A Numerical Scheme for Fast and High Accuracy Simulation of Motion-Induced Eddy Current Testing Signals

In this paper, an efficient numerical scheme and corresponding fast solver are proposed and implemented for rapid and high-accuracy numerical calculation of the motion-induced eddy current testing (MIECT) forward problems. First, inspired by the time-domain numerical formulation of the MIECT problem, a DFT-based numerical scheme in the frequency-domain was proposed through DFT of the transient excitation magnetic field signals at conductor surface caused by the moving permanent magnet of the MIECT probe. Second, a fast-forward simulator was implemented by further improving the existing Ar code for single-frequency ECT problem and adopting databases approach using the unflawed field information solved and stored a priori. As the key of the fast simulation of the MIECT signal perturbed by defects, a scheme to calculate the pickup signal perturbations was proposed and validated based on the reciprocity theorem. Finally, the validity of the numerical schemes and corresponding fast-forward solver was verified through comparing simulation results with experimental signal. Compared with the full analysis domain methods, the fast simulator can save computational burden up to 1000 times on the premise of not affecting the numerical precision, which enables its being adopted in the inverse analysis of MIECT signals for defect sizing.