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 D3: Experimental Developments I: New Sensors and Explosives Measurements |
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Chair: Mario Fajardo, Air Force Research Lab Room: Grand Ballroom FG |
Monday, July 10, 2017 2:00PM - 2:15PM |
D3.00001: Inexpensive Method of Testing Ambient and Thermally Elevated Resistive and Piezoresistive Thin-Film Pressure Gauges Christopher Armstrong, Philip Rae, Eric Heatwole, Douglas Tasker Manganin is an alloy that changes resistance when subjected to high-pressure, but is insensitive to temperature changes. Resistance curves as a function of pressure for these gauges have been established. Another commonly used piezoresistive pressure sensor are thin-film carbon gauges, which are more pressure sensitive than manganin gauges. Carbon gauge response in high temperature is not well quantified. The current research is focused on verifying these established resistance curves as well as verifying this specific experimental configuration. In this research the carbon gauges’ resistance change is measured for thermally elevated gauges. In this setup a 20 mm caliber gun drove planar copper projectiles at the gauge, which was embedded in a copper anvil. The Hugoniot relationship allows for a comparison between observed and theoretical pressure over a pressure range 5 to 20 GPa for manganin gauges and 1 to 5 GPa for carbon gauges. The comparison between the data obtained in this research and that of others shows that the pressure-resistance curve of manganin does to not vary between lots of manganin. Additionally, the data shows that this setup is a relatively inexpensive quick means of testing gauge response to high-pressure shocks and is suitable for elevated temperature. [Preview Abstract] |
Monday, July 10, 2017 2:15PM - 2:30PM |
D3.00002: Thermal Impulse Sensors for use in Explosions. Hergen Eilers, Ray Gunawidjaja, Benjamin Anderson We have developed temperature and thermal impulse (temperature and duration) sensors for use in explosive fireballs. These sensors are seeded into an explosive fireball and record temperature and duration via morphological phase changes that are optically probed. The thermal impulse sensors include two sensor materials with different phase transition kinetics, and may include a reference material which does not undergo temperature-induced phase changes, and can aid in the optical analysis. Analyzing the sensor materials allows us to determine heating temperature and heating duration of an explosion. The temperature sensors and thermal impulse sensors were recently tested and showed promising results. However, we found that the different components of the thermal impulse sensors tend to get separated during the explosion. We are now evaluating several approaches for redesigning our thermal impulse sensors so that the components remain together during the explosion. These approaches include a core/shell assembly, crosslinking, and co-synthesis. The integrity of the chemically bonded components is evaluated by subjecting the sensors to dispersing forces, while temperature-dependent phase changes of these sensors are assessed by rapid heating using a CO$_{\mathrm{2}}$ laser. [Preview Abstract] |
Monday, July 10, 2017 2:30PM - 2:45PM |
D3.00003: Experimental and computational investigation of microwave interferometry (MI) for detonation front characterization Robert Reeves, Owen Mays, Joe Tringe, Clark Souers, Lisa Lauderbach, Emer Baluyot, Mark Converse, Ron Kane Microwave interferometry (MI) presents several advantages over more traditional existing shock and deflagration front diagnostics. Most importantly, it directly interrogates these fronts, instead of measuring the evolution of containment surfaces or explosive edges. Here we present the results of MI measurements on detonator-initiated cylinder tests, as well as on deflagration-to-detonation transition experiments, with emphasis on optimization of signal strength through coupling devices and through microwave-transparent windows. Full-wave electromagnetic field finite element simulations were employed to better understand microwave coupling into porous and near full theoretical maximum density (TMD) explosives. HMX and TATB-based explosives were investigated. Data was collected simultaneously at 26.5 GHz and 39 GHz, allowing for direct comparison of the front characteristics and providing insight into the dielectric properties of explosives at these high frequencies. MI measurements are compared against detonation velocity results from photonic Doppler velocimetry probes and high speed cameras, demonstrating the accuracy of the MI technique. Our results illustrate features of front propagation behavior that are difficult to observe with other techniques. [Preview Abstract] |
Monday, July 10, 2017 2:45PM - 3:00PM |
D3.00004: Results from a high speed pyrometer measuring detonating explosive. James Richley, James Ferguson High speed pyrometry has been deployed on two series of cylinder test experiments in order to investigate its ability to measure the temperature of a detonating explosive. The pyrometer fielded on the first series of cylinder tests consisted of two, three channel systems fed by optical fibres. The optical fibres were placed such that they observed the exposed explosive at the end of the cylinder (through a lithium fluoride window). In addition an optical emission spectrometer was used to capture the emission spectrum from the same area of the explosive. The pyrometer design was then modified to produce a six-channel system, which incorporated detectors with rise times on the order of 1 ns, this was tested on a second series of cylinder tests. Half of the cylinder tests in the second series were performed without a LiF window. Results from the second series of experiments are reported and compared with those from the first series. Initial analysis suggests that the temperature observed was at least 3700 K. [Preview Abstract] |
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