The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform
Katsuyuki Suzuki - One of the best experts on this subject based on the ideXlab platform.
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atomic simulations to evaluate effects of stacking fault energy on interactions between Edge Dislocation and spherical void in face centred cubic metals
Philosophical Magazine, 2018Co-Authors: K Doihara, Taira Okita, Mitsuhiro Itakura, Masaatsu Aichi, Katsuyuki SuzukiAbstract:In this study, molecular dynamics simulations were performed to elucidate the effects of stacking fault energy (SFE) on the physical interactions between an Edge Dislocation and a spherical void in...
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effects of stacking fault energies on the interaction between an Edge Dislocation and an 8 0 nm diameter frank loop of self interstitial atoms
Nuclear materials and energy, 2016Co-Authors: Sho Hayakawa, Taira Okita, Mitsuhiro Itakura, Katsuyuki Suzuki, Y Hayashi, Y KuriyamaAbstract:Abstract Molecular dynamics simulations were conducted to investigate the effects of stacking fault energy (SFE) as a single variable parameter on the interaction between an Edge Dislocation and a Frank loop of self-interstitial atoms with a diameter of 8.0 nm. The physical contact between the Edge Dislocation and the loop causes constriction of the Edge Dislocation, followed by the formation of a D-Shockley partial Dislocation. The latter process is associated with either the formation of a screw component and its cross-slip, or the direct core reaction between the Dislocation and the loop. These processes induce either the absorption of the loop into the Dislocation or the transformation of the loop into a perfect loop. The SFE influences the interaction morphologies by determining the separation distance of the two partial Dislocations and consequently the rate of constriction. The dependence of the interaction morphology on the SFE varies with the habit plane of the loop. A higher SFE increases the probability of the absorption or transformation interaction; however, only loop shearing is observed at the lower limit of the SFE range of austenitic stainless steels.
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behavior of a self interstitial atom type Dislocation loop in the periphery of an Edge Dislocation in bcc fe
Nuclear materials and energy, 2016Co-Authors: Sho Hayakawa, Taira Okita, Mitsuhiro Itakura, Masaatsu Aichi, S Fujita, Katsuyuki SuzukiAbstract:Abstract The behavior of the Dislocation loop of a self-interstitial atom (SIA) near an Edge Dislocation and its conservative climb process were modeled in body-centered cubic Fe by incorporating loop rotation. The stable position of the loop and its rotational angle due to the interaction with an Edge Dislocation were evaluated through molecular dynamics simulations and calculations of the isotropic elasticity. The results were used as input variables in kinetic Monte Carlo simulations to model the absorption of the loop by the Dislocation via a conservative climb. Loop rotation was found to affect the velocity of the conservative climb only at short-distances because the gradient in the interaction energy between the Dislocation and an atom at the Edge of the loop, which is a driving force of the conservative climb, could not be precisely evaluated without loop rotation. Depending on the distance between the Dislocation and the loop, allowing the loop rotation resulted in either an increase or decrease in the velocity of the conservative climb.
D J Bacon - One of the best experts on this subject based on the ideXlab platform.
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Effects of temperature on structure and mobility of the 〈100〉 Edge Dislocation in body-centred cubic iron
Acta Materialia, 2010Co-Authors: D.A. Terentyev, Yuri N. Osetsky, D J BaconAbstract:Dislocation segments with Burgers vector b=〈100〉 are formed during deformation of body-centred-cubic (bcc) metals by the interaction between Dislocations with b=1/2〈111〉. Such segments are also created by reactions between Dislocations and Dislocation loops in irradiated bcc metals. The obstacle resistance produced by these segments on gliding Dislocations is controlled by their mobility, which is determined in turn by the atomic structure of their cores. The core structure of a straight 〈100〉 Edge Dislocation is investigated here by atomic-scale computer simulation for α-iron using three different interatomic potentials. At low temperature the Dislocation has a non-planar core consisting of two 1/2〈111〉 fractional Dislocations with atomic disregistry spread on planes inclined to the main glide plane. Increasing temperature modifies this core structure and so reduces the critical applied shear stress for glide of the 〈100〉 Dislocation. It is concluded that the response of the 〈100〉 Edge Dislocation to temperature or applied stress determines specific reaction pathways occurring between a moving Dislocation and 1/2〈111〉 Dislocation loops. The implications of this for plastic flow in unirradiated and irradiated ferritic materials are discussed and demonstrated by examples.
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computer simulation of interaction of an Edge Dislocation with a carbon interstitial in α iron and effects on glide
Acta Materialia, 2007Co-Authors: K Tapasa, Yu.n. Osetsky, D J BaconAbstract:Abstract The atomic-scale behaviour of a carbon (C) interstitial atom in the core of a 1 / 2 [ 1 1 1 ] ( 1 1 ¯ 0 ) Edge Dislocation in α-iron has been simulated for the first time. C sites with high binding energy to the Dislocation have been investigated and the critical stress, τc, for the Dislocation to overcome a row of C atoms determined. The effects of temperature, T, and applied strain rate, e ˙ , on τc have been studied. τc decreases rapidly as T increases to ∼400 K and becomes almost constant at higher T. It decreases with decreasing e ˙ and is e ˙ -independent at T greater than ∼300 K. The activation parameters in simulation conditions have been obtained. The activation distance of ∼(0.2–0.3)b is consistent with point-obstacle strengthening. However, the activation energy is only ∼5kBT, where kB is the Boltzmann constant, and ∼20kBT smaller than that realized in experimental conditions. This implies that the decline of τc over the range 0 to ∼400 K would occur over 0 to ∼80 K in experiment, which is where C-Edge Dislocation effects would be influential. A few jumps of C occur in the core before Dislocation unpinning at T ⩾ 800 K and give a small T-dependence of τc. Core diffusion of C occurs by ± 1 / 2 [ 1 1 1 ¯ ] jumps at 70.5° to [1 1 1]. The diffusivity in the absence of applied stress is 4 × 10−9exp(−0.2 eV/kBT) m2/s compared with 1.9 × 10−7exp(−0.7 eV/kBT) m2/s for bulk diffusion of C in the same MD model. Hence, the Edge Dislocation provides a path for rapid diffusion of C, but net transport along the core can only occur by motion of the Dislocation itself.
Mitsuhiro Itakura - One of the best experts on this subject based on the ideXlab platform.
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atomic simulations to evaluate effects of stacking fault energy on interactions between Edge Dislocation and spherical void in face centred cubic metals
Philosophical Magazine, 2018Co-Authors: K Doihara, Taira Okita, Mitsuhiro Itakura, Masaatsu Aichi, Katsuyuki SuzukiAbstract:In this study, molecular dynamics simulations were performed to elucidate the effects of stacking fault energy (SFE) on the physical interactions between an Edge Dislocation and a spherical void in...
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effects of stacking fault energies on the interaction between an Edge Dislocation and an 8 0 nm diameter frank loop of self interstitial atoms
Nuclear materials and energy, 2016Co-Authors: Sho Hayakawa, Taira Okita, Mitsuhiro Itakura, Katsuyuki Suzuki, Y Hayashi, Y KuriyamaAbstract:Abstract Molecular dynamics simulations were conducted to investigate the effects of stacking fault energy (SFE) as a single variable parameter on the interaction between an Edge Dislocation and a Frank loop of self-interstitial atoms with a diameter of 8.0 nm. The physical contact between the Edge Dislocation and the loop causes constriction of the Edge Dislocation, followed by the formation of a D-Shockley partial Dislocation. The latter process is associated with either the formation of a screw component and its cross-slip, or the direct core reaction between the Dislocation and the loop. These processes induce either the absorption of the loop into the Dislocation or the transformation of the loop into a perfect loop. The SFE influences the interaction morphologies by determining the separation distance of the two partial Dislocations and consequently the rate of constriction. The dependence of the interaction morphology on the SFE varies with the habit plane of the loop. A higher SFE increases the probability of the absorption or transformation interaction; however, only loop shearing is observed at the lower limit of the SFE range of austenitic stainless steels.
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behavior of a self interstitial atom type Dislocation loop in the periphery of an Edge Dislocation in bcc fe
Nuclear materials and energy, 2016Co-Authors: Sho Hayakawa, Taira Okita, Mitsuhiro Itakura, Masaatsu Aichi, S Fujita, Katsuyuki SuzukiAbstract:Abstract The behavior of the Dislocation loop of a self-interstitial atom (SIA) near an Edge Dislocation and its conservative climb process were modeled in body-centered cubic Fe by incorporating loop rotation. The stable position of the loop and its rotational angle due to the interaction with an Edge Dislocation were evaluated through molecular dynamics simulations and calculations of the isotropic elasticity. The results were used as input variables in kinetic Monte Carlo simulations to model the absorption of the loop by the Dislocation via a conservative climb. Loop rotation was found to affect the velocity of the conservative climb only at short-distances because the gradient in the interaction energy between the Dislocation and an atom at the Edge of the loop, which is a driving force of the conservative climb, could not be precisely evaluated without loop rotation. Depending on the distance between the Dislocation and the loop, allowing the loop rotation resulted in either an increase or decrease in the velocity of the conservative climb.
Taira Okita - One of the best experts on this subject based on the ideXlab platform.
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atomic simulations to evaluate effects of stacking fault energy on interactions between Edge Dislocation and spherical void in face centred cubic metals
Philosophical Magazine, 2018Co-Authors: K Doihara, Taira Okita, Mitsuhiro Itakura, Masaatsu Aichi, Katsuyuki SuzukiAbstract:In this study, molecular dynamics simulations were performed to elucidate the effects of stacking fault energy (SFE) on the physical interactions between an Edge Dislocation and a spherical void in...
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effects of stacking fault energies on the interaction between an Edge Dislocation and an 8 0 nm diameter frank loop of self interstitial atoms
Nuclear materials and energy, 2016Co-Authors: Sho Hayakawa, Taira Okita, Mitsuhiro Itakura, Katsuyuki Suzuki, Y Hayashi, Y KuriyamaAbstract:Abstract Molecular dynamics simulations were conducted to investigate the effects of stacking fault energy (SFE) as a single variable parameter on the interaction between an Edge Dislocation and a Frank loop of self-interstitial atoms with a diameter of 8.0 nm. The physical contact between the Edge Dislocation and the loop causes constriction of the Edge Dislocation, followed by the formation of a D-Shockley partial Dislocation. The latter process is associated with either the formation of a screw component and its cross-slip, or the direct core reaction between the Dislocation and the loop. These processes induce either the absorption of the loop into the Dislocation or the transformation of the loop into a perfect loop. The SFE influences the interaction morphologies by determining the separation distance of the two partial Dislocations and consequently the rate of constriction. The dependence of the interaction morphology on the SFE varies with the habit plane of the loop. A higher SFE increases the probability of the absorption or transformation interaction; however, only loop shearing is observed at the lower limit of the SFE range of austenitic stainless steels.
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behavior of a self interstitial atom type Dislocation loop in the periphery of an Edge Dislocation in bcc fe
Nuclear materials and energy, 2016Co-Authors: Sho Hayakawa, Taira Okita, Mitsuhiro Itakura, Masaatsu Aichi, S Fujita, Katsuyuki SuzukiAbstract:Abstract The behavior of the Dislocation loop of a self-interstitial atom (SIA) near an Edge Dislocation and its conservative climb process were modeled in body-centered cubic Fe by incorporating loop rotation. The stable position of the loop and its rotational angle due to the interaction with an Edge Dislocation were evaluated through molecular dynamics simulations and calculations of the isotropic elasticity. The results were used as input variables in kinetic Monte Carlo simulations to model the absorption of the loop by the Dislocation via a conservative climb. Loop rotation was found to affect the velocity of the conservative climb only at short-distances because the gradient in the interaction energy between the Dislocation and an atom at the Edge of the loop, which is a driving force of the conservative climb, could not be precisely evaluated without loop rotation. Depending on the distance between the Dislocation and the loop, allowing the loop rotation resulted in either an increase or decrease in the velocity of the conservative climb.
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the elastic interaction between an Edge Dislocation and a loop in bcc systems
Journal of Nuclear Materials, 2007Co-Authors: Taira Okita, Naoto SekimuraAbstract:We have evaluated the interaction between an Edge Dislocation and a loop in BCC metals. In this calculation, we used the linear elastic theory to estimate their long range interaction, and we incorporated the change in the normal vector of the loop in the stress field originating from the Edge Dislocation. The rotation of the loop significantly modifies the interaction and strongly affects the microstructural evolution and the irradiation hardening.
Qihong Fang - One of the best experts on this subject based on the ideXlab platform.
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effect of interface stresses on the image force and stability of an Edge Dislocation inside a nanoscale cylindrical inclusion
International Journal of Solids and Structures, 2009Co-Authors: Qihong FangAbstract:Dislocation mobility and stability in inclusions can affect the mechanical behaviors of the composites. In this paper, the problem of an Edge Dislocation located within a nanoscale cylindrical inclusion incorporating interface stress is first considered. The explicit expression for the image force acting on the Edge Dislocation is obtained by means of a complex variable method. The influence of the interface effects and the size of the inclusion on the image force is evaluated. The results indicate that the impact of interface stress on the image force and the equilibrium positions of the Edge Dislocation inside the inclusion becomes remarkable when the radius of the inclusion is reduced to nanometer scale. The force acting on the Edge Dislocation produced by the interface stress will increase with the decrease of the radius of the inclusion and depends on the inclusion size which differs from the classical solution. The stability of the Dislocation inside a nanoscale inclusion is also analyzed. The condition of the Dislocation stability and the critical radius of the inclusion are revised for considering interface stresses.
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size dependent interaction between an Edge Dislocation and a nanoscale inhomogeneity with interface effects
Acta Materialia, 2006Co-Authors: Qihong FangAbstract:The influence of the interface stress on the interaction between an Edge Dislocation and a circular nanoscale inhomogeneity is investigated. The explicit solutions are given for stress fields and the image force acting on the Edge Dislocation. The impact of interface properties and the size of the inhomogeneity on the glide/climb force are evaluated. The results show that the local hardening and softening effects at the interface of the nanoscale inhomogeneity due to the interface stress are remarkable and an additional repulsive/attractive force acting on the Dislocation is produced. The normalized glide/climb force increases (decreases) with the decrease of the radius of the inhomogeneity, and the size dependence becomes significant when the radius of the inhomogeneity is reduced to the nanometer scale which differs from the size-independent classical solutions. For some cases, the glide/climb of the Edge Dislocation near the nanoinhomogeneity may be more difficult because more equilibrium locations are present.
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Interaction between an Edge Dislocation and a circular inclusion with interfacial rigid lines
Acta Mechanica, 2005Co-Authors: Qihong Fang, Chiping JiangAbstract:The elastic interaction between an Edge Dislocation and a circular inclusion with interfacial rigid lines is investigated. The Edge Dislocation is located either in the matrix or in the inclusion. Utilizing the complex variable method, the general solutions for the complex potentials in the matrix and the inclusion are obtained. A closed form solution is derived explicitly in the case of an interfacial rigid line. Image forces on the Dislocation are then calculated using the Peach-Koehler formula. The influence of the length of the rigid line and material mismatch on the equilibrium position of the Edge Dislocation near the inclusion is discussed in detail. It is found that a stable equilibrium point may be available when the Edge Dislocation moves to the inclusion from infinity, which differs from the corresponding perfect bonding case.
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Edge Dislocation interacting with an interfacial crack along a circular inhomogeneity
International Journal of Solids and Structures, 2003Co-Authors: Qihong Fang, C P JiangAbstract:Abstract The elastic interaction of an Edge Dislocation, which is located either outside or inside a circular inhomogeneity, with an interfacial crack is dealt with. Using Riemann–Schwarz’s symmetry principle integrated with the analysis of singularity of the complex potentials, the closed form solutions for the elastic fields in the matrix and inhomogeneity regions are derived explicitly. The image force on the Dislocation is then determined by using the Peach–Keohler formula. The influence of the crack geometry and material mismatch on the Dislocation force is evaluated and discussed when the Dislocation is located in the matrix. It is shown that the interfacial crack has significant effect on the equilibrium position of the Edge Dislocation near a circular interface. The results also reveal a strong dependency of the Dislocation force on the mismatch of the shear moduli and Poisson’s ratios between the matrix and inhomogeneity.
