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Low Frequency Eddy Current Testing for Subsurface Cracks in Aluminum Aircraft Supports
N. Alatawneh, P.R. Underhill, and T.W. Krause
Department of Physics, Royal Military College of Canada, Kingston, ON, K7K 7B4
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Outline 2
Introduction Problem definition Probe design Simulation Results Experimental Results Conclusion and Future work
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Introduction 3
Location of CF-188 Stub Flanges on the CF-188 Fighter Jet.
Inspection Surface
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Test Samples - Eyebrow Crack 4
A=0.4”, 0.5”, 0.6”
B= 3/8” RC= 0.288” Crack height= 0.15”
0o
-90o
90o
0.15”
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Scanning Probe
5
Drive coil
Differential pick-up coils
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Problem Definition 6
Slanted sample
EC probe
Bolt
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Proposed Solution 7
Sample
Scanning probe
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FEM Modeling Using COMSOL
8
Challenges Build the 3D geometry Meshing Material parameters
Bolt Driver Cone Coil
Pick up Coils
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Horizontal Sample VS Slanted Sample
9
-0.0005
0
0.0005
0.001
0.0015
0.002
0.0025
-0.0002 0.0002 0.0006 0.001
Imag
. (V
)
Real (V)
No crack with 5 deg. slope surface No crack in horizontal sample
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The Response as a Function of Sample Thickness
10
-0.0005
0
0.0005
0.001
0.0015
0.002
0.0025
0.003
0.0035
0.004
0.0045
-0.0005 0 0.0005 0.001 0.0015 0.002 0.0025 0.003 0.0035
Imag. (V
)
Real (V)
NC_500Hz_5deg_0.25"thick
NC_1000Hz_5deg_0.25"thick
NC_500Hz_5deg_0.35"thick
NC_1000Hz_5deg_0.35"thick
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The Response as a Function of Sample Slope
11
0
0.0005
0.001
0.0015
0.002
0.0025
0 0.0002 0.0004 0.0006 0.0008 0.001 0.0012
Imag. (V
)
Real (V)
500 Hz_NO crack_ 0.25"_thickness_without edge
1 degree
3 degrees
5 degrees
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The Response as a Function of Sample Slope
12
0
0.0005
0.001
0.0015
0.002
0.0025
0.003
0.0035
0.004
0 0.0005 0.001 0.0015 0.002 0.0025 0.003
Imag. (V
)
Real (V)
1000 Hz_NO crack_ 0.25"_thickness_without edge
1 degree
3 degrees
5 degrees
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Different Crack Heights for rounded edge sample at 1 kHz
13
Ch
-0.001
0
0.001
0.002
0.003
0.004
0.005
0 0.001 0.002 0.003 0.004 0.005
Imag
. (V
)
Real (V)
0.13" 0.15" 0.17"
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FEM modeling of edge effect 14
NO Edge Edge 1 Edge 2
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Edge Effect Without a Crack at 1 kHz for height of 0.15”
15
NO
Edge1
Edge2
-0.001
0
0.001
0.002
0.003
0.004
-0.001 0 0.001 0.002 0.003 0.004
Imag
. (V
)
Real (V)
Round edge
Sharp edge
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Measurements 16
0o -90o 90o
NORTEC 600 D
Real Sample
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Measurements 17
NO crack, 0.15”, rounded edge, 1000 Hz, 60 dB
0.6” crack, 0.15”, height, rounded edge, 1000 Hz, 60 dB
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Measurements 18
NO crack, 0.15”, rounded edge, 200 Hz, 60 dB
0.6” crack, 0.15”, height, rounded edge, 200 Hz, 60 dB
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Conclusions 19
Simulations were performed to give information about different geometries and conditions
Experimental measurements demonstrate ability to size crack in terms of depth and length
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Future work 20
Refine probe (make thinner, use spherical washer)
Develop eye brow probe
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21
Thank you!