scholarly journals Detection of Mechanical Damage Using the Magnetic Flux Leakage Technique

2004 ◽  
Author(s):  
Lynann Clapham ◽  
Vijay Babbar ◽  
James Byrne
Keyword(s):  
Magnetic Flux ◽  
Experimental Studies ◽  
Mechanical Damage ◽  
Central Peak ◽  
Magnetic Flux Leakage ◽  
Element Analysis ◽  
Stress Effects ◽  
Stress Relieving ◽  
Stress Dependent ◽  
Flux Leakage

Since magnetism is strongly stress dependent, Magnetic Flux Leakage (MFL) inspection tools have the potential to locate and characterize mechanical damage in pipelines. However, MFL application to mechanical damage detection faces hurdles which make signal interpretation problematic: 1) the MFL signal is a superposition of geometrical and stress effects, 2) the stress distribution around a mechanically damaged region is very complex, consisting of plastic deformation and residual (elastic) stresses, 3) the effect of stress on magnetic behaviour is not well understood. This paper summarizes recent results of experimental and modeling studies of MFL signals resulting from mechanical damage. In experimental studies, mechanical damage was simulated using a tool and die press to produce dents of varying depths in plate samples. Radial component MFL measurements were made before and after selective stress-relieving heat treatments. These annealing treatments enabled the stress and geometry components of the MFL signal to be separated. Geometry and stress effects generate separate MFL peaks — the geometry effects lead to central peak regions while the stress effects produce ‘shoulder’ peaks. In general the geometry peaks tend to scale with depth, while the shoulder peaks remain approximately constant. This implies that deep dents will display a ‘geometry’ signature while shallow or rerounded dents will have a stress signature. Finally, the influence of other parameters such as flux density and topside/bottomside inspection was also quantified. In the finite element analysis work, stress was incorporated by modifying the magnetic permeability in the residual stress regions of the modeled dent. Both stress and geometry contributions to the MFL signal were examined separately. Despite using a number of simplifying assumptions, the modeled results matched the experimental results very closely, and were used to aid in interpretation of the MFL signals.

Understanding Magnetic Flux Leakage Signals From Dents

2006 ◽  
Author(s):  
Lynann Clapham ◽  
Vijay Babbar ◽  
Alex Rubinshteyn
Keyword(s):  
Magnetic Flux ◽  
Pipe Wall ◽  
Experimental Studies ◽  
Mechanical Damage ◽  
Magnetic Behaviour ◽  
Magnetic Flux Leakage ◽  
Element Analysis ◽  
Aspect Ratios ◽  
Stress Relieving ◽  
Flux Leakage

The Magnetic Flux Leakage (MFL) technique is sensitive both to pipe wall geometry and pipe wall stresses, therefore MFL inspection tools have the potential to locate and characterize mechanical damage in pipelines. However, the combined influence of stress and geometry make MFL signal interpretation difficult for a number of reasons: 1) the MFL signal from mechanical damage is a superposition of geometrical and stress effects, 2) the stress distribution around a mechanically damaged region is very complex, consisting of plastic deformation and residual (elastic) stresses, 3) the effect of stress on magnetic behaviour is not well understood. Accurate magnetic models that can incorporate both stress and geometry effects are essential in order to understand MFL signals from dents. This paper reports on work where FEA magnetic modeling is combined with experimental studies to better understand dents from MFL signals. In experimental studies, mechanical damage was simulated using a tool and die press to produce dents of varying aspect ratios (1:1, 2:1, 4:1), orientations (axial, circumferential) and depths (3–8 mm) in plate samples. MFL measurements were made before and after selective stress-relieving heat treatments. These annealing treatments enabled the stress and geometry components of the MFL signal to be separated. Geometry and stress ‘peaks’ tend in most cases to overlap — however stress features are most prominent in the dent rim region and geometry peaks over central region. In general the geometry signal scales directly with depth. The stress scales less significantly with depth. As a result deep dents will display a ‘geometry’ signature while in shallow dents the stress signature will dominate. In the finite element analysis work, stress was incorporated by modifying the magnetic permeability in the residual stress regions of the modeled dent. Both stress and geometry contributions to the MFL signal were examined separately. Despite using a number of simplifying assumptions, the modeled results matched the experimental results very closely, and were used to aid in interpretation of the MFL signals.

scholarly journals Detection of Mechanical Damage Using the Magnetic Flux Leakage Technique

2002 ◽  
Author(s):  
L. Clapham ◽  
Vijay Babbar ◽  
Thana Rahim ◽  
David Atherton
Keyword(s):  
Residual Stress ◽  
Plastic Deformation ◽  
Magnetic Flux ◽  
Mechanical Damage ◽  
Magnetic Behaviour ◽  
Magnetic Flux Leakage ◽  
Stress Effects ◽  
Stress Relieving ◽  
Series Of Experiments ◽  
Flux Leakage

Since magnetism is strongly stress dependent, Magnetic Flux Leakage (MFL) inspection tools have the potential to locate and characterize mechanical damage in pipelines. However, MFL application to mechanical damage detection faces major hurdles, which make signal interpretation problematic: 1) the MFL signal will be a superposition of geometrical and stress effects, 2) the stress distribution around a mechanically damaged region is very complex, consisting of plastic deformation and residual (elastic) stresses, 3) the effect of stress on magnetic behaviour is not well understood. This paper summarizes a number of our studies concerned with mechanical damage and the effects of elastic and plastic deformation on MFL signals. The first series of experiments was conducted using uniaxial loading into the plastic deformation regime. Magnetic measurements made in situ with this uniaxial deformation showed that magnetic behaviour is far more sensitive to elastic, compared to plastic, deformation. Unloading the samples resulted in a combination of plastic deformation and residual stress. Subsequent ‘staged’ stress relieving heat treatments enabled us to progressively remove the residual stresses, and characterize their effects on magnetic behaviour and MFL signals. In a second series of experiments we simulated mechanical damage using a tool and die press to progressively ‘dent’ a number of plate samples. As with true mechanical damage, the resulting MFL signals arise from both geometrical and residual stress effects. Subsequent stress relieving heat treatments were used to separate and compare the ‘geometrical’ MFL signal from the ‘residual stress’ MFL signal.

Modelling Magnetic Flux Leakage Signals From Dents

2008 ◽  
Author(s):  
Lynann Clapham ◽  
Vijay Babbar ◽  
Kris Marble ◽  
Alex Rubinshteyn ◽  
Mures Zarea
Keyword(s):  
Magnetic Flux ◽  
Pipe Wall ◽  
Mechanical Damage ◽  
Magnetic Behaviour ◽  
Magnetic Flux Leakage ◽  
Element Analysis ◽  
The Past ◽  
Fea Modeling ◽  
Flux Leakage ◽  
Wall Geometry

The Magnetic Flux Leakage (MFL) technique is sensitive both to pipe wall geometry and pipe wall strain, therefore MFL inspection tools have the potential to locate and characterize mechanical damage in pipelines. However, the combined influence of strain and geometry makes MFL signals from dents and gouges difficult to interpret for a number of reasons: 1) the MFL signal from mechanical damage is a superposition of geometrical and strain effects, 2) the strain distribution around a mechanically damaged region can be very complex, often consisting of plastic deformation and residual (elastic) strain, 3) the effect of strain on magnetic behaviour is not well understood. Accurate magnetic models that can incorporate both strain and geometry effects are essential in order to understand MFL signals from mechanical damage. This paper reviews work conducted over the past few years involving magnetic finite element analysis (FEA) modeling of MFL dent signals and comparison with experimental results obtained both from laboratory-dented samples and dented pipe sections.

Finite Element Analysis and Experimental Research for Horizontal Tank to Internal Magnetic Flux Leakage Detection

2014 ◽  
Vol 599-601 ◽  
pp. 321-325
Author(s):  
Li Qiang Sun ◽  
Hong Bo Zhu ◽  
Ming Xie ◽  
Ji Xia Li
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Magnetic Flux ◽  
Magnetic Flux Leakage ◽  
Leakage Detection ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Horizontal Tank ◽  
Flux Leakage ◽  
Detection Effect

In view of the petroleum and petrochemical characteristics of horizontal tank, ANSYS software of finite element analysis was carried out on the horizontal tank within the magnetic flux leakage testing, analyzes the influencing factors of defect magnetic flux leakage signals. Experiments verify the finite element analysis results, the experimental results show that the research of horizontal tank within the magnetic flux leakage detection effect is obvious.

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.

Numerical Simulation Study of Stress-Magnetization Effect on Different Notch Steel Specimens

2014 ◽  
Vol 989-994 ◽  
pp. 891-897 ◽  
Author(s):  
Xiao Wen Xi ◽  
Shang Kun Ren ◽  
Yin Huang
Keyword(s):  
Magnetic Flux ◽  
Quantitative Research ◽  
Tensile Load ◽  
Magnetic Flux Leakage ◽  
Magnetic Memory ◽  
Metal Magnetic Memory ◽  
Element Analysis ◽  
Damage Degree ◽  
Testing Technology ◽  
Flux Leakage

To study the mechanism of metal magnetic memory (MMM) testing technology, the stress-magnetization effect on 20 steel specimens with different notch angles under exercise of the geomagnetic field and tensile load is simulated by using the finite element analysis (FEA) software ANSYS. With the stimulation, the stress and magnetic flux leakage distribution of the specimens is given. The results showed that internal stress distribution of different notch specimens under external tensile effects is different; The curves of relationship between damage degree of stress concentration and the distribution of magnetic flux leakage is also related to the defect shape and structure; Magnetization decreases with increases of stress at first and then increases with continuing increase of stress, which is called stress magnetization reversal. It provides an important reference for the quantitative research of metal magnetic memory technology.

Finite Element Analysis on Magnetic Flux Leakage of Interior Permanent Magnet Generator for Vehicle

2011 ◽  
Vol 66-68 ◽  
pp. 483-488 ◽  
Author(s):  
Xue Yi Zhang ◽  
Hong Bin Yin ◽  
Li Wei Shi
Keyword(s):  
Finite Element ◽  
Magnetic Flux ◽  
Permanent Magnet ◽  
Structural Design ◽  
Magnetic Flux Leakage ◽  
The Finite Element Method ◽  
Element Analysis ◽  
Interior Permanent Magnet ◽  
Leakage Coefficient ◽  
Flux Leakage

In order to solve the problem that no-load magnetic flux leakage coefficient is not accurate when it is calculated by the method of magnetic circuit, a model of interior permanent magnet(IPM) generator with 36 slots for vehicle was built through the finite element method of the ANSYS, and then a means of calculating the IPM generator’s magnetic flux was put forward after analyzing the magnetic flux leakage conditions of different rotor structures under the circumstance of not changing stator structure. The ralationships among the pairs of poles, the magnet width, the thickness of non-magnetic sleeve, the length of air-gap and the magnetic flux leakage coefficient were obtained, and they provided forceful guidance for the structural design of IPM generator.

Management of Pipeline Dents and Mechanical Damage in Gas Pipelines

2006 ◽  
Author(s):  
David J. Warman ◽  
Dennis Johnston ◽  
John D. Mackenzie ◽  
Steve Rapp ◽  
Bob Travers
Keyword(s):  
High Resolution ◽  
Magnetic Flux ◽  
Mechanical Damage ◽  
Management Plan ◽  
Magnetic Flux Leakage ◽  
Pipeline System ◽  
Channel Geometry ◽  
Channel Deformation ◽  
Integrity Management ◽  
Flux Leakage

This paper describes an approach used by Duke Energy Gas Transmission (DEGT) to manage dents and mechanical damage as part of its overall Integrity Management Plan (IMP). The approach provides guidance in the process for evaluating deformation anomalies that are detected by high resolution magnetic flux leakage (HR-MFL) and multi-channel geometry in-line inspection tools, the process to determine which deformations will be selected for excavation, the process to conduct pipeline field excavations, assessments, and repairs for pipeline integrity purposes. This approach was developed, tested and fully implemented during pipeline integrity work over a two year program involving over 1,100 miles of HR-MFL and 900 miles of geometry in-line inspection. Integration of data from high resolution ILI tools (HR-MFL and multi-channel deformation tools) was used to identify and characterize dents and mechanical damage in the pipeline system. From subsequent field assessments and correlation with ILI results, the processes were refined and field procedures developed. The new guidance provided in the 2003 edition of ASME B31.8 was used as the governing assessment criteria.

Finite Element Analysis of Magnetization Reversal Effect Based on Ferromagnetic Specimens

2014 ◽  
Vol 620 ◽  
pp. 127-132
Author(s):  
Xiao Wen Xi ◽  
Shang Kun Ren ◽  
Li Hua Yuan
Keyword(s):  
Magnetic Field ◽  
Finite Element Analysis ◽  
Finite Element ◽  
Magnetic Flux ◽  
Magnetization Reversal ◽  
Tensile Load ◽  
Magnetic Flux Leakage ◽  
Element Analysis ◽  
The Magnetic Field ◽  
Flux Leakage

Using large finite element analysis (FEA) software ANSYS, the stress-magnetization effect on 20# steel specimens with different shape notches is simulated under the geomagnetic field and tensile load. With the stimulation, the magnetic flux leakage fields at certain positions of the surface specimen were measured. Through analysis the relationship between the magnetic flux leakage fields of certain points with tensile stress, the results showed that the magnetic field value at certain positions of specimen surface first decreases and then increases along with the increase of stress, which is called magnetization reversal phenomenon; Different gaps and different positions of the specimen show different magnetization reversal rules; By measuring the maximal variation of the magnetic field value △Hmax at certain positions of the surface specimen and by analyzing its change law, we can roughly estimate specimen stress size and distribution regularity of stress. Moreover, this article also discusses the effect of lifts-off of the probe on the law of stress magnetization.

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