Bulletin of the American Physical Society
22nd Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 67, Number 8
Monday–Friday, July 11–15, 2022; Anaheim, California
Session 1K: Early Career / Student Poster SessionPoster Student Symposium
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Room: Anaheim Marriott Platinum 7-10 |
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1K.00001: Experimental Evaluation of the Formation of a Shockwave from two Colliding Subsonic Vortex Rings Rachel Bauer Vortex rings form as a slug of air moves through an opening, such as the end of a shock tube. Shock tubes have been used extensively in explosives research and have various geometries and designs. Boundary layer forces cause the air exiting an opening to curl back upon itself creating the vortex. Previous studies have shown the interaction of vortex rings with solid walls, and in collision and reconnection with other vortex rings with circular openings. This study uses explosively formed shock waves to study the collision of vortex rings in air with different geometries visually through schlieren videography. Upon exiting the tube, the vortex rings are traveling at subsonic velocities, but after head-on collision, produce a shock wave. Different shaped vortex rings have different velocities upon exiting the tube, but still produce a shock wave after collision. Both the circular and shaped vortex rings trap air between them before collision. As more air becomes trapped, the pressure increases, creating a pressure gradient. The collision of the vortex rings causes a rapid release of air creating the resulting shock wave. Comparison of the shock and vortex velocities is performed. |
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1K.00002: Additively Manufactured Granular and Binder Metamaterial's Response To Shock Jack D Borg Homogenous material are created using sucrose crystals 180 μm to 250 μm in size and an ultraviolet sensitive resin manufactured by Anycubic. Mesoscale structures are generated in the samples to research their effect shock waves as they traverse through the target. A single stage light gas gun is utilized in the uniaxial plate impact configuration and a photo doppler velocimetry system (PDV) to perform several experiments each focusing on various wave interactions in the materials. The material's physical structure and material properties mimics that of Plastic Bonded Explosives while remaining inert, therefore allows insight into the physical response short of chemical excitation of these granular and plastic materials. CTH simulations are conducted cohesively with each experimentation setup and compared with experimental results to construct more accurate models for the materials. |
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1K.00003: High-pressure, high-temperature phase diagram and equations of state of RDX polymorphs Bethany Chidester High-explosive crystals pass through a range of pressure-temperature conditions on the path to shock-induced detonation. Accurate identification of phase boundaries is essential to predicting the phases involved in initiation and at the leading edge of the detonation front. RDX (cyclotrimethylenetrinitramine) is a commonly-used explosive that is known to have a complex phase diagram to 10 GPa and 200 C. At ambient temperatures, alpha-RDX transforms to gamma-RDX around 4 GPa, further transforming to delta-RDX around 16-18 GPa. At high temperatures, both alpha-RDX and gamma-RDX transform to the epsilon phase, but the location of the alpha-gamma-epsilon triple point has been debated. Here, we explore the high-pressure, high-temperature phase diagram of RDX to 25 GPa and 150 C in a diamond anvil cell with in situ synchrotron X-ray diffraction (XRD). We confirm the alpha-to-gamma phase transition around 4 GPa at all temperatures explored, and the gamma-to-delta phase transition around 16 GPa. We did not observe the epsilon phase of RDX up to 150 C, more tightly constraining the alpha-gamma-epsilon triple point for this material. However, we did observe some time-dependent decomposition at this temperature. These data were used to inform thermal equations of state of all three phases explored. |
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1K.00004: Radiation Stability of the Nitrate Ester Energetic Functional Group Patricia L Huestis High explosives (HE) are used in a variety of applications that require them to be stable under a wide range of harsh environments, and understanding how HE is altered by ionizing radiation is of particular importance. This talk will focus on the radiolytic degradation of the nitrate ester (-ONO2) functional group (FG) which is the energetic FG responsible for the explosive properties of the commonly used pentaerythritol tetranitrate (PETN). Trace chemical analyses using proton nuclear magnetic resonance (1H-NMR) and ultra high pressure liquid chromatography (UHPLC) were completed on control and γ-irradiated materials containing nitrate esters to assess chemical changes brought about by the ionizing radiation. Results indicate that the nitrate ester FG is the predominantly affected part of the molecule, and the most probable degradation pathway involves the cleavage of the trigger linkage (O-NO2).These results were found to be insufficient to explain changes in small scale sensitivity tests seen by other researchers, and thus other radiolytic changes to the materials will be discussed. |
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1K.00005: Quantifying Motion Blur by Imaging Shock Front Propagation Kathryn Harke Time-integrated (multiple pulse or longer-time continuous exposure) radiography using MeV Bremsstrahlung x-ray sources is the norm for imaging during system-level testing of components and structures under dynamic conditions. In large scale, dynamic, MeV range experiments, sources of error in the analysis of these datasets stem largely from motion blur. Time-integration very quickly starts to become a problem if the motion (of the compression front) during the additive time and the spatial resolution demanded in the dynamic event become commensurate. In a prelude to applying our methodology to larger scale experiments, we first aim to quantify motion blur on a well understood, small scale experiment, utilizing gas gun capabilities at The Advanced Photon Source's Dynamic Compression Sector. Both plane wave and reverberating shock wave propagation were investigated experimentally to quantify motion blur and test the validity of our state-of-the-art radiography and hydrodynamic simulation codes. |
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1K.00006: A simulated and experimental investigation into the effect of casing material fracture on the axial explosive performance of cylindrical charges Emily M Johnson Current models to predict the damage response of solids are based on empirical data from indirectly applied shocks or gradual strain increases. Neither of these conditions accurately represent the conditions a solid charge casing undergoes during explosive detonation: extremely high pressures, with zero buildup, over a short duration. The response to such conditions have been validated in air, as the shock wave can be easily observed experimentally. Validation for solids, with low visibility in the immediate contact region and an inability of most sensors to operate under the harsh conditions produced by detonation, results in the need to observe, not the response of a solid casing, but the secondary response of a witness material. This report presents information from the Plate Dent Test as a way of identifying measurable differences in the behavior of charge casings. One inch diameter Composition-B charges are cased in polyurethane, acrylic, or metal and detonated on top of a metal witness plate. The dent produced by the explosive on the witness plate is compared to three predictive simulations to validate the test's ability to distinguish between casing materials and to identify the most accurate simulation technique. |
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1K.00007: Modeling heat transfer and kinetics in a PETN RP-1 exploding bridgewire detonator: an aging study Levi Lystrom Exploding bridgewire (EBW) detonators have a wide range of applications. Teledyne RP-1 is a common commercial EBW, which has a low density pressing (initial pressing; IP) of pentaerythritol tetranitrate (PETN) explosive against the bridgewire. RP-1 detonators may be stored or experience environments that have the potential to induce electrical current across the bridgewire. These currents are likely low amplitude; however, these induced currents could result in localized heating of the PETN surrounding the bridgewire. This heating could act as a miniaturized cook-off experiment leading to unsafe conditions. Understanding how the miniaturized cook-off experiment affects the structure of the PETN within the EBW detonators is crucial to safety store and deploy EBW in environments that cause the localized heating. COMSOL Multiphysics simulations provide a platform to understand thermal degradation of processes such as these. In this study, we found that closed-circuit currents equal to or greater than 6.25 A will cause thermal runaway leading to ignition of the PETN, while currents of 6.125 A and 6 A will lead to thermal damage or aging of the PETN surrounding the bridgewire. |
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1K.00008: Real-time latent heat emission during dynamic compression freezing of water Erin J Nissen The temperature of liquid water was measured during quasi-isentropic compression for the first time. Compression was achieved through multiple shock wave loading using sapphire windows, where photon Doppler velocimetry (PDV) was collected at the liquid/window interface and the radiance was simultaneously collected from a ZrF fiber on an amplified liquid nitrogen cooled InSb detector with ~10 ns time resolution. The results show ice clusters form at pressures below the previously defined metastable limit of 6 – 7 GPa for homogeneous nucleation of ice VII. We also show the water is not hypercoooled as previously described. Instead, the latent heat from solidification brings the temperature to the liquid-ice VII melt line, where it remains with increasing pressure. We suggest an alternative hypothesis to corroborate the results presented here with previous work on dynamic compression freezing of liquid water. ** SNL is managed and operated by NTESS under DOE NNSA contract DE-NA0003525. Nevada National Security Site is operated by Mission Support and Test Services, LLC for the NNSA of U.S. DOE under contract DE-NA0003624. This abstract describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government. |
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1K.00009: Comparison between x-ray free electron laser phase contrast imaging and hydrodynamic simulations of void collapse in PETN single crystals Christian McCombs Much is still unknown about how detonation in high explosives initiates from insults such as shock, especially when the energy from the shock is lower than the energy barrier of the chemical reaction. The current hypothesis is that void collapse or other heterogeneity interactions with the shock form hot spots that initiate the chemical reaction needed to sustain shock wave propagation. Single-shot X-ray Free Electron Laser (XFEL) phase contrast imaging (PCI) was performed at the Matter in Extreme Conditions (MEC) Instrument at the Linac Coherent Light Source (LCLS). Pentaerythritol tetranitrate (PETN) high explosive single crystals with laser milled 10 micron voids were shocked with 5 GPa and probed with 40 fs, 5.822 keV X-ray pulse from the LCLS. Here, we compare hydrocode simulations of the experiment to PCI detector images. The hydrocode simulation density is converted to index of refraction and then summed along the optical axis into a 2D exit surface wave, and computationally propagated to the detector. The results of this proof of principle experiment represent the highest resolution imaging of shocked high explosives and will improve our understanding of hot spot formation in high explosives. |
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