A ray-theory approach is presented to analyze scattering of Rayleigh surface waves by a surface-breaking crack. The two-dimensional problem of normal incidence on an edge crack of depth d in an elastic half-space is discussed in detail. The basic diffraction mechanisms in the high-frequency range at the mouth and the edge of the crack are investigated one by one on the basis of elastodynamic ray theory. The results are then superimposed to yield simple expressions for the backscattered and forward-scattered Rayleigh surface waves and for the elastodynamic stress-intensity factors, in terms of reflection, transmission, and diffraction coefficients. These approximate results are compared with exact numerical results. Good agreement is observed for d/A > 1, where A is the wavelength of the incident surface wave. A simple formula for the inverse problem is presented, which relates the periodicity of the amplitude modulation in the high-frequency range directly to the depth d of the crack.
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