Abstract: In order to solve the problem that the angle of crack and magnetization direction was too small to identify in the pipeline magnetic flux leakage internal detection, the influence of crack angle on magnetic flux leakage detection signal and the characteristics of crack magnetic flux leakage signal under the condition of axial excitation of DC electromagnet were analyzed. Comsol finite element simulation software was used to simulate and analyze the crack defects of 0.2 mm in different angles of the inner wall of the pipeline. DC electromagnet axial excitation experimental platform was built, and EDM technology was used to process the specimens with different angles of crack to carry out the dragging experiment of the crack angle. Results show that the minimum detectable angle of crack and magnetization direction is 25°. The peak value of MFL signal decreases with the decrease of crack angle, larger the signal span, the greater the influence of noise signal. When the magnetization direction is perpendicular to the crack, the maximum span of MFL signal amplitude is the smallest, and when the magnetization direction is parallel to the crack, no MFL signal is generated.

Key words: Electromagnetic field, Crack angle, Axial field, Leakage field

摘要： 针对管道漏磁内检测中裂纹与磁化方向角度过小难以识别问题，分析了直流电磁铁轴向励磁条件下裂纹角度对漏磁检测信号的影响以及裂纹漏磁信号的特征。采用Comsol有限元仿真软件，对管道内壁不同角度0.2 mm裂纹缺陷进行了仿真分析；搭建了直流电磁铁轴向励磁实验平台，采用电火花技术加工不同角度裂纹试件，进行裂纹角度问题的拖拉实验。结果表明，裂纹与磁化方向最小可检测角度为25°；随着裂纹角度的减小，漏磁信号峰值逐渐减小，信号跨度越大，噪声信号影响越大；当磁化方向与裂纹垂直时，漏磁信号幅值最大跨度最小，磁化方向与裂纹平行时无漏磁信号产生。

关键词: 电磁励磁, 裂纹角度, 轴向励磁, 漏磁场