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

10 20 30 40 50 60

200

300

400

500

600

200

300

400

500

600

200

300

400

500

600

200

300

400

500

600

RAW Image

100

200

300

10 20 30 40 50 60 10 20 30 40 50 60

100

200

300

10 20 30 40 50 60

100

200

300

10 20 30 40 50 60

100

200

300

10 20 30 40 50 60

400

500

600

0.9

1

X: 29Y: 0 8049

X: 34Y: 0.8171

X: 24Y: 0.8902

X: 27Y: 0.9146

X: 40Y: 0 8049

10 20 30 40 50 60

400

500

600

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

400

500

600

0.9

1

X: 27Y: 0.9589

X: 35Y: 1

X: 43Y: 0.9178

X: 25Y: 1

X: 45Y: 0.9315

10 20 30 40 50 60

400

500

600

0.9

1X: 35Y: 1

X: 49Y: 1

X: 47Y: 0.9505

X: 36

SAFT Image

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

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

0.3

0.4

0.5

0.6

0.7

0.8

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

e

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