The Experts below are selected from a list of 69726 Experts worldwide ranked by ideXlab platform
Matteo Ghidelli - One of the best experts on this subject based on the ideXlab platform.
-
Homogeneous Flow and size dependent mechanical behavior in highly ductile zr65ni35 metallic glass films
Acta Materialia, 2017Co-Authors: Matteo Ghidelli, Hosni Idrissi, Sebastien Gravier, Jean-jacques Blandin, Jean-pierre Raskin, Dominique Schryvers, Thomas PardoenAbstract:Abstract Motivated by recent studies demonstrating a high strength - high ductility potential of nano-scale metallic glass samples, the mechanical response of freestanding Zr 65 Ni 35 film with sub-micron thickness has been investigated by combining advanced on-chip tensile testing and electron microscopy. Large deformation up to 15% is found for specimen thicknesses below 500 nm with variations depending on specimen size and frame compliance. The deformation is homogenous until fracture, with no evidence of shear banding. The yield stress is doubled when decreasing the specimen cross-section, reaching ∼3 GPa for small cross-sections. The fracture strain variation is related to both the stability of the test device and to the specimen size. The study concludes on clear disconnect between the mechanisms controlling the onset of plasticity and the fracture process.
-
Homogeneous Flow and size dependent mechanical behavior in highly ductile Zr65Ni35 metallic glass films
Acta Materialia, 2017Co-Authors: Matteo Ghidelli, Hosni Idrissi, Sebastien Gravier, Jean-jacques Blandin, Jean-pierre Raskin, Thomas SchryversAbstract:Motivated by recent studies demonstrating a high strength- high ductility potential of nano-scale metallic glass samples, the mechanical response of freestanding Zr65Ni35 film with sub-micron thickness has been investigated by combining advanced on-chip tensile testing and electron microscopy. Large deformation up to 15% is found for specimen thicknesses below 500 nm with variations depending on specimen size and frame compliance. The deformation is homogenous until fracture, with no evidence of shear banding. The yield stress is doubled when decreasing the specimen cross-section, reaching 3 GPa for small cross-sections. The fracture strain variation is related to both the stability of the test device and to the specimen size. The study concludes on clear disconnect between the mechanisms controlling the onset of plasticity and the fracture process. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Christopher A Schuh - One of the best experts on this subject based on the ideXlab platform.
-
temperature strain rate and reinforcement volume fraction dependence of plastic deformation in metallic glass matrix composites
Acta Materialia, 2007Co-Authors: Christopher A SchuhAbstract:A systematic study of mechanical properties is presented for Zr-based bulk metallic glass matrix composites, spanning a wide range of strain rates and temperatures, as well as various levels of reinforcement volume fraction. All of the experimental materials exhibit mechanical properties dominated by deformation of the amorphous matrix phase, including inHomogeneous Flow and fracture at low temperatures, as well as Homogeneous Flow of both Newtonian and non-Newtonian character at high temperatures. In the Homogeneous Flow regime, the composites exhibit clear strengthening as the volume fraction of reinforcement increases. This strengthening effect is quantitatively explained in both the Newtonian and non-Newtonian regimes, and is found to arise from two contributions: (i) load transfer from the amorphous matrix to the reinforcements; and (ii) a shift in the glass structure and properties upon precipitation of the reinforcements. An additional source of apparent strengthening – in situ precipitation of reinforcement during deformation – is also discussed.
-
new regime of Homogeneous Flow in the deformation map of metallic glasses elevated temperature nanoindentation experiments and mechanistic modeling
Acta Materialia, 2004Co-Authors: Christopher A Schuh, Alan C Lund, T G NiehAbstract:Abstract The character of plastic deformation in metallic glasses is investigated through instrumented nanoindentation experiments on amorphous Pd40Ni40P20 and Mg65Cu25Gd10. Using a customized experimental apparatus, nanoindentation experiments have been conducted over four decades of indentation strain rate and from ambient temperature up to the glass transition, allowing rapid evaluation of an extensive deformation map with only small volumes of experimental material. At low rates and temperatures, inHomogeneous or serrated Flow is observed, owing to the discrete operation of individual shear bands. Two distinct regimes of Homogeneous Flow can be identified. The first, expected, regime of Homogeneous Flow corresponds to the onset of viscous deformation at high temperatures and low rates, and is well described by existing mechanistic models. The second Homogeneous regime occurs at high deformation rates even well below the glass transition, and arises when deformation rates exceed the characteristic rate for shear band nucleation, kinetically forcing strain distribution. By extending an existing model for glass deformation to explore shear band nucleation kinetics, this second regime is quantitatively rationalized and the natural frequency for shear band nucleation is extracted from the data. From this analysis the critical radius of a shear band as it transitions from nucleation to propagation is estimated to be in the submicron range.
Jun Dong Park - One of the best experts on this subject based on the ideXlab platform.
-
the non Homogeneous Flow of a thixotropic fluid around a sphere
Applied Mathematical Modelling, 2020Co-Authors: Jun Dong ParkAbstract:Abstract The non-Homogeneous Flow of a thixotropic fluid around a settling sphere is simulated. A four-parameter Moore model is used for a generic thixotropic fluid and discontinuous Galerkin method is employed to solve the structure-kinetics equation coupled with the conservation equations of mass and momentum. Depending on the normalized falling velocity U*, which compares the time scale of structure formation and destruction, Flow solutions are divided into three different regimes, which are attributed to an interplay of three competing factors: Brownian structure recovery, shear-induced structure breakdown, and the convection of microstructures. At small U*( ≪ 1), where the Brownian structure recovery is predominant, the thixotropic effect is negligible and Flow solutions are not too dissimilar to that of a Newtonian fluid. As U* increases, a remarkable structural gradient is observed and the structure profile around the settling sphere is determined by the balance of all three competing factors. For large enough U*( ≫ 1), where the Brownian structure recovery becomes negligible, the balance between shear-induced structure breakdown and the convection plays a decisive role in determining Flow profile. To quantify the interplay of three factors, the drag coefficient Cs of the sphere is investigated for ranges of U*. With this framework, the effect of the destruction parameter, the confinement ratio, and a possible nonlinearity in the model-form on the non-Homogeneous Flow of a thixotropy fluid have been addressed.
-
the non Homogeneous Flow of a thixotropic fluid around a sphere
arXiv: Fluid Dynamics, 2019Co-Authors: Jun Dong ParkAbstract:The non-Homogeneous Flow of a thixotropic fluid around a settling sphere is explored. A four-parameter Moore model is used for a generic thixotropic fluid and discontinuous Galerkin method is employed to solve the structure-kinetics equation coupled with the conservation equations of mass and momentum. Depending on Weissenberg number (Wi), Flow solutions are divided into three different regimes, which are attributed to an interplay of three competing factors: Brownian structure recovery, shear-induced structure breakdown, and structure refilling effect due to convection. At small Wi ($\ll 1$), where the Brownian structure recovery is predominant, thixotropic effect is negligible and Flow solutions are not too dissimilar to that of Newtonian fluid. As Wi increases, a remarkable structural gradient is observed and the structure profile around the settling sphere is determined by the balance of all three competing factors. For large enough Wi ($\gg 1$), where the Brownian structure recovery becomes negligible, the balance between shear-induced structure breakdown and refilling effect by convection plays a decisive role in determining Flow profile. To quantify the interplay of three factors, the drag coefficient Cs of the sphere is investigated for ranges of Wi. With this framework, the effect of destruction parameter, confinement ratio, and possible nonlinearity in the model-form on the non-Homogeneous Flow of a thixotropy fluid have been discussed.
N. Nikabdullah - One of the best experts on this subject based on the ideXlab platform.
-
The transition from Homogeneous Flow to fracture in metallic glasses at high-homologous temperatures
Scripta Materialia, 2011Co-Authors: T Prakash G. Thamburaja, N. NikabdullahAbstract:We derive a deformation map governing the transition from Homogeneous Flow to fracture response in metallic glasses under the influence of external conditions, i.e. applied deformation rates, test temperatures and sample sizes. This model is developed using simplified kinematics describing the shear-banding process, free-volume kinetics and also a phenomenologically based ductile-fracture criterion. The analytically obtained deformation map accurately reproduces an experimentally determined deformation map for a commercially available metallic glass system.
Hosni Idrissi - One of the best experts on this subject based on the ideXlab platform.
-
Homogeneous Flow and size dependent mechanical behavior in highly ductile zr65ni35 metallic glass films
Acta Materialia, 2017Co-Authors: Matteo Ghidelli, Hosni Idrissi, Sebastien Gravier, Jean-jacques Blandin, Jean-pierre Raskin, Dominique Schryvers, Thomas PardoenAbstract:Abstract Motivated by recent studies demonstrating a high strength - high ductility potential of nano-scale metallic glass samples, the mechanical response of freestanding Zr 65 Ni 35 film with sub-micron thickness has been investigated by combining advanced on-chip tensile testing and electron microscopy. Large deformation up to 15% is found for specimen thicknesses below 500 nm with variations depending on specimen size and frame compliance. The deformation is homogenous until fracture, with no evidence of shear banding. The yield stress is doubled when decreasing the specimen cross-section, reaching ∼3 GPa for small cross-sections. The fracture strain variation is related to both the stability of the test device and to the specimen size. The study concludes on clear disconnect between the mechanisms controlling the onset of plasticity and the fracture process.
-
Homogeneous Flow and size dependent mechanical behavior in highly ductile Zr65Ni35 metallic glass films
Acta Materialia, 2017Co-Authors: Matteo Ghidelli, Hosni Idrissi, Sebastien Gravier, Jean-jacques Blandin, Jean-pierre Raskin, Thomas SchryversAbstract:Motivated by recent studies demonstrating a high strength- high ductility potential of nano-scale metallic glass samples, the mechanical response of freestanding Zr65Ni35 film with sub-micron thickness has been investigated by combining advanced on-chip tensile testing and electron microscopy. Large deformation up to 15% is found for specimen thicknesses below 500 nm with variations depending on specimen size and frame compliance. The deformation is homogenous until fracture, with no evidence of shear banding. The yield stress is doubled when decreasing the specimen cross-section, reaching 3 GPa for small cross-sections. The fracture strain variation is related to both the stability of the test device and to the specimen size. The study concludes on clear disconnect between the mechanisms controlling the onset of plasticity and the fracture process. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
