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Surface Open Corrosive Wall Thinning Effects Isabel Cristina Pérez Blanco Gerd Dobmann Research Institute of Corrosion (Colombia) Fraunhofer Institute of Nondestructive Testing (Germany) 1
Surface Open Corrosive Wall Thinning Effects
Isabel Cristina Pérez Blanco Gerd Dobmann
Research Institute of Corrosion (Colombia)
Fraunhofer Institute of Nondestructive Testing (Germany)
1
• MFL Principle and In-Line Tools
• Corrosive defects Approximation
• Comparison between 3D and 2D Simulation Results
• Conclusions
2
Outline
3
MFL Principle
N
S
S
N
Test specimen Test specimen
with flaw
Magnets
Magnetizing yoke
Sensor N
S
S
N Sensor
Magnetic Flux
Magnetic
Leakage Flux
4
MFL Principle
Hn Ht
Normal and tangential magnetic field components of the leakage signal
Hinc
5
In‐Line Inspection Tools
MFL Tools (axial)
High Resolution MFL-tool
from C-Pig
(Foto C-Pig)
High Resolution
MFL-tool from GE-PII
(Foto GE-PII)
6
In‐Line Inspection Tools
Design of intelligent pigs
Propulsion
Sensor carrier
Data Recording IDOD-Sensors
Battery section
Odometer-wheels
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Corrosive Defects Approximation
Name Defects depth [%]
Plate height [mm]
Plate width [mm]
Plate length [mm]
TK 10-05 0.5
10
120 500
TK 10-30 30
TK 10-70 70
TK 15-05 0.5
15 TK 15-30 30
TK 15-70 70
TK 20-05 0.5
20 TK 20-30 30
TK 20-70 70
Specimen TK 10-70
10 mm thick
70% defect depth
Set of specimens
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Corrosive Defects Approximation
Magnetic field components at 1 mm lift-off in TK 10-70:
Tangential Circumferential Normal
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Corrosive Defects Approximation
TK 10-70
External defects
Simulation Experiment
TK 10-70
Internal defects
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Corrosive Defects Approximation
0
0.5
1
1.5
2
2.5
3
0 5 10 15 20 25
Hz
p-p
no
rm.
[A/m
]
Defect Radius [mm]
Simulation
Experiment
Linear (Simulation)
Linear (Experiment)
Comparison between simulated and experiment results
for specimen TK 10-70
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Corrosive Defects Approximation
D1
D2
Distance between defects in
test specimen
-1500
-1000
-500
0
500
1000
1500
-200 -150 -100 -50 0 50 100 150 200
Hz
[A/m
] Position [mm]
D1=50mm D1=100mm
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Corrosive Defects Approximation
Influence of adjacent defects (D > 2L)
3D Simulation
0
500
1000
1500
2000
2500
3000
0 20 40 60 80 100
Hz
p-p
[A
/m]
Distance between defects [mm] -1500
-1000
-500
0
500
1000
1500
-200 -100 0 100 200 Hz
[A/m
]
Position [mm]
D=20mm
R= 5 mm
R= 7.5 mm
R= 15 mm
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Corrosive Defects Approximation
Defect Radius = 3 mm
3D simulation
0
200
400
600
800
1000
1200
1400
1600
1800
2000
0 20 40 60 80 100
Hz
p-p
[A
/m]
Defect Depth [%]
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Corrosive Defects Approximation
Analysed parameters:
• Magnetic field signal components
• Intern and extern signals
• Influence of adjacent defects
• Radius vs. depth in defect
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Comparison between 3D and 2D simulation
Tangential
component
Normal
component
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Comparison between 3D and 2D simulation
External defects Internal defects
2D simulation
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Comparison between 3D and 2D simulation
0
500
1000
1500
2000
2500
3000
3500
4000
0 20 40 60 80 100
Hz
p-p
[A
/m]
Distance between defects [mm]
R= 5 mm
R= 7.5 mm
R= 15 mm
Influence of adjacent defects (D > 2L)
2D simulation
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Comparison between 3D and 2D simulation
Defect
Superposition
D = 10 mm
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Comparison between 3D and 2D simulation
Defect Radius = 3 mm
2D simulation
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
0 20 40 60 80 100
Hz
p-p
[A
/m]
Defect depth [%]
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Conclusions
• 2D simulation is accurate enough to interpret MFL signals obtained from corrosion defects and subsequently allow the defect reconstruction.
• Selection of an ideal mesh resolution and suitable boundary conditions are essential to guarantee accurate numerical results.
• Besides time and computational cost savings, obtained signals in 2D are smoother as 3D signals.
• A mathematical model should be develop to take into account the influence of the third component in the signal amplitude of the results in 2D.
• Further research is needed for irregular defects.
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Thank you for your attention !
Questions?
