Detection of surface cracks of arbitrary shape in metals using an open-ended waveguide probe

Abstract

A new formulation is presented to model the problem of an open-ended waveguide probe radiating into a conducting metal with a surface-breaking crack of arbitrary shape. In this formulation, the crack is first modeled by an appropriate number of short rectangular waveguides. The mode-matching technique is then used to calculate the scattering matrix of the new segmented waveguide structure. The probe reflection coefficient of the dominant mode, TE10, is finally calculated for various positions of the crack in order to predict the probe output signal. Results obtained for a semi-circular crack will be presented, demonstrating the potential of the new formulation for handling real fatigue cracks.