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Estimation of crack closure stresses for in situ toughened silicon nitride with 8 wt pct scandiaAn 8-wt pct-scandia silicon nitride with an elongated grain structure was fabricated. The material exhibited high fracture toughness and a rising R-curve as measured by the indentation strength technique. The 'toughening' exponent m was found to be m about 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 a function of crack size from the R-curve data, with an arbitrarily assumed distribution function.
Document ID
19920060854
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Choi, Sung R.
(NASA Lewis Research Center; Cleveland State University OH, United States)
Salem, Jonathan A.
(NASA Lewis Research Center Cleveland, OH, United States)
Sanders, William A.
(Analex Corp. Brook Park, OH, United States)
Date Acquired
August 15, 2013
Publication Date
June 1, 1992
Publication Information
Publication: American Ceramic Society, Journal
Volume: 75
Issue: 6, Ju
ISSN: 0002-7820
Subject Category
Nonmetallic Materials
Accession Number
92A43478
Distribution Limits
Public
Copyright
Other

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