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I. Roman - One of the best experts on this subject based on the ideXlab platform.
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A continuum model for Grain Junctions in polycrystalline aggregate
Mechanics of Materials, 1998Co-Authors: B. Druyanov, I. RomanAbstract:Abstract Experimental results indicate that the material properties in the immediate vicinity of the Grain Junction (GJ) differ substantially from those in the bulk material. It is assumed that the material in a vicinity of GJ is in a specific state, somewhat amorphous, and that an interface exists between the vicinity and the bulk material. Employing Hsieh and Balluffi's (Hsieh, T.E., Balluffi, R.W., 1989. Acta Metall. 37,1637) experimental data, the Laplace pressure at the interface is calculated. The stress field induced by the Laplace pressure at the interface between the GJ and bulk domains is considered. The stresses extend the GJ domain and compress the Grain material. In equilibrium, they decrease as r−2 for r → ∞, where r is the distance from the geometrical center of the GJ to the point under consideration, and as r−1 in the nonequilibrium case. The effect of Grain anisotropy and temperature changes on the generation of shear stresses at Grain boundaries is discussed. The proposed model makes it possible to explain some phenomena specific to GJs from the unified standpoint. It should be helpful for computational modeling.
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A Model for Grain Junction in Polycrystalline Material and Effect of Temperature Changes on Related Phenomena
Solid Mechanics and its Applications, 1Co-Authors: B. Druyanov, I. RomanAbstract:Experimental evidences show that the material properties in an immediate vicinity of a Grain Junction (GJ) significantly differ from those in the bulk material. It is assumed that the material near the GJs is in some sort of a specific phase, and there is an interface between the GJ and the bulk material. Hsieh and Balluffi’s (1989) experimental data allows us to calculate the Laplace pressure at the interface. We consider the stress field induced by the Laplace pressure at the interface between the GJ and the bulk domain. The stresses extend the GJ domain and compress the material of adjacent Grains. In the case of equilibrium they decrease as r−2 for r→∞ where r is the distance from the geometrical center of the GJ to the point under consideration, and as r−1 in the nonequilibrated case. We discuss the effect of Grain anisotropy on the generation of shear stresses at Grain boundaries.
Catalin R. Picu - One of the best experts on this subject based on the ideXlab platform.
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Singularities of an interface crack impinging on a triple Grain Junction
International Journal of Solids and Structures, 1996Co-Authors: Catalin R. PicuAbstract:The crack-tip stress-field singularity of a crack lying along a Grain boundary and impinging on a Grain triple Junction is investigated. The three Grains forming the triple Junction are considered to be made from the same anisotropic material, albeit with different orientations of the principal material axes. The analysis is limited to elastic plane-strain deformation and is carried out using the Eshelby-Stroh formalism for anisotropic elasticity. The effect of the anisotropy on the level of the singularity is investigated for both transversely cubic and orthotropic Grains.
B. Druyanov - One of the best experts on this subject based on the ideXlab platform.
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A continuum model for Grain Junctions in polycrystalline aggregate
Mechanics of Materials, 1998Co-Authors: B. Druyanov, I. RomanAbstract:Abstract Experimental results indicate that the material properties in the immediate vicinity of the Grain Junction (GJ) differ substantially from those in the bulk material. It is assumed that the material in a vicinity of GJ is in a specific state, somewhat amorphous, and that an interface exists between the vicinity and the bulk material. Employing Hsieh and Balluffi's (Hsieh, T.E., Balluffi, R.W., 1989. Acta Metall. 37,1637) experimental data, the Laplace pressure at the interface is calculated. The stress field induced by the Laplace pressure at the interface between the GJ and bulk domains is considered. The stresses extend the GJ domain and compress the Grain material. In equilibrium, they decrease as r−2 for r → ∞, where r is the distance from the geometrical center of the GJ to the point under consideration, and as r−1 in the nonequilibrium case. The effect of Grain anisotropy and temperature changes on the generation of shear stresses at Grain boundaries is discussed. The proposed model makes it possible to explain some phenomena specific to GJs from the unified standpoint. It should be helpful for computational modeling.
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A Model for Grain Junction in Polycrystalline Material and Effect of Temperature Changes on Related Phenomena
Solid Mechanics and its Applications, 1Co-Authors: B. Druyanov, I. RomanAbstract:Experimental evidences show that the material properties in an immediate vicinity of a Grain Junction (GJ) significantly differ from those in the bulk material. It is assumed that the material near the GJs is in some sort of a specific phase, and there is an interface between the GJ and the bulk material. Hsieh and Balluffi’s (1989) experimental data allows us to calculate the Laplace pressure at the interface. We consider the stress field induced by the Laplace pressure at the interface between the GJ and the bulk domain. The stresses extend the GJ domain and compress the material of adjacent Grains. In the case of equilibrium they decrease as r−2 for r→∞ where r is the distance from the geometrical center of the GJ to the point under consideration, and as r−1 in the nonequilibrated case. We discuss the effect of Grain anisotropy on the generation of shear stresses at Grain boundaries.
Marian B. Holness - One of the best experts on this subject based on the ideXlab platform.
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Plagioclase growth rates control three-Grain Junction geometry in dolerites and gabbros
Journal of Petrology, 2015Co-Authors: Marian B. HolnessAbstract:Measurements of dihedral angles at three-Grain Junctions in gabbros, involving two Grains of plagioclase and one Grain of another mineral, demonstrate that the median dihedral angle is generally the same for all minerals in any sample. The few exceptions to this can be attributed to reaction or to the cessation of growth of plagioclase during the last stages of solidification of highly evolved liquids that do not crystallize volumetrically important amounts of plagioclase. The dihedral angle is therefore primarily controlled by the growth behavior of plagioclase in the last remaining liquid. The final value of the dihedral angle is controlled by the extent to which plagioclase growth is accommodated on the (010) faces: low angles form when growth on the (010) faces is minor compared with that on the other growth faces, and high angles form when the (010) faces accommodate significant growth. The response of dihedral angles to changes in crystallization time is therefore explained by the changing response of plagioclase growth to cooling rate, with limited growth on (010) faces during rapid cooling (leading to a low dihedral angle) and more significant growth at slow cooling (leading to high dihedral angle). The correspondence between dihedral angle and plagioclase Grain shape (as quantified by the average apparent aspect ratio observed in thin section) is clearly evident for non-fractionated bodies such as dolerite sills. Although the stratigraphic variation of the overall plagioclase Grain shape in the floor cumulates of the Skaergaard Intrusion is broadly similar to that observed in sills, there is no correspondence to observed augite�plagioclase�plagioclase dihedral angles, which show a step-wise stratigraphic variation, corresponding to changes in the liquidus assemblage. This decoupling occurs because plagioclase growth in layered intrusions occurs in two stages, the first at, or close to, the magma�mush interface and the second within the mush. Chemical maps of samples on either side of the augite-in dihedral angle step demonstrate a step-wise change in the aspect ratio of the plagioclase grown during the second stage, with the aspect ratio of this stage corresponding to that predicted from the dihedral angles. Plagioclase shape in layered intrusions thus records two separate thermal regimes, with the overall shape controlled by the global cooling rate of the intrusion, and the second (minor) stage within the mushy layer reflecting local thermal buffering controlled by the liquidus assemblage of the bulk magma. Dihedral angles in layered intrusions record the second thermal regime.
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Toward an understanding of disequilibrium dihedral angles in mafic rocks
Journal of Geophysical Research: Solid Earth, 2012Co-Authors: Marian B. Holness, Madeleine C. S. Humphreys, Rachel Sides, Rosalind T. Helz, Christian TegnerAbstract:[1] The median dihedral angle at clinopyroxene-plagioclase-plagioclase Junctions in mafic rocks, Θcpp, is generally lower than equilibrium (109° ± 2°). Observation of a wide range of mafic bodies demonstrates that previous work on systematic variations of Θcpp is incorrect in several important respects. First, the spatial distribution of plagioclase compositional zoning demonstrates that the final geometry of three-Grain Junctions, and hence Θcpp, is formed during solidification (the igneous process): sub-solidus textural modification in most dolerites and gabbros, previously thought to be the dominant control on Θcpp, is insignificant. Θcpp is governed by mass transport constraints, the inhibiting effects of small pore size on crystallization, and variation in relative growth rates of pyroxene and plagioclase. During rapid cooling, pyroxene preferentially fills wider pores while the narrower pores remain melt-filled, resulting in an initial value of Θcpp of 78°, rather than 60° which would be expected if all melt-filled pores were filled with pyroxene. Lower cooling rates create a higher initial Θcpp due to changes in relative growth rates of the two minerals at the nascent three-Grain Junction. Low Θcpp (associated with cuspate clinopyroxene Grains at triple Junctions) can also be diagnostic of infiltration of previously melt-free rocks by late-stage evolved liquids (the metasomatic process). Modification of Θcpp by sub-solidus textural equilibration (the metamorphic process) is only important for fine-Grained mafic rocks such as chilled margins and intraplutonic chill zones. In coarse-Grained gabbros from shallow crustal intrusions the metamorphic process occurs only in the centers of oikocrysts, associated with rounding of chadacrysts
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Decoding dihedral angles in melt-bearing and solidified rocks
Journal of the Virtual Explorer, 2010Co-Authors: Marian B. HolnessAbstract:The dihedral angle is the angle subtended between two Grain boundaries at a three-Grain Junction, or the angle between the two liquid-solid interfaces at the corner of a fluid-filled pore. In textural equilibrium the dihedral angle defines the topology, interconnectivity and amount of a liquid phase. Complete textural equilibrium (in terms of uniform Grain size, constant mean curvature of Grain boundaries and balancing of interfacial energies at all three- and four-Grain Junctions) is rare in geological materials, particularly in the crust. Local equilibrium at Grain Junctions (manifest as dihedral angles) is generally seen in monomineralic rocks, in high-grade metamorphic rocks and in the mantle. The distribution of true dihedral angles, as measured using a universal stage, has great potential use in interpretation of rock history. The studies of disequilibrium dihedral angles are currently at the descriptive stage, and further efforts need to be applied to deriving a quantitative understanding of the processes by which, and rates at which, they attain equilibrium.
Sang-joon Kim - One of the best experts on this subject based on the ideXlab platform.
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Effects of the seed distance on the characteristics of the (100)/(100) Junctions of top-seeded melt growth processed YBCO superconductors using two seeds
Physica C-superconductivity and Its Applications, 2000Co-Authors: Chan-joong Kim, Ho-jin Kim, Jinho Joo, Gye-won Hong, Sang-chul Han, Young-hee Han, Tae Hyun Sung, Sang-joon KimAbstract:Abstract The effects of the distance ( d ) between two Sm 1.8 Ba 2.4 Cu 3.4 O x seeds on the characteristics of the (100)/(100) Junctions of top-seeded melt growth (TSMG) processed YBCO superconductors were investigated. The trapped magnetic field at the Grain Junction and the levitation force of the top surface decreased with increasing d value. The degradation of the properties was discussed in terms of the presence of the residual melt-forming phases (CuO and BaCuO 2 ) at the Grain Junction.
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Multiseeding with (100)/(100) Grain Junctions in top-seeded melt growth processed YBCO superconductors
Physica C: Superconductivity, 2000Co-Authors: Chan-joong Kim, Ho-jin Kim, Jinho Joo, Gye-won Hong, Sang-chul Han, Young-hee Han, Tae Hyun Sung, Young A. Jee, Sang-joon KimAbstract:Multiseeding with (100)/(100) Grain Junctions of top-seeded melt growth (TSMG) processed YBCO superconductors was studied. Multiple seeding shortened the processing time for the fabrication of TSMG-processed YBCO superconductors. The relationship among the number of seeds, the levitation forces and the trapped magnetic fields of the TSMG-processed YBCO samples is reported. The characteristic of the (100)/(100) Grain Junction is discussed in terms of a wetting angle of a melt.
