The efficacy of ultrasonic methods to detect and characterize a crack depends on topographical features of the crack faces, the presence of inhomogeneities in the crack's environment, and the mechanical properties in the near-crack region. In this paper, the effects on the scattered ultrasonic field of various features of fatigue and stress corrosion cracks such as partial crack closure, the presence of microcracks and microvoids, and near-tip zones of different mechanical properties have been investigated. A representation integral for the scattered field has been used to formulate the ultrasonic scattering problem. Numerical results have been obtained for some canonical configurations. For the configurations examined in this paper, crack closure has the most significant effect on far-field scattering.
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