Blocking of a Rayleigh wave by a subsurface crack

Abstract

By now, diffraction of Rayleigh waves (RWs) by surface and subsurface obstacles has been studied relatively well. Flaw detection using reflected and transmitted signals yields information on zones of exfoliation of film structures and nanocoatings, on inceptive defects (fractures) in structural elements, and on surface corrosion of pipelines. Sharp screening of surface waves at certain frequencies is used in acoustoelectronics for producing frequency filters. In geophysics, surface waves provide information on the presence and properties of seismic brakes. When an RW runs on a crack that does not even reach the surface, partial reflection of the wave with a transformation of a fraction of its energy into bulk waves is also observed. One of the most thorough theoretical studies of dependences of the transmission κ+, reflection κ–, and surface-to-bulk conversion κv coefficients for the energy of a plane RW on the size, tilt, and depth of a strip crack was performed by van der Hijden and Neerhoff [1]. In particular, they have shown that, at a certain ratio of depth d of a horizontal crack to the crack half-width a, it is possible to almost completely screen a surface wave. The minimum value of the transmittance κ+ = 0.0036 was obtained at ω = 3, d/a = 0.46,