School of Automation Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China.
Center for Information Geoscience, University of Electronic Science and Technology of China, Chengdu 611731, China.
Sensors (Basel). 2018 Aug 23;18(9):2769. doi: 10.3390/s18092769.
Remote Field Eddy Current Testing (RFECT) has broad applications in ferromagnetic pipe testing due to the same testing sensitivity to inner and outer wall defects. However, how to quantify wall thickness in the RFECT of pipes is still a big problem. According to researchers' studies, a linear relationship exists between the wall thickness, permeability and conductivity of a pipe and the phase of the RFECT signal. Aiming to quantify wall thickness by using this linear function, it is necessary to further study the effects of pipe permeability and conductivity on the phase of the RFECT signal. When the product value of the permeability and the conductivity of a pipe remains constant, the univariate analysis and Finite Element Analysis (FEA) are employed to analyze the variations among the phase of the RFECT signal caused by different couples of permeability and conductivity. These variations are calibrated by using a nonlinear fitting method. Moreover, Multi-Frequency Eddy Current Testing (MFECT) is applied to inverse the permeability and conductivity of a pipe to compensate for the quantification analysis of wall thickness. The methods proposed in this paper are validated by analyzing the simulation signals and can improve the practicality of RFECT of ferromagnetic pipes.
远场涡流检测（RFECT）由于对内外壁缺陷具有相同的检测灵敏度，因此在铁磁管道检测中具有广泛的应用。然而，如何在管道的 RFECT 中定量壁厚仍然是一个大问题。根据研究人员的研究，管道的壁厚、磁导率和电导率与 RFECT 信号的相位之间存在线性关系。为了利用这个线性函数来定量壁厚，有必要进一步研究管道磁导率和电导率对 RFECT 信号相位的影响。当管道的磁导率和电导率的乘积保持不变时，采用单变量分析和有限元分析（FEA）来分析由不同的磁导率和电导率对 RFECT 信号相位引起的变化。这些变化通过非线性拟合方法进行校准。此外，多频涡流检测（MFECT）被应用于反演管道的磁导率和电导率，以补偿壁厚的定量分析。本文提出的方法通过对模拟信号的分析进行了验证，提高了铁磁管道 RFECT 的实用性。
