Preprint Article Version 2 Preserved in Portico This version is not peer-reviewed

Lift-off Invariant Inductance of Steels in Multi-Frequency Eddy-Current Testing

Version 1 : Received: 12 April 2021 / Approved: 14 April 2021 / Online: 14 April 2021 (14:24:43 CEST)
Version 2 : Received: 20 April 2021 / Approved: 22 April 2021 / Online: 22 April 2021 (09:16:48 CEST)

How to cite: Lu, M.; Meng, X.; Huang, R.; Chen, L.; Peyton, A.; Yin, W. Lift-off Invariant Inductance of Steels in Multi-Frequency Eddy-Current Testing. Preprints 2021, 2021040387 (doi: 10.20944/preprints202104.0387.v2). Lu, M.; Meng, X.; Huang, R.; Chen, L.; Peyton, A.; Yin, W. Lift-off Invariant Inductance of Steels in Multi-Frequency Eddy-Current Testing. Preprints 2021, 2021040387 (doi: 10.20944/preprints202104.0387.v2).

Abstract

Eddy current testing can be used to interrogate steels but it is hampered by the lift-off distance of the sensor. Previously, the lift-off point of intersection (LOI) feature has been found for the pulsed eddy current (PEC) testing. In this paper, a lift-off invariant inductance (LII) feature is proposed for the multi-frequency eddy current (MEC) testing, which merely targets the ferromagnetic steels. That is, at a certain working frequency, the measured inductance signal is found nearly immune to the lift-off distance of the sensor. Such working frequency and inductance are termed as the lift-off invariant frequency (LIF) and LII. Through simulations and experimental measurements of different steels under the multi-frequency manner, the LII has been verified to be merely related to the sensor parameters and independent of different steels. By referring to the LIF of the test piece and using an iterative inverse solver, one of the steel properties (either the electrical conductivity or magnetic permeability) can be reconstructed with a high accuracy.

Subject Areas

Eddy current testing; lift-off invariance; property measurement; multi-frequency; non-destructive testing.

Comments (1)

Comment 1
Received: 22 April 2021
Commenter: Mingyang Lu
Commenter's Conflict of Interests: Author
Comment: Reference
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