信息对抗技术专业毕业设计英文翻译说明.docx

信息对抗技术专业毕业设计英文翻译说明.docx

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信息对抗技术专业毕业设计英文翻译说明

Theultrasonicwavepropagationincompositematerial

anditscharacteristicevaluation

JunjieChang,ChangliangZheng,Qing-QingNi

1.Introduction

FRPcompositematerialswereappliedtovariousfields,suchasaircraftandspacestructures,becauseoftheexcellentcharacteristics,e.g.,light-weight,highratioofrelativeintensityandhighratioofrelativerigidity.DespiteFRPhavingsuchoutstandingcharacteristic,cracksinthematrixandfracturesofthefibermakedebondingsuchkindofdamageeasytooccurbetweenthefiberandthematrix,orthemulti-layers.Thesedamagesaredifficulttobedetecteddirectlybyvisualinspectionfromthesamplesurface,causingtroubletoensurethereliabilityandsafetyofthecompositematerialandstructures.Meanwhile,healthmonitoringtechnologiesofmaterialsareindispensable.Amongthem,theultrasonichealthmonitoringtechnologyattractslotsofattentionsinrecentyears.Simulationsbyfiniteelementmethodhavebeenperformedforthedevelopmentofapparatusforultrasonicdamage-detection,suchasultrasonicpictureinspectionandultrasoniclaser,andfortheverificationoftheirsafetyandvalidity.Researchesandcalculationsonthepropagationanalysisoftheultrasonicwaveinfiberstrengtheningcompositematerialshavebeenwellconductedandreported[1–8].

Onthesolidinterface,twokindsofboundariescanbeconsidered.Oneisliquidcontactinwhichthinlubricantisplaced,andonlypowerandpositionmovementperpendiculartotheinterfacearetransmitted.Theotheroneiscompletesolidcombination,whichpowerandpositionmovementbothperpendiculartoandparalleltotheinterfacearetransmitted.Fiberstrengtheningcompositematerial,theinterfacebetweenthefiberandthematrixcanbeconsideredtobesolidcontact.Inthecaseof,debondingexistingbetweenthematrixandthefiber,fewliteratureswerefound,sincetheconversionsofthetransmittedwavemode,reflectionwavemodeandreflectionpulsephase（waveform）maketheanalysisverycomplicated.Providedthisproblemtobesolved,thequalityofthematerials,tosomeextent,canbeestimatedfromthesoundimpedanceofthereflectorandthetransmissionobject,andtheoptimaldamage-detectionmethodcanbealsoassumedinasimulation.

Inthisresearch,inthesimulationofthetechniquemonitoringthehealthbyanultrasonicwavemethod,theultrasonicwavedistributionpatternwasanalyzedwiththebasictheoryforwavepropagationbyusingthemodelforfiberstrengtheningcompositematerial.Namely,itaimsatobtainingtheamplitudeofthereflectionwaveandtheamplitudeofatransmittedwave,whenthelongitudinalwavehasunitamplitudeincidenceinmodelcompoundmaterial.Inthecaseofanultrasonicwavepropagationinsideamodelmedia,theratesofthereflectivelongitudinal,reflectivetraversewave,transmissionlongitudinalwaveandatransmissiontraversewavegeneratedatageneralincidenceangleintheinterface（afiberandexfoliation）wereanalyzedandreflectivecoefficientandatransmissioncoefficientweregotten,respectively.Visualizedstudiesseparatingintoalongitudinalwaveandatraversewavewerecarriedout,andthemechanismsofalongitudinalwavedistributionandatraverse-wavedistributionwereelucidatedwhentheultrasonicwavepropagatedinsideacompositematerial.

2.Ultrasonicwaveequations

Considerasinglefibercomposite,i.e.,asinglefiberisembeddedinamatrix.TwodimensionsanalysisisconductedasshowninFig.2.Inthiscase,whenanultrasonicwavepropagatesinthissolidmedia,fromHooke’slaw,thestress–strainrelationshipfortwo-dimensionalplanestraininanisotropicmediaiswrittenasfollows[2]:

（1）

（2）

（3）

（4）

WherekandlareLame′constants,andtheTsuperscriptdenotesthetransposition.

Theultrasonicwaveequationsofmotionfortwodimensionalplanestraininanisotropicmediaareasfollows:

（5）

Where,thefirsttermontheleft-handsideofEq.（5）correspondstoalongitudinalwave,andthesecondtermcorrespondstoatransversewave.

isdensity.Ifthelongitudinalwavevelocity

andtransversewavevelocity

areintroducedtheultrasonicwaveequationsofmotionfortwo-dimensionalplanestraincanberewrittenby

（6）

Inthecaseofaplaneadvancingwave,thefollowingformulaisusedtocalculatefortheoscillatingenergygeneratedbytheultrasonicwaveperunittime:

（7）

3.Resultsofanalysisandsimulation

3.1.Transmissionenergyindifferentinterfaceshapes

Whenanincidentverticalwaveisobliquelyirradiated,fourwavesasshowninFig.3,i.e.,reflectedlongitudinalwave,reflectedtransversewave,transmittedlongitudinalwaveandtransmittedtransversewave,wouldappearontheinterface.Inotherwords,theshapeoftheinterfacebetweenepoxyandglassmayinfluencethepropagationoftheultrasonicwave.Forthisreason,themodelwithdifferentinterfaceshapesasshowninFig.1wasusedtoinvestigatetheinfluenceofinterfaceshapeonwavepropagationbehavior.Thevolumefractionproportionofbothmaterialsis1:

1,despiteofthedifferentinterfaceshapesofthethreemodels.Thatistosay,theglass-volume-percentageofallthemodelsis50%.ThepropertiesofeachmediumusedintheanalysisareshowninTable1.Asaboundaryconditionofthemodel,absorptionisconsideredontherightandleftedge,whileitissymmetrical（theroller）ontheupanddowndirection.TheanalyticconditionandtheinputparameterswereshowninTable1.

Fig.2showsthetransmissionenergyoftheultrasonicwavepropagationforthesefourmodelsshowninFig.1.

Fig.1.Fourdifferentinterfaceshapesbetweenepoxyandglass.

Herethetransmissionenergywasdefinedbytheaverageenergyperunitarea,lJ/mm2,atthereceiveredge.Asseen,inModel1,theincidentultrasonicwaveisperpendiculartotheplaneinterface,andtransmittedwaveoccursalongwholeplane,sothatthetransmissionenergyisfarlargerthanthatintheothermodels.Thefull-reflectiontakesplaceinpartofinterfaceinbothModel2andModel3whentheincidenceangleislargerthanthecriticalanglebecausetheultrasonicwaveradiatesobliquelyonaconvexorconcaveinterface.Aboutonethirdoftheincidentwaveexperiencesfull-reflectioninModel2andModel3.However,thetransmissionenergyofModel3islargerthanthatofModel2.AsecondpeakappearsinthetransmissioncurveofModel3.Peak1isareflectedwavethatpropagatesasasecondarywavesourceneartheup-down-wardinterface（intheglassregion）,whilepeak2isatransmittedwaveinthecentralpartoftheglassregion.Thereasonmightbethatneartheinterface,arefractiveindexdistributionoccurs,resultingintheappearanceofthescatteredwaves,includingrefractionandreflectionwaves.

Thefull-reflectiontakesplaceininterfaceofModel4（incidenceangleis45_）.Allprimaryincidentwaveswerereflected,andtheverysmalltransmissionenergythatshowsasfigureisbecausethedispersionwaveandthereflectedwavepenetratedthepartassecondarywavesourcefromtheverticalneighborhood.

3.2.Influenceofdifferentfiberconditions

Refractiveindexdistributionoccursnearthesecondphaseboundaryduetothesecondphasecompounding,resultingintheappearanceofthescatteredwaves,includingrefractionandreflectioninthecompositematerialsstrengthenedbyfibers.Inthenext,thescatteringoftheultrasonicwaveshowninFig.1willbetakenintoconsideration.Thescattersoccurduetofibersembeddedincompositematerials.Theincidentwave

propagatinginmatrixregion,isasinusoidalwave.Whentheincidentwavereachesthefiber,someistransmittedintothefiber,andtheotherisreflectedonthefiber/matrixinterface,andbecomesasecondarywavesource.Accordingtotheoverlappingprincipleofwavefunctions,thewholewavefunction

canbeexpressedasasumoftheincidentwave

andthescatteredwave

.

（8）

Wherethescatteredwave

includesallthewavesscatteringcomponentsgeneratedduetotheinterfacefromtheknownwave

.

ThemodelfigureofthecompositematerialsfortheinvestigationofthescatterswasdesignedaswhatshowninFig.3,wherethreefiberswithdifferentshapeswereembeddedinthematrix.Thesizeofthemodelwas

.Theboard-shapedglassfiberwiththickness

wasembeddedinthecenterofthematrixofepoxyinModel1,andwasobliquelyembeddedinModel2.Acolumnshapedglassfiberwithadiameter

wasembeddedinthecenterofmatrixinModel3.Theabovethreemodelshadacommonfiberpercentageof20.TheanalyticconditionandtheinputparameterswereshowninTable1.

ForthemodelsinFig.3,whentheincidentwaveontheleft-handsideoftheglassregionarrivedatthefirstinterfacebetweentheepoxyandglass,thetransmittedwaveandthereflectedwavearose.Thenthereflectedwavepropagatedtotheincidenceside,whilethetransmittedwavepropagatedtothereceiversideandarrivedatthesecondinterfaceoftheglassandepoxythroughtheglassregion.

Thesecondtransmittedwaveandthesecondreflectedwavearoseatthesecondinterface,andamultiplexreflectionoccurredintheglassregion.Fortheboard-shapedfiber（planefiber）andthecolumn-shapedfiber（cylindricalfiber）,Fig.4showsthecomparisonsoftheanalyticresultsinthecasesofModel1（fiberthickness

）,Model2（fiberthickness

_）andModel3（fiberdiameter

）inFig.3,withanequivalentfibervolumefractionbutwithadifferentshape.Asseenfromthefigure,thetransmissionenergyoftheModel1isfarlargerthanthatModel2andModel3.

FromFig.4,whichembeddedtheboard-shapedfiber,twoenergy