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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H ow Phased Arrays W orkH ow Phased Arrays W ork
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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H ow Phased Arrays W orkH ow Phased Arrays W ork
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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PhasedPhased--ArrayArrayW aveform ingW aveform ing
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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PhasedPhased--ArrayArrayW aveform ingW aveform ing
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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H ow Phased Arrays W orkH ow Phased Arrays W ork
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.