Bulletin of the American Physical Society
18th Biennial Intl. Conference of the APS Topical Group on Shock Compression of Condensed Matter held in conjunction with the 24th Biennial Intl. Conference of the Intl. Association for the Advancement of High Pressure Science and Technology (AIRAPT)
Volume 58, Number 7
Sunday–Friday, July 7–12, 2013; Seattle, Washington
Session D5: EM.2 Shock to Detonation I |
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Chair: Christophe Matignon, Commissariat a l'energie atomique Room: Cascade I |
Monday, July 8, 2013 1:45PM - 2:15PM |
D5.00001: Discrete effects in energetic materials Invited Speaker: Andrew Higgins The classical theory of detonation wave propagation has been highly successful in prediction of detonation dynamics based on a macroscopic, continuum-based approach, wherein the heterogeneity of the energetic material only enters the model via the reaction rate term (e.g., hot-spot based reaction mechanisms). The effects of spatial heterogeneity are rarely treated explicitly in detonation models. However, considerable evidence can be found that mesoscale phenomenon can influence the dynamics of the detonation front on scales larger than the heterogeneities. This evidence is critically reviewed, and possible directions for modeling approaches that incorporate the spatial granularity (discreteness) of the energetic material are suggested. [Preview Abstract] |
Monday, July 8, 2013 2:15PM - 2:30PM |
D5.00002: Transverse Initiation of an Insensitive Explosive in a Layered Slab Geometry Eric K. Anderson, Tariq D. Aslam, Scott I. Jackson Experiments are presented that explore the shock initiating layer dynamics in an insensitive high explosive. Tests were conducted with a PBX 9502 slab bonded on one side to a PBX 9501 slab. For each test, a planar detonation in the PBX 9501 was generated to drive a shock into the PBX 9502. The thickness of the PBX 9501 layer was varied to control the strength and duration of the transmitted shock. Phase velocities at the explosive outer surfaces, wave-front breakout shapes, and post-shock particle velocity histories associated with the detonating and initiating zones in the two explosives are reported and discussed. [Preview Abstract] |
Monday, July 8, 2013 2:30PM - 2:45PM |
D5.00003: Double-HE-Layer Detonation-Confinement Sandwich Tests: The Effect of Slow-Layer Density Larry Hill Over a period of several years, we have explored the phenomenon in which slabs of high explosives (HEs) with differing detonation speeds are joined along one of their faces. Both are initiated (usually by a line-wave generator) at one edge. If there were no coupling between the layers, the detonation in the fast HE would outrun that in the slow HE. In reality, the detonation in the fast HE transmits an oblique shock into the slow HE, the phase speed of which is equal to the speed of the fast HE. This has one of two effects depending on the particulars. First, the oblique shock transmitted to the slow HE can pre-shock and deaden it, extinguishing the detonation in the slow HE. Second, the oblique shock can transversely initiate the slow layer, pulling its detonation along at the fast HE speed. When the second occurs, it does so at the``penalty'' of a nominally dead layer, which forms in the slow HE adjacent to the material interface. We present the results of tests in which the fast layer was 3-mm-thick PBX 9501 (95 wt\% HMX), and the slow layer was 8-mm-thick PBX 9502 (95 wt\% TATB). The purpose was to observe the effect of slow layer density on the ``dead'' layer thickness. Very little effect was observed across the nominal PBX 9502 density range, 1.885-1.895 g/cc. [Preview Abstract] |
Monday, July 8, 2013 2:45PM - 3:00PM |
D5.00004: Shock Initiation Thresholds for Projectiles with Curved Surfaces Hugh James, Nicholas Whitworth The impacts of flat-nosed rods into bare, conventional high explosives tend to produce either detonations or very little discernable reaction. In contrast impacts from projectiles with curved striking surfaces can produce a range of reactions, some very vigorous, as well as detonations. This paper attempts to explain this complex behaviour. The identification of the initiation threshold as corresponding to the boundary of a particular set of responses, rather than just the boundary between no reaction and detonation, is discussed in the light of experimental results. The structure of the impact shock is explored and the existence of two sonic boundaries is explained. The linkage between the theoretical initiation threshold and one of the sonic boundaries is obtained by comparing the generation of the boundary to the experimentally determined presence of the threshold. The implications of this threshold, in terms of the proportion of the diameter of the projectile needed to cause initiation, are discussed and the results illustrated using CREST, a hydrocode-based reactive burn explosive model. [Preview Abstract] |
Monday, July 8, 2013 3:00PM - 3:15PM |
D5.00005: Thermodynamic Formulation of Wu-Jing Equation of State for Condensed Substances Kunihito Nagayama, Shiro Kubota Thermodynamic formulation has been made for the enthalpy-pressure-volume equation of state for condensed substances based on the assumptions proposed by Wu and Jing in the reference. [Q. Wu, and F. Jing, J. Appl. Phys., \textbf{80} (1996)4343-4349.] These state variables seem attractive for the numerical simulation of propagation of shock or detonation waves containing chemical reaction. We found a unique thermodynamic identity containing Wu-Jing parameter, i.e., the non-dimensional material parameter defined by them and the specific heat at constant pressure. This equation gives a constraint for these two parameters. Behavior of Wu-Jing parameter and constant pressure specific heat upon compression has been evaluated based on the calculation of the Gr\"{u}neisen parameter by using three theoretical models. Comparison of Wu-Jing parameter along shock Hugoniot curve and along an isentrope centering uncompressed initial state revealed that Wu-Jing parameter does depend on entropy as well as pressure, but its entropy dependence is very small. This result strongly suggests that Wu-Jing parameter as a function of only pressure will give sufficient description of high-pressure behavior of solid materials within appropriate range of pressure. [Preview Abstract] |
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