Beam Parametrization of Localized Weak Debonding in a Layered Aluminum Plate

Abstract

Obliquely incident (predominantly P-wave) beam inputs from an ultrasonic transducer into a layered bounded composite elastic plate are suitable for detection of weak debonds because they generate on the bond lines the tangential shear to which this kind of flaw responds. In previous studies, the beam-flaw interaction and scattering mechanisms were explored by expressing the fields in both the unflawed and flawed environments in terms of the set of P-SV coupled modes capable of propagating in the plate [1–5]. As may be anticipated, the reference data generated in this manner exhibited beam-like features of the fields in observational domains characterized by only a few P-SV coupled beam reflections between the outer boundaries of the perfectly bonded plate, thereby indicating that the normal modes do not parametrize the process in terms of the “observables” in the data. The problem is therefore re-parametrized here by direct beam tracking. As before [1,2], our model is two-dimensional and comprises a two-layer aluminum plate in vacuum, with a weak debond region modeled by a quasi-Gaussian pliability profile.