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 V6: ME.4 Strength VII |
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Chair: Curt Bronkhorst, Los Alamos National Laboratory Room: Cascade II |
Thursday, July 11, 2013 1:45PM - 2:00PM |
V6.00001: Response of magnesium single crystals to shock-wave loading at normal and elevated temperatures G. Garkushin, G. Kanel, A. Savinykh, S. Razorenov, D. Jones, W. Proud Magnesium single crystals, 0.2 mm to 3 mm thick, were shock loaded along the two axes, $a$, $c$ and the direction at 45 degrees to the $c$-axis. At the room temperature the response is very similar to that observed by Pope and Johnson for beryllium single crystals (1974). Shock compression along the $c$-axis causes inelastic deformation by means of pyramidal slip and twinning and is associated with the largest HEL. The easiest basal slip was activated by shock loading along the inclined, off-axis direction and is associated with smallest HEL value. For all orientations, we observed elastic precursor decay and growth of the HEL values with increasing temperature. However, for the $c$-orientation the growth is caused by decrease of elastic constants and not with an increase of resolved shear stress along the pyramidal slip planes. In the other orientations the resolved shear stresses in slip planes at the HEL increased with temperature. At inclined shock compression we found two plastic shock waves for which the stress behind the first depends on the peak stress associated with the second plastic wave. The crystals demonstrate the largest spall strength at shock loading along the $a$-axis and smallest one at shock loading in off-axis direction. [Preview Abstract] |
Thursday, July 11, 2013 2:00PM - 2:15PM |
V6.00002: High strain rate behavior of pure metals at elevated temperature Gabriel Testa, Nicola Bonora, Andrew Ruggiero, Gianluca Iannitti, Gentile Domenico In many applications and technology processes, such as stamping, forging, hot working etc., metals and alloys are subjected to elevated temperature and high strain rate deformation process. Characterization tests, such as quasistatic and dynamic tension or compression test, and validation tests, such as Taylor impact and DTE - dynamic tensile extrusion -, provide the experimental base of data for constitutive model validation and material parameters identification. Testing material at high strain rate and temperature requires dedicated equipment. In this work, both tensile Hopkinson bar and light gas gun where modified in order to allow material testing under sample controlled temperature conditions. Dynamic tension tests and Taylor impact tests, at different temperatures, on high purity copper (99.98{\%}), tungsten (99.95{\%}) and 316L stainless steel were performed. The accuracy of several constitutive models (Johnson and Cook, Zerilli-Armstrong, etc.) in predicting the observed material response was verified by means of extensive finite element analysis (FEA). [Preview Abstract] |
Thursday, July 11, 2013 2:15PM - 2:30PM |
V6.00003: Effects of sample temperature on spall fracture in laser shock-loaded metals between about 30 K and 1000 K Thibaut de Resseguier, Emilien Lescoute, Didier Loison, Jean-Marc Chevalier For many years, spall fracture of shock-loaded materials has been one of the most widely studied phenomena in shock physics, for both basic and technological motivations. Laser driven shocks provide a means to investigate this process over ranges of extremely high strain rates and short durations, and they allow recovering spalled samples more easily than impact or explosive loading techniques. In this paper, we present laser shock experiments on gold, aluminium and iron, over a wide range of initial temperatures from cryogenic conditions (relevant in the context of inertial confinement fusion) to about 1000 K. Time-resolved measurements of the free surface velocity are used to determine the evolution of the spall strength with sample temperature. They are complemented by post-test observations of the recovered targets, which reveal clear changes in fracture surface morphology in the spall craters. In the case of iron, possible influences of pressure-induced phase transformations prior to tensile loading are discussed on the basis of hydrodynamic simulations. [Preview Abstract] |
Thursday, July 11, 2013 2:30PM - 2:45PM |
V6.00004: Measurements of a Strength of Metals in a Picosecond Time Range Sergey Ashitkov, Pavel Komarov, Mikhail Agranat, Gennady Kanel, Vladimir Fortov We studied the shock-wave phenomena in metal films of a micron or submicron thickness irradiated by femtosecond laser pulses. The single-shot interferometer technique was used to record the time and spatial resolved displacements of both the frontal and rear surfaces of the films. The free surface displacement histories were converted into the free surface velocity histories using several various approaches. As a result, new data on the HEL and spall strength values have been obtained for aluminum, iron, nickel and other metals in strongly metastable states close to ultimate shear and tensile stresses. Comparison of measured parameters of elastic shock waves with the data of plate impact experiments at larger sample thicknesses demonstrate different regimes of the decay: whereas for pure fcc metals the decay may be described by one power function over 1 $\mu $m to 10 mm range of the distances, in the case of bcc iron main decay occurs obviously at the distance of order of 50 $\mu $m. The data are discussed from the view point of main mechanisms of high-rate deformation and fracture. [Preview Abstract] |
Thursday, July 11, 2013 2:45PM - 3:00PM |
V6.00005: Nanosecond to Picosecond Instability Regimes for Solids Under Large Deformation R.A. Graham Modeling of physical, chemical, and mechanical behaviors of solids under large finite deformation requires identification and measurement of often ambiguous, interacting behaviors. For times less than a few nanoseconds mechanical processes are not constrained by macroscopic conditions of uniaxial strain. Rather, behaviors are consequences of inertial responses controlled by crystallography, chemistry and morphology. At every moment - at each particular place - responses are born anew. Response may be inferred from related measurements as typically assumed. Nevertheless when combined with other excitations or unknown instabilities, originally unresolved events may be significant or dominate. Notable are: large magnetic fields, large electric fields, structured loading, instrumentation with piezoelectric crystals or optical windows, ferroelectric crystals or ceramics, polymers; as well as ballotechnic reactions. Instabilities resulting from mass, thermal, thermochemical, or chemical accelerations (either, or, and) may readily lead to observable effects in interactive environments. Such instabilities are not quantitatively predictable today. Forward-looking modeling requires data from sub-nanosecond, three-dimensional acceleration measurements rather than engineering fixes. Interactions among mechanical, electronic, and optical processes are overt in the original piezoelectric 3-Zone Model of Neilson and Benedick [1], and recent and related work on finite-strain deformation science.\\[4pt] [1] F. W. Neilson, W. B. Benedick, W. P. Brooks, R. A. Graham, and G. W. Anderson, in Les Ondes de Detonation, Centr. Recher. Scientific, Paris, France, pp. 391-419, 1962. [Preview Abstract] |
Thursday, July 11, 2013 3:00PM - 3:15PM |
V6.00006: XFEL diffraction of engineering materials under dynamic loading by nanoseconds laser pulse at SACLA Yuji Sano, Tomokazu Sano, Norimasa Ozaki, Toshiyuki Fujita, Keiichi Hirota, Shigekazu Miyashita, Tomoki Matsuda, Hiroyuki Uranishi, Ryota Kashiwabara, Yoshihiko Kondo, Takeshi Matsuoka, Kazuto Arakawa, Takafumi Adachi, Mayu Hashimoto, Yuichi Inubushi, Takahiro Sato, Kanade Ogawa, Makina Yabashi, Tadashi Togashi, Kensuke Tono, Osami Sakata, Koichi Akita, Kiyotaka Masaki, Kazuo A. Tanaka, Ryosuke Kodama Laser-induced plastic deformation imparts compressive residual stress and enhances the reliability of components. The authors studied the dynamic behavior of materials with XFEL during the plastic deformation. Foil of aluminum alloy was stuck on an acrylic plate with vacuum grease, through which a laser pulse of an Nd:YAG laser were irradiated. XFEL with energy of 10 keV impinged on the opposite free surface of the foil with various delay time and the diffraction was recorded with a two-dimensional detector (MPCCD). When the impulsive wave arrived at the opposite surface, the diffraction pattern obviously changed from spotty to a smoother ring pattern, suggesting the fragmentation of coarse grains. Shifts of diffraction angles were also observed. [Preview Abstract] |
Thursday, July 11, 2013 3:15PM - 3:30PM |
V6.00007: Hopkinson pressure bar set-up for the measurement of Bauschinger effect under dynamic loading Andrew Ruggiero, Nicola Bonora, Gianluca Iannitti Metals and alloys show different stress-strain characteristics under reverse loading cycle (Bauschinger effect). The knowledge of the effective material response is important in impact dynamics where material is subjected to compression-tension loading as a result of stress wave propagation. In this paper an experimental set-up of the Hopkinson pressure bar to characterize the material response under dynamic loading cycle is presented. In the proposed configuration, in one single test, the sample is subjected to tension and compression loading with same absolute stress intensity and duration. Also this solution allows the possibility to select the load cycle sequence (tension-compression or compression-tension). Relationships to determine the stress, strain rate and strain from the elastic signals at the bars which are also effective for the second stress pulse, are presented. The method was verified with FEM and used to determine the Bauschinger effect for AISI 316L stainless steel. [Preview Abstract] |
Thursday, July 11, 2013 3:30PM - 3:45PM |
V6.00008: Modeling Single-Crystal Microstructure Evolution due to Shock Loading Jeffrey Lloyd, John Clayton, David McDowell An existing high strain rate viscoplastic (HSRVP) model is extended to address single-crystal anisotropic, elastic-plastic material response and is implemented into a steady plastic wave formulation in the weak shock regime. The single-crystal HSRVP model tracks nucleation, multiplication, annihilation, and trapping processes of dislocations, as well as thermally activated and phonon drag regimes. The steady plastic wave formulation is used to model the evolving elastic-plastic response with respect to a propagating longitudinal wave, and assumes that the magnitude of quasi-transverse waves is negligible. This steady wave analysis does not require specification of artificial viscosity, which can give rise to spurious dissipative effects. The constitutive model and its numerical implementation are applied to single-crystal pure Al and results are compared with existing experimental and computational data. Dislocation evolution, lattice reorientation, and macroscopic velocity-time histories are tracked for different initial orientations subjected to varying peak shock pressures. Results suggest that initial material orientation can significantly influence microstructure evolution, which in turn has been shown to influence damage behavior during tensile unloading. [Preview Abstract] |
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