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Mixed‐Mode Fracture in Soda‐Lime Glass Using Indentation Flaws
Author(s) -
GLAESEMANN G. SCOTT,
RITTER JOHN E.,
JAKUS KARL
Publication year - 1987
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1987.tb05731.x
Subject(s) - materials science , indentation , composite material , crack closure , perpendicular , residual stress , crack growth resistance curve , stress intensity factor , fracture mechanics , stress concentration , stress (linguistics) , fracture (geology) , crack tip opening displacement , structural engineering , geometry , mathematics , linguistics , philosophy , engineering
Mixed‐mode failure of soda‐lime glass under inert and fatigue test conditions was studied using Knoop indentation flaws. For annealed cracks (residual stress‐free) crack extension (catastrophic or subcritical) is by an abrupt transition from the initial crack plane to a noncoplanar crack plane followed by a reorientation of the crack normal to the applied stress. Although fatigue strength of these inclined flaws increased linearly with respect to orientation of the flaws to the applied stress up to an angle of 60°, this increase was considerably less than what was predicted by existing theories. It is believed that subcritical crack growth causes the crack to be realigned perpendicular to the applied stress before failure for all orientations; hence, fatigue strength does not show the dramatic increase at orientation angles as predicted by theory. For as‐indented cracks the contact residual stress causes the crack extension to be less inclined to the initial crack plane than for annealed cracks, but in this case also, the crack realigns itself perpendicular to the applied stress. Again, fatigue strength is relatively insensitive to the orientation angle as predicted by theory and subcritical crack growth is believed to play a primary role in determining this strength dependency.