Study of Rotating Magnet Array-Based Motion-Induced Eddy Current Thermography

To achieve high-speed scanning of defect detection, this paper proposes a motion-induced eddy current (MIEC) thermography method, which utilizes the relative movement between permanent magnet array and the inspected object to induce the eddy current. Specifically, a set of circumferentially arranged permanent magnets rotating in a steel pipe is used to implement the proposed method. Numerical simulation and experimental studies are conducted to investigate the MIEC and thermal distribution influenced by speed, crack orientation, and lift-off effects. The results show that thermal contrast of the crack rises with its orientation to MIEC flowing path changing from parallel to perpendicular; thermal contrast decreases sharply with the lift-off distance of the magnet array increasing. One merit of the proposed MIEC thermography is that MIEC intensity (thermal contrast) increases with scanning speed and benefits the defect detection.