Lift-Off Point of Intersection in Spectral Pulsed Eddy Current Signals for Thickness Measurement

2018 ◽  
Vol 2 (2) ◽  
pp. 1-4 ◽  
Author(s):  
Dongdong Wen ◽  
Mengbao Fan ◽  
Binghua Cao ◽  
Be Ye ◽  
Guiyun Tian
Keyword(s):  
Eddy Current ◽  
Thickness Measurement ◽  
Pulsed Eddy Current ◽  
Lift Off ◽  
Point Of Intersection

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.

Measurement of Wall Thinning through Insulation with Ferromagnetic Cladding Using Pulsed Eddy Current Testing

2011 ◽  
Vol 301-303 ◽  
pp. 426-429
Author(s):  
Zhi Yuan Xu ◽  
Xin Jun Wu ◽  
Chen Huang ◽  
Yi Hua Kang
Keyword(s):  
Eddy Current ◽  
Steel Plate ◽  
Thickness Measurement ◽  
Measurement Range ◽  
Galvanized Steel ◽  
Shielding Effect ◽  
Pulsed Eddy Current ◽  
Wall Thinning ◽  
The Common ◽  
Lift Off

Pulsed eddy current (PEC) technique has been successfully used for measuring wall thinning of carbon steel equipments without removal of the insulation. In field applications, the probe performance decreases in presence of ferromagnetic claddings. This paper presents a method based on saturation magnetization to solve this problem. The main principle of this method is to weaken the magnetic shielding effect of the cladding by magnetizing it to saturation. A U-shaped magnetizer is designed to realize this method. Contrast experiments are performed on a Q235 steel plate covered by a galvanized steel cladding. The experiment results show that the thickness measurement range and lift-off range are increased by applying this method to the common PEC probe.

Time-to-peak of time derivative signals of pulsed eddy current testing for evaluating the thickness of ferromagnetic samples

2021 ◽  
Vol 63 (2) ◽  
pp. 88-94
Author(s):  
Dongdong Wen ◽  
Shuchen Wang ◽  
Lei Zhang ◽  
Jianhua Zhang
Keyword(s):  
Eddy Current ◽  
Measurement Accuracy ◽  
Time Derivative ◽  
Thickness Measurement ◽  
Processing Method ◽  
Current Testing ◽  
Time To Peak ◽  
Pulsed Eddy Current ◽  
Precision Evaluation ◽  
Lift Off

The time-to-peak serves as a popular signal feature of pulsed eddy current (PEC) signals and is widely used in thickness measurement and defect detection. In order to further improve the ability of time-to-peak independent of the lift-off effect, a time derivative processing method is proposed in this paper to obtain a better time-to-peak feature of time derivative signals of PEC for reducing the lift-off effect. The method is used to improve the thickness measurement accuracy of ferromagnetic samples. The results of simulation and experimentation demonstrate that a time-to-peak feature of time derivative signals of PEC can be obtained using the time derivative processing method and the timeto-peak obtained from time derivative signals of PEC can be used to measure the thickness and improve the thickness measurement accuracy of ferromagnetic samples. This means that the use of the time-to-peak of time derivative signals of PEC is feasible for high-precision evaluation of the thickness of ferromagnetic samples.

Measurement of coating thickness using lift-off point of intersection features from pulsed eddy current signals

2020 ◽  
Vol 116 ◽  
pp. 102333 ◽  
Author(s):  
Yao Wang ◽  
Mengbao Fan ◽  
Binghua Cao ◽  
Bo Ye ◽  
Dongdong Wen
Keyword(s):  
Eddy Current ◽  
Coating Thickness ◽  
Pulsed Eddy Current ◽  
Lift Off ◽  
Point Of Intersection

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 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.

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.

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