Enhanced Crack Detection Using a Shielded Magnetic Probe With Tmr Sensors for Mfl and Eddy Current Techniques

This study investigates the effectiveness of a magnetic probe with and without shielding for crack detection in steel structures using Magnetic Flux Leakage (MFL) and Eddy Current (EC) techniques. A magnetic probe with two high-sensitivity TMR ALT025 sensors (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$2.5 ~\text{mm} \times 2.5 ~\text{mm}$</tex>) was developed and enclosed in a mild steel 1018 magnetic shield (12 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{mm} \times 9 ~\text{mm}$</tex>). The probe was integrated with 12 excitation coils (2.5 mm in diameter) and connected to a function generator, a current amplifier, a DAQ card, and a PC for data acquisition. The setup was mounted on an XY-stage controlled by LabVIEW for precise movement. Raw signal data were collected for both shielded and non-shielded configurations, and peak-to-peak values were calculated to compare real and imaginary components. Gradient analysis and percentage difference calculations further evaluated the shielding effect. The results indicate that the magnetic shield significantly influences the signal response, reducing background interference and enhancing sensitivity. The imaginary component exhibited a more pronounced difference between shielded and non-shielded conditions, highlighting the shielding effect on reactive magnetic field behavior. This study demonstrates that magnetic shielding improves the performance of TMR-based probes for crack detection by minimizing external disturbances and optimizing signal quality. The findings support the use of shielded probes for enhanced accuracy in non-destructive testing applications, with potential for further optimization in real-world structural assessments.