Motion induced eddy current based testing method for the detection of circumferential defects under circumferential magnetization

Magnetic flux leakage (MFL) testing is widely applied in the online detection of steel pipes. Different magnetizing directions are required for the detection of defects in different directions. As the speed of online MFL testing increases, the motion induced eddy current (MIEC) effect becomes significant, and the direction of the MIEC is perpendicular to defects in the same direction as the magnetization. Therefore, the magnetic field signal generated by the MIEC perturbation is analyzed by simulation and compared with MFL signal. It is found that the amplitude of the magnetic field signal generated by the MIEC perturbation increases with the rise of the rotational speed and magnetization. In high rotational speed and strong magnetization, the amplitude of the magnetic field signal caused by MIEC perturbation is greater relative to the amplitude of the MFL signal, providing a possibility for detecting defects that are parallel to the direction of magnetization.