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Nonlinear Ultrasonic Characterization of Fatigue MicrostructuresDislocation dipole substructures formed during metal fatigue are shown to produce a substantial distortion of ultrasonic waves propagating through the fatigued material. A model of ultrasonic wave-dislocation dipole interactions is developed that quantifies the wave distortion by means of a material nonlinearity parameter (beta). Application of the model to AA2024-T4 predicts a value of p approximately 300% larger in material cyclically loaded for 100 kcycles in stress-control at 276 MPa and R=0 than that measured for virgin material. Experimental measurements show a monotonic increase in p as a function of the number of fatigue cycles that closely approaches the predicted increase. The experiments also suggest that the relevant dislocation substructures are localized in the material.
Document ID
20020036017
Acquisition Source
Langley Research Center
Document Type
Reprint (Version printed in journal)
Authors
Cantrell, John H.
(NASA Langley Research Center Hampton, VA United States)
Yost, William T.
(NASA Langley Research Center Hampton, VA United States)
Date Acquired
August 20, 2013
Publication Date
January 1, 2001
Publication Information
Publication: International Journal of Fatigue
Publisher: Elsevier Sciences Ltd.
Volume: 23
ISSN: 0142-1123
Subject Category
Acoustics
Distribution Limits
Public
Copyright
Other

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