A Flexible Sensor Tag for Surface Crack Detection of Curved Film-Coated Metals

A novel sensor tag based on spit ring resonator (SRR) for detecting cracks on curved metal surfaces is presented in this paper. This tag is flexible and can be easily covered on the surface of curved metal structure. The SRR shape is etched on the tag, which is excited by the waveguide to make it resonate. Accurate crack detection can be achieved based on the resonance frequency shift caused by the crack. Due to the strong field enhancement effect during SRR resonance, the tag is highly sensitive in detecting metal cracks. When the radius of the curved film-coated metal is 40mm, there will be a resonant frequency shift greater than 260MHz when detecting sub-millimeter cracks of different sizes. And a resonance frequency shift of at least 100MHz is still exhibit when a 10 $\mu {\mathrm{ m}}$ microcrack is detected. This tag is expected to provide a new idea for high-precision surface crack detection of curved metals.