In conventional magnetic flux leakage (MFL) detection, a lift-off layer based on air or non-ferromagnetic wear-resistant material is employed to prevent magnetic sensors from wearing. However, the increase of the lift-off will lower the detection sensitivity and reduce the MFL signal amplitude. To address the issue, theoretical analysis was used to investigate the effect of the ferromagnetic lift-off layer on MFL detection in this study. Then, we put forward a new MFL detection method based on the ferromagnetic lift-off layer. A through groove is machined in the ferromagnetic lift-off layer, which creates an air gap below the sensor. The leakage magnetic field (LMF) generated by the through groove increases the local magnetization intensity around the crack on the sample, while the LMF generated by the crack increases the magnetization intensity surrounding the through groove of the lift-off layer. As a result, the magnetic sensor above the through groove detects a greater MFL signal. In addition, the effect of applied magnetization intensity, groove width, and lift-off layer thickness on the detection signal were explored by experiments. The practicality of the proposed method of detecting different size cracks of nearside and farside were studied. In summary, experiments show that the ferromagnetic steel sheet with a through groove strengthens the MFL signal of the nearside and farside cracks.

在传统的漏磁检测（MFL）中，采用基于空气或非铁磁性耐磨材料的剥离层来防止磁传感器磨损。但是，提离的增加会降低检测灵敏度并降低 MFL 信号幅度。为了解决这个问题，本研究使用理论分析来研究铁磁剥离层对 MFL 检测的影响。然后，我们提出了一种新的基于铁磁剥离层的 MFL 检测方法。在铁磁剥离层中加工出通槽，在传感器下方形成气隙。通槽产生的漏磁场（LMF）增加了样品裂纹​​周围的局部磁化强度，而裂纹产生的LMF增加了剥离层通槽周围的磁化强度。因此，通槽上方的磁传感器检测到更大的 MFL 信号。此外，通过实验探索了外加磁化强度、凹槽宽度和剥离层厚度对检测信号的影响。研究了所提出的检测近侧和远侧不同尺寸裂纹的方法的实用性。总之，实验表明，带有通槽的铁磁钢板增强了近侧和远侧裂纹的 MFL 信号。通过实验探索检测信号上的剥离层厚度。研究了所提出的检测近侧和远侧不同尺寸裂纹的方法的实用性。总之，实验表明，带有通槽的铁磁钢板增强了近侧和远侧裂纹的 MFL 信号。通过实验探索检测信号上的剥离层厚度。研究了所提出的检测近侧和远侧不同尺寸裂纹的方法的实用性。总之，实验表明，带有通槽的铁磁钢板增强了近侧和远侧裂纹的 MFL 信号。