Inspection time optimization of advanced materials with ultrasonic phased array technology Kenny Van Heuverswijn Promotoren: prof. dr. ir. Joris Degrieck, prof. dr. ir. Wim Van Paepegem Begeleiders: Geert Luyckx, Ebrahim Lamkanfi Scriptie ingediend tot het behalen van de academische graad van Burgerlijk werktuigkundig-elektrotechnisch ingenieur Vakgroep Mechanische constructie en productie Voorzitter: prof. dr. ir. Joris Degrieck Faculteit Ingenieurswetenschappen Academiejaar 2007-2008 Inspection time optimization of advanced materials with ultrasonic phased array technology Kenny Van Heuverswijn Promotoren: prof. dr. ir. Joris Degrieck, prof. dr. ir. Wim Van Paepegem Begeleiders: Geert Luyckx, Ebrahim Lamkanfi Scriptie ingediend tot het behalen van de academische graad van Burgerlijk werktuigkundig-elektrotechnisch ingenieur Vakgroep Mechanische constructie en productie Voorzitter: prof. dr. ir. Joris Degrieck Faculteit Ingenieurswetenschappen Academiejaar 2007-2008 Acknowledgements This master thesis is the final piece of hard work to reach the degree of engineer. It was a challenging journey through numerous engineering topics including mechanics, electronics, informatics, physics and automation. I never walked alone and therefore, I wish to acknowledge the following persons. First of all, I would like to thank my thesis supervisors Ir. Ebrahim Lamkanfi and Ir. Geert Luyckx for the countless times we changed ideas, for their assistance on practical matters and for the time and effort they have put into proofreading my manuscript. Also many thanks to my promotors prof. dr. Ir. Joris Degrieck and prof. dr. Ir. Wim Van Paepegem for their guidance and constructive feedback. Furthermore, I thank technician Luc Vandenbroecke for his helping hand. It was a real pleasure working with him. Last but not least, I wish to express my sincere gratitude to my parents for their unconditional support and for giving me the opportunity to study. Additionally, I would like to send a special thanks to my girlfriend Jolien who stood by me in good and bad days. Kenny Van Heuverswijn Ghent, 10th of June 2008 iv Inspection time optimization of advanced materials with ultrasonic phased array technology KennyVanHeuverswijn Supervisor(s): prof. dr. Ir. J.Degrieck,prof. dr. Ir. W.VanPaepegem,Ir. E.LamkanfiandIr. G.Luyckx Abstract—Thisextendedabstractdescribestheimprovementstoanul- achievedontwoways: implementationofnewmotioncontrol- trasonicscaninspectionfacilityinordertospeeduptesting.Theseinclude linghardware,whichprovidesfasterpositionfeedback,andthe implementationofnewmotioncontrollinghardwareandtheuseofmulti- use of multi-element inspection by means of ultrasonic phased elementscanningwithultrasonicphasedarraytechnology.SeveralC-scans ofdamagedcompositematerialsmadewiththeimprovedfacilityarepre- arraytechnology. sented. First,themostimportantimprovementstotheultrasonicscan Keywords—ultrasonics;ultrasonicphasedarray;nondestructivetesting; inspection facility are discussed. Afterwards follows a closer LabVIEW;automation look at the test results obtained with a conventional ultrasonic apparatus (Krautkramer Branson USIP) and with an ultrasonic I. INTRODUCTION phasedarrayapparatus(OlympusNDTOmniscanMX). C OMPOSITEMATERIALScan be engineered to have a wide range of flexural, tensile and impact strength prop- erties. Additionally, theyarecorrosionresistanttomostchem- icals, donotsufferfromelectrolysisandincorporatelong-term benefitssuchasweatherabilityandUVstability[1]. Therefore, theyplayakeyroleinmanystate-of-the-artconstructions,such asairplanes,windturbinesandsailboats. Inaviationforexam- ple, the use of composites with high specific strength leads to significantweightandcostsavings[2]. Despite the enormous amount of advantages, special care should be taken when using composite materials because they canbedamagedwithoutanyvisualclue. Forexample,tooldrop onacompositewingskincaninternallyaffectthemechanicsof the structure without any visual prove. Secondly, damage can build-up gradually during use. Finally, discontinuities which ariseduringproduction,suchasdelaminationsorporosities,can formathreattothematerialsstrength. Asaconsequence,there is a need to monitor the internal health of the material during productionandin-servicetoensuresafety. [3][4] Ultrasonic nondestructive testing is one of the techniques usedtosearchforandlocateinternaldefectsordiscontinuities. Therefore, ultrasound is transmitted into a material and the re- flectionorthetransmissionisusedtoprovidedetailsonthein- ternalstateofthematerial. TheLaboratoryforMechanicalConstructionandProduction from Ghent University has an ultrasonic scan inspection facil- Fig.1. Communicationnetworkforultrasonicphasedarrayscanning. ity with five degrees of freedom which can be used to perform full automated ultrasonic nondestructive tests. Therefore, the transducer is continuously moved over the test specimen and II. IMPROVEMENTS the ultrasonic scan signals are saved together with the position A. Newmotioncontrollinghardware into files for further processing. The most important problem withthisfacilitywastheenormousinspectiontimeduetoslow The existing serial RS-232 connection between the motion positionfeedbackfromthemotioncontrolhardware,whichcon- controllersandthecomputerhasbeenreplacedbyaCAN1 bus trolsthemotors, tothecomputer[5][6]. Loweringtheinspec- systemwithahigherdatatransferrate(1MBit/sforCANcom- tiontimewasthemainobjectiveofthismasterthesiswhichwas paredwith19200kBit/sforRS-232). AlthoughCANcommuni- cationtakesmorebitstosendacontrolmessage,positionfeed- K. Van Heuverswijn is a final year mechanical engineering student at Ghent University (UGent), Gent, Belgium. E-mail: 1CANisshortfor’ControllerAreaNetwork’andisaserialdatacommunica- [email protected]. tionprotocolwhichwasinternationallystandardized(ISO118981)in1993. backtakesapproximately17timeslesstimecomparedwithse- rialRS-232communication(3msforCANcomparedwith50ms for RS-232). As a consequence, the scanning speeds for per- formingconventionalscansataresolutionof1mmand0.1mm arereducedtorespectively42mm/sand6mm/s. B. Multi-elementscanning An ultrasonic phased array apparatus (Olympus Omniscan MX) is integrated into the facility. The transducer connected to this apparatus has an array of 64 individual piezoelectric el- ementswhichcanbecontrolledindividually. Themainadvan- Fig.2. ConventionalultrasonicC-scanofimpactedGFRPplate.Left:reflection tageisthattheelementsalongthelengthofthetransducercan atcertaindepth.Right:reflectiononglassplateundertheGFRPplate. be pulsed quickly after each other to collect information over the complete length of the transducer without movement. Ad- B. Ultrasonicphasedarrayscans ditionally, the Omniscan can impose a phase shift between the pulsationofdifferentelementswhichallowstofocusandsteer ThesameimpactedGFRPplateistestedwiththeOmniscan theultrasoundbeam. [7] usinga64-elementlinearphasedarraytransducer. Theareaof The Omniscan needs external encoder feedback to construct 150mmx150mmwasscannedataresolutionof0.1mmwithin a scanning image and therefore, additional linear magnetic en- twoandahalfminutes. Foraresolutionof1mm,theinspection coders are installed. They provide a maximum resolution of timeisevenafactor10smaller. 5µm which is even better than the maximum resolution of the Omniscan (10µm). The scanning image is constructed in the Omniscan and the computer from the facility is used only for motioncontrolandpost-processing. Additionally, theinstalled encoders can also be used to speed up conventional ultrasonic scans performed with the conventional ultrasonic apparatus. Thecommunicationnetworkisillustratedinfigure1. C. Software New software has been written with LabVIEW to per- form completely automated conventional C-scans of rectangu- Fig. 3. C-scan of impacted GFRP plate made with ultrasonic phased array lar plates with the conventional ultrasonic apparatus as well as technology.Left:unfocusedscan;reflectionatcertaindepth.Right:focused withtheultrasonicphasedarrayapparatus. Thecommunication scan;reflectionatcertaindepth. betweenthecomputersoftwareandtheCANbusisdonewitha USB-to-CANdevicewhichrequiresmorecomplexmotioncon- Theresultofbothanunfocusedandafocusedscan(withfo- trol software. Extra features are added, such as the possibility cal point in the middle of the plate) is shown on figure 3 (the toperformadiagonalscantocheckthesetupparameters. Ad- lighter the color, the less energy is reflected to the transducer). ditionally,thesoftwarecanbeusedtoplotpreviousmadescans, Theimpactdamagecanbeseeninthemiddleofbothimagesas toshowprevioususedconfigurationparametersandtoplacethe alightercoloredzone. Thefocusedscanseemstoprovidemore probeperpendicularautomatically. details,howevertheinteractionofthesteeredandfocusedultra- soundbeamwiththetestspecimenneedsfurtherinvestigation. III. SCANNINGRESULTS IV. CONCLUSION A. Conventionalultrasonicscans Thismasterthesishaseffectivelyledtoanoptimizationofthe One of the first experiments was the detection of impact timeneededtoperformultrasonicscanswiththeultrasonicscan damage in a glass fiber reinforced plastic (GFRP) plate which inspectionfacility. Additionally,successfulCscansofdamaged showednovisualdamageontheimpactedside. Forthisexper- compositematerialshavebeenmade,bothwithconventionalul- iment,theUSIPincombinationwithaconventionaltransducer, trasonic technology and with ultrasonic phased array technol- which acts both as transmitter and receiver, is used. The new ogy. The knowledge gained of the Omniscan and the motion hardwareandsoftwareperformedwellforthisexperiment: the controlthroughCANcommunicationopensuppossibilitiesfor damage could be located and the test was performed with an further use and development of the inspection facility (eg. for acceptable scanning speed. The area of 150mm x 150mm was polarscansonwhichtheresearchgroupisworking). Itcanbe scannedataresolutionof1mmwithin15minutes. concludedthattheobjectivesofthemasterthesisareachieved. TheC-scanisillustratedonfigure2(thedarkerthecolor,the less energy is reflected to the transducer). The impact damage REFERENCES canclearlybeseeninthemiddleasablackzonewhichmeans [1] GeraldMyers,PaulSteinert.TheAdvantageofCompositeMaterialsinthe less ultrasound is reflected in that zone compared with other, Design, ConstructionandUseofHard-WallSheltersandContainerSys- lightercoloredzones. tems,http://www.alkanshelter.com/Advantage.pdf,October2003. [2] MartineSegers.Glaremaaktvliegtuigengoedkoper,TUDELTA33,2001. [3] NitinSharma,RolandF.Gibson,EmannuelO.Ayorinde. FatigueofFoam andHoneycombCoreCompositeSandwichStructures:ATutorial,Journal ofSandwichStructures8,pp.263-319,July2006. [4] J.Christophersonetal.AnInvestigationontheEffectofSmallMassImpacts onSandwichCompositePlates, JournalofCompositeStructures67,pp. 299-306,2005. [5] D.Vanleene.Optimaliseringengebruikvandeultrasoonopstellingbijhet onderzoekvanbeschadigdecomposietplaten,UGent,June2006. [6] G.Luyckx. OntwikkelingvanLabVIEW-programmatuurvoordesturing vaneenproefstandvoorultrasoononderzoek,UGent,June2003. [7] M.Moles,C.R.Bird. AdvancesinPhasedArrayUltrasonicTechnology Applications,R/DTech,Waltham,2004. Permission to loan “The author gives the permission to place this master thesis to someone his disposal and copy parts of this master thesis for personal use. Anyotherusefallsundercopyrightlaw, speciallywithregardtothelegalcommitmenttoclearly mention the source when using results from this master thesis.” The author Ghent, 10th of June 2008 viii Inspection time optimization of advanced materials with ultrasonic phased array technology by Kenny Van Heuverswijn Thesis submitted to reach the academic degree of Master of Science in Electromechanical Engineering: option Mechanical Construction Academic year 2007–2008 Promotors: prof. dr. Ir. J. Degrieck, prof. dr. Ir. W. Van Paepegem Supervisors: Ir. E. Lamkanfi, Ir. G. Luyckx Faculty of Engineering Ghent University Laboratory for Mechanical Construction and Production Chairman: prof. dr. Ir. J. Degrieck Summary Ultrasonic nondestructive testing is a method which makes use of ultrasound to search for and locate defects or discontinuities in a material without damaging it. Ultrasonic sound waves are transmittedintoamaterialandthereflectedorthetransmittedsoundwavesareusedtoprovide details on the internal state of the material. The laboratory for Mechanical Construction and Production has an ultrasonic scan inspection facilitywith5degreesoffreedomwhichisusedforultrasonicnondestructivetestingofcomposite materials. The largest problem with this facility was the enormous inspection time due to slow position feedback. Lowering the inspection time was the main objective of this master thesis, which was achieved in two ways: the inspection speed was raised with new motion control hardware and multi-element inspection was implemented by means of ultrasonic phased array technology. Thefirstchaptercontainsageneralintroductiontocompositematerialsandtheuseofultrasonic nondestructive testing for R&D and industry. Additionally, the objective of the master thesis is discussed. Being able to understand this master thesis into detail, the second chapter contains a short introduction to conventional ultrasonic testing and ultrasonic phased array technology. The third chapter contains the history of the ultrasonic scan inspection facility, a description of its components, the improvements done to the facility and a view on the new LabVIEW software for performing conventional ultrasonic C-scans on flat plates. The new hardware and softwarehavebeentestedextensivelyinchapter4, whichalsocontainstheresultofconventional ultrasonic scans of damaged composite plates. In chapter 4 and 5, the step to ultrasonic phased array technology is made. Chapter 4 contains x first an introduction to the Omniscan MX from Olympus NDT which is an ultrasonic phased array apparatus the laboratory recently has acquired. The rest of this chapter describes the integration of the Omniscan MX into the ultrasonic scan inspection, including the software writtenforperformingC-scansonflatplates. Theresultsofexperimentswiththenewtechnology are included in chapter 5. Chapter 6 contains ideas for further use and development of the ultrasonic scan inspection facility. The conclusions can be found in chapter 7. Keywords ultrasonics, ultrasonic phased array, nondestructive testing, LabVIEW, automation