An Analytical Model for Prediction of Magnetic Flux Leakage from Surface Defects in Ferromagnetic Tubes

Abstract In this paper, an analytical model is proposed to predict magnetic flux leakage (MFL) signals from the surface defects in ferromagnetic tubes. The analytical expression consists of elliptic integrals of first kind based on the magnetic dipole model. The radial (Bz) component of leakage fields is computed from the cylindrical holes in ferromagnetic tubes. The effectiveness of the model has been studied by analyzing MFL signals as a function of the defect parameters and lift-off. The model predicted results are verified with experimental results and a good agreement is observed between the analytical and the experimental results. This analytical expression could be used for quick prediction of MFL signals and also input data for defect reconstructions in inverse MFL problem.

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A Method for Detecting Surface Defects in Railhead by Magnetic Flux Leakage

Applied Sciences ◽

10.3390/app11209489 ◽

2021 ◽

Vol 11 (20) ◽

pp. 9489

Author(s):

Yinliang Jia ◽

Shicheng Zhang ◽

Ping Wang ◽

Kailun Ji

Keyword(s):

Magnetic Flux ◽

Surface Defects ◽

Rapid Development ◽

Magnetic Flux Leakage ◽

Detection Accuracy ◽

Physical Experiments ◽

Detection Technology ◽

Element Simulation ◽

Lift Off ◽

Flux Leakage

With the rapid development of the world’s railways, rail is vital to ensure the safety of rail transit. This article focuses on the magnetic flux leakage (MFL) non-destructive detection technology of the surface defects in railhead. A Multi-sensors method is proposed. The main sensor and four auxiliary sensors are arranged in the detection direction. Firstly, the root mean square (RMS) of the x-component of the main sensor signal is calculated. In the data more significant than the threshold, the defects are determined by the relative values of the sensors signal. The optimal distances among these sensors are calculated to the size of a defect and the lift-off. From the finite element simulation and physical experiments, it is shown that this method can effectively suppress vibration interference and improve the detection accuracy of defects.

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Experimental Study of the Influencing Factors of Elevator Cable Magnetic Flux Leakage Detection Signal

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.711.327 ◽

2013 ◽

Vol 711 ◽

pp. 327-332

Author(s):

Yi Su ◽

Zhen Zhang ◽

Tao Zhang ◽

Ming Li Yang ◽

Mei Lin ◽

...

Keyword(s):

Magnetic Flux ◽

Magnetic Flux Leakage ◽

Probe Design ◽

Détection Signal ◽

Detection Mechanism ◽

Fracture Width ◽

Lift Off ◽

Elevator Cable ◽

Flux Leakage ◽

Detection Signal

The detection mechanism of Magnetic Flux Leakage (MFL) Method of elevator cable is proposed. Using Gauss-Mercury method to analyze the influence of different factors that lift-off value, fracture width, broken wires number and diameter and depth all that based on the collecting experimental system of MFL signals. The method can be used to optimize the detection probe design and detection signal processing.

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Practical evaluation of velocity effects on the magnetic flux leakage technique for storage tank inspection

Insight - Non-Destructive Testing and Condition Monitoring ◽

10.1784/insi.2020.62.2.73 ◽

2020 ◽

Vol 62 (2) ◽

pp. 73-80

Author(s):

A L Pullen ◽

P C Charlton ◽

N R Pearson ◽

N J Whitehead

Keyword(s):

Magnetic Flux ◽

Storage Tank ◽

Eddy Currents ◽

Surface Defects ◽

Signal Amplitude ◽

Magnetic Flux Leakage ◽

Scanning Velocity ◽

Near Surface ◽

Practical Evaluation ◽

Flux Leakage

Magnetic flux leakage (MFL) is a technique commonly used to inspect storage tank floors. This paper describes a practical evaluation of the effect of scanning velocity on defect detection in mild steel plates with thicknesses of 6 mm, 12 mm and 16 mm using a fixed permanent magnetic yoke. Each plate includes four semi-spherical defects ranging from 20% to 80% through-wall thickness. It was found that scanning velocity has a direct effect on defect characterisation due to the distorted magnetic field resulting from induced eddy currents that affect the MFL signal amplitude. This occurs when the inspection velocity is increased and a reduction in the MFL signal amplitudes is observed for far-surface defects. The opposite applies for the top surface, where an increase is seen for near-surface MFL amplitudes when there is insufficient flux saturating the inspection material due to the concentration of induced flux near the top surface. These findings suggest that procedures should be altered to minimise these effects based on inspection requirements. For thicker plates and when far-surface defects are of interest, inspection speeds should be reduced. If only near-surface defects are being considered then increased speeds can be used, provided that the sensor range is sufficient to cope with the increased signal amplitudes so that signal clipping does not become an issue.

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A Lift-Off-Tolerant Magnetic Flux Leakage Testing Method for Drill Pipes at Wellhead

Sensors ◽

10.3390/s17010201 ◽

2017 ◽

Vol 17 (12) ◽

pp. 201 ◽

Cited By ~ 12

Author(s):

Jianbo Wu ◽

Hui Fang ◽

Long Li ◽

Jie Wang ◽

Xiaoming Huang ◽

...

Keyword(s):

Magnetic Flux ◽

Magnetic Flux Leakage ◽

Testing Method ◽

Drill Pipes ◽

Lift Off ◽

Flux Leakage ◽

Magnetic Flux Leakage Testing

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Analysis and Design of a New Linear Vibration Motor Used to Reduce Magnetic Flux Leakage in In-Vehicle Infotainment

Applied Sciences ◽

10.3390/app10103370 ◽

2020 ◽

Vol 10 (10) ◽

pp. 3370 ◽

Cited By ~ 1

Author(s):

Zhi-Xiong Jiang ◽

Ki-Hong Park ◽

Jun-Hyung Kim ◽

Yuan-Wu Jiang ◽

Dan-Ping Xu ◽

...

Keyword(s):

Finite Element Method ◽

Finite Element ◽

Magnetic Flux ◽

Cardiac Pacemaker ◽

Experimental Results ◽

Magnetic Flux Leakage ◽

Linear Vibration ◽

Analysis And Design ◽

Flux Leakage ◽

Element Method

Linear vibration motors are becoming more popular for use in haptic applications owing to their better performance. However, a permanent magnet with a large volume causes massive magnetic flux leakage, which can be harmful to passengers with a cardiac pacemaker or an implantable-cardioverter defibrillator. The magnetic flux leakage is calculated using the 3D finite element method, which can also be applied to obtain the force factor. Then, the displacement and impedance are obtained to check the performance of the linear vibration motor by utilizing the finite element method. A prototype of a linear vibration motor is analyzed and verified based on the experimental results. Based on the analysis methods, three new designs are proposed to reduce the magnetic flux leakage to within 50 G. The final design shows a 93.07% reduction of the magnetic flux leakage while maintaining the same performance as the prototype. To verify the validity of the analysis results, three experimental results were obtained: the magnetic flux leakage, displacement, and impedance. The experimental results are in good agreement with the analysis results.

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Analytical approach for fast computation of magnetic flux leakage due to surface defects

INTERMAG Asia 2005. Digests of the IEEE International Magnetics Conference, 2005. ◽

10.1109/intmag.2005.1464012 ◽

2005 ◽

Cited By ~ 3

Author(s):

Y. Melikhov ◽

S.J. Lee ◽

D.C. Jiles ◽

R. Lopez ◽

L. Brasche

Keyword(s):

Magnetic Flux ◽

Analytical Approach ◽

Surface Defects ◽

Magnetic Flux Leakage ◽

Fast Computation ◽

Flux Leakage

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A novel magnetic flux leakage method based on the ferromagnetic lift-off layer with through groove

Sensors and Actuators A Physical ◽

10.1016/j.sna.2021.113091 ◽

2021 ◽

Vol 332 ◽

pp. 113091

Author(s):

Jian Tang ◽

Rongbiao Wang ◽

Bocheng Liu ◽

Yihua Kang

Keyword(s):

Magnetic Flux ◽

Magnetic Flux Leakage ◽

Lift Off ◽

Flux Leakage

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Optimising sensor pitch for magnetic flux leakage imaging systems

Insight - Non-Destructive Testing and Condition Monitoring ◽

10.1784/insi.2021.63.7.416 ◽

2021 ◽

Vol 63 (7) ◽

pp. 416-421

Author(s):

R Murshudov ◽

J M Watson ◽

C W Liang ◽

J Sexton ◽

M Missous

Keyword(s):

Magnetic Flux ◽

Imaging System ◽

Sensor Arrays ◽

Magnetic Sensors ◽

Magnetic Flux Leakage ◽

Step Size ◽

Optimal Spacing ◽

Minimum Number ◽

Lift Off ◽

Flux Leakage

Sensor arrays can significantly increase the speed at which inspections and subsequent imaging of flaws is performed[1]. This work focuses on developing a software approach for optimising the spacing between quantum well Hall-effect (QWHE) magnetic sensors used for magnetic flux leakage (MFL) imaging, where this approach could be adapted for any non-destructive evaluation (NDE) technique in which imaging is obtained. A ground mild steel weld sample containing two surface-breaking flaws prepared by Sonaspection was scanned using an XYZ MFL imaging system developed at the University of Manchester[2,3,13,14]. The scan was taken with an autonomously controlled lift-off height of 0.75 mm, with an x-y measurement step of 100 μm and an applied magnetic field of 30 mT root mean square (RMS) at a frequency of 400 Hz. This data (ie magnetic image) was then processed to simulate different measurement step sizes, to determine any relationship between step size and flaw detectability (flaw signal to weld background response). This work effectively simulates different sensor pitches (separation between sensors) of integrated QWHE sensor arrays from 100 μm to 5 mm, with the goal of determining both the minimum number of sensors required in the array and the optimal spacing to maximise scan speeds and help determine optimum inspection parameters to develop the technology of low-power MFL imaging. This optimisation process could be applied to any NDE imaging system (electromagnetic or other) currently used, with results dependent on the inspection parameters.

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