Measurement of the scattering of a Lamb wave by a through hole in a plate

Flexural waves propagating in an aluminum plate containing a circular hole are studied. In the experiments the first antisymmetric Lamb wave mode A(0) is excited selectively by a piezoelectric transducer. The scattered field around a circular cavity is measured pointwise using a heterodyne laser interferometer. The measurements are compared with theoretical calculations. Different approximate analytical approaches, employing Kirchhoff and Mindlin types of plate theories to describe the scattered field, are used. Good agreement between the experimental data and the analytical solutions is found within the ranges of validity of the different models. Introduction of a small imperfection, like a notch, at the boundary of the cavity changes the measured scattered field significantly. The approach allows a fast measurement of large surfaces and might be useful for nondestructive testing purposes, e.g., the detection of cracks at fastener holes in airplane fuselage. (C) 2002 Acoustical Society of America.