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• Extensiveexperienceof use of ultrasound in NDE

• Automatedultrasonictechniques to improve accuracy,speedandreliability

• PhasedArraystoreduce inspection time and cost

• Conformablephasedarraytoinspectcomponents with irregularsurfaces

What is Ultrasonic Inspection?

Ultrasound relates to pressure waves that propagate at frequenciesbeyondtheaudiblerangeofthehumanear.Figure1showsthebasicprincipleofultrasonicinspectionusing a single transducer.

When the ultrasonic wave encounters a defect within thecomponentthewaveisreflectedandscatters,changing the nature of the ultrasonic signal that is obtained by the receiver.

ThesignalrecordedbythereceivingtransducerisknownasanA-Scan,thissignalrepresentstheintensityoftheultrasonicenergythatreachesthereceiverinafixedtimewindow.ExamplesoftheA-Scansobtainedareshown inFigure2.

Rolls-Royce utilises the basic operational principle of ultrasound to inspect a wide range of different components.Anumberofbespoke,automatedscannershave been developed to improve the accuracy, speed and reliabilityoftheinspection.Dataisautomaticallyrecordedandanalysisiscompletedremotelytoreducetheexposureof personnel to ionising radiation.

Ultrasonic InspectionTheuseofultrasoundinNon-DestructiveEvaluation

Figure1.Ultrasonicflawdetectionusingasingletransducer,a)forcomponentswithnodefects,b)foracomponentcontainingadefect

A

B

Figure2.SimulatedA-scans

a)withnodefect b)withadefectpresent

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To maintain inspection performance it is essential to update the phased arraydelaylawsinordertocompensatefortheirregularsurfaceprofileofthe component under test; this effect is shown in Figure 5. This process canbeextremelychallenging;theresearchteamsarecurrentlyworkingtodevelopadvancedalgorithmsformorecomplexgeometriesandinspectiontechniques.

Themembraneprobecanbeusedforbothsurfaceprofilemeasurementand inspection, allowing rapid scanning without the need for multiple angled probes and time consuming mechanical scanning.

NDE–UltrasonicInspection

Metallurgical inspection Capability

Figure4.MembraneProbe

• InnovativeresearchprojectincollaborationwithImperialCollegeLondon

• Membraneprobebenefits:

–Accurate

–Versatile

–Lowcost

–Robust

–RapidScanning

a)forplanesurfacetestpiece

Figure3

Figure5.SectorscanforcompressionalwaveinspectionofsidedrilledholesusingImperial membrane device

b)testpiecewithweldcap when not updating delay laws

c)weldcapwithupdateddelay laws

Ultrasonic Phased Arrays

PhasedArraytransducerstypicallyconsistofalargenumberofidenticalpiezoelectricelements(array)whereeachelementisexcitedataslightlydifferenttime(phased)suchthatitispossibletosteerandfocustheultrasonicbeam;thisisshownschematicallyinFigure3.

Asinglephasedarraytransducercanbeusedtogeneratearangeofdifferent beams; it can therefore be used for multiple inspections.

Phased arrays also allow electronic scanning of a component, which significantlyincreasesinspectionspeedandhencereducescost.

Conformable Ultrasonic Phased Arrays

In contact ultrasonic inspection it is essential to maintain coupling between the transducer and the component under test.

Whenusingconventionalultrasonictechniquesitisnotalwayspossibletomaintaincontactandachieve100%testcoverageofcomponentswithirregular surfaces.

Rolls-RoyceisworkingwithImperialCollegeLondontoresearchanddevelop a new conformable phased array device that allows reliable ultrasonicinspectionofcomponentswithcomplexgeometries.

This low-cost membrane device, that uses a standard phased array, couplestothecomponentsurfaceviaafluidstandoffencapsulatedbyalow-loss membrane and is shown in Figure 4.

• Improvedaccuracy

• Fasterscanning

• Reducedinspectiontimeandhencecost

7166/CS.04/Aug10