Research on the magnetic flux leakage field distribution characteristics of defect in low-frequency electromagnetic detection technique

[摘要] This work aimed to investigate the distribution characteristics of the low-frequency magnetic flux leakage (LF-MFL) field of defect on oil and gas pipelines in low-frequency electromagnetic detection technique (LFET). Taking four types of crack defects (rectangular, semicircular, trapezoidal, and V-shaped grooves) with equal lengths, widths and different bottom shapes into consideration, the specific mathematical model of the LF-MFL field was inferred and established on the basis of magnetic dipole theory. Experimental results demonstrated that the variation values of the tangential and normal component upper-lower envelope difference curves were linearly positively correlated with the defect cross-sectional area along the detection direction, which was strictly independent of bottom shape and excitation conditions (amplitude, frequency and lift-off).

[学科分类] 电子、光学、磁材料

[关键词] low-frequency magnetic flux leakage (LF-MFL);lowfrequency electromagnetic detection technique (LFET);magnetic dipole;cross-sectional area