Post on 05-Jan-2016
description
ANDE Course SAFTANDECourse SAFT
September24,2009
SyntheticApertureFocusingTechnique( )(SAFT)
Time domain Ultrasonic bulk wavesTimedomain Frequencydomain(FSAFT)
Ultrasonicbulkwaves
Ultrasonicguidedwaves(LSAFT)(F SAFT) (L SAFT)
Microwaves
SAFT ScopeSAFT Scope
Point sources andPoint sourcesandpointreceivers
Pulsedsignalsg Pointdefects Extended spatialExtendedspatialsamplingofdefectsignals
Synthetic Aperture Focusing with Phased Array Elementswith Phased Array Elements
Individual A- Scans
Tim
e
SmallFlaw
BasictSAFT
and, consequently, via Fourier inversion,
tSAFT:AScanapproach
tSAFT:Pixeldrivenapproach
Individual A- Scans
Tim
e
SAFT:LateralResolution
eff L2 =
LeffHalfpowerbeamwidthfortheeffective
effeff L2
D
aperture
At range R the horizontal D
RLx eff=Atrange R,thehorizontalextentofabeamfroman
apertureDisgivenby DRx = Forcompletecoverageoroverlap
Reff =LinearresolutioninazimuthatrangeR is
2DCombiningtheprevioustworelations,wegetthelateral
resolutionforSAFTas
zD 33.1=InnormalBscanimaging,the
resolutionisgivenby
tSAFT:Resolutioncapabilities
Example of SAFT
100 100 100 100
Element by element pulse-echo from a 1.5 mm dia SDH in Al
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RAW Image
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0.9
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X: 29Y: 0 8049
X: 34Y: 0.8171
X: 24Y: 0.8902
X: 27Y: 0.9146
X: 40Y: 0 8049
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0.9
1X: 27Y: 1
X: 44Y: 0.9255
X: 36Y: 1 X: 43
Y: 0.9681
X: 45Y: 0.9681
10 20 30 40 50 60
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0.9
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X: 27Y: 0.9589
X: 35Y: 1
X: 43Y: 0.9178
X: 25Y: 1
X: 45Y: 0.9315
10 20 30 40 50 60
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0.9
1X: 35Y: 1
X: 49Y: 1
X: 47Y: 0.9505
X: 36
SAFT Image
0.1
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X: 33Y: 0.3148
X: 29Y: 0.115 X: 34
Y: 0.1011
X: 33Y: 0.3148
Y: 0.8049 Y: 0.8049
X: 31Y: 0.3422
X: 30Y: 0.2619
0.2
0.3
0.4
0.5
0.6
0.7
0.8
X: 37Y: 0.254
X: 40Y: 0.112
X: 35Y: 0.3466
X: 32Y: 0.6489
X: 33
X: 42Y: 0.8298
X: 40Y: 0.6809
0.2
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X: 34Y: 0.5054
X: 36Y: 0.2977
Y: 0.9178
X: 22Y: 0.6438
X: 29Y: 0.6986
X: 35Y: 0.7397
X: 32X: 39Y: 0 09162
0.2
0.3
0.4
0.5
0.6
0.7
0.8
X: 36Y: 0.5309
X: 22Y: 0.8764
X: 37Y: 0.2653
X: 36Y: 0.9146
X: 34Y: 0.2826
X: 53Y: 0.5802
X: 18Y: 0.4938
X: 27Y: 0.5802
X: 32Y: 0.1241 X: 40
Y: 0.1107
0 10 20 30 40 50 60 700
0 10 20 30 40 50 60 700
0.1 Y: 0.0715
0 10 20 30 40 50 60 700
0.13
Y: 0.07272Y: 0.09162
0 10 20 30 40 50 60 700
0.1
13mmdeepSDH 19mmdeepSDH 26mmdeepSDH 45mmdeepSDH
FSAFT:Narrowbandversion
Scalarwaveequation
SpatialFouriertransformationofthesolution and its inversesolutionanditsinverse
propagator
Reconstructthefieldatz
FSAFT:BroadbandversionTemporalFouriertransform
Spatial FourierSpatialFouriertransformationatagiventemporalfrequency
propagator
Reconstructthefieldatzforthegiventemporalfrequencyfrequency
Reconstructthefieldatzthrough inverseFouriertransform
FSAFTandBandwidthEffects
Another example of SAFTAnotherexampleofSAFT
Theexampleshowsa30mmcrackina58mmthicksteelplate.A4MHzcontacttechniqueprobehasbeenused with a nominal angle of 70 The image spots in the SAFT image have constant sizes in the directionusedwithanominalangleof70 .TheimagespotsintheSAFTimagehaveconstantsizesinthedirectionperpendicularto70,theimagespotsoftheBscanshowupanincreasingwidthproportionaltothedistancetotheprobe,whichreflectsthespreadingofthesoundfield.
Volumetric Weld Volumetric Weld CoverageCoverage
TOFD
PE45 SW
PE60 SW
Volumetric Weld Coverage Volumetric Weld Coverage -- Data Visualisationo
v
e
m
e
n
t
r
o
b
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M
o
TOFD 60-SW60 SW 45-SW45-SW
P
r
TOFD 60 SW60 SW 45-SW45 SW
LSAFT Dispersioncorrected
ReferencesReferences
L.J. Busse, Three-dimensional imaging using a frequency-domain synthetic aperture focusing technique, IEEE Transac. UFFC 39 (1992) 174-179.
V. Schmitz, S. Chakhlov, W. Muller, Experiences with synthetic aperture , , , p y pfocusing technique in the field, Ultrasonics 38 (2000) 731738
D Levesque A Blouin C Neron J -P Monchalin Performance of laser-D. Levesque , A. Blouin, C. Neron, J. P. Monchalin, Performance of laser-ultrasonic F-SAFT imaging, Ultrasonics 40 (2002) 10571063