ISSN: 1546-962X
CODEN: JAIOAD
Published Online: 1 November 2004
Page Count: 21

Multi-Mechanism Synergy in Variable-Amplitude Fatigue

Sunder, R
BiSS Research, Bangalore,

Ashbaugh, NE
University of Dayton Research Institute, Dayton, OH

Porter, WJ
University of Dayton Research Institute, Dayton, OH

Rosenberger, AH
Air Force Research Laboratory (AFRL/MLLN), Wright-Patterson AFB, OH

(Received 12 July 2002; accepted 12 November 2003)

Abstract

Fractographic studies on Al alloys and a nickel-base super-alloy point to the combined action of three major load-interaction mechanisms in controlling crack growth under variable-amplitude loading. These are crack closure, residual stress, and crack front incompatibility. Crack front incompatibility attenuates crack tip response to applied load and can also increase crack closure stress. Notch root residual stress affects crack closure, while crack tip residual stress moderates environment-enhanced fatigue crack extension. The latter effect disappears in vacuum. Experiments designed to isolate the effect of individual mechanisms provide a framework to model their synergistic action, consistent with microscopic observations of crack growth bands in variable amplitude fatigue.

Keywords:
crack growth mechanisms, thresholds, residual stress effect, crack closure, crack front incompatibility

Paper ID: JAI19065
DOI: 10.1520/JAI19065
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