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K. Farrell - One of the best experts on this subject based on the ideXlab platform.
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Deformation in metals after low temperature irradiation part i mapping Macroscopic Deformation modes on true stress dose plane
Acta Materialia, 2008Co-Authors: Thak Sang Byun, K. FarrellAbstract:Abstract Macroscopic Deformation modes, elastic, uniform plastic, and unstable plastic Deformation modes, are mapped in tensile true stress–dose space for more than two dozen metallic materials consisting of 13 body-centered cubic (bcc), 11 face-centered cubic (fcc), and two hexagonal closed packed (hcp) metals. The boundaries between different Deformation zones are set by the true stress versus dose curves: the yield stress (YS), plastic instability stress (PIS), and true fracture stress (FS) plotted as functions of dose. Values for these true stresses are obtained from uniaxial tensile tests or calculated from engineering tensile data using a linear strain-hardening model for necking Deformation. The relatively low-strength annealed fcc metals display large uniform plasticity regions, while unstable Deformation regions are dominant in the harder bcc and hcp metals. PIS values for all materials are independent of dose except for the precipitation-hardened IN718 alloy, where a decrease of PIS occurs due to an irradiation-induced change in second phases. In the bcc materials for high-temperature application, such as 9Cr ferritic/martensitic steels, sintered molybdenum, vanadium, and tantalum, the radiation-induced embrittlement is characterized in terms of FS decreasing with dose at relatively high doses. FS is nearly dose-independent below the critical dose for embrittlement. It is concluded that the tensile stress-based Deformation mode maps effectively integrate mechanical property information and characterize differences in radiation effects between crystalline structures or material groups.
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Deformation in metals after low-temperature irradiation: Part I – Mapping Macroscopic Deformation modes on true stress–dose plane
Acta Materialia, 2008Co-Authors: Thak Sang Byun, K. FarrellAbstract:Abstract Macroscopic Deformation modes, elastic, uniform plastic, and unstable plastic Deformation modes, are mapped in tensile true stress–dose space for more than two dozen metallic materials consisting of 13 body-centered cubic (bcc), 11 face-centered cubic (fcc), and two hexagonal closed packed (hcp) metals. The boundaries between different Deformation zones are set by the true stress versus dose curves: the yield stress (YS), plastic instability stress (PIS), and true fracture stress (FS) plotted as functions of dose. Values for these true stresses are obtained from uniaxial tensile tests or calculated from engineering tensile data using a linear strain-hardening model for necking Deformation. The relatively low-strength annealed fcc metals display large uniform plasticity regions, while unstable Deformation regions are dominant in the harder bcc and hcp metals. PIS values for all materials are independent of dose except for the precipitation-hardened IN718 alloy, where a decrease of PIS occurs due to an irradiation-induced change in second phases. In the bcc materials for high-temperature application, such as 9Cr ferritic/martensitic steels, sintered molybdenum, vanadium, and tantalum, the radiation-induced embrittlement is characterized in terms of FS decreasing with dose at relatively high doses. FS is nearly dose-independent below the critical dose for embrittlement. It is concluded that the tensile stress-based Deformation mode maps effectively integrate mechanical property information and characterize differences in radiation effects between crystalline structures or material groups.
Thomas L. Reinecke - One of the best experts on this subject based on the ideXlab platform.
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electron acoustic phonon scattering rates in ii vi quantum dots contribution of the Macroscopic Deformation potential
Solid State Communications, 2000Co-Authors: Augusto M. Alcalde, G. E. Marques, Gerald Weber, Thomas L. ReineckeAbstract:Abstract The electron–acoustic-phonon scattering process in spherical II–VI quantum dots is discussed. The quantized acoustic modes are described in terms of Lamb's classical theory for the oscillations of a continuous sphere. The longitudinal spheroidal modes are included owing to their dominant contribution to the acoustic-phonon Deformation potential (DP) scattering. We considered two mechanisms for the interaction between electrons and acoustic modes: microscopic DP, and Macroscopic acoustic Deformation, also called the ripple mechanism (RM). We also discuss the influence of the glass matrix on the electron–phonon coupling, which is particularly important for the RM. Our calculations show that the Macroscopic Deformation scattering rates become dominant by more than an order of magnitude, for a small dot radius. In general, the total scattering rate depends substantially on the choice of the mechanical boundary conditions and on the acoustic properties of the glass matrix.
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Electron–acoustic-phonon scattering rates in II–VI quantum dots: contribution of the Macroscopic Deformation potential
Solid State Communications, 2000Co-Authors: Augusto M. Alcalde, Gilmar E. Marques, Gerald Weber, Thomas L. ReineckeAbstract:Abstract The electron–acoustic-phonon scattering process in spherical II–VI quantum dots is discussed. The quantized acoustic modes are described in terms of Lamb's classical theory for the oscillations of a continuous sphere. The longitudinal spheroidal modes are included owing to their dominant contribution to the acoustic-phonon Deformation potential (DP) scattering. We considered two mechanisms for the interaction between electrons and acoustic modes: microscopic DP, and Macroscopic acoustic Deformation, also called the ripple mechanism (RM). We also discuss the influence of the glass matrix on the electron–phonon coupling, which is particularly important for the RM. Our calculations show that the Macroscopic Deformation scattering rates become dominant by more than an order of magnitude, for a small dot radius. In general, the total scattering rate depends substantially on the choice of the mechanical boundary conditions and on the acoustic properties of the glass matrix.
Thak Sang Byun - One of the best experts on this subject based on the ideXlab platform.
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Deformation in metals after low temperature irradiation part i mapping Macroscopic Deformation modes on true stress dose plane
Acta Materialia, 2008Co-Authors: Thak Sang Byun, K. FarrellAbstract:Abstract Macroscopic Deformation modes, elastic, uniform plastic, and unstable plastic Deformation modes, are mapped in tensile true stress–dose space for more than two dozen metallic materials consisting of 13 body-centered cubic (bcc), 11 face-centered cubic (fcc), and two hexagonal closed packed (hcp) metals. The boundaries between different Deformation zones are set by the true stress versus dose curves: the yield stress (YS), plastic instability stress (PIS), and true fracture stress (FS) plotted as functions of dose. Values for these true stresses are obtained from uniaxial tensile tests or calculated from engineering tensile data using a linear strain-hardening model for necking Deformation. The relatively low-strength annealed fcc metals display large uniform plasticity regions, while unstable Deformation regions are dominant in the harder bcc and hcp metals. PIS values for all materials are independent of dose except for the precipitation-hardened IN718 alloy, where a decrease of PIS occurs due to an irradiation-induced change in second phases. In the bcc materials for high-temperature application, such as 9Cr ferritic/martensitic steels, sintered molybdenum, vanadium, and tantalum, the radiation-induced embrittlement is characterized in terms of FS decreasing with dose at relatively high doses. FS is nearly dose-independent below the critical dose for embrittlement. It is concluded that the tensile stress-based Deformation mode maps effectively integrate mechanical property information and characterize differences in radiation effects between crystalline structures or material groups.
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Deformation in metals after low-temperature irradiation: Part I – Mapping Macroscopic Deformation modes on true stress–dose plane
Acta Materialia, 2008Co-Authors: Thak Sang Byun, K. FarrellAbstract:Abstract Macroscopic Deformation modes, elastic, uniform plastic, and unstable plastic Deformation modes, are mapped in tensile true stress–dose space for more than two dozen metallic materials consisting of 13 body-centered cubic (bcc), 11 face-centered cubic (fcc), and two hexagonal closed packed (hcp) metals. The boundaries between different Deformation zones are set by the true stress versus dose curves: the yield stress (YS), plastic instability stress (PIS), and true fracture stress (FS) plotted as functions of dose. Values for these true stresses are obtained from uniaxial tensile tests or calculated from engineering tensile data using a linear strain-hardening model for necking Deformation. The relatively low-strength annealed fcc metals display large uniform plasticity regions, while unstable Deformation regions are dominant in the harder bcc and hcp metals. PIS values for all materials are independent of dose except for the precipitation-hardened IN718 alloy, where a decrease of PIS occurs due to an irradiation-induced change in second phases. In the bcc materials for high-temperature application, such as 9Cr ferritic/martensitic steels, sintered molybdenum, vanadium, and tantalum, the radiation-induced embrittlement is characterized in terms of FS decreasing with dose at relatively high doses. FS is nearly dose-independent below the critical dose for embrittlement. It is concluded that the tensile stress-based Deformation mode maps effectively integrate mechanical property information and characterize differences in radiation effects between crystalline structures or material groups.
Augusto M. Alcalde - One of the best experts on this subject based on the ideXlab platform.
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Spin-flip relaxation due to phonon Macroscopic Deformation potential in quantum dots
Microelectronics Journal, 2005Co-Authors: Augusto M. Alcalde, O. O. Diniz Neto, G. E. MarquesAbstract:Abstract We have calculated the spin-flip relaxation rates of electrons in a single CdTe spherical quantum dot due to the interaction with acoustical phonons via Macroscopic Deformation potential, also called the ripple mechanism . The relaxation of spin states is possible considering that the applied magnetic field and the coupling between valence and conduction bands produce admixture, both in the electrons as well as in the hole spin states. We have demonstrated that the inclusion of spin states mixture produces an appreciable probability of spin-preserving and spin-flip transitions. The electronic states are calculated within the multiband k · p approximation and the phonon modes are described as plane-waves. We have studied the dependence of the transition rates with the magnetic field and with the dot size. Our results show a fair compatibility with available experimental data.
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electron acoustic phonon scattering rates in ii vi quantum dots contribution of the Macroscopic Deformation potential
Solid State Communications, 2000Co-Authors: Augusto M. Alcalde, G. E. Marques, Gerald Weber, Thomas L. ReineckeAbstract:Abstract The electron–acoustic-phonon scattering process in spherical II–VI quantum dots is discussed. The quantized acoustic modes are described in terms of Lamb's classical theory for the oscillations of a continuous sphere. The longitudinal spheroidal modes are included owing to their dominant contribution to the acoustic-phonon Deformation potential (DP) scattering. We considered two mechanisms for the interaction between electrons and acoustic modes: microscopic DP, and Macroscopic acoustic Deformation, also called the ripple mechanism (RM). We also discuss the influence of the glass matrix on the electron–phonon coupling, which is particularly important for the RM. Our calculations show that the Macroscopic Deformation scattering rates become dominant by more than an order of magnitude, for a small dot radius. In general, the total scattering rate depends substantially on the choice of the mechanical boundary conditions and on the acoustic properties of the glass matrix.
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Electron–acoustic-phonon scattering rates in II–VI quantum dots: contribution of the Macroscopic Deformation potential
Solid State Communications, 2000Co-Authors: Augusto M. Alcalde, Gilmar E. Marques, Gerald Weber, Thomas L. ReineckeAbstract:Abstract The electron–acoustic-phonon scattering process in spherical II–VI quantum dots is discussed. The quantized acoustic modes are described in terms of Lamb's classical theory for the oscillations of a continuous sphere. The longitudinal spheroidal modes are included owing to their dominant contribution to the acoustic-phonon Deformation potential (DP) scattering. We considered two mechanisms for the interaction between electrons and acoustic modes: microscopic DP, and Macroscopic acoustic Deformation, also called the ripple mechanism (RM). We also discuss the influence of the glass matrix on the electron–phonon coupling, which is particularly important for the RM. Our calculations show that the Macroscopic Deformation scattering rates become dominant by more than an order of magnitude, for a small dot radius. In general, the total scattering rate depends substantially on the choice of the mechanical boundary conditions and on the acoustic properties of the glass matrix.
Makoto Uchida - One of the best experts on this subject based on the ideXlab platform.
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computational simulation of micro to Macroscopic Deformation behavior of cavitated rubber blended amorphous polymer using second order homogenization method
Key Engineering Materials, 2014Co-Authors: Makoto Uchida, Naoya TadaAbstract:To evaluate the effect of the size of the microstructure on the mechanical property of the cavitated rubber blended (voided) amorphous polymer, the FEM simulation based on the rate form second-order homogenization method, in which rates of the Macroscopic strain and strain gradient are given to the microstructure, was performed. Computational simulations of micro-to Macroscopic Deformation behaviors of amorphous polymers including different sizes and volume fractions of the voids were performed. Non-affine molecular chain network theory was employed to represent the inelastic Deformation behavior of the amorphous polymer matrix. With the increase in the volume fraction of the void, decrease and periodical fluctuation of stress and localized Deformation in the Macroscopic field were observed, and were more emphasized with the increase in the size of the void. These results were closely related to the non-uniform Deformation and volume increase of the void in the microscopic field.
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Micro- to Macroscopic Deformation Behavior of Amorphous Polymer with Slightly Heterogeneous Distribution of Molecular Chains
Solid Mechanics and Its Applications, 2004Co-Authors: Yoshihiro Tomita, Makoto UchidaAbstract:The micro- to Macroscopic Deformation behavior of the polymer under Macroscopically uniform tension and shearing, and surface Deformation of the plane strain polymer block under compression were investigated by means of computational simulation with the nonafflne molecular chain network model with slightly heterogeneous distribution of the molecular chain, in other words, the distribution of the initial strength of the polymer. The results clarified the onset of microscopic shear bands emanating from the slightly weak points and their evolution, interaction and percolation. The interaction of weak points and the evolution of surface undulation under compression have been demonstrated.
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Effect of Heterogeneity of Microstructure of Amorphous Polymer on Micro- to Macroscopic Deformation Behavior
TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series A, 2004Co-Authors: Makoto Uchida, Yoshihiro TomitaAbstract:The purpose of the present study is to elucidate the micro-to Macroscopic Deformation behavior of an amorphous polymer with slightly heterogeneous distribution of molecular chain, in other words, the distribution of the initial strength of the polymer. The micro-to Macroscopic Deformation behavior of polymer blocks under Macroscopically uniform tension, compression and shearing, and surface Deformation of the plane strain block under compression were investigated by means of computational simulation with the nonaffine molecular chain network model. The results clarified the onset of microscopic shear bands emanating from the slightly weak points and their evolution, interaction and percolation of new shear band. The effect of distribution patterns and variation of initial shear strength on the Deformation, the interaction of weak points, transition of microscopic shear bands to Macroscopically inhomogeneous Deformation including the evolution of surface undulation under compression have been demonstrated. In Macroscopically homogeneous Deformation as well as heterogeneous Deformation, the Deformation resistance increases with the introduction of heterogeneity of the initial shear strength.
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Computational Evaluation of Micro- to Macroscopic Deformation Behavior of Amorphous Polymer with Slightly Heterogeneous Distribution of Initial Shear Strength
Solid Mechanics and its Applications, 2004Co-Authors: Yoshihiro Tomita, Makoto UchidaAbstract:We investigate the characteristic Deformation behavior of an amorphous polymer with a heterogeneous distribution of the initial shear strength (ISS). The Deformation behavior of polymers under Macroscopically uniform tension, and of plane strain polymer unit cell with a cylindrical void under combined straining were investigated by computational simulation with the nonaffine molecular chain network model. The results revealed the onset, evolution and interaction of microscopic shear bands emanating from slightly weak points, and the percolation of new shear bands. The micro- to Macroscopic isotropy of the Deformation response has been verified. Although the existence of distribution of ISS substantially affects the Deformation, the effects of distribution patterns and standard deviation of ISS on the Deformation were small. The interaction between the heterogeneity of ISS and voids substantially affects such micro- to Macroscopic Deformation behavior as onset and propagation of shear bands, mean stress distribution, and Macroscopic stress vs strain relationship.
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Characterization of micro- to Macroscopic Deformation behavior of amorphous polymer with heterogeneous distribution of microstructures
International Journal of Mechanical Sciences, 2003Co-Authors: Yoshihiro Tomita, Makoto UchidaAbstract:In the present study, we clarify the micro- to Macroscopic Deformation behavior of an amorphous polymer with a slightly heterogeneous distribution of molecular chains; in other words, the distribution of the initial shear strength of the polymer. The micro- to Macroscopic Deformation behaviors of polymer under Macroscopically uniform tension and shearing, uniaxial extension of a plane strain block and surface Deformation of the plane strain block under compression were investigated by means of computational simulation with the nonaffine molecular chain network model. The results revealed the onset of microscopic shear bands emanating from slightly weak points and their evolution, and the interaction and percolation of new shear bands. The effects of distribution patterns and standard deviation of initial shear strength on the Deformation, the interaction of weak points, the transition from microscopic shear band formation to Macroscopic neck propagation and the evolution of surface undulation under compression have been demonstrated.
