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 D4: MS-2: Rheology of Various Metals |
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Chair: Naresh Thadani, Georgia Institute of Technology Room: Hermitage D |
Monday, June 29, 2009 1:30PM - 1:45PM |
D4.00001: The Young's modulus of 1018 steel and 6061-T6 aluminum measured from quasi-static to elastic precursor strain-rates Philip Rae, Carl Trujillo, Rusty Gray It is commonly assumed in engineering and physics that the elastic moduli of metals is independent of strain-rate, but is a weak function of temperature. An extensive literature search however has failed to find any citable reference in which the Young's modulus of any pedigreed metal was measured over a wide variety of strain-rates. To rectify this, samples of pedigreed 1018 steel and 6061-T6 aluminum have been tested at strain-rates from $10^{-4}$~s$^{-1}$ to $10^{6}$~s$^{-1}$. Low strain-rate data ($10^{-4}-10^{-2}$~s$^{-1}$)was obtained from commercial bonded strain gauges. Intermediate rate data ($\approx10^{-4}$~s$^{-1}$) was obtained from time of flight ultrasonic measurements. Shock rate data was obtained by examining the elastic precursor using shock pins and PDV (photonic Doppler velocimetry). Correction for the adiabatic versus thermal nature of the disparate strain-rate regimes have been made. Additionally, the implications of the uniaxial strain nature of the shock elastic precursor are examined with respect to comparison with uniaxial stress lower rate data. [Preview Abstract] |
Monday, June 29, 2009 1:45PM - 2:00PM |
D4.00002: Strain Rate Dependence of a Single Crystal Alloy Clive Siviour, Euan Wielewski, Nik Petrinic In order to provide data for constitutive modelling, and to better understand mechanisms behind strain rate dependence of metals, characterisation experiments have been performed on the nickel based single crystal alloy CMSX-4. This material has received extensive characterisation in the literature, concentrating on metallurgical aspects as well as creep and fatigue behaviour, giving a good background to the high rate research. The current paper will report data from compression experiments performed at strain rates from 10$^{-3}$ to 10$^3$ s$^{-1}$, and Taylor Impact tests. Data obtained will be evaluated in the light of previous thermo-mechanical characterisation of this alloy, and compared to the high rate response of polycrystalline materials. [Preview Abstract] |
Monday, June 29, 2009 2:00PM - 2:15PM |
D4.00003: Dynamic Shear Strength Measurements in Shock Loaded Molybdenum S.M. Stirk, J.C.F. Millett, N.K. Bourne, G. Whiteman, N.T. Park Dynamic shear strength measurements in shock-loaded molybdenum have been performed in the pressure range 2-20 GPa using plate-impact techniques. Shear strength is monitored using managnin stress gauges mounted such that they are sensitive to the lateral component of stress, combined with knowledge of the shock-induced impact stress in the longitudinal direction. In previous work on the shock response of body centred cubic (BCC) metals, increases in lateral stress with duration behind the shock front have been interpreted as a decrease in shear strength. In tantalum, this interpretation is supported by post-shock microstructural analysis which reveals a minor increase in dislocation density associated with a high Peierl's stress. Our current measurements in molybdenum metal further extend this work in BCC structures. [Preview Abstract] |
Monday, June 29, 2009 2:15PM - 2:30PM |
D4.00004: Modeling high-rate straining of cerium in shock waves and explosive experiments Alexander Petrovtsev, Vladimir Bychenkov, Denis Varfolomeev, Vladimir Dremov, Vyacheslav Elkin, Evgenii Kozlov, Elena Mironova, Anatoly Sapozhnikov, Natalya Sokolova, Vladislav Tarzhanov, Frank Cherne, George Gray III, Marvin Zocher The paper presents numerical results from calculations simulating experiments which were focused on the investigation of stress profiles in high-purity and high-grade cerium. The experiments were taken in recent years at LANL with use of light-gas guns for loading samples and the VISAR technique for recording stress profiles and at RFNC-VNIITF where samples were loaded with the sliding and normal detonation of HE and the registration of stress profiles was done with photo- chronographic optic lever technique. Provided is information on the multiphase equation of state and the elastic-plastic models used in calculations. Calculated and experimental profiles are compared. Specific features and characteristics of high-rate straining of cerium are discussed. [Preview Abstract] |
Monday, June 29, 2009 2:30PM - 2:45PM |
D4.00005: Shock Driven Twinning in Tantalum Single Crystals Mukul Kumar, James McNaney, Luke Hsiung, Nathan Barton Recovery based observations of high pressure material behavior generated under high explosively driven flyer based loading conditions are reported. Two shock pressures, 25, and 55 GPa and four orientations {\{}(100), (110), (111), (123){\}} were considered. Recovered material was characterized using electron backscatter diffraction along with a limited amount of transmission electron microscopy to assess the occurrence of twinning under each test condition. Material recovered from 25 GPa had a very small fraction of twinning for the (100), (110), and (111) oriented crystals while a more noticeable fraction of the (123) oriented crystal was twinned. Material recovered from 55 GPa showed little twinning for (100) orientation slightly more for the (111) orientation and a large area fraction for the (123) orientation. The EBSD and TEM observations of the underlying deformation substructure are rationalized by comparing with previous static and dynamic results along with the crystal plasticity based hydrodynamic modeling. [Preview Abstract] |
Monday, June 29, 2009 2:45PM - 3:00PM |
D4.00006: Shock Response of Cu-Nb Nanolayer Composites T.C. Germann, R.G. Hoagland, S.N. Luo, N.A. Mara, A. Misra, D.L. Paisley Large-scale classical molecular dynamics (MD) simulations and laser-launched flyer plate experiments have been used to study the shock response of Cu-Nb nanolayered composites. At a layer thickness of 5 nm, the hardness of such metallic multilayers (as measured by quasistatic indentation or compression tests) reaches a maximum due to the difficulty of dislocation transmission across the interfaces. We observe a similar strengthening effect under dynamic shock loading, both in the MD simulations and in \textit{post mortem} examinations of shock-recovered samples subjected to $\sim $20 GPa shock loading. The MD simulations provide insight into the dislocation nucleation and transmission processes that occur under compression, as well as the subsequent annihilation upon release. [Preview Abstract] |
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