Calculation and Measurement of Scattering Coefficients for Surface-Breaking Cracks Sonified by a Focused Array

Abstract

A simulation of a focused beam of surface wave motion generated by a line array of surface wave transducers is used to calculate the field scattered back from a surface-breaking crack. The backscattered field is expressed in terms of a scattering coefficient, which is derived from the reciprocal identity for elastodynamic states, and which is calculated numerically by using the Kirchhoff approximation. In an earlier work the validity of the focused beam simulation has been verified. In this paper, the theoretical results for the backscattered field are compared with measurements for two crack sizes, one of which is used for calibration.