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Flaws Responsible for Slow Cracking in the Delayed Fracture of Alumina
Author(s) -
SINES GEORGE,
OKADA TATSUO
Publication year - 1983
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.1151-2916.1983.tb10024.x
Subject(s) - cracking , materials science , coalescence (physics) , intergranular corrosion , scanning electron microscope , fracture (geology) , composite material , fracture mechanics , fractography , forensic engineering , microstructure , physics , astrobiology , engineering
The early stages of crack extension from inherent flaws were observed directly in order to identify flaws responsible for crack initiation. The specimen surface was immersed in fluorescent dye penetrant while cracks were forming; this procedure allowed the dye to penetrate into the fine cracks. Once the cracking sites were located, scanning electron microscopy was used to identify the flaws. An eccentrically loaded column testing system was used to produce a number of crack initiations on a surface of a specimen without causing catastrophic failure of the specimen. There were many inherent flaws which, either by themselves or as an assembly, became potential crack origins. The initial stage of delayed fracture was shown to involve the interaction and coalescence of nearby flaws with intergranular cracking. It was also found that the crack origins were multiple in delayed fracture.