Li Yong, Ren Shuting, Yan Bei, Zainal Abidin Ilham Mukriz, Wang Yi
State Key Laboratory for Strength and Vibration of Mechanical Structures, Shaanxi Engineering Research Center of NDT and Structural Integrity Evaluation, Xi'an Jiaotong University, Xi'an 710049, China.
Leading Edge NDT Technology (LENDT) Group, Malaysian Nuclear Agency, Bangi 43000, Kajang, Selangor, Malaysia.
Sensors (Basel). 2017 Jul 31;17(8):1747. doi: 10.3390/s17081747.
A corrosive environment leaves in-service conductive structures prone to subsurface corrosion which poses a severe threat to the structural integrity. It is indispensable to detect and quantitatively evaluate subsurface corrosion via non-destructive evaluation techniques. Although the gradient-field pulsed eddy current technique (GPEC) has been found to be superior in the evaluation of corrosion in conductors, it suffers from a technical drawback resulting from the non-uniform field excited by the conventional pancake coil. In light of this, a new GPEC probe with uniform field excitation for the imaging of subsurface corrosion is proposed in this paper. The excited uniform field makes the GPEC signal correspond only to the field perturbation due to the presence of subsurface corrosion, which benefits the corrosion profiling and sizing. A 3D analytical model of GPEC is established to analyze the characteristics of the uniform field induced within a conductor. Following this, experiments regarding the imaging of subsurface corrosion via GPEC have been carried out. It has been found from the results that the proposed GPEC probe with uniform field excitation not only applies to the imaging of subsurface corrosion in conductive structures, but provides high-sensitivity imaging results regarding the corrosion profile and opening size.
腐蚀性环境会使服役中的导电结构易于发生亚表面腐蚀，这对结构完整性构成严重威胁。通过无损评估技术检测并定量评估亚表面腐蚀是必不可少的。尽管梯度场脉冲涡流技术（GPEC）已被发现在评估导体腐蚀方面具有优势，但它存在一个技术缺陷，即传统扁平线圈激发的场不均匀。鉴于此，本文提出了一种用于亚表面腐蚀成像的具有均匀场激发的新型GPEC探头。激发的均匀场使GPEC信号仅对应于由于亚表面腐蚀的存在而引起的场扰动，这有利于腐蚀轮廓分析和尺寸测量。建立了GPEC的三维分析模型，以分析导体内感应的均匀场的特性。在此之后，进行了通过GPEC对亚表面腐蚀成像的实验。从结果中发现，所提出的具有均匀场激发的GPEC探头不仅适用于导电结构中亚表面腐蚀的成像，而且提供了关于腐蚀轮廓和开口尺寸的高灵敏度成像结果。
