Evaluation of Coating Thickness Using Lift-Off Insensitivity of Eddy Current Sensor

Xiaobai Meng; Mingyang Lu; Wuliang Yin; Abdeldjalil Bennecer; Katherine J. Kirk

doi:10.3390/s21020419

Evaluation of Coating Thickness Using Lift-Off Insensitivity of Eddy Current Sensor

Xiaobai Meng, Mingyang Lu, Wuliang Yin, Abdeldjalil Bennecer, Katherine J. Kirk

EEE - Academic & Research

Research output: Contribution to journal › Article › peer-review

Abstract

Defect detection in ferromagnetic substrates is often hampered by nonmagnetic coating thickness variation when using conventional eddy current testing technique. The lift-off distance between the sample and the sensor is one of the main obstacles for the thickness measurement of nonmagnetic coatings on ferromagnetic substrates when using the eddy current testing technique. Based on the eddy current thin-skin effect and the lift-off insensitive inductance (LII), a simplified iterative algorithm is proposed for reducing the lift-off variation effect using a multifrequency sensor. Compared to the previous techniques on compensating the lift-off error (e.g., the lift-off point of intersection) while retrieving the thickness, the simplified inductance algorithms avoid the computation burden of integration, which are used as embedded algorithms for the online retrieval of lift-offs via each frequency channel. The LII is determined by the dimension and geometry of the sensor, thus eliminating the need for empirical calibration. The method is validated by means of experimental measurements of the inductance of coatings with different materials and thicknesses on ferrous substrates (dual-phase alloy). The error of the calculated coating thickness has been controlled to within 3% for an extended lift-off range of up to 10 mm.

Original language	English
Pages (from-to)	419
Journal	Sensors
Volume	21
Issue number	2
DOIs	https://doi.org/10.3390/s21020419
Publication status	Published - 11 Jan 2021

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10.3390/s21020419Licence: CC BY

https://www.mdpi.com/1424-8220/21/2/419

Electromagnetic Sensing Group
Peyton, A. (PI), Fletcher, A. (Researcher), Daniels, D. (CoI), Conniffe, D. (PGR student), Podd, F. (PI), Davidson, J. (Researcher), Anderson, J. (Support team), Wilson, J. (Researcher), Marsh, L. (PI), O'Toole, M. (PI), Watson, S. (PGR student), Yin, W. (PI), Regan, A. (PGR student), Williams, K. (Researcher), Rana, S. (Researcher), Khalil, K. (PGR student), Hills, D. (PGR student), Whyte, C. (PGR student), Wang, C. (PGR student), Hodgskin-Brown, R. (PGR student), Dadkhahtehrani, F. (PGR student), Forster, S. (PGR student), Zhu, F. (PGR student), Yu, K. (PGR student), Xiong, L. (PGR student), Lu, T. (PGR student), Zhang, L. (PGR student), Lyu, R. (PGR student), Zhu, R. (PGR student), She, S. (PGR student), Meng, T. (PGR student), Pang, X. (PGR student), Zheng, X. (PGR student), Bai, X. (PGR student), Zou, X. (PGR student), Ding, Y. (PGR student), Shao, Y. (PGR student), Xia, Z. (PGR student), Zhang, Z. (PGR student), Khangerey, R. (PGR student) & Lawless, B. (Researcher)
1/10/04 → …
Project: Research

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title = "Evaluation of Coating Thickness Using Lift-Off Insensitivity of Eddy Current Sensor",

abstract = "Defect detection in ferromagnetic substrates is often hampered by nonmagnetic coating thickness variation when using conventional eddy current testing technique. The lift-off distance between the sample and the sensor is one of the main obstacles for the thickness measurement of nonmagnetic coatings on ferromagnetic substrates when using the eddy current testing technique. Based on the eddy current thin-skin effect and the lift-off insensitive inductance (LII), a simplified iterative algorithm is proposed for reducing the lift-off variation effect using a multifrequency sensor. Compared to the previous techniques on compensating the lift-off error (e.g., the lift-off point of intersection) while retrieving the thickness, the simplified inductance algorithms avoid the computation burden of integration, which are used as embedded algorithms for the online retrieval of lift-offs via each frequency channel. The LII is determined by the dimension and geometry of the sensor, thus eliminating the need for empirical calibration. The method is validated by means of experimental measurements of the inductance of coatings with different materials and thicknesses on ferrous substrates (dual-phase alloy). The error of the calculated coating thickness has been controlled to within 3% for an extended lift-off range of up to 10 mm.",

author = "Xiaobai Meng and Mingyang Lu and Wuliang Yin and Abdeldjalil Bennecer and Kirk, {Katherine J.}",

year = "2021",

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T1 - Evaluation of Coating Thickness Using Lift-Off Insensitivity of Eddy Current Sensor

AU - Meng, Xiaobai

AU - Lu, Mingyang

AU - Yin, Wuliang

AU - Bennecer, Abdeldjalil

AU - Kirk, Katherine J.

PY - 2021/1/11

Y1 - 2021/1/11

N2 - Defect detection in ferromagnetic substrates is often hampered by nonmagnetic coating thickness variation when using conventional eddy current testing technique. The lift-off distance between the sample and the sensor is one of the main obstacles for the thickness measurement of nonmagnetic coatings on ferromagnetic substrates when using the eddy current testing technique. Based on the eddy current thin-skin effect and the lift-off insensitive inductance (LII), a simplified iterative algorithm is proposed for reducing the lift-off variation effect using a multifrequency sensor. Compared to the previous techniques on compensating the lift-off error (e.g., the lift-off point of intersection) while retrieving the thickness, the simplified inductance algorithms avoid the computation burden of integration, which are used as embedded algorithms for the online retrieval of lift-offs via each frequency channel. The LII is determined by the dimension and geometry of the sensor, thus eliminating the need for empirical calibration. The method is validated by means of experimental measurements of the inductance of coatings with different materials and thicknesses on ferrous substrates (dual-phase alloy). The error of the calculated coating thickness has been controlled to within 3% for an extended lift-off range of up to 10 mm.

AB - Defect detection in ferromagnetic substrates is often hampered by nonmagnetic coating thickness variation when using conventional eddy current testing technique. The lift-off distance between the sample and the sensor is one of the main obstacles for the thickness measurement of nonmagnetic coatings on ferromagnetic substrates when using the eddy current testing technique. Based on the eddy current thin-skin effect and the lift-off insensitive inductance (LII), a simplified iterative algorithm is proposed for reducing the lift-off variation effect using a multifrequency sensor. Compared to the previous techniques on compensating the lift-off error (e.g., the lift-off point of intersection) while retrieving the thickness, the simplified inductance algorithms avoid the computation burden of integration, which are used as embedded algorithms for the online retrieval of lift-offs via each frequency channel. The LII is determined by the dimension and geometry of the sensor, thus eliminating the need for empirical calibration. The method is validated by means of experimental measurements of the inductance of coatings with different materials and thicknesses on ferrous substrates (dual-phase alloy). The error of the calculated coating thickness has been controlled to within 3% for an extended lift-off range of up to 10 mm.

U2 - 10.3390/s21020419

DO - 10.3390/s21020419

M3 - Article

SN - 1424-8220

VL - 21

SP - 419

JO - Sensors

JF - Sensors

IS - 2

ER -

Evaluation of Coating Thickness Using Lift-Off Insensitivity of Eddy Current Sensor

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