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：

---

用于缺陷检测的磁通量泄漏信号的三个分量的简化提离校正

磁通量泄漏（MFL）测试被广泛用于检测和评估铁磁材料中的缺陷。传感器的抬起不可避免地导致检测信号的减弱。因此，有必要为检测到的MFL信号校正提离。本文基于磁偶极子分析方法，分析了缺陷的MFL信号的三个分量与剥离之间的近似负指数关系，建立了基于剥离的MFL信号简化数值计算模型。还提出了提离校正方法，以在合适的提离范围内有效地修正MFL信号的三个分量。在该方法中，引入了指数函数补偿，并且仅涉及提升修正值。通过3-D MFL测试实验对铁磁管道缺陷的校正方法的有效性。结果表明，校正后的MFL信号与实验信号很好地匹配。