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 B1: EM-1: Shock Initiation |
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Chair: Ruth Doherty, Department of Homeland Security Room: Tennessee Ballroom C |
Monday, June 29, 2009 9:00AM - 9:30AM |
B1.00001: Recent Research Efforts in Shock Initiation of Energetic Materials Invited Speaker: Research in the area of shock initiation of energetic materials has developed over the many years since it was introduced with many changes in the diagnostic techniques and the energetic materials being tested. Recent efforts in the last 10-15 years has been in the form of safety studies investigating the lower limit of initiation as well as studies performed at elevated temperatures to examine sensitivity changes in events such as a fire. Over the years, the techniques have improved from using pins or a streak camera image on a wedge to using in-situ gauges to measure the pressure or particle velocity. The ability of various models to reproduce the results has also advanced greatly. This work will briefly discuss the history of the field with the techniques utilized followed by highlights of recent work exploring the lower limit of initiation and at elevated temperatures and will conclude with a discussion of the various modeling efforts utilized to simulate the results. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. [Preview Abstract] |
Monday, June 29, 2009 9:30AM - 9:45AM |
B1.00002: 1899-1909: Key Years for Shock Wave and Detonation Theory Olivier Heuze One century ago, in 1909, finished one of the most creative decade for the progress of shock wave and detonation understanding. Before these years, many experiments were undetaken and analyzed by Berthelot, Mallard, Vieille, Le Ch\^atellier and Dixon, especially about reactive gaseous mixtures. In 1899, Chapman provided the basis of what is called now the Chapman- Jouguet theory. During the following years, an unusual high number papers were published by different authors (Jouguet, Hadamard, Crussard, Duhem, Dixon and the hungarish Zemplen...) who yielded important contributions to the understanding of shock wave and detonation propagation. They tried to precise the former knowledge and to extend it to real geometries and to real materials. These years finished in 1909 with Duhem's paper which gathered some properties concerning real materials. After these years, the number of papers about shock waves and detonation strongly decreased. The main questions were raised, some of them were solved and the others had to wait up to several decades to be answered, by Von Neumann, Bethe, Zel'dovitch and others. Then Jouguet focused on deflagration, others retired or moved to other topics. We have collected an exhaustive bibliography. If most of these papers are now historical, some formulae or ideas like the forgotten concept of ``quasi-wave,'' with finite thickness, has a renewed interest for numerical or modern studies. [Preview Abstract] |
Monday, June 29, 2009 9:45AM - 10:00AM |
B1.00003: Mesoscale simulations of shock initiation in energetic materials characterized by three-dimensional nanotomagraphy Aaron Brundage, Ryan Wixom, Alexander Tappan, Gregory Long Three-dimensional reverse ballistic shock simulations of energetic materials have been conducted to improve our understanding of initiation at the mesoscale. Vapor-deposited films of PETN and pressed powders of HNS were characterized with a novel three-dimensional nanotomographic technique. Detailed microstructures were constructed experimentally from a stack of serial electron micrographs obtained by successive milling and imaging in a dual-beam FIB/SEM. These microstructures were digitized and imported into a multidimensional, multimaterial Eulerian shock physics code. The simulations provided insight into the mechanisms of pore collapse in PETN and HNS samples with distinctly different three-dimensional pore morphology and distribution. This modeling effort supports the novel design and development of microenergetic devices and elucidates mechanisms governing initiation of secondary explosives. [Preview Abstract] |
Monday, June 29, 2009 10:00AM - 10:15AM |
B1.00004: Initiation of Explosives From the Bow Shock of a Supersonic Penetrator Eric Ferm An analytic and computational study of supersonic penetration of an explosive is presented. The goal is the development of an initiation criterion relating projectile diameter and threshold projectile velocity determined by fundamental material and explosive parameters. The basis of the initiation criterion is an examination of the steady flow structure around a supersonic penetrator in the unreacted materials, yielding the states along the bow shock and the size and sonic character of the flow structure. The state is used to determine the time scale of the reacting explosive using initiation experiment results (Pop Plot). The size of the subsonic region is compared to the failure diameter to examine the viability of the initiation. The results are compared with experimental initiation criterion. [Preview Abstract] |
Monday, June 29, 2009 10:15AM - 10:30AM |
B1.00005: Microenergetic Shock Initiation Studies on Deposited Films of PETN Alexander S. Tappan, Ryan R. Wixom, Wayne M. Trott, Gregory T. Long, Robert Knepper, Aaron L. Brundage, David A. Jones Films of the high explosive PETN (pentaerythritol tetranitrate) up to 500-$\mu $m thick have been deposited through physical vapor deposition, with the intent of creating well-defined samples for shock-initiation studies. PETN films were characterized with surface profilometry, scanning electron microscopy, x-ray diffraction, and focused ion beam nanotomography. These high-density films were subjected to strong shocks in both the in-plane and out-of-plane orientations. Initiation behavior was monitored with high-speed framing and streak camera photography. Direct initiation with a donor explosive (either RDX with binder, or CL-20 with binder) was possible in both orientations, but with the addition of a thin aluminum buffer plate (in-plane configuration only), initiation proved to be difficult due to the attenuated shock and the high density of the PETN films. Mesoscale models of microenergetic samples were created using the shock physics code CTH and compared with experimental results. The results of these experiments will be discussed in the context of small sample geometry, deposited film morphology, and density. [Preview Abstract] |
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