Scattering of ultrasonic waves by defective adhesion interfaces in submerged laminated plates

We present an analytical-numerical method to simulate time-harmonic ultrasonic scattering from nonhomogeneous adhesive defects in anisotropic elastic laminates. To that end, we combine the quasistatic approximation (QSA) with a very high-order (tens or hundreds of terms) regular perturbation series to allow modeling of nonuniform interfacial flaws. To evaluate each term in the perturbation series, we use a recursive algorithm based on the invariant imbedding method. It is applicable to solve wave propagation problems in arbitrarily anisotropic layered plates and it is stable for high frequencies. We demonstrate examples of convergence and divergence of the perturbation series, and validate the method against the exact solution of plane wave reflection from a layered plate immersed in water. We present a further example of scattering of a Gaussian beam by an inhomogeneous interfacial flaw in the layered plate. We discuss how results of our simulations can be used to indicate the frequencies and angles of incidence where scattering from potential defects is strongest. These parameters, presumably, offer the best potential for flaw characterization. (c) 2005 Acoustical Society of America.