Highly Sensitive Nondestructive Tunneling Magneto Resistive Imaging: Simulation and Experimental Validation

Abstract

With the increased use of high-performance thin steels, detecting internal or external micro defects in a manufacturing process has become critical for the steel manufacturing process's cost and quality management. For detecting defects, magnetic-based nondestructive testing (NDT) methods have been researched widely due to their simplicity, ease of use, and contactless nature. However, magnetic-based approaches suffer from low sensitivity, thus limiting their use. Here, we present a highly sensitive tunneling magnetoresistive (TMR) imaging system to detect sub-surface defects in thin steel samples. Artificially created holes in the steel plates were magnetically imaged by measuring magnetic flux leakage (MFL). The experimental results were compared against the simulated results to confirm the visibility of the holes. We also confirmed the successful visualization of the sub-surface defects in the steel plates formed during the real manufacturing processes. Thus, based on these results, we believe the TMR method holds great potential as an NDT technique for steel manufacture management.