The Experts below are selected from a list of 4731 Experts worldwide ranked by ideXlab platform
Zhenhuan Li - One of the best experts on this subject based on the ideXlab platform.
-
A Dislocation Climb/glide coupled crystal plasticity constitutive model and its finite element implementation
Mechanics of Materials, 2018Co-Authors: Shulin Yuan, Minsheng Huang, Zhenhuan LiAbstract:Abstract The glide and Climb of Dislocations are two important plastic deformation mechanisms of the metallic crystals at elevated temperatures. In this work, a new Dislocation density-based constitutive model for single crystal plasticity with explicit consideration of both Dislocation glide and Climb is presented. Three contributions of Dislocation Climb to the plastic deformation are involved: the kinematics, the Climb-enhanced Dislocation mobility and the Climb-induced Dislocation annihilation. A fully implicit time-integration scheme for this model is given and implemented by a user material subroutine in software ABAQUS. Then, the compression tests of 〈110〉 single crystalline aluminum at high temperature and low strain rate are simulated, showing good agreements with the experimental results. Moreover, this model is used to predict the creep deformation of single crystalline aluminum at different temperatures and applied stress levels. The results show that the present model can capture the power law creep behavior of single crystalline aluminum and the predicted creep exponent falls within the range suggested by earlier research.
-
The influence of vacancies diffusion-induced Dislocation Climb on the creep and plasticity behaviors of nickel-based single crystal superalloy
Computational Materials Science, 2015Co-Authors: Hui Yang, Minsheng Huang, Zhenhuan LiAbstract:Abstract In the nickel-based single crystal superalloys (NBSCSs) that usually works at high temperature, the vacancies diffusion-induced Dislocation Climb is an important creep/plasticity mechanism besides the Dislocation glide. In order to uncover and capture the Dislocation dynamics mechanisms behind primary creep and early plasticity of NBSCSs, the glide-only three-dimensional discrete Dislocation dynamics (3D-DDD) simulation framework is extended by incorporating the vacancies diffusion-induced Climb mechanism. By means of this extended 3D-DDD framework, the Climb-assisted Dislocation glide in the narrow γ matrix channels of NBSCSs is simulated to study the primary creep and early plasticity behaviors of NBSCSs serving at elevated temperature, with special attention on the important role of Dislocation Climb in them. The influences of some important factors, such as ambient temperature, applied stress and vacancy supersaturation, which can directly affect the Dislocation Climb velocity, and the sizes of the two-phase microstructure (i.e., the precipitate size and matrix channel width) on the primary creep of NBSCSs, are studied in detail. In addition, the important role that Dislocation Climb plays in the early plasticity behaviors of NBSCSs, including the strain rate effect and the tension–compression (T–C) asymmetry, is investigated and discussed carefully. Moreover, some Dislocation Climb-induced typical Dislocation configurations and their dynamics evolutions, including the triangular Dislocation loop wrapping around the corner of the precipitate and the Dislocation junctions on the {0 0 1} γ/γ′ interface, are reproduced, in good agreement with the experimental observation and previous computational simulation published.
Alphonse Finel - One of the best experts on this subject based on the ideXlab platform.
-
Multiscale Theory of Dislocation Climb.
Physical review letters, 2015Co-Authors: Pierre-antoine Geslin, Benoît Appolaire, Alphonse FinelAbstract:Dislocation Climb is a ubiquitous mechanism playing a major role in the plastic deformation of crystals at high temperature. We propose a multiscale approach to model quantitatively this mechanism at mesoscopic length and time scales. First, we analyze Climb at a nanoscopic scale and derive an analytical expression of the Climb rate of a jogged Dislocation. Next, we deduce from this expression the activation energy of the process, bringing valuable insights to experimental studies. Finally, we show how to rigorously upscale the Climb rate to a mesoscopic phase-field model of Dislocation Climb. This upscaling procedure opens the way to large scale simulations where Climb processes are quantitatively reproduced even though the mesoscopic length scale of the simulation is orders of magnitude larger than the atomic one.
-
A phase field model for Dislocation Climb
Applied Physics Letters, 2014Co-Authors: Pierre-antoine Geslin, Benoît Appolaire, Alphonse FinelAbstract:We propose a phase field method to model consistently Dislocation Climb by vacancy absorption or emission. It automatically incorporates the exact balance between the vacancy flux and the phase field associated with the Dislocation evolution, enforced by the conserved character of the total population of vacancies. One of its major advantage is the natural introduction of a dynamic coefficient controlling the kinetics of vacancy emission/absorption by the Dislocation. We also derived a closed-form expression of the Climb rate valid from the diffusion-limited to the attachment-limited regimes.
Minsheng Huang - One of the best experts on this subject based on the ideXlab platform.
-
A Dislocation Climb/glide coupled crystal plasticity constitutive model and its finite element implementation
Mechanics of Materials, 2018Co-Authors: Shulin Yuan, Minsheng Huang, Zhenhuan LiAbstract:Abstract The glide and Climb of Dislocations are two important plastic deformation mechanisms of the metallic crystals at elevated temperatures. In this work, a new Dislocation density-based constitutive model for single crystal plasticity with explicit consideration of both Dislocation glide and Climb is presented. Three contributions of Dislocation Climb to the plastic deformation are involved: the kinematics, the Climb-enhanced Dislocation mobility and the Climb-induced Dislocation annihilation. A fully implicit time-integration scheme for this model is given and implemented by a user material subroutine in software ABAQUS. Then, the compression tests of 〈110〉 single crystalline aluminum at high temperature and low strain rate are simulated, showing good agreements with the experimental results. Moreover, this model is used to predict the creep deformation of single crystalline aluminum at different temperatures and applied stress levels. The results show that the present model can capture the power law creep behavior of single crystalline aluminum and the predicted creep exponent falls within the range suggested by earlier research.
-
a Dislocation Climb glide coupled crystal plasticity constitutive model and its finite element implementation
Mechanics of Materials, 2018Co-Authors: Shulin Yuan, Minsheng Huang, Yaxin ZhuAbstract:Abstract The glide and Climb of Dislocations are two important plastic deformation mechanisms of the metallic crystals at elevated temperatures. In this work, a new Dislocation density-based constitutive model for single crystal plasticity with explicit consideration of both Dislocation glide and Climb is presented. Three contributions of Dislocation Climb to the plastic deformation are involved: the kinematics, the Climb-enhanced Dislocation mobility and the Climb-induced Dislocation annihilation. A fully implicit time-integration scheme for this model is given and implemented by a user material subroutine in software ABAQUS. Then, the compression tests of 〈110〉 single crystalline aluminum at high temperature and low strain rate are simulated, showing good agreements with the experimental results. Moreover, this model is used to predict the creep deformation of single crystalline aluminum at different temperatures and applied stress levels. The results show that the present model can capture the power law creep behavior of single crystalline aluminum and the predicted creep exponent falls within the range suggested by earlier research.
-
The influence of vacancies diffusion-induced Dislocation Climb on the creep and plasticity behaviors of nickel-based single crystal superalloy
Computational Materials Science, 2015Co-Authors: Hui Yang, Minsheng Huang, Zhenhuan LiAbstract:Abstract In the nickel-based single crystal superalloys (NBSCSs) that usually works at high temperature, the vacancies diffusion-induced Dislocation Climb is an important creep/plasticity mechanism besides the Dislocation glide. In order to uncover and capture the Dislocation dynamics mechanisms behind primary creep and early plasticity of NBSCSs, the glide-only three-dimensional discrete Dislocation dynamics (3D-DDD) simulation framework is extended by incorporating the vacancies diffusion-induced Climb mechanism. By means of this extended 3D-DDD framework, the Climb-assisted Dislocation glide in the narrow γ matrix channels of NBSCSs is simulated to study the primary creep and early plasticity behaviors of NBSCSs serving at elevated temperature, with special attention on the important role of Dislocation Climb in them. The influences of some important factors, such as ambient temperature, applied stress and vacancy supersaturation, which can directly affect the Dislocation Climb velocity, and the sizes of the two-phase microstructure (i.e., the precipitate size and matrix channel width) on the primary creep of NBSCSs, are studied in detail. In addition, the important role that Dislocation Climb plays in the early plasticity behaviors of NBSCSs, including the strain rate effect and the tension–compression (T–C) asymmetry, is investigated and discussed carefully. Moreover, some Dislocation Climb-induced typical Dislocation configurations and their dynamics evolutions, including the triangular Dislocation loop wrapping around the corner of the precipitate and the Dislocation junctions on the {0 0 1} γ/γ′ interface, are reproduced, in good agreement with the experimental observation and previous computational simulation published.
-
the influence of Dislocation Climb on the mechanical behavior of polycrystals and grain size effect at elevated temperature
International Journal of Plasticity, 2014Co-Authors: Minsheng Huang, Jie TongAbstract:The mechanical behavior of a polycrystalline aluminum in tension was modeled using a Climb-assisted discrete Dislocation dynamics (DDD) technique. Special focus was on how Dislocation Climb influences the flow stress of the polycrystalline aluminum with regard to selected grain sizes at elevated temperature. A periodical representative cell (PRC) consisting of given number of grains was used in the simulations. Results showed that, at the high temperature considered, Dislocation Climb plays an important role in defining the mechanical behavior of the polycrystalline crystal. Specifically, Dislocation Climb decreases significantly the flow stress and hardening rate while increases the Dislocation density by relieving the Dislocation pile-ups against the grain boundaries (GBs). In addition, the grain size effect on the yield stress of polycrystalline aluminum is significantly weakened by Dislocation Climb, especially when the grain size falls in the range of submicron. Another interesting result is that, at high temperature, when both Dislocation Climb and glide are considered, the grain size effect seems to be insignificant with regard to the applied strain rate, although the strength of material increases with enhanced loading rate.
Pierre-antoine Geslin - One of the best experts on this subject based on the ideXlab platform.
-
Multiscale Theory of Dislocation Climb.
Physical review letters, 2015Co-Authors: Pierre-antoine Geslin, Benoît Appolaire, Alphonse FinelAbstract:Dislocation Climb is a ubiquitous mechanism playing a major role in the plastic deformation of crystals at high temperature. We propose a multiscale approach to model quantitatively this mechanism at mesoscopic length and time scales. First, we analyze Climb at a nanoscopic scale and derive an analytical expression of the Climb rate of a jogged Dislocation. Next, we deduce from this expression the activation energy of the process, bringing valuable insights to experimental studies. Finally, we show how to rigorously upscale the Climb rate to a mesoscopic phase-field model of Dislocation Climb. This upscaling procedure opens the way to large scale simulations where Climb processes are quantitatively reproduced even though the mesoscopic length scale of the simulation is orders of magnitude larger than the atomic one.
-
A phase field model for Dislocation Climb
Applied Physics Letters, 2014Co-Authors: Pierre-antoine Geslin, Benoît Appolaire, Alphonse FinelAbstract:We propose a phase field method to model consistently Dislocation Climb by vacancy absorption or emission. It automatically incorporates the exact balance between the vacancy flux and the phase field associated with the Dislocation evolution, enforced by the conserved character of the total population of vacancies. One of its major advantage is the natural introduction of a dynamic coefficient controlling the kinetics of vacancy emission/absorption by the Dislocation. We also derived a closed-form expression of the Climb rate valid from the diffusion-limited to the attachment-limited regimes.
Alexander Hartmaier - One of the best experts on this subject based on the ideXlab platform.
-
3d discrete Dislocation dynamics study of creep behavior in ni base single crystal superalloys by a combined Dislocation Climb and vacancy diffusion model
Journal of The Mechanics and Physics of Solids, 2017Co-Authors: Marc Fivel, Alexander HartmaierAbstract:Abstract A three-dimensional (3D) discrete Dislocation dynamics (DDD) creep model is developed to investigate creep behavior under uniaxial tensile stress along the crystallographic [001] direction in Ni-base single crystal superalloys, which takes explicitly account of Dislocation glide, Climb and vacancy diffusion, but neglects phase transformation like rafting of γ ′ precipitates. The vacancy diffusion model takes internal stresses by Dislocations and mismatch strains into account and it is coupled to the Dislocation dynamics model in a numerically efficient way. This model is helpful for understanding the fundamental creep mechanisms in superalloys and clarifying the effects of Dislocation glide and Climb on creep deformation. In cases where the precipitate cutting rarely occurs, e.g. due to the high anti-phase boundary energy and the lack of superDislocations, the Dislocation glide in the γ matrix and the Dislocation Climb along the γ / γ ′ interface dominate plastic deformation. The simulation results show that a high temperature or a high stress both promote Dislocation motion and multiplication, so as to cause a large creep strain. Dislocation Climb accelerated by high temperature only produces a small plastic strain, but relaxes the hardening caused by the filling γ channels and lets Dislocations further glide and multiply. The strongest variation of vacancy concentration occurs in the horizontal channels, where more mixed Dislocations exit and tend to Climb. The increasing internal stresses due to the increasing Dislocation density are easily overcome by Dislocations under a high external stress that leads to a long-term Dislocation glide accompanied by multiplication.