Bulletin of the American Physical Society
20th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 62, Number 9
Sunday–Friday, July 9–14, 2017; St. Louis, Missouri
Session V4: Experimental Developments IX: Shock Geometry |
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Chair: Nate Sanchez, Los Alamos National Laboratory Room: Regency Ballroom A |
Thursday, July 13, 2017 3:45PM - 4:00PM |
V4.00001: An experimental study of an explosively driven flat plate launcher Philip Rae, Erik Haroz, Chris Armstrong, Lee Perry For some upcoming experiments it is desired to impact a large explosive assembly with one or more moderate diameter flat metal plates traveling at high velocity (2--3~km s$^{-1}$). The time of arrival of these plates will need to carefully controlled and delayed (i.e. the time(s) of arrival known to approximately a microsecond). For this reason, producing a flyer plate from more traditional gun assemblies is not possible. Previous researchers have demonstrated the ability to throw reasonably flat metal flyers from the so-called Forest flyer geometry. The defining characteristics of this design are a carefully controlled reduction in explosive area from a larger explosive plane-wave-lens and booster pad to a smaller flyer plate to improve the planarity of the drive available and an air gap between the explosive booster and the plate to reduce the peak tensile stresses generated in the plate to suppress spalling. This experimental series comprised a number of different design variants and plate and explosive drive materials. The aim was to calibrate a predictive computational modeling capability on this kind of system in preparation for later more radical design ideas best tested in a computer before undertaking the expensive business of construction. [Preview Abstract] |
Thursday, July 13, 2017 4:00PM - 4:15PM |
V4.00002: Simple Explosive Plane Wave Booster Designs for 1-D Shock Experiments Forrest Svingala, Paul Giannuzzi, Harold Sandusky The gold standard 1-dimensional shock wave source is a flyer plate driven by a gas or powder gun. However, not all experimenters have access to such a gun, and some experiments that require large input areas (\textgreater 80 cm$^{2}$) and high input pressures (\textgreater 15 GPa) are out of reach for most of those that do. An attractive alternative to gun-driven flyers in these cases is an explosive plane wave booster (PWB). The PWB uses an explosive train to produce a 1-D wave that can throw a flyer plate or be used directly. Shock pressure levels can be adjusted as needed through the use of attenuator plates or an explosive booster pad on the output of the PWB. Unfortunately, traditional ‘dual velocity’ PWBs using two explosives require precision machining of the energetics, and as such can be difficult to produce and prohibitively expensive to purchase. This work explores several PWB designs that use cast explosives to keep costs down, and are easily scalable to the size of the required experiment. Their relative simultaneity and peak pressures are quantified using streak photography and photon Doppler velocimetry (PDV), and compared with typical values for the dual velocity lens and gun driven flyers. [Preview Abstract] |
Thursday, July 13, 2017 4:15PM - 4:45PM |
V4.00003: Towards Modernizing the Characterization of Shock and Detonation Physics Performance via Novel Diagnostics and Tests Invited Speaker: Terry Salyer For the bulk of detonation performance experiments, a fairly basic set of diagnostic techniques has evolved as the standard for acquiring the necessary measurements. Gold standard techniques such as pin switches and streak cameras still produce the high-quality data required, yet much room remains for improvement with regard to ease of use, cost of fielding, breadth of data, and diagnostic versatility. Over the past several years, an alternate set of diagnostics has been under development to replace many of these traditional techniques. Pulse Correlation Reflectometry (PCR) is a capable substitute for pin switches with the advantage of obtaining orders of magnitude more data at a small fraction of the cost and fielding time. Spectrally Encoded Imaging (SEI) can replace most applications of streak camera with the advantage of imaging surfaces through a single optical fiber that are otherwise optically inaccessible. Such diagnostics advance the measurement state of the art, but even further improvements may come through revamping the standardized tests themselves such as the copper cylinder expansion test. At the core of this modernization, the aforementioned diagnostics play a significant role in revamping and improving the standard test suite for the present era. [Preview Abstract] |
Thursday, July 13, 2017 4:45PM - 5:00PM |
V4.00004: Development of an Explosively-Driven 10-Degree Conical Shock Tube Joel Stewart Shock tubes have been used for more than a century to provide a controlled, repeatable environment to investigate shock waves traveling through various media and the interaction of these shock waves with other structures. The work presented in this paper will focus on the development of an explosively-driven conical shock tube for propagating air blast. The current work seeks to build upon previous shock tube work done by the author through increasing the efficiency of the shock tube (i.e., obtaining greater pressures/impulses at the test section while using smaller explosive charges inside the shock tube). This increased efficiency is obtained both by decreasing the cone angle and by modifying the driver section of the shock tube, which is the portion of the tube that confines the explosive charge and transitions to the air-blast-confining portion of the tube. The influence of these modifications on the air blast downstream of the shock tube’s driver section will be investigated. A comparison will be made between the computational predictions of the air blast resulting from a detonating explosive charge inside the shock tube and experimental data, and discrepancies between the computational and experimental results will be discussed. [Preview Abstract] |
Thursday, July 13, 2017 5:00PM - 5:15PM |
V4.00005: Effect of Explosive Charge Geometry on Shockwave Propagation Catherine Johnson, Phillip Mulligan, Kelly Williams, Martin Langenderfer, Jeffery Heniff The shape of an explosive charge has an effect on the shock wave propagation. Several efforts have been made to model the shock wave from a high explosive detonation. Due to the rapid rate and high variability of a detonation reaction the characteristics of detonation are difficult to predict accurately. Detonation of 15 PETN-based primasheet charges in the spherical, cubic, cylindrical, and tetrahedral configurations have been examined in this study. Qualitative data was collected through the use of high-speed photography to examine the shockwave and fireball production macroscopically. Quantitative pressure data was collected in the near and far field of the detonation reaction using free-field pressure probes, recording data both normal to charge faces as well as along charge vertices. In the near field a lower pressure zone is created along charge vertices. In the far field, pressures along these bisecting axes increase as the shock front from adjacent facets intersect. These results shed a new light on the effect an explosive charges shape has on its ability to perform work on its surroundings. This paper will describe the methodology and findings of this study as well as examine the causality and implications of its results on our understanding of the detonation phenomena. [Preview Abstract] |
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