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Fatigue damage accumulation in nickel prior to crack initiationThe accumulation of lattice defects during fatigue cycling of nickel was investigated by electrical resistivity measurements, positron annihilation lifetime spectroscopy and transmission electron microscopy. Dislocations and vacancy clusters were found to be the main defect types. During cycling of axial and flexural samples at constant load amplitude, the dislocations form a saturated structure early in the fatigue life. This saturated structure consists of a cellular dislocation matrix, in which persistent slip bands (PSBs) begin to operate after the saturation has been established. Vacancies and vacancy clusters are formed during fatigue as a consequence of repetitive dislocation glide in the PSB structure. When PSBs operate, the matrix is assumed to be dormant, allowing vacancies to accumulate preferentially in the PSBs. The increase in vacancy concentration then accounts for the monotonic accumulation of fatigue damage, which points to the importance of vacancy accumulation as a precursor to crack nucleation.
Document ID
19920051323
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Grobstein, T. L.
(NASA Lewis Research Center; Case Western Reserve University Cleveland, OH, United States)
Sivashankaran, S.
(NASA Lewis Research Center Cleveland, OH, United States)
Welsch, G.
(NASA Lewis Research Center Cleveland, OH, United States)
Panigrahi, N.
(NASA Lewis Research Center Cleveland, OH, United States)
Mcgervey, J. D.
(Case Western Reserve University Cleveland, OH, United States)
Blue, J. W.
(NASA Lewis Research Center Cleveland; Cleveland Clinic Foundation, OH, United States)
Date Acquired
August 15, 2013
Publication Date
January 1, 1991
Publication Information
Publication: Materials Science and Engineering, Part A - Structural Materials: Properties, Microstructure and Processing
Volume: A138
ISSN: 0921-5093
Subject Category
Metallic Materials
Accession Number
92A33947
Distribution Limits
Public
Copyright
Other

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