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TECHNICAL PAPERS

K Variations and Anisotropy: Microstructure Effect and Numerical Predictions

[+] Author and Article Information
Xu-Dong Li

School of Materials Science and Engineering, Gansu University of Technology, 85 Lan Gong Ping, Lanzhou, Gansu Province, 730050, P. R. China

J. Eng. Mater. Technol 125(1), 65-74 (Dec 31, 2002) (10 pages) doi:10.1115/1.1525252 History: Received June 05, 2002; Revised August 20, 2002; Online December 31, 2002
Copyright © 2003 by ASME
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References

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Figures

Grahic Jump Location
A simulated polycrystalline aggregate consisting of 2114 arbitrarily polygon-shaped grains. Planar microcracks of different sizes are embedded in the aggregate of infinite medium. D denotes average grain size of the aggregate (D=10 microns). The dashed lines within Fig. 1 indicate microcracks of different sizes.
Grahic Jump Location
Schematic illustration of broken grains (a) of varying crystallographic orientation with respect to loading direction; (b) in which reference and local crystallite co-ordinate frames are defined.
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(a) Illustration of numerical grids and refinement of boundary elements used to mesh the crack domain. Locations of centroid of elements are presented; (b) Illustration of an element shared by grains and shared area
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Duplicated local microstructure and mesoscopic stress distribution. (a) a microcrack of 2c/D=5 and broken grains; (b) spatial grain modulus ratios in grains intersected by the crack front; (c) appearance of computationally-scanned image of distribution of grain anisotropy ratio in broken grains; and (d) image of distribution of mesoscopic stress the broken grains.
Grahic Jump Location
Illustration of grain geometry effect on K-Ratio evolution along a microcrack front. (a) The geometry effect imposes strong disturbances if grain shapes are treated differently rather than identically. (b) The grain geometry effect increases if the crack size is smaller.
Grahic Jump Location
Demonstration, by (a) and (b), of the dependence of K Variation on local mesoscopic stress in intersected grains for a smaller crack (2c/D=5). (c) the effect of crystal anisotropy on K variations and deviations of anisotropic K away from isotropic counterparts.
Grahic Jump Location
Crack size effect on K variation along the crack front (Ni material)
Grahic Jump Location
Quantitative assessment of local dependence of anisotropic K for a crack of 2c/D=48. (a,d) inhomogeneous mesoscopic stress distributions due respectively to random and local preferential crystallographic orientations in grains nearby the location Q; (b,e) indications of contribution of 200 broken grains, closer to the location Q, to the anisotropic K; (c,f) local contribution per broken-grain-area in the 200 grains (the grain ID is indicated in a pair of brackets).

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