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Estimation of Crack Closure Stresses for In Situ Toughened Silicon Nitride with 8 wt% Scandia
Author(s) -
Choi Sung R.,
Salem Jonathan A.,
Sanders William A.
Publication year - 1992
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.1151-2916.1992.tb04217.x
Subject(s) - materials science , fracture toughness , composite material , silicon nitride , indentation , toughening , bridging (networking) , fracture mechanics , toughness , crack closure , stress intensity factor , crack growth resistance curve , computer network , layer (electronics) , computer science
An 8‐wt%‐scandia silicon nitride with an elongated grain structure was fabricated. The material exhibited high fracture toughness (∼ 7 MPa · m 1/2 ) and a rising R ‐curve as measured by the indentation strength technique. The “toughening” exponent m was found to be m ∼ 0.1. The high fracture toughness and R ‐curve behavior was attributed mainly to bridging of the crack faces by the elongated grains. The crack closure (bridging) stress distribution in the wake region of the crack tip was estimated as afunction of crack size from the R ‐curve data, with an arbitrarily assumed distribution function.