Localization of a Crack in Moving Cylindrical Ferromagnetic Rods by Measuring the Fourier Coefficients of the Leakage Magnetic Flux

This article presents a novel leakage magnetic flux (LMF) method to estimate crack positions in moving cylindrical ferromagnetic rods. The crack positions are estimated by the circumferential first-order Fourier coefficients of the LMF by utilizing the dc excitation and modeling the moving crack as a magnetic dipole. The Fourier coefficients are directly measured by using only two coils. In addition, numerical experiments were conducted to evaluate the effect of motion-induced eddy current (MIEC). The demonstration of locating hole-shaped cracks in moving S45C cylindrical rods was performed by using the proposed method.