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 Y5: Experimental Developments X: Imaging Methods |
Hide Abstracts |
Chair: Laura Robin Benedetti, Lawrence Livermore National Laboratory Room: Regency Ballroom B |
Friday, July 14, 2017 9:15AM - 9:30AM |
Y5.00001: Shadowgraph and schlieren imaging of explosions using a pulsed light source Kevin McNesby, Eric Collins, Richard Benjamin, Gerrit Sutherland A high-repetition rate laser is used as an illumination source for shadowgraph and schlieren imaging of explosions. The laser is a diode pumped solid state device (Nd:YAG) that operates at 200 kHz and outputs 0.33 milliJoules of energy per pulse (\textless 40 nanosecond) at a wavelength of 532 nanometers. The laser pulse rate is synchronized to a high speed video camera, such that the light from the laser coincides with the onset of the exposure period of the camera. The camera is filtered at the laser wavelength, and the illumination and viewing lines-of-sight are made coincidental to minimize parallax. The system is designed such that the intensity from the laser exceeds that from an explosive event at the laser wavelength for the duration of the camera exposure time. This enables imaging of bright events, such as explosive breakout, while maintaining reasonable contrast with regions close to the explosion but not blast-illuminated. The system is used to image the explosive near-field and particles accelerated by the explosive event when their velocity is near maximum. Problems and advantages inherent to single wavelength shadowgraph and schlieren imaging, minimization of laser speckle, as well as applications to multi-phase blast analysis are discussed. [Preview Abstract] |
Friday, July 14, 2017 9:30AM - 9:45AM |
Y5.00002: Using PDV to Understand Damage in Rocket Motor Propellants Gareth Tear, David Chapman, Phillip Ottley, William Proud, Peter Gould, Ian Cullis There is a continuing requirement to design and manufacture insensitive munition (IM) rocket motors for in-service use under a wide range of conditions, particularly due to shock initiation and detonation of damaged propellant spalled across the central bore of the rocket motor (XDT). High speed photography has been crucial in determining this behaviour, however attempts to model the dynamic behaviour are limited by the lack of precision particle and wave velocity data with which to validate against. In this work Photonic Doppler Velocimetery (PDV) has been combined with high speed video to give accurate point velocity and timing measurements of the rear surface of a propellant block impacted by a fragment travelling upto 1.4 km s\textsuperscript{-1}. By combining traditional high speed video with PDV through a dichroic mirror, the point of velocity measurement within the debris cloud has been determined. This demonstrates a new capability to characterise the damage behaviour of a double base rocket motor propellant and hence validate the damage and fragmentation algorithms used in the numerical simulations. [Preview Abstract] |
Friday, July 14, 2017 9:45AM - 10:00AM |
Y5.00003: 2D characterization of the pressure generated by an intense laser pulse on an aluminum target Bertrand Aubert, David Hebert, Jean-Luc Rullier, Emilien Lescoute, Laurent Videau, Laurent Berthe High intensity lasers are a very powerful tool to study the mechanical properties of materials, such as equations of state, or dynamic fracture. In the first case, laser experiments are usually designed so as to allow 1D interpretation of the measurements. However, as regards the characterization of material strength, it can be useful to take advantage of 2D effects that are due to the finite size of the laser focal spot, for instance in cratering experiments on thick samples. In this paper, we present an experimental study of the 2D mechanical loading generated by the interaction of a high power laser (40 J, 100 ns) with aluminum targets. The focal spot diameter is approximately 0.25 mm. Under such conditions, the pressure generated on the sample by the ablation process can reach 25 GPa. In our experiments, targets were 0.2 mm thick aluminum plates, and a VISAR was used to record the free surface velocity at various positions off the symmetry axis. The radial dependence of the mechanical loading was then deduced from these measurements and compared to the radial intensity profile. Some differences are observed and discussed, as well as their consequences on cratering experiments. [Preview Abstract] |
Friday, July 14, 2017 10:00AM - 10:15AM |
Y5.00004: ABSTRACT MOVED TO POSTER M9.68 |
Friday, July 14, 2017 10:15AM - 10:45AM |
Y5.00005: Development of a Multi-Energy Flash Computed Tomography Diagnostic for Three Dimensional Imaging of Ballistic Experiments. Invited Speaker: Michael Zellner The US Army Research Laboratory is developing a Multi-Energy Flash Computed Tomography (MEFCT) diagnostic that will be used to capture tomographic image(s) of dynamic impact and detonation events. To accomplish dynamic tomography, the diagnostic uses numerous source--detector pairs to accumulate fifteen 2-D images, which are subsequently used for reconstruction of up to three 3-D tomograms. The diagnostic is designed to provide either: a single-frame, three-dimensional tomogram that delineates material specificity throughout the field, or a three-frame tomographic movie spaced in time while lacking the information pertaining to the material specificity. This work assesses aspects of the diagnostic development including structural design, dynamic capability, instrument resolution and computational reconstruction. Examples of real-time measurements are provided from static phantom fiducials, as well as a few dynamic, non-symmetric experiments to demonstrate the strengths and usefulness of the capability. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700