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http://dx.doi.org/10.4283/JKMS.2004.14.6.207

Lift-Off Invariance Transformations for Electromagnetic Eddy Current Nondestructive Evaluation Signals  

Kim, Dae-Won (단국대학교 공학대학 전자컴퓨터학부 멀티미디어학전공)
Publication Information
Journal of the Korean Magnetics Society / v.14, no.6, 2004 , pp. 207-212 More about this Journal
Abstract
Eddy current (EC) testing methods are widely used in a variety of applications including the inspection of steam generator tubes in nuclear power plants, aircraft parts and airframes. A key factor that affects the EC signal is lift-off which means the physical distance between a sensor and a specimen in the testing. In practice, it is difficult to keep track of the actual value of the lift -off during a specific experiment, simulation or testing in the field, which is essential for accurate interpretation of the signal to be used in the following steps. Hence it is necessary to have a scheme to render the EC signal invariant to the effects of lift-off in spite of the changes in the real world. This paper describes a new method for compensating EC signals for variations in lift-off by acquiring an invariance feature using a homomorphic operator and neural network techniques. The signals from various lift-offs are transformed to obtain a zero lift-off equivalent signal that can be subsequently used for defect characterization in the next step.
Keywords
Eddy current; Invariance Transformation; Lift-off; Nondestructive Evaluation;
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