Eddy Current Induced by Pipe Rotation in MFL Testing and Its Influence on Testing Signal

摘要

In order to improve the testing efficiency in magnetic flux leakage testing of steel pipes, the rotational speed of pipes should be increased, which causes eddy current effect in the testing. The distribution of motional eddy current and its influence on the magnetization status of pipes is analyzed. Then, finite element simulation is carried out to calculate the eddy current and magnetic field inside the steel pipe. Furthermore, the testing signals for both external and internal longitudinal defects are extracted. The results show that: in the regions where the pipe is approaching the pole shoes, the external defect signal decreases with the increase of rotational speed and the internal defect signal only changes a little; In the regions where the pipe is leaving the pole shoes, the external defect signal increases with the increase of rotational speed and the internal defect signal decreases with the increase of rotational speed.