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Ultraschall-Impulse...gestern, heute undmorgen von KrautkrämerUnser Produktprogramm zurWerkstoffprüfungUniverselle Ultraschallgeräte fürmobilen und stationären Ein-satz; tragbare Ultraschall-Wand-dickenmesser und Härteprüf-geräte; Wirbelstromprüfgeräte;Prüfköpfe, Sonden, Zubehör undAnwendungssoftware für dasGeräteprogramm; automatischePrüfanlagen für Halbzeuge oderBauteile; Dienstleistungen wiekundenspezifische Problemlö-sungen, Schulungen, Service.Und vieles mehr.

Als Spezialist für Ultraschall ha-ben wir stets Impulse gesetzt. ImDialog mit unseren Kunden ver-pflichten wir uns dafür auch inZukunft.

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Cover photoWeld testing on a pipeline using portable flawdetectors from the past and present: theUSK 2 with separate power unit (1956) andthe USM 25 (1999)

Other photos and pictures

p. 38: Zeppelin Silo- und ApparatebauGmbH, Friedrichshafen

p. 42: Bayerische Motoren Werke AG,Munic

p. 46: Published in FACTS (Switzerland)39/1998

all other photos: Krautkrämer

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Published by:

Krautkrämer GmbH & Co. oHGRobert-Bosch-Str. 3 - D-50354 Hür thP.O. Box 1363 - D-50330 HürthTel.: +49-2233-601 0Fax: +49-2233-601 402E-Mail: [email protected]: www.krautkramer.com

Editorial team:

Paul BuschkeUlrich HuhnRoland KierspelBrigitte KrauseHarald NeuhausMonika Reuter

Other authors from Krautkrämer

M. Berke, H.-E. Grefenberg, W. Hansen,U. Hoppenkamps, B. Karbach,T. Pagel, P. Renzel, W. Roggendorf,Dr. W. Roye, U. Schlengermann, S. Schulz,Dr. J. Sommer, Dr. G. Splitt, B. Waldron

Layout

Brigitte KrauseMonika Reuter

Printed by:

der springende punktKommunikation GmbH, Köln

Total distribution: 18.000

No subscription charge. Reproduction mustinclude mention of the source, and a speci-men copy is requested to be sent to oureditorial office.Contributions from readers are welcome.

7/99

Page

50 YEARS OF KRAUTKRÄMER

A word of greeting from the company founders ..................................... 3

A word of greeting from the General Management ................................ 3

TESTING YESTERDAY

The Krautkrämer Story ........................................................................ 4

Reminiscenses of the early years with Krautkrämer .............................. 8

All safe and (ultra)sound, play it safe with ultrasound ......................... 11

TESTING TODAY

News about DM 4 ............................................................................. 16

State of the art in coating thickness measurement ............................ 17

The invasion of the smallest ones ..................................................... 19

Everything about scanners ................................................................ 22

Wall thickness measurement on componentshaving unknown sound velocities....................................................... 23

An ultrasonic instrument for all eventualities ..................................... 24

Tube testing - on a large scale, off-the-peg design .............................. 26

Immersion testing with the UPR family ............................................... 26

TESTING TOMORROW

True or not true? .............................................................................. 28

Quick hardness testing, quick documentation .................................... 29

Array transducers with integrated electronicsfor industrial applications.................................................................. 30

Joined together by welding ................................................................ 33

REPORTS AND OPINIONS

The Krautkrämer training system ....................................................... 36

Probes for the DM 4 ......................................................................... 37

Another step forward in ultrasonic testing.......................................... 38

Steps in ultrasonic testing ................................................................ 39

Service in changing times ................................................................. 40

ECHO PULSES

Checking of resistance spot welds .................................................... 42

Well armed for the year 2000 ........................................................... 43

The Krautkrämer Ultrasonic Booklet .................................................. 44

With small and large calibre .............................................................. 45

Tracking down the holes ................................................................... 46

Nothing but a cheesy story? Luckily a fat profit! ................................. 47

I M P R I N T C O N T E N T S

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A word of greeting from the General ManagementKrautkrämer has shaped the historyof ultrasonic testing in Germany andaround the world from the very begin-ning. The founders of the companyhave focused their product develop-ments on the solution of essentialtest problems, and we are proud ofthe fact that we continue writing this”history of innovations”. Our latestproducts supply impressive proof ofthis.

We are likewise proud of the fact thatwe always apply the technically feasi-ble for the benefit of our customers.This is the reason why we keep up thedialog with our customers in order toincorporate the experiences andideas from the field into the develop-ment of our products and into every-

thing we do. Application lab, sales,service, training courses and informa-tion offered are examples of this, andtheir importance will also determineour future.

Our work was and still is focused onthe quality of our products and on thedialog with our customers. We aresure that the members of our staffwill continue to follow this path in theyears to come. The customer serviceis our highest principle.

Werner DemmigGeneral Manager

A word of greeting from the company founders

We would like to send our greetings tothe Krautkrämer company and congrat-ulate the company on the occasion ofits 50th anniversary.

Thanks are due to the General Man-agement, to all members of the staff,to customers as well as to suppliersand representatives all over theworld, who have so successfully con-tinued to manage and support thecompany founded by us. We wouldalso like to send our greetings tothose who have retired and who intheir time were comrades-in-arms foran increased safety through ultrason-ic testing, and who transmitted knowl-edge and motivation.

We wish everybody a lot of creativity,every success in new markets, and asound profit line for the future!

Josef KrautkrämerDr. rer.nat. habil.Dr.-Ing. h.c.

Herbert KrautkrämerDr. rer.nat.Honorary senator at the WHU(Wissenschaftliche Hochschule fürUnternehmensführung / ScientificCollege for Business Management)

50 Y E A R S O F K R A U T K R Ä M E R

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T E S T I N G Y E S T E R D A Y

The way it all began.

The Krautkrämer Story

The legendary garageThe history of Krautkrämer begins – asso often in those days - in a garage. It’sthe year 1946: The university of Co-logne, where Dr. Josef Krautkrämer islecturer and Herber t Krautkrämer astudent, is in ruins. The two brotherswant to try and earn some money un-til the university reopens – naturallywith something they know how to dobest: physics. So they hire a garage,set up a laboratory in it, and nail asign beside the door: Dr. Josef andHerber t Krautkrämer, Company forElectrophysics. They hope to get afew orders for the repair or develop-ment of all types of physical measur-ing instruments.

The challengeOne day they are faced with problemsof a different type from industry: theKrupp-WIDIA company is looking for anondestructive test method thatwould help reduce the reject rate oftheir products. This concerns wiredrawing dies made of metal carbidewhich in many cases show blowholesand pores just underneath the materi-al sur face. As these defects are notrevealed till the grinding process, thework done here is quite uneconomicinvolving a lot of wasted time. How isit possible to detect such materialflaws before any further processing ofthe components? X-rays are not suit-able anyhow, they’re no use for de-

tecting even the largest accumulationof pores.

Clearly, this is a challenge for passion-ate physicists like the two Krautkrämerbrothers. Their answer: the develop-ment of an ultrasonic instrument thatoperates according to the through-transmission method - a principlewhich, though already described inscientific publications, had not yetbeen applied successfully in field con-ditions. However it works, but is notthe thing needed because the teststake by far too long. It’s only a sort of”warm-up round” in ultrasonics, thereal breakthrough is yet to come.

1949: the first ”real”Krautkrämer instrumentWe’re in 1949. The Krautkrämerbrothers have discovered the fasci-nating world of echoes as they havefurther developed their idea and builtan ultrasonic flaw detector in whichthe ultrasonic signals transmitted intothe component are displayed on anoscilloscope. It’s true that this instru-ment does not solve the actual prob-lem because, due to unsufficient res-olution, it cannot deliver proof of thedetected porosity just below the sur-face. It’s also true that the disap-pointed customer therefore shelvesthis new development. It’s likewisetrue that this took a good bit of windout of Josef and Herbert Krautkrämer’s

sails since they had used the advancemoney paid but not carried out the or-der. But they did develop an instrumentable to do something else, viz. to non-destructively detect material flaws incomponents made of steel. Nobody atthat time had the slightest idea of thepossibilities opened up by this ”blackbox”.

Not even the Krautkrämer brothersthemselves, although they are con-vinced of their own development. InAugust 1949, a meeting of the VereinDeutscher Eisenhüttenleute - Associa-tion of German Ironworkers – takesplace in Düsseldorf, on which occasionthey aim to present their meanwhile ad-vanced ultrasonic flaw detector – thefirst German instrument of this type,and already a typical ”Krautkrämerproduct” with all the bits and pieces,that means with all the features point-ing the way ahead for the later develop-ment: highly sensitive, high resolution,display of flaws measuring only onemillimeter at a depth of less than tenmillimeters (radio-frequency displaywith a 50-millimeter range), pulse rep-etition frequency up to 1000 Hertz,and portable with its weight of around20 kilograms.

This makes 1949 the year when the ultra-sonic flaw detectors from Krautkrämerwere born.

The beginning of a wonderful(business) friendshipA few hundred people are present atthe meeting in Düsseldor f when JosefKrautkrämer begins to read his papertitled Nondestructive Ultrasonic Test-ing. Herbert Krautkrämer operatesthe projector. When the lights areswitched on again after the per for-mance, only three members of thewhole audience are left. One of themis the head of quality assurance atthe Federal German Railways.

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The people at the German Rail are in-terested. They have a few problemswith their surviving cars and enginesafter 1945. The readiness for serviceis not guaranteed, axle breakage andrail failures are to be expected. X-raydevices, whose introduction has beenpromoted by the German Rail itself, arenot available. In addition, this newmethod presented by Josef and HerbertKrautkrämer involves other promisingpossibilities for easy field application.The German Rail is very soon to beone of the first and, all through theKrautkrämer history, one of the com-pany’s most important customers.

Starting offFor the time being, however, theKrautkrämer brothers are unceasinglytraveling around everywhere in order todemonstrate the usefulness of their de-velopment on site. And it works: it ispossible to use ultrasonics to demon-strate whether there are materialflaws inside a component or not. Ev-ery time a component is identified asdefective using ultrasonics, the de-fect becomes a fact when the work-piece is subsequently cut open. It isthen that another step towards con-vincing people has been taken. Some-times there are discussions as towhether an expensive componentshould really be destroyed in order toconfirm the defect, sometimes ittakes hours until the componentbreaks apart; but the tests are alwayssuccessful.

The ultrasonic instruments are beingcontinuously improved along with theexperiences gathered in the field; or-ders also star t to come in slowly butcontinuously. From January 1951 on-ward, all engines belonging to GermanRail are tested using Krautkrämerequipment; a number of more or lessimportant cracks are detected in theaxles in this connection. Express trainservices can now be continued with-out risks thanks to ultrasonic testing.

A truly portable USIP

left: Axle testing atthe Federal German Railways

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From the garageon tour around the worldThe feeling of starting off changesinto euphoria. Since the university ofCologne has reopened, Dr. JosefKrautkrämer continues his teachingactivities, and Herbert Krautkrämercompletes his studies of physics.They commute between the universityand the garage which is still the com-pany’s headquarters. In the mean-time, this place has become a well-known meeting point for students ofphysics who are infected by the enthusi-asm and become both cheap and effec-tive helpers. At the same time, the com-pany’s activities expand. In 1952, thepoint is reached when the first two em-ployees are hired: Dr. Ludwig Niklasand Dr. Werner Grabendör fer, both ofthem likewise physicists and formKrautkrämer’s first department ”Re-search and Development”. Not thatwe could speak here of any specializedjobs: everybody is still doing every-thing. The first foreign representatives’

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offices of the young company are like-wise already founded in Belgium andFrance in the early 50’s. Representa-tives in almost all European countriesand in numerous countries outsideEurope are added to this during theyears that follow. The triumphal marchof Krautkrämer test equipment aroundthe world cannot be stopped. ”You thinkyou’re the driving force, and it’s youwho are driven by the continuouslygrowing demand from all corners ofthe world” – that’s how Dr. Josef andDr. Herber t Krautkrämer put it 20years later.

Another trade mark:the transfer of know-howWith all the worldwide activities, salesfigures shooting up, growing numberof employees and building activitiesstarting from the mid fifties: from thevery beginning, Krautkrämer is notonly interested in products and in theimplementation of the technically fea-sible. The inspector or test operatorand his experience as well as theknowledge acquired in the field are al-ways incorporated into the work.Looking at it the other way round, it’salso par t of the company’s philoso-phy to impart company know-how tothe inspector. The fact is that the firstmajor successes of ultrasonic tech-nology established that in his workthe user profits from his knowledge ofthe theory of test methods and of theway to handle the equipment. Conse-quently, the first of the monthly trainingcourses titled Introduction to UltrasonicTest Methods is held in the new build-ing on the Luxemburger Strasse in Co-logne’s city quarter Klettenberg as ear-ly as in 1955. Many thousand will fol-low. The participants come from all eco-nomic sectors. Starting from 1956, thecustomer magazine the echo is pub-lished, a forum that has always been,and still is, aimed at presenting sub-stantiated information from the ultra-sonic world. Moreover, a forum thathas accompanied us – also as athank-you to our customers - through50 years of Krautkrämer history.

Up to this very day.

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Reminiscenses of the early yearswith KrautkrämerC. D. Wells, Wells Krautkramer, Great BritainI first became involved with ultrasonictesting in 1952, using Krautkrämerequipment (an USIP 9) about 1954/55.My association with the Krautkrämercompany started in 1957 and so I wasvery much involved in those early pio-neering days. It was pioneering in thesense that it was a completely newtechnology, relatively unknown in in-dustry and often referred to as a“black ar t”. We were all very busy atthat time speaking at seminars, con-ferences and running training coursesas part of the process - “to spreadthe word”.

In those early years a demonstrationof the equipment at a potential cus-tomer, had to start with an explana-tion of ultrasound, piezoelectricityand the two axes of an oscilloscope,before showing its capacity on somefaulty specimens. Those were the ear-ly days of television and to see asmall CRT on a factory floor invariablydrew a small crowd and some wise-crack such as “What won the 3’0clock race today?”!!!

Covering the whole spread of industrywith site work and representation forKrautkrämer, raised many testing andoften fundamental questions and Iwas a frequent visitor to Köln. I foundit a great strength to be able to go tothis “fount of ultrasonic knowledge”with my problems. Having dealt withthe commercial business at the offic-es in the Luxemburger Straße we invari-ably visited “Works II” fur ther downthe road, the restaurant Unkelbach,and there together with one of the DrsKrautkrämer, or Niklas or Grabendör ferwould try to solve the latest technicalproblem, leaving all our technical se-crets scribbled on the paper tableserviette!!

In December 1959 I went with JosefKrautkrämer to the institute of Phys-ics in London, where he gave the firstrepresentation of his paper on the DGS(AVG) diagrams for the variation of am-plitude with distance from disc shapedreflectors. The amplitude was mea-sured for the first time in Decibels andthis was also the introduction of the cal-ibrated attenuator to ultrasonic testing.This original work took the “black art”out of echo amplitude and gave ultra-sonic testing a clear amplitude refer-ence unit which was adopted immedi-ately by all the workers in this field. Ibelieve that this was the most impor-tant milestone we have seen in the his-tory of ultrasonic testing.

Those were the days, as the oldieswould say, they cer tainly have givenme many happy memories, lifelongfriends, and I feel privileged to havebeen a part of that “historical” periodof ultrasonic testing, which was syn-onymous with the name Krautkrämer.

The Krautkrämer staff in 1969 with C. D. Wells (first row, the sixth from the right).At the far right, Dr. Josef and Dr. Herbert Krautkrämer.

Yoji Kobayashi, Krautkramer Japan

My first contact with Krautkrämer hap-pened in 1963. At that time I wasworking with a German trading firm inJapan and responsible for importedNDT-products. X-Ray and Eddy Currentinstruments were well known even atthat time, but Ultrasonics was a less-er known factor. Of course, I did notknow anything about this method -and was sent to Germany to gettrained at this company. I remember

Dr. Herbert Krautkrämer being dis-pleased with my non-professionalquestions....

All parties had to learn from each oth-er. Krautkrämer had to learn that thevoltage in Japan was 100 Volt - not115 Volt as in America, or 220 Volt asin Germany - and I had to learn, whatultrasonic testing of materials was allabout.

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Back in Japan I was sent to carry outdemonstrations with the heavy,mains-operated best seller USIP 10.Once I had five of these instrumentsin the boot of my car, when somebodyhit the rear and seriously damaged mycar. The outcome of this story wasthat I had to demonstrate and give in-formation to the police at their head-quarters in Tokyo. Needless to say, upuntil now we have not received any in-strument orders from them...

In 1971 I founded my own company,Krautkrämer Japan Ltd., thanks to thekind understanding and support of

many people at Krautkrämer. Thiscompany now exists for also almost30 years - so as you can see this is apartnership which has been goingsteady for quite some time!

Now I am preparing to join the“Krautkrämer old boys club”. I trustthat the younger generation will fur-ther develop the next half century ofKrautkrämer’s successful history.

Manfred Müller, Krautkramer Forster Española, Spain

The first time I had contact withKrautkrämer was in 1963 – I was incharge of destructive and nondestruc-tive testing at Siaisa in Madrid at thattime. Having demonstrated Krautkrämerinstruments at several customers forsome years, I received the offer to set upa Spanish branch office for Krautkrämerin 1966. That’s the way KrautkramerEspañola was established in the mid-dle of the year 1966.

The first years were very much charac-terized by travelling; we were constantlyaway on business dealing with ultrason-ics. One week ”on the road” at the cus-tomers, one week in Madrid to do thework there – that was the rhythm of ourlife. Free weekends? A rarity.

Nevertheless, we were successful inour operations. The business devel-oped continuously, and in 1971, we

took over representations of other Ger-man companies – for example, of theinstitute Dr. Förster in Reutlingen andthe Tiede GmbH in Aalen. In the courseof this, the name of our company wasalso changed to Krautkramer ForsterEspañola. The staff also grew along. Atthe beginning, the team consisted ofthree persons - a service electronician,a secretary and myself; in 1997, wehad come so far that our staff num-bered 20 persons.

We managed to achieve this boomthanks to our consistent customer-ori-ented work: individual problem solu-tions and a good after-sales service forour customers were always in the cen-tre of our attention. We have achieved inour country that the name Krautkrämeror Krautkramer Forster Española cameto be identified with the term ultrasonictesting (just as stock-cubes and Maggiwere at that time...). What more couldone wish for the image of a company?

Stand at a fair in Madrid in 1967:Manfred Müller (center) talking with theMinister of Industry, Mr. Lopez Bravo.

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Rudolf Brutsaert, the Brutsaert company, BelgiumThe companies Brutsaert andKrautkrämer are united by a really longhistory. It must have been in 1951 whenmy father heard of Krautkrämer for thefirst time – to be more precise, the occa-sion was a contact with a German manu-facturer of medical instruments: thismanufacturer had just received an orderfrom Dr. Josef Krautkrämer to make aseries of printed circuit boards for an ”in-dustrial ultrasonic instrument”. I remem-ber that my father talked about it athome and that he thought about possi-bly accepting the representation of thisinstrument – whatever it might exactlybe - in Belgium. A little later, all uncer-tainties as to the type and significanceof this ultrasonic instrument were dis-pelled; and as early as in 1952, the offi-cial cooperation between Brutsaert andKrautkrämer started.

This decision turned out to be just theright one soon enough. The break-through with the new method was al-ready achieved with one of the first cus-tomers – the Kuhlmann chemicalworks. All of a sudden, it was possibleto measure wall thicknesses on sulphu-ric acid cisterns nondestructively andquickly! As this news very soon reachedthe customer‘s headquarters in Paris,the future of Brutsaert was sealed: allother activities were stopped, ultrason-ic testing was immediately in the centreof attention. And so it came that a lot ofpioneer work was done in Belgium andFrance in the years that followed.

This shows that Brutsaert was ”oneof the party” to make the ultrasonicmethod known and to disseminate itin Europe almost right from the begin-ning - and thus likewise looks back onalmost 50 years of company history.

left: Rudolf Brutsaertin the fall of 1960 on theSeverin bridge in Cologne.

below: Rudolf Brutsaert,this time without hair,approx. 1970,at Krautkr mer inCologne-Klettenberg

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All safe and (ultra)sound,play it safe with ultrasoundThe past and present of ultrasonic test applications.

The history of materials and qualitytesting has always been a quite ”in-conspicuous” one. It’s in the natureof these things. However, if we con-sider that in many respects materialtesting is the very thing that makeslife safe, it should have deserved abit more attention. Sad enough, it’smostly not talked about unless it hasnot been carried out - or not been car-ried out properly - and damages oreven accidents could not be prevent-ed. The result that documents noflaws is seldom worth mentioning.We would therefore like to seize thisopportunity and for once do some-thing for it in order to devote to ultra-sonic testing – largely unnoticed inpublic – the space due to it. A few ap-plication examples are meant toserve this purpose, chosen from thegreat variety of field applications. In thisregard, the history of Krautkrämer is in-separably connected with the ever in-creasing possibilities of solving testproblems over the course of the past50 years.

Nothing done by halveswith semifinished productsMetal sheets or plates, tubes, rods orbars, billets – a great variety of fabricat-ed materials are ultrasonically testedbefore being further processed or fin-ished; this often enables optimizing themanufacturing process itself. The first”case” of the Krautkrämer brothers –blowholes or pores lying close belowthe material surface in wire drawingdies made of metal carbide – alreadyinvolved the task of reducing the rejectrates within the manufacturing process,that means of detecting material flawsas early as possible during the workingprocess. It turned out very soon thatthe testing of semifinished productswould be a domain of the automatictesting because it deals with largepiece numbers having identical geome-tries and with the integration into the

production process. So it came that anautomation project for plate testing in arolling mill was already worked on in the50’s. The idea developed at Krautkrämerof coupling via free water jets inthrough-transmission technique in or-

der to avoid probe wear contributed tothe construction of the first heavyplate testing machine. As early as in1960, a tube testing machine usingrotating probes was developed, thefirst of its type.

top: Mechanized weld testing using USIPbelow: Heavy plate testing using free water jets

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Automatic testing machines have al-ways been and will always be designedin close cooperation with the end user.A recent example includes the technicalprogress on the one hand, but on theother hand, it also shows that the prin-ciple hasn’t changed: this system per-forms a 100 % volume test on a wirehaving a maximum temperature of1000 °C, and it does it at rollingspeeds ranging from 10 to 45 m/s.Both internal flaws and surface flawsare detected and evaluated ultrasoni-cally – in this case using so-called rodwaves which are excited electrodynami-cally in the test material, that meanswithout any couplant.

Smooth transition:weld testingIn the early 50’s, the inspection ofwelds was already a matter of greatinterest to the industry. Welds alwayswere and still are something thatcause problems, for example in theindividual components of chemicaland power plants, and also in tankconstruction, shipbuilding and bridgeconstruction. Inspection of welds wasalready prescribed in those days dueto the obvious safety relevance. Thenewly appeared ultrasonic methodstepped beside the previously usedradiographic method and comple-mented it as it could be carried outfaster and without expenditure for rayprotection.

For the Krautkrämer brothers as pio-neers in the field of ultrasonic testing,weld testing was of course somethingthey took up at once: in 1952, aUSIP 5 was already used for testingthe large-diameter, longitudinallywelded pressure pipes of the Schluch-see power plant in the Black Forest.

At this stage, the position of eachflaw had to be determined by measur-ing and calculating; location aids werestill unknown. A true evaluation offlaws with reference to their position,type and size – essential factors interms of any possible impairment ofthe weld – wasn’t possible tillDr. Josef Krautkrämer developed theDGS diagram in 1958. In modern in-struments, such as the USLT 2000 orthe USM 25, DGS diagrams and trigo-nometric functions (display of soundpath, projection distance and flawdepth) for flaw evaluation are integrat-ed into the instrument by means ofsoftware.

The way is clearfor the German RailThe first truly usable ultrasonic flaw de-tector in Germany, which the Krautkrämerbrothers had developed in 1949, wassuitable for detecting material flawsin components made of steel. One ofthe first beneficiaries of the newmethod was the Federal German Rail-ways who had big problems after

1945 with the axle breakage on ex-press engines due to war damage.Par t of the wheelset axles showedmore or less large cracks that couldnot be recognized from the outside. Itwas possible for the first time to usethe ultrasonic method to nondestruc-tively detect the par tly extensive fa-tigue fractures in the wheelset axles.The extent of the cracks could be esti-mated with astonishing accuracy onthe basis of the flaw echo sequence.A systematic test of all locomotive en-gine wheelsets was carried out, onwhich occasion a lot of engines had tobe put out of service. This was theonly way to ensure that the train ser-vice could be safely continued.

The guaranteed safe operation ofmeans of communication and trans-por tation is still one of the most im-por tant tasks of ultrasonic testing to-day. Even if manufacturing technologyhas advanced fur ther and further –there’s always a risk left due to mate-rial defects, unrecognized errors andflaws produced during the manufac-

top:Weld testing

left:Ultrasonic testing of anaxle shaft

right:DGS scale as of 1967;developed on the basis ofthe General DGS Diagramfrom 1958

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turing process, unforeseeable stress-es, or a combination of several caus-es which cannot be fully excluded bythe usual safety precautions. Shaftsand axles of trains and trams orstreetcars must continue to be sys-tematically checked for any fatiguecracks at regular intervals.

Not a bad move:NDT on all routesUltrasonic testing plays a part in safetyand reliability in many different wayswithin the automotive industry - andagain, it’s almost unnoticeable in thebackground. Who could really claim thathe knows that valves, pistons, cylinders,crankshafts and many other items arenot used unless they have passed amaterial test? Dreaded breaking of ax-les and cardan shafts, spring and valvefractures of the past are long gone andonly very seldom happen today.

A particularly high safety relevancemakes ultrasonic testing indispensablein the aircraft industry as well. Rivetedjoints and bondings, for example at crit-ical transition points between fuselageand wing, or at the wing edges, landinggears, turbine blades, vital parts of en-gines – these are all objects liable to besubjected to the most thorough ultra-sonic inspection.

Though laid on thick: justthe remaining wall thicknessesThe first ultrasonic gauge, exclusivelymeant for measuring wall thicknesses,was developed by Krautkrämer in1967. The wall thickness measure-ment became especially important – forexample on pipelines operated by refin-eries – in terms of safeguarding envi-ronmental protection. A reduction of thewall thicknesses, for example due tocorrosion, can lead to disastrous dam-ages and accidents here. The ultrason-ic method has the special advantage ofallowing the wall thickness measure-ment to be carried out on objects whichare only accessible from one side. Wallthicknesses which are too low can bedetected in good time using systematicultrasonic checks. In addition, down-times and consequently also cost andtime expenditure can be reduced.

Thickness measurements are carriedout on various test objects subject towear: pressure vessels, gas cylinders,

storage tanks, receptacles for chemi-cal processes, material handling sys-tems and pumps, facilities in ship-building and structural steelwork.When the D-Meter thickness gauge,no bigger than a camera, was intro-duced by Krautkrämer in 1971, it sig-nified a spectacular improvement. Itwas spectacular because it was impor-tant in connection with plant supervi-sion tasks, for example within thechemical industry, that small and light-weight equipment be available for the”comprehensive climbing exercises”.The latest Krautkrämer thickness gaug-es only weigh around 250 grams, andthey offer even more advantages. Forexample, they enable precision wallthickness measurements even throughcoatings, without having to remove thecoating first.

Tales of layersCoatings are not only important in wallthickness measurements. In manybranches of industry, the assessmentof the coatings themselves is an inte-gral part of quality assurance. What’sat stake here is also the exact controland monitoring of coating materialquantities, which in the end aims atmaterial saving and cost reduction. Themeasurement of coatings is requiredfor example at automobile-body worksfor the paint coating layers on metalsheet base material, or within the woodworking industry for sealing varnish orprotecting lacquer layers on woodenbase material. These applications arenowadays also part of ultrasonic testrepertoire, and the innovative technolo-gy from Krautkrämer is decisive here. Inthis regard, it was possible to imple-ment an ultrasonic measurement reso-lution – in the micrometer range - whichwas previously unattained.

Play it safe with ultrasoundIn the course of the 50 years ever since1949, during which time Krautkrämerhas been active in ultrasonics, manythings have changed. An ever increas-ing number of test problems could besolved, more and more new require-ments from the field could be met.There were quantum leaps in technolo-gy, such as digital technology or theminiaturization in electronics, whichhas led to the present-day systemswhich are ultrasonic instrument and PCin one and fit into a laptop. Somethinghas never theless also stayed as ithas always been: material flaws can-not be excluded, the risks due tothem still exist, for example fatiguefractures due to cracks are nowadaysjust as topical as they were in 1949when the Krautkrämer brothers start-ed to deal with this problem. The an-swer to the question concerning apossible solution for all these prob-lems referring to materials testingand quality assurance is today thesame as it was yesterday: play it safewith ultrasound.

The application examples mentioned weretaken from specialized literature, e. g: KlausEgelkraut; Werner Grabendörfer: Ultraschall-Prüfung in Deutschland. Erinnerungen an dieAnfänge (Ultrasonic testing in Germany. Rem-iniscences of how it all began). Minden 1993

Wall thickness measurement:two are better than one.

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T E S T I N G T O D A Y

News about DM 4

Through-coatingmeasurement:DUAL MULTImode; indication:0.244 inchesthickness

Measuring through paint –correctly from now on!A frequent test task consists of mea-suring the metal wall thickness of pipe-lines and tanks. The task is to measurethese objects accurately and quickly inspite of surface coating – such as e.g.adherent paint coatings, plastic coat-ings or fiber-reinforced plastic sheath-ings. If these coatings are not takeninto consideration in the thicknessmeasurement, the result will show, de-pending on the coating thickness, con-siderable measurement errors (approx.2.5 times the thickness value of thecoating due to the lower sound veloci-ty). Up to date, it was absolutely neces-sary to use ultrasonic instrumentsequipped with monitor gates to avoidthis measurement error.

The thickness gauges DM 4 andDM 4DL with their new operating modeDUAL MULTI enable precision measure-ments of the metal wall thickness un-der adherent coatings - and what’smore, only via digital displays.

The measurement is carried out auto-matically between two successive back-wall echoes from the underlying basematerial; the echoes received from thecoating are ignored.

Special features of the method:

• The coating does not have to beremoved

• Measured-value correction is nolonger necessary

• Considerable time saving

Probes through intelligenceA wide range of probes, customizedfor different applications and require-ments, are available:

• For the measurement on hot compo-nents: medium temperature probesfor temperatures up to 200 °C andspecial probes for temperatures upto 800 °C.

• Intelligent dialog probes from the se-ries DA 4.., which are automaticallyrecognized by the instrument and en-sure an optimum instrument setup.

• The special probe developed for theDM 4DL with integrated remote con-trol key (type FH2E-D-REM) which en-ables to store measured values di-rectly by pressing a key.

• The DUAL MULTI operating mode al-lows the use of numerous standardprobes which have proved to be agood investment for the thicknessmeasurement on many occasions. Itshould be remembered that themeasuring range of the probes is re-duced because two backwall echoesare always required for the success-ful thickness measurement througha coating. The measuring rangetherefore depends on the type andthickness of the coating and on themetal thickness.

What else is new?• Choice between two operating

modes for the zero point calibrationwhen using non-dialog probes: con-tinuous with the probe coupled(= DA3 mode, corresponding to theDM 3) or automatic with the probeuncoupled (= Automatic mode, corre-sponding to the previous DM 4). The

DA3 mode is the right choice if thetemperature of probe and test objectdiffer from each other, and especial-ly well suited with probes from theDA3..series as well as with mediumtemperature and high temperatureprobes. The range of probes for hightemperature measurements couldbe widened by this operating mode.The Automatic mode is recommend-ed for test objects having a roughsurface and for probes showing non-uniform wear. This mode is carriedout automatically for all dialogprobes, but it can also be selectedfor non-dialog probes.

• Omission of the 2-point calibration,involving a lot of work, for all existingand future special probes as theyare recognized by the instrument.The probe zero adjustment is auto-matically carried out.

• Extension of the data memory capac-ity of the DM 4DL: with 5,390 read-ings – divisible into a maximum of999 files – the memory space of thedata logger has been doubled.

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The digital coating thickness gauge CTM 20 enables to measure coating and wall thicknesses on site accurately, re-producibly and quickly. For the first time, it’s possible to measure up to three coatings of paint, varnish/lacquer,plastic or other insulating coatings on metallic and non-metallic base materials, such as plastics, wood, ceramic,glass, etc., in one single measuring process. This is not possible using the conventional nondestructive methods(eddy current and magnet-inductive method). The CTM 20 enables to achieve a measurement resolution of 1 µm, thelower measurement limit for individual coating layers being 10 µm for paint coatings and 100 µm for wall thicknessmeasurements. The wall thickness can be measured through the coating.

State of the art incoating thickness measurementInnovative ultrasonic technology makes the CTM 20 a coatingthickness gauge that opens up totally new application possibilities.

The signal processing made it possibleto utilize the known pulse-echo methodfor the coating thickness measurementin a new way. Thanks to the use of pow-erful state-of-the-art electronics themeasuring system has been reduced toa perfectly handy size.

The system differs fundamentally fromthe operating method of conventionalultrasonic instruments. A few importantcorrelations should therefore be dealtwith in more detail for a better under-standing.

Possibilities and limits of con-ventional ultrasonic technologySound waves are excited in the testmaterial by the probe via a couplant,and these sound waves reach theprobe again after being reflected from aboundary surface or an internal inter-face. By a corresponding wiring theprobe serves as transmitter (or pulser)

and as receiver. If the material isscanned vertically, the known correla-tion [1] between sound velocity c,sound path d and acoustic time of flightt applies:

d = sound path (coatingthickness)

d = c • t/2 [1] c = sound velocityt = acoustic time of flight

(round trip)

The excitation time of the sound trans-mitter is so short in this connectionthat only wave trains (pulses) limited intime are generated. The frequency,shape and number of ultrasonic signaloscillations are decisive factors in thisregard for the minimum coating thick-ness that can still be resolved. Resolu-tion is to be understood here as theminimum distance between the echopulses that can still be separated ordistinguished by means of the usualmethods in the present-day technology.

A 15-MHz shock-wave probe, like theCLF 4, enables to even resolve coatingthicknesses (or wall thicknesses) downto approx. 0.3 mm in plastics. If theacoustic times of flight of the echoesbecome shorter than the duration ofthe ultrasonic pulse, the sound wavesare superimposed on each other andallow no conclusions to be drawn aboutexisting internal interface echoes (Fig. 1).

Fig. 1: Echo signals from a polystyrenecoating layer having dif ferent thicknesses,probe CLF 4

400 µm

200 µm

100 µm

50 µm

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The sound would take 8.33 ns for theround trip on a layer of lacquer/varnishcoating of 10 µm at a sound velocity of2,400 m/s. The above mentioned probehas a wavelength of 160 ns and is thusmany times the time of flight in thecoating layer. Up until now, time-of-flightdifferences shorter than their wave-length could not be evaluated.

Increase of resolutionby the pulse shapeAnother possibility for increasing theresolution is offered by the echo shapeand its time dimension. The so-calledtriangular pulse is obtained as an opti-mum from theoretical considerationswith a corresponding excitation by thetransmitter (or pulser). With a correspond-ingly narrow base width, it becomes ap-parent that this echo shape brings abouta considerable improvement of the res-olution in comparison with the usualprobe signals (Fig. 2).

Fig.2: Echo signals from a polystyrene coatinglayer having different thicknesses (pulseshape), probe CTF 1

The requirements for generating thispulse with a corresponding excitationare met in good approximation by thetransducer element material PVDF(polyvinylidenefluoride). The sensitivityof such transducer element systems is

nevertheless relatively small comparedwith ceramic elements. On the otherhand, they match paint and plasticcoatings better (similar impedance).Thelosses of the ultrasonic wave at thetransition point from the transducer ele-ment to the test material (or delay line)are therefore smaller than with ceramicelements; this partly compensates forthe smaller sensitivity.

Such a broadband PVDF probe was de-veloped for the CTM 20. In order to at-tain an optimum signal quality, both theultrasonic transmitter (or pulser) andthe receiver preamplifier were integrat-ed into the probe. Though this probemakes it possible to obtain higher reso-lutions, coatings smaller than approx.30 µm lead to superimpositions of thesound waves travelling to and fro in thiscase as well, and thus to the limits ofresolution mentioned.

Ultrasonic evaluationwith signal processingA further step toward solving the prob-lem with high-resolution time-of-flightmeasurement is taken by means of thesignal processing:

The ultrasonic pulse-echo response canbe observed as the convolution of thematerial response with the initial acous-tic wave. The individual times of flightwhich are inseparable or cannot be dis-tinguished in the superimposed echodisplay can be resolved by means of a”deconvolution operation”. The echo in-dication reaching the receiver can be il-lustrated by a superimposition of time-shifted and scaled reference echoes.This superimposition can be separatedto form individual pulses by means ofsuitable algorithms. The individual puls-

es thus calculated contain the soundpath up to the corresponding boundarylayer or internal interface.

Besides the measurement of the echoindication, a prerequisite for these cal-culations is also the measurement ofthe reference echo (probe without cou-plant against air). The special develop-ment for the coating thickness gaugedescribed here consists in finding asuitable deconvolution algorithm. Thelatter must produce correct and repro-ducible results and must be flexible fordifferent applications.

Field testsShown below is the A-scan of a three-layer varnish/lacquer coating on a plas-tic base material (Fig. 3). This can beread from the instrument and displayedfor any measurement via the Windowssoftware CSOFT. A microsection (Fig. 4)was made as comparison. The displayshows the measured signal, the calcu-lated signal as well as the deviation ofboth curves. The following five echoesare recognized from the left to the right:

• inter face echo at sound entry(probe delay line - couplant)

• coupling echo (couplant - layer 1)

• internal interface or boundarylayer echo 1 (layer 1 - layer 2)

• internal interface or boundarylayer echo 2 (layer 2 - layer 3)

• internal interface or boundarylayer echo 3 (layer 3 – base material)

The end of the probe delay line is indi-cated above the A-scan, and the corre-sponding readings for each layer, aswell as the total coating thickness.

Fig. 3: A-scanfrom CTM 20

400 µm

200 µm

100 µm

50 µm

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The bars represent the calculatedecho positions and amplitudes. If thecorrespondingly scaled reference ech-oes are placed at these positions, theresult is the calculated signal. If theecho positions are correctly deter-mined, the deviation between themeasured and the calculated signalreaches a minimum.

The calculated coating thicknesses cor-respond perfectly to the results of themicrosection. Any deviations possiblydetected may be the result of a differentmeasuring position as well as of differ-ences between the preset sound veloci-ties. The same can be adjusted to thematerial on the instrument if necessary.

Nondestructive measurementof coating thicknesses... is possible using the CTM 20 even incases which previously did not allowthis to be done. The CTM 20 opens upnew application fields for nondestruc-tive test methods. It is for example pos-sible to measure the individual layers ofpriming, undercoat and transparentcoatings on the sheet metal base mate-rial within car body making - in one sin-gle measuring process and withouthaving to remove a paint coating layer.The automotive industry offers numer-

Fig. 4: Microsection

ous application fields for the instrument— wherever individual coatings on plas-tics have to be measured: on bodyparts, bumpers, fittings/instruments, etc.

The measurement of paint coatings isalso an essential topic for the aircraftindustry; the important thing here is toachieve a minimum possible weight byreducing the paint coating thicknesses.Likewise for the wood working industry:on all wooden supports or bases thecoating thicknesses of sealing and pro-tecting lacquer can be measured on allwooden bases using the CTM 20.

In many cases, it’s not only the qualityassurance which is concerned withcoating thickness measurements, butalso the optimization of material use.The CTM 20 makes it possible to alsoreduce cost by accurately checking andcontrolling coating material quantities.

The invasion of the smallest onesThe members of the USM family are lightweight, mobile ultrasonicinstruments overshadowing quite a few ”big ones”.

Fig. 1: Instrument front view with rotary knobs

Miniaturization makes it possible: afamily of fully-featured ultrasonic flawdetectors in an extremely small, light-weight and rugged housing presentingan exceptional design for the rougheveryday testing conditions and thestraightforward operation with the an-alog feeling. The absolutely new thingabout the instruments from the USMfamily is the fast ”transflective” LCDscreen enabling an A-scan refreshrate of 60 Hz for the first time, andreally ensuring optimum readability inall ambient light conditions. For thefirst time, the A-scan can be evaluat-ed at an unusually large viewing anglein bright sunlight without a lightscreen – even from a larger distance.If it’s dark, the backlight is simplyswitched on.

The remarkable features of all ver-sions of the USM family, in short:

• Weight and size are the same forall instruments: 1.6 kg includingthe four NiCad cells, 265 mm wide,245 mm high and 46 mm deep, in-cluding the turning carrying andprop-up handle.

• The operating concept is unique:all functions are set using two rota-ry knobs (Fig. 1). The left-hand rota-ry knob allows direct access to the

instrument gain at any time. Theright-hand rotary knob is always as-signed to the function that was ac-tivated from the four functions of

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Fig. 3: Screen display: standard - zoomdemonstrated by the example of USM 25

Fig. 2: USM 25 in weld testing

the selected menu by pressing akey. Pressing the key another timeenables an additional fine orcoarse adjustment of the values insome cases.

• Another exceptional feature is thelow power consumption: only fourstandard NiCad baby cells are re-quired to use the instruments foreight hours. As an alternative,AlMn cells which are availablearound the world can be used. Thestandard package also includes auniversal plug-in power supply unitby means of which the instrumentscan also be operated on any supplysystem (85 to 260 VAC) as re-quired.

• Moreover, the product is providedwith a practical transport case madeof plastic in attaché case design withroom not only for the instrument it-self but also for all the necessaryaccessories for testing, e.g. probes,cables, small reference blocks, cou-plant, the plug-in power supply unit,the operating manual, and the neck-strap which is very practical whenev-er you need both hands at the sametime for a test job.

• The turning transport handle thatrotates through 360° is at thesame time used as a prop-upstand. It enables a secure opera-

tion on almost any mounting sur-face, it does not matter if it’s in-clined or curved (Fig. 2).

• The standard display on the largeLCD screen shows the A-scan witha resolution of 220 x 200 pixels, tothe right the four selected func-tions with the momentary adjust-ment values, below the A-scan themeasurement line including thecurrent measurement results ofthe evaluated echo indication (inthe gate). If required, the currentreading can additionally be copiedin large digits to the A-scan so thatit’s still recognizable even from alarger distance. As soon as all set-tings of the flaw detector are deter-mined, the function menu is deacti-vated by pressing a key. The A-scanis then enlarged to 95 mm x 66 mmhaving 320 x 220 pixels (Fig. 3). Allinstrument functions, except forthe gain, are at the same timeblocked to avoid unintentional ad-justment.

• All instruments have a data memo-ry for filing 100 data sets. Onedata set contains the complete in-strument setup including the corre-sponding A-scan. It is thus possibleto file individual settings for imme-diate test use – as well as all theresults in the same way.

• The RS232 inter face enables theeasy output of test repor ts via aconnected printer or the bidirec-tional data exchange using a PCand the UltraDOC software.

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Fig. 4: Detection of a blowhole using a 1 MHzcomposite probe in a highly sound absorbingworkpiece made of gray cast iron

Fig. 5: Memo pad referring to the result indata set 11

USM 22BDoes the test task only call for the ba-sic functions – similar to those on ananalog ultrasonic instrument? In thatcase, the USM 22B is the economic al-ternative. It can be used on any materi-al (sound velocities from 1,000 m/s to15,000 m/s), the minimum displayrange is 2.5 mm, the maximum displayrange is 1420 mm (with steel), whichmeans that more than 90 % of all work-piece sizes can be covered. The broad-band frequency range from 0.5 MHz to15 MHz (- 3 dB) offers an adequatepenetration capacity in workpiecesshowing higher sound attenuation char-acteristics, and an excellent resolutionwhen it comes to detecting small reflec-tors or to carrying out a high-resolutionwall thickness measurement. The moni-tor gate (in bar-type display) is used forthe alarm output via an LED, and for allmeasurement tasks. In this connec-tion, it is also possible to switch over toa dual gate for measuring sound pathdifferences. This enables accurate wallthickness measurements with a resolu-tion of 0.01 mm or 0.001 inches, or mea-surements through a (paint) coating.

USM 22LThe USM 22L is especially designedfor ultrasonic testing of very largeworkpieces up to a length of 10 m(steel), or workpieces showing espe-cially high sound absorption (e.g.plastics) or sound scattering (e.g.cast materials, nonferrous metals).To improve the penetration depth, thepulser energy was increased. Threefrequency filters enable an optimumadaptation of the correspondingprobe to the test requirements. Therange from 0.1 to 2 MHz in particularenables ultrasonic testing on work-pieces having especially high soundattenuation characteristics, particu-larly in combination with the new com-posite probes (Fig. 4). All other func-tions of the USM 22L are identicalwith those of the USM 22B.

USM 22FUltrasonic CRT screen instrumentshave already been used in stockbreed-ing of animals for slaughter for manyyears now in order to be able to get”nondestructive” qualitative informa-tion about the animal’s condition on thebasis of echo indications from the indi-

vidual tissue layers. Especially the lastecho in the evaluation gate, corre-sponding to the ultrasonic reflectionfrom the muscular tissue, is interestingfor this purpose. This is the reason whythe reading is given only from the lastecho of a series displayed on thescreen. Thanks to its optimum housingdata, the easy operation, the longoperating time and the large data mem-ory, the USM 22F is therefore theinstrument best suited for the fat andtissue layer thickness measurement instockbreeding.

USM 25The ”big brother” of the USM 22 is theUSM 25. The frequency range was in-creased to 20 MHz, the function rangewas also considerably extended. Thismeans that the additional functions ofthe USM 25 support many more de-manding ultrasonic tests. In order tomaintain the field-proven, intuitive oper-ating concept, only one more key had tobe added to the operator’s control pan-el: the new key to the left of the fivemenu keys activates a second series offunction menus. The rest of the opera-tion is identical with that of the USM 22.

Which new functions are ready foruse with the USM 25?

1. For tests using angle-beam probes:angle of incidence, X-value and thick-ness of the workpiece to be tested.Additional evaluation results are cor-respondingly displayed in the mea-surement line: projection or reducedprojection distance and the reflectordepth taking the workpiece thick-ness into account.

2. In addition, the echo amplitude cannow also be displayed as a dB-differ-ence with regard to a stored refer-ence echo.

3. The echo evaluation is carried out ei-ther at the intersection point of theecho flank with the gate or at theecho peak.

4. Besides the full-wave rectification, itis additionally possible to switch overto the positive or negative half-waverectification.

5. As a standard feature, the USM 25offers a choice of three frequency fil-ters through a total range from0.5 MHz to 20 MHz.

6. Thanks to the memo functions, themanagement of the data memoryhas become considerably morestraightforward:

• Every data set can be provided withadditional alphanumerical identifica-tion.

• Every data set can be assigned to agroup of editable fields. The currentdate and time are an integral part ofthe memo text.

• The data sets can also be displayedas a list (directory).

• The A-scans of all data sets can beviewed using the preview functionand loaded back if required.

7. Horn for the acoustic signalling of agate alarm.

8. I/O interface, e.g. to output the gatealarm or the trigger signal, or to inputa test data release signal for control-ling the validity of the measured value.

The example of a weld inspection illus-trates the advantages of the USM 25:all important coordinates and the echoamplitude of the detected reflector ap-pear in the measurement line. Any cho-sen reading, in this case the dB-differ-ence with regard to the reference echo,is copied in large digits to the A-scan.The result is described in the memopad (Fig. 5); all data, including the com-plete instrument setup with A-scan, arestored as data set.

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Fig. 6: Flaw echo 3 dB above the DAC from a50 mm thick austenitic weld

USM 25 DACFinally, this instrument version is theUSM 25 extended by the functions forgenerating and using a Distance-Ampli-tude-Curve (DAC). The DAC is generat-ed using a maximum of ten referenceechoes. The amplitudes of the refer-ence echoes are stored in this connec-tion and used for calculating the record-ing curve. After activation of the DAC,the curve appears in the A-scan. Echoindications can now be evaluated withreference to this curve. The value dBcis selected as an additional reading forthe amplitude evaluation, indicatingthe dB amount by which the echo indi-cation exceeds or falls below the DAC.

Moreover, the use of the DAC functionsmeets international specifications:three other curves at user-definable dB-distances from the original curve can

Everything about scannersAutomation based on a modular system successfullyin use worldwide.

likewise be displayed. The curves areautomatically recalculated in the caseof any gain variations or variations ofthe display range so that all indicationsare always evaluated in relation to therecording or response threshold (DAC)(Fig. 6). A function has also been incor-porated to take test-related correctionsinto consideration, e.g. the transfer cor-rection.

Standard applications can be evaluatedeasily and without any problem with theoptional DGS method which is pro-grammed in the instrument for themost frequently used probes.

Considering the capabilities of thesmall instruments from the USM family,they certainly don’t need to fear com-parison with the big ultrasonic instru-ments. New technologies crystallize

into great advantages in field testingsituations with these instruments – forexample, the LCD screen, or the minia-turization that packs the performancerange of a modern digital ultrasonic in-strument into the volume of a cigar-box.This is the state of the art in 1999which will surely also endure in the nextmillenium.

Fig. 1: Scanner inter face

Manual ultrasonic testing only needsthe positioning accuracy of the hand;test results are written down, the po-sition on the test object is determinedusing the measuring tape. If higherdemands are set and if the ultrasonicdata are visually displayed, the probeposition has to be continuously de-tected. The measuring tape is replacedwith path pick-ups or position encodersas is the case with ANDSCAN (ultrason-ic system for mapping corrosion pro-files, or for bonding tests and flaw de-tection) and with ISONIC (system forweld inspection). The probe is stillguided manually in these cases, how-ever, the probe position is recordedusing path potentiometers or air-borne sound. Ultrasonic and positiondata are processed to C-scans. Thisis the point where the user will notice,at the latest, how much work is re-quired to vir tually scan 100 percentof a test sur face – the C-scan merci-lessly shows the sur faces still to bescanned, which means: it will all haveto be automated! Logically, it has to

be modular, universal, adaptable toall test tasks, economic, easy touse....

A universal inter face is offered byscanners driven with stepped motors(Fig. 1). Power amplifier and motorare a compatible unit. Multiaxis-con-trollers provide the three signals forclock, direction and motor current ac-tivation for each axis – irrespective ofthe size of the drive. If linear guides

are then added to the modular sys-tem, the most different test problemscan be solved using only one system!

A small, portable scanner for weld in-spection (Fig. 2) is operated using thesame software as the ”big brother”for testing aircraft components...

Aircraft components, constructed inhoneycomb design, are tested inthrough-transmission mode using wa-terjet probes with a scan sur face of

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Fig.3: Testing of aircraft components

Fig. 2: Small scanner for weld inspection

6 m x 4 m and two Z masts which canbe controlled independently of eachother – a car wash would of coursealso be possible in this way (Fig. 3).

Besides these two extremes, a tai-lored solution is available for everyapplication case.

Wall thickness measurementon components havingunknown sound velocities

A total of 20 Krautkrämer systems havebeen in use worldwide ever since theintroduction of this modular system –with a continuous upward tendency.However, we do not limit ourselvesonly to complete systems; existingsystems can likewise be modernized.The test mechanics are generally de-signed in such a way that an opera-tion is possible over several decades.Due to the use of computer technolo-gy, the development of data acquisi-tion, recording and evaluation meth-ods nevertheless moves so fast thatthese components no longer corre-spond to the state of the art afteronly a few years. So, why not replacethis part?

A few examples from the wide rangeof application possibilities: systemsare being used not only for testing

switching contacts but also for testingcamshafts, turbine discs or rods forsafety parts – needless to say, all cer-tified according to the currently validspecifications.

As a rule in ultrasonic wall thicknessmeasurements, the acoustic time offlight is measured, and the product ofthis time of flight and the ”known”sound velocity is then the wall thick-ness.

However, it may happen that the soundvelocity is not known because

• no point on the component is acces-sible for a mechanical thicknessmeasurement, and therefore nosound velocity can be determined.

• the sound velocity may largely varyalong with the temperature. This is avery marked feature, e.g. with plas-tics.

• the sound velocity varies locally in in-homogeneous materials, such as ingray cast iron for example. In such acase, no constant known sound ve-locity can be used for the wall thick-ness measurement.

The latter was the case some timeago when testing paper rollers whosewall thickness was to be continuouslychecked, firstly, in order to avoid acase of damage in due time and, sec-ondly, to achieve a maximum possibleservice life. The AUTO-V method wasdeveloped by Krautkrämer for thiscase, enabling to start by measuringthe sound velocity at any location,and to continue by integrating this val-ue into the current wall thicknessmeasurement.

To do this, a probe having two transmit-ter and receiver elements is used. Thepair of transducer elements called T1 -R1 excites a longitudinal wave parallelto the surface, a so-called ”head wave”(Fig. 1). The current sound velocity ofthe longitudinal wave is calculated fromthe measured time of flight and the de-sign distance between the single trans-ducer elements. A typical A-scan ofsuch a situation is shown in Figure 2.

The second pair of transducer elementscalled T2 - R2 measures the time offlight vertically to the surface at thesame probe position (Fig. 3). The cur-rent wall thickness can now be calculat-ed using the previously determinedsound velocity.

The pairs of transducer elements arealternately activated by a dual-channelmultiplexer, with four measurementsbeing carried out per second using amodified instrument software.Fig. 1: Principle of the AUTO-V probe

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Fig. 4: AUTO-V probe

Fig. 3: A-scan in the wallthickness measurementmode

Fig. 2: A-scan in the soundvelocity measurement mode

An ultrasonic instrumentfor all eventualities

The current wall thickness and soundvelocity are displayed on the screenwhile the component surface is beingscanned.

The use is not only limited to ferrousor nonferrous metals, but it’s also

successful e.g. on ceramic materialsor plastic components.

The ultrasonic flaw detector USN 52was equipped with a dual-channelmultiplexer to implement this testmethod.

The probe with its four transducer ele-ment units is shown in Figure 4. Inthis case, it’s a probe for checkingthe wall thickness of cast steel of pa-per rollers whose sound velocityshows strong local variations. For thispurpose, the probe is mounted on adevice provided with magnetic rollers.This ensures steady continuous test-ing.

The new USN family makes it possible.New versions of the proven small flawdetectors have been brought out gain-ing a great deal from the results of thetechnical progress within the computerindustry. Processors become fasterand faster, and memory chips containmore and more capacity. Decisive forthe further development of ultrasonicCRT-type units, however, is the displayspeed of digital flat screens.

The digital screenLet us recall: analog screens or CRT’srewrite the signals at every ultrasonicpulse fired. This means that withsmall units, such as e.g. the USK 7 S,the A-scans are updated 1,000 timesper second, with lab instruments andinstruments for automatic testing ma-chines up to 12,000 times, or evenmore often. Things are a bit differentwith digital ultrasonic instruments:

• The signals received by the probeare first subdivided into small timeintervals of equal size. An oscillatorcrystal supplies the clock pulses.Typical frequencies for this start at30 MHz. This frequency is alsocalled ”digitizing frequency” or ”sam-pling rate”. We use a sampling rateof 240 MHz in the instruments of theUSN series (generated from 30 MHzand multiplied by the factor 8).

• The amplitude of the signal receivedis then determined one by one ineach one of the small time intervals.The amplitude value A in the inter-val “i” has a certain analog voltagewhich is now assigned a numberaccording to a fixed amplitude inter-val scheme. In this case, the num-bers lie between 0 and 255, corre-sponding to 8 bits (28).

• All digital amplitude values Ai mustbe buffered temporarily. This resultsin a data volume of approx. 20 kB(20,000 values) for an A-scan in therange of 250 mm (steel).

• To display this quantity of values on adigital screen, a data reduction is al-ways necessary because the num-ber of pixels on the screen is muchsmaller than the number of valuesgenerated. This task is accom-plished by the data processor of adigital instrument. It must always beensured in this regard that all maxi-mum amplitudes actually are trans-ferred to the A-scan to be displayed.The computing time required for theseoperations is inserted at the end of atransmit/receive cycle. The time inter-val between two transmitter pulses istherefore extended, and the pulse rep-etition frequency is reduced.

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• Besides the pulse repetition fre-quency, the screen refresh ratealso plays a decisive role. Thoughthe human eye perceives a se-quence of 25 single images persecond (cinema) as a continuousmovement, this speed is notenough for ultrasonic testing: ifworkpieces are scanned faster,flaw echoes can no longer be rec-ognized reliably in this way be-cause their dwell time on thescreen is simply too short. By in-creasing the image refresh rate inconnection with a certain inertia ofthe pixels (”persistence”), suchshort signals are now also reliablyrecognized. This means that thefaster new A-scans are displayedon the screen, the closer we get tothe customary representation of ananalog display.

Flat screensAt first glance, digital flat screenshave many advantages to offer com-pared with the CRT’s: less space re-quired, lower current consumption,lower cost, display of text and mea-sured values as well as less environ-mental impact. These essential ad-vantages are nevertheless paid forwith the following restrictions:

• limited screen refresh rate

• stair-step representation of thesignals due to the division of theimage into pixels

The electroluminescent display usedin Krautkrämer instruments (USD 15,USN 50/52) is fast enough with itsscreen refresh rate of 60 Hz. Liquidcrystal displays (LCD), as they arenowadays used in many devices ofour everyday life (digital clocks, note-books, PC’s, etc.), could not be usedfor ultrasonic instruments up to datedue to the slow display generating.However, the technology has ad-vanced: thanks to a direct transistor-controlled excitation of the liquid crys-tals, an optimization of the liquid andnew backlight techniques, we havenow an LCD at our disposal whicheven meets the requirements of ultra-sonic testing. The new ”transflective”LCD screen enables us to attain thepractice-oriented A-scan update rateof 60 Hz.

The new USN familyWe have now applied the new technol-ogy to the field-proven ultrasonic flawdetectors USN 50 and USN 52, andat the same time added new func-tions. These product extensions arealso applied to the versions equippedwith the EL display. All new USN 50/52units are equipped either with the ELdisplay having double the resolutionof the earlier versions, or with the fasthigh-resolution LCD screen. To makea distinction between the two, the in-struments are now called: USN 50L,USN 52L (LCD versions) and USN 50R,USN 52R (EL versions).

It goes without saying that due to thehigh display contrast with bright ambi-ent light, the ”L” versions are particu-larly well suited for all outdoor appli-cations. For the first time, no lightshield is required, not even with directsunlight. Another advantage of the

”L” versions is the extended operat-ing time due to the considerably lowercurrent consumption of the LCD. As aresult of this, a battery charge lastslonger than one test shift.

Extended functions round off the newimage of the USN family. For examplea so-called memo function in theUSN 52 instruments, enabling toidentify data sets alphanumerically,brings about more clarity for the test.The contents of the memo pads for allassigned data sets can be trans-ferred to a PC or a printer. Further im-provements include the exact reflec-tor localization with angle beaming oncurved workpieces and the 0.1-dBfine adjustment. The two USN 52 ver-sions contain the DGS option whichmakes it possible to unambiguouslyand reproducibly evaluate smallflaws.

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Tube testing - on a large scale,off-the-peg design

Immersion testingwith the UPR family

There are basically three concepts forthe complete ultrasonic testing ofseamless or welded tubes:

• rotating probes along a linearlytransported tube

• fixed probes on a spirally trans-ported tube

• probes moved linearly along astationarily rotated tube

Krautkrämer delivers ultrasonic tubetesting machines according to thesethree design concepts.

The so-called rotation testing ma-chines (rotating probes) previouslyreached their limits at a maximum di-ameter of 180 mm. The family of therotation testing machines (ROT) hasnow been extended upward, i.e. it hasbeen expanded for larger diameters.The new machine type ROT 350 en-ables a standard diameter range from60 to 340 mm to be tested.

The machine is not only characterizedby the large test range but in particu-lar also by the variable probe assem-bly having a total of four probe mod-

ules. Besides ”classical testing” forlongitudinal, transverse and laminarflaws, additional probes can be built infor testing angled flaws and for the di-mensional measurement.

Other probes can alternatively be acti-vated for special tests (e.g. for ex-tremely short flaws). That means thatelectronic channels, including the cor-

responding evaluation, can be as-signed to the operation of individual,permanently installed probes.

The first machine for the diameterrange from 60 to 250 mm was deliv-ered to TUBACEX/Spain, the secondmachine for the diameter range from60 to 340 mm was delivered toCONDUVEN/Venezuela (see photo).

Nondestructive immersion testing ofhigh-quality components (high-dutysafety par ts, e.g. turbine discs) hasstrongly increased during the last fewyears due to tightened legislation(product liability).

To be able to carry out these tests,Krautkrämer has developed a modu-lar concept, viz. the “Universal PortalRobot”.

A UPR system consists of the follow-ing components:

• ultrasonic electronics

• recording and evaluation system

• test mechanics including controlsystem

The system can be easily adapted tomost different job specificationsthanks to its modular setup both interms of test mechanics and in termsof software.

The main objective when developingthe UPR was to implement a comput-er-controlled machine for the produc-tion inspection which can be con-trolled by means of easy-to-operatesoftware - and which would then en-able fully automatic scanning afterthe (one-off) definition of a scan se-quence. The scan sequence is pro-grammed by “teaching”, or by directinput of the scanning paths.

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The C-scan software (operating sys-tem Windows NT) is the control centrefor all this, enabling to control the fol-lowing parameters:

• ultrasonic settings

• mechanical parameters (travelpaths, speeds, etc.)

• recording and representation ofthe test results as C–scans, flawreports

The linear travel paths are implement-ed by stepped-motor controlled linearaxes. These linear axes are availablein almost any length graduations. Ifround (rotationally symmetrical) partsare meant to be tested, a turntabledriven by a stepped motor or servo-motor – depending on the weight ofthe components to be tested – isused. Mounted on the Z-axis is aprobe manipulator which can be pro-vided with one or two angular axes aswell as with an additional rotationabout the Z-axis, depending on thespecified job.

Should parts having a complex geom-etry be tested, the scan sequence isdivided into individual scan steps. Astep consists of travel parameters forthe mechanics and for the corre-sponding ultrasonic settings. Thesesteps are automatically processedone by one without the operator hav-ing to intervene.

The figures show two typical imple-mentations: a 7-axis scanner (Figure 1)for testing turbine discs (the machineis approved for tests according toBMW-RR, GE, MTU, etc.), as well as a4-axis system (Figure 2), equippedwith rollers, for testing bars.

The test results are shown as C-scans(Figure 3). In addition to the C–scan, twosections are laid through the C-scan atthe cursor position, and the amplitudecurve is shown along the sections.

The raw data are always stored, andthey can also be subsequently edited(other color assignments, other re-cording thresholds, etc.). The rawdata can be subjected to differentevaluation algorithms (e.g. filters, ad-jacency viewing). It goes without say-ing that the software allows to gener-ate customized reports.

Fig. 2 (above): UPR4 electronics (BARMAG, Remscheid)

Fig. 1 (left): UPR7 (FUCHS, Meinerzhagen)

Fig. 3: typical C-scan

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T E S T I N G T O M O R R O W

True or not true?News from Charlie Smartchecker.Charlie Smartchecker has meanwhilestarted his own service business fornondestructive materials testing andspecialized in ultrasonic testing – hav-ing gathered many years of experiencein this field. His motto being Open tothe new, yet under obligation to tradi-tion, he manages his business togetherwith his son Charlie Jr., who’s acting asjunior manager and who’s supposed totake over the business later on. Thebusiness is doing well, Charlie Smart-checker has already built up a reputa-tion in the branch, he’s known as anhonest and upright partner. Charlie Jr.on the other hand, a software and in-ternet fan, always looking for newpaths, is often of the opinion that hissenior takes too little risks, that thestructure and the method of the busi-ness are urgently in need of moderniza-tion. Maintaining the market position,that’s Charlie Smartchecker‘s goal,and after all, he wants to leave his sona flourishing business.

One day, Smartchecker & Son are ableto get a large order. It consists of test-ing a pipeline section having a totallength of 40 km. The pipeline (nominaldiameter 900 with a wall thickness of12 mm) is meant to be subjected to a100 % inspection on either side of theweld. The test requirements determinethat the ultrasonic test specified forpartial sections and the radiographictest be carried out and be documentedanalogously in spite of the different testmethods. The contract award is, amongother factors, subject to the followingspecifications: observance of the cus-tomer’s QA guidelines, a fairly compre-hensive specialized documentation in-cluding evaluation of single results. Allwelds are clearly identified by a codewhich is subsequently meant to beused for managing the correspondingresults in a database. During the teston site, all indications exceeding the re-cording threshold (circular-disk-shapedreflector as reference reflector) shall bedocumented using position coordinatesof the reflector (flaw) as well as the re-flector’s echo dynamics.

The total contract volume is approx.$ 200,000.- for the radiographic partand approx. $ 140,000.- for the ultra-sonic part. Charlie Smartchecker, an”old hand” in the job, has gone into alot of raptures over the documentationcapabilities of his ultrasonic equipmentand thus been awarded the contract forthe ultrasonic part. At the moment, thetesting company has a USD 15 and twoUSN 52 units from Krautkrämer, as wellas three older analog ultrasonic instru-ments having no documentation capa-bilities. In view of the order, CharlieSmartchecker has already secretlyplanned a new investment for a new ul-trasonic instrument equipped withstate-of-the-art documentation featuresamounting to approx. $ 30,000.-.

So Charlie Smartchecker contactsKrautkrämer – asking them to submit aquotation for a corresponding ultrason-ic system. He knows that Krautkrämerwill quote for this ultrasonic notebookUSLT 2000, which opens the way tomodern data processing, and thatthere’s a special application softwarefor it, as well as – to sort of round it alloff – an additional development toolcalled UltraWORKS. All of it costingaround $ 25,000.-. Those people atKrautkrämer claim that UltraWORKSmakes it relatively easy to create yourown applications and to access all testresults.

The junior is not enthusiastic. He saysthat it’s only software that you can justas well develop or have developed foryourself. He has an old college friendwho’s been writing software for manyyears now. He doesn’t do anything else.He knows a lot about these things. He’lltake care of it - in two weeks for$ 1,100.- to be more precise. It wouldthen be possible to take the USD 15, ithas an interface. That’ll make the testsystem complete. Charlie Smartcheck-er refuses at first, but in a moment ofweakness he could be persuaded andchanged his mind. Anyhow, the juniormust know what he’s saying. After all,he knows how to surf in the internetand everything.

In the end, Charlie Jr.’s college frienddevelops – according to the order andeven on schedule - an ultrasonic docu-mentation software called Titanic IIwhich is used for the pipeline inspec-tion. The pipeline welds are inspectedaccording to the order. Two inspectorscarry out the weld test parallel to oneanother, each using an ultrasonic in-strument. Any indications subject to re-cording are at once stored in the datamemory of the instrument. Having ac-complished the day’s work, the two ul-trasonic instruments are connected toa PC, and the test results are trans-ferred. The data are processed accord-ing to the specifications using Titanic II,and the required documentation is gen-erated – viz. for all welds, even forthose not containing any indicationssubject to recording at all.

The test is carried out: everything is allright. Or is it?

The owner of the pipeline system, arather suspicious man after a few nastyexperiences in the past, has samplingcheck tests carried out on the ultrason-ically tested pipelines – always at thestart, in the middle and at the end ofeach pipeline section. He isn’t pre-pared to accept any test section and topay the bill for the corresponding testjob till after this has been done. Andthat’s how something happens that no-body has expected: two out of threetests on the first pipeline sectionchecked produce indications subject torecording. Both welds are marked ok inthe corresponding documentation gen-erated by Titanic II.

The customer summons the testingcompany to meet him. At first, Smart-checker & Son cannot believe at allwhat’s being claimed. However, duringa ”manual” rechecking directly on thepipeline, indications subject to record-ing are actually detected. The reasonfor the wrong results must therefore befound in the documentation software.

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Junior sees the problem in the PC con-nector cable and says that he’s oftenhad difficulties with that. Charlie Smart-checker on his part is not at all satis-fied with this explanation, he wants toget to the bottom of this matter and in-sists on having the software revised byits author plus on an immediate elimi-nation of the cause of the error. CharlieJr. promises to take care of that.

Not having heard anything about the re-quired software revision after a coupleof days, the senior asks about it. Thejunior shamefacedly informs him thathe has been desperately trying to getinto contact with his friend till he finallylearned that the latter could not bereached: not now and not within thenext few months – because his friendhad quit studying, having felt a sudden

urge to experience the most differentcultures on various continents for thepurpose of self-realization.

The wildest thoughts flash throughCharlie Smartchecker’s mind: disinheri-tance, selling the company, emigration.Finally, he comes to his senses, and hemakes an appointment with the ownerof the pipeline - and with Krautkrämer.

The software error has made the entireultrasonic documentation worthless.The customer naturally insists on acomplete re-inspection of the pipelineand demands that the documentationsystem has to be supplied by a re-nowned manufacturer. In addition, heinsists on a preliminary acceptance ofthe documentation system. CharlieSmartchecker gets off lightly one more

time: he’s allowed to continue workingon the order, he doesn’t even have topay for the time delay.

After all this, Charlie Smartcheckerdid what he should have done rightfrom the star t: he bought the USLT2000 including the development toolUltraWORKS from Krautkrämer andhad his own documentation softwarecreated. Charlie Jr. was no longer con-sulted about this matter.

Due to the additional expenditurecaused by the double testing, thecompany ends up with a deficitamounting to almost double the in-vestments. Charlie Jr. is now payingthis off. Besides, he has enrolled inthe necessary training courses atKrautkrämer.

Quick hardness testing,quick documentationWith UltraHARD toward the future of mobile hardness testing.

UltraHARD:user inter facewith graphicalanalysis oftest data

MIC 10 and DynaMICKrautkrämer has a lot to offer for themobile hardness testing which repre-sents a quick and, most of all, an eco-nomic alternative to stationary testingin today’s manufacturing process. WithMIC 10 and DynaMIC, the program in-cludes products that cover a wide appli-cation range. The two actually refer totwo different physical methods - thestatic UCI and the dynamic reboundhardness testing method – implement-ed in a uniform instrument concept.Both instruments enable hardnesstesting in a matter of seconds: placethe probe or the impact device on thecomponent, trigger the measurement,read the hardness value on the display.

UltraHARDThe UltraHARD application software,developed for both hardness testers,extends their function scope in terms ofevaluation, statistics, documentation,data processing - and it makes the workeven easier, the testing process includ-ing the corresponding applications

even faster, for the documentation forexample. UltraHARD, which joins theseries of proven Krautkrämer applica-tion programs, is available in two ver-sions having different performanceranges.

Basic functionsThe basic module of UltraHARD primelyconsists of a data transfer function fromthe hardness tester to the PC, and in an

automatic interfacing with the Windowsor MS-Office world. Test reports can beeasily generated – for example as apredefined Excel sheet form which onlyhas to be recalled for subsequent testreports: all that has to be done is topress a key, and the next test repor tis ready. The integration of graphicsinto the repor ts – analyzing graphicsor company logos for example – is like-

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Array transducerswith integrated electronicsfor industrial applications

wise no problem with UltraHARD. Ofcourse, the program feature also en-ables to fur ther process the data inExcel with all its possibilities, e.g. ingraphics or for statistics. In the casethere is no MS-Office environmentavailable, the program additionally of-fers a simple integrated editor for testreport generation.

User-friendly toolsTo make it easier to use the program,user-friendly tools were integrated: aso-called WIZARD for example guidesthrough the individual actions, helpsto define test repor ts and to alsoplace, apart from the measured val-ues, other important pieces of infor-mation – order numbers for example –at the required position in the test re-port form. The test report only has tobe defined once, and is afterwardsused as a template model for the testreport.

A Data Manager, similar to the WindowsExplorer in its setup, enables to com-pile measurement series for test re-ports – sorted, for example, accord-ing to date of orders, test points, cus-tomer or order numbers, etc. Dif fer-ent organization levels are offered inthis regard to help with the assign-ment and sorting of data. The possi-

bility of simply renaming the measure-ment series – which are still typicallyidentified by means of consecutivenumbers in the hardness testers to-day – by giving them alphanumericalnames brings about further advantag-es for the general arrangement.

Additional functionsBesides the data transfer and docu-mentation functions, to which the pro-gram version UltraHARD light is limit-ed, UltraHARD‘s standard version hasmany other things to offer. For exam-ple, graphical analyzing tools for thefollowing applications:

• linear representation of measure-ment series for hardness progresscurves

• frequency distribution / histogram

• case-hardening thickness (accord-ing to DIN 50190), nitriding depth,and rim zone hardness depth

• statistical evaluations of individualmeasurement series or of the com-plete readings on all measurementseries

All important information can be seenat a glance. These program featuresof UltraHARD enable, for example, tographically display and evaluate thehardness progress curve on welds;

the display of frequency distributionof readings allow to draw conclusionswith regard to the process capability.

There’s an extended function rangeeven for report generation: test re-por ts are available in standard for-mats which can be easily edited. How-ever, they can also be generated indi-vidually, a process which is likewisemade easy for the user by simple op-erator control features.

Moreover, UltraHARD has an ”onlinescreen” which directly displays themeasured values on the PC screenduring the test on the one hand, andserves for the remote control of thehardness tester on the other hand.The hardness test can therefore becontrolled from the PC.

SummaryUltraHARD enables an easy ”docking”to the MS-Office world. In particularthe test documentation ”at the pressof a key” makes the work easier inview of today’s legal requirementsand in view of the quality assurancedemands. Yet it’s all done quickly andconveniently. Those of us who are notquite unfamiliar with the Windowsworld, will get to know UltraHARD ”inless than no time”.

Figs. 1 and 2: Segments of a single elementtransducer and a circular element

What is an array transducer?An array is basically a large single ele-ment transducer, which has been sub-divided by cutting it into small seg-ments as shown in Figure 1. Typicalelement sizes are from 0.5 mm(0.02 inch) to 2.5 mm (0.1 inch), al-

With the drive to smaller, less expensive and more sensitive electronic de-vices, the array instrumentation area is now economically more viable for in-dustrial applications, and Krautkramer is pleased to announce that we arenow developing and manufacturing industrial instrumentation to take advan-tage of the features which arrays open up.

though custom sizes are available.Also available are annular arrays,which are circular elements, dividedinto donut shaped annular elements(Fig. 2).

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Fig. 3: Different elements and sound beams

Figs. 4 and 5: Time delayed firing and wavefront for angle beaming

Figs. 6 and 7: Time delayed firing and wavefront for focusing

Fig. 9: Time delay control with echo signals

Fig. 8: Linear scanning

Why divide the probeinto small elements?A large probe will give a good flat cov-erage, but its small beam angle limitsits ”visibility“. A small element has amuch larger beam divergence angle,and it is this large angle which opensup the useful features of arrays suchas dynamic focussing and beamsteering.

Another feature of small elements istheir energy transfer efficiency -small-er elements take less energy to exciteand are more efficient receivers dueto the lower mass to be energized.Beam divergence is also a function offrequency, lower frequencies will givemore divergence than higher. Typicalsizes/frequencies for industrial appli-cations are 1 mm wide for 2.5 MHzand 0.5 mm wide for 5 MHz.

Beam SteeringAn important aspect of array usage isthe ability to dynamically synthesizean ultrasonic beam and create a ”Vir-tual Probe“ of any angle within theoverall beam spread of an individualelement.

An angle beam is created by sequen-tially firing each element in an array tocreate a wave front following the de-sired angle. The angle is selected andset up electronically by the instrumen-tation, and can if necessary bechanged pulse by pulse. This ”VirtualProbe“ can also be ”swept“ through atest object by firing groups of ele-ments in a large array.

Dynamic FocusingAs shown for dynamic beam steering,the same effect can be used to dy-namically focus an ultrasonic beam byselecting the array firing order andpulse delays. Again, this can bechanged on a pulse by pulse basis toeffectively ”sweep“ a focal pointthrough test material. Note the beamsteering and dynamic focusing can becombined to give a resultant beamwhich is both focused and angled(used e.g. for tube testing applica-tions).

Linear ScanningLinear scanning (sometimes calledsynthetic aper ture scanning) succes-sively fires adjacent groups of ele-ments to create a scanning effect.The ”Vir tual Probe“ width and scanpitch can be controlled by selectingthe number of elements fired in paral-lel, and the number of elements in-dexed for successive shots.

Figure 8 shows two elements fired to-gether, with an index of one element.This technique can be combined withboth beam steering and dynamic fo-cussing to apply a ”scanning motion“to angle and focussed beams.

Phased Array Creationand EvaluationAs shown for beam steering and dy-namic focussing, a beam can be cus-tomized and created by selectivelysetting the firing order and time de-lays for individual elements.

However, what happens with the re-turned signals? How can they be eval-uated as a single ultrasonic signal?

Figure 9 below shows the same pat-tern for firing the simple steeredbeam, but includes simulated signalsall occurring at the same relative dis-tance from each array element.

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Fig. 10: Main bang and echoessuperimposed in time

Fig. 13: Weld testing on a tube using thephased array technique

Fig.14: Phased array using the tandem tech-nique for testing welds

Fig. 11: Main bang and echo with phasecompensation

Fig. 12: A-scan display of compensatedsignals

Note that on a single timebase(Fig. 10), all the signals do not align,which makes evaluation difficult.

This problem is overcome in twophases. First, each received echostream from each array element isdigitized and all echo streams arealigned so that the phasing offset isremoved and echoes are then shownrelative to each other on a standardtime base (Fig. 11).

Next all the aligned echo trains aredigitally added so that any indicationsfound by more than one element willbe amplified and will give a true pic-ture of the relative size of the indica-tion (Fig. 12). This then results in asummed presentation which is thenfed into a standard USPC 2100 in-strument as a regular signal as re-ceived from a standard single ele-ment transducer, and is evaluated bygated and standard measurements.

Tube Flaw DetectionThis system is used to test the tubeweld in an ERW welded tube. The sys-tem is installed in-line to scan theweld area. As the radial position ofthe weld can wander, as the tubemoves between the weld head andthe testing position, scanning is nec-essary to cover any deviation.

The system allows for automatic set-up to accommodate different tube di-ameters and thicknesses with no re-setting of transducers. Because ofthe system tolerance to weld wander,the probes can also be installed in aposition in the production line wherethe tube is cool and mechanically sta-ble from vibrations.

The application uses all the phasedarray features described previously.

• Beam steering to generate thecorrect angle in the tube

• focussing the beam in the weldarea

• linear scanning to move the beamacross the weld area.

Tube ThicknessAs with the previous flaw detectionapplications, this application also isused in the ERW tube manufacturingprocess. In this instance the array isfocussed and scanned to measurethe wall thickness of the tube.

This measurement is usual to checkthe alignment and state of the scar f-ing tool which trims the ID post weldflash from the tube.

The technique uses focussing and lin-ear scanning to cover the area ofinterest.The results are evaluatedand presented to the user as C-scanand B-scan images of the weld area,along with thickness tolerancechecks.

Tandem ScanningPhased arrays allow for dynamic scan-ning using the tandem technique. Toutilize the technique, separate arraygroups are defined as transmit andreceive ”vir tual probes“ and scannedto cover the test area.

This technique can be used for test-ing welds in thick sections.

Testing of thick-walled containers inpower plants is a special applicationfor the tandem technique. The datarecording capability is of particularimportance for application of theseparts.

The units necessary for the phasedarray test systems:

• Array transducer

• Array module

• Time delay cards

• Ultrasonic electronics (e.g.USPC 2100) with evaluationelectronics

The test system itself can, and must,be customized; due to the relativelyhigh engineering expenditure it is im-perative that there be close coopera-tion between user and Krautkrämer,as supplier. Owing to the applica-tion’s complexity, the conditions forsuccessful operation must be inten-sive project studies and consultation.

If these preparations are made, thephased array test system will certain-ly solve difficult test tasks whichcould not be solved up until now.

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Joined together by weldingUltraLOG - a forward-looking development in close cooperationwith the industry.

IntroductionThe ultrasonic method has also beenused in spot weld testing for manyyears now. A large number of automo-bile manufacturers worldwide are usingultrasonic systems from Krautkrämerfor nondestructive spot weld testing.The use of this method was evenmore eagerly accepted within the indus-try because of substantial new develop-ments within the ultrasonic technolo-gy. Krautkrämer has played a decisivepart in this development for more than10 years by launching correspondingtest equipment as well as product fami-lies and accessories respectively. Thefollowing report does not only presentboth newcomers and long-standingpros an updated stock-taking of the testmethod, but it also describes a promis-ing problem solution by the example ofthe ultrasonic notebook USLT 2000 andthe application software UltraLOG.

Industrial requirementsThe use of ultrasonic technology fortesting spot-welded joints offers sub-stantial advantages for the user whencompared with the conventional inspec-tion using ”a hammer and a chisel”:

• The component is not destroyed ordamaged (less scrap)

• Determined test results can be pro-duced

• Test results become comparablebecause a test result is document-ed independently of the inspector(ultrasonic display)

• The test process can be easily auto-mated

The obvious arguments speaking forthe use of the ultrasonic method leadto a continuously increasing accep-tance among the users, in spite of theconsiderable expenditure on the train-ing of test personnel and the necessaryintra-company transfer of know-how.

In order to set up a field-oriented testmethod especially for this type of

application, other essential argumentsmust also be taken into account:

Legal regulationsImplied warranties stipulated by law,and especially the Product Liability Act,force manufacturers to furnish proof ofa correct manufacturing process of aproduct in the case of doubt. To achievethis, the manufacturer must documentboth the production process and any in-spection and checking actions taken.Recall actions are meant as a means ofconforming to these general legalguidelines, however, they will not be ef-fective until after a defect has been de-tected. An adequate test method helpsto avoid expensive recall actions in ad-vance by preventive measures.

Production processMore and more complex prefabricatedsingle components, assembled on onesingle site in next to no time, are usedwithin the automotive industry. It goeswithout saying that this requires sophis-ticated checking mechanisms ensuringthe safe and reliable assembly of per-

fectly flaw-free single components. Thismakes incoming inspections as well asa uniform test method agreed uponwith the sub-supplier indispensable!

Besides that, tests must be carried outwithin the production process withoutaffecting the actual production pro-cess. That means that both the testequipment and the actual test must bedocumented quickly, reliably and clearlyleaving no room for doubt. In this con-nection, the degree of automation with-in the production process, determinedinternally within each individual compa-ny, must also be taken into consider-ation as a guideline to be followed. Thefully automatic production control is fac-ing an inspection or test system whichis automated to the farthest possibledegree. The quality of the complete ve-hicle should already be warranted dur-ing the production of the single parts.

Quality management philosophyDepending on the QM concept, thetest is not only regarded as a statisticalverification of the produced quality.

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Modern systems also have a sensoryfunction in the sense of a continuousimprovement process (CIP). Informa-tion on short-term quality variations atcertain welding stations or long-termobservations of the process, e. g. in thecase of changes in the material thick-nesses or surface quality, are to be re-corded and evaluated. A test systemmust be able to produce correspondingindicators.

Test environmentThe test can serve as a means of verifi-cation within the production process onthe one hand, or it can be used for fur-ther QA statistics outside the processon the other hand. The actual test re-quires adequately trained personnel.The possibility for a quick and directdocumentation and further processingof the data obtained from the test mustlikewise be given. Modern QA and pro-cess control systems should be able toutilize the test as a corresponding datasource.

Moreover, the test philosophy has to betaken into consideration. That means,how’s the test going to be carried out?Two methods are common in the fieldin this connection. The setup involveseither fixed test stations, e. g. near thewelding station, or flexible test systemsused alternately at different locations.

EquipmentApart from the actual ultrasonic sys-tem, the inspector should be giventhe chance of executing all routineoperations by means of a correspond-ing system. This includes the menu-guided processing of the test, for ex-ample by means of an inspectionplan, as well as the automatic docu-mentation of all test-relevant dataand an inspection assistance tool(evaluation assistance tool). The in-spection assistance tool should beable to present automatic results forthe test classes OK, too small nug-get, poor fusion/bad through-welding,loose joint, stick weld, burnt spot,both for two-plate and for three-platejoints. The ultrasonic system, theprobe, as well as the correspondingQA and evaluation software should ofcourse come from one and the samesupplier.

How does a future-orientedproblem solution look like?With all these influential factors, thereader is naturally liable to suspect itto be questionable whether theremight be any feasible solution at all, asolution that would be both handy andeasy to use, at the same time allow-ing for all the factors describedabove. State-of-the-ar t ultrasonictechnology from Krautkrämer howevercovers all these aspects.

Here’s our proof...The ultrasonic notebook USLT 2000 isa high-resolution ultrasonic system,rugged in its industrial housing, andyet handy, especially well suited forthe evaluation of spot welds undermanufacturing conditions. The digitalpart of the ultrasonic component con-sists of a card, approx. the size of acheque card, in a standard notebook.With a horizontal pixel resolution of1024 pixels, this portable system is aworldwide leader. This excellentscreen resolution enables to recordand evaluate the weld inspection ofeven the thinnest metal sheets.

Add to this the evaluation and QA soft-ware UltraLOG, and you have custom-ized evaluation software included in thepackage besides the ultrasonic system!The overall system is based on the op-erating system WINDOWS 95 (compati-ble with WINDOWS 98 / WINDOWS NT).State-of-the-art software technology (cli-ent-server technology) will ensure thatall known utilities of the operating sys-tem or corresponding industrial-stan-dard application programs (e.g. MS-Office) are automatically also sup-ported.

These state-of-the-ar t hardware andsoftware technologies make it possi-ble to open up totally new paths forthe systematic inspection of spotwelds!

Automatic evaluation assistance toolUltraLOG contains dif ferent evalua-tion assistance tools (Evaluation As-sistance I, II, III) which produce opti-mum results depending on the metalsheet combination and sur face quali-ty of the material. These evaluationassistance tools were developed andtested in direct cooperation with auto-mobile manufacturers over a period of

about two years. This will ensure theuser that he’s not dealing with a ”ba-nana product” (ripens at the custom-er’s), but with a field-proven evalua-tion system. In addition to fixed-pro-grammed evaluation algorithms, theevaluation assistance tool also con-tains a ”teach-in” method in which dif-ferent ultrasonic displays can be filedfor a test result. The filed displays arethen compared with the currently ac-tive display in each case. If they areconsistent with each other, the corre-sponding test result is displayed.However, the standard algorithms(Evaluation Assistance I/II) havemeanwhile also matured to such anextent that consistencies of 94 %were attained in measurement seriescarried out with ”NOK” spots in thesecases!

Test data managerAnother feature contained in UltraLOGis a complete database system forgenerating and managing the test re-sults, as well as for the test manage-ment. Inspection plans can be gener-ated for individual inspectors or cer-tain test stations by means of testdata managers. This enables to plan,to control and to document the actualtest process. These plans may in-clude instructions for testing themost complex components (e.g. acomplete car body). UltraLOG doesn’tcontain any limitations with regard tothe nesting depth - i.e. structural set-up - of the components under test. In-spection plans can be generated andmanaged in a centralized or decentral-ized manner (depending on the com-pany’s EDP structure). For example,the Planning Department can preparethe complete test system for any cho-sen production lines, without having tohave any direct contact with the actualtest station. The ready-made inspectionplans are distributed among the testsystems via network, e-mail, internet,or quite conservatively, on a disk.

The processing degree is of course vari-able by means of the built-in three-stage safety system (Administrator/Master/Inspector). The work processescan be optimally controlled in this way,avoiding any collisions or overlappingsduring the actual test or during the testpreparation.

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A new dimension ofultrasonic testing...The inspection plans are called by theinspector by pressing a key at the cor-responding station. The inspector isthen guided through the test accord-ing to the sequence defined in the in-spection plan. The inspector can easi-ly recall test-specific support data foreach plan (test instructions, compo-nent drawings). The required supportdata (e.g. material data) are of courselikewise filed in the inspection plan.Depending on whether the inspectorwould like to see the large high-reso-lution ultrasonic display or whether hewould rather like to be guided by thecomponent drawing (e.g. in the caseof unknown components), he has thepossibility to change the views duringthe test. The actual test is largely au-tomated, i.e.:

• The inspector couples the ultrason-ic probe to the spot weld accordingto the model in the inspectionplan/test sketch.

• The ultrasonic display will automat-ically stop (!) as soon as all cou-pling conditions are met.

• The automatic evaluation assis-tance tool evaluates the spot weldaccording to the set evaluationmethod and makes an evaluationsuggestion.

• The inspector shortly checks theresult visually and signalizes by re-coupling the probe that he acceptsthe test result (documentation willthen take place parallel to this).

• The system goes automatically tothe next spot weld to be tested.

Whether or not the information ob-tained from the test results can be re-lied on in the ultrasonic inspection isinfluenced by the probe used. Theprobe element diameter must corre-spond to the specified minimum nuggetdiameter. A wrong choice can lead toincorrect test results. New ”intelligent”dialog probes make sure that such mis-matches are avoided. The operationalreliability and consequently the informa-tion obtained from the test results thusgain a new quality.

An automated test can be carried outup to 10 times per minute, i.e. a maxi-mum of 600 spot welds per hour. The

inspector carries out the complete teston the component. Basically no inter-ventions are required during the test onthe test system. Should interventionsnevertheless become necessary (e.g. arepeated measurement), the essentialfunctions can be influenced during thetest process via remote control. Thedocumentation of the actual test resulttakes place without any additional workparallel to the test process, i.e. the in-spector doesn’t have to enter any addi-tional data. All test results, as well asall ultrasonic parameters are automati-cally stored in the database for eachcomponent in question. It is thereforealways possible to present statistics oncomponent level for each test station,or to furnish full documented proof ofthe test on a component from the pointof view of Product Liability.

And always rememberto keep in touch!It goes without saying that, apart fromthe test process control, the test resultand further processing are importantaspects, especially for the online quali-ty assurance. Once generated, all testresults are immediately available forfurther processing, e.g. via network ore-mail. These test results meet the re-quirements in terms of the documenta-tion duty under Product Liability, andthey can be utilized for statistical as-sessments or for production processcontrol. Determining the characteristicfactors for each work station, weldingstation, component, or different time-

related viewing methods are possiblewithout any problem via the integratedWINDOWS interfaces.

Summing-upSpot weld testing using the ultrasonicmethod has gained worldwide accep-tance today in many companies withinthe automotive industry. Krautkrämerhas fundamentally shaped this applica-tion by various product families over theyears.

At present, the most up-to-date andmost versatile system worldwide isUSLT 2000 with the application soft-ware UltraLOG. This unit combines atraditional application with ultrasonicknow-how and state-of-the-art EDP tech-nology in such a way that an innovativeand forward-looking system was devel-oped for this application.

Besides the cost saving in comparisonwith hammer and chisel, the decisivething about the use of this method isthe possibility to actively participate inthe continuous improvement process(CIP) of the QA system in question. Thedocumentation possibilities take gener-al legal conditions (Product Liability Act)into account and create additional pos-sibilities of obtaining information aboutquality variations within the productionprocess and of drawing direct conclu-sions as to their cause if applicable.

This method is becoming ever increas-ingly accepted by the automotive indus-try.

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R E P O R T S A N D O P I N I O N S

The Krautkrämer training systemThe continuously increasing demandson quality, safety and reliability of theproducts call for an improvement ofthe development and productionmethods, and along with it also thetraining and qualification of special-ists in the quality control. The nonde-structive test methods gain more andmore importance in view of all this.

We as manufacturers of ultrasonictest equipment have realized very ear-ly that a flaw detector plus operatingmanual alone is only of little use tothe operator. For this reason, the helpwith the solution of test problems giv-en by our Application Lab as well asthe field-oriented training courses ofthe inspectors and test operators or-ganized by our Training Departmentare an integral part of our after-salesservice.

We have held one-week training cours-es on the subject of “NondestructiveUltrasonic Testing” at Krautkrämerever since 1955 - and since 1992,these courses have also been held onsubjects from the field of eddy currenttesting. We are thus able to base ourwork on comprehensive experienceand to immediately introduce new de-velopments in the test sector into ourcourses.

Our courses are divided into a theoreti-cal and a practical part. In the theoreti-cal part (in the morning), the funda-mental principles of the test methodand its applications are presented. Thepractical part (in the afternoon) is thengone through according to a detailedprogram of exercises in groups of twoto three participants at workstationsequipped with state-of-the-art instru-ments. The practical exercises are setup in such a way that the theoreticalknowledge acquired in the morning issubstantiated by the exercises. In thisconnection, the course leader inter-venes by giving explanations and bydemonstrating whenever any errors aremade, or whenever a work group askshim for help. At the end of a trainingcourse, a detailed certificate of partici-pation is handed out to the participant.

The training in the field of ultrasonictesting star ts with the course “Intro-duction to Ultrasonic Testing” whichdoes not require any specializedknowledge. Duration: 5 days (40hours). Subject matters of the trainingcourse are: fundamental principles ofphysics of the sound propagation;generation of ultrasound; setup andfunction of (analog and digital) ultra-sonic instruments and probes; cali-bration and localization using straight-beam, angle-beam and TR probes;easy documentation of test results.

The training course “Introduction toUltrasonic Testing” meets the require-ments for entering the qualificationexaminations “Level I-UT” accordingto the ASNT document SNT-TC-1A, aswell as the “Level 1-UT” according toEN 473. We are currently offering theLevel-I examination (ASNT) and willsoon also offer – following a corre-sponding agreement – the Level-1 ex-amination according to EN 473 whichwill then be held at our company byan authorized independent test spe-cialist.

Taking the basic course “Introductionto Ultrasonic Testing” as a basis, the

training course titled “Ultrasonic Eval-uation of Flaws” is held, dealing withthe theoretical and practical aspectsof the fundamental principles of re-cording and evaluation of flaws or dis-continuities according to the DGS, ref-erence block and half-value methods.Duration 5 days (40 hours).

The continuing training course “Appli-cation-Oriented Selection of Ultrason-ic Probes” is likewise based on thebasic course “Introduction to Ultra-sonic Testing” and on the advancedcourse “Ultrasonic Evaluation ofFlaws” in which theoretical and practi-cal knowledge and skills can be ac-quired in terms of choosing the suit-able probes for the different applica-tion cases of the daily field testing sit-uations, for the evaluation of test re-sults and the creation of testinstructions. Duration: 5 days (40hours).

The two previously mentioned trainingcourses together, i.e. “Ultrasonic Eval-uation of Flaws” and “Application-Ori-ented Selection of Ultrasonic Probes”with a total of 10 days (80 hours) oftraining time, meet the requirement forparticipating in the Level-II examination

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according to the ASNT documentSNT-TC-1A. Following a correspondingagreement the requirements for partic-ipating in the Level-2 examination ac-cording to EN 473 will also be met. Thisexamination will then be held, as theLevel-1 examination, at our company bythe certification authorities.

Other training courses in the field ofultrasonic testing, organized by us inour training centre at Hürth, include:

• Ultrasonic Testing of WeldedJoints.

• Practical Exercises on DigitalUltrasonic Equipment.

• Practical Exercises in UltrasonicThickness Measurement.

• Introduction to Eddy Current Testing.

In addition, we organize our standardand specialized training courses – suchas e.g. “Ultrasonic Inspection of SpotWelds in Car Body Making” - on request

worldwide also in English. Besides this,our U.S. associated company at Lewist-own likewise offers corresponding train-ing courses in the USA.

For more detailed information aboutour training program, please contactour Training Department.

Probes for the DM 4The latest version of the thicknessgauge DM 4 presents considerable im-provements in comparison with earlierversions. Besides the possibility ofmeasuring the thickness of base mate-rial through coatings (DUAL MULTI func-tion), a DA3 mode was created to opti-mize the operation of DA3.. probes.

High-temperature measurementsFor example, when using the probesDA 315, DA 317 and DA 319 for mea-surements on hot surfaces up to ap-prox. 200 °C as well as DA 305 up toapprox. 500 °C in the DA3 mode, thedelay line length is measured while theprobe is coupled to the test object. Thishas the following advantage in compari-son with measurements in which theprobe is lifted off: time-of-flight varia-tions due to heating of the probe delayline during the measurement can be di-rectly compensated for. This excludes atemperature drift of the measurementresults, i.e. the measurement resultsare exact and independent of any influ-ences by coupling time and cooling cy-cle.

The new DA3 mode is also of advan-tage when using the probes DA 301,DA 303 and DA 312 for measurementsat ambient temperature because themeasurement result is influenced bytemperature variations in this case aswell, if only slightly. The DA3 mode thusallows to obtain a considerably morestable and better reproducible mea-surement result for all DA3.. probes.

Dialog probesThe latest generation of the DA 45..-type dialog probes for the DM 4 opti-mize the utilization of the measure-ment accuracies that can be achievedwith the instrument. The probe con-tains a memory chip carrying all thenecessary settings for the optimuminstrument operation. When connect-ing the dialog probe to the DM 4, theinformation filed in the memory chipis read by the instrument, and all theparameters are automatically set inthe instrument accordingly. This re-fers e.g. to the gain, the phase angle tobe evaluated of the delay line and back-wall echo, and to the correction curvefor the V-path error which always existswith the dual-element (TR) probes.These adjustment data are type-relatedin the case of standard probes, i.e. thedata are constant for a type regardlessof the single probe unit.

With special probes for the DM 4, onthe other hand, single unit-relateddata can also be programmed in thememory chip in order to be able tocontrol the instrument individually forevery single probe. This enables toobtain the best signal-to-noise ratioeven with critical measurement tasks,i.e. it makes maximum measurementsafety and reliability available. As alladjustment data for the DM 4 areavailable in the memory chip, theuser does not have to worry about theinstrument setup. He can rather relyon the fact that the instrument setupis always optimized so that he can ful-ly concentrate on the actual measure-ment task. The DM 4 always has ex-actly the same setup, even in repeti-tive in-service measurements, with-out the user having to note down thissetup.

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Another step forwardin ultrasonic testingBy Erik Zimmermann, Zeppelin Silo- und Apparatetechnik GmbH, Friedrichshafen

In 1895, Wilhelm Conrad Röntgen dis-covered the X-rays, called ”Röntgen” af-ter him in German. Ever since that time,nothing fundamental has changed in ra-diographic testing developed at thattime, except that the X-ray films and theX-ray machines have been improvedand become more efficient.

One of the great advantages of radio-graphic testing was always the docu-mentation in the form of the X-ray filmwhich could be filed. In the case of ul-trasonic testing, it was previouslycommon practice to draw up hand-written test reports, which is oftenseen as a disadvantage.

Ever since we started using the ISONICtest system, we have taken one stepforward in this regard. We are nowable to hand out a representativepiece of documentation to the ex-perts and to our customers. This com-prises the demonstrated proof of thecorrect execution of the test and thereal-time evaluation of all signals, in-cluding the echo indications from theultrasonic instrument – even as true-to-scale and graphic representations.

Another aspect is based on the factthat an X-ray image or radiograph al-ways only represents a shadow image– without any information as to thedepth position of flaw indications.ISONIC offers not only a top view forthis, but also the side view from whichthe depth position can be read. Howoften has a weld been repaired fromthe wrong side! This is avoided whenusing the ISONIC.

Moreover, it often happens that theultrasonic inspection detects cracksand lack of side fusion more sensi-tively than the X-ray method. An exam-ple of this: We would like to describeour first experiences using a normalwork specimen made of WstE355.The metal sheet specimen was radio-graphed after welding according to

top: X-ray film

middle: Extract froma test report

bottom: Microsection

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standard specifications. No irregulari-ties were noticed when the film wasevaluated. The additional ultrasonicinspection using the ISONIC system,however, revealed a flaw measuring17 mm in length. This flaw area wasafterwards again radiographed usingan X-ray tube as well as a more sensi-tive film quality and another beamingdirection. Once again, no flaws weredetected when evaluating the film(please see X-ray film range 37-39cm). As the test object was a workspecimen and not a finished tank, amicrosection was taken from the loca-tion concerned. The defective spotcould then be seen under the micro-scope (please see microsection photo).

Another characteristic feature of ISON-IC is the reproducibility of the test: ev-erything is documented by the systemright from the start, from coupling viaprobe movement up to complete vol-ume coverage, that means the wholetest sequence (please see extract fromthe ISONIC report on the above-men-tioned work specimen) - and not only forferritic welds, but also for materialssuch as aluminium alloys. The require-ments of the European and U.S. stan-dard specifications can be met withoutreservations.

The step into the next century wouldthus already be traced out, the test iscarried out by a certified inspector us-

ing a calibrated system, and the eval-uation is made ”at a round table” aswith the X-ray film evaluation.

Summary:

• Documentation, ISONIC now makesit also possible for the ultrasonic in-spection

• Determination and documentation ofthe flaw depth position

• Large-area flaws in welds can oftenbe better detected ultrasonically thanby means of the radiotechnology

• Improvement as against the conven-tional ultrasonic inspection: couplingmonitor.

Steps in ultrasonic testingExhibition of historical test equipmentat the DGZfP Annual Conference 1999

On the occasion of this year’s annualconference of the Deutsche Gesell-schaft für zerstörungsfreie Prüfung(German Society of NondestructiveTesting) in Celle, an exhibition hadbeen arranged showing remarkabledevelopments in ultrasonic materialtesting devices in West and East Ger-many – from the early days of their in-dustrial application up to the end ofthe ”analog era”. A handsome num-ber of instruments were presented il-lustrating to the visitor the technicalprogress of electronics and test tech-niques in particular.

Krautkrämer was always able to bringout the main features and to contrib-ute to the development with manymilestones in the past five decades.No wonder the following ”Krautkrämertreasures” were encountered at thehistorical exhibition:

• ultrasonic flaw detector USIP 4(1951); the first instrument at thetop left

• portable ultrasonic flaw detectorUSK 2 (1956),with a separate power supply unit

• TR probe SEB 4 (1958) - a worldsuccess in a dual package

• portable ultrasonic flaw detectorUSK 4 (1961), with display magnifier

• Corrometer (1967), needle meterfor wall thickness measurements

• D-Meter (1971), wall thicknessgauge in camera format

• ultrasonic flaw detector USL 35(1976), with logarithmic amplifierand programmed distance laws

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Service in changing timesIn the era of a transition from the in-dustrial society to the informationand communication society, thefunction and the importance of thetechnical after-sales service havecontinuously and lastingly changed.

Development during thelast few decadesIf the after-sales service was a neces-sary evil for the manufacturers at thetime of booming demand of the 50’s,this was followed by thoughts of repo-sitioning the services and of redefin-ing the staff profile in the 60’s whenthe first signs of a market saturationshowed up. In the decade of the fol-lowing 70’s, the range of goods of-fered still increased, decreasing profitmargins led to cost pressure, trans-parency was in demand. At the sametime, a technical revolution took placedue to the microprocessor. It was thetime of the systems specialists and ofthe ”cost center”.

After-sales serviceas marketing instrumentIn the high-tech market of the 80’swith a high market saturation, the af-ter-sales service developed into anactive, sales-supporting marketing in-strument. As a result of this, today’sglobal market calls for open systems– with the consequences that the of-fers and supplies must be based on”integral thinking” and on the princi-ple of ”everything coming from oneand the same supplier”. This refers toinformation, engineering, calibrationservices and maintenance of value,and is per formed, for example, bymeans of hardware modification andsoftware update.

Service Center at KrautkrämerIn view of this – from the customer’spoint of view certainly advantageous –development, the Krautkrämer Ser-vice Center was founded in 1983, of-fering various benefits for the custom-er: closeness to market, short pathsfor information and decisions, experi-ence, technical competence for in-struments and systems with the re-

sulting synergies, commercial han-dling, including spare parts sales andlogistics – and with a direct connec-tion, the Service-Center hotline(..2233 / 601 111).

Specialists for all instrument versionsare standing by in the repair shop,contributing to an effective problemsolution (software/hardware) and toshort repair times with their special-ized knowledge. As our customerscannot do without their test instru-ment for too long, we have an exten-sive stock of service spare parts di-rectly at our disposal. High-tech prod-ucts require original spare par ts. Ex-perienced employees are at your dis-posal for questions concerningcomponent specification, price deter-mination, availability and delivery. Ev-ery repair closes with an intensive en-durance test and a comprehensive fi-nal inspection.

In many countries of the world, our”mobile workshop” comes to the cus-tomer, for example if the system is in-tegrated into a production process. Ashort reaction time is taken for grant-ed by us. In addition, our field servicestaff safeguards the investments of

the customer by software updates ormodifications of the test device for anew or additional job.

Training and instruction are an impor-tant prerequisite for the repair andadjustment of modern equipment. Ev-ery single move has to fit, the soft-ware must be masterly installed. Ourservice know-how is therefore impart-ed to the technicians of our represen-tatives worldwide in training courseswhich the Service Center continuouslyorganizes and offers.

Services within the frameworkof quality assuranceThe demands for the comprehensiveand thorough precision of test equip-ment have enormously increased dur-ing the past few years. The verifica-tion of the reproducibility and compar-ativeness of measurements at regu-lar intervals has become an integralpart of today’s quality assurance sys-tems. Objective and reproducible testmethods are therefore used for thecalibration of ultrasonic test equip-ment. One example of this are themathematically generated referencesignals of a waveform synthetizerused by us for checking and optimiz-

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ing the per formance of test instru-ments and systems. The test proper-ties of the instruments are thus al-ways traceable; we carry out tests ac-cording to national or internationalguidelines – taking into considerationthe EN equipment standard to be ex-pected - or according to especially de-veloped Krautkrämer criteria whichare recognized throughout the world.

A large range of servicesoffered today ...Our services are field-oriented andcan be utilized as a modular system.The inspection comprises calibrationaccording to delivery specifications,software update if required, networktesting according to VBG 4 and docu-mentation. In addition, we offer thespare parts option, just in case that adefect is detected during the inspec-

tion. The repair is carried out immedi-ately, the necessary component ormodule is billed at a special price. Ifmaximum availability is at stake, ourmaintenance agreement (completeservice) is just the right answer. Weoffer inspections at regular intervals,software update, repairs at a fixedprice, including material and labour,instruments and modules to getthrough the repair period, as well as aguaranteed reaction time. Since soft-ware is something that ”lives”, wekeep the software-update agreementready. It includes the automatic mail-ing of new software versions, supportby phone, special prices for our soft-ware training courses offered at regu-lar intervals, and the use of our free-call hotline.

... and tomorrow.Everybody’s talking about the year2000 – and so are we. Our supportwill shor tly be extended by two inter-esting aspects: we shall make equip-ment firmware available by means ofdownload programs via the data net-work, and we shall introduce – espe-cially within the systems service – thetechnique of remote diagnosis. Thefirst steps have already been taken inthis direction, steps that will bring ourcompetence a bit closer to the cus-tomer.

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E C H O P U L S E S

Checking ofresistance spot weldsDefinition of position of the ultrasonic spot weld testing.

In the last editions of echo, we reportedon the methods and advantages of ul-trasonic spot weld testing – among oth-ers on the special issue 296 ”Ultrason-ic testing of spot-welded joints on coat-ed steel sheets and optimization ofwelding parameters”. You may now ob-tain from us our special issue SD 297”Ultrasonic testing as a means of quali-ty assurance in resistance spot weld-ing” (author: Dipl.-Ing. H. Polrolniczak,Moers).

You will be informed about:

· Quality features in resistance spotwelding

· Measures aiming at quality ass-urance

· Comparison between mechanicaltesting using chisel and hammerand ultrasonic testing

· Ultrasonic testing of spot welds

The summary reads:

”For some time now, there has beenan exchange of experiences from thefield application at almost all Germanautomobile works, these experienceshave been mutually discussed, andopen issues have been clarified byjoint field-oriented studies.

The positive outcome of the tests andexperiments described in this treatiseshows that it’s possible to mark outan area in which a nondestructive ul-trasonic test can be carried out pro-ducing a sufficiently reliable test re-sult for the field application. The sys-tematically continued exchange of ex-periences will also allow conclusionsto be drawn on those cases in which atest is at present still too unreliable.Furthermore, it will be possible to re-duce the area where there is notenough knowledge of ultrasonic test-ing yet.

An important interim result of the pre-vious effor ts already applies to thepresent situation:

1. The nondestructive mechanicaltool test using chisel and hammercan be completely replaced withthe technically more revealing andmore economical ultrasonic test.

2. The number of destructive testscan be reduced by the use of ultra-sonic test techniques.

The required extent and degree of in-spector training is at the moment de-fined within the framework of a GermanWelding Association (Deutscher Ver-band für Schweißen - DVS) guideline”Inspector in resistance welding” whichis currently being worked out.

Well-trained inspectors and standard-ized test principles are indispensableprerequisites for a successful appli-cation of ultrasonic testing.

It is to be hoped that the necessaryscientific support for the clarificationof physical correlations be very soongiven with the same topicality and in-tensity as the intensive efforts withinthe industry.

The test results presented are part ofthe joint projects dealt with by theproject team called ”Exchange of ex-periences in ultrasonic testing”.

The tests were carried out by inspec-tors from AUDI, BMW, Daimler BenzAG, FORD, and VW, the preparation ofsamples and their mechanical testingbeing carried out by the Welding Re-search and Training Center (Schweiß-technische Lehr- und Versuchsanstalt- SLV) at Duisburg.”

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E C H O P U L S E S

Well armed for the year 2000Many people worldwide are expectinggigantic problems with the changeoverof time in our computer systems on the1st of January in 2000. Whether largedata processing systems or small mi-crocomputers – for example also in ul-trasonic instruments: all of them couldget into trouble with the changeover ifthere’s an electronic clock ticking in-side them.

Where can a problem occur? If theclock ticks silently on and only servesfor the time indication, nothing muchwill happen. The situation only be-comes delicate whenever the time isrequired for the data processing.Sor ting processes according to thedate are a typical application.

In earlier times, the year was only pro-cessed in two-digit numbers in orderto save precious memory space.Dates indicated as 01.01.99 are stillcommon nowadays. The changeoverfrom 31.12.99 to 01.01.00 makesthe problem clearly visible: many com-puters assume a step back into theyear 1900...

The time plays an important part inmany processes of our everyday life:reminders and interests depend on it.Just imagine yourself ordering and re-ceiving an article in December, 1999,but not paying for it until in January,2000. A computer having a ”year-2000 problem” could draw up a re-minder for you requiring interest pay-able on arrears on account of a de-fault in payment for over 99 years...

How can we protect ourselves againstthis problem? The very first thing is toattach importance to a 4-digit numberof the year! Most computers allowthis to be done even afterwards. Thecomputer should then get a chance ofexperiencing the turn of the milleniumboth when it’s switched on and whenit’s switched off. Simply watch whatyour unit or computer does when youset the clock to 23:55 and31.12.1999. Does it run on into thenext millenium after five minutes with-

out any problem? Apart from this,does it recognize 29.02.2000 as anadditional day of the leap year 2000?

We have already carried out thesetests on our products. The reactionsof each individual instrument or unitwas documented in a quite compre-hensive list. In that way, instrumentsor units not having any clock at all –and consequently no problem with theyear 2000 either – were identified. Wehave provided space for remarks in aseparate column if anything specialshould be taken into account with aunit or instrument in view of the turnof the millenium.

How can you get this list? Go to the In-ternet! Select our home page at theaddress:

http://www.krautkramer.com.

You will find the introduction to thechapter “Year 2000 Readiness” righton the first page there. At the end ofan extensive discussion of the topicyou will find the list you are looking forunder the heading “Krautkramer Prod-ucts year 2000 status”. Regular up-dates make sure that the latest find-ings are documented in this list.

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E C H O P U L S E S

The KrautkrämerUltrasonic Booklet

We are prepared for the year 2000.For more than a year, a specializedteam has examined all conceivable in-fluences of the turn of the year 2000within Krautkrämer and worked outsolutions for it.

By the way...In the Internet you will find a lot moreinteresting information, ideas andproblem solutions on our pages.

just click us at:

http://www.krautkramer.com.

The Krautkrämer booklet can alreadylook back on a long history and hasbeen a faitfhful companion to manyan inspector – and not only to them -in the course of the years.

As the changing times have to be tak-en into account in this booklet aswell, a new edition of the booklet wasbrought out in German and in Englishthis year.

Typographical errors were corrected,the references updated, and the cur-rently valid standard specificationsand rules for ultrasonic testing weretaken into consideration.

These booklets can be ordered at atoken fee from the KrautkrämerGmbH & Co. oHG at Hür th in German(order number 28643) or in English(order number 28644).

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With smalland large calibreThe ultrasonic test doesn‘t determineany absolute physical quantities (theonly exception being the time-of-flightmeasurement). The test results musttherefore usually be referred to refer-ence blocks and reference reflectors.

This means that the reliability of thetest results is directly dependent onthe reliability of the reference materi-al and on the calibration of the testequipment.

These reference blocks and adjust-ment procedures must therefore alsobe standardized in the course of theeconomic globalization. This takesplace both worldwide through the ISOstandardization comprising 130 mem-ber countries (International Organiza-tion for Standardization), and in Eu-rope through the CEN standardizationcomprising 19 member countries (Co-mité Européen de Normalisation).

The weld inspection makes up thelargest sector of ultrasonic testing.That is the reason why the referenceblocks for weld inspection were givenpriority in the standardization pro-cess.

There are two blocks of this type,which are now called calibrationblocks because they are defined asreference standards in internationalstandard specifications: the calibra-tion blocks no. 1 and no. 2, or shortK1 and K2:

• DIN EN 27963 (identical with ISO7963), issue June 1992, Weldedjoints in steel – calibration blockno. 2 for the ultrasonic testing ofwelded joints.

That means that there’s only onestandard worldwide for this applica-tion.

The block has the known shapewith a thickness of 12.5 mm andthe circular arcs of 25 mm and50 mm radius. The bore hole diam-eter is 5 mm.

• DIN EN 12223 (final draft 1998),Nondestructive testing – ultrasonictesting – description of the calibra-tion block no. 1.

This block has likewise the knownshape with a thickness of 25 mmand a length of 300 mm. However,it no longer has an insert made ofplexiglass. The bore hole diameteris now 3 mm.

The sound velocities of the two blocksmust be within the following intervals:

• for longitudinal waves(5920 ± 30) m/s,

• for transverse waves(3255 ± 15) m/s.

Since the reliability of weld testing de-pends on the uniformity of the calibra-tion blocks, as mentioned previously,very strict standards are applied tothe process inspection of theseblocks at Krautkrämer:

• Both calibration blocks are made ofthe same steel quality by Krautkrämer(S355JO according to EN 10027).The blanks are heat-treated andforged to produce a fine micro-structure.

• The plates are completely checkedfor any internal inclusions (usinglongitudinal waves of 10 MHz).

• The sound velocities are very accu-rately determined at several pointsin the main axes of the calibrationblock (by measuring the thickness-es and the echo times of flight).

• The measurements for transversewaves are carried out using two po-larizing directions perpendicular toone another at every measuringpoint.

• The dimensions, the scales andthe plane-parallelism of the fin-ished calibration block are checkedusing special gauges.

A single out-of-tolerance value will beenough to make the block become areject item, no matter if it were dimen-sional imperfections, variations in ve-locity, or internal inclusions.

With clear conscience, Krautkrämercan therefore declare its calibrationblocks to be in conformity with thestandards mentioned above.

Calibration block no. 1 (K1)according to DIN EN 12223,order number 59108

Calibration block no. 2 (K2)according to DIN EN 27963,order number 50434

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Tracking down the holesGetting under the rind of cheese that went wrong: thanks toULTRASONICS, its ripening can be tracked down to every detail.By Gaby Schweizer

We recognize the Appenzell cheese byits pin-sized holes, the Sbrinz by itsbrittleness. Not every cheese is nev-ertheless flawless: sometimes theAppenzell lacks holes, or the Gruyèreis full of cracks. After months of careand attention, such a cheese that hasgone wrong must be sold off at a lowprice. It causes problems with the au-tomatic packing, or it can only beused as raw material for ready-to-serve fondue.

The problem is caused by the factthat milk is non-transparent. The rip-ening cheese doesn’t reveal its innerlife which has possibly lost its bal-ance, faulty developments may re-main unnoticed until the end.

Swiss scientists aim to remedy this.They have developed an ultrasonicmethod which listens to the cheeseduring the ripening process and im-mediately detects any cracks. It is thesame ultrasonic method that enablespregnant women to look into their bel-lies.

In Switzerland, one to two percent ofthe cheeses are downgraded in value.This cheap cheese weighs heavy: inthe winter of 1996/97 alone, around90 tons of Gruyère were stirred intocheese spread, and nine tons werefed to pigs.

Up until today, it has been the humanear that scanned the cheese forflaws. The cheese is tapped on eitherside with a hammer, and the muffledecho is listened to. Experts are ableto hear cracks within the first few cen-timetres under the rind by this meth-od. In the case of doubt, the personexamining the cheese takes a drill ora plugger. If the ten centimetre long”plug” pulled out of the cheese is toobrittle or too cracked, the chances ofthe cheese to be rated first-classdwindle. The disadvantage of this

method: for example with Gruyère, itis only used after three months – anyfaulty developments or malformationscan no longer be reversed or correct-ed at this point of time. Moreover, thedrill destroys a small part of thecheese.

Scientists from the Swiss ResearchInstitute for Dairy Farming (Forschungs-anstalt für Milchwirtschaft) at Liebe-feld have now developed a method oflistening which is superior to the hu-man ear: Bruno Albrecht and his staffuse an ultrasonic probe to listen tothe cheese. Ultrasonic waves havesuch a high frequency that they can-not be perceived by the human ear.The electronic ear is placed on therind of cheese to sound out fracturesif any. The emitted sound waves prop-agate through the cheese at a speedof 5,760 kilometres per hour. Shouldthey hit an inter face – where air orgas par t from the cheese dough –they are reflected. The echo tells thescientists where cracks or faultyholes have slipped inside the cheese.”This method allows us to track downvery small cracks already in the earlystages of storage”, says Albrecht.

The cheese-maker can intervenequickly in this case and, for example,reduce the storage temperature.

It is to be assumed that only a smallgroup of cheese-lovers will be unhap-py about the new method of detectingcracks in cheese: Albrecht has indeedalready talked to people ”who ratherprefer their Gruyère with lots ofcracks”.

Fig. 1: Like during pregnancy. Bruno Albrecht from the Research Institute for Dairy Farming(Forschungsanstalt für Milchwirtschaft) listening to the ripening of cheese.

Fig. 2: Early detection of cracks in a wholecheese. The sound waves propagatethrough the cheese at 5,760 kilometresper hour. As soon as they hit a crack, they’rereflected from it.

Published in Facts (Switzerland) 39/1998.Off-print by kind permission of the author.

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E C H O P U L S E S

Nothing but a cheesy story?Luckily a fat profit!The early days of not all too ordinary ultrasonic tests.

... given by Krautkrämeryesterday, today,and tomorrow

Ultrasonicimpulses

50 years experience in nondestructivematerials testing, 50 years experience ofservice for quality and safety. We havealways been able to give impulses with ourinnovative products ever since the pioneerdays, and we shall continue along on thisroad in future as well. One example of ourforward-looking products is our UltrasonicNotebook USLT 2000, a milestone ofultrasonic progress worldwide.

The techniques and the appearance of thetest equipment may have changed in thecourse of time, but the principle has alwaysremained the same: our instruments andsystems serve the quality of your products,they serve your safety and the safety of all.

We have accomplished our work in adialog with you, our customers. Therefore,we would like to express our thanks.

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