Study of Lift-Off Invariance for Pulsed Eddy-Current Signals

被引：119

作者：

Tian, Gui Yun ^{[1
]}

Li, Yong ^{[1
]}

Mandache, Catalin ^{[2
]}

机构：

[1] Newcastle Univ, Sch Elect Elect & Comp Engn, Newcastle Upon Tyne NE1 7RU, Tyne & Wear, England

[2] Natl Res Council Canada, Inst Aerosp Res, Ottawa, ON K1A 0R6, Canada

来源：

IEEE TRANSACTIONS ON MAGNETICS | 2009年 / 45卷 / 01期

基金：

英国工程与自然科学研究理事会;

关键词：

Inverse process; lift-off; lift-off compensation; lift-off invariance; normalization; pulsed eddy current; CURRENT NDT; DEFECT CLASSIFICATION; SENSORS;

D O I：

10.1109/TMAG.2008.2006246

中图分类号：

TM [电工技术]; TN [电子技术、通信技术];

学科分类号：

0808 ; 0809 ;

摘要：

Lift-off invariance (LOI) is getting much attention from researchers in the field of electromagnetic nondestructive evaluation (ENDE) because, at the LOI point, eddy-current signals for different lift-offs intersect and the signal amplitude is independent of the lift-off variance. We discuss our ongoing research into LOI, starting from an overview of the state-of-the art of pulsed eddy-current testing (PEC) systems and their use in the elimination of the lift-off effect. We have investigated LOI characteristics with respect to variation in the configuration of the PEC probe in a theoretical study, implemented by extended truncated region eigenfunction expansion (ETREE) modeling. We found that: 1) the LOI occurs when the first-order time derivative of the magnetic field signals are acquired from Hall sensors; 2) an LOI range instead of a single LOI point, when multiple lift-offs are introduced through both experimental and theoretical studies. The LOI range varies with the Hall sensor position in the probe assembly and the conductivity of the samples under inspection, which are important parameters for the design and development of PEC systems. Based on this understanding, we investigated new approaches using theoretical computation and multiple lift-off, or magnetic sensor arrays, for conductivity and lift-off estimation. Our study can be extended for design and development of multipurpose eddy-current sensor systems for surface form measurement and defect detection.

引用

页码：184 / 191

页数：8

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