A sensor measuring the Fourier coefficients of the magnetic flux density for pipe crack detection using the magnetic flux leakage method

2011 ◽  
Vol 109 (7) ◽  
pp. 07E305 ◽  
Author(s):  
T. Nara ◽  
Y. Takanashi ◽  
M. Mizuide
Keyword(s):  
Magnetic Flux ◽  
Flux Density ◽  
Crack Detection ◽  
Fourier Coefficients ◽  
Magnetic Flux Leakage ◽  
Magnetic Flux Density ◽  
Flux Leakage

Numerical Simulation and Analysis on Magnetizing Exciter for Magnetic Flux Leakage

2011 ◽  
Vol 474-476 ◽  
pp. 1187-1190
Author(s):  
Qiang Song
Keyword(s):  
Magnetic Flux ◽  
Permanent Magnet ◽  
Flux Density ◽  
Pipe Wall ◽  
Three Dimensional ◽  
Magnetic Flux Leakage ◽  
Magnetic Flux Density ◽  
Outer Diameter ◽  
Element Analysis ◽  
Flux Leakage

Magnetic flux leakage (MFL) is a non-destructive testing method used to inspect the pipe and magnetization of the pipe wall to saturation is essential for anomalies to be reliably and accurately detected and characterized. Axial components of magnetic flux density obtained during the MFL inspection have been simulated using three-dimensional finite element analysis and the effects of magnetizing exciter parameters on magnetic flux density are investigated. The pipe modeled in this paper has an outer diameter of 127mm (5 in.) with a wall thickness of 9 mm (0.354 in.). According to numerical simulations, an increase in the magnetic flux density of pipe wall is observed with an increase in the permanent magnet length and height. It clearly illustrates that Nd-Fe-B permanent magnet assembly with 70 mm length and 40 mm height may magnetize pipe wall to near saturation.

Magnetic Flux Leakage Sensing-Based Steel Cable NDE Technique Incorporated on a Cable Climbing Robot for Bridge Structures

2012 ◽  
Vol 83 ◽  
pp. 217-222 ◽  
Author(s):  
Seung Hee Park ◽  
Ju Won Kim ◽  
Min Jun Nam ◽  
Jong Jae Lee
Keyword(s):  
Magnetic Flux ◽  
Magnetic Flux Leakage ◽  
Magnetic Flux Density ◽  
Inspection System ◽  
Climbing Robot ◽  
Steel Cable ◽  
Monitoring Method ◽  
Sensor Head ◽  
Bridge Structures ◽  
Flux Leakage

In this study, an automated cable monitoring system using a NDE technique and a cable climbing robot is proposed. MFL (Magnetic Flux Leakage- based inspection system was applied to monitor the condition of cables. This inspection system measures magnetic flux to detect the local faults (LF) of steel cable. To verify the feasibility of the proposed damage detection technique, an 8-channel MFL sensor head prototype was designed and fabricated. A steel cable bunch specimen with several types of damage was fabricated and scanned by the MFL sensor head to measure the magnetic flux density of the specimen. To interpret the condition of the steel cable, magnetic flux signals were used to determine the locations of the flaws and the level of damage. Measured signals from the damaged specimen were compared with thresholds set for objective decision making. In addition, the measured magnetic flux signal was visualized into a 3D MFL map for convenient cable monitoring. Finally, the results were compared with information on actual inflicted damages to confirm the accuracy and effectiveness of the proposed cable monitoring method.

scholarly journals Pulsed magnetic flux leakage method for hairline crack detection and characterization

AIP Advances ◽  
2018 ◽  
Vol 8 (4) ◽  
pp. 047207 ◽  
Author(s):  
Chukwunonso K. Okolo ◽  
Turgut Meydan
Keyword(s):  
Magnetic Flux ◽  
Crack Detection ◽  
Magnetic Flux Leakage ◽  
Flux Leakage

scholarly journals Magnetic field gradient as the most useful signal for detection of flaws using MFL technique

2018 ◽  
Vol 69 (6) ◽  
pp. 422-425 ◽  
Author(s):  
Zbigniew Usarek ◽  
Marek Chmielewski ◽  
Leszek Piotrowski
Keyword(s):  
Magnetic Flux ◽  
Steel Plate ◽  
Magnetic Field Gradient ◽  
Normal Component ◽  
Magnetic Flux Leakage ◽  
Magnetic Flux Density ◽  
Scanning Velocity ◽  
Useful Signal ◽  
Flux Leakage ◽  
Proper Analysis

Abstract The magnetic flux leakage (MFL) technique is extensively used for detection of flaws as well as for evaluation of their dimensions in ferromagnetic materials. However, proper analysis of the MFL signal is hindered by the MFL sensor velocity causing distortions of this signal. Traditionally measured components of the MFL signal are particularly sensitive to the scanning velocity. In this paper, an another signal – the gradient of the normal component of magnetic flux density – was proposed as it is less sensitive to the scanning velocity. Results obtained for scans of the steel plate with artificially manufactured flaws confirm this statement.

Magnetizing Method for High Precision MFL Inspection of Longitudinal Defects of Thick Wall Steel Pipe

2013 ◽  
Vol 718-720 ◽  
pp. 898-902 ◽  
Author(s):  
Bo Feng ◽  
Jian Bo Wu ◽  
Yun Yang ◽  
Yi Hua Kang
Keyword(s):  
Magnetic Flux ◽  
High Precision ◽  
Magnetic Sensors ◽  
Magnetic Flux Leakage ◽  
Steel Pipe ◽  
Thick Wall ◽  
Magnetic Flux Density ◽  
Detection Zone ◽  
Flux Leakage ◽  
Magnetic Flux Leakage Testing

Circumferential magnetization of the thick wall steel pipe is carried out for the inspection of longitudinal defects in magnetic flux leakage testing. For high precision magnetic flux leakage testing, magnetic field distribution along the axial direction must be uniform, thus a new type of pole shoe structure is proposed in this paper to enlarge the uniformly magnetized area. Thick wall steel pipes are hard to be magnetized to near saturation, especially when the new pole shoe is used, which makes difficult for the magnetic sensors to pick up the magnetic leakage field. Therefore, the relationship between the magnetic flux density of the detection zone and the dimensions of the magnetizer has been studied by finite element simulation. These results are helpful in the design of circumferential magnetizer.

scholarly journals Magnetic Flux Leakage Sensing-Based Steel Cable NDE Technique

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Seunghee Park ◽  
Ju-Won Kim ◽  
Changgil Lee ◽  
Jong-Jae Lee
Keyword(s):  
Magnetic Flux ◽  
Magnetic Flux Leakage ◽  
Magnetic Flux Density ◽  
Inspection System ◽  
Steel Cable ◽  
Monitoring Method ◽  
Sensor Head ◽  
Long Span Bridges ◽  
Long Span ◽  
Flux Leakage

Nondestructive evaluation (NDE) of steel cables in long span bridges is necessary to prevent structural failure. Thus, an automated cable monitoring system is proposed that uses a suitable NDE technique and a cable-climbing robot. A magnetic flux leakage- (MFL-) based inspection system was applied to monitor the condition of cables. This inspection system measures magnetic flux to detect the local faults (LF) of steel cable. To verify the feasibility of the proposed damage detection technique, an 8-channel MFL sensor head prototype was designed and fabricated. A steel cable bunch specimen with several types of damage was fabricated and scanned by the MFL sensor head to measure the magnetic flux density of the specimen. To interpret the condition of the steel cable, magnetic flux signals were used to determine the locations of the flaws and the levels of damage. Measured signals from the damaged specimen were compared with thresholds that were set for objective decision-making. In addition, the measured magnetic flux signals were visualized as a 3D MFL map for intuitive cable monitoring. Finally, the results were compared with information on actual inflicted damages, to confirm the accuracy and effectiveness of the proposed cable monitoring method.

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.

Magnetic flux leakage–based local damage detection and quantification for steel wire rope non-destructive evaluation

2017 ◽  
Vol 29 (17) ◽  
pp. 3396-3410 ◽  
Author(s):  
Ju-Won Kim ◽  
Seunghee Park
Keyword(s):  
Magnetic Flux ◽  
Damage Detection ◽  
Permanent Magnets ◽  
Steel Wire ◽  
Threshold Value ◽  
Wire Rope ◽  
Magnetic Flux Leakage ◽  
Magnetic Flux Density ◽  
Sensor Head ◽  
Flux Leakage

A magnetic flux leakage method was applied to detect damage when inspecting steel wire rope. A multi-channel magnetic flux leakage sensor head was fabricated using Hall sensors and permanent magnets to adapt to the wire rope. Three types of artificial damage were created on a wire rope specimen. The magnetic flux leakage sensor head scanned the damaged specimen to measure the magnetic flux density while the damage was expanding in three steps. Signal processing processes including the enveloping process based on Hilbert transform were performed to clarify the flux leakage signal due to the damage. The enveloped signals were then analyzed for objective damage detection by comparing with the threshold value. For improvement of quantitative analysis, three types of new damage indexes that utilize the relationship between the enveloped magnetic flux leakage signal and the threshold value were additionally proposed. By using the proposed damage indexes and the general damage indexes for the magnetic flux leakage method, the detected magnetic flux leakage signals from each damage type were quantified. The trends of the extracted damage indexes according to damage levels were analyzed to examine the applicability and reliability of the proposed damage indexes for the magnetic flux leakage based wire rope inspection.

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