Fracture toughness of materials

Technical Report · Fri Jan 01 04:00:00 EST 1988

DOI:https://doi.org/10.2172/6493240· OSTI ID:6493240

Burns, S J

Crack tip dislocation emission in bulk specimens have been measured in single crystal specimens and the measurements are well below the accepted theoretical values for dislocation emission. The image forces on a dislocation due to the presence of a semi-infinite crack are used to calculate the potential energy of the dislocation around the crack. Expressions for the radial and tangential forces and for slip and climb forces have been found. Crack tip deformation in Mode I and Mode II fractures on both {l brace}100{r brace} and {l brace}110{r brace} planes have been observed in crystals of LiF. The deformation is shown to nearly completely shield {l brace}110{r brace} plane cracks and prevent their propagation while deformation is less effective in shielding {l brace}100{r brace} plane cracks. The fracture toughness of MgO-partially-stabilized ZrO{sub 2} exhibiting transformation toughening been measured. The equations of linear elastic fracture mechanics have been self-consistantly formulated to include the residual displacement from the transformation wake. MgO single crystals were fatigued in plastic strain control at elevated temperatures. At high temperatures, dense bundles of dislocations were observed in transmission electron microscopy aligned perpendicular to the Burgers' vector directions. The thermodynamics of a superconducting second order phase transformation has been related to jumps in physical properties. A simple energy balance, without assuming an equation of state, is used to relate the rate of change of state variables to measurable physical properties. There are no preconceived assumptions about the superconducting mechanism.

• Research Organization: Rochester Univ., NY (USA). Dept. of Mechanical Engineering
• Sponsoring Organization: DOE/ER
• DOE Contract Number: FG02-84ER45051
• OSTI ID: 6493240
• Report Number(s): DOE/ER/45051-3; ON: DE91001305
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360203* -- Ceramics
Cermets
& Refractories-- Mechanical Properties
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
CHALCOGENIDES
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DEFORMATION
DISLOCATIONS
DOCUMENT TYPES
FLUORIDES
FLUORINE COMPOUNDS
FRACTURE PROPERTIES
HALIDES
HALOGEN COMPOUNDS
HIGH-TC SUPERCONDUCTORS
LINE DEFECTS
LITHIUM COMPOUNDS
LITHIUM FLUORIDES
LITHIUM HALIDES
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
MECHANICAL PROPERTIES
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PROGRESS REPORT
SUPERCONDUCTORS
THERMODYNAMICS
TRANSITION ELEMENT COMPOUNDS
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES