SEDL / STP / STP982-EB / STP27231S

Using Acoustic Waves for the Characterization of Closed Fatigue Cracks

Buck, O
Professor and senior scientist, professor and project director, and associate metallurgist, Ames Laboratory, Iowa State University, Ames, IA

Thompson, RB
Professor and senior scientist, professor and project director, and associate metallurgist, Ames Laboratory, Iowa State University, Ames, IA

Rehbein, DK
Professor and senior scientist, professor and project director, and associate metallurgist, Ames Laboratory, Iowa State University, Ames, IA

Pages: 12    Published: Jan 1988

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Abstract

Partial contact of two rough fatigue crack surfaces leads to transmission, reflection, diffraction, and mode conversion of an acoustic signal at those contacts (asperities). This paper reviews recent experimental and theoretical efforts to understand such interactions and uses them to quantify in greater detail the contact between actual fatigue crack surfaces under plane strain conditions. It is shown that the size and density of individual contacts, or asperities, can be estimated from acoustic measurements. Furthermore, it is shown that this information is needed to calculate the static stress across a partially closed crack as well as the “effective” stress intensity range, which activates fatigue crack propagation.