基于低频电磁的铁磁管道内壁缺陷重构方法

利用低频电磁的方法对铁磁管道内壁缺陷进行检测及轮廓重构是当前的一个热点问题。然而，低频电磁方法检测到的漏磁信号是周期性变化的，不便于缺陷信息的提取，并且被检测管道的长度、管径和原始壁厚的不同会严重干扰检测结果。因此，本文首先建立了低频磁场下管道内壁缺陷的二维有限元检测模型。其次通过计算漏磁信号与线圈电流比值，消除了漏磁信号的周期性变化给检测带来的不便。然后通过对的预处理，有效减少管道长度、管径和原始壁厚的不同对缺陷轮廓重构结果的影响。最后，基于高斯过程回归算法建立预处理信号与缺陷轮廓的回归模型，实现了缺陷轮廓重构。仿真结果中，针对长度、管径和原始壁厚各异的铁磁管道，所重构轮廓的均方根误差在0.17mm左右，表明该方法能够准确的重构出内壁缺陷轮廓。

Reconstruction method of inwall defects of ferromagnetic pipe based on low frequency electromagnet

Defect detection on inwall of ferromagnetic pipes through low frequency electromagnetic method has become a research hotspot. However, periodic variation of magnetic flux leakage signal brings inconvenience to extraction of defect information. In addition, dependences between magnetic flux leakage signal and the pipe parameters such as length, diameter and initial thickness severely disturb the detection. To solve the problems, in this paper, we firstly establish a two-dimensional finite element detection model of irregular defects on inwall of the ferromagnetic pipes. Subsequently, the impact of periodic variation of magnetic flux leakage signal on extraction of defect information is eliminated by calculating the ratio of magnetic flux leakage signal to coil current. After that, the impact of dependences between magnetic flux leakage signal and the pipe parameters is greatly reduced through preprocessing of Finally, the defect profile is successfully reconstructed using the regression model between defect profile and preprocessed trained by Gaussian process regression algorithm. Based on the above mentioned method, simulation has been performed, and the results indicate that the RMSEs of reconstructed profiles are all around 0.17mm, which verify that the proposed method can accurately reconstruct profiles of the defects on inwall of ferromagnetic pipes.