Author
Futoshi Shimizu
Other affiliations: Ohio State University, Japan Atomic Energy Research Institute
Bio: Futoshi Shimizu is an academic researcher from Japan Atomic Energy Agency. The author has contributed to research in topics: Shear band & Shear modulus. The author has an hindex of 7, co-authored 8 publications receiving 1059 citations. Previous affiliations of Futoshi Shimizu include Ohio State University & Japan Atomic Energy Research Institute.
Papers
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TL;DR: The aged-rejuvenation-glue-liquid (ARGL) shear band model has been proposed for metallic glasses based on small-scale molecular dynamics simulations up to 20,000 atoms and thermomechanical analysis as mentioned in this paper.
Abstract: The aged-rejuvenation-glue-liquid (ARGL) shear band model has been proposed for metallic glasses (Acta Mater. 54 (2006) 4293), based on small-scale molecular dynamics simulations up to 20,000 atoms and thermomechanical analysis. The model predicts the existence of a critical lengthscale � 10 nm, above which melting could occur in shear-alienated glass. Large-scale molecular dynamics simulations with up to 5 million atoms have directly verified this prediction. When the applied stress exceeds the glue traction (computed separately before in a shear cohesive zone, or an amorphous-amorphous ‘‘generalized stacking fault energy’’ calculation), we indeed observe maturation of the shear band embryo into bona fide shear crack, accompanied by melting. In contrast, when the applied stress is below the glue traction, the shear band embryo does not propagate, becomes diffuse, and eventually dies. Thus this all-important quantity, the glue traction which is a property of shearalienated glass, controls the macroscopic yield point of well-aged glass. We further suggest that the disruption of chemical short-range order (‘‘chemical softening’’) governs the glue traction microscopically. Catastrophic thermal softening occurs only after chemical alienation and softening in our simulation, after the shear band embryo has already run a critical length. [doi:10.2320/matertrans.MJ200769]
843 citations
TL;DR: In this article, the embryonic shear band propagation in bulk metallic glasses is studied. But the critical condition for propagation is not its nucleation, but the far-field shear stress s1 � Eey/2 must exceed the quasi-steady-state glue traction sglue of shear-alienated glass until the glass transition temperature is approached internally due to frictional heating, at which point ESB matures as a runaway shear crack.
247 citations
TL;DR: In this article, shear deformations of Cu 57 Zr 43 bulk metallic glass (BMG) model systems are performed using molecular dynamics simulation, and the results suggest that both the hydrostatic stress and the stress normal to the shear plane should affect the response (modified Mohr-Coulomb yield criterion).
129 citations
TL;DR: In this article, critical conditions have been determined for intrinsic transformation of a vacancy Frank loop into a stacking fault tetrahedron in a face centered cubic metal by the molecular dynamics method.
58 citations
TL;DR: In this paper, the authors studied the behavior of dislocations near a crack tip in an fcc lattice and revealed three-dimensional features of dislocation nucleation and subsequent entanglement.
Abstract: Dynamic behavior of dislocations near a crack tip in an fcc lattice, studied through parallel molecular dynamics (MD) simulation with visualization facilitated by newly developed software, reveals three-dimensional features of dislocation nucleation and subsequent entanglement. Results obtained for copper and aluminum show multiple emissions of dislocation loops from the crack tip and incipient evolution of plastic deformation during crack extension. 〈100〉 dislocations are found to be emitted in aluminum at zero temperature, which however are unstable and subsequently disassociate into bundles of \(\frac{1}{2}\)\langle110\rangle dislocations.
26 citations
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TL;DR: The Open Visualization Tool (OVITO) as discussed by the authors is a 3D visualization software designed for post-processing atomistic data obtained from molecular dynamics or Monte Carlo simulations, which is written in object-oriented C++, controllable via Python scripts and easily extendable through a plug-in interface.
Abstract: The Open Visualization Tool (OVITO) is a new 3D visualization software designed for post-processing atomistic data obtained from molecular dynamics or Monte Carlo simulations. Unique analysis, editing and animations functions are integrated into its easy-to-use graphical user interface. The software is written in object-oriented C++, controllable via Python scripts and easily extendable through a plug-in interface. It is distributed as open-source software and can be downloaded from the website http://ovito.sourceforge.net/.
8,956 citations
TL;DR: In this article, the authors review the tremendous efforts over the past 50 years devoted to unraveling the atomic-level structure of MGs and the structural origin of their unique behaviors.
1,276 citations
TL;DR: A comprehensive and up-to-date review on the rapid progress achieved very recently on this subject can be found in this article, where key materials-science issues of general interest, including the initiation of shear localization starting from shear transformations, the temperature and velocity reached in the propagating or sliding band, the structural evolution inside the shear-band material, and the parameters that strongly influence shearbanding are discussed.
Abstract: Shear-banding is a ubiquitous plastic-deformation mode in materials. In metallic glasses, shear bands are particularly important as they play the decisive role in controlling plasticity and failure at room temperature. While there have been several reviews on the general mechanical properties of metallic glasses, a pressing need remains for an overview focused exclusively on shear bands, which have received tremendous attention in the past several years. This article attempts to provide a comprehensive and up-to-date review on the rapid progress achieved very recently on this subject. We describe the shear bands from the inside out, and treat key materials-science issues of general interest, including the initiation of shear localization starting from shear transformations, the temperature and velocity reached in the propagating or sliding band, the structural evolution inside the shear-band material, and the parameters that strongly influence shear-banding. Several new discoveries and concepts, such as stick-slip cold shear-banding and strength/plasticity enhancement at sub-micrometer sample sizes, will also be highlighted. The understanding built-up from these accounts will be used to explain the successful control of shear bands achieved so far in the laboratory. The review also identifies a number of key remaining questions to be answered, and presents an outlook for the field.
1,164 citations
TL;DR: A highly strained ultrathin membrane of MoS2 could lead to the creation of a solar funnel, a new form of solar cell which absorbs a much broader range of the solar spectrum that a usual single junction device as discussed by the authors.
Abstract: A highly strained ultrathin membrane of MoS2 could lead to the creation of a solar funnel, a new form of solar cell which absorbs a much broader range of the solar spectrum that a usual single junction device.
978 citations
TL;DR: The aged-rejuvenation-glue-liquid (ARGL) shear band model has been proposed for metallic glasses based on small-scale molecular dynamics simulations up to 20,000 atoms and thermomechanical analysis as mentioned in this paper.
Abstract: The aged-rejuvenation-glue-liquid (ARGL) shear band model has been proposed for metallic glasses (Acta Mater. 54 (2006) 4293), based on small-scale molecular dynamics simulations up to 20,000 atoms and thermomechanical analysis. The model predicts the existence of a critical lengthscale � 10 nm, above which melting could occur in shear-alienated glass. Large-scale molecular dynamics simulations with up to 5 million atoms have directly verified this prediction. When the applied stress exceeds the glue traction (computed separately before in a shear cohesive zone, or an amorphous-amorphous ‘‘generalized stacking fault energy’’ calculation), we indeed observe maturation of the shear band embryo into bona fide shear crack, accompanied by melting. In contrast, when the applied stress is below the glue traction, the shear band embryo does not propagate, becomes diffuse, and eventually dies. Thus this all-important quantity, the glue traction which is a property of shearalienated glass, controls the macroscopic yield point of well-aged glass. We further suggest that the disruption of chemical short-range order (‘‘chemical softening’’) governs the glue traction microscopically. Catastrophic thermal softening occurs only after chemical alienation and softening in our simulation, after the shear band embryo has already run a critical length. [doi:10.2320/matertrans.MJ200769]
843 citations