The Experts below are selected from a list of 1914 Experts worldwide ranked by ideXlab platform
D C Ahn - One of the best experts on this subject based on the ideXlab platform.
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void growth by dislocation Loop emission
Journal of Applied Physics, 2007Co-Authors: D C Ahn, Petros Athanasios Sofronis, Mukul Kumar, James Belak, R MinichAbstract:Experimental results from spall tests on aluminum reveal the presence of a dense dislocation structure in an annulus around a void that grew under the tensile pulse when a shock wave was reflected at the free surface of the specimen. The proposition is that dislocation emission from the void surface under load is a viable mechanism for void growth. To understand void growth in the absence of diffusive effects, the Interstitial-Loop emission mechanism under tensile hydrostatic stress is investigated. First, the micromechanics of pile-up formation when Interstitial Loops are emitted from a void under applied macroscopic loading is reviewed. Demand for surface energy expenditure upon void-surface change is taken into consideration. It is demonstrated that in face-centered cubic metals Loop emission from voids with a radius of ∼10 nm is indeed energetically possible in the hydrostatic stress environment generated by shock loading. On the other hand, the levels of hydrostatic stress prevalent in common structural applications are not sufficient to drive Loops at equilibrium positions above a ∼10 nm void. However, for voids larger than about 100 nm, the energetics of Loop emission are easily met as a necessary condition even under the low stress environment prevalent in structural applications.
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on the micromechanics of void growth by prismatic dislocation Loop emission
Journal of The Mechanics and Physics of Solids, 2006Co-Authors: D C Ahn, Petros Athanasios Sofronis, R MinichAbstract:Experimental evidence and recent molecular dynamics simulations of void growth indicate that prismatic dislocation Loop emission by externally applied stresses is a viable mechanism of void growth under shock loading conditions when diffusive processes are given no time to operate. In this paper, the process of growth by Loop emission is studied in a model system comprised of a void in an infinite linearly elastic and isotropic solid loaded axisymmetrically by remote applied stresses. First, the interaction between applied stresses, the stress field of a single dislocation Loop or a pile-up of Loops next to the void, the surface energy expenditure on void surface change, and the lattice resistance to the motion of Loops is reviewed. The necessary condition for Interstitial Loop emission is used to determine the equilibrium positions of the Loops as well as the maximum number of Loops in a pile-up under given applied stresses. For the parameters of the model-material with purely hydrostatic loading, the numerical results yield a volume change for the void, which when normalized by the initial undeformed volume, exhibits a strong dependence on the size of the void for radii less than ∼400 times the lattice Burgers vector. For larger voids, the normalized volume change was found to be independent of the void radius.
R Minich - One of the best experts on this subject based on the ideXlab platform.
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void growth by dislocation Loop emission
Journal of Applied Physics, 2007Co-Authors: D C Ahn, Petros Athanasios Sofronis, Mukul Kumar, James Belak, R MinichAbstract:Experimental results from spall tests on aluminum reveal the presence of a dense dislocation structure in an annulus around a void that grew under the tensile pulse when a shock wave was reflected at the free surface of the specimen. The proposition is that dislocation emission from the void surface under load is a viable mechanism for void growth. To understand void growth in the absence of diffusive effects, the Interstitial-Loop emission mechanism under tensile hydrostatic stress is investigated. First, the micromechanics of pile-up formation when Interstitial Loops are emitted from a void under applied macroscopic loading is reviewed. Demand for surface energy expenditure upon void-surface change is taken into consideration. It is demonstrated that in face-centered cubic metals Loop emission from voids with a radius of ∼10 nm is indeed energetically possible in the hydrostatic stress environment generated by shock loading. On the other hand, the levels of hydrostatic stress prevalent in common structural applications are not sufficient to drive Loops at equilibrium positions above a ∼10 nm void. However, for voids larger than about 100 nm, the energetics of Loop emission are easily met as a necessary condition even under the low stress environment prevalent in structural applications.
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on the micromechanics of void growth by prismatic dislocation Loop emission
Journal of The Mechanics and Physics of Solids, 2006Co-Authors: D C Ahn, Petros Athanasios Sofronis, R MinichAbstract:Experimental evidence and recent molecular dynamics simulations of void growth indicate that prismatic dislocation Loop emission by externally applied stresses is a viable mechanism of void growth under shock loading conditions when diffusive processes are given no time to operate. In this paper, the process of growth by Loop emission is studied in a model system comprised of a void in an infinite linearly elastic and isotropic solid loaded axisymmetrically by remote applied stresses. First, the interaction between applied stresses, the stress field of a single dislocation Loop or a pile-up of Loops next to the void, the surface energy expenditure on void surface change, and the lattice resistance to the motion of Loops is reviewed. The necessary condition for Interstitial Loop emission is used to determine the equilibrium positions of the Loops as well as the maximum number of Loops in a pile-up under given applied stresses. For the parameters of the model-material with purely hydrostatic loading, the numerical results yield a volume change for the void, which when normalized by the initial undeformed volume, exhibits a strong dependence on the size of the void for radii less than ∼400 times the lattice Burgers vector. For larger voids, the normalized volume change was found to be independent of the void radius.
Dmitry Terentyev - One of the best experts on this subject based on the ideXlab platform.
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Solving the puzzle of 100 Interstitial Loop Formation in bcc Iron
Physical Review Letters, 2013Co-Authors: Haixuan Xu, Roger E. Stoller, Yuri N. Osetsky, Dmitry TerentyevAbstract:The Interstitial Loop is a unique signature of radiation damage in structural materials for nuclear and other advanced energy systems. Unlike other bcc metals, two types of Interstitial Loops, 1/2 < 111 > and < 100 >, are formed in bcc iron and its alloys. However, the mechanism by which < 100 > Interstitial dislocation Loops are formed has remained undetermined since they were first observed more than fifty years ago. We describe our atomistic simulations that have provided the first direct observation of < 100 > Loop formation. The process was initially observed using our self-evolving atomistic kinetic Monte Carlo method, and subsequently confirmed using molecular dynamics simulations. Formation of < 100 > Loops involves a distinctly atomistic interaction between two 1/2 < 111 > Loops, and does not follow the conventional assumption of dislocation theory, which is Burgers vector conservation between the reactants and the product. The process observed is different from all previously proposed mechanisms. Thus, our observations might provide a direct link between experiments and simulations and new insights into defect formation that may provide a basis to increase the radiation resistance of these strategic materials.
Petros Athanasios Sofronis - One of the best experts on this subject based on the ideXlab platform.
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void growth by dislocation Loop emission
Journal of Applied Physics, 2007Co-Authors: D C Ahn, Petros Athanasios Sofronis, Mukul Kumar, James Belak, R MinichAbstract:Experimental results from spall tests on aluminum reveal the presence of a dense dislocation structure in an annulus around a void that grew under the tensile pulse when a shock wave was reflected at the free surface of the specimen. The proposition is that dislocation emission from the void surface under load is a viable mechanism for void growth. To understand void growth in the absence of diffusive effects, the Interstitial-Loop emission mechanism under tensile hydrostatic stress is investigated. First, the micromechanics of pile-up formation when Interstitial Loops are emitted from a void under applied macroscopic loading is reviewed. Demand for surface energy expenditure upon void-surface change is taken into consideration. It is demonstrated that in face-centered cubic metals Loop emission from voids with a radius of ∼10 nm is indeed energetically possible in the hydrostatic stress environment generated by shock loading. On the other hand, the levels of hydrostatic stress prevalent in common structural applications are not sufficient to drive Loops at equilibrium positions above a ∼10 nm void. However, for voids larger than about 100 nm, the energetics of Loop emission are easily met as a necessary condition even under the low stress environment prevalent in structural applications.
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on the micromechanics of void growth by prismatic dislocation Loop emission
Journal of The Mechanics and Physics of Solids, 2006Co-Authors: D C Ahn, Petros Athanasios Sofronis, R MinichAbstract:Experimental evidence and recent molecular dynamics simulations of void growth indicate that prismatic dislocation Loop emission by externally applied stresses is a viable mechanism of void growth under shock loading conditions when diffusive processes are given no time to operate. In this paper, the process of growth by Loop emission is studied in a model system comprised of a void in an infinite linearly elastic and isotropic solid loaded axisymmetrically by remote applied stresses. First, the interaction between applied stresses, the stress field of a single dislocation Loop or a pile-up of Loops next to the void, the surface energy expenditure on void surface change, and the lattice resistance to the motion of Loops is reviewed. The necessary condition for Interstitial Loop emission is used to determine the equilibrium positions of the Loops as well as the maximum number of Loops in a pile-up under given applied stresses. For the parameters of the model-material with purely hydrostatic loading, the numerical results yield a volume change for the void, which when normalized by the initial undeformed volume, exhibits a strong dependence on the size of the void for radii less than ∼400 times the lattice Burgers vector. For larger voids, the normalized volume change was found to be independent of the void radius.
Yuri N. Osetsky - One of the best experts on this subject based on the ideXlab platform.
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Interstitial Loop transformations in FeCr
Journal of Alloys and Compounds, 2015Co-Authors: Laurent Karim Béland, Yuri N. Osetsky, Roger E. StollerAbstract:Abstract We improve the Self-Evolving Atomistic Kinetic Monte Carlo (SEAKMC) algorithm by integrating the Activation Relaxation Technique nouveau (ARTn), a powerful open-ended saddle-point search method, into the algorithm. We use it to investigate the reaction of 37-Interstitial 1/2[1 1 1] and 1/2[ 1 ‾ 1 ‾ 1 ] Loops in FeCr at 10 at.% Cr. They transform into 1/2[1 1 1], 1/2[ 1 ‾ 1 ‾ 1 ], [1 0 0] and [0 1 0] 74-Interstitial clusters with an overall barrier of 0.85 eV. We find that Cr decoration locally inhibits the rotation of crowdions, which dictates the final Loop orientation. The final Loop orientation depends on the details of the Cr decoration. Generally, a region of a given orientation is favored if Cr near its interface with a region of another orientation is able to inhibit reorientation at this interface more than the Cr present at the other interfaces. We also find that substitutional Cr atoms can diffuse from energetically unfavorable to energetically favorable sites within the interlocked 37-Interstitial Loops conformation with barriers of less than 0.35 eV.
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Solving the puzzle of 100 Interstitial Loop Formation in bcc Iron
Physical Review Letters, 2013Co-Authors: Haixuan Xu, Roger E. Stoller, Yuri N. Osetsky, Dmitry TerentyevAbstract:The Interstitial Loop is a unique signature of radiation damage in structural materials for nuclear and other advanced energy systems. Unlike other bcc metals, two types of Interstitial Loops, 1/2 < 111 > and < 100 >, are formed in bcc iron and its alloys. However, the mechanism by which < 100 > Interstitial dislocation Loops are formed has remained undetermined since they were first observed more than fifty years ago. We describe our atomistic simulations that have provided the first direct observation of < 100 > Loop formation. The process was initially observed using our self-evolving atomistic kinetic Monte Carlo method, and subsequently confirmed using molecular dynamics simulations. Formation of < 100 > Loops involves a distinctly atomistic interaction between two 1/2 < 111 > Loops, and does not follow the conventional assumption of dislocation theory, which is Burgers vector conservation between the reactants and the product. The process observed is different from all previously proposed mechanisms. Thus, our observations might provide a direct link between experiments and simulations and new insights into defect formation that may provide a basis to increase the radiation resistance of these strategic materials.
