外文翻译--织机打纬机构的计算机辅助分析 英文版.pdf

http:/trj.sagepub.com/TextileResearchJournalhttp:/trj.sagepub.com/content/68/9/630Theonlineversionofthisarticlecanbefoundat:DOI:10.1177/004051759806800902199868:630TextileResearchJournalYoujiangWangandHuiSunComputerAidedAnalysisofLoomBeating-upMechanismsPublishedby:http:/www.sagepublications.comcanbefoundat:TextileResearchJournalAdditionalservicesandinformationforhttp:/trj.sagepub.com/cgi/alertsEmailAlerts:http:/trj.sagepub.com/subscriptionsSubscriptions:http:/www.sagepub.com/journalsReprints.navReprints:http:/www.sagepub.com/journalsPermissions.navPermissions:http:/trj.sagepub.com/content/68/9/630.refs.htmlCitations:WhatisThis?-Sep1,1998VersionofRecord>>trj.sagepub.comDownloadedfrom630ComputerAidedAnalysisofLoomBeating-upMechanismsYOUJIANGWANGANDHUISUNSchoolofTextile&FiberEngineering,GeorgiaInstituteofTechnology,Atlanta,Georgia30332,U.S.A.ABSTRACTAnalysisanddesignofthebeating-upmechanismisofgreatimportanceforim-provingloomperformance.Computeraideddesignandanalysistoolsareusedtostudydifferentkindsofbeating-upmechanisms,includingthe4-linkand6-linksystems,andtheircharacteristicsarecomparedwiththoseoftheconjugate-cammechanism.Resultsfrommodelswithvaryinggeometricparametersarepresented,revealingthatthecom-putertoolsareeffectiveandusefulinanalyzinganddesigningbeating-upmechanismswithsmootheroperation,lowernoiseandvibration,andhigherspeeds.Thelastdecadehaswitnessedthetransformationof,thetextileindustryfromalaborintensiveoneintoahighproductivity,capitalintensiveindustry.Inmanu-facturingwovenfabrics,thereisaconstantdesireforhighperformanceloomsthatarefast,energyefficient,reliable,highlyautomated,quiet,durable,andlowmaintenance.Overthelastfewdecades,theproductionrateofloomshasincreasedtremendously,withmaxi-mumweftinsertionratesmovingfromabout200.towellover2000m/min.Suchasignificantimprovementinperformanceisaresultoftechnologicalinnovations(e.g.,shuttlelessweaving),employmentofnewtech-nologies(e.R.,computersandmaterials),andbettermachinerydesigns.Regardlessofthekindofloom,itstechnologicalstate,orthepatterntobewoven,thebasicweavingoperationsconsistsoffoursteps:shedding,picking,beating-up,andtaking-up/letting-off2J.Theshed-.dingoperationraisesandlowersspecificwarpyarnsbymeansofharnessestoformashed.Duringthepickingstep,thenewfillingyamisinsertedthroughtheshed.Beating-upoccurswhenthenewlyinsertedfillingyarnispushedfirmlyinplacebymeansofthereedmountedonthesley.Finally,thefinishedfabriciswoundonthe；clothbeam.whilemorewarpyarnisreleasedfromthe:warpbeam.Thesefouroperationsareperformedina¡.constantlyrepeatedsequence.Beating-upisofgreatimportancetotheweavingprocessandthequalityoftheproduct.Anormalbeat-ing-upoperationwillgiveafirm,uniformfabricstruc-ture.Inaddition,themovementofthereedcarriedbythesley,throughwhichbeating-upisachieved,hasanimportanteffectonthe.smoothnessofsheddingandpickingoperations.Inhighspeedweaving,therelativetimepercycletakenbyoperationsotherthanpickingshouldbeminimized.Itisdesirablethatthereeddwell；aslongaspossibleatthereartoleavemoretimeforweftinsertion,andthenmoveswittlytobeatupthenewfillingyarn.Thisisespeciallycrucialformodernwide-widthlooms.However,higherforcesandvibra-tionsareassociatedwithjerkymovements,anddesigncompromiseisnecessarytoachieveabalancebetweenloomspeedandsmoothoperation.Dynamicanalysisofthemotionofthesley(reed)isthereforeimportantforloomdesignersandmanufacturers.Ingeneral,therearethreebasickindsofbeating-upmechanisms:4-link.6-link,andconjugate-carn,asshowninFigure1.The4-linkmechanismisusedmostwidelyonshuttle,air-jet,andrapierlooms.sinceithasasimplestructureandiseasytomanufacture.The6-linkmechanism,whichmayprovidealongerdwellpe-riod,ismainlyusedinair-jetlooms.Theconjugate-cammechanismisbeingusedmoreandmorewidelyinshuttlelessloomsduetoitspreciseandadjustabledwellperiodofthesley.Thedesignofbeating-upmechanism；,particularlytheirmassdistributionandgeometry,hasasignificanteffectontheperformanceoftheloom.Traditionalmethodsforanalyzingthesemechanismsbasedonki-nematicanddynamicprinciplesarewellestablished,butofteninvolvelengthymathematicalderivations.Computeraideddesignandanalysistoolsprovideasimplerwayofanalyzingthedynamicresponsesofcomplexstructures.WorkingModel,asoftwareproductofKnowledgeRevolution,Inc.11.combinesadvancedmotionsim-ulationtechnologywithsophisticatededitingabilitiestoprovideausefultoolforengineeringandanimationsimulation.Amechanismcanbeconvertedintoasetofrigidbodiesandconstraintstobuildthemodelonthecomputer.ThissoftwaresimulatesthemotionofthemechanismbasedongeometricconstraintsandNewtonianmechanics.principles.Quantitiesdefinedbeforethesimulationcanbeexportedduringthesim-trj.sagepub.comDownloadedfrom631FIGURE1.Typicalbeating-upmechanisms:(a)4-link,(b)6-J.ink.and(c)conjugate-camulatingprocessforfurtheranalysis.Thepropertiesofobjectscanbeadjustedwithitsgraphicuserinterfacetoformnewmodelswithdesirableresults.Inthisstudy,wefirstanalyzethe4-linkmechanismusingtheWorkingModelsoftware.Aparametricstudyexplorestheeffectofgeometryonthesleysmotion.Wealsobuildmodelsforthe6-linkmechanismtoiden-tifygeometricconfigurationsthatcanleadtoalonginsertionperiodinaweavingcycle.Finally,wecom-parethesleysmotionfordifferentbeating-upmech-anisms.Beating-upMechanismsFOUR-LINKMECHANISMFigure2showsthecomputermodelobtaineddafterimplementingallpartsofa4-linkmechanismwithWorkingModel,accordingtotheactualsize；mass,andconnectiontype.Quantitiesmeasuredandrecordedduringthesimulationincludethedisplacementofthesley(X),thevelocityofsley(V),theaccelerationofsley(A),andtheforce(F)actingontheswordpin.TovalidateWorkingModel,wehavecomparedtheresultsfromtheWorkingModelsimulationandkinematicsanalysisandfoundnonoticeabledifferences.Forparametricstudies,wehaveusedtheactualdi-mensionsofmachinepartsinashuttleloom(FigureIa)-crankshaftlengthr=6cm,connectingrodlengths=32cm,andsleylengthL=72.11cm.Thisgeometricconfigurationisthereferencefortheperfor-mancecomparisonwithothermodels.Wehaveas-sumedthattheloomspeedis200rpm.Toobservetheinfluenceofdifferentratiosofslronthemotionofthesley,theconnectingrodlengthvariesfrom17to102cm,whilerandLarekeptconstant.Wehaveevaluatedelevemmodelswiths/rratiosfrom2.83to17.FIGURE2.Computermodelof4-linkbeating-upmechanism.FromtheWorkingModelsimulationdata,wehaveobtainedthemaximumvaluesofsleyvelocityV,ac-celerationA,andtheforceintheconnectingrodF,foreachmodel.TheresultsareshowninFigure3,nor-malizedwithrespecttothereferencemodel.Becauses/rvariesfrom2to8,themaximumvaluesofV,A.andFdecreasesignificantly.However.thereislittlechangeinVmax,Amj,andFmaxasslrincreasesfurther.Toensuresmoothfillingyaminsertionthroughtheshed,theshedshouldbekeptlargeenoughduringthefillingtraverse.Thesizeoftheshedisdeterminedbytheheightbetweenthetwosheetsofyamsandthepo-trj.sagepub.comDownloadedfrom632FIGURE3.Effectofgeometricra-tio.s/ronsleysmotioncharacter-istics.sitionofthesley.Duringaweavingcycle,thefillingyamcanonlybeinsertedwhenthesleystayscloseto.；thebackwardpositionandtheshedopeningissuffi-cient.Thus,forfastloomoperation,thesleyshouldstaybackwardmostofthetimeforfillinginsertion,andthenmoverapidlyforbeating-up.Theexactrangeofsleypositionsallowingfillinginsertiondependsontheparticulardesignofaloom.Inthisanalysis,wehaveassumedthatthefillinginsertioniscompletedduringtheperiodwhenthesleyisinthe&dquo；backzone&dquo；betweenitsoriginal(mostbackward)positionandone-halfof.itsmaximumdisplacement(Figure4).Thecorre-:.spondingperiodisreferedtoastheinsertionperiod.Fromthesimulationdataonthedisplacementofthe.sley.,weseethatthesleyreachesonehalfitsmaximum.displacementatdifferentdegreesofthecrankrotation,dependingonthegeometryofthe4-linkmechanism,.assummarizedinTableI.Withincreaseds/r,thesleystaysnearitsmostbackwardpositionforashorterFIGURE4.Effectofgeometricratiosironthedisplacementprofileofthesley.TABLE1.Insertionperiodsfordifferent4-linkmodels.amountoftime,leavinglesstimeforthefillingtobeinsertedacrosstheloom.Nomatterwhatmechanismisdiscussed,alowerAmaxindicatesasmoothermovementandahigherA,leadstoajerkyaction.Foraloominparticular,themove-mentofthesleyaffectstheefficiencyofbeating-up.Fordifferentfabrics,however,differentactionsofbeat-ing-uparedesired2.Afine,delicatefabricshouldnotbehandledroughly,whereasacoarsestapleyammayrequiresharpbeating-uptobeeffective.There-fore,forlightfabricssuchassilkandfinecotton,onlyverygentlebeating-upisrequiredandalargesli-valueissuitable(e.g.,>6).Formediumfabricssuchasme-diumdensitycotton,asmoothbeat-upisneeded,andtheslrratioshouldbemedium(e.g.,between3and6).Forheavyfabricssuchasjeansorindustrialma-terials,animpulsive,jerkysortofbeat-upisnecessary,andasmallslrratioismoreappropriate(e.g.,<3).Forawideloom,whichneedsalongtimeforthefillingtobeinserted,alowerslrratioshouldbechosen.Incontrast,ahigherslrratioissufficientforanarrowloom,whichrequiresashorttimeforfillinginsertion.TheperformancemapshowninFigure5isobtainedbycombiningtheeffectsofthegeometric.s/rratioonthesleysmotionandinsertionperiod.Thehorizontalaxisisthemaximumforceactingonthepinjointoftheconnectingrodandthesley.Thelongitudinalaxistrj.sagepub.comDownloadedfrom