Going deeper on magneto-optical Faraday effect analysis to detect fatigue crack with high-spatial resolution for non-destructive inspection

In this study, we introduce a high-resolution technique for defect detection that uses the magneto–optical (MO) Faraday effect. Our system combines a portable polarized microscope and an MO sensor for the high spatial observation of a magnetic domain structure. We accurately localized and characterized the fatigue defects through integrated image pre-processing and cross-power spectral density analysis. This approach enhances our analysis of the magnetic domain structure, increasing the spatial capabilities of the microscope to detect fatigue defects. We conducted experiments on fatigue cracks with defect depth angles of 0°, 30°, and 60°, analyzing their relationship through signal amplitude and the tendency of the signal shift with increasing defect angle. Our findings were validated using a tunnel magnetoresistance sensor. Future research will focus on the optimization of feature extraction complexity, considering the limited computational power available for portable non-destructive testing devices.