Affiliations: [a] School of Mechanical Science and Engineering, Huazhong
University of Science and Technology, Wuhan, Hubei, China | Université Laval, Canada | Tohoku University, Japan
Correspondence:
[*]
Corresponding author: Jianbo Wu, School of Mechanical Science
and Engineering, Huazhong University of Science and Technology, Wuhan 430074,
Hubei, China. Tel.: +86 139 7104 0932; E-mail: meishanwujianbo@163.com
Abstract: According to the Lenz's Law, eddy-current essentially exists in MFL
(magnetic flux leakage) testing due to the relative movement between steel pipe
and excitation coil, apparently affecting the MFL signals with the testing
speed rising. Hence, the constitutive equation of eddy-current in the steel
pipe was established by using Lenz's Law and it was found that: eddy-current in
the arriving zone has the different direction from excitation current,
resulting in the reduction of magnetization intensity; but they have the same
direction in the leaving zone, where the magnetization intensity is enhanced;
and there is few eddy-current formed in the center; besides, the eddy-current
density has direct proportion to the testing speed. Further, the effect on the
MFL signal was investigated and it was shown that not only the magnitude but
also the features are altered. Finally, a confirmation for the aforementioned
analysis was conducted by numerical simulations.
