Lift off compensation of eddy current crack detection system by controlling damping resistance of oscillator

Although remote field eddy current had achieved successive application in pipes and tubes non-destructive testing, the poor ability and sensitivity to axial crack such as stress corrosion crack prevented its further application. A novel high resolution remote field eddy current detection method which can be suitable for axial crack especially stress corrosion crack detection was proposed and verified by simulation and experiment. First of all, conventional detection ability of remote field eddy current for crack in different directions was researched with detail. Aside from this, applicability of orthogonal magnetic filed in remote field eddy current was analyzed and simulated by finite element method, and appropriate configuration using to generating orthogonal magnetic fields for tubular structure was discussed and verified. Thirdly, design of detection system including key parameters selection and detection coil mode were researched. At last, proposed high resolution detection system were verified experimentally using various type defects, such as parallel axial crack and real stress corrosion crack. From the above research, conclusions were drawn as followed: the detection ability and sensitivity of proposed remote field eddy current detection system could be improved significantly compared with conventional system, especially for axial crack which was not easily to detect, and real stress corrosion crack could be detected and evaluated successively.

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Design of orthogonal eddy-current probe for weld crack detection of carbon-steel plate

International Journal of Applied Electromagnetics and Mechanics ◽

10.3233/jae-209453 ◽

2020 ◽

Vol 64 (1-4) ◽

pp. 1347-1355

Author(s):

Tao Chen ◽

Xiaoqi Xiao ◽

Lihong Zhang ◽

Cheng Lv ◽

Zhiyang Deng ◽

...

Keyword(s):

Carbon Steel ◽

Eddy Current ◽

Crack Detection ◽

Steel Plate ◽

Signal To Noise Ratio ◽

Detection Sensitivity ◽

Scanning Angle ◽

Length Width ◽

Lift Off ◽

Detection Effect

Due to uneven surface and lift-off effect, it is difficult to detect weld crack by eddy-current testing. A new orthogonal eddy-current probe for weld crack detection of carbon-steel plate was designed in this paper. Based on COMSOL Multiphysics, the influence of scanning angle on detection sensitivity of the probe was compared firstly. Then, the effects of coil width, coil side length, detection coil height, and lift-off distance on detection sensitivity of the probe were studied, respectively. Finally, the test piece of carbon-steel plate weld with crack, and the physical probe used to verify the crack detection effect were made. The experimental results show that the weld crack of carbon-steel plate with length × width × depth of 20.0 mm × 0.3 mm × 1 mm can be effectively identified, and the lift-off noise can be effectively suppressed by the method presented in this paper. At the same time, the signal-to-noise ratio of the probe keeps constant in the lift-off distance range of 0.3 mm–3.0 mm.

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Anisotropy magnetoresistance differential probe for characterization of sub-millimeter surface defects on galvanized steel plate

Measurement and Control ◽

10.1177/00202940211028618 ◽

2021 ◽

pp. 002029402110286

Author(s):

Nurul A’in Nadzri ◽

Mohd Mawardi Saari ◽

Mohd Aufa Hadi Putera Zaini ◽

Aiman Mohd Halil ◽

Mahadzir Ishak ◽

...

Keyword(s):

Eddy Current ◽

Crack Detection ◽

Surface Defects ◽

Detection System ◽

Early Stage ◽

Metal Structure ◽

Galvanized Steel ◽

Small Scale ◽

Excitation Coil ◽

The Future

Defects such as cracks can cause dangerous damage to the metal structure and may lead to structural collapses. Cracks can exist in various shapes and sizes where they can start to develop from small scale lower than 1 mm and spread to contribute to the complete fracture of components. Hence, early discovery and monitoring of any cracks in their early stage are crucial to prevent any sudden fatal accidents in the future. This work presents the study and detailed analysis of an ECT probe’s development based on AMR sensors to identify sub-millimeter surface cracks in galvanized steel plates. The probe consists of an excitation coil that induces an eddy current in sample plates and two AMR sensors that detect the differential eddy current-induced magnetic response. A phase-sensitive detection technique with a lock-in amplifier is used to evaluate the magnetic field distribution detected by the AMR sensors. The measured magnetic responses are classified to the depth, width, length, and complex shapes of artificial slits, and the probe is used to perform line scans and 2-D map scans above the slits’ positions. The probe was able to characterize slits with a depth and width as low as 210 and 50 µm, respectively, by using an excitation current of 4 mA at 1 kHz. The slit orientations that were perpendicular to the differential direction of the AMR sensors were clearly visualized, with their estimated lengths showed a good correlation with the physical slit lengths. In the future, the developed system can be expected to help towards the development of a more sophisticated crack detection system where real-time inspections can be realized and applied in various fields.

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An Eddy Current-Capacitive Crack Detection Probe with High Insensitivity to Lift-Off

IECON 2018 - 44th Annual Conference of the IEEE Industrial Electronics Society ◽

10.1109/iecon.2018.8591254 ◽

2018 ◽

Cited By ~ 1

Author(s):

S. Sreevatsan ◽

Boby George ◽

Tan Zhichao

Keyword(s):

Eddy Current ◽

Crack Detection ◽

Detection Probe ◽

Lift Off

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Challenges in improving the performance of eddy current testing: Review

Measurement and Control ◽

10.1177/0020294018801382 ◽

2018 ◽

Vol 52 (1-2) ◽

pp. 46-64 ◽

Cited By ~ 12

Author(s):

Ahmed N AbdAlla ◽

Moneer A Faraj ◽

Fahmi Samsuri ◽

Damhuji Rifai ◽

Kharudin Ali ◽

...

Keyword(s):

Eddy Current ◽

Crack Detection ◽

Oil And Gas ◽

Structure Design ◽

Eddy Current Testing ◽

Testing Technique ◽

Current Testing ◽

Advantages And Disadvantages ◽

Lift Off ◽

Design Factors

Eddy current testing plays an important role in numerous industries, particularly in material coating, nuclear and oil and gas. However, the eddy current testing technique still needs to focus on the details of probe structure and its application. This paper presents an overview of eddy current testing technique and the probe structure design factors that affect the accuracy of crack detection. The first part focuses on the development of different types of eddy current testing probes and their advantages and disadvantages. A review of previous studies that examined testing samples, eddy current testing probe structures and a review of factors contributing to eddy current signals is also presented. The second part mainly comprised an in-depth discussion of the lift-off effect with particular consideration of ensuring that defects are correctly measured, and the eddy current testing probes are optimized. Finally, a comprehensive review of previous studies on the application of intelligent eddy current testing crack detection in non destructive eddy current testing is presented.

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

Sensors ◽

10.3390/s20195515 ◽

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.

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Deep Learning-Based Automatic Safety Detection System for Crack Detection

2020 7th International Conference on Dependable Systems and Their Applications (DSA) ◽

10.1109/dsa51864.2020.00034 ◽

2020 ◽

Author(s):

Quan Chen ◽

Xi-Xi Zhang ◽

Yu Chen ◽

Wei Jiang ◽

Guan Gui ◽

...

Keyword(s):

Deep Learning ◽

Crack Detection ◽

Detection System

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

Sensors ◽

10.3390/s21020419 ◽

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.

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