Inversion of lift-off distance and thickness for non-magnetic metal using eddy current testing

2020 ◽  
pp. 1-1
Author(s):  
Xiaobai Meng ◽  
Mingyang Lu ◽  
Wuliang Yin ◽  
Abdeldjalil Bennecer ◽  
Katherine J Kirk
Keyword(s):  
Eddy Current ◽  
Eddy Current Testing ◽  
Current Testing ◽  
Magnetic Metal ◽  
Lift Off

scholarly journals Inversion of Lift-Off Distance and Thickness for Non-Magnetic Metal Using Eddy Current Testing

2020 ◽  
Author(s):  
Xiaobai Meng ◽  
Mingyang Lu ◽  
Wuliang Yin ◽  
Abdeldjalil Bennecer ◽  
Katherine Kirk
Keyword(s):  
Eddy Current ◽  
Prediction Error ◽  
Skin Depth ◽  
Eddy Current Testing ◽  
Sample Thickness ◽  
Current Testing ◽  
Aluminium Copper ◽  
Magnetic Metal ◽  
Thickness Prediction ◽  
Lift Off

For the electromagnetic eddy current testing, various methods have been proposed for reducing the lift-off error on the measurement of samples. In this paper, instead of eliminating the measurement error caused by the lift-off effect, an algorithm has been proposed to directly measure the lift-off distance between the sensor and non-magnetic conductive plates. The algorithm is based on a sample-independent inductance (SII) feature. That is, under high working frequencies, the inductance is found sensitive to the lift-off distance and independent of the test piece under an optimal single high working frequency (43.87 kHz). Furthermore, the predicted lift-off distance is used for the thickness prediction of the non-magnetic conductive samples using an iterative method. Considering the eddy current skin depth, the thickness prediction is operated under a single lower frequency (0.20 kHz). As the inductance has different sensitivities to the lift-off and thickness, the prediction error of the sample thickness is different from that of the lift-off distance. From the experiments on three different nonmagnetic samples – aluminium, copper, and brass, the maximum prediction error of the lift-off distance and sample thickness is 1.1 mm and 5.42 % respectively at the lift-off of 12.0 mm.

scholarly journals Research on Detection Mechanism of Weld Defects of Carbon Steel Plate Based on Orthogonal Axial Eddy Current Probe

Sensors ◽  
2020 ◽  
Vol 20 (19) ◽  
pp. 5515
Author(s):  
Linnan Huang ◽  
Chunhui Liao ◽  
Xiaochun Song ◽  
Tao Chen ◽  
Xu Zhang ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Eddy Current ◽  
Steel Plate ◽  
Difficult Problem ◽  
Eddy Current Testing ◽  
Detection Sensitivity ◽  
Detection Mechanism ◽  
Current Testing ◽  
Weld Defects ◽  
Lift Off

The uneven surface of the weld seam makes eddy current testing more susceptible to the lift-off effect of the probe. Therefore, the defect of carbon steel plate welds has always been a difficult problem in eddy current testing. This study aimed to design a new type of eddy current orthogonal axial probe and establish the finite element simulation model of the probe. The effect of the probe structure, coil turns, and coil size on the detection sensitivity was simulated. Further, a designed orthogonal axial probe was used to conduct a systematic experiment on the weld of carbon steel specimens, and the 0.2 mm width and 1 mm depth of weld defects of carbon steel plates were effectively detected. The experimental results showed that the new orthogonal axial eddy current probe effectively suppressed the unevenness effect of the weld surface on the lift-off effect during the detection process.

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

Sensors ◽  
2021 ◽  
Vol 21 (2) ◽  
pp. 419
Author(s):  
Xiaobai Meng ◽  
Mingyang Lu ◽  
Wuliang Yin ◽  
Abdeldjalil Bennecer ◽  
Katherine J. Kirk
Keyword(s):  
Eddy Current ◽  
Coating Thickness ◽  
Thickness Measurement ◽  
Eddy Current Testing ◽  
Thickness Variation ◽  
Testing Technique ◽  
Current Testing ◽  
Thin Skin ◽  
Embedded Algorithms ◽  
Lift Off

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.

Differential coupling double-layer coil for eddy current testing with high lift-off

2021 ◽  
pp. 1-1
Author(s):  
Kefan Chen ◽  
Bin Gao ◽  
G.Y. Tian ◽  
Yupei Yang ◽  
Changrong Yang ◽  
...  
Keyword(s):  
Double Layer ◽  
Eddy Current ◽  
Eddy Current Testing ◽  
High Lift ◽  
Current Testing ◽  
Lift Off ◽  
Differential Coupling

scholarly journals The Effects of Lift-Off from Wall Thinning Signal in Pulsed Eddy Current Testing

2012 ◽  
Vol 17 (4) ◽  
pp. 298-301 ◽  
Author(s):  
Duck-Gun Park ◽  
C.S. Angani ◽  
M.B. Kishore ◽  
C.G. Kim ◽  
D.H. Lee
Keyword(s):  
Eddy Current ◽  
Eddy Current Testing ◽  
Current Testing ◽  
Pulsed Eddy Current ◽  
Wall Thinning ◽  
Lift Off

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

2021 ◽  
Author(s):  
Xiaobai Meng ◽  
Mingyang Lu ◽  
Wuliang Yin ◽  
Abdeldjalil Bennecer ◽  
Katherine Kirk
Keyword(s):  
Eddy Current ◽  
Coating Thickness ◽  
Thickness Measurement ◽  
Eddy Current Testing ◽  
Thickness Variation ◽  
Testing Technique ◽  
Current Testing ◽  
Thin Skin ◽  
Embedded Algorithms ◽  
Lift Off

Defect detection in ferromagnetic substrates is often hampered by non-magnetic 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 non-magnetic 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 multi-frequency 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.

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

2021 ◽  
Author(s):  
Mingyang Lu ◽  
Xiaobai Meng ◽  
Ruochen Huang ◽  
Liming Chen ◽  
Anthony Peyton ◽  
...  
Keyword(s):  
Eddy Current ◽  
High Accuracy ◽  
Eddy Current Testing ◽  
Current Testing ◽  
Pulsed Eddy Current ◽  
Working Frequency ◽  
Lift Off ◽  
Ferromagnetic Steels ◽  
Point Of Intersection ◽  
Steel Properties

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.

scholarly journals 204 Study on Methodology of Coincident Lift-off Measurement Using Optical System in Eddy Current Testing

2005 ◽  
Vol 2005.40 (0) ◽  
pp. 58-59
Author(s):  
Jun MATSUKAWA ◽  
Hisashi ENDO ◽  
Toshihiko ABE ◽  
Tetsuya UCHIMOTO ◽  
Toshiyuki TAKAGI
Keyword(s):  
Optical System ◽  
Eddy Current ◽  
Eddy Current Testing ◽  
Current Testing ◽  
Lift Off

A Novel Technique for Eliminating Probe Lift-Off in Eddy Current Nondestructive Testing

2013 ◽  
Vol 291-294 ◽  
pp. 2474-2478
Author(s):  
Bo Ye ◽  
Ming Li ◽  
Fang Zeng
Keyword(s):  
Nondestructive Testing ◽  
Eddy Current ◽  
Measurement Accuracy ◽  
Excitation Frequency ◽  
Eddy Current Testing ◽  
Basic Principles ◽  
Current Testing ◽  
Novel Technique ◽  
Simulation Results ◽  
Lift Off

The lift-off problem is a very important problem in eddy current testing, which will influence the measurement accuracy. This paper proposes a novel technique for eliminating the probe lift-off in eddy current nondestructive testing. Firstly, the basic principles and characteristics of eddy current testing were introduced. Secondly, this paper analyzed and studied the coil impedance responses caused by the variations of the probe lift-off. Based on simulation results, this paper presents that choosing proper probe excitation frequency can eliminate the disturbance of coil impedance caused by the lift-off, and obtains better results.

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