Crack tip deformation in LiF: Mode I and II cracks on (100) and (110) crystal planes

Conference · · TMS (The Metallurgical Society) Paper Selection; (USA)

OSTI ID:5448129

Chia, K Y; Burns, S J ^[1]

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1. Univ. of Rochester, NY (USA)

Optical observations of etched crack tips in LiF single crystals have shown dislocations associated with mode I and Mode II crack tip stresses. The geometric distributions of edge type dislocations around (110) and (100) cleavage cracks are restricted by the limited number of available (110) slip planes. Mode I loaded cracks on (110) and (100) planes are blunted by edge dislocations. Mode II loading crack tips seem to advance unblunted, but shielded, by edge dislocations on the crack plane. This deformation is observed by a multiple etching/fracturing technique. A second type mode I, (100) crack tip deformation is formed by pile-ups of screw dislocations which form a unique crack-dislocation lock at the crack tip. Unloading effects on this crack tip deformation have also been experimentally studied. It is found that unloading contributes to deformation in the crack tip region. A simple but easy-to-understand model is proposed that explains deformation during unloading.

• OSTI ID: 5448129
• Report Number(s): CONF-840909--
• Conference Information: Journal Name: TMS (The Metallurgical Society) Paper Selection; (USA) Journal Volume: 56
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
ALKALI METAL COMPOUNDS
CRACKS
CRYSTAL DEFECTS
CRYSTAL LATTICES
CRYSTAL STRUCTURE
CRYSTALS
DEFORMATION
DISLOCATIONS
DISTRIBUTION
EDGE DISLOCATIONS
FLUORIDES
FLUORINE COMPOUNDS
FRACTURE MECHANICS
HALIDES
HALOGEN COMPOUNDS
LINE DEFECTS
LITHIUM COMPOUNDS
LITHIUM FLUORIDES
LITHIUM HALIDES
MATHEMATICAL MODELS
MECHANICS
SCREW DISLOCATIONS
SLIP
STRESSES