Bulletin of the American Physical Society
18th Biennial Intl. Conference of the APS Topical Group on Shock Compression of Condensed Matter held in conjunction with the 24th Biennial Intl. Conference of the Intl. Association for the Advancement of High Pressure Science and Technology (AIRAPT)
Volume 58, Number 7
Sunday–Friday, July 7–12, 2013; Seattle, Washington
Session R1: ME.3 Inelastic Deformation, Fracture, and Spall VII |
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Chair: James Stalken, Lawrence Livermore National Laboratory Room: Grand Ballroom I |
Wednesday, July 10, 2013 3:30PM - 3:45PM |
R1.00001: Elastic Precursor Decay in S-200F Beryllium Chris D. Adams, WIlliam W. Anderson, William R. Blumenthal, George (Rusty) T. Gray, III We have performed a number of plate impact experiments on vacuum hot-pressed (VHP) S-200F Be at shock stresses between 2.1 and 23 GPa to gain insight into the dynamic strength and damage behavior of this technologically important material.\footnote{C. D. Adams, et. al., ``Shock Compression of Condensed Matter -- 2009, AIP Conference Proceedings 1195, \textbf{1}, 509-512, (2009).} In this discussion we will focus on our observations of dynamic strength represented by the Hugoniot Elastic Limit (HEL) determined from the amplitude of the elastic precursor wave observed in VISAR wave profiles collected at the rear surface of the target for experiments conducted in transmission geometry. We observe monotonic decay in precursor amplitude with run distance for sample thicknesses between 4 and 8 mm. We will discuss the observed precursor decay with respect to the relative roles of twinning and dislocation mediated slip in the overall material mechanical response. We will make comparisons with similar data obtained from experiments conducted on roll-textured plate where the contribution of twinning to initial deformation is expected to be suppressed. [Preview Abstract] |
Wednesday, July 10, 2013 3:45PM - 4:00PM |
R1.00002: Characterization of shocked beryllium Carl Cady, Eric Brown, George Gray, Chris Adams, Lawrence Hull, Thomas Wynn, Michael Prime, James Cooley, Curt Bronkhorst, Frank Addessio Explosively driven arrested beryllium experiments were performed with post mortem characterization to evaluate the microstructure and failure behaviors. The test samples were encapsulated in an aluminum assembly that was large relative to the sample, and the assembly features both axial and radial momentum traps. The sample carrier was inserted from the explosively loaded end and has features to lock the carrier to the surrounding cylinder using the induced plastic flow. Calculations with Lagrangian codes showed that the tensile stresses experienced by the Be sample were below the spall stress. Metallographic characterization of the arrested Be showed radial cracks present in the samples may have been caused by bending moments. Fractography showed the fractures propagated from the side of the sample closest to the explosives, the side with the highest tensile stress. There was evidence that the fractures may have propagated from the circumferential crack outward and downward radially. The EBSD results were the most informative of the characterization techniques used. EBSD provides information regarding texture, residual strain, and twinning. There was clear evidence of grain rotation as evidenced by the pole figures, the inverse pole figures and the Kernel Average Misorientation figures. [Preview Abstract] |
Wednesday, July 10, 2013 4:00PM - 4:15PM |
R1.00003: ABSTRACT HAS BEEN MOVED TO M1.00107 |
Wednesday, July 10, 2013 4:15PM - 4:30PM |
R1.00004: Calibrating a Shear-failure model using punch specimens in the SHPB apparatus Zev Lovinger, Yehezkel Ashuach We are using a punch specimen on the split Hopkinson pressure bar (SHPB) apparatus to calibrate a shear-failure model for two Aluminum alloys. The tested specimen is a thin disc which is placed between punch and anvil adapters. We use 2D simulations of the entire SHPB set-up and compare the experimental strain-gauge measurements to our numerical gauges in the model. The straight forward procedure we developed consists of two stages: first, we fit a strength model based on the standard Hopkinson analysis and validate the model through simulations of the SHPB test, comparing the strain-gauge signals. At the second stage we use the validated strength model and calibrate the shear failure model parameters by fitting the fall-time of the transmitted signal. The fall time is found to be very sensitive to the failure parameters. Finally, we conducted FSP penetration tests to validate the failure model and found good comparison with our simulations. [Preview Abstract] |
Wednesday, July 10, 2013 4:30PM - 4:45PM |
R1.00005: Spall Properties of Aluminum 5083 Plate Fabricated using Equi-Channel Angular Extrusion and Rolling Ricky Whelchel, Naresh Thadhani, Thomas Sanders, Suveen Mathaudhu, Laszlo Kecskes The spall strength and Hugoniot Elastic Limit (HEL) of aluminum alloy 5083 (Al 5083) are compared for plates fabricated using equi-channel angular extrusion (ECAE) versus rolling. Al 5083 is a light-weight and strain-hardenable aluminum alloy used for armor plating in military transport vehicles, thus requiring the highest achievable spall strength. The spall strength of strain-hardenable alloys is a function of the grain structure and volume fraction of secondary phases, such as brittle inclusions, in addition to the extent of hardening. Materials processed by ECAE have a highly refined grain structure with little texturing and a large degree of plastic deformation, whereas rolled plates have a textured grain structure that aligns along the rolling direction. The spall behavior of Al 5083 for both forms was measured using plate impact gas gun experiments combined with rear free surface velocity measurements employing VISAR. The spall strength varied with impact orientation for the rolled plate but remained uniform for the ECAE material. Despite large differences in the HEL, the spall behavior for Al 5083 made by both processing techniques was controlled by the extent of brittle particles that acted as nucleation sites for damage during tensile failure. [Preview Abstract] |
Wednesday, July 10, 2013 4:45PM - 5:00PM |
R1.00006: The shock and spall response of AA 7010-T7651 Paul Hazell, Gareth Appleby-Thomas, David Wood, Jonathan Painter Aluminium alloys are used extensively in armour. Their use as armour materials is primarily due to their relatively low densities and their high strength characteristics. The aerospace-grade 7000-series alloy Al7010-T7651 is one possible contender for armour. In this study a series of plate-impact experiments were undertaken to investigate the behaviour of this alloy under shock. Manganin stress gauges and a heterodyne velocimeter system were used to interrogate both strength and dynamic tensile failure (spall) respectively; with microscopic analysis of recovered samples providing insight into the development of failure in the material. [Preview Abstract] |
Wednesday, July 10, 2013 5:00PM - 5:15PM |
R1.00007: Effect of Dynamic Loading Rate on the Uniaxial Dynamic Tensile Response in Commercially Pure 1050 Aluminum Nathaniel Sanchez, Darcie Dennis-Koller, David Field A series of plate impact experiments were conducted to investigate the effect of dynamic loading rate on the uniaxial dynamic tensile response of commercially pure 1050 aluminum. The loading rate (kinetic effect) was varied by altering the shock-wave shape, while the total defect density loaded in dynamic tension was held constant (spatial effect). The maximum tensile stress magnitude was held constant for all experiments in order to solely examine the effects of dynamic loading rate. Samples were soft recovered and analyzed via Electron Backscatter Diffraction (EBSD) to correlate damage to microstructural features. An optical velocimetry (VISAR) trace from the free surface was utilized to correlate the effects of damage growth rate observed through EBSD to changes in free surface velocity pull back rate. Results indicate as the dynamic tensile evolution rate was increased, a transition occurs from slow damage mechanisms of individual void nucleation and growth, to a fast mechanism of lattice curvature resulting in no observable macroscopic damage. These results suggest damage models must account for wave evolution in order to provide a robust predictive capability. [Preview Abstract] |
Wednesday, July 10, 2013 5:15PM - 5:30PM |
R1.00008: Study on the characteristics of dynamic damage in ultrapure Aluminum with 2D and 3D method Meilan Qi, Bixiong Bie, Changming Hu, Hongliang He, Xiaoxia Ran, Duan Fan, Shengnian Luo Based on the metallographic analysis, electron back scattering diffraction and 3D tomography with synchrotron x-ray method, the characteristics and laws of damage distribution in ultrapure aluminum with different degree under shock loading are characterized and analyzed. Some microscopic characteristics of damages are worthy of attention. Under the lower-velocity impact, the spherical void will grow in isolation, and the space distribution of voids is uneven in the area with same tensile stress, which is related to the microstructure of the material. Under higher-velocity impact, the voids will grow bigger and connect each other, which lead to the concentrated area of damage. The space distribution of voids and the connecting form of two voids can be found clearly from the 3D analysis result. Moreover, the result of electron back scattering diffraction shows that the emitted dislocation will appear during the growth process of voids, which accelerates the growth of voids and make the voids easy to coalesce each other. [Preview Abstract] |
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