Numerical and Experimental Analysis of Defect Detection in Jointed Electromagnetic Waveguides

Electromagnetic waves in the microwave and millimeter-wave frequency range are used in non-destructive testing (NDT) and structural health monitoring (SIMI) applications to detect material defects such as delaminations, cracks or inclusions. This work presents a sensing concept called jointed electromagnetic waveguide, in which the waveguide forms a union with the structure to be inspected. Exploiting ultra-wideband signals a surface defect in the area under the waveguide can be detected and accurately localized. This paper presents numerical and experimental results of the jointed electromagnetic waveguide technology with a focus on detecting through holes and cracks with different orientation. It was found that the numerical model qualitatively replicates the experimental S-parameter measurements for holes of different diameters. A parametric numerical study indicates that the crack parameters such as its orientation and width has a significant influence on the interaction of the incident wave with the structural defect.