Bulletin of the American Physical Society
21st Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 64, Number 8
Sunday–Friday, June 16–21, 2019; Portland, Oregon
Session O1: DSIC: Flyer Plates and Low Performance Explosives |
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Chair: Alexander S. Tappan, SNL Room: Grand Ballroom I |
Wednesday, June 19, 2019 11:00AM - 11:15AM |
O1.00001: Comparing the shock sensitivity of RDX particles using laser-driven flyer plate impacts Steven Dean, Frank De Lucia, Jr., Jennifer Gottfried Understanding the response of an energetic material to shock stimuli is important for both safety and performance concerns. Typical shock impact experiments require multiple grams of material for testing. Here, laser-driven flyer plates were used to apply various shock strengths to RDX pressed into double-sided tape to evaluate the utility of the experiment as a means to probe shock sensitivity. Three different RDX particle sizes were studied: nano-RDX (200 nm), Class 5 RDX (97{\%} particles \textless 43 $\mu $m) and Class 1 RDX (98{\%} particles \textless 841 $\mu $m). Key advantages of the laser-driven flyer plate technique are its low cost and high throughput, with the potential to prepare and conduct a hundred launches in a day using only milligrams of material. Flyers were generated by focusing the spatially-shaped pulse of an Nd:YAG laser (10 ns, up to 1.2 J, 1064 nm) onto the adhesive interface between an Al foil (25 \textmu m thick) and a borosilicate glass substrate, forming a plasma. This plasma rapidly expands and launches an Al disk approximately 800 \textmu m in diameter at velocities up to 2.4 mm/$\mu $s. The disk crosses a small air gap, and impacts the RDX sample. The material's response was determined by monitoring visible emission from the impact site with a photomultiplier tube. Initial results for the impact threshold required to induce a reaction in the RDX indicate the method is capable of correctly sorting materials by shock sensitivity ($i.e.$, Class 1 RDX \textgreater Class 5 RDX \textgreater nano-RDX). [Preview Abstract] |
Wednesday, June 19, 2019 11:15AM - 11:30AM |
O1.00002: Hot Spot Chemistry in Several Polymer-bound Explosives under Nanosecond Shock Conditions Will Bassett, Belinda Johnson, Harry Springer, Dana Dlott Initial hot spot temperatures and temperature evolutions for 4 polymer-bound explosives under shock compression by laser-driven flyer plates at speeds from 1.5 -- 4.5 km s$^{\mathrm{-1}}$ are presented along with mesoscale simulations in the multi-physics hydrocode ALE3D. The PBX formulations studied here consist of either pentaerythritol tetranitrate (PETN), 1,3,5-trinitro-1,3,5-triazinane (RDX), 2,4,6-trinitrotoluene (TNT), or 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) in a 80/20 wt.{\%} mixture with a silicone elastomer binder. The temperature dynamics demonstrate a unique shock strength dependence for each base explosive. The initial hot spot temperature and its evolution in time are shown to be indicative of chemistry occurring within the reaction zone of the four explosives. The number density of hot spots is qualitatively inferred from the spatially-averaged emissivity and appears to increase exponentially with shock strength. An increased emissivity for formulations consisting of TNT and TATB is consistent with carbon-rich explosives. Qualitative conclusions about sensitivity were drawn from the initial hot spot temperature and rate at which the number of hot spots appear to grow. [Preview Abstract] |
Wednesday, June 19, 2019 11:30AM - 11:45AM |
O1.00003: Imaging the Reactive Flow Structure Evolution in Shocked Nitromethane and Nitromethane with Additives Erin Nissen, Mithun Bhowmick, Dana Dlott We used a tabletop laser driven flyer plate to generate planar shock waves in cuvettes to produce detonations in liquid nitromethane (NM), and NM with sensitizing and inert additives. The liquid is sandwiched between an optical window and a thin aluminum lid. Photon Doppler velocimetry was used to track the flyer and particle velocity at the lid/NM interface. Images were taken using a 5-ns gated sCMOS camera at different times to analyze the flow structure evolution as a function of impact velocity and additive. Three distinct structure regimes were found to be controlled by impact velocity in pure NM, while the additives in NM control the size of the cellular structures. This may be used to calculate the reaction zone length to corroborate PDV measurements. Mechanical defects at the lid/NM interface were also investigated. There were no changes in structures between rough or smooth aluminum or steel lids, signifying the structures are a property of NM and not propagating from the lid. Molecular layers that inhibit or enhance the shock chemistry were patterned on the lid interface to control the shock to detonation time and cellular structures. [Preview Abstract] |
Wednesday, June 19, 2019 11:45AM - 12:00PM |
O1.00004: Development of Low-Density Explosive Formulations Based on Ammonium Picrate with Slow Detonation Velocities Bryce Tappan, John Budzinski, Eric Mas, Larry Hull, Larry Hill, Patrick Bowden, Joseph Lichthardt, Andrew Schmalzer, Marvin Shorty, Philip Miller, Daniel McDonald, Michael Burkett Traditional slow Dv explosive components, such as Baratol (76{\%} Ba(NO3)2 and 24{\%} TNT), rely on dilution of a traditional explosive with a dense relatively inert material, while some utilize Ca(NO3)2, ZnO or BaCO3. However, our applications require solely CHNO-based formulations that exhibit slow Dv near theoretical maximum density. Given a target Dv of 6.5 mm/\textmu s, ammonium picrate was chosen as a convenient explosive to be diluted with a high binder level (14-20{\%}). Thermal equilibrium calculations were performed to determine the binder level to provide the desired Dv. Two formulations were produced, a molding powder with a polystyrene/dioctyl adipate binder, Dv $=$ 6.45 mm/\textmu s and a cast-cure using hydroxy-terminated polybutadiene/bis-(2,2-dinitropropyl)acetal-formal/MDI binder (AmPicCC), Dv $=$ 6.58 mm/\textmu s. All formulations showed no sensitivity response or compatibility issues. The AmPicCC was chosen for further analysis, and cylinder expansion was performed followed by JWL parameterization. AmPicCC was found to initiate and propagate unconfined at thicknesses above 12 mm. The ultimate test configuration of the formulation is discussed with a sweeping initiation from PBX 9502 imaged with proton radiography (pRad) to visualize the lagging AmPicCC detonation front, as predicted by simulation. [Preview Abstract] |
Wednesday, June 19, 2019 12:00PM - 12:15PM |
O1.00005: ABSTRACT WITHDRAWN |
Wednesday, June 19, 2019 12:15PM - 12:30PM |
O1.00006: Characterization of PBX 9502 Dead Zones via Spectrally Encoded Imaging Terry Salyer The characterization of dead zones is essential for tailoring the explosive performance of TATB-based main charges to precision applications. Such dead zones occur predominantly near boosted initiation systems, where the detonation wave struggles to diffract in a non-steady propagation regime. The principal suite of tests for characterizing dead zones has traditionally included some form of wavefront breakout measurement in the vicinity of the dead zone, along with a separate radiographic examination of its dynamic evolution. Breakout measurements in the shadow of the dead zone unfortunately lack direct observation, and radiography resolution is typically limited with regard to both space and time. To converge the benefits of these tests, the dead zone cutback (DZC) test was designed to make simultaneous wavefront breakout measurements at multiple dead zone cutback locations in a single shot. The test combines the precision and economy of the standard breakout tests with the direct measurement attributes of radiography. The newly developed diagnostic based on Spectrally Encoded Imaging (SEI) enables this test, and results are in agreement with those from similar proton radiography (pRad) experiments. [Preview Abstract] |
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