Research on the Forward Solving Method of Defect Leakage Signal Based on the Non-Uniform Magnetic Charge Model

Abstract

Pipeline magnetic flux leakage inspection is widely used in the evaluation of material defect detection due to its advantages of having no coupling agent and easy implementation. The quantification of defect size is an important part of magnetic flux leakage testing. Defects of different geometrical dimensions produce signal waveforms with different characteristics after excitation. The key to achieving defect quantification is an accurate description of the relationship between the magnetic leakage signal and the size. In this paper, a calculation model for solving the defect leakage field based on the non-uniform magnetic charge distribution of magnetic dipoles is developed. Based on the traditional uniformly distributed magnetic charge model, the magnetic charge density distribution model is improved. Considering the variation of magnetic charge density with different depth positions, the triaxial signal characteristics of the defect are obtained by vector synthesis calculation. Simultaneous design of excitation pulling experiment. The leakage field distribution of rectangular defects with different geometries is analyzed. The experimental results show that the change in defect size will have an impact on the area of the defect leakage field distribution, and the larger the length and wider the width of the defect, the more sensitive the impact on the leakage field distribution. The solution model is consistent with the experimentally obtained leakage signal distribution law, and the model is a practical guide by which to improve the quality of defect evaluation.

Evaluation of Depth Size Based on Layered Magnetization by Double-Sided Scanning for Internal Defects

“…In the current research, the common electromagnetic nondestructive evaluation methods for defect size evaluation include eddy current testing (ECT) [ 4 , 5 , 6 , 7 ], pulsed eddy current testing (PECT) [ 8 , 9 , 10 , 11 , 12 ], and magnetic flux leakage (MFL) testing [ 13 , 14 , 15 ], alternating current field measurement (ACFM) [ 16 , 17 , 18 ]. MFL [ 19 , 20 , 21 , 22 , 23 ] was limited by wall thickness, while the signal for evaluating defects in thick-walled components is attenuated with increasing wall thickness, and some of them [ 24 , 25 , 26 , 27 , 28 , 29 , 30 ] were often affected by skin effects or magnetic shielding effects. Nowadays, some scholars [ 31 , 32 , 33 , 34 ] evaluated defects through signal characterization with algorithmic optimization.…”