Interaction of Rectangular Open-Ended Waveguides With Surface Tilted Long Cracks in Metals

This paper presents a modeling technique for output-signal prediction of a waveguide probe when scanning a tilted long crack. The modeling technique establishes a cavity by placing a hypothetical conductive plane within the waveguide at some distance away from the probe-crack mouth. The position of the plane is iteratively changed until the appropriate resonance frequency of the cavity equals the operating frequency. In this case, the plane lies at one of the dominant-mode standing-wave nulls inside the waveguide from which the reflection coefficient, and hence, the probe output signal are determined. The main feature of the model is its ability to solve a three-dimensional problem in a two-dimensional framework, thus reducing the degree of complexity and computation time. Several simulation results are presented to evaluate the accuracy of the model at two operating frequencies in the X and K bands. The results are compared with the experimental results and those obtained using a commercial finite-element code, demonstrating the accuracy of the modeling technique