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 M6: Detonation Propagation/Mechanical Response |
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Chair: Raafat Guirguis, Naval Surface Warfare Center Dahlgren Divison Room: Fairmont Orchid Hotel Promenade I/II |
Wednesday, June 27, 2007 10:30AM - 10:45AM |
M6.00001: The Energy Diameter Effect Peter Vitello, P. Clark Souers The diameter (size) effect is the well-known increase of detonation velocity with increasing radius. We ask if a similar effect is seen with the detonation energy. To see this, it is necessary to perform the Cylinder test on small-radius samples of non-ideal explosives, which detonate with a low velocity. We fired nine ammonium nitrate/aluminum and AN/NM Cylinder shots with diameters of 12.7 to 50.8 mm using Fabry and heterodyne velocimetry for the wall velocities and pins for the detonation velocity. It is the use of the ultra-narrow 12.7 mm copper cylinders that give us points low enough to be sure that the effect exists. We find that the detonation energies at the three standard Cylinder relative volumes (2.2, 4.4, 7.2) vary roughly as the square of the detonation velocity. This is confirmed in numerical simulation calculations. A simple derivation of the relations of energy, detonation velocity, reaction zone length and detonation rate are given. We define a generalized inverse radius that can be applied to data for both explosive cylinders and outwardly-detonating spheres. The relation that detonation rate is proportional to the diameter effect slope can be used to derive the inverse radius equation. 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] |
Wednesday, June 27, 2007 10:45AM - 11:00AM |
M6.00002: Ignition and Growth Modeling of Detonating TATB Cones and Arcs* Craig Tarver, Steven Chidester Abstract. The Ignition and Growth reactive flow model for the detonating triaminotrinitrobenzene (TATB)-based explosives LX-17 and PBX 9502 is applied to recent experimental data on converging conical charges plus confined and unconfined arc charges. The conical charges are at first overdriven by the converging flow and then fail to detonate as the radial rarefaction wave slows the reaction rate. Unconfined TATB arcs detonate more slowly than cylindrical charges on the inner surface and exhibit large phase velocities on the outer surface. Confinement reduces but does not eliminate these effects. The model calculations reproduce these features and agree well with experimental detonation velocity and arrival time data. *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] |
Wednesday, June 27, 2007 11:00AM - 11:15AM |
M6.00003: Analysis of Wave Curvature and Rate Stick Experiments for Monomodal Explosives with Different Crystal Quality and Particle Size Characteristics Gerrit Sutherland Wood-Kirkwood theory and computer simulations of rate stick and wave curvature experiments of two sets of monomodal explosives are presented. One set [1] included two explosives composed of RDX or reduced sensitivity RDX representing a range of crystal quality. The second set [2] of explosives had mean particle sizes of 6, 134 and 428 $\mu $m. Wood-Kirkwood theory was used to calculate the reaction zone width from the wave curvature experiments. Two-term ignition and growth reactive model simulations for the first set of experiments were performed. Ignition and growth parameters were determined from embedded gauge experiments and critical diameter tests. The ability of the simulations to adequately predict shape of detonation velocity versus diameter curves and to replicate wave curvature data is presented. 1. G.T. Sutherland, 13$^{th}$ International Detonation Symposium, to be published. 2. H. Moulard, 9$^{th}$ International Detonation Symposium, pp. 18-24. [Preview Abstract] |
Wednesday, June 27, 2007 11:15AM - 11:30AM |
M6.00004: Damage formation during high strain rate deformation of PBS9501 Clive Siviour, William Proud A key aspect of the response of an explosive formulation to high strain rate loading is damage formation. In addition to the effect on immediate strength properties, damage, once formed, can lead to an undesirable~increase in sensitivity and rate of burning. Methodologies for understanding and characterising the damage formed during loading are therefore vital if we are to claim a true understanding of the mechanical properties of these materials. This paper presents results from experiments on stimulant, PBS9501, of a polymer bonded explosive. High strain rate loading was performed in a split Hopkinson pressure bar, using speckle metrology and high speed photography to build up a more complete data-set on the formation of damage in this material. X-ray microtomography was also applied to examine internal damage in recovered specimens. [Preview Abstract] |
Wednesday, June 27, 2007 11:30AM - 11:45AM |
M6.00005: The Dynamic Response of Energetic Formulations to Embedded Voids. Gregg Glenn, Horie Yasuyuki, Michael Gunger Programs are underway at AFRL and other labs to investigate the phenomenology of the response of energetic materials to long duration ($>$1 ms) loading environments. As part of these efforts, the effect of a defect, primarily in the form of a void, is the focus of the investigation. This paper will present a combined test and analytical study of multiple composite energetic formulations and will include a significant amount of test data. The primary variables associated with the loading environment are pressure, duration and loading rate. The energetic formulations primarily consist of ammonium perchlorate (AP), RDX, aluminum flake and HTPB binder. Void size and peak pressure were varied to determine safe loading margins. Post-test observations of reacted material were performed using a scanning electron microscope (SEM) to determine damage, crystal response and reaction locations within the sample. X-ray analysis was performed on unreacted samples to compare with reacted samples. The results are providing critical information on the sensitivity of an explosive formulation to void compression as a function of formulation, loading rate, peak pressure and duration. The results of these tests can be used in simulations to develop an improved understanding of mechanical and thermal initiation of energetic materials. [Preview Abstract] |
Wednesday, June 27, 2007 11:45AM - 12:00PM |
M6.00006: Predicting Runaway Reaction in a Solid Explosive Containing a Single Crack Scott Jackson, Larry Hill Mechanically damaged high explosive (HE) undergoing deflagration has been shown capable of generating combustion pressures and flame speeds dramatically in excess of those observed in undamaged HE. Flame penetration of HE cracks large enough to support the reaction zone increases the burning surface area and rate of gas production. Cracks confine the products, elevating the local pressure and reducing the reaction zone thickness such that it can enter continually smaller-width cracks. The process appreciably increases the flame surface area and rapidly pressurizes the crack network. This runaway of pressure and burning area, termed combustion bootstrapping, can dramatically accelerate the combustion mode and in the most extreme cases may result in deflagration-to-detonation transition. The current study is intended to help predict the critical conditions required for the onset of reaction runaway in a narrow HE slot intended to simulate a well-formed crack. We discuss experiments where flames were observed to propagate though such slots at velocities up to 10 km/s, reaching pressures in excess of 1 kbar. Pressurization of the slot due to gas-dynamic choking is then used to predict the onset of runaway reaction. This model agrees with experimental pressure measurements of observed reaction runaway in slots. [Preview Abstract] |
Wednesday, June 27, 2007 12:00PM - 12:15PM |
M6.00007: Non-Shock Initiation of Plastic Bonded Explosive: Experimental and Theoretical methods I Karmen Lappo The goal of this research is to develop an empirical matrix that relates the level of damage created by an impulsive load on an explosive to the level of violence it produces -- confined or unconfined. To develop this matrix, the first phase of the research will focus on relating the projectile velocity to a level of violence. The second phase will then relate the projectile velocity to a level of damage. This will then link the level of damage to the level of violence based on the projectile velocity. The third and final phase is to implement the data into a computational model and then validate its ability to simulate impact scenarios of explosives, explosive components, and explosive systems. [Preview Abstract] |
Wednesday, June 27, 2007 12:15PM - 12:30PM |
M6.00008: Reaction Zone Structure of Steady-State Detonation Wave for Tetranitromethane Alexander Utkin, Valentina Mochalova, Victor Garanin The investigation of the reaction zone structure at steady-state detonation in liquid TNM by means of laser interferometer VISAR was conducted. The initial density and detonation velocity of TNM were 1.64 g/cm$^{3}$ and 6.4 km/s respectively. Laser beam reflected from Al foil with thickness 7-400 mkm placed between the charge and water window. Velocity profiles with Von Neumann spike were determined. The transition from the reaction zone to unloading wave is smooth and it doesn't allow to define correctly the parameters of Chapman-Jouguet point. Approximate reaction time is 300 ns, and pressure in Von Neumann spike (26,4 GPa) exceeds the pressure in Chapman-Jouguet point (14,5 GPa) 1,8 times. Behind the shock jump a maximum gradient of particle velocity is observed which is equal to 10$^{7}$ 1/s, it is a typical value for powerful HE. Although TNM has low parameters in Chapman-Jouguet point and a large duration of chemical reaction zone, the high initial decomposition rate provides the existence of steady-state detonation front in tetranitromethane. [Preview Abstract] |
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