Simplified test comparison of two excitation modes in MFL internal inspections

In order to compare systematically the inspection accuracy of axial-excitation magnetic flux leakage (MFL) internal inspection and circumferential-excitation MFL internal inspection on defects of different angles, a simplified engineering comparison test was designed. In the test, a flat steel plate on which defects of different angles were made was used as the test sample, and a magnetic leakage detection prototype with flat structure was developed to simulate axial and circumferential excitation MFL internal inspection by changing the direction of the excitation. By virtue of the MFL detection prototype with flat plate structure, MFL inspection was performed to the defects on the flat plate based on axial excitation and circumferential excitation, and the MFL signals were acquired. The following test conclusions are reached by comparing the detection signals of the same defect acquired from axial-excitation MFL internal inspection and from circumferential-excitation MFL internal inspection. The circumferential-excitation MFL internal inspection results are more accurate if the defect is parallel to the axial direction or the included angle between the defect and the axial direction is equal or less than 30°, and the axial-excitation MFL internal inspection results are more accurate if the included angle between the defect and the axial direction is more than 30°. (11 Figures, 20 References)