Output Signal Prediction of an Open-Ended Coaxial Probe When Scanning Arbitrary-Shape Surface Cracks in Metals

A subdomain method of moment formulation is proposed to model the problem of an open-ended coaxial probe radiating into a metal with a surface-breaking crack of arbitrary depth profile. The proposed formulation is capable of treating effectively the unknown magnetic current over the arbitrary-shape common aperture. By using the dyadic Green´s function, it is sufficient to discretize the common aperture surface rather than the entire structure, which results in a sharp decrease in the number of unknowns. This feature will remarkably improve the computation time, resulting in a fast prediction of probe output signal. Results are given for cracks with rectangular, semicircular, and semielliptical shapes. The accuracy of the model will be demonstrated by comparing the simulation results with those obtained using a commercial finite integration technique and measurement results.