. To investigate the factors affecting the dispersal of fuel particles separate from those controlling their combustion, we analyzed the dispersal of equivalent mock inert particles. Solid glass spheres embedded in detonating small explosive charges were tracked using high-speed digital shadowgraphy. Two different particle sizes, 3 and 30 $\mu $m, and different mass fractions in the explosive compositions were considered. Reactive aluminum particles in the range of 1 to 120 $\mu $m in diameter were also analyzed. During the first 50 $\mu $s of the expansion, the general trend for both reactive and inert particles is for the smaller particles to expand near the leading shock wave to a greater extent than the larger particles. The results are consistent with the numerical model applied here, highlighting the role of simple factors such as particle size and density in the early time expansion and mixing of fuels for enhanced blast applications. [Preview Abstract] |
Thursday, July 2, 2009 9:45AM - 10:00AM |
T1.00004: Detonation Shock Dynamics Calibration for Non-Ideal HE: ANFO Mark Short, Terry Salyer The detonation of ammonium nitrate (AN) and fuel-oil (FO) mixtures (ANFO) is significantly influenced by the properties of the AN (porosity, particle size, coating) and fuel-oil stoichiometry. We report on a new series of rate-stick experiments in cardboard confinement that highlight detonation front speed and curvature dependence on AN/FO stoichiometry and AN particle properties. Standard detonation velocity-curvature calibrations to the experimental data will be presented, as well as higher-order time-dependent detonation shock dynamics calibrations. [Preview Abstract] |
Thursday, July 2, 2009 10:00AM - 10:15AM |
T1.00005: Measurement of Front Curvature and Detonation Velocity for a Nonideal Heterogeneous Explosive in Axisymmetric and Two-Dimensional Geometries Andrew Higgins Detonation in a heterogeneous explosive with a relatively sparse concentration of reaction centers (``hot spots'') is investigated experimentally. The explosive system considered is nitromethane gelled with PMMA and with glass microballoons (GMB's) in suspension. The detonation velocity is measured as a function of the characteristic charge dimension (diameter or thickness) in both axisymmetric and two-dimensional planar geometries. The use of a unique, annular charge geometry (with the diameter of the annulus much greater than the annular gap thickness) permits quasi-two-dimensional detonations to be observed without undesirable lateral rarefactions that result from a finite aspect ratio. The detonation front curvature is also measured directly using an electronic streak camera. The results confirm the prior findings of Gois et al. (1996) which showed that, for a low concentration of GMB's, detonation propagation does not exhibit the expected 2:1 scaling from axisymmetric to planar geometries. This reinforces the idea that detonation in highly nonideal explosives is not governed exclusively by front curvature. [Preview Abstract] |
Thursday, July 2, 2009 10:15AM - 10:30AM |
T1.00006: Phenomenon of Energy Focusing in Explosive Systems which include High Modulus Elastic Elements I. Balagansky, K. Hokamoto, P. Manikandan, A. Matrosov, I. Stadnichenko, H. Miyoshi The phenomenon was observed in a passive HE charge of cast Comp. B without cumulative shape under shock wave loading by explosion of an active HE charge through water after preliminary compression by a leading wave in silicon carbide insert. The phenomenon manifested itself as a hole in identification steel specimen with depth of about 10 mm and diameter of about 5 mm. Results of experiments on studying of conditions of implementation of this phenomenon for SEP and Comp. B are presented. For each HE a number of experiments has been executed at various length of silicon carbide insert. Presence or absence of a hole in the steel specimen was determined. Also a number of optical registrations of process in framing mode with record step of 1 $\mu $s have been executed. Digital video camera SHIMADZU HPV-1 was used for optical registration. Results of experiments testify that the phenomenon is reproduced both for SEP, and for Comp. B. Focusing process is observed in conditions close to critical conditions of transfer of a detonation from active to a passive HE charge. [Preview Abstract] |
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