Magnetic Flux Leakage Testing for Steel Plate Using Pot-Shaped Excitation Structure

Abstract

U-shaped excitation structures are widely used to magnetize steel plates in magnetic flux leakage (MFL) testing. However, the edge effect leads to the difficulty of further increasing the magnetization near the defect as well as the leakage magnetic field (LMF). Therefore, this article proposes an MFL testing device with a pot-shaped excitation structure to concentrate on the main magnetic flux in the steel plate between the two magnetic poles for improving the LMF. First, the simulated comparison of the conventional U-shaped and the proposed pot-shaped structures is presented in this article. Then, a sensor array is applied to investigate the measured MFL signal components and the C-scan images of the pot-shaped structure. Finally, the experiments are conducted to verify the effectiveness of the simulations and investigate the effect of the relative position of the sensor. The results show that the peak-to-peak value of the MFL signal can increase to 1.93 times after using the pot-shaped structure. Besides, its signal is not affected by the steel plate width and remains the ability to characterize defect sizes and profiles.