Development and optimisation of array probe and instrument for motion-induced eddy current testing

Motion-induced eddy current testing (MIECT) is a new electromagnetic non-destructive testing (NDT) technique with significant application potential in the inspection of engineering structures with relative motion. However, the current MIECT probe configurations were not optimised systematically, which constrains the broader practical application of MIECT. In this paper, a comprehensive methodology for the design and performance evaluation of MIECT probes is proposed, and high-performance probes were developed accordingly based on numerical analyses and experimental validation. Firstly, a numerical method is proposed to analyze signal contributions in ferromagnetic materials , confirming magnetic current as the dominant factor. Second, four novel probe configurations, i.e. double permanent magnet (PM) probe, double-PM differential probe, drag probe and the low-lift probe were designed based on the distinct physical effects. A comprehensive comparison of the signal-to-noise ratios (SNR) obtained via numerically reveals that the double-PM differential probe configuration delivers the best performance under both vertical and parallel crack orientations. Finally, a 16-channel MIECT instrument together with a high-speed experimental platform is developed and validated. The effectiveness of the proposed design methodology and the developed array MIECT system are verified experimentally.