Design and fabrication of a high-Q near-field probe for subsurface crack detection

Non-destructive detection and evaluation of invisible cracks in metal structures is an important matter in several critical environments including ground transportation, air transportation and power plants. In this paper, a high-Q near-field Microwave probe is designed and fabricated using defected ground structures for surface and subsurface crack detection in metal structures. For this purpose, several near-field probes with different DGSs are designed and probe with the highest quality factor is selected for subsurface detection. Experimental results show that the proposed probe is able accurately detect invisible crack of a size 1mm with at least 20dB magnitude and more than 300 degrees phase contrast. It has also been demonstrated that the proposed device can efficiently used for detection and imaging of small failure and crack in dielectric and metallic structures. Also, it is noted that if the probe dimensions scale down, spatial resolution for crack detection of size in micro and nanometer is achieved at millimeter waves.