Bulletin of the American Physical Society
16th APS Topical Conference on Shock Compression of Condensed Matter
Volume 54, Number 8
Sunday–Friday, June 28–July 3 2009; Nashville, Tennessee
Session D5: ID-2: Aluminum Spall and Strength |
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Chair: N. S. Brar, University of Dayton Research Institute Room: Magnolia Ballroom |
Monday, June 29, 2009 1:30PM - 1:45PM |
D5.00001: ABSTRACT WITHDRAWN |
Monday, June 29, 2009 1:45PM - 2:00PM |
D5.00002: Laser-Driven Spall in Al: Velocity Interferometry and Target Recovery Stephen Rothman, Sujit Bandhyopadhyay, Colin Brown, Adrian George, Nydhyrjn Gjshchkhmyj, Rebecca Greedharee, Tom Guymer, Nigel Park, Mike Parsley, Ed Price Using the HELEN laser at AWE we have done spall experiments on pure Al at strain rates between $\sim $6x10$^{5}$ and 2x10$^{6}$s$^{-1}$. A heterodyne velocity interferometer (Het-V) recorded rear-surface velocity profiles and the majority of targets were recovered. We have compared the behaviour of polycrystalline and single-crystal Al of four different crystal orientations. The results allow the correlation of pre-shot target structure -- determined by electron backscatter diffraction -- with the velocity profiles and recovered-target metallurgy. [Preview Abstract] |
Monday, June 29, 2009 2:00PM - 2:15PM |
D5.00003: Temporal Softening and its Effect upon Spall Strength Viktor Skokov, Olga Ignatova, Andrey Malyshev, Viktor Raevsky, Aleksey Podurets, Olga Tupanova, Marvin Zocher Experimental observation has revealed that the effects of shock wave loading are extremely complex, often resulting in morphological changes that result in a hardening of the material. Temporal softening that precedes the aforementioned hardening has also been observed. In Al and Cu, the duration of this softening is on the order of 0.3 to 0.5 ms. This work has revealed that, at least in some cases, this temporal softening phenomenon is attributable to the formation of complex bi-periodic twin structures. The overall morphology of these structures is rather complex, consisting of what we shall refer to as ``packages,'' with each ``package'' being composed of two sets of parallel twins aligned in a quasi-herringbone pattern. It is probable that the temperature within the ``package'' is much higher than the temperature of the surrounding material during ``package'' formation. The formation of bi-periodic twin structures and concomitant temporal softening has an effect upon spall strength. That effect is explored in the work to be presented. Samples are loaded by short duration pulses (0.2 - 1 ms) in such a way that the onset of damage occurs within the period of temporal softening. This has enabled an assessment of the softening effect on spall strength. [Preview Abstract] |
Monday, June 29, 2009 2:15PM - 2:30PM |
D5.00004: Spall and Dynamic Yielding of Aluminum and Aluminum Alloys at Strain Rates of 3x10$^{6}$ s$^{-1}$ D.A. Dalton, D.L. Worthington, P.A. Sherek, N.A. Pedrazas, A.C. Bernstein, H.J. Quevedo, P. Rambo, J. Schwarz, A. Edens, M. Geissel, I.C. Smith, E.M. Taleff, T. Ditmire We have explored the role that grain size, impurity particles and alloying in aluminum play in dynamic yielding and spall fracture at tensile strain rates of $\sim $3x10$^{6}$ s$^{-1}$. We achieved these strain rates shocking the aluminum specimens via laser ablation using the Z-Beamlet Laser at Sandia National Laboratories. The high purity aluminum and Al-1100 produced very different spall strengths and nearly the same yield strengths. Various grain-sized Al + 3 wt. {\%} Mg specimens presented the lowest spall strength, but the greatest dynamic yield strength. Fracture morphology results and particle analysis will be presented along with hydrodynamic simulations to put these results in context with previous publications. Impurity particles appeared to play a vital role in spall fracture at these fast strain rates. With respect to dynamic yielding, alloying elements such as Mg seem to be the dominant factor. [Preview Abstract] |
Monday, June 29, 2009 2:30PM - 2:45PM |
D5.00005: Shock Behavior of 2139-T8 Aluminum Daniel Casem, Dattatraya Dandekar Plane shock wave experiments have been conducted on an aluminum alloy, Al 2139-T8, to determine its response under high rates of loading. The alloying elements, copper, magnesium, and silver, have been found to improve the fatigue life and fracture toughness of Al 2139 and mitigate impact induced damage. The present suite of experiments provide measurements of the Hugoniot Elastic Limit (HEL), compression, shear strength, and spall threshold to 5 GPa. Longitudinal measurements are made with a VISAR system and shear strength is determined through direct measurements of lateral stress with manganin gages. Preliminary results indicate an HEL of approximately 0.9 GPa, a value consistent with yield stress measured at rates as high as 40k/s, and a constant spall pull-back velocity of approximately 180 m/s. The results also show that it continues to retain shear strength like other aluminum alloys. The EPIC code (Elastic Plastic Impact Calculations) is used to simulate the experimental results. [Preview Abstract] |
Monday, June 29, 2009 2:45PM - 3:00PM |
D5.00006: Investigation of aluminum 6061-T6 strength properties to 160 GPa William Reinhart, Scott Alexander, James Asay, Lalit Chhabildas Shock compression experiments were performed on aluminum 6061-T6 up to 160 GPa to probe aluminum strength through the melt regime. A careful set of experiments, using established two and three stage flyer plate launch techniques were conducted using symmetric impact loading conditions to compress the aluminum through the solid to liquid phase boundary. Velocity interferometry provides the fine structure almost as an in-situ particle velocity wave profile at the aluminum/lithium-fluoride window interface. Results will be detailed in terms of wave speeds in the shocked state for estimates of strength of the material. Results of these experiments will be discussed in detail. Sandia is a multi-program laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. [Preview Abstract] |
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