Influence of planar cracks in plates on reflected and transmitted fields of Gaussian acoustic beams

The scattering of a Gaussian beam by a rectangular crack is studied by means of the radiation mode model. The orthogonal set of modes for a L/S/V structure is derived, and a general mode decomposition formula is developed. The influence of a crack on the reflected and transmitted fields of a bounded beam, incident at critical angles of the L/S/L- and the L/S/V structure, is studied and physical interpretations are given. From those interpretations, the starting point of the crack is deduced along with the length and distance to the surface. Effects on focused beams are considered as well.