Dislocation Activity, Stable Crack Motion, and the Warm-Prestressing Effect in Magnesium Oxide

Autor:	BOOTH, A, ROBERTS, S, Booth, Andrew S., Roberts, Steven G.
Rok vydání:	1994
Předmět:	Crack closure Materials science Fracture toughness Electromagnetic shielding Metallurgy Materials Chemistry Ceramics and Composites Fracture (geology) Fracture mechanics Dislocation Composite material Crack growth resistance curve Crystallographic defect
Zdroj:	Journal of the American Ceramic Society. 77:1457-1466
ISSN:	1551-2916 0002-7820
DOI:	10.1111/j.1151-2916.1994.tb09743.x
Popis:	Four-point bend tests were performed on precracked single-crystal MgO specimens at different temperatures and strain rates. A large amount of stable crack growth before fracture occurred; etching revealed dislocations in the crack advance region. The authors believe that dislocation sources near the crack tip emit loops, producing shielding and antishielding dislocations; the latter promote crack advance by a repeated microcleavage mechanism. Warm-prestressing'' experiments, which improve the room-temperature fracture toughness by dislocation shielding, were performed. There was a prestress below which no warm-prestressing effect'' (WPSE) was exhibited and the magnitude of the WPSE increased with increasing prestressing temperature.
Databáze:	OpenAIRE
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