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Fatigue Crack Characterization by Ultrasonic Inspection

出版	ASTM International, 1990
URL	http://books.google.com.hk/books?id=7kN1zgEACAAJ&hl=&source=gbs_api

註釋The ultrasonic interrogation of components for the detection and sizing of defects has advantages over other techniques in that surface as well as subsurface defects can be probed. However, the phenomenon of crack closure or crack surface contact can reduce the detectability of a crack and lead to erroneous crack sizing. The significance of crack closure is twofold: (1) It is important for the interpretation of fatigue data, in particular as affected by the stress ratio, by spike overloads/underloads, and by threshold effects. (2) It affects the detection probability of fatigue cracks, which influences strongly the capability for accurate life prediction. In the present paper, the interaction of ultrasound with fatigue cracks will be discussed with primary emphasis on the first objective.