cursillo phased array.doc

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1.0 Introduction 1.1 General introduction to ultrasonic testing  1.2 A brief histor y of phased array testing 1.3 Types of equipment currently available  1. !hat is a phased array system" 1.# !hat do they do" 1.$ Advantag es of phase d array as co mpared % ith convention al &T 2.0 Transducers 2.1 'onventional transducer construction  2.2 'onventional beam characteristics  2.3 !ave front dynamic properties in conventional probes  2. 'omposite monolithic transducers  2.# (ingle element transducer characteri)ation  2.$ Inside a phased array transducer  2.* +hased array transducer characteristics  2., +hased array %edges  2.- +hased array pulsing and its effects  2.10 ocal la% sequencing 2.11 /eam shaping 2.12 /eam steering 2.13 Grating lobes and side lobes  2.1 ocusing %ith phased array probes  2.1# +hased array probe selection summary 3.0 Imaging /asics 3.1 Introduction  3.2 A(can da ta 3.3 (ingle alue /(can 3. '(can mapping 3.# +hased array '(can 3.$ 'ross sectional /(can 3.* +hased array inear scans  3., +hased array (ectorial scans (scans4  3.- 'ombined image formats  3.10 5vervie% of beam effects on sectorial scans .0 +hased Array Instrumentation .1 5vervie% .2 Instrument bloc6 diagram .3 Important specifications

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1.0 Introduction

1.1 General introduction to ultrasonic testing 1.2 A brief history of phased array testing

1.3 Types of equipment currently available 1. !hat is a phased array system" 1.# !hat do they do" 1.$ Advantages of phased array as compared %ith conventional &T

2.0 Transducers

2.1 'onventional transducer construction 2.2 'onventional beam characteristics 2.3 !ave front dynamic properties in conventional probes

2. 'omposite monolithic transducers 2.# (ingle element transducer characteri)ation 2.$ Inside a phased array transducer 2.* +hased array transducer characteristics 2., +hased array %edges 2.- +hased array pulsing and its effects 2.10 ocal la% sequencing 2.11 /eam shaping 2.12 /eam steering 2.13 Grating lobes and side lobes

2.1 ocusing %ith phased array probes 2.1# +hased array probe selection summary

3.0 Imaging /asics

3.1 Introduction 3.2 A (can data 3.3 (ingle alue / (can 3. ' (can mapping 3.# +hased array ' (can 3.$ 'ross sectional / (can 3.* +hased array inear scans 3., +hased array (ectorial scans ( scans4 3.- 'ombined image formats 3.10 5vervie% of beam effects on sectorial scans

.0 +hased Array Instrumentation

.1 5vervie%

.2 Instrument bloc6 diagram

.3 Important specifications

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.3.1 'onventional instruments

.3.2 +hased array instruments

.3.3 'alibration and normali)ation methods

.3. 'ombined phased array and conventional &T instruments

#.0 Anatomy of +hased Array 7isplay

#.1 Anatomy of +hased Array 7isplay #.2 ocal a% (etup #.3 (traight /eam inear scans#. Angled inear (cans #.# ocal a% (equence #.$ 7efect +ositioning #.* Interpreting (ector (ector

$.0 Typical Applications

$.1 ist of current applications notes

*.0 Glossary of +hased Array Terms

Glossary of +hased Array Terms

1.1 General introduction to ultrasonic testing

&ltrasonic test instruments have been used in industrial applications for more than si8ty years.(ince the 1- 0s9 the la%s of physics that govern the propagation of high frequency sound%aves through solid materials have been used to detect hidden crac6s9 voids9 porosity9 andother internal discontinuities in metals9 composites9 plastics9 and ceramics9 as %ell as tomeasure thic6ness and analy)e material properties. &ltrasonic testing is completelynondestructive and safe9 and it is a %ell established test method in many basic manufacturing9process9 and service industries9 especially in applications involving %elds and structural metals.

The gro%th of ultrasonic testing largely parallels developments in electronics9 and later incomputers. :arly %or6 in :urope and the &nited (tates in the 1-30s demonstrated that highfrequency sound %aves %ould reflect from hidden fla%s or material boundaries in predictable%ays9 producing distinctive echo patterns that could be displayed on oscilloscope screens.(onar development during the (econd !orld !ar provided further impetus for research inultrasonics. In 1- #9 &( researcher loyd irestone patented an instrument he called the(upersonic ;eflectoscope9 %hich is generally regarding as the first practical commercialultrasonic fla% detector that used the pulse<echo technique commonly employed today. It %ouldlead to the many commercial instruments that %ere introduced in the years that follo%ed.

Among the companies that %ere leaders in the development of ultrasonic fla% detectors9 gages9

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and transducers in the 1-$0s and 1-*0s %ere +anametrics9 (taveley9 and =arisonic9 all of%hich are no% part of 5lympus >7T.

In the late 1- 0s9 researchers in ?apan pioneered the use of ultrasonic testing in medicaldiagnostics using early / scan equipment that provided a t%o dimensional profile image oftissue layers. /y the 1-$0s9 early versions of medical scanners %ere being used to detect andoutline tumors9 gallstones9 and similar conditions. In the 1-*0s9 the introduction of precisionthic6ness gages brought ultrasonic testing to a %ide variety of manufacturing operations thatrequired thic6ness measurement of parts in situations %here there %as access to only one side9and corrosion gages came into %ide use for measurement of remaining %all thic6ness in metalpipes and tan6s.

The latest advances in ultrasonic instruments have been based on the digital signal processingtechniques and the ine8pensive microprocessors that became available from the 1-,0s on%ard.This has led to the latest generation of miniaturi)ed9 highly reliable portable instruments and online inspection systems for fla% detection9 thic6ness gaging9 and acoustic imaging.

1.2 A brief history of phased array testing

7uring their first couple decades9 commercial ultrasonic instruments relied entirely on singleelement transducers that used one pie)oelectric crystal to generate and receive sound %aves9dual element transducers that had separate transmitting and receiving crystals9 and pitch<catchor through transmission systems that used a pair of single element transducers in tandem.These approaches are still used by the ma@ority of current commercial ultrasonic instruments

designed for industrial fla% detection and thic6ness gaging9 ho%ever instruments using phasedarrays are steadily becoming more important in the ultrasonic >7T field.

The principle of constructive and destructive interaction of %aves %as demonstrated by :nglishscientist Thomas oung in 1,01 in a notable e8periment that utili)ed t%o point sources of lightto create interference patterns. !aves that combine in phase reinforce each other9 %hile %avesthat combine out of phase %ill cancel each other.

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+hase shifting9 or phasing9 is in turn a %ay of controlling these interactions by time shifting %avefronts that originate from t%o or more sources. It can be used to bend9 steer9 or focus the energyof a %ave front. In the 1-$0s9 researchers began developing ultrasonic phased array systemsthat utili)ed multiple point source transducers that %ere pulsed so as to direct sound beams bymeans of these controlled interference patterns. In the early 1-*0s9 commercial phased arraysystems for medical diagnostic use first appeared9 using steered beams to create crosssectional images of the human body.

Initially9 the use of ultrasonic phased array systems %as largely confined to the medical field9aided by the fact that the predictable composition and structure of the human body ma6e

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instrument design and image interpretation relatively straightfor%ard. Industrial applications9 onthe other hand9 represent a much greater challenge because of the %idely varying acousticproperties of metals9 composites9 ceramics9 plastics9 and fiberglass9 as %ell as the enormousvariety of thic6nesses and geometries encountered across the scope of industrial testing. Thefirst industrial phased array system9 introduced in the 1-,0s9 %ere e8tremely large9 and requireddata transfer to a computer in order to do the processing and image presentation. Thesesystems %ere most typically used for in service po%er generation inspections. In large part9 thistechnology %as pushed heavily in the nuclear mar6et9 %here critical assessment more greatlyallo%s use of cutting edge technology for improving probability of detection. 5ther earlyapplications involved large forged shafts and lo% pressure turbine components.

+ortable9 battery po%ered phased array instruments for industrial use appeared in the 1--0s. Analog designs had required po%er and space to create the multi channel configurationsnecessary for beam steering9 but the transition into the digital %orld and the rapid developmentof ine8pensive embedded microprocessors enabled more rapid development of the ne8tgeneration phased array equipment. In addition9 the availability of lo% po%er electroniccomponents9 better po%er saving architectures9 and industry %ide use surface mount boarddesign led to miniaturi)ation of this advanced technology. This resulted in phased array tools%hich allo%ed electronic setup9 data processing9 display and analysis all %ithin a portabledevice9 and so the doors %ere opened to more %idespread use across the industrial sector. Thisin turn drove the ability to specify standard phased array probes for common applications.

1.3 Types of equipment currently available

As %ith other categories of ultrasonic test equipment9 phased array systems are available in avariety of models %ith increasing comple8ity and capability. Instruments range from basicmodels that perform simple sector and linear scans %ith 1$ element probes to advancedsystems that offer multi channel capability and advanced interpretive soft%are %ith probes of upto 2#$ elements. urther information on the 5lympus >7T phased array product line is availablehere

1. !hat is a phased array system"

An array transducer is simply one that contains a number of separate elements in a singlehousing9 and phasing refers to ho% those elements are sequentially pulsed. A phased arraysystem is normally based around a speciali)ed ultrasonic transducer that contains manyindividual elements typically from 1$ to 2#$4 that can be pulsed separately in a programmedpattern. These transducers may be used %ith various types of %edges9 in a contact mode9 or inimmersion testing. Their shape may be square9 rectangular9 or round9 and test frequencies aremost commonly in the range from 1 to 10 B=). ou %ill find much more information aboutphased array probes in the follo%ing sections of this tutorial.

1.# !hat do they do"

+hased array systems pulse and receive from multiple elements of an array. These elementsare pulsed in such a %ay as to cause multiple beam components to combine %ith each otherand form a single %ave front traveling in the desired direction. (imilarly9 the receiver function

combines the input from multiple elements into a single presentation.

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/ecause phasing technology permits electronic beam shaping and steering9 it is possible togenerate a vast number of different ultrasonic beam profiles from a single probe assembly9 andthis beam steering can be dynamically programmed to create electronic scansC

This enables the follo%ing capabilitiesC1. (oft%are control of beam angle9 focal distance9 and beam spot si)e. These parameterscan be dynamically scanned at each inspection point to optimi)e incident angle andsignal to noise for each part geometry.

2. Bultiple angle inspection can be performed %ith a single9 small9 multi element probeand %edge9 offering either single fi8ed angles or a scan through a range of angles.

3. These capabilities provide greater fle8ibility for inspection of comple8 geometries andtests in %hich part geometry limits access.

. Bultiple8ing across many elements allo%s motionless high speed scans from a singletransducer position. Bore than one scan may be performed from a single location %ith

various inspection angles.

1.$ Advantages of phased array as compared %ith conventional &T

&ltrasonic phased array systems can potentially be employed in almost any test %hereconventional ultrasonic fla% detectors have traditionally been used. !eld inspection and crac6detection are the most important applications9 and these tests are done across a %ide range ofindustries including aerospace9 po%er generation9 petrochemical9 metal billet and tubular goodssuppliers9 pipeline construction and maintenance9 structural metals9 and general manufacturing.+hased arrays can also be effectively used to profile remaining %all thic6ness in corrosionsurvey applications.

The benefits of phased array technology over conventional &T come from its ability to usemultiple elements to steer9 focus and scan beams %ith a single transducer assembly. /eamsteering9 commonly referred to sectorial scanning9 can be used for mapping components atappropriate angles. This can greatly simplify the inspection of components %ith comple8geometry. The small footprint of the transducer and the ability to s%eep the beam %ithoutmoving the probe also aids inspection of such components in situations %here there is limitedaccess for mechanical scanning. (ectorial scanning is also typically used for %eld inspection.The ability to test %elds %ith multiple angles from a single probe greatly increases theprobability of detection of anomalies. :lectronic focusing permits optimi)ing the beam shapeand si)e at the e8pected defect location9 as %ell as further optimi)ing probability of detection.

The ability to focus at multiple depths also improves the ability for si)ing critical defects forvolumetric inspections. ocusing can significantly improve signal to noise ratio in challenging

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applications9 and electronic scanning across many groups of elements allo%s for ' (canimages to be produced very rapidly.

The potential disadvantages of phased array systems are a some%hat higher cost and arequirement for operator training9 ho%ever these costs are frequently offset by their greaterfle8ibility and a reduction in the time required to perform a given inspection.

2.1 'onventional transducer construction

To understand ho% phased array transducers %or69 it is helpful to first consider the conventionalmonolithic ultrasonic transducers designed for >7T applications.

These transducers come in a %ide variety of si)es9 frequencies9 and case styles9 but most havea common internal structure. Typically9 the active element of the transducer is a thin dis69square9 or rectangle of pie)oelectric ceramic that converts electrical energy into mechanicalenergy ultrasonic vibrations49 and vice versa. It is protected from damage by a %earplate oracoustic lens9 and bac6ed by a bloc6 of damping material that quiets the transducer after thesound pulse has been generated. This ultrasonic subassembly is mounted in a case %ithappropriate electrical connections. 'ommon contact9 delay line9 immersion9 and angle beamtransducers utili)e this basic design. 7ual element transducers9 commonly used in corrosion

survey applications9 differ in that they have separate transmitting and receiving elementsseparated by a sound barrier9 no bac6ing9 and an integral delay line rather than a %earplate orlens.

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2.2 'onventional beam characteristics

'onventional single element longitudinal %ave ultrasonic transducers %or6 as a piston source ofhigh frequency mechanical vibrations9 or sound %aves. As voltage is applied9 the pie)oelectrictransducer element often called a crystal4 deforms by compressing in the directionperpendicular to its face. !hen the voltage is removed9 typically less than a microsecond later9the element springs bac69 generating the pulse of mechanical energy that comprises anultrasonic %ave. The graphic belo% sho%s a conceptuali)ed e8ample of ho% a pie)oelectricelement responds to a brief electrical pulse .

Transducers of the 6ind most commonly used for ultrasonic >7T %ill have these fundamentalfunctional propertiesC

Type The transducer %ill be identified according to function as a contact9 delay line9 angle

beam9 or immersion type. Inspected material characteristics such as surface roughness9temperature9 and accessibility as %ell as the position of a defect %ithin the material and the

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The far field is the region beyond > %here the sound pressure gradually drops to )ero as thebeam diameter e8pands and its energy dissipates. The near field distance is a function of thetransducerEs frequency and diameter9 and the sound velocity in the test medium9 and it may becalculated as follo%s for the square or rectangular elements commonly found in phased arraytestingC

/ecause of the sound pressure variations %ithin the near field9 it can be difficult to accuratelyevaluate fla%s using amplitude based techniques although thic6ness gaging %ithin the nearfield is not a problem4. Additionally9 > represents the greatest distance at %hich a transducerEsbeam can be focused by means of either an acoustic lens or phasing techniques. ocusing isdiscussed further in section 2.1 9 Focusing with Phased Array Probes.

The aspect radio constant is as follo%s9 based on the ratio bet%een the short and longdimensions of the element or apertureC

Ratio short/long k

1.0 1.3* square element4

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0.- 1.2#

0., 1.1#

0.* 1.0-

0.$ 1.0

0.# 1.01

0. 1.00

0.3 and belo% 0.--

In the case of circular elements9 6 is not used and the diameter of the element 74 is usedinstead of the length termC

2.3 !ave front dynamic properties in conventional probes

!ave front formation

!hile a single element transducer may be thought of as a piston source9 a single dis6 or platepushing for%ard on the test medium9 the %ave it generates may be mathematically modeled asthe sum of the %aves from a very large number of point sources. This derives from =uygensE+rinciple9 first proposed by seventeenth century 7utch physicist 'hristiaan =uygens9 %hichstates that each point on an advancing %avefront may be thought of as a point source thatlaunches a ne% spherical %ave9 and that the resulting unified %ave front is the sum of all ofthese individual spherical %aves.

/eam spreading

In principle9 the sound %ave generated by a transducer %ill travel in a straight line until itencounters a material boundary. !hat happens then is discussed belo%. /ut if the sound pathlength is longer than the near field distance9 the beam %ill also increase in diameter9 divergingli6e the beam of a spotlight. The beam spread angle of an unfocused transducer can becalculated as follo%sC

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rom this equation it can be seen that beam spreading increases %ith lo%er frequencies andsmaller diameters. (ince a large beam spread angle can cause sound energy per unit area to

quic6ly drop %ith distance9 effectively decreasing sensitivity to small reflectors9 echo response insome applications involving long sound paths can be improved by using higher frequency

and<or larger diameter transducers.

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Attenuation

As it travels through a medium9 the organi)ed %ave front generated by an ultrasonic transducer%ill begin to brea6 do%n due to imperfect transmission of energy through the microstructure ofany material. 5rgani)ed mechanical vibrations sound %aves4 turn into random mechanicalvibrations heat4 until the %ave front is no longer detectable. This process is 6no%n as soundattenuation.

The mathematical theory of attenuation and scattering is comple8. The loss of amplitude due toattenuation across a given sound path %ill be the sum of absorption effects9 %hich increaselinearly %ith frequency9 and scattering effects9 %hich vary through three )ones depending on theratio of the si)e of grain boundaries or other scatterers to %avelength. In all cases9 scatteringeffects increase %ith frequency. or a given material at a given temperature9 tested at a given

frequency9 there %ill be a specific attenuation coefficient9 commonly e8pressed in >epers percentimeter >p<cm4. 5nce this attenuation coefficient is 6no%n9 losses across a given soundpath may be calculated according to the equation

As a practical matter9 in ultrasonic >7T applications attenuation coefficients are normallymeasured rather than calculated. =igher frequencies %ill be attenuated more rapidly than lo%erfrequencies in any medium9 so lo% test frequencies are usually employed in materials %ith highattenuation coefficients li6e lo% density plastics and rubber.

;eflection and transmission at a perpendicular planeboundary

!hen a sound %ave traveling through a medium encounters a boundary %ith a dissimilarmedium that lies perpendicular to the direction of the %ave9 a portion of the %ave energy %ill bereflected straight bac6 and a portion %ill continue straight ahead. The percentage of reflectionversus transmission is related to the relative acoustic impedances of the t%o materials9 %ithacoustic impedance in turn being defined as material density multiplied by speed of sound. Thereflection coefficient at a planar boundary9 the percentage of sound energy that is reflected bac6to the source9 may be calculated as follo%sC

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rom this equation it can be seen that as the acoustic impedances of the t%o materials becomemore similar9 the reflection coefficient decreases9 and as the acoustic impedances become lesssimilar9 the reflection coefficient increases. In theory the reflection from the boundary bet%eent%o materials of the same acoustic impedance is )ero9 %hile in the case of materials %ith verydissimilar acoustic impedances9 as in a boundary bet%een steel and air9 the reflectioncoefficient approaches 100F.

;efraction and mode conversion at non perpendicularboundaries

!hen a sound %ave traveling through a material encounters a boundary %ith a differentmaterial at an angle other than )ero degrees9 a portion of the %ave energy %ill be reflectedfor%ard at an angle equal to the angle of incidence. At the same time9 the portion of the %aveenergy that is transmitted into the second material %ill be refracted in accordance %ith (nellEs

a%9 %hich %as independently derived by at least t%o seventeenth century mathematicians.(nellEs la% related the sines of the incident and refracted angle to the %ave velocity in eachmaterial as diagramed belo%.

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If sound velocity in the second medium is higher than that in the first9 then above certain anglesthis bending %ill be accompanied by mode conversion9 most commonly from a longitudinal %avemode to a shear %ave mode. This is the basis of %idely used angle beam inspectiontechniques. As the incident angle in the first slo%er4 medium such as a %edge or %aterincreases9 the angle of the refracted longitudinal %ave in the second faster4 material such asmetal %ill increase. As the refracted longitudinal %ave angle approaches -0 degrees9 aprogressively greater portion of the %ave energy %ill be converted to a lo%er velocity shear%ave that %ill be refracted at the angle predicted by (nellEs a%. At incident angles higher thanthat %hich %ould create a -0 degree refracted longitudinal %ave9 the refracted %ave e8ists

entirely in shear mode. A still higher incident angle %ill result in a situation %here the shear%ave is theoretically refracted at -0 degrees9 at %hich point a surface %ave is generated in thesecond material. The diagram belo% sho%s this effect for a typical angle beam assemblycoupled into steel.

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2. 'omposite monolithic transducers

7uring the first fe% decades of ultrasonic >7T9 transducers %ere based on solid dis6s of quart)or pie)oelectric ceramics. Bore recently9 composite transducers have been introduced as analternative. !hile increased manufacturing costs ma6e them more e8pensive9 they have the

advantage of significantly increasing sensitivity by as much as 12 d/ over comparableconventional elements %hile maintaining broad band%idth and a relatively fast pulse recoverytime.

'omposite transducers are made by dicing standard pie)oelectric material into a grid. Thespaces in the diced element are filled %ith epo8y9 and the bottom is ground a%ay to leave aseries of tiny pie)oelectric bloc6s in an epo8y matri8. /oth sides are then plated for electricalcontact. The ra% material is cut to si)e in a square9 rectangular9 or circular shape depending onthe model of transducer it %ill become.

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In the resulting transducer element9 the many pie)oelectric bloc6s each act as point sources forspherical %ave fronts that combine into a single %ave in accordance %ith =uygensE +rinciple.Transducer sensitivity is increased because the individual pie)oelectric bloc6s can more freelye8pand and contract as compared to a given point in the middle of a solid dis6 or plate.

Additionally9 the presence of the epo8y lo%ers the acoustic impedance of the transducer9creating more efficient sound coupling into %edges9 delay lines9 and %ater9 as %ell as intononmetallic test materials li6e composites and polymers. 5ne potential disadvantage is in nearsurface resolution from the more freely resonating transducer in direct contact testing. Thisparticular transducer manufacturing technique is of special relevance as it establishes the base

line for phased array transducer construction and %avefront equivalencies.

2.# (ingle element transducer characteri)ation

&ltrasonic transducers for >7T %ill normally be characteri)ed by their manufacturers inaccordance %ith industry standard procedures such as A(TB :10$#. Typically the transducerEssensitivity9 %aveform shape9 and frequency spectrum %ill be tested and recorded underdocumented conditions. A typical transducer characteri)ation form is seen belo%.

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2.$ Inside a phased array transducer

!hile phased array transducers come in a %ide range of si)es9 shapes9 frequencies9 andnumber of elements9 %hat they all have in common is a pie)oelectric element that has been

divided into a number of segments.

'ontemporary phased array transducers for industrial >7T applications are typicallyconstructed around pie)ocomposite materials9 %hich are made up of many tiny9 thin rods ofpie)oelectric ceramic embedded in a polymer matri8. !hile they can be more challenging tomanufacture9 composite transducers typically offer a 10 to 30 d/ sensitivity advantage overpie)oceramic transducers of other%ise similar design. (egmented metal plating is used to dividethe composite strip into a number of electrically separate elements that can be pulsedindividually. This segmented element is then incorporated into a transducer assembly thatincludes a protective matching layer9 a bac6ing9 cable connections9 and an overall housing.

The animation above depicts a linear array9 %ith a rectangular footprint9 %hich is a very commonconfiguration for a phased array. Arrays can be arranged as a matri8 to provide more beamcontrol over a surface cross section9 or as circular arrays %hich provides a more sphericalfocusing pattern.

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2.* +hased array transducer characteristics

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+hased array transducers are functionally categori)ed according to the follo%ing basicparametersC

Type Bost phased array transducers are angle beam type9 designed for use %ith either aplastic %edge or a straight plastic shoe )ero degree %edge4 or delay line. 7irect contact andimmersion transducers are also available.

Frequency Bost ultrasonic fla% detection is done bet%een 2 B=) and 10 B=)9 so mostphased array transducers fall %ithin that range. o%er and higher frequency probes are alsoavailable. As %ith conventional transducers9 penetration increases %ith lo%er frequency9 %hileresolution and focal sharpness increase %ith higher frequency.

!um"er of elements +hased array transducers most commonly have from 1$ to 12,elements9 %ith some having as many as 2#$. A larger number of elements increases focusingand steering capability9 and can increase area coverage as %ell9 but also increases both probeand instrumentation costs. :ach of these elements is individually pulsed to create the %avefront

of interest. =ence the dimension across these elements is often referred to as the active orsteering direction.

Si#e of elements As element %idth gets smaller9 beam steering capability increases9 but largearea coverage %ill require more elements at higher cost.

The dimensional parameters of a phased array are customarily defined as follows

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This information is use by instrument soft%are to generate the desired beam shape. If it is notentered automatically by probe recognition soft%are9 then it must be entered by the user duringsetup.

2., +hased array %edges

In addition to the array transducer itself9 phased array probe assemblies usually also include aplastic %edge. !edges are used in both shear %ave and longitudinal %ave applications9including straight beam linear scans. These %edges perform basically the same function inphased array systems as in conventional single element fla% detection9 coupling sound energyfrom the transducer to the test piece in such a %ay that it mode converts and<or refracts at adesired angle in accordance %ith (nellEs a%. !hile phased array systems do utili)e beamsteering to create beams at multiple angles from a single %edge9 this refraction effect is alsopart of the beam generation process. (hear %ave %edges loo6 very similar to those used %ithconventional transducers9 and li6e conventional %edges they come in many si)es and styles.

(ome of them incorporate couplant feed holes for scanning applications. A typical phased array%edge is seen belo%.

ero degree %edges are basically flat plastic bloc6s that are used for coupling sound energyand for protecting the transducer face from scratches or abrasion4 in straight linear scans and

also for lo% angle longitudinal %ave angled scans.

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!edges can also be custom contoured to accommodate comple8 part geometries. There areseveral %edge dimensions in addition to incident angle that are used in programming phasedarray scans9 to insure proper distance and depth calibration as %ell as proper refracted angle.These parameters %ill be listed in the manufacturerEs %edge documentation and should berecorded for reference.

2.- +hased array pulsing and its effects

!henever %aves originating from t%o or more sources interact %ith each other9 there %ill bephasing effects leading to an increase or decrease in %ave energy at the point of combination.!hen elastic %aves of the same frequency meet in such a %ay that their displacements areprecisely synchroni)ed in phase9 or 0 degree phase angle49 the %ave energies %ill add togetherto create a larger amplitude %ave. If they meet in such a %ay that their displacements aree8actly opposite 1,0 degrees out of phase49 then the %ave energies %ill cancel each other. At

phase angles bet%een 0 degrees and 1,0 degrees9 there %ill be a range of intermediate stagesbet%een full addition and full cancellation. By varying the timing of the waves from a largenum"er of sources$ it is possi"le to use these effects to "oth steer and focus theresulting com"ined wave front% This is an essential principle behind phased array testing.

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In conventional transducers9 constructive and destructive interference effects create the nearfield and far field )ones and the various pressure gradients therein. Additionally9 a conventionalangle beam transducer uses a single element to launch a %ave in a %edge. +oints on this %avefront e8perience different delay intervals due to the shape of the %edge. These are mechanicaldelays9 as opposed to the electronic delays employed in phased array testing. !hen the %avefront hits the bottom surface it can be visuali)ed through =uygenEs +rinciple as a series of pointsources. The theoretically spherical %aves from each of these points interact to form a single%ave from at an angle determined by (nellEs a%.

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In phased array testing9 the predictable reinforcement and cancellation effects caused byphasing are used to shape and steer the ultrasonic beam. +ulsing individual elements or groupsof elements %ith different delays creates a series of point source %aves that %ill combine into asingle %ave front that %ill travel at a selected angle. This electronic effect is similar to themechanical delay generated by a conventional %edge9 but it can be further steered by changingthe pattern of delays. Through constructive interference9 the amplitude of this combined %avecan be considerably greater than the amplitude of any one of the individual %aves that produceit. (imilarly9 variable delays are applied to the echoes received by each element of the array tosum the responses in such a %ay as to represent a single angular and<or focal component ofthe total beam. In addition to altering the direction of the primary %ave front9 this combination of

individual beam components allo%s beam focusing at any point in the near field.

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:lements are usually pulsed in groups of to 32 in order to improve effective sensitivity by

increasing aperture9 %hich reduces un%anted beam spreading and enables sharper focusing.

The returning echoes are received by the various elements or groups of elements and timeshifted as necessary to compensate for varying %edge delays and then summed. &nli6e aconventional single element transducer9 %hich %ill effectively merge the effects of all beamcomponents that stri6e its area9 a phased array transducer can spatially sort the returning%avefront according to the arrival time and amplitude at each element. !hen processed byinstrument soft%are9 each returned focal la% represents the reflection from a particular angularcomponent of the beam9 a particular point along a linear path9 and<or a reflection from aparticular focal depth. The echo information can then be displayed in any of several standardformats.

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2.10 ocal la% sequencing

As noted previously9 phased array beams are generated by pulsing the individual probeelements or groups of elements in a particular pattern. +hased array instruments %ill generatethese patterns based on information that has been entered by the user.

(oft%are 6no%n as a focal la% calculator establishes specific delay times for firing each group ofelements in order to generate the desired beam shape through %ave interaction9 ta6ing intoaccount probe and %edge characteristics as %ell as the geometry and acoustical properties ofthe test material. The programmed pulsing sequence selected by the instrumentEs operatingsoft%are then launches a number of individual %ave fronts in the test material. These %avefronts in turn combine constructively and destructively into a single primary %ave front thattravels through the test material and reflects off crac6s9 discontinuities9 bac6 %alls9 and othermaterial boundaries li6e any conventional ultrasonic %ave. The beam can be dynamicallysteered through various angles9 focal distances9 and focal spot si)es in such a %ay that a singleprobe assembly is capable of e8amining the test material across a range of differentperspectives. This beam steering happens very quic6ly9 so that a scan from multiple angles or%ith multiple focal depths can be performed in a small fraction of a second.

2.11 /eam shaping

The response of any ultrasonic test system is a combination of factorsC the transducer used9 thetype of instrument used and its settings9 and the acoustic properties of the test material. Theresponses produced by phased array transducers9 li6e those from any other ultrasonictransducers for >7T9 %ill be related both to transducer design parameters li6e frequency9 si)e9and mechanical damping9 and to the parameters of the e8citation pulse that is used to drive it.

our important transducer parameters %ill have a number of interrelated effects on

performance.

Frequency As noted in the previous section9 the test frequency has a significant effect on nearfield length and beam spreading. In practice9 higher frequencies can provide better signal tonoise ratio than lo%er frequencies since they offer potentially sharper focusing and thus atighter9 more optimi)ed focal spot. At the same time9 penetration in any test material %illdecrease %ith frequency because of increasing material attenuation as frequency goes up.

Applications involving very long sound paths or test materials that are highly attenuating orscattering %ill require use of lo%er frequencies. 'ommonly9 industrial phased array probes areoffered %ith frequencies bet%en1 B=) and 1# B=).

&lement si#e As the si)e of individual elements in an array decreases9 its beam steeringcapability increases. The minimum practical element si)e in commercial probes is typicallyaround 0.2 mm. =o%ever if the element si)e is less than one %avelength9 strong un%anted sidelobes %ill occur.

!um"er of elements As the number of elements in an array increases9 so can the physicalcoverage area of the probe and its sensitivity9 focusing capability9 and steering capability. At thesame time9 use of large arrays must often be balanced against issues of system comple8ity andcost.

'itch and aperture +itch is the distance bet%een individual elements9 aperture is the effective

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counterpart.

or phased array transducers > elements are grouped together to form the effective aperturefor %hich beam spread can be appro8imated by conventional transducer models.

or phased array transducers9 the ma8imum steering angle at $ d/4 in a given case is derivedfrom the beam spread equation. It can be easily seen that small elements have more beamspreading and hence higher angular energy content9 %hich can be combined to ma8imi)esteering. As element si)e decreases9 more elements must be pulsed together to maintainsensitivity.

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;ecalling that the practical limit for phased array transducer manufacturing restricts the smallestindividual element %idth to 0.2 mm9 the active aperture for a 1$ element probe %ith 0.2 mmelements %ould be 3.2 mm. 'reating an aperture of $. mm %ould require 32 elements. !hilethese transducers %ould no doubt ma8imi)e steering9 the small apertures %ould limit staticcoverage area9 sensitivity9 and focussing ability.

The steering range can be further modified by using an angled %edge to change the incidentangle of the sound beam independently of electronic steering.

2.13 Grating lobes and side lobes

Hbulos principales y lHbulos secundarios

Another phenomenon associated %ith phased array probes is the generation of un%antedgrating lobes or side lobes9 t%o closely related phenomena caused by sound energy thatspreads out from the transducer at angles other than the primary path. This phenomenon is notlimited to phased array systems un%anted lobes also occur %ith conventional transducers aselement si)e increases. These un%anted ray paths can reflect off surfaces in the test piece andcause spurious indications on an image. The amplitude of grating lobes is significantly affectedby pitch si)e9 the number of elements9 frequency9 and band%idth. The beam profiles belo%compare t%o situations %here the probe aperture is appro8imately the same9 but the beam atleft is generated by si8 elements at 0. mm pitch and the beam at right by three elements at 1mm pitch. The beam at left is appro8imately shaped as a cone9 %hile the beam at right has t%ospurious lobes at appro8imately a 30 degree angle to the center a8is of the beam.

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Grating lobes %ill occur %henever the si)e of individual elements in an array is equal to orgreater than the %avelength9 and there %ill be no grating lobes %hen element si)e is smallerthan half a %avelength. or element si)es bet%een one half and one %avelength9 thegeneration of grating lobes %ill depend on the steering angle.4 Thus the simplest %ay tominimi)e grating lobes in a given application is to use a transducer %ith a small pitch.(peciali)ed transducer design incorporating subdicing cutting elements into smaller elements4and varying element spacing %ill also reduce un%anted lobes.

2.1 ocusing %ith phased array probes

rom the beam spread angle9 the beam diameter at any distance from the transducer can becalculated. In the case of a square or rectangular phased array transducer9 beam spreading inthe passive plane %ill be similar to that of an unfocused transducer. In the steered or activeplane9 the beam can be electronically focused to converge acoustic energy at a desired depth.!ith a focused transducer9 the beam profile can typically be represented by a tapering cone or%edge in the case of single a8is focusing4 that converges to a focal point and then diverges atan equal angle beyond the focal point9 li6e thisC

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reflected by a small fla%. The $ d/ beam diameter of a focused transducer at the focal pointcan be calculated as follo%sC

rom these formulas it can be seen that as the element diameter and<or frequency increase9 thebeam spread angle decreases. A smaller beam spread angle in turn can result in highereffective sensitivity in the far field )one since the beam energy dissipates more slo%ly. ! ithin itsnear field9 a transducer can be focused to create a beam the converges rather than diverges.>arro%ing the beam diameter to a focal point increases sound energy per unit area %ithin thefocal )one and thus increasing sensitivity to small reflectors. 'onventional transducers usuallydo this %ith a refractive acoustic lens9 %hile phased arrays do it electronically by means ofphased pulsing and the resulting beam shaping effects.

In the case of the most commonly used linear and square phased arrays %ith rectangularelements9 the beam %ill be focused in the steering direction and unfocused in the passivedirection. Increasing the aperture si)e increases the sharpness of the focused beam9 as can beseen in these beam profiles. ;ed areas correspond to the highest sound pressure9 and blueareas to lo%er sound pressure.

2.1# +hased array probe selection summary

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7esigning phased array probes is al%ays a compromise bet%een selecting the proper pitch9element %idth and aperture. &sing a high number of small elements to increase steering9reduce side lobes and provide focusing but can be limited by cost of manufacturing andinstrument comple8ity. Bost standard instruments %ill support apertures of up to 1$ elements.(eparating elements greater distances may seem the easy %ay to gaining aperture si)e9 butthis creates un%anted grating lobes.

It is important to note that vendors of phased array transducers often offer standard probes thathave been designed %ith these compromises in mind9 resulting in optimi)ed performance for theintended use. Actual transducer selection %ill ultimately be driven by the end application needs.In some cases multi angle steering %ill be required over small metal paths so large aperturesi)es are not needed or desired. In other cases the application may be to cover large areas forlaminar defects %ill require large apertures and linear scan format %ith multiple groupedelements %here steering is not required at all. In general9 the user can apply best practice fromtheir conventional &T 6no%ledge for frequency and aperture selection.

The graphic belo% is a lin6 to the 5lympus >7T phased array probe catalog. 'lic6 on it to vie%the full selection of probes and %edges that is available.

3.0 Imaging /asics

3.1 Introduction

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+rincipios de base de la creaciHn deim genesC IntroducciHn

/oth conventional and phased array ultrasonic instruments utili)e high frequency sound %avesto chec6 the internal structure of a test piece or measure its thic6ness9 and both rely on thesame basic la%s of physics that govern sound %ave propagation. (imilar concepts areemployed in both ultrasonic technologies to present ultrasonic data.

'onventional ultrasonic instruments for >7T commonly consist of either a single active elementthat both generates and receives high frequency sound %aves9 or t%o paired elements9 one fortransmitting and one for receiving. A typical instrument consists of a single channel pulser andreceiver generates and receives an ultrasonic signal9 %ith an integrated digital acquisition

system %hich is coordinated %ith an onboard display and measurement module. In moreadvanced units multiple pulser receiver channels can be used %ith a group of transducers toincrease )one of coverage for evaluating different depths or fla% orientations and can furtherprovide alarm outputs. In more advanced systems9 conventional ultrasonics can be integrated%ith positional encoders9 controllers and soft%are as part of an imaging system.

+hased array instruments9 on the other hand9 are naturally multi channel as they need toprovide e8citation patterns focal la%s4 to transducer assemblies %ith from 1$ to as many as2#$ elements. &nli6e conventional fla% detectors9 phased array systems can s%eep a soundbeam from one probe through a range of refracted angles9 along a linear path9 or dynamicallyfocus at a number of different depths9 thus increasing both fle8ibility and capability in inspectionsetups. This added ability to generate multiple transducer paths %ithin one probe adds apo%erful advantage in detection and naturally adds the ability to Jvisuali)eJ an inspection bycreating an image of the inspection )one. +hased array imaging provides the user %ith theability to see relative point to point changes and multi angular defect responses9 %hich canassist in fla% discrimination and si)ing. !hile this may seem inherently comple89 it can actuallysimplify e8panding inspection coverage %ith increased detection by eliminating the comple8fi8tures and multiple transducers that are often required by conventional &T inspectionmethods.

The follo%ing sections %ill further e8plain the basic formats for conventional and phased arraydata presentation.

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3.2 A (can data

Any ultrasonic instrument typically records t%o fundamental parameters of an echoC ho% large itis amplitude49 and %here it occurs in time %ith respect to a )ero point pulse transit time4.Transit time in turn is usually correlated to reflector depth or distance9 based on the soundvelocity of the test material and the simple relationship

7istance K velocity 8 time

The most basic presentation of ultrasonic %aveform data is in the form of an A scan9 or%aveform display9 in %hich echo amplitude and transit time are plotted on a simple grid %ith thevertical a8is representing amplitude and the hori)ontal a8is representing time. The e8amplebelo% sho%s a version %ith a rectified %aveformL unrectified ; displays are also used. The redbar on the screen is a gate that selects a portion of the %ave train for analysis9 typicallymeasurement of echo amplitude and<or depth.

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3.3 (ingle alue / (can

/ scan de valor Mnico

Another %ay of presenting this information is as a (ingle alue / scan. A (ingle alue / scanis commonly used %ith conventional fla% detectors and corrosion thic6ness gages to plot thedepth of reflectors %ith respect to their linear position. The thic6ness is plotted as a function oftime or position %hile the transducer is scanned along the part to provide its depth profile.

'orrelating ultrasonic data %ith actual transducer position allo%s a proportional vie% to beplotted and allo%s the ability to correlate and trac6 data to specific areas of the part beinginspected. This position trac6ing is typically done through the use of electromechanical devices6no%n as encoders. These encoders are used in fi8tures %hich are either manually scanned orin automated systems that move the transducer by a programmable motor controlled scanner.In either case the encoder records the location of each data acquisition %ith respect to a desireduser defined scan pattern and inde8 resolution.

In the case belo%9 the / scan sho%s t%o deep reflectors and one shallo%er reflector9corresponding to the positions of the side drilled holes in the test bloc6.

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3. ' (can mapping

Bapeo ' scan

Another presentation option is a ' scan9 a t%o dimensional presentation of data displayed as a

top or planar vie% of a test piece9 similar in its graphic perspective to an 8 ray image9 %herecolor represents the gated signal amplitude or depth at each point in the test piece mapped toits position. +lanar images can be generated on flat parts by trac6ing data to N position9 or oncylindrical parts by trac6ing a8ial and angular position. or conventional ultrasound9 amechanical scanner %ith encoders is used to trac6 the transducerEs coordinates to the desiredinde8 resolution. The images that follo% conceptually sho% ' scans of a reference bloc6 made%ith a conventional immersion scanning system using a focused immersion transducer.

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3.# +hased array ' (can

' scan phased array

A ' scan from a phased array system is very similar to the one from the conventional probeseen above. !ith phased array systems ho%ever9 the probe is typically moved physically alongone a8is %hile the beam electronically scans along the other according to the focal la%sequence. (ignal amplitude or depth data is collected %ithin gated region of interest @ust as inconventional ' scans. In the case of phased arrays9 data is plotted %ith each focal la%progression9 using the programmed beam aperture.

/elo% is an actual scan of the same test bloc6 sho%ed in the previous section using an

encoded # B=)9 $ elements linear array probe %ith a straight %edge or sho%. :ach focal la%uses 1$ elements to form the aperture9 and at each pulsing the starting element increments by

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one. This results in forty nine data points that are plotted hori)ontally in the image belo%4across the transducerEs 3* mm 1.#J4 length. As the transducer is moved in a straight linefor%ard9 a planar ' scan vie% emerges. :ncoders %ill normally be used %henever precisegeometrical correspondence of the scan image to the part must be maintained9 although nonencoded manual scans can also provide useful information in many cases.

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!hile the graphic resolution is not fully equivalent to the conventional ' scan because of thelarger effective beam si)e9 there are other considerations. The phased array system is fieldportable9 %hich the conventional system is not9 and costs about one third the price. Additionally9the phased array image %as made in a fe% seconds9 %hile the conventional immersion scantoo6 several minutes. ;eal time generation of the ' scan is sho%n belo%.

3.$ 'ross sectional / (can

/ scan de corte transversal

A cross sectional / scan provides a detailed end vie% of a test piece along a single a8is. Thisprovides more information than the single value / scan presented earlier. Instead of plotting @usta single measured value from %ithin a gated region9 the %hole A scan %aveform is digiti)ed ateach transducer location. (uccessive A scans are plotted over elapsed time or actual encoded

transducer position so as to dra% pure cross sections of the scanned line. This allo%svisuali)ation of both near and far surface reflectors %ithin the sample. !ith this technique9 the

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full %aveform data is often stored at each location and may be recalled from the image forfurther evaluation or verification.

To accomplish this9 each digiti)ed point of the %ave form is plotted so that color representingsignal amplitude appears at the proper depth.

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In practice this electronic s%eeping is done in real time so a live cross section can be continuallyvie%ed as the transducer is physically moved. /elo% is a real time image %ith a $ element

inear phased array probe.

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It is alsopossible to scan at a fi8ed angle across elements. As discussed later this is very useful forautomated %eld inspection. &sing a $ element linear phased array probe %ith %edge9 shear%aves can be generated at a user defined angle often #9 $0 or *0 degrees4. !ith aperturesequencing through the length of the probe full volumetric %eld data can be collected %ithoutthe need for physically increasing distance to %eld center line %hile scanning. This provides forsingle pass inspection along the %eld length.

3., +hased array (ectorial scans ( scans4

( scan angular phased array

5f all imaging modes discussed so far9 the (ectorial scan is unique to phased array equipment.In a linear scan9 all focal la%s employed a fi8ed angle %ith sequencing apertures. (ectorialscans9 on the other hand9 use fi8ed apertures and steer through a sequence of angles.

T%o main forms are typically used. The most familiar9 very common in medical imaging9 uses a)ero degree interface %edge or shoe to steer longitudinal %aves at relatively lo% angles9

creating a pie shaped image sho%ing laminar and slightly angled defects.

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The second format employs an angled plastic %edge to increase the incident beam angle forgeneration of shear %aves9 most commonly in the refracted angle range of 30 to *0 degrees.This technique is similar to conventional angle beam inspection9 e8cept that the beam s%eepsthrough a range of angles rather than a @ust single fi8ed angle determined by a %edge. As %iththe linear scan9 the image presentation is a cross sectional picture of the inspected area of thetest piece.

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The actual image generation %or6s on the same stac6ed A scan principle that %as discussed inthe conte8t of the linear scans introduced in the previous section. The end user defines theangle start9 end9 and step resolution to generate the sectorial image. ou %ill notice that theaperture remains constant9 %ith each defined angle generating a corresponding beam %ithcharacteristics defined by aperture9 frequency9 damping and the li6e. The %aveform responsefrom each angle focal la%4 is digiti)ed and plotted related to color at the appropriatecorresponding angle9 building a cross sectional image.

In actuality9 the sectorial scan is produced in real time so as to continually offer dynamicimaging %ith transducer movement. This is very useful for defect visuali)ation and increasesprobability of detection9 especially %ith respect to randomly oriented defects9 as manyinspection angles can be used at once.

3.- 'ombined image formats

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Im genes combinadas

+hased array images are po%erful in their ability to provide real time visuali)ation of volumetric

data. Through the electronic scanning process9 imaging truly becomes real time and is used inboth manual and automated systems to increase probability of detection. :specially inautomated and more capable phased array instruments9 the ability to display multiple imagetypes and store complete ra% %aveform information for the entire inspection allo%s postscanning analysis of the inspection. /ecause all the ultrasonic %aveform data is collected9 thispost analysis enables allo%s reconstruction of sectorial scans 9 ' scan and or / scans %ithcorresponding A scan information at any inspection location. or e8ample9 the screen belo%simultaneously displays the rectified A scan %aveform9 a cross sectional / scan profile9 and a' scan image of a set of reference holes in a steel test bloc6.

3.10 5vervie% of beam effects on sectorial scans

:fectos del ha)C Generalidades

+hased array instruments allo% the operator to program a number of parameters that %ill affectthe shape of the sound beam and in turn the graphic resolution of the resulting images.

The scan images belo% sho% the effect of increasing the virtual aperture of a phased arrayprobe by pulsing the elements in groups. &sing a $ element probe %ith a 0.$ mm 0.02 inch4pitc h9 elements are pulsed in groups of 9 ,9 and 1$ %hile imaging side drilled holes in areference bloc6. The largest aperture 1$ elements4 produces an image that is much sharperthat that produced by the smaller apertures9 and it also gives the highest amplitude responsefrom the target holes. 5f course large apertures can be achieved only %ith probes that have a

large number of elements9 %hich in turn are more e8pensive and typically require moree8pensive instrumentation to drive them.

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i6e aperture and the number of focal la%s9 electronic beam focusing as discussed in (ection 2.1 4 canhave a significant effect on both the sharpness of an image and the amplitude of the reflection from atarget. The scans belo% sho% unfocused left4 and focused right4 # B=) images of three side drilled holesin a steel reference bloc6.

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+erhaps the most fundamental variable affecting graphic resolution is probe selection. =igherfrequency %ill typically offer greater resolution than lo%er frequencies9 %hile lo%er frequencieshave a penetration advantage in applications involving very long sound paths9 or test materialsthat are highly attenuating or scattering. The scans belo% sho% a series of side drilled holes in asteel reference bloc6 imaged %ith a # B=)9 $ element probe left4 and a 2 B=)9 1$ elementprobe right49 in both cases using a 1$ element aperture. The # B=) image is significantlysharper.

The # B=) test does require a higher gain level9 since attenuation in any material increasesproportionally to frequency. =o%ever in most phased array applications system gain is not a

limiting factor.

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.0 +hased Array Instrumentation

.1 5vervie%

There a %ide variety phased array probes commercially available. !hile the linear array probeis certainly the most commonly used configuration9 customi)ed transducers %ith high elementcounts and varying element placements are also available9 often designed to meet demandingapplication needs requiring high speed full volumetric coverage and<or comple8 beam steering.To meet these needs9 there are varying levels of phased array instrumentation no%commercially available in three general classificationsC field portable manual9 field portableautomated9 and rac6 instruments for in line inspection.

.2 Instrument bloc6 diagram

7iagrama del equipo

The fundamental requirement of all phased array instruments is the ability to configure a definedgroup of elements %ith the programmed pulser and reception delays commonly referred to as afocal la%. The instrument forms images by sequencing focal la%s %ith different pulser andreceiver delays across the same aperture9 or multiple8ing the same la% across steppedapertures.

7uring pulsing9 a trigger is sent to a ban6 of pulsers %ith the delay sequence required toachieve the desired beam. At reception9 the signals are digiti)ed and delayed according to afocal la% and summed to form a single ; response. This %aveform is then amplified9 filtered asrequired9 digiti)ed9 processed and stored. As one sequence of focal la%s is being completed9the image is simultaneously displayed along %ith an associated A (can and measurements. Inlinear scanning9 groups of elements are stepped through a multiple8er to reduce cost andelectronic comple8ity. A conceptual overvie% is sho%n belo% in a reduced configurationconsisting of four pulser<receivers e8citing an , element probe. >ote that for sectorial scans thema8imum number of elements that can be used is four.

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.3 Important specifications

.3.1 'onventional instruments

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:specificaciones de los equipos deultrasonidos convencionales

!hen evaluating conventional fla% detectors9 a number of functional characteristics are oftenspecified. These characteristics are generally shared %ith phased array instruments. >ot all ofthe items listed belo% are available in all instruments.

'ulser and Receiver

argely defines the operating range of transducers that can be used %ith the instrument

(easurement and Display

Si#ing )ptions

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A vareity of fla% detection standards and codes have been developed and are in practice forsi)ing a variety of defects. These apply to inspection of %eldments as %ell as to a variety ofmetallic and composite structures. 'ertain inspections require that a specific code be follo%ed.

As a result a variety of tools are no% available in conventional digital fla% detectors to automateand record tools required by these codes.

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!um"er of Receivers !ill define the total number of elements that can be used forsequencing apertures that leads to the potential increase in coverage from a single probefootprint.

++ ,, >aming convention used %here NN K >umber of pulsers and K >umber of receiverpaths. The number of receivers is al%ays greater or equal to number of pulsers. Instrumentsfrom 1$C1$ to 32C12, are available in field portable pac6aging. =igher pulser and receivercombinations are available for in line inspection and<or systems that use larger element countprobes.

Focal -aws The number of focal la%s that can be combined to form an image is oftenspecified. In general9 higher NNC configurations can support more focal la%s as they supportgreater element apertures and<or more aperture stepping in linear scanning. >ote that morefocal la%s does not al%ays mean more functionality. Ta6e the e8ample belo% using a $element probe performing a sectorial scan of three side drilled holes from 0 to *0 degrees9comparing steering %ith 1 degree 30 la%s49 2 degree 1# la%s49 and degree * la%s4 stepsover a 2 inch9 #0 mm metal path. !hile the image %ill be slightly better defined %ith finer angleincrements9 detection at coarser resolution is adequate. &nless beam diameter is drasticallyreduced %ith focusing9 si)ing from images %ill not dramatically change either.

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:8amples for the number of focal la%s required performing linear scans %ith varyingcombinations of virtual probe apertures and total element counts are sho%n belo%.

rom the above9 it is readily apparent that a 1$C1$ configuration used %ith a 1$ elementtransducers may only require 30 la%s %hile a 1$C12, or 32C12, instrument configuration used inlinear scan mode %ith a 12, element transducer may very %ell require 12, focal la%s.

+; <7isplay &pdate ;ateC Instruments can vary greatly in display update in various imagemodes. or phased array imaging modesC

An e8ample of a reduced four focal la% linear scan sequence %ith a $0 =) image display updateis sho%n belo% for conceptuali)ation.

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The actual image display rate may be affected by other parameters. The A scan refresh rate ofa single focal la% %ill vary bet%een instruments. In some instruments9 the A scan +; rate islimited by the ma8imum image display update9 %hether it is sho%n %ith the phased array imageor even %hen ma8imi)ed to a full A scan. or this reason9 in some applications it may beimportant to verify A scan +; %hen derived from focal la% sequence in various image displaymodes.

'ro"e recognition The ability to recogni)e phased array probes reduces operator setup timeby automatically configuring an instrument setup %ith proper number of elements and probegeometry.

*mage types (ectorial and linear scans are typically available in phased array instruments. Theability to stac6 these image modes to create amplitude and depth ' scans allo%s planar imagesto be formed and provides e8panded means for si)ing defects.

Waveform storage The ability to store ra% ; %aveforms allo%s data to be revie%ed off line.This is particularly useful %hen collecting data over a large area.

(ulti. roup support Bore capable phased array instruments allo% multiple focal la% groupsto be sequenced on one or more connected transducers. This is especially useful in cases%here it is important to collect volumetric data %hich %ill be analy)ed off line. or e8ample9 a #B=)9 $ element probe can be programmed to use elements 1 1$ for a 0 to *0 degree sectorscan9 %hile a second group can be used to perform a $0 degree linear scan %ith an aperture of

1$ elements9 stepping by one element over the entire $ element length.

&ncoding There are t%o classes of instruments generally availableC manual and encoded.

A manual phased array instrument %or6s much li6e a conventional fla% detector as it providesreal time data. Along %ith an A scan9 the instrument also sho%s real time ( scan or linear scanimages %hich can aid in detection and discontinuity analysis. The ability to use and visuali)emore than one angle at a time in a test %ould be the main reason for using this type ofinstrument. In some cases li6e crac6 si)ing9 the image can be used as a tool to help si)e crac6depth.

A phased instrument %ith encoder interface merges probe positional data9 probe geometry9 andprogrammed focal la% sequences to allo% top9 end and side vie% images of test specimen. Ininstruments that also store full %aveform data9 images can be reconstructed to provide crosssectional vie%s along the length of the scan or regenerate planar ' scans at various levels.These encoded images allo% for planar si)ing of defects.

Reference 0ursors Instruments %ill provide various cursors that can be used on an image fordirect si)ing. In a sectorial scan9 it is possible to use cursors for measurement of crac6 height.

Appro8imate defect si)e can be measured in encoded linear ' scans as %ell.

.3.3 'alibration and normali)ation methods

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'alibraciHn y normali)aciHn

0ali"ration (ethod The method of calibration for phased array transducers can be varied. As

beam formation relies on variant element delays and groups9 it is important to normali)e theresponse from each focal la%9 to compensate both for element to element sensitivity variationsin the array transducer and for varying %edge attenuation and energy transfer efficiency atdifferent refracted angles. 'alibration of %edge delay and sensitivity over the entire inspectionsequence not only provides clearer image visuali)ation9 but also allo%s measurement and si)ingfrom any focal la%. !hile 5lympus >7T instruments allo% full calibration9 many instruments %illonly allo% calibration of one focal la% at any one time.

T1 /D20 for phased array or si)ing defects9 A scan amplitude techniques using 7A'curves or time corrected gain are common. These methods account for material attenuationeffects and beam spreading by compensating gain levels T'G4 or dra%ing a reference curvebased on same si)e reflector response as a function of distance. As in sensitivity calibrations9some instruments allo%s a T'G to be built at multiple points over all defined focal la%s. In theseinstruments9 the vie% can be s%itched from T'G to 7A' curve at any time. This allo%s use ofsi)ing curves at multiple angles for sectorial scans or at any virtual aperture in linear scans.

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.3. 'ombined phased array and conventional &T instruments

:quipos de tecnologOa combinada

(ome phased array instruments also provide a conventional ultrasonic channel to supportinspections %ith single element transducers. It is important to 6no% ho% this conventionalchannel functions.

'ulser /ecause of the small si)e of phased array elements9 and leveraging the fact thatconstructive interference effects bet%een elements results in higher sensitivity9 phased arraypulsers are typically limited to 100 volts. 5ften vendors use this limited phased array pulser asthe conventional transducer pulser. This can become very limiting in applications involving longsound paths or highly attenuating materials9 especially %hen using frequencies at or belo%2.2#B=).

*mage Support !hile the phased array portion of the instrument supports A scan9 / scan9 'scan9 and sectorial scans9 this does not mean the conventional &T portion of the instrument %illnecessarily incorporate any imaging. Bore capable instruments do allo% cross sectional /scans on a timed basis %ith %aveform storage on the conventional side. (ome also include theability to interface %ith conventional transducers attached to one or t%o a8is encoded scannersto generate actual position related / scans and ' scans respectively. 5f course sectorialscanning is unique to phased array.

In the image belo%9 a combined phased array<conventional instrument is %or6ing inconventional mode. performing a / scan of a corroded pipe %ith a dual element transducer inan encoded hand scanner.

#.0 Anatomy of +hased Array 7isplay

#.1 Anatomy of +hased Array 7isplay

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Anatomy of +hased Array 7isplay

This section provides further insight into ho% phased array images are constructed. In

particular9 it %ill further e8plain required inputs9 and the relationships of the various phased arraydisplay types %ith respect to the actual probe assembly and part being inspected. !e %ill alsoe8plain the typically available A scan vie%s associated %ith the phased array image.

Required 0onsiderations for 'roper *nspection

As discussed previously9 there are many factors that need to be identified in order to properlyperform any ultrasonic inspection. In summary9 there are material specific characteristics andtransducer characteristics needed for calibrating the instrument for a proper inspection.

(aterial

1. elocity of the material being inspected needs to be set in order to properly measuredepth. 'are must be ta6en to select the proper velocity mode longitudinal or shear4. Asyou may recall9 compressional straight beam testing typically uses longitudinal %aves%hile angle beam inspection most often uses shear %ave propagation.

2. +art thic6ness information is typically entered. This is particularly useful in angle beaminspection. It allo%s proper depth measurement relative to the leg number in anglebeam applications.

3. ;adius of curvature should be set considered %hen inspecting non flat parts. Thiscurvature can be algorithmically accounted for to ma6e more accurate depthmeasurements.

Transducer

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1. requency must be 6no%n to allo% for proper pulser parameters and receiver filtersettings.

2. ero 5ffset must be established in order to offset electrical and mechanical delaysresulting from coupling9 matching layer9 cabling and electronic induced delays for properthic6ness readings.

3. Amplitude response from 6no%n reflectors must be set and available for reference inorder to use common amplitude si)ing techniques.

. Angle of sound beam entry into the material being inspected.#. or phased array probes9 the number elements and pitch need to be 6no%n.

Wedge

1. elocity of sound propagation through the %edge2. Incident angle of the %edge.3. /eam inde8 point or front of probe reference.

. irst element height offset for phased array.

In conventional ultrasonic testing9 all of the above steps must be ta6en prior to inspection toachieve proper results. (ince a single element probe has a fi8ed aperture9 the entry angleselection9 )ero offset9 and amplitude calibration are specific to a single transducer ortransducer<%edge combination. :ach time a transducer or its %edge is changed9 a ne%calibration must be performed.

&sing phased array probes9 the user must follo% these same principles. The main advantage ofphased array testing is the ability to change aperture9 focus9 and<or angle dynamically9essentially allo%ing the use of several probes at one time. This imparts the additionalrequirement of e8tending calibration and setup requirements to each phased array transducerstate commonly referred to as a focal la%4. This not only allo%s accurate measurements ofamplitude and depth across the entire programmed focal sequence9 but also provides accurateand enhanced visuali)ation via the natural images that phase array instruments produce.

5ne of the ma@or differences bet%een conventional and phased array inspections occurs inangle beam inspection. !ith conventional &T9 input of an improper %edge angle or material

velocity %ill cause errors in locating the defect9 but basic %ave propagation and hence theresultant A scan4 is not influenced9 as it relies solely on mechanical refraction. or phased arrayho%ever9 proper material and %edge velocities along %ith probe and %edge parameter inputsare required to arrive at the proper focal la%s to electronically steer across the desired refractedangles and to create sensible images. In more capable instruments9 probe recognition utilitiesautomatically transfer critical phased array probe information and use %ell organi)ed libraries tomanage the selection of %edge parameters.

The follo%ing values must normally be entered in order to program a phased array scanC

'ro"e 'arameters requency

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#.3 (traight /eam inear scans

:scaneos lineales con haces rectos

(traight beam linear scans are usually easy to conceptuali)e on a display because the scanimage typically represents a simple cross sectional vie% of the test piece. As described in(ection 3.*9 a phased array system uses electronic scanning along the length of a linear arrayprobe to create a cross sectional profile %ithout moving the transducer. As each focal la% is

sequenced9 the associated A scan is digiti)ed and plotted. (uccessive apertures are Jstac6edJ9creating a live cross sectional vie%. The effect is similar to a / scan presentation created by

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moving a conventional single element transducer across a test piece and storing data atselected intervals.

In practice9 this electronic s%eeping is done in real time so a live part cross section can becontinually vie%ed as the transducer is physically moved. The actual cross section representsthe true depth of reflectors in the material as %ell as the actual position typically relative to thefront of the probe assembly. /elo% is an image of holes in a test bloc6 made %ith a # $ A29$ element # B=) linear phased array probe. The probe has a 0.$mm pitch.

In this e8ample9 the user programmed the focal la% to use 1$ elements to form an aperture andsequenced the starting element increments by one. (o aperture 1 consists of elements 1through1$9 aperture 2 from elements 2 through 1*9 aperture 3 from elements 3 through1,9 andso on. This results in - individual %aveforms that are stac6ed to create the real time crosssectional vie% across the transducerEs length.

The result is an image that clearly sho%s the relative position of the holes %ithin the scan area9along %ith the A scan %aveform from a single selected aperture9 in this case the 2-th apertureout of -9 formed from elements 2- #9 is represented by the user controlled blue cursor. This isthe point at %hich the beam intersects the second hole.

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#. Angled inear (cans

:scaneos lineales con haces angulares

A linear scan can also be programmed at a single fi8ed angle9 much li6e the beam from aconventional single element angle beam transducer. This single angle beam %ill scan acrossthe length of the probe9 allo%ing the user to test a larger %idth of material %ithout moving theprobe. This can cut inspection time9 especially in %eld scanning applications.

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In the e8ample above9 the beam is s%eeping across the test piece at a # degree angle9intercepting each of three holes as it moves. The beam inde8 point9 the point at %hich the soundenergy e8its the %edge9 also moves from left to right in each scan sequence. The A scandisplay at any given moment represents the echo pattern from a given aperture.In any angle scan not involving very thic6 materials9 it is also necessary to consider the actualposition of reflectors that fall beyond the first leg9 the point at %hich the beam first reflects fromthe bottom of the test piece. This is usually a factor in tests involving typical pipes or plates. Inthe case belo%9 as the beam scans from left to right9 the beam component from the center ofthe probe is reflecting off the bottom of the steel plate and hitting the reference hole in thesecond leg.

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The screen display has been set up to sho% by means of the dotted hori)ontal cursors therelative positions of the end of the first leg and the end of the second leg on the image. Thus9this hole indication9 %hich falls bet%een the t%o hori)ontal cursors9 is identified as being in thesecond beam leg. >ote that the depth scale on the left edge of the screen is accurate only forthe first leg. To use the scale beyond that9 a correction must be applied. In the second leg9 it isnecessary to subtract the apparent depth as read off the scale from t%ice the thic6ness of thetest piece to get the true depth of an indication. or e8ample9 in this case the actual depth of thesecond leg indication in the 2# mm thic6 plate is 3, 2 8 2#49 or 12 mm. In the third leg9 it isnecessary to subtract t%ice the thic6ness of the test piece from the apparent depth of theindication to obtain true depth. Bost instruments are able to do this automatically and displaythe result9 as seen in (ection #.$.

#.# ocal a% (equence

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(ecuencia de las leyes focales

This is very similar to the linear scan setup described in (ection #.1 in that the parameters listed

there must be entered9 e8cept that a range of angles must also be selected. All of the otherconsiderations listed in section #.1 apply. Along %ith typical &T settings for pulser9 receiver andmeasurement gate setup9 the user must also set transducer beam and electronic steering focalla%4 characteristics.

Required 3ser inputs

• Baterial elocity• :lement Puantity the number of elements used to form the aperture of the probe4• irst element to be used for scan• The last element in the electronic raster • :lement step defines ho% defined aperture moves across the probe4• The first angle of the scan.• The last angle of the scan.• The increment at %hich angles are to be stepped.• 7esired focus depth9 %hich must be set less than near field length >4 to effectively

cerate a focus

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sound beam e8ists the %edge4 is a fi8ed location for a conventional %edge9 and a moving pointfor phased array %edges. In the case of linear scans9 the beam inde8 point %ill move along thelength of the probe as the scan sequences. In the case of angular sector scans9 differentangular components %ill e8it the %edge at different points.

The screen images belo% sho% the presentation of location information from t%o corner

reflectors in a steel plate9 one from the first leg signal off the bottom corner and one from thesecond leg signal from the top corner9 seen by a probe at the appropriate position.

'onventional fla% detectors normally use the single beam inde8 point of the %edge as thereference from %hich depths and distances are calculated. In this e8ample9 the top line of thefirst display indicates that the bottom reflector is 2# mm in front of the beam inde8 point at adepth of 2# mm9 and that the measured sound path from the beam inde8 point to the reflector is3#.3# mm. The second display indicates that the top reflector is #0 mm in front of the beaminde8 point at the surface depth )ero49 and that the measured sound path from the beam inde8point to the reflector is *0.*1 mm. The first leg versus second leg differentiation is indicated by

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the readouts 1 1 and 1 2 short for Gate 1 eg 1 and Gate 1 eg 2 respectively4 on the lo%erright edge of the screen.

First leg indication from bottom corner.

Second leg indication from top corner.

/ecause the beam inde8 point of a phased array probe is variable9 a common %ay of

referencing fla% position is %ith respect to the front edge of the %edge rather than the /I+. Thefollo%ing dimensions can then be calculated from the beam informationC

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#.* Interpreting (ector (ector

:scaneo sectorial con haces angulares

In the case of s%ept angle sector scans9 interpretation can be more comple8 because of thepossibility of multiple leg signals that have reflected off the bottom and top of the test piece. Inthe first leg the portion of the sound path up through the first bounce off the bottom of the part49the display is a simple cross sectional vie% of a %edge shaped segment of the test piece.=o%ever beyond the first leg9 the display requires more careful interpretation9 as it also does%hen using a conventional fla% detector.

A conventional fla% detector used %ith common angle beam assemblies displays a single angle A scan. Bodern digital instruments %ill use trigonometric calculation based on measured sound

path length and programmed part thic6ness to calculate the reflector depth and surfacedistance. +art geometry may create simultaneous first leg and second leg indications on thescreen9 as seen here in the case belo% %ith a # B=) transducer and a # degree %edge9 %herea portion of the beam reflects off the notch on the bottom of the part and a portion reflectsup%ard and off the upper right corner of the bloc6. eg indicators and distance calculators canthen be used to confirm the position of a reflector.

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In this e8ample %e see three indications from a single probe position as the beam s%eepsthrough a 0 degree to *0 degree scan.

$.0 Typical Applications$.1 ist of current applications notes

Agricultural +roductsield +ortable N; for AgricultureC :nvironmental Puality Assessments

+otential To8ins from Bedical Bari@uana &se

Aluminio Aircraft (6in Inspection %ith +hased Array ateral (canning Automatic astener =ole inspection in Aircraft/au8ite 5re AnalysisC Aluminum Q Associated Impurities'ast Iron Analysis:'A (ubsurface 'orrosion 7etection

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:'A (ubsurface 'rac6 7etection:'A (urface 'rac6 7etection=o% ;ecent =andheld N; 7evelopments Impact +lant /ased Alloy +ositive BaterialIdentification +BI4 TestingIron9 (teel9 Aluminum9 and >on errous 'astingsBeasurement of the ayers in 'lad Betal 'oo6%are

>on Betallic Inclusion Analysis in (teel+hased array :8amination of riction (tir !elds+rocess +ipe (tress 'orrosion 'rac6ing Inspection(crap ;ecycling %ith N; R (ort Bore9 (ort aster9 and Increase our +rofits(cribe Bar6s Inspection %ith >o +aint ;emoval!all Thic6ness Beasurements for Betal 'ans9 'ontainers and :nclosures

+ie)as fundidas'ast Iron Analysis:lastic Bodulus Beasurement=o% ;ecent =andheld N; 7evelopments Impact +lant /ased Alloy +ositive BaterialIdentification +BI4 TestingIron9 (teel9 Aluminum9 and >on errous 'astings

Beasuring >odularity in 'ast IronBeasuring Thic6ness of !a8 Bolds for +recision 'astingsBeasuring !all Thic6ness of Gun 7rilled Betal;emote isual Inspection for Automotive Applications(crap ;ecycling %ith N; R (ort Bore9 (ort aster9 and Increase our +rofits&ltrasonic Inspection of /abbitt /earing iners&ltrasonic Testing in the oundry Industry!all Thic6ness Beasurement of 'ast :ngine /loc6s and 'ylinder /ores

'er mica Application 'onsiderations in (pecifying =igh requency &ltrasonic Transducers'ar 'atalytic 'onverters ;ecycling'rac6ing in 'eramic 7iesel +articulate ilters7etect and I7 Glass 'eramic G'4 Q eaded Glass %ith +ortable N;:lastic Bodulus Beasurement=andheld N; to (tudy Ancient ;oman 7rainage (ystemBeasurements of (ilicone 'oatings on +orcelain =igh oltage InsulatorsBeasuring Thic6ness of !a8 Bolds for +recision 'astings+hase (hift Test for /ond Integrity+ortable G+( N; +rotocols for ield Archaeology+ortable N; Technology for Archaeometry and Authentication and 'onservation of Art 5b@ectsThic6ness Beasurements and la% 7etection of 'eramics

'ompuestos Aircraft 'omposite Inspection %ith 3#;7' ;amp 7amage 'hec6er /ond Testing in 'omposite +o%er ine Insulators'omposite Inspection %ith ;adius !ater /o8:lastic Bodulus BeasurementInspection of 'omposite lat +anels &sing 5mni(canS +AIns pection of 'omposite ;adiiInspection of 'omposite ;oc6et >o))leBulti mode Adhesive /ond Testing>ondestructive /ond Testing for Aircraft 'omposites+hase (hift Test for /ond Integrity(hear !eb /onding Inspection (olution for ! ind Turbine /ladesThic6ness Beasurement of Aerospace 'omposites&ltrasonic +reamplifiers

ibra de vidrio Aircraft 'omposite Inspection %ith 3#;7' ;amp 7amag e 'hec6er

:lastic Bodulus B easurementInspection of 'omposite ;adiiInspection of 'omposite ;oc6et >o))le

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'revice 'orrosion Testing the (ealing (urface of langes7efect (i)ing in +ipeline !elds R ! hat 'an !e ;eally Achieve"7etection and (i)ing Techniques o f I7 'onnected 'rac6ing7etection of =ydrogen Induced 'rac6ing =I'47etermination of 'alcium9 inc9 (ulfur9 and +hosphorus in ubricating 5ils7etermination of (ulfur in =eavy uel 5il9 !ear Be tals and Additives in ubricating 5il

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astener =ole 'rac6 7etection &sing Ad@ustable (lid e +robesatigue 'rac6 7etection in Barine +ropellerse 5re Binerali)ation =eavy Q i ght :lement Analysis

Grain (i)e Analysis in Betals and AlloysGuidelines for Automated &ltrasonic Inspection Austentic !elds==N; Analy)ers for (cree ning 'onsumer Goods for ead +b49 'admium 'd4 and 5therBetals=igh Temperature &ltrasonic Testing=o% ;ecent =andheld N; 7evelopments Impact +lant /ased Alloy +ositive BaterialIdentification +BI4 TestingInspecting Areas 'lose To :dgesInspecting pipeline girth %elds9 both for onshore a nd for offshore useInspection of anding Gear Inspection of Tee ?oint !elds on /ridge BembersInspection 5f Titanium 'astings &sing &ltrasound +hased ArrayInspections of !ind Tur bine Gearbo8es

Iron9 (teel9 Aluminum9 and >on errous 'astingsBanual !eld Inspection (olution %ith the 5mni(can BBeasurement of th e ayers in 'lad Betal 'oo6%areBeasurement of % all thic6ness of steam boile r tubes %ith :BAT transducersBeasuring Internal 58ide (cale in /oiler Tub esBeasuring Betal Thic6ness Through +aintBeasuring >odularity in 'ast IronBeasuring the Puantity of Bagnetic 7ebris &sing the 5lympus 7ebris Tester Beasuring !all Thic6ness of Gun 7rilled BetalBetal 'oils Thic6ness InspectionBining :8cavator (%ing (haft InspectionsBining =eavy :quipment ug or /ore InspectionsBulti mode Adhesive /ond Test ing

>on 7estructive Gold Assay Darat I7>on Betallic Inclusion Analysis in (t eel>ondestructive +recious Betals Assay and Darat I75il !ell 7o%n =ole 7rilling Tool Inspection+hase (hift Test for /ond Integrity+hased Array Inspection of Gears in =eavy :quipment+hased array :8amination of riction (tir ! elds+BI Inspection and Baterial erification for =ot9 In (ervice Testing+ortable N; for Betals AnalysisC 'haracteri)ation of a +rivate / o%ie Dnife 'ollection+rocess +ipe (tress 'orrosion 'rac6ing Inspe ctionPuilt +ac6agingC ining &p an Array o f 5pportunities;educing the edge effects in turbine component inspections using fle8ible printed circuit board

+'/4 based eddy current array probes.;emote isual Inspection for Automotive Applications;ingdo%n Test for /ond Integrity

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(crap ;ecycling %ith N; R (ort Bore9 (ort aster9 and Inc rease our +rofits(cribe Bar6s Inspection %ith >o +aint ;emoval(pot !eld Testing(tress 'orrosion 'rac6 7etection in +ipelines & sing :ddy 'urrent ArrayThe /enefits of =andheld N; for Bedical 7evice ;o=( 'omplianceThic6ness of (mall 7iameter Tubing

Tube and +ipe !eld Inspection &sing 5mni(c anS +ATurbine 7ovetail Inspection &sing :ddy 'urrent Arrays&ltrasonic Inspection of /abbitt /earing iners&ltrasonic +reamplifiers&ltrasonic Testing in the oundry Ind ustry&ltrasonic Thic6ness Beasureme nts of =ot Betals

isual Inspections of +asseng er ?et :ngines!all Thic6ness Beasurement of 'ast :ngin e /loc6s and 'ylinder /ores!all Thic6ness Beasurements for Betal 'ans9 'ontainers and :nclosures!all Thic6ness Beasurements of Betal +ipes and Tubes!all Thic6ness of Turbine /ladesN #000 +ortable N; Analy)er or +etroche mical :lemental Analysis

5res Au Bineralisation Q +N;+hosphate Binerali)ation Q +athfinder :lements;are : arth Analysis %ith the N #000 Bobile N;&ltra +ortable ;are :arth :lement :8 ploration&ranium :8ploration9 +athfinders Q ight :lements

5tros/ond Testing in 'omposite +o%er ine Insulators7etection of 'alcium9 inc9 (ulfur and +hosphorus in ubricating 5ils7etermination of (ulfur in +etroleum +roducts:ffects of ong 'ables in &ltrasonic Testing %ith (ingle :lement Transducers:+;I +7I Pualification of 5lympus >7T la% 7etectors and +robes for &ltrasonic in (ervice:8amination of >uclear +lant 'omponents +7I &T 10C &ltrasonic :8amination of 7issimilarBetal !elds:+;I +7I Pualification of 5lympus >7T la% 7etect ors and +robes for &ltrasonic in (ervice:8amination of >uclear +lant 'omponents +7I &T 1C erritic +iping:+;I +7I Pualification of 5lympus >7T la% 7 etectors and +robes for &ltrasonic in (ervice:8amination of >uclear +lant 'omponents +7I &T 2C Austenitic +ipe !elds:+;I +7I Pualification of 5lympu s >7T la% 7etectors and +robes for &ltrasonic in (ervice:8amination of >uclear +lant 'omponents +7I &T 3C Through !all (i)ing:+;I +7I Pualification of 5lympus >7T la% 7 etectors and +robes for &ltrasonic in (ervice:8amination of >uclear +lant 'o mponents +7I &T ,C !eld 5verlaid (imilar and 7issimilarBetals:valuating >e% Bethods of 7ental :rosion Analys is:valuating (ample +reparation of ( tone ToolsC :ffects of 'leaning on (urface Beasurements

ield +ortable N;7 Q N; for (hale Gas 7rilling :fficiency=andheld N; for Import (afety and /o rder (ecurity for Government Agencies=andheld N; for (hip%rec6sInspections of !ind Turbine Gearbo8es

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:'A (urface 'rac6 7etection:ddy 'urrent !eld InspectionGuidelines for Autom ated &ltrasonic Inspection Austentic !elds=andheld N; for A' 'orrosion +rediction by 'r in 'arbon (teel=and held N; for ight :lements +hosphorus +4 in (teel==N; for = Al6ylation &nits 'orrosion +rediction by ;esiduals in 'arbon (teel

=o% ;ecent =andhel d N; 7evelopments Impact +lant /ased Alloy +ositive BaterialIdentification +BI4 TestingIron9 (teel9 Aluminum9 and >on errous 'astingsBeasurement of the ayers in 'lad Betal 'oo6%areBetal 'oils Thic6ness Inspection>on Betallic Inclusion Analysi s in (teel+rocess +ipe (tress 'orrosion 'rac6ing Inspection(crap ;ecycling %ith N; R (ort Bore9 (ort aster9 and Increase our +rofits(tainless (teel !eld (urface Inspect ion %ith le8ible :ddy 'urrent Array +robes(tress 'orrosion 'rac6 7etection in +ipelines &sing :ddy 'urre nt Array&ltrasonic Inspection of /abbitt /ea ring iners&ltrasonic +reamplifiers

Titanio:'A (urface 'rac6 7etection=o% ;ecent =andheld N; 7evelopments Impact +lant /ased Alloy +ositive BaterialIdentification +BI4 TestingInspection 5f Titanium 'astings &sing &ltrasound + hased Array(crap ;ecycling %ith N; R (ort Bore9 (ort aster9 and Increase our +rofit s

&ranium&ranium :8ploration9 +athfinders Q ight :lements

*.0 Glossary of +hase d Array Terms

Glossary of +hased Array Ter ms

Golsario de t rminos sobre losultrasonidos phased array

2.Scan An ultrasonic %aveform plotted as amplitude %ith respect to time. It may be eitherrectified or unrectified ; 4.

2podi#ation A computer controlled function that applies lo%er e8citation voltage to the outsideelements of an array in order to reduce the amplitude of un%anted side lobes.

2perture In phased array testing 9 the %idth of the transducer element or group of elementspulsed simultaneously.

2#imuthal Scan An alternate term for (ector scan. It is a t% o dimensional vie% of all amplitudeand time or depth data from all focal l a%s of a phased array probe corrected for delay andrefracted angle.

B.Scan A t%o dimensional image of ultrasonic data plotted as r eflector depth or distance %ith

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respect to beam position. / sc ans may be either single value or cross sectional.

B.scan$ single value A t%o dimensional image based on plotting the first or largest reflector%ithin a gate. This format is commonly used in ultrasonic fl a% detectors and advan ced thic6nessgages and it sho%s one reflector at each data point.

B.scan$ cross.sectional A t%o dimensional i mage of ultrasonic data based on full %aveformstorage at each data9 %hich can b e plotted to sho% all reflectors in a cross section rather than

@ust the first or largest. This allo%s visua li)ation of both near and far surface reflectors %ithin thesample.

Bandwidth The portion of the frequency response that falls %ithin speci fied amplitude limits. Inthis conte8t9 it should be noted that typical >7T transducers do not generate sound %aves at asingle pure frequency9 but rather over a range of frequencies centered at the nominal frequencydesignation. The industry standard is to specify this band%idth at the $d/ or half amplitude4point. As a general rule9 broader band%idth results in better near surface and a8ial resolution9%hile narro% band%idth res ults in higher energy output and thus higher sensitivity.

Beam Forming In phased array testing9 generating a sound beam at a partic ular position9angle9 and<or focus through sequential pulsing of the elements of an array transducer.

Beam spread The angle of divergence from the centerline of a sound beam in its far field.

Beam Steering The capability to modify the refracted angle of the sound beam generated by a

phased array probe.'alibration9 %edge delay A procedure that electronically compensates for the different soundpaths ta6en by different beam components in a %edge9 used to normali)e the measure soundpath length to a reflector.

0ali"ration$ sensitivity A procedure that electronically equali)es amplitude response acrossall beam components in a phased array scan. This typically compensates for both element toelement sensitivity variations9 and the varying energy transfer at different refracted angles.

0.Scan A t%o dimensional vie% of ultrasonic amplitude or time<depth data displayed as a top

vie% of the test piece.

Far Field The portion of a sound beam beyond the last on a8is pressure ma8imum. /eamspreading occurs in the far field.

Focal -aws The programmed pattern of time delays applied to pulsing and receiving from theindividual elements of an array transducer in order to steer and<or focus the resulting soundbeam and echo response.

Focus In ultrasonics9 the point at %hich a sound beam converges to minimum diameter and

ma8imum sound pressure9 and beyond %hich the beam diverges.

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rating -o"es (purious components of a sound beam diverging to the sides of the center ofenergy9 caused by even sampling across the probe elements. Grating lobes occur only %ithphased array transducers and are caused by ray components associated %ith the regular9periodic spacing of the small individual elements. (ee also (ide obes.

4uygens5 'rinciple A mathematical model of %ave behavior that states that each point on anadvancing %ave front may be thought of as a point source that launches a ne% spherical %ave9and the resulting unified %ave front is the sum of those individual spherical %aves.

-inear Scan A scan in %hich the acoustic beam moves along the ma@or a8is of the array%ithout any mechanical movement. A single focal la% is multiple8ed across groups of activeelements9 creating either a straight beam or a beam at a single angle that advances the lengthof the probe.

!ear Field The portion of a sound beam bet%een the transducer and the last on a8is soundpressure pea6. Transducers can be focused only in the near field.

'hased 2rray A multi element ultrasonic transducer typically %ith 1$9 329 or $ elements4used to generate steered beams by means of phased pulsing and receiving.

'hasing The interaction of t%o or more %aves of the same frequency but %ith different timedelays9 %hich may result in either constructive or destructive interference.

'itch The separation bet%een individual elements in a phased array transducer.

'lane$ active The orientation parallel to the phased array probe a8is consisting of multipleelements.

'lane$ passive The orientation parallel to the individual transducer element length or probe%idth.

'lane$ steering The orientation in %hich the beam direction is varied for a phased arrayprobe.

'ulse duration The time interval bet%een the point at %hich the leading edge of a %aveformreaches a specified amplitude typically 20 d/ %ith respect to pea64 to the point at %hich thetrailing edge of the %aveform reaches the same amplitude. /roader band%idth typically reducespulse duration %hile narro%er band%idth increases it. +ulse duration is highly dependent onpulser settings.

Resolution$ angular In phased array systems9 the angular resolution is the minimum angularvalue bet%een t%o A scans %here ad@acent defects located at the same depth are individuallyresolvable.

Resolution$ a6ial The minimum depth separation bet%een t%o specified reflectors that permits

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