J. Instrum. In pipeline inspection, the MFL device is propelled by the gas and oil inside the pipe. Measurement 47, 613626 (2014). Uhlig R.P., Zec M., Brauer H., Thess A. Lorentz Force Eddy Current Testing: A Prototype Model. Antipov A.G., Markov A.A. Bowler derived an analytical solution for semi-elliptical indentation by solving the Laplace equation of a static magnetic field, and the results turned to be in agreement with those from the dipole model [19]. Sun Y., Kang Y. Magn. The defect sizes and corresponding signals (or signal features) are fed into the network to update the weights. https://doi.org/10.19650/j.cnki.cjsi.2012.09.009, Tsukada, K., Yoshioka, M., Kawasaki, Y., Kiwa, T.: Detection of back-side pit on a ferrous plate by magnetic flux leakage method with analyzing magnetic field vector. Sun proposed an opening electromagnetic transducer, as shown in Figure 11, which facilitates the insertion of specimens [98,99]. Chin. In E. Lis paper, it is reported that the smallest crack that can be detected is with a depth of 7 m. Ryu K.S., Atherton D.L., Clapham L. Effect of Pit Geometry and Bulk Stress on Near- and Far-Side Calculated MFL Signals. K. Hwang employed the wavelet basis function (WBF) neural network to the MFL signal to a three-dimensional defect profile [140]. The machine learning-based algorithm usually requires a large training set, and the iteration-based algorithm usually requires large computational resources during the iteration process. Influence of Motion Induced Eddy Current on the Magnetization of Steel Pipe and MFL Signal. Int. Both algorithms achieved relatively good accuracy on defect quantification. Fast Reconstruction of Defect Profiles from Magnetic Flux Leakage Measurements Using a RBFNN Based Error Adjustment Methodology. They found that it was possible to detect cracks that are parallel to the magnetization, although the amplitude was small. A comparison between the distributions of the eddy current and magnetic field at different speeds is shown in Figure 10. Shcherbinin V., Pashagin A. Kandroodi M.R., Araabi B.N., Bassiri M.M., Ahmadabadi M.N. J. Philip and V. Mahendran have proposed the use of a ferrofluid emulsion film to visualize the leakage magnetic field [134,135,136]. Procedia Eng. For a line with infinitesimal length dy on the slot surface shown in Figure 3a, the magnetic charge is dp=mdy, and in the 3D model shown in Figure 3b, the charge is dp=mdydz. If there is no defect in the material, most magnetic ux lines will pass through the inside Theoretical Analysis on the Distribution of Eddy Current in Motion This article describes the working principle, capabilities, applications and limitations of magnetic flux leakage (MFL) technique for nondestructive detection and sizing of defects in. Magnetic Focusing Method and Sensor in Surface Topography Testing for Ferromagnetic Materials. The magnetization strength can be easily adjusted by changing the current in the coil and the current can be turned off during the installation. 1335, 12561263 (2011). Rao proposed the use of an Eigen vector-based approach to suppress the noise caused by non-linear permeability, surface roughness, stresses, and liftoff variations in MFL images [94]. With the rapid development of image processing technology, especially deep learning techniques such as CNN, displaying the MFL testing results as gray-scale images (Figure 16b) would facilitate the application of corresponding algorithms to extract defect information. Y. Wang also studied the stress-dependent MFL signals in Q235 steel plates [82]. The Magnetic Leakage Field of Surface-Breaking Cracks. Tang J., Wang R., Zhang J., Kang Y. T. Nara designed a Fourier coil consisting of two coils of radial offset [133]. Wu Z., Deng Y., Wang L. A Pinning Actor-Critic Structure-Based Algorithm for Sizing Complex-Shaped Depth Profiles in MFL Inspection with High Degree of Freedom. The ultimate goal of non-destructive testing can be classified into three levels. Li H., Chen Z., Zhang D., Sun H. Reconstruction of Magnetic Charge on Breaking Flaw Based on Two-Layers Algorithm. Influence of magnetizing current on MFL signal. Liu S., Sun Y., He L., Kang Y. Pearson N.R., Boat M.A., Priewald R.H., Pate M.J., Mason J.S.D. Sun compared MFL with PMP and stated that the PMP method can accomplish inspection in a narrower operation space and is more suitable for omni-directional cracks [170,171]. Kandroodi used the MFL signal contour to determine the defect length and width and used the signal peak-to-peak values along with the estimated length and width to estimate the defect depth [142]. 28, 3540 (1995), Kundu, T., Bergamini, A., Christen, R.: A simple approach to the localization of flaws in large diameter steel cables. If the error is less than a desirable value, the profile will be regarded as the final estimation, otherwise, the error is used to update the defect profile and repeat the process of forward calculation. Based on their study, many researchers have further derived the distribution of the leakage field generated by a 2D notch and a 3D notch [8,9]. Experimental and Finite Element Analysis Study of 3D Magnetic Field Sensing for Pulsed Magnetic Flux Leakage Defect Characterization. Z. Deng compared MFL with MPP and found that MPP can detect defects that are buried deeper than MFL [169]. In recent studies, magnetic field sensors with higher sensitivities have been used in MFL testing for the detection of tiny cracks. Wu J., Xia H., Feng B., Li E., Huang X., Kang Y. Tehranchi M.M., Ranjbaran M., Eftekhari H. Double Core Giant Magneto-Impedance Sensors for the Inspection of Magnetic Flux Leakage from Metal Surface Cracks. Based on the model, the effects of defect size, defect orientation, and liftoff distance have been analyzed. Gotoh also used low-frequency AC excitation to increase the penetration depth and detected outer side cracks in a steel plate 3 mm thick [106,107]. In order to reduce the velocity impact, Usarek studied the change in the magnetic field with velocity and found that both tangential and normal components of the magnetic field increase with velocity linearly and used an empirical fitting equation to compensate for the MFL signal [65]. 82, 1325 (2016). Tehranchi M.M., Hamidi S.M., Eftekhari H., Karbaschi M., Ranjbaran M. The Inspection of Magnetic Flux Leakage from Metal Surface Cracks by Magneto-Optical Sensors. Later, he proposed a new MFL principle based on near-zero background magnetic field [44], in which magnetic shielding is used to collect a strong background field. In 1918, it was found that powder was absorbed near defects due to the changes in surface magnetic field; thus, magnetic particle detection method was invented. Wang Y., Melikhov Y., Meydan T., Yang Z., Wu D., Wu B., He C., Liu X. Stress-Dependent Magnetic Flux Leakage: Finite Element Modelling Simulations Versus Experiments. The magnetizer can be either a magnet with a ferromagnetic yoke or a magnetizing coil. An Estimation Method of Defect Size from MFL Image Using Visual Transformation Convolutional Neural Network. Instrum. IEEE Sens. ; writingreview and editing, J.W. Kataoka Y., Murayama S., Wakiwaka H., Shinoura O. https://creativecommons.org/licenses/by/4.0/. Sun Y., Kang Y. Rocha T.J., Ramos H.G., Lopes Ribeiro A., Pasadas D.J. It consists of three modules, two of which are for the inspection of transverse and longitudinal cracks and a demagnetizing module to demagnetize the pipe after inspection. Sun Y., Wu J., Feng B., Kang Y. Kallias G., Devlin E., Christides C., Niarchos D. High Tc SQUID Sensor System for Non-Destructive Evaluation. Sensors 19, 4869 (2019). Hwang K., Mandayam S., Udpa S.S., Udpa L., Lord W., Atzal M. Characterization of Gas Pipeline Inspection Signals Using Wavelet Basis Function Neural Networks. 1620. An official website of the United States government. https://doi.org/10.1016/j.proeng, Gotoh, Y., Takahashi, N.: Proposal of detecting method of outer side crack by alternating flux leakage testing using 3-D nonlinear FEM. It is a nondestructive testing technique which uses magnetic sensitive sensors to detect the magnetic leakage field of defects on both the internal and external surfaces of pipelines. An inductive coil sensor or a Hall effect sensor detects the leakage. The influence of the velocity on the MFL signal has also been extensively studied. Mahendran V., Philip J. Li E., Kang Y., Tang J., Wu J. A magnetic shielding strategy for magnetic sensor in magnetic flux This is a preview of subscription content, access via Feng B., Kang Y., Sun Y. (2017). Hall element is able to measure the absolute value of the magnetic field; however, when the sensor is near the poles of the magnetizer, it may operate outside the linear range. Magnetic flux leakage (MFL) is a magnetic method of non-destructive testing that is used to detect corrosion, pitting and wall loss in steel structures. 18, 65406546 (2018). Y. One of the most important applications is underground pipeline inspection, where the so-called pipeline inspection gauge (PIG) is used. As early as 1868, the British Naval Architects Association began to use magnetic flux leakage technology and found defects on steel pipe through the compass. Lukyanets S., Snarskii A., Shamonin M., Bakaev V. Calculation of Magnetic Leakage Field from a Surface Defect in a Linear Ferromagnetic Material: An Analytical Approach. A Multi-sensors method is proposed. Van Der Horst M.P., Van Kreveld S.L., Kaminski M.L. He integrated the MFL theory into the loss function and proposed a physics-informed doubly fed cross-residual network that estimated the defect length, width, and depth accurately [146]. Review and Analysis of Three Representative Electromagnetic NDT Methods. Magnetic flux leakage (MFL) testing is a widely used nondestructive testing (NDT) method for the inspection of ferromagnetic materials. The widely applied magnetic flux leakage (MFL) nondestructive testing for ferrous materials has been simply explained by "MFL escaping from defects and being induced is exactly the MFL. The depth of defect is often accepted for justifying the dangerousness of defects [2]. To begin the defect quantification process, an initial estimate of the defect profile is required. Magnetic flux leakage (MFL) testing is a prospectiv e method for quantifying defects [1]. Trevino proposed an improved dipole model to calculate the MFL of conical, ellipsoidal, and tensional shaped defects [15]. Subsequently, many researchers have studied the signal characteristics and extracted features for defect quantification and discrimination of internal and external defects [111,112,113,114]. This effect can also be obtained by extracting the magnetic field along different directions using Equations (4)(6). Huang X., Wu J., Sun Y., Kang Y. To make the inductive coil detect both external and internal defects under static conditions in magnetic flux leakage testing (MFL), this paper proposes a method based on the AC and DC composite magnetization. https://doi.org/10.1063/1.3592078. Improved FEM model for defect-shape construction from MFL signal by using genetic algorithm. S. Lu proposed a visual transformation CNN for defect quantification and improved the accuracy of estimation for length, width, and depth by 26.9%, 27.1%, and 33.3% [144]. In this case, the flux line continues at the interface without any perturbation, and there is no leakage magnetic field. A Review of Magnetic Flux Leakage Nondestructive Testing Then the magnetic field in the material leaks from areas where metal is lost, such as corrosion or defects, forming the MFL . Magnetic Flux Leakage Scanning Velocities for Tank Floor Inspection. Wu J., Xia H., Feng B., Li E., Huang X., Kang Y. Nondestruct. Later, genetic algorithms [162], particle swarm optimization [163,164,165], and cuckoo search [166,167] have been applied to quantify defects in MFL testing. However, due to the skin effect, it can only detect surface defects and has strict requirements on surface quality. With the advantages of high efficiency, low cost, and environmental friendliness, MFL has been applied in many applications such as underground pipelines, seamless steel piles, drill pipes, sucker rods, and bearings. Usually, there are types of forward models that can be used, namely the magnetic dipole model, finite element model, and neural network model. Due to these features, magnet-based magnetizers are especially suitable for use in portable devices and inspection robots for the inspection of wire ropes and transmission pipelines. Kasai N., Sekine K., Maruyama H. Influence of Corrosion Products on Magnetic Flux Leakage Signals in Inspection of Far-Side Metal-Loss Defects in Oil Storage Tank Bottom Floors. Among the testing methods, the MFL is the most commonly used. Recently, B. Feng found an analytical solution to Equation (9) and further obtained the expression of the motion-induced eddy current under a pole of the magnetizer [51]: where Jtotal is the eddy current in specimen, y0 is the liftoff, h is the height of magnetizer, CxIII, CyIII, DxIII and DyIII are coefficients that are solved as [51]: With the analytical solution of the MIEC, the tail effect and tilt angle of the MIEC at different moving speeds are also analyzed [51]. Zhang derived an analytical expression for internal defects using a modified dipole model and image theory [17]. Thus, a lot of effort has been put into the study of the quantification of defects, which is a classical inverse problem. Influence of the extension of a defect on the magnitude of its magnetic field. Park G.S., Park S.H. Sun Y., Kang Y., Qiu C. A New NDT Method Based on Permanent Magnetic Field Perturbation. Jia used a filtering method to suppress liftoff interference [36]; Wu proposed a liftoff tolerant sensor by inserting ferrite into the sensing coil [37]; Peng introduced an exponential function compensation for liftoff correction [38]; Wang linearized the liftoff effect by applying Fourier transform [39]. Corrosion of the tank floor can lead to the loss of product and cause damage to the . Theory and Application of Magnetic Flux Leakage Pipeline Detection - MDPI In MFL testing, there are many factors that influence the inspection signal. 86, 406419 (2014). This technique will normally be applied as a fast screening technique if small diameter pitting is expected. In: 2017 IEEE Sensors Applications Symposium (SAS). Influences of Magnetization Direction on the Flux Leakage Field of Weld Y. Wang proposed a multi-physics simulation model to study the change in MFL signal with stress and showed that the peak-to-peak amplitude of the normalized MFL signal decreases with an increase in stress [80]. G. Park and Y. Jia both considered adding a ferromagnetic backing near the sensor to enhance the MFL signal [124,125]. This paper presents a method to characterize dents based on the analysis of the BJ Vectra Magnetic Flux Leakage (MFL) tool signals. government site. ), have been introduced in detail. An Opening Electric-MFL Detector for the NDT of In-Service Mine Hoist Wire. For the inspection of longitudinal cracks, magnetizers with two shoes that are 180 away from each other are used to generate magnetic fields in the circumferential direction. Basic principle of MFL testing: (a) yoke-type magnetizer; (b) encircling coil-type magnetizer. Antipov A.G., Markov A.A. 3D Simulation and Experiment on High Speed Rail MFL Inspection. Pullen A.L., Charlton P.C., Pearson N.R., Whitehead N.J. NDT E Int. Mandache C., Clapham L. A Model for Magnetic Flux Leakage Signal Predictions. Kasai studied the MFL testing signal for samples covered by corrosion (iron oxides) and showed that the MFL signal decreased with increasing iron oxide ratio [78]. For the defect shown in Figure 3b, the magnetic field above the center of the defect (y = 1, z = 0) was extracted and the results are shown in Figure 5. 43, 323328 (2010). Priewald R.H., Magele C., Ledger P.D., Pearson N.R., Mason J.S.D. Du Z., Ruan J., Peng Y., Yu S., Zhang Y., Gan Y., Li T. 3-D FEM Simulation of Velocity Effects on Magnetic Flux Leakage Testing Signals. : Novel eddy current probes for pipes: Application in austenitic round-in-square profiles of ITER. The MFL signal reduces as the increase in liftoff distance [33,34,35], an example of liftoff effect is shown in Figure 8. Hayashi proposed an unsaturated ACMFL testing method for reinforcing steel bars and achieved defect inspection at high liftoff of up to 100 mm [108]. An analytical expression for the leakage magnetic field based on the 3D magnetic dipole model is provided. Estimation of Depth and Length of Defects from Magnetic Flux Leakage Measurements: Verification with Simulations, Experiments, and Pigging Data. Magnetic methods of nondestructive testing (NDT) depend on detecting this magnetic flux leakage field. Finite Element Calculation of Magnetic Flux Leakage Detector Signals. Coils have a wider measurement range; however, they only measure the rate of change in the magnetic field instead of its absolute value. Due to the skin effect, the magnetic field concentrates on the surface of the specimen, thus the surface can be saturated with a relatively small excitation current. NDT E Int. Sens. 3D Reconstructing of Arbitrary Defects with Magnetic Flux Leakage IEEE Trans. Ji F., Wang C., Sun S., Wang W. Application of 3-D FEM in the Simulation Analysis for MFL Signals. Feng B., Kang Y., Sun Y., Yang Y., Yan X. Visualizing MFL testing signals: (a) multi-channel time-domain signals; (b) gray-scale images. The combined DC and AC excitation has also been used in MFL testing. Evaluation of Subsurface Defects Using Diffusion of Motion-Induced Eddy Currents. A double U-shaped orthogonal magnetizer, as shown in Figure 12, can be used to overcome this problem, although it was originally developed for alternating current field measurement (ACFM) [103]. Magnetic Flux Leakage (MFL) - Intertek After generating a leakage field with appropriate excitation, sensing is the vital step to pick up the leakage field. Long Y., Huang S., Peng L., Wang S., Zhao W. A Novel Compensation Method of Probe Gesture for Magnetic Flux Leakage Testing. The research is addressed through both designed experiments and simulations. At the interface of the two media, the magnetic elds satisfy the boundary equations; thus, the refracted angle is expressed as: a2 = arctan(m2 m1 IEEE, Glassboro, NJ, USA, pp. The properties of ferromagnetic materials change with the loading stress due to the magneto-mechanical coupling, thus the MFL signal also changes with the stress. Therefore, external and internal defects can generate a time-varying leakage magnetic field. Azizzadeh T., Safizadeh M.S. The encircling coil-based magnetizer has the advantage of providing a strong and adjustable magnetizing field; however, wires are closed, making it difficult for certain specimens such as wire ropes and coiled tubing to be inserted into the middle of the coil. Then, a forward MFL model is used to calculate the MFL signal generated by the defect profile. 42, 14151418 (2006). https://doi.org/10.1016/j.ndteint.2008.11.003, Nakahata, K., Tokumasu, S., Sakai, A., Iwata, Y., Ohira, K., Ogura, Y.: Ultrasonic imaging using signal post-processing for a flexible array transducer. Jia Y., Lu Y., Xiong L., Zhang Y., Wang P., Zhou H. A Filtering Method for Suppressing the Lift-Off Interference in Magnetic Flux Leakage Detection of Rail Head Surface Defect. The DC magnetization makes the defects generate static leakage magnetic field. The MFL testing device usually consists of a magnetizing unit, a sensing unit, a signal conditioning unit, an analog-to-digital converter (ADC), and a computer with signal displaying and analyzing software. 103, 4861 (2019). 2931 July 2011; pp. Parra-Raad J.A., Roa-Prada S. Multi-Objective Optimization of a Magnetic Circuit for Magnetic Flux Leakage-Type Non-Destructive Testing. Principle of Magnetic Flux Leakage Detection The basic idea of magnetic ux leakage inspection is that the ferromagnetic material is magnetized close to saturation under the applied magnetic eld. Abstract This work investigates the influence of acceleration on the leakage signal in magnetic flux leakage type of non-destructive testing. Khodayari-Rostamabad A., Reilly J.P., Nikolova N.K., Hare J.R., Pasha S. Machine Learning Techniques for the Analysis of Magnetic Flux Leakage Images in Pipeline Inspection. A New Micro Magnetic Bridge Probe in Magnetic Flux Leakage for Detecting Micro-Cracks. In another study, B.P.C. Amineh R.K., Nikolova N.K., Reilly J.P., Hare J.R. Park G.S., Park E.S. Magnetic flux leakage (MFL) testing is a widely used nondestructive testing (NDT) method for the inspection of ferromagnetic materials. The phenomenon of magnetic eld leakage was explained using the refraction of the magnetic eld by Sun and Kang with the boundary conditions of the electromagnetic eld [5], as shown in Figure2a. A High-Sensitivity MFL Method for Tiny Cracks in Bearing Rings. In addition, MFL has the advantage of automatic inspection; thus, it is replacing MPI in several fields, such as the inspection of bearing, as shown in Figure 15d. Magnetic Flux Leakage Testing | PDF | Manufactured Goods - Scribd 3D Magnetic Dipole Models of Magnetic Flux Leakage for concave and Bump Defects. Firstly, the principle of MFL testing has been explained with the theory of refracted magnetic field and an analytical expression for the leakage magnetic field has been derived based on the 3D magnetic dipole model. Uetake I., Saito T. Magnetic Flux Leakage by Adjacent Parallel Surface Slots. Magn. With the increase in computer performance, deep neural networks that require massive computational resources have been applied in many industrial fields. the contents by NLM or the National Institutes of Health. The conventional yoke type magnetizer only generates a magnetic field in one direction and has limited sensitivity for cracks that are parallel to the magnetic field. Feng B., Deng K., Wang S., Chen S., Kang Y. S. Liu proposed a magnetic focusing sensor that adds a magnetic guide core and a permanent magnet to coils [130]. PDF Characterizing the Surface Crack Size by Magnetic Flux Leakage Testing Other influencing factors, such as magnetization strength, testing speed, surface roughness, and stress, have also been introduced. A Novel Magnetic Flux Leakage Testing Method Based on AC and DC Composite Magnetization. 36, 68 (2017). UT can detect internal defects but requires couplant. Kataoka and Singh used a giant magnetoresistance (GMR) line sensor and flexible GMR sensor array in MFL [118,119]. Chen G., Li W., Wang Z. A Review of Magnetic Flux Leakage Nondestructive Testing - MDPI PDF Theory and Application of Magnetic Flux Leakage Pipeline Detection Kallias and Krause discussed the potential of using a superconducting quantum interference device (SQUID) in nondestructive testing [122,123]. https://doi.org/10.3390/s19224869, Ramos, H.G., Ribeiro, A.L. 52, 12311236 (2016). There are two common ways to display and visualize multi-channel signals. Machine learning techniques showed great success in tasks such as classification and regression. The basic principles are shown in Figure2. Yang also studied the effect of surface roughness on the SNR of MFL signals and proposed the use of a magnetic medium to improve the SNR [93]. Shi Y., Zhang C., Li R., Cai M., Jia G. Theory and Application of Magnetic Flux Leakage Pipeline Detection. 42, 157161 (2009). Pulsed Electromagnetic Methods for Defect Detection and Characterisation. Sun Y., Feng B., Ye Z., Liu S., Li D., Kang Y., Gu M., Liu C. Change Trends of Magnetic Flux Leakage with Increasing Magnetic Excitation. and Y.K. Eval. With either a permanent magnet or coil, a ferromagnetic yoke can be used to formulate magnetic circuits with less magnetic reluctance to increase the magnetization inside the specimens. Stress-Induced Self-Magnetic Flux Leakage at Stress Concentration Zone. Babbar V., Shiari B., Clapham L. Mechanical Damage Detection With Magnetic Flux Leakage Tools: Modeling the Effect of Localized Residual Stresses. your institution, https://doi.org/10.1016/j.ndteint.2019.02.003, https://doi.org/10.1016/j.ndteint.2009.09.001, https://doi.org/10.1016/j.ndteint.2008.11.003, https://doi.org/10.1016/j.ndteint.2016.04.002, https://doi.org/10.1016/j.sna.2020.111844, https://doi.org/10.1016/j.ndteint.2017.02.001, https://doi.org/10.19650/j.cnki.cjsi.2012.09.009, https://doi.org/10.1016/j.ndteint.2010.01.004, https://doi.org/10.1016/j.sna.2005.07.013, https://doi.org/10.1016/j.ndteint.2006.12.008, https://doi.org/10.1080/10589750802588010, https://doi.org/10.1016/j.measurement.2013.09.047, https://doi.org/10.1023/B:JONE.0000010736.74285.b6, https://doi.org/10.1007/s10921-017-0447-z, https://doi.org/10.1109/tmag.2009.2024894, https://doi.org/10.1109/jsen.2018.2850977. Yu G., Liu J., Zhang H., Liu C. An Iterative Stacking Method for Pipeline Defect Inversion with Complex MFL Signals. Feng J., Li F., Lu S., Liu J., Ma D. Injurious or Noninjurious Defect Identification from MFL Images in Pipeline Inspection Using Convolutional Neural Network. Wang P., Xiong L., Sun Y., Wang H., Tian G. Features Extraction of Sensor Array Based PMFL Technology for Detection of Rail Cracks. Eval. Wang Y., Cheng Y., Bai L., Zhang J., Yu H., Alimey F.J. Solenoid Model for the Magnetic Flux Leakage Testing Based on the Molecular Current. Magnetic Flux Leakage Testing | Request PDF - ResearchGate Meas. Eval. Before Uetake studied the MFL of adjacent parallel surface slots [10]. Google Scholar, Hunter, A.J., Drinkwater, B.W., Wilcox, P.D. The method involves magnetizing the test object with a static magnetic field source (magnetizing system). Energies | Free Full-Text | Deep Learning for Magnetic Flux Leakage Piao G., Guo J., Hu T., Leung H. The Effect of Motion-Induced Eddy Current on High-Speed Magnetic Flux Leakage (MFL) Inspection for Thick-Wall Steel Pipe. Usarek Z., Chmielewski M., Piotrowski L. Reduction of the Velocity Impact on the Magnetic Flux Leakage Signal. In the automobile industry, bearings were previously tested by the method of magnetic particle inspection (MPI). : Present and future impact of magnetic sensors in NDE. Tian proposed the PMFL method, in which a square waveform is applied as the excitation signal [109]. Theoretical Analyses of MFL Signal Affected by Discontinuity Orientation and Sensor-Scanning Direction. IEEE Trans. NDT E Int. Tehranchi used a double-core giant magneto-impedance (GMI) sensor in the testing of steel plates [120]. This review paper presents the basic principles of MFL testing and summarizes the recent advances in MFL. Piao G., Li J., Udpa L., Udpa S., Deng Y. Due to the abrupt change in magnetic reluctance at the defects, the magnetic flux leaks into the nearby air. Simulation of magnetic field distribution is of great significance for design an efficient MFLT system in the nondestructive testing applications. For the 3D model in Figure 3b, the results are: According to Equations (4)(6), the distribution of magnetic field above a notch can be calculated. The advantage of MFL over MPI is the easiness of implementing automatic testing; however, at the same time, it has lower sensitivity than MPI. Han W., Xu J., Zhou M., Tian G., Wang P., Shen X., Hou E. Cuckoo Search and Particle Filter-Based Inversing Approach to Estimating Defects via Magnetic Flux Leakage Signals. Zhang L., Belblidia F., Cameron I., Sienz J., Boat M., Pearson N. Influence of Specimen Velocity on the Leakage Signal in Magnetic Flux Leakage Type Nondestructive Testing. The most commonly used sensors are the Hall element and coils. (of this report) Unclassified 20. J. Appl. Publishers Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Theoretical Analysis on the Distribution of Eddy Current in Motion-Induced Eddy Current Testing and High-Speed MFL Testing. Comparison of Inspecting Non-Ferromagnetic and Ferromagnetic Metals Using Velocity Induced Eddy Current Probe. https://doi.org/10.1016/j.ndteint.2010.01.004, Song, N., Haga, Y., Goda, T., Sakai, K., Kiwa, T., Tsukada, K.: Detecting internal defects of a steel plate by using low-frequency magnetic flux leakage method. For the inspection of transverse cracks, encircling coils have been used to generate axial magnetic fields in steel pipes. Chang Y., Jiao J., Li G., Liu X., He C., Wu B. MFL technique belongs to the category of electromagnetic NDT. Zhang Y., Ye Z., Wang C. A Fast Method for Rectangular Crack Sizes Reconstruction in Magnetic Flux Leakage Testing.
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