Application of surface impedance approach to ultrasonic wave propagation in layered anisotropic media

Abstract

Matrix methods have been extensively used for wave propagation problems in layered media. Direct application of these methods using partial waves or transfer matrix formulation result in numerical problems known as exponential dichotomy. In this paper, we use the concept of surface impedance tensor to tackle this problem. Given the surface impedance tensor along an initial surface, a recursive algorithm is used to calculate the surface impedance tensor for the other layers. The methodology inherently prevents exponential dichotomy. We present applications of the surface impedance approach to practical problems. As examples, we consider the anisotropy of SAW velocity for different electrical boundary conditions, plane wave reflection from immersed layered structures with general anisotropy, and internal field distributions for predicting defect detection sensitivity.