LOI-Based Pulsed Eddy Current Evaluation of Hidden Material Degradation in Coated Nonmagnetic Conductors

摘要

Coated nonmagnetic conductors are subject to material degradation hidden under nonmetallic coating. It is formidable to evaluate the degradation degree and thickness of degradation region without removing the non-conductive coating. In light of this, in this paper the feasibility of pulsed eddy current (PEC) probes for nondestructive assessment of hidden material degradation in coated nonmagnetic conductors was investigated. The characteristics of lift-off intersection (LOI) of signals from PEC probes were utilized in a bid to cancel out the influence of coating thickness on signals. A fast inverse scheme based on LOI was proposed, along with the probe to implement simultaneous evaluation of the degradation degree and thickness. A series of experiments revealed that the proposed probe is high-efficiency and capable of assessing hidden material degradation without much loss of accuracy.