Bulletin of the American Physical Society
19th Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 60, Number 8
Sunday–Friday, June 14–19, 2015; Tampa, Florida
Session C4: Materials Strength II: Dynamic Experimetal Methods |
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Chair: Wayne Chen, Purdue University, Justin Brown, Sandia National Laboratories Room: Grand H |
Monday, June 15, 2015 11:15AM - 11:45AM |
C4.00001: Strength measurements and thermo-mechanical behavior of metals at high-strain rates Invited Speaker: Guruswami Ravichandran Current state-of-the-art understanding and experimental techniques for investigating the high-strain-rate and themo-mechanical behavior of metals are reviewed. Results for the thermo-mechanical behavior and microstructural characterization of iron and tantalum over a wide range of strain rates are presented. Shear compression specimens (SCS) consisting of rectangular plates into which two slots have been machined at 45$^{\circ}$ to the loading axis are subjected to high-strain rate deformation using a split Hopkinson (Kolsky) pressure bar. Upon compression of the specimen, the gage section is subjected to a dominant state of shear deformation. \textit{In-situ} temperature measurements are performed in the deforming gage section with a high-speed infrared detector. Microstructural characterization is performed using optical and electron microscopy (SEM, TEM). Orientation imaging microscopy is used to characterize the texture. The results presented include the stress-strain behavior, strength, conversion of plastic work to heat, and microstructural and texture evolution as a function of strain and strain rate. Both iron and tantalum exhibit rate sensitive behavior and the strength of iron approaches that of high strength steels at very high strain rates. The stress-strain response of iron at low strain rates compares well with prior experiments. However, its response at very high strain rates exhibits softening and coincides with that of pre-shocked material. For tantalum, the entire plastic work is converted to heat, while for iron, the fraction of plastic work converted to heat is found to be a function of strain and strain rate. The observed high-strain-rate behavior of both the materials is correlated with microstructural and texture evolution. [Preview Abstract] |
Monday, June 15, 2015 11:45AM - 12:00PM |
C4.00002: Yield strength of Cu and an engineered material of Cu with 1{\%} Pb William Buttler, George Gray, III, Saryu Fensin, Mike Grover, Gerald Stevens, Joseph Stone, William Turley To study the effects of engineered elastic-plastic yield on the mass-ejection from shocked materials we fielded explosively driven Cu and CuPb experiments. The Cu and CuPb experiments fielded fully annealed disks in contact with PBX 9501; the CuPb was extruded with 1{\%} Pb that aggregates at the Cu grain boundaries. The elastic-plastic yield strength is explored as a difference of ejecta production of CuPb versus Cu, where the ejecta production of solid materials ties directly to the surface perturbation geometries of wavelengths (fixed at 65 $\mu $m) and amplitudes (which were varied). We observed that the Cu performs as expected, with ejecta turning on at the previously observed yield threshold, but the CuPb ejects mass in much larger quantities, at much lower wavenumber ($k = $ 2$\pi $/$\lambda )$ amplitude ($h)$ products (\textit{kh}), implying a reduced elastic-plastic yield stress of the engineered material, CuPb. [Preview Abstract] |
Monday, June 15, 2015 12:00PM - 12:15PM |
C4.00003: X-ray diffraction techniques for in-situ measurements of the dynamic flow stress of shock compressed Ta Christopher Wehrenberg, Nathan Barton, Andrew Comley, David McGonegle, Brian Maddox, James Mcnaney, Hye-Sook Park, Chris Plechaty, Shon Prisbrey, Bruce Remington, Rob Rudd A range of experimental techniques using in-situ x-ray diffraction have been developed to study the dynamic flow stress and underlying deformation of shock compressed samples. Experiments performed at the Omega and Omega EP facilities can generate both a high pressure drive, ranging from 0.3 Mbar up to and beyond the Hugoniot melt line, while simultaneous providing a short, bright x-ray source. Single crystal samples were studied either by Laue diffraction, using a broadband x-ray source created by an imploding CH capsule, or by Bragg diffraction, using a short pulse driven metal foil backlighter. The strength of polycrystalline samples can be determined using a pinhole camera setup and a quasi-monochromatic source. For highly-textured polycrystalline samples, additional strength information can be inferred from the azimuthal position of the texture spots on the Debye ring. Through measurements of the 1D-to-3D relaxation time or changes in the observed texture, information about the deformation mechanics of shock loading can be inferred. [Preview Abstract] |
Monday, June 15, 2015 12:15PM - 12:30PM |
C4.00004: Validating Material Modelling of OFHC Copper Using Dynamic Tensile Extrusion (DTE) Test at Different Impact Velocity Nicola Bonora, Gabriel Testa, Andrew Ruggiero, Gianluca Iannitti, Magnus H\"ornqvist, Nooshin Mortazavi In the Dynamic Tensile Extrusion (DTE) test, the material is subjected to very large strain, high strain rate and elevated temperature. Numerical simulation, validated comparing with measurements obtained on soft-recovered extruded fragments, can be used to probe material response under such extreme conditions and to assess constitutive models. In this work, the results of a parametric investigation on the simulation of DTE test of annealed OFHC copper - at impact velocity ranging from 350 up to 420 m/s - using phenomenological and physically based models (Johnson-Cook, Zerilli-Armstrong and Rusinek-Klepaczko), are presented. Preliminary simulation of microstructure evolution was performed using crystal plasticity package CPFEM, providing, as input, the strain history obtained with FEM at selected locations along the extruded fragments. Results were compared with EBSD investigation. [Preview Abstract] |
Monday, June 15, 2015 12:30PM - 12:45PM |
C4.00005: Shock-induced optical emission from yttria-doped cubic zircon single crystal: crystal orientation effects Xiuxia Cao, Xianming Zhou, Chuanmin Meng The shock-induced optical emission from yttria (Y$_{2}$O$_{3})$-doped cubic zircon single crystal (\textless 100\textgreater\ and \textless 110\textgreater\ crystal orientations) under the pressure range from 30 to 52 GPa was measured by the time-resolved 40-channel optical pyrometer at discrete wavelengths ranging from 400 to 800 nm. Clear periodic fluctuation was observed in spectral radiance history of \textless 110\textgreater\ ZrO$_{2}$, while a noise fluctuation was found in \textless 100\textgreater\ ZrO$_{2}$. The gray-body function was used to fit the spectral radiance histories. We found that the obtained apparent temperature varied slightly with time, but the emissivity history showed a fluctuate increase with time. Moreover, all the temperature data were independent of shock stress and were well above the calculated Lindeman melting temperature. Present result suggests that the optical emission relates to the shock-induced local hot spots, and its crystal orientation effect is attributed to the different dynamic deformation response between \textless 100\textgreater\ and \textless 110\textgreater\ ZrO$_{2}$ . [Preview Abstract] |
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