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High temperature low cycle fatigue mechanisms for nickel base and a copper base alloyDamage mechanisms were studied in Rene' 95 and NARloy Z, using optical, scanning and transmission in microscopy. In necklace Rene' 95, crack initiation was mainly associated with cracking of surface MC carbides, except for hold time tests at higher strain ranges where initiation was associated more with a grain boundary mechanism. A mixed mode of propagation with a faceted fracture morphology was typical for all cycle characters. The dependence of life on maximum tensile stress can be demonstrated by the data falling onto three lines corresponding to the three tensile hold times, in the life against maximum tensile stress plot. In NARloy Z, crack initiation was always at the grain boundaries. The mode of crack propagation depended on the cycle character. The life decreased with decreasing strain rate and with tensile holds. In terms of damage mode, different life prediction laws may be applicable to different cycle characters.
Document ID
19820018560
Acquisition Source
Legacy CDMS
Document Type
Thesis/Dissertation
Authors
Shih, C. I. (Cincinnati Univ. OH, United States)
Date Acquired
September 4, 2013
Publication Date
June 1, 1982
Publication Information
Publisher: NASA
Subject Category
Metallic Materials
Report/Patent Number
NAS 1.26:3543
NASA-CR-3543
Accession Number
82N26436
Funding Number(s)
PROJECT: RTOP 505-33-22
CONTRACT_GRANT: NSG-3263
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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