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 O3: AETD: Loading Techniques |
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Chair: Eric Brown, LANL Room: Pavilion East |
Wednesday, June 19, 2019 11:00AM - 11:15AM |
O3.00001: Investigating off-Hugoniot states using multi-layer ring-up targets David McGonegle, Patrick Heighway, Marcin Sliwa, Justin Wark, Cynthia Bolme, Andrew Comley, Leora Cooper, Andrew Higginbotham, Ashley Poole, Emma McBride, Bob Nagler, Inhyuk Nam, Matt Seaberg, Bruce Remington, Robert Rudd, Christopher Wehrenberg While laser shocks have long been used as a method for reaching high pressure states, their highly entropic nature limits the range of pressures over which a sample can be kept solid. Laser pulse shaping has been used to ramp compress samples while keeping them close to the isentrope, but this requires long laser pulses that are unavailable to most facilities or expensive pusher materials such as diamond or sapphire. We demonstrate the use of a multilayer target with different impedance layers that result in the sample `ringing-up' to the desired pressure via a series of smaller shocks, keeping it cooler. We present experimental data taken at LCLS, where laser-ablation pressure is used to drive a `ring-up' target, allowing for the compression of Pb sample above 100 GPa while remaining solid, approximately two times as high in pressure than where it would shock melt on the Hugoniot. We examine the feasibility of applying this technique to other samples as well as other laser facilities. [Preview Abstract] |
Wednesday, June 19, 2019 11:15AM - 11:30AM |
O3.00002: Shockwave Compression of Pre-Compressed H$_{\mathrm{\mathbf{2}}}$\textbf{-He Mixtures} Sakun Duwal, Christopher Seagle, Marcus Knudson We have performed shock compression experiments on pre-compressed H$_{\mathrm{2}}$-He mixtures. Studying pre-compressed samples of H$_{\mathrm{2}}$-He mixtures under dynamic loading allows us to access unique P-T states off of the principal Hugoniot. The understanding of material behavior at these P-T states is crucial to comprehend the origin and evolution of gas planets. Furthermore, the validation of mixture models has been a long-standing topic of interest with numerous conflicting theoretical results, particularly for non-ideal hydrogen systems. In an attempt to get a deeper knowledge in these matters, we have shock compressed mixtures of H$_{\mathrm{2}}$-He. Here, we present our experimental results on the pre-compressed samples of H$_{\mathrm{2}}$-He mixtures using pulsed-power-driven flyer plates at the Z-facility, and impact studies on the two-stage light gas gun. [Preview Abstract] |
Wednesday, June 19, 2019 11:30AM - 11:45AM |
O3.00003: Testing the performance of a novel plane wave generator with a low explosive mass using a many channel PDV system. James Richley The generation of an unsupported shockwave into a material can be used to investigate phenomena such as spall. An unsupported shock can be generated using novel flyer designs on gas guns or by using a high explosive to generate the shock. Ideally the source of the shockwave will result in an area where the material sees an approximately 1D shock. To produce such a shocked area in a target from a high explosive source a plane wave lens is typically used, however, these require precision machining of multiple explosives and typically contain more than 1 kg of HE. To reduce the explosive mass and remove the need for precision machining of high explosive a hybrid multi-detonator/explosive track system has been developed. To assess the simultaneity of the shock arrival and the pressure profile generated by the initiation train three experiments were conducted. Shock arrival times and the initial free surface velocities (after shock arrival) were recorded using up to 64 channels of PDV at the surface of a copper target placed at the output of the initiation train. The planarity of the shock generated by the initiation train in both time and pressure as a function of position are reported. [Preview Abstract] |
Wednesday, June 19, 2019 11:45AM - 12:00PM |
O3.00004: Dynamic tensile response of an alumina ceramic under 1D-stress state Jean-Luc Zinszner, Benjamin Erzar Ceramics are particularly well suited to build protective structures. However, the maximum tensile stress that the material can withstand is generally ten times less than their compressive strength. The knowledge of the dynamic tensile behavior of ceramics is essential to simulate their ballistic response. Spalling tests by means of plate impact tests are generally performed to characterize the dynamic tensile strength of ceramics. Recently, the high-pulsed power generator GEPI, producing a ramp loading, has been used to perform shockless spalling tests. It allowed highlighting the strong strain-rate sensitivity of the dynamic tensile strength of ceramics in the range 10$^{\mathrm{3}}$-10$^{\mathrm{4}}$ s$^{\mathrm{-1}}$. In this work, a new spalling technique using the GEPI machine is proposed. Instead of characterizing the material in a one-dimensional strain state, the use of small diameter cylindrical specimen allows ensuring a one-dimensional stress state. This new spalling configuration has been applied on alumina specimens at strain-rates of about 10$^{\mathrm{4}}$ s$^{\mathrm{-1}}$. The experimental results highlight the influence of the loading state on the dynamic tensile response of an alumina. \newline [Preview Abstract] |
Wednesday, June 19, 2019 12:00PM - 12:15PM |
O3.00005: ABSTRACT WITHDRAWN |
Wednesday, June 19, 2019 12:15PM - 12:30PM |
O3.00006: Measuring strength of materials at very high strain rates using electromagnetically driven expanding cylinders Eyal Avriel, Zev Lovinger, Roni Nemirovsky, Daniel Rittel In this work we developed a new methodology to measure the strength of materials at very high strain rates, using magnetically driven expanding cylinder experiments by the means of a pulse current generator (PCG). The expansion of the specimen is done using a ``pusher'' configuration, enabling one cylinder which carries the magnetic load to push out the external tested material, with negligible effects of the current/magnetic field on it. This allows also to test with this technique any material, regardless its conductivity. We use a hybrid analysis methodology to measure and define the yield stress in the tests, using the combination of experimental and numerical analyses. The analysis is conducted at the \textit{forced} stage of acceleration unlike standard expanding ring/cylinder tests in the literature which use the free ?ight stage for the strength analysis. This allows to take advantage of the high rate regime, dominated by the fast rise-time of the PCG and thus to reach very high strain rates. The technique is demonstrated for OFHC copper up to strain rates of 7.5$\cdot $10$^{\mathrm{4}}$ sec$^{\mathrm{-1}}$ and is compared with other results in the literature for this material. [Preview Abstract] |
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