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

Introduction 3

Location of CF-188 Stub Flanges on the CF-188 Fighter Jet.

Inspection Surface

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”

Scanning Probe

5

Drive coil

Differential pick-up coils

Problem Definition 6

Slanted sample

EC probe

Bolt

Proposed Solution 7

Sample

Scanning probe

FEM Modeling Using COMSOL

8

Challenges Build the 3D geometry Meshing Material parameters

Bolt Driver Cone Coil

Pick up Coils

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

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

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

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

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"

FEM modeling of edge effect 14

NO Edge Edge 1 Edge 2

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

Measurements 16

0o -90o 90o

NORTEC 600 D

Real Sample

Measurements 17

NO crack, 0.15”, rounded edge, 1000 Hz, 60 dB

0.6” crack, 0.15”, height, rounded edge, 1000 Hz, 60 dB

Measurements 18

NO crack, 0.15”, rounded edge, 200 Hz, 60 dB

0.6” crack, 0.15”, height, rounded edge, 200 Hz, 60 dB

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

Future work 20

Refine probe (make thinner, use spherical washer)

Develop eye brow probe

21

Thank you!