scholarly journals Tensor Based Finite Element Model for the Calculation of Leakage Field in Magnetic Flux Leakage Testing

2020 ◽  
Author(s):  
Fred John Alimey ◽  
Libing Bai ◽  
Yuhua Cheng
Keyword(s):  
Magnetic Flux ◽  
Surface Defects ◽  
Element Model ◽  
Single Equation ◽  
Magnetic Flux Leakage ◽  
Leakage Field ◽  
Proposed Model ◽  
Defect Area ◽  
Mathematical Operations ◽  
Flux Leakage

Magnetic flux leakage (MFL) testing is a widely used electromagnetic nondestructive testing (ENDT) method, which has the ability to detect both surface and sub-surface defects in conductive materials. One of its best features is its ability to mathematically model field leakage from the defect area in a magnetized material. In this paper, we propose an optimized FEM model using geometrical weighted tensor (TBFEM), for the calculation of leakage field in MFL. This model using the Einstein’s convention eliminates the bulky nature of traditional FEM based on its matrix algebra formation allowing for easy implementation and fast calculations. The proposed model achieves this by reducing the set of matrix equations into a single equation using suffixes which can then be solved with regular mathematical operations.

Finite Element Analysis and Research on Corrosion Defect of Tank Floor

2016 ◽  
Vol 853 ◽  
pp. 514-518
Author(s):  
Zhi Jun Yang ◽  
De Shu Chen ◽  
Liang Chen ◽  
Yu Zhuo Liu ◽  
Ran An ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Finite Element ◽  
Magnetic Flux ◽  
Magnetic Flux Leakage ◽  
Bottom Plate ◽  
Element Analysis ◽  
Corrosion Defect ◽  
Leakage Magnetic Field ◽  
Leakage Field ◽  
Flux Leakage

Storage tank is an essential vessel in petrochemical industry, and the corrosion of tank is an important reason for the safety hazard. The corrosion of tank bottom plate is more serious than the tank wall, and it is not easy to check and repair, when damaged to a certain extent it will cause the leakage of the media, then lead to waste of energy, environmental pollution, at the same time it will cause a major accident. Magnetic flux leakage testing is widely used in the field of tank floor inspection with the advantages of fast scanning speed, accurate results and so on. In this paper, the finite element simulation and analysis of the corrosion defect leakage magnetic field is used to obtain the data, and the characteristic of the leakage magnetic field is extracted. The effect of defect depth and width and shape on the magnetic flux leakage field is studied, and the distribution curve of the magnetic flux leakage field is obtained.

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

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.

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

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.

Numerical Simulation and Experimental Research on Crack Magnetic Flux Leakage Field

2011 ◽  
Author(s):  
Fujun Liu ◽  
Mulin Zheng ◽  
Shuai Kong ◽  
Zhangwei Ling ◽  
Yueqiang Qian
Keyword(s):  
Numerical Simulation ◽  
Magnetic Flux ◽  
Experimental Research ◽  
Inclination Angle ◽  
Three Dimensional ◽  
Magnetic Flux Leakage ◽  
Experimental Investigations ◽  
Leakage Field ◽  
Three Dimensional Models ◽  
Flux Leakage

Magnetic flux leakage (MFL) testing is widely used to inspect and characterize defects in pipelines, storage tanks and other structures. In this paper, based on the Maxwell Equations, numerical simulation and experimental research of crack magnetic flux leakage field were carried out. The three-dimensional models of cracks were established, the influence of the generalized crack parameters to the magnetostatic MFL field, including depth, width, inclination angle and crack spacing, was discussed. The relationship between defect parameters and MFL amplitude was obtained. The amplitude is significantly affected by the inclination angle. Therefore, single direction inspection may lead to undetected in practice. While the two cracks interval is less than 5 mm, the MFL fields would overlap. Furthermore, the experimental investigations were developed, and the results agree well with that of the simulation. The conclusions could provide valuable reference for inspection.

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

2016 ◽  
Vol 16 (1) ◽  
pp. 8-13 ◽  
Author(s):  
V. Suresh ◽  
A. Abudhahir
Keyword(s):  
Magnetic Flux ◽  
Analytical Model ◽  
Surface Defects ◽  
Experimental Results ◽  
Magnetic Flux Leakage ◽  
Analytical Expression ◽  
Cylindrical Holes ◽  
Lift Off ◽  
Flux Leakage ◽  
Good Agreement

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.

scholarly journals Investigation of and Components of the Magnetic Flux Leakage in Ferromagnetic Laminated Sample

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Mustafa Göktepe
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Crack Detection ◽  
Industrial Applications ◽  
Magnetic Flux Leakage ◽  
Longitudinal Magnetization ◽  
Flux Lines ◽  
Power Stations ◽  
Leakage Field ◽  
Flux Leakage

The magnetic flux leakage (MFL) technique is most commonly used for crack detection from iron bars, laminated sheets, and steel tubes of ferromagnetic nature. Magnetic flux leakage system induces a magnetic field and detects magnetic flux lines that “leak” or change because of a discontinuity in the magnetized area. An inductive coil sensor or a Hall effect sensor detects the leakage. Magnetic methods of nondestructive testing (NDT) depend on detecting this magnetic flux leakage field. The ferromagnetic specimen is magnetized by suitable methods, and flaws which break the surface or just the subsurface distort the magnetic field, causing local flux leakage fields. It is very important for industrial applications to detect cracks and flaws in metal parts of the steel bridges, power stations, military tools and structures, and so forth. In this study, the inspection of cracks in laminated sheets under longitudinal magnetization will be discussed in detail.

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