Application of the Geometrical Theory of Diffraction to closed cracks
The purpose of this paper is to compare the scattering of ultrasound by means of different types of smooth planar cracks in elastic solids. The boundary conditions on the flaws are of a type that incorporates interfacial forces. A crack that is partly closed by a static background pressure can thus be modeled. The Geometrical Theory of Diffraction (GTD) is used to predict the pulse-echo response from the crack. Previously obtained diffraction and reflection coefficients for cracks with interfacial forces are reviewed and some numerical difficulties are discussed. The backscattered echo amplitude is numerically calculated and compared for some different crack types and crack shapes. The presence of interfacial forces, due to background pressure, significantly influences the scattering behavior of the cracks. For a background pressure of 250 MPa, the backscattered amplitude, using our model of the interfacial forces, is typically reduced by 5–20 dB.
Key wordsScattering GTD spring contact closed crack
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