Magnetic flux leakage (MFL) testing is widely used to detect and estimate defect in ferromagnetic materials. The lift-off of sensors caused the weakening of the detected signal inevitably. Therefore, it is necessary to correct lift-off for the detected MFL signal. In this article, we analyze the approximate negative exponential relationship between the three components of MFL signal of the defect and the lift-off based on magnetic dipole analytical method and establish a simplified numerical calculation model of MFL signal based on the lift-off. A lift-off correction method is also proposed to revise the three components of the MFL signal at a suitable range of lift-off efficiently. In this method, an exponential function compensation is introduced and only the lift-off correction value is concerned. The validity of the correction method is verified by the 3-D MFL testing experiment for the ferromagnetic pipeline defects. The results demonstrate that the corrected MFL signals match the experimental signals well.

中文翻译：

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用于缺陷检测的漏磁信号三个分量的简化提离校正


漏磁 (MFL) 测试广泛用于检测和评估铁磁材料中的缺陷。传感器的升空不可避免地导致检测到的信号减弱。因此，有必要对检测到的MFL信号进行提离校正。本文基于磁偶极子解析方法分析了缺陷的MFL信号的三个分量与提离之间的近似负指数关系，并建立了基于提离的MFL信号的简化数值计算模型。还提出了一种提离校正方法，以在合适的提离范围内有效地修正 MFL 信号的三个分量。该方法引入了指数函数补偿并且仅关注提离校正值。通过铁磁管道缺陷3D MFL检测实验验证了修正方法的有效性。结果表明，校正后的 MFL 信号与实验信号吻合良好。