Xu Zhiyuan, Wang Xiang, Deng Yiming
School of Mechanical Engineering, Xiangtan University, Xiangtan, Hunan 411105, China.
Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48824, USA.
Sensors (Basel). 2020 Apr 20;20(8):2345. doi: 10.3390/s20082345.
This paper presents a rotating focused field eddy-current (EC) sensing technique, which leverages the advantages of magnetic field focusing and rotating magnetic field, for arbitrary orientation defects detection. The sensor consists of four identical excitation coils orthogonally arranged in an upside-down pyramid configuration and a giant magneto-resistive (GMR) detection element. The four coils are connected to form two figure-8-shaped focusing sub-probes, which are fed by two identical harmonic currents with 90 degrees phase difference. A finite element model-based study of arbitrary orientation defects detection was performed to understand the probe operational characteristics and optimize its design parameters. Probe prototyping and experimental validation were also carried out on a carbon steel plate specimen with four prefabricated surface-breaking defects. In-situ spot inspection with the probe rotating above the defect and a manual line-scan inspection were both conducted. Results showed that the probe has the capability of detecting defects with any orientations while maintaining the same sensitivity and the defect depth can be quantitatively evaluated by using the signal amplitude. Compared with the existing rotating field probes, the presented probe does not require additional excitation adjustment or data fusion. Meanwhile, due to its focusing effect, it can generate a strong rotating magnetic field at the defect location with a weak background noise, thus yielding superior signal-to-noise ratio.
本文提出了一种旋转聚焦场涡流（EC）传感技术，该技术利用磁场聚焦和旋转磁场的优势，用于任意取向缺陷检测。该传感器由四个以倒金字塔配置正交排列的相同励磁线圈和一个巨磁阻（GMR）检测元件组成。四个线圈连接形成两个8字形聚焦子探头，由两个具有90度相位差的相同谐波电流馈电。进行了基于有限元模型的任意取向缺陷检测研究，以了解探头的工作特性并优化其设计参数。还在具有四个预制表面缺陷的碳钢平板试样上进行了探头原型制作和实验验证。在缺陷上方旋转探头进行现场点检测和手动线扫描检测。结果表明，该探头具有检测任意取向缺陷的能力，同时保持相同的灵敏度，并且可以通过信号幅度定量评估缺陷深度。与现有的旋转场探头相比，所提出的探头不需要额外的励磁调整或数据融合。同时，由于其聚焦效应，它可以在缺陷位置产生强旋转磁场，背景噪声较弱，从而产生优异的信噪比。
