Phased Arry

8/10/2019 Phased Arry

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H ow Phased Arrays W orkH ow Phased Arrays W orkand W hat Can They do?and W hat Can They do?

H ouston O pen H ouseH ouston O pen H ouse

January 15January 15--17, 200317, 2003


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Source: NDT On-line

Phased arraysPhased arrays a definitiona definition

A mosaic of transducer elements in which

the timing of the elements' excitation canbe individually controlled to produce certain

desired effects, such as steering the beam

axis or focusing the beam.


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IllustrationIllustration --Beam Generation and FocusingBeam Generation and Focusing

Beam shaping isperformed by pulsing

the elements with

different time delays.This picture shows the

elements in the array,

and the delay applied

to each element

These time delays

(green histogram)

generate a focused

normal beam, from the

symmetrical

parabolic timedelays


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IllustrationIllustration --Beam DeflectionBeam Deflection

For shear waves,

the time delaypattern has a

slant as shown

here.

Focusing can be

performed by

using parabolictime delays (see

previous slide),

as well as theslant.


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IllustrationIllustration --Beam Deflection and FocusingBeam Deflection and Focusing

The picture shows the

generated beams in very

early, mid-stage, late andat focus.

For angling and focusing,

we use a combined slantand parabola.


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Beam GenerationBeam Generation


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Physics of Phased ArraysPhysics of Phased Arrays


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H ow Phased Arrays W orkH ow Phased Arrays W ork

Ultrasonic phased arrays consist of a series of

individual elem ents, each with its own connector,

time delay circuit, and A/D converter. Elem ents are acoustically insulated from each

other.

Elem ents are pulsed in groups with pre-calculated

time delays for each element, i.e. phasing.

For economic reasons, pulsersare usually

multiplexed. Instrumentation nomenclature such

as a FO CUS 32/128 refers to an instrument with

32 multiplexed pulsersand a total of 128

ultrasonic channels.


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PhasedPhased--arrayarrayprobeprobe

Basically, a phased-array is a long conventional probe

Cut into many elements


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Linear arrays are the most com mon type, and can

perform scanning in one dimension only. Linear

arrays typically minimize the number of elem ents

required, and hence cost.

M atrix arrays can scan in two dimensions, andoffer considerably more flexibility, albeit at a price.

Circular and sectorial-annular arrays are specific

for normal beam inspections, e.g. billets, forgings.


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The operator inputs the focal depth(s), inspection

angle(s) and/or couplant, plus how many and

which elem ents are to be fired.The operator also must input details on the array

and wedge. (This information is engraved on the

side of the array and wedge.)

The phased array calculator calculates what time

delays to apply to each element.

The operation of the calculator is shown in the

next slides.

For standard scans (e.g. electronic or sectorial),

the set-up is essentially straightforward.


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Focal point(X,Z)

The calculator searchs the Snell point. It considers the center of the active aperture

(from elements2 to 7 in this example).

Then, the X, Z point of the focal point is determinedThe wedge delay is calculated and the focal law is offset accordingly

interface

Xaxis or Scan axis

Depth

Snell point

law scan offset

Angle

Operator defines depth and refracted angleOperator defines depth and refracted angle


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Phased Array BasicsPhased Array Basics

For linear scans, arrays are multiplexed using the same Focal Law.

For sectorial scans, the same elements are used, but the Focal Laws are

changed.

For DDF, the receiver Focal Laws are changed in hardware.


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PhasedPhased ArrayArray BeamformingBeamforming

Beamforming requires precise pulsing and time delays.Receiving is the reverse of pulsing.


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U TU T PhasedPhased--ArrayArray

PrinciplesPrinciples&& CapabilitiesCapabilities


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ConventionalConventionalW aveform ingW aveform ing

Beam steering using conventional UT probe (EM ISSION) : acoustic beam generated by Huyghensprinciple

angled wedge introduces appropriate delays during emission to

generate angle beam

Crystal

Wedge

Material

Excitation pulse

Wave front

Delay

Location

A B C

A B C


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PhasedPhased--ArrayArrayW aveform ingW aveform ing

Beam steering using phased-array probe (EM ISSION) : acoustic beam generated by Huyghensprinciple

appropriate delays introduced electronically during em ission to

generate angle beam

Wave front

Time

Delay

Element

Focal law


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Beam steering using phased-array probe (RECEPTIO N) : appropriate delays introduced electronically during reception

O nly signals satisfying delay law shall be in phase and generate

significant signal after summation

S


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Global overview of phased-array signal processing


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Design Param eters of PhasedDesign Param eters of Phased--Array ProbesArray Probes

p g

e

H

A


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Beam FocusingBeam Focusing

Is thecapability to converge the acoustic energy

into a small focal spot

Allows forfocusing at several depths, using asingle probe

Symmetrical (e.g. parabolic) focal laws (time delay

vs. element position)

Is limitedto near-field only

Can only performed in the steering plane, whenusing a 1D-array


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Beam SteeringBeam Steering

Is thecapability to modify the refracted angleof

the beam generated by the array probe.

Allows formultiple angle inspections, using asingle probe

Applies asym metrical (e.g. linear) focal laws

Can only be performed in steering plane,when

using 1D-arrays

Can generate both L (compression) and SV (shearvertical) waves, using a single probe


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ElectronicalElectronical(Linear) Scanning(Linear) Scanning

Is theability to move the acoustic beam along the

axis of the array without any mechanical movement.

The beam movement is performed by time

multiplexing of the active elem ents

Scanning extent is limited by : number of elements in array

number of channels in acquisition system


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Com bined Beam ProcessingCom bined Beam Processing

The phased-array technique allows for

almost any combination of processing

capabilities :

focusing + steering

linear scanning + steering


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O ther Types of Array ProbesO ther Types of Array Probes

DUAL-ARRAY PRO BES :

Consist of separate transmitter (T) and

Receiver (R) arrays

In side-by-side configuration, all considerations for

conventional TRL probes remain valid :

Pseudo-focusing effect

Absence of interface echo

Improved SNR in attenuating materials

In addition, all advantages of the PA technique

are available


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W hat Phased Arrays Can DoW hat Phased Arrays Can Do


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This section illustrates typical scans that can beperformed using phased arrays:

Electronic (linear) scans Sectorial (azimuthal) scans

Transverse scans

Dynamic Depth Focusing Time-O f-Flight Diffraction

W ith the Tomoview software, operators cancustom-design their own scan patterns, displays

and output.


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Electronic or Linear ScanningElectronic or Linear Scanning

M ultiplex A Single Focal Law

Across the Array


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Electronic ScanningElectronic Scanning

This animation shows a conceptual weld inspection using electronic

(linear) scanning. This approach can easily emulate typical ASME-

type 45 and 60 shear wave inspections, and is much faster than rasterscanning.

Typical weld inspection requires two or more angles with implied

raster size, step size etc. Need to cover weld, HAZ, any positionerrors => significant amount of scanning.

i i il i (li )S i


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Electronic (linear) Scanning onElectronic (linear) Scanning on

Circular Com ponentsCircular Com ponents

Electronic scanning permits very rapid scanning of componentswith constant geometry, e.g. tubes, pipes.


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Sectorial (Azim uthal) ScanningSectorial (Azim uthal) Scanning

Changing the Inspection Angle

without M oving the Array


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Illustration of Sectorial ScanningIllustration of Sectorial Scanning


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S t il(A i th l)SS t il(A i th l)S


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Sectorial (Azim uthal) ScansSectorial (Azim uthal) Scans

Sectorial scanning by changing the

incident angle without changing position

can be used for a variety of inspections.


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Sectorial Scanning Anim ationSectorial Scanning Anim ation

This illustration

shows a turbine blade

root being inspected

using S-scans

(sectorial scanning).


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Turbine Welded Rotor InspectionTurbine Welded Rotor Inspection

Phased-array inspection:

Sectorial scan 30-60 SW

Step of 1 degree

Mechanical scan along the

circumferential axis

Phased-array probe:

5 MHz, 16 elements, 16 mm x

16 mmmounted on a wedge

Calibration block:EDM notches 2 mm x 0.5 mm


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Electronic/Sectorial Scanning Anim ationElectronic/Sectorial Scanning Anim ation


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Dynam ic Depth FocusingDynam ic Depth Focusing

Extending the Focal Range

Electronically


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Schematic Representation ofSchematic Representation of

Dynamic Depth FocusingDynamic Depth Focusing

Mechanical Displacement

c = velocity in material

FOCUS DEPTH (PULSER)

DYNAMIC FOCUSING (RECEIVER)

Beamdisplacement

DDF is an

excellent way

of inspecting

thick

components in

a single pulse.The beam is

re-focused

electronicallyon its return


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Dynam ic Depth FocusingDynam ic Depth Focusing

Standardphasedarray

Phased Array withDynam ic Depth

Focusing


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Dynam ic Depth Focusing Anim ationDynam ic Depth Focusing Anim ation


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Tim eTim e--O fO f--Flight DiffractionFlight Diffraction

O ptimum Sizing Technique for

Thicker Components

TO FD usingPhasedArraysTO FD usingPhased Arrays


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TO FD using Phased ArraysTO FD using Phased Arrays

sam e as conventional U Tsam e as conventional U T

Transmitter Receiver

Lateral wave

LW

Upper tip Lower tip

Back-wall reflection

BW


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W hat Do TO FD Scans Look Like?W hat Do TO FD Scans Look Like?

Lateral wave is clearlyseen in a good TOFD

scan (top signal).

Backwall signal isstrong (bottom signal).

Both typically used

for calibration.

On clean material,

defects show up well.

Backwall is alwaysstrong. Watch for

perturbations due to

surface-breakingdefects (also on lateral

wave .


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L d i Ph d A T h lL d i Ph d A T h l


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Leader in Phased Array TechnologyLeader in Phased Array Technology

First system on site1993

M ore than 400PA unitssold

Improved technology4th generation

Advanced PAtechnology

DDF-VFT-TRM


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IndustrialProductLineIndustrialProductLine


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QuickScan PA

Industrial Product LineIndustrial Product Line

An economicalsolution for

industrial

requirements, e.g.in-line inspections

on production plant.

Rack-mounted.

Similar capabilities

to FOCUS, but less

flexible.

O i P t bl PA U it


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Omniscan Portable PA UnitFunction keys and knob interface for field used

Data on RDTIFF exportable and compatible with Tomoview

Multiview

remote console for easy operation with only one operator.

E-Z View for adequate viewing and control in operationconditions

1CONFIG

ABC

4

TOOLS

JKL

6

AXIS

PQR

7

USERSTU

9

CALIBYZ

+/-CHANNEL

_ %#

.

CLEAR

CLR

2FILE

DEF

5

Utilities

MNO

8

FREEZEVWX

0

. *

3DISPLAY

GHI

Start/

Stop

--->

Store /

Print


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Instrum entation N om enclatureInstrum entation N om enclature

Phased array units (FO CUS or Q uickscan)are defined as two numbers divided by a

backslash, e.g. 32/128. This refers to an instrument with 32multiplexed pulsersand 128 individualchannels.

R/D Tech instruments are supplied in binarysizes, e.g. 16/64, 16/128, 32/256 .

Instruments are custom-built for theapplication.


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TomoViewTomoView


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Real-time, multichannel,

angle-corrected top, side,

and front views

Pulse-echo and TO FD functions

Logarithmic and linear

12-bit data

RF, compressed,and C-scan data

W eld overlays

User-defined screen and reportlayouts

Handles GB-size data files

O nline and offline modes

TomoViewTomoViewPC-based UT software


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CorrectedCorrected SS--scanscan ViewView


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M erging of dataM erging of data

Raw UT data generated by different focallaws (angles, focusing depths) can be

merged off-lineto generate new UT data M erged data contain maximum amplitudeof the different focal laws

M erged data can be treated as regular data,and visualisedas VC Top (C-scan), Side (B-scan) and End (D-scan) Views

Time-saving during data analysis


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Sum m arySum m ary FO CU S, Q uickscan & Tom oviewFO CU S, Q uickscan & Tom oview

FOCUS: Commercial system, ~ four years old

O ver two hundred and fifty sold

In service 24/7 in several industries Q uickscan:

Industrial version of FO CUS

19 rack-mounted

Less flexible than FO CUS, but cheaper

O mniscan: New, portable phased array system

Tomoview: Established commercial software

W idely used on hundreds of systems

Very flexible for inspections, displays, windows etc.

Documents

Phased Arry