The Experts below are selected from a list of 53694 Experts worldwide ranked by ideXlab platform
K J Hemker - One of the best experts on this subject based on the ideXlab platform.
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the high strain rate response of alpha titanium experiments deformation mechanisms and modeling
Acta Materialia, 1998Co-Authors: D R Chichili, K T Ramesh, K J HemkerAbstract:Abstract The high-strain-rate mechanical response of α-titanium is examined in terms of the underlying deformation mechanisms that govern its Macroscopic Behavior. The mechanical Behavior of α-titanium has been evaluated using quasistatic (10−5 to 100 s−1) compression testing with servohydraulic machines, dynamic (10−2 to 104 s−1) compression testing with a compression Kolsky bar, and high-rate (10−4 to 105 s−1) shearing under pressure using the pressure–shear plate impact technique. At the Macroscopic level, α-titanium displays substantial rate sensitivity of the flow stress and pronounced strain hardening. The strain-hardening is greater at high strain rates than at low strain rates, and increases with strain at low strain rates. In an effort to determine the deformation mechanisms underlying this Macroscopic Behavior, the microstructures developed after low-rate and high-rate deformations have been characterized using both optical and transmission electron microscopy (TEM). At the microscopic level, both dislocations and twins are observed; the density of twins increases with both strain and strain rate and is shown to be a unique function of the flow stress (but not vice versa). Although dislocation motion accounted for the majority of plastic deformation, twin-dislocation interactions play an important role in strain hardening. The Kocks–Mecking model is used in order to describe the mechanical response as a function of the strain, strain rate and temperature; while the model is able to predict the monotonic Behavior fairly accurately, it is unable to capture the experimental Behavior observed in load–unload–reload tests.
Jurgen Rodel - One of the best experts on this subject based on the ideXlab platform.
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domain switching energies mechanical versus electrical loading in la doped bismuth ferrite lead titanate
Journal of Applied Physics, 2011Co-Authors: Thorsten Leist, Kyle G Webber, Torsten Granzow, Emil Aulbach, Jens Suffner, Jurgen RodelAbstract:The mechanical stress-induced domain switching and energy dissipation in morphotropic phase boundary (1−x)(Bi1 − yLay)FeO3–xPbTiO3 during uniaxial compressive loading have been investigated at three different temperatures. The strain obtained was found to decrease with increasing lanthanum content, although a sharp increase in strain was observed for compositions doped with 7.5 and 10 at. % La. Increased domain switching was found in compositions with decreased tetragonality. This is discussed in terms of the competing influences of the amount of domain switching and the spontaneous strain on the Macroscopic Behavior under external fields. Comparison of the mechanically and electrically dissipated energy showed significant differences, discussed in terms of the different microscopic interactions of electric field and stress.
Thomas J Pence - One of the best experts on this subject based on the ideXlab platform.
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models for one variant shape memory materials based on dissipation functions
International Journal of Non-linear Mechanics, 2002Co-Authors: Davide Bernardini, Thomas J PenceAbstract:Some simple models for the Macroscopic Behavior of shape memory materials whose microstructure can be described as a mixture of two phases are derived on the basis of a free energy and a dissipation function. Keeping a common expression for the free energy, each model is based on a different expression for the dissipation function. Temperature-induced as well as isothermal, adiabatic and convective stress-induced transformations are studied. Attention is paid to closed form solutions, comparison among the models and parameter identification.
Ruben Juanes - One of the best experts on this subject based on the ideXlab platform.
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morphodynamics of fluid fluid displacement in three dimensional deformable granular media
Physical Review Letters, 2018Co-Authors: Mariejulie Dalbe, Ruben JuanesAbstract:The simultaneous displacement of fluids through a porous medium and deformation of that host medium are crucial in applications as varied as hydraulic fracturing, methane venting from organic-rich sediments, volcanic eruptions, and desiccation cracking of soil. The authors present quantitative three-dimensional imaging of a deforming porous pack under immiscible fluid-fluid displacement. The data are modeled as the onset and evolution of cavity formation by overcoming the frictional resistance in the granular pack. These findings connect pore-scale observations to Macroscopic Behavior, and elucidate the physics at play in important natural processes and engineering applications.
Pierre Suquet - One of the best experts on this subject based on the ideXlab platform.
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Macroscopic Behavior and field fluctuations in viscoplastic composites: Second-order estimates versus full-field simulations
Journal of the Mechanics and Physics of Solids, 2006Co-Authors: Martin Idiart, Hervé Moulinec, Pedro Ponte Castañeda, Pierre SuquetAbstract:This work presents a combined numerical and theoretical study of the effective Behavior and statistics of the local fields in random viscoplastic composites. The full-field numerical simulations are based on the fast Fourier transform (FFT) algorithm [Moulinec, H., Suquet, P., 1994. A fast numerical method for computing the linear and nonlinear properties of composites. C. R. Acad. Sci. Paris II 318, 1417–1423], while the theoretical estimates follow from the so-called “second-order” procedure [Ponte Castañeda, P., 2002a. Second-order homogenization estimates for nonlinear composites incorporating field fluctuations: I—Theory. J. Mech. Phys. Solids 50, 737–757]. Two-phase fiber composites with power-law phases are considered in detail, for two different heterogeneity contrasts corresponding to fiber-reinforced and fiber-weakened composites. Both the FFT simulations and the corresponding “second-order” estimates show that the strain-rate fluctuations in these systems increase significantly, becoming progressively more anisotropic, with increasing nonlinearity. In fact, the strain-rate fluctuations tend to become unbounded in the limiting case of ideally plastic composites. This phenomenon is shown to correspond to the localization of the strain field into bands running through the composite along certain preferred orientations determined by the loading conditions. The bands tend to avoid the fibers when they are stronger than the matrix, and to pass through the fibers when they are weaker than the matrix. In general, the “second-order” estimates are found to be in good agreement with the FFT simulations, even for high nonlinearities, and they improve, often in qualitative terms, on earlier nonlinear homogenization estimates. Thus, it is demonstrated that the “second-order” method can be used to extract accurate information not only for the Macroscopic Behavior, but also for the anisotropic distribution of the local fields in nonlinear composites.
