Some aspects of forces and fields in atomic models of crack tips

Journal Article · Sun Dec 01 00:00:00 EST 1991 · Journal of Materials Research; (United States)

DOI:https://doi.org/10.1557/JMR.1991.2565· OSTI ID:5504918

Hoagland, R G ^[1]; Daw, M S ^[2]; Hirth, J P ^[1]

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1. Washington State University, Pullman, Washington 99164-2920 (United States)
2. Sandia National Laboratories, Livermore, California 94551-0969 (United States)

This paper examines the stresses and displacement gradients in atomistic models of cracks based on an EAM potential devised for aluminum. Methods for computing these quantities are described. Results are presented for two models differing in terms of the orientations of the crack relative to the crystal, a (100)(010) orientation that behaves in a brittle fashion and a (111)(110) orientation which emits partial dislocations prior to extending. Both models display lattice trapping. The stresses in the brittle crack model are compared with the linear elastic prediction and found to be in remarkably good agreement to within distances of about one lattice parameter of the crack tip and at the free surface where contributions from sources other than strain energy (e.g., surface tension) influence the results. Similar results are observed for the ductile model until dislocation emission occurs. The largest stresses that develop just prior to crack extension or dislocation emission are used to estimate the ratio of theoretical tensile strength to shear strength in this material. Eshelby's conservation integrals, {bold F} and {ital M}, are also computed. {bold F} is found to be essentially contour independent and in agreement with the linear elastic prediction in both models until dislocation emission occurs, at which point a large screening contribution arises from the emitted partials. The contour size dependence of {ital M} reveals some interesting features of the crack tip including a slight wobble of the crack tip inside its potential well with changing applied {ital K} and the existence of forces acting to move the crack faces apart as blunting occurs.

• DOE Contract Number: FG06-87ER45287
• OSTI ID: 5504918
• Journal Information: Journal of Materials Research; (United States), Vol. 6:12; ISSN 0884-2914
• Country of Publication: United States
• Language: English

Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
BARIUM OXIDES
GRAIN BOUNDARIES
COPPER OXIDES
HIGH-TC SUPERCONDUCTORS
YTTRIUM OXIDES
CRITICAL CURRENT
ORIENTATION
STRUCTURAL MODELS
TEXTURE
TRANSMISSION ELECTRON MICROSCOPY
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
CHALCOGENIDES
COPPER COMPOUNDS
CRYSTAL STRUCTURE
CURRENTS
ELECTRIC CURRENTS
ELECTRON MICROSCOPY
MICROSCOPY
MICROSTRUCTURE
OXIDES
OXYGEN COMPOUNDS
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
665000* - Physics of Condensed Matter- (1992-)