Fatigue Crack Inspection Using Microwave Resonator Probe

Fatigue cracks are among the most commonly occurring anomalies in metallic structures. Detection and characterization of cracks is of utmost significance to prevent complete failure of structures. The detection of a fatigue crack using microwave nondestructive testing methods is complicated by the fact that the indication of such a crack is very small compared to the environmental disturbances (e.g., surface irregularities, variations in the lift-off, etc.). Furthermore, orientation/location of the crack is typically unknown a priori. In this paper, an enhanced microwave resonator probe is introduced for the detection of fatigue cracks in metals. The performance of the probe which operates at 800 MHz is demonstrated on a real fatigue crack with width measured to be less than 3 μm near its tip at a lift-off of 1mm, The performance is also compared to a conventional Ka-band rectangular aperture probe, which was unable to detect the crack.