Intro to Shearography
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Transcript of Intro to Shearography
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Shearography - NDT Capabilities
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The basic principles of the measurement method are interferometry and correlation techniques
Interferometry is determination of fractional relative phase difference between light waves traversing different paths. Phenomena which can be measured are those which influence the phase of the light beams. In practice this is e. g. surface deformation
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The basic principles of the measurement method are interferometry and correlation techniques
Digital Image Correlation is a data analysis method, which uses a proprietary mathematical correlation method to analyse digital image data taken while samples are subjected to mechanical stresses. Consecutive image captures taken during the testing phase will “show” a change in surface characteristics as the specimen is effected by the mechanical stresses imposed upon it.
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Non-destructive testing is the common use of shearography. The defects become visible on measuring their inhomogeneous deformation gradients. Depending on the spatial distribution of deformation the defect or the structure itself can be characterised. The rotor measurements show a dis-bond (left), a crack (right) and a structural transition (centre). Compare fringe density and distribution.
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Dynamic excitation is a special technique of isi-sys for non destructive testing. During the sweep the vibration modes are visible in real-time. The example (left) shows selected images of C-Si-C composite (sweep 1-20kHz) with an in service dis-bond in the middle. Further data processing enables determination the mechanical properties of the defect area.
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Impact defect detection in carbon fibre composites (CFRP) by dynamic excitation
The examples shows carbon fibre panel with impacts prepared by Airbus, Bremen. Similar carbon composites are used for the new Airbus A380.
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Impact defect detection in carbon fibre composites (CFRP) by dynamic excitation
The defects are prepared by impacts of different energies. The defects become visible by dynamic excitation at their natural frequencies as show below.
Defect visible at 17.873Hz
Evaluated vibration mode
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Example of NDT by dynamic excitation applied on GLAREThe examples shows a glare panel (size 500x500, see below) with de-bondings (Ø60mm) prepared by Airbus Bremen. Glare is a combination of Aluminium plates with composite layers used for the new Airbus A380F.The defects (dis-bonds or delaminations) are prepared in different depth between the aluminum plates. The defects become visible by dynamic excitation at their natural frequencies as show below by the supperposed measurement results.
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Illuminated
object
Birefringent
element Polarizer
Lens
CCDImage processing
Loading:
Thermal
Vacuum – pressure
Vibration
Mechanical
Shearography principle recall
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Comparaison : TV-Holographie and Shearographie
Typical shearographic result
- - - Initial position
_____ After-stress position
Measured value
x Shear length
Typical TV-holography result13-02-2001 19:37:20
Deslocamento [µm]
PV= 30.614
LOME/INEGI
-5.5
-2.1
1.3
4.7
8.1
11.5
14.9
18.3
21.7
25.1
3.1 27.0 52.1 76.0 100.7 124.6 149.7 173.6 198.3 222.2 247.3
91.9
73.7
55.9
37.7
20.2
13-02-2001 19:37:20
Deformação [µm/shear]
PV= 2.497
LOME/INEGI
X=11.0
Y=59.6
32.9
59.6
55.6
59.6
78.8
59.6
101.9
59.6
124.6
60.2
147.7
60.2
170.8
60.2
193.6
60.2
216.7
60.2
239.4
61.0
-1.301
-1.052
-0.802
-0.552
-0.303
-0.053
0.197
0.446
0.696
0.946
1.195
13-02-2001 19:49:40
Deslocamento [µm]
PV= 30.925
LOME/INEGI
X= 9.8
Y=59.6
32.9
59.6
55.6
60.2
78.8
60.2
101.9
61.0
124.6
61.6
147.7
61.6
170.8
62.2
193.6
62.2
216.7
63.1
239.4
63.6
-5.54
-2.45
0.64
3.74
6.83
9.92
13.01
16.11
19.20
22.29
25.38
11-12-2000 10:56:13
Deformation [µm/shear]
PV= 3.301
NDT Expert
3-grad.TFD
-1.75
-1.38
-1.01
-0.65
-0.28
0.09
0.45
0.82
1.19
1.55
6.9 31.5 57.3 82.3 107.8 132.8 158.6 183.2 209.1 233.7 259.5
138.6
108.2
78.8
48.9
19.5
Shearography principle recall
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REPORTING
SIZING
LOCALIZATION
Monitoring on Optical disc – useful on serialised parts
FOLLOW UP
Shearography - Capabilities
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13-02-2001 18:23:41
Deformation [µm]
PV= 6.332
Dr. Ettemeyer GmbH & Co.
-4.08
-3.38
-2.67
-1.97
-1.26
-0.56
0.14
0.85
1.55
2.25
33.1 57.3 80.7 104.9 128.3 152.5 176.0 200.1 223.6 247.8
99.2
78.8
59.5
39.1
19.8
13-02-2001 18:23:41
Deformation [µm]
PV= 3.203
Dr. Ettemeyer GmbH & Co.
-1.62
-1.27
-0.91
-0.55
-0.20
0.16
0.51
0.87
1.23
1.58
33.1 57.3 80.7 104.9 128.3 152.5 176.0 200.1 223.6 247.8
99.2
78.8
59.5
39.1
19.8
13-02-2001 18:20:31
Deformation [µm]
PV= 5.434
Dr. Ettemeyer GmbH & Co.
X9.86
57.44105.02
152.60200.19
247.77
Y
158.09
118.45
78.81
39.17
-0.47
-40.11
Z
-3.77
-2.69
-1.60
-0.51
0.57
1.66
13-02-2001 18:20:31
Deformation [µm]
PV= 2.502
Dr. Ettemeyer GmbH & Co.
X9.86
57.44105.02
152.60200.19
247.77
Y
158.09
118.45
78.81
39.17
-0.47
-40.11
Z
-1.30
-0.80
-0.30
0.20
0.70
1.20
Shearography - Capabilities
Example of images obtained with thermal Loading
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X-ray result Shearographic Images with two perpendicular shear directions
DAMAGE TYPE DETECTED – Honey comb junctions dislocation
Shearography - Capabilities
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unbounding
DAMAGE TYPE DETECTED – Metal/metal edges unbounding
Top view
Profile view
Shearography - Capabilities
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ON CONCORDE
Positioning and sizing tool
Shearography - Capabilities
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DAMAGE TYPE DETECTED – Adhesive craking under impact
Cross section Adhesive cracks Honeycomb
Skin
Top view
Visible impacted area
Multiple adhesive cracks
Shearography - Capabilities
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Shearography - Capabilities
Example of vacuum loading
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Liquid ingress
unbound
DAMAGE TYPE DETECTED – Water or liquid ingress
Shearography - Capabilities
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US-Laser System
Shearographic system
Thermographic system
Comparative tests
Shearography - Capabilities
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Thermography Lock-InShearography immediate(t)
Shearography after 15 sc. (t’)
US-Laser (Amplitude)
US-Laser (time base)
Results of Comparative tests
Shearography - Capabilities
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US C-ScanImpacted Monolithc
(CFRP)Displacement field
Corrosion Detection
Aluminium Alloys
CF C-ScanDisplacement field
Shearography - Capabilities
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MIRA pressure vessel Filamentary wounded (Al-
GFRP)
Ageing control
Delamination detection
Old New
Procedure Control – Diagram of the part to be inspected
Shearography - CapabilitiesPressurized material control
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Benefits:
Contact less
Global method,
Good sensitivity,
Real time inspection,
Quicker than most of the NDI methods,
Working on all type of materials and structures,
Numerical acquisition give rise to efficient follow up,
New type of damage are now detectable without opening the structure…
The keys of the efficiency are in the selection of the loading and the implementation
Conclusions
Shearography - Capabilities