Segmental Resonator Loaded Transmission Line for Robust Crack Detection

Crack defects widely exist in metallic structures due to cycling stress, and the uncertainty of their locations brings challenges in detection. This paper proposes a sensor design approach to improve the coverage and consistency of crack detection. By serially loading the split ring resonator under the transmission line in a meander format, the coupling effect between the resonant units is weakened. A cap design is carried out at the gap of the split ring resonator. By this way, four sensing regions form to a near length of λ / 2. The crack depth detection sensitivity of each region is -14MHz/mm2. The proposed sensor overcomes the limited coverage of single resonator and the sensitivity limitation varying with position.