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外文翻译--翻车保护结构的动态响应 英文版【优秀】.pdf

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外文翻译--翻车保护结构的动态响应 英文版【优秀】.pdf

ComputerAidedCivilandInfrastructureEngineering232008448–464INDUSTRIALAPPLICATIONDynamicResponseofaRolloverProtectiveStructureDavidP.Thambiratnam∗BrianJ.ClarkSchoolofUrbanDevelopment,FacultyofBuiltEnvironmentEngineering,QueenslandUniversityofTechnology,Brisbane,AustraliaNimalJ.PereraSchoolofUrbanDevelopment,FacultyofBuiltEnvironmentEngineering,QueenslandUniversityofTechnology,Brisbane,AustraliaRobertBirdGroup,Brisbane,AustraliaAbstractRollOverProtectiveStructuresROPSaresafetydevicesfittedtoheavyvehiclestoprovideprotectiontotheoperatorduringanaccidentalrollover.Atpresent,ROPSdesignstandardsrequirefullscaledestructivetestingthatcanbeexpensive,timeconsuming,andunsuitableforsmallcompanies.MoreeconomicalanalyticalmethodsarenotpermittedduetoalackofunderstandingofpostyieldbehaviorandtheenergyabsorptioncapacityofROPS.Toaddressthis,acomprehensiveresearchprojectwasundertakentoinvestigateROPSbehaviorusinganalyticaltechniquessupportedbyexperiments.ThisarticlepresentsthedynamicimpactanalysisofabulldozerROPSusingcalibratedfiniteelementmodels.Resultsindicatethat1ROPSpostshavesignificantinfluenceontheenergyabsorbingcapacity,2dynamicamplificationsinenergycouldbeupto25,3stifferROPScausehighpeakdecelerationsthatmaybedetrimentaltotheoperator,and4analyticaltechniquesmaybeusedforevaluatingROPSperformance.1INTRODUCTIONHeavyvehiclesthatareusedintherural,mining,andconstructionindustriesaresusceptibletorolloversas∗Towhomcorrespondenceshouldbeaddressed.Emaild.thambiratnamqut.edu.au.theyhaveahighcenterofgravityandcommonlyoperateonslopinganduneventerrain.Asteelmomentresistingframewitheithertwoorfourpostsisusuallyattachedtothesevehiclesabovetheoperatorscabinforprotectionduringrollovers.ThissafetydeviceiscalledaRolloverProtectiveStructureROPSanditsroleistoabsorbsomeofthekineticenergyKEoftherollover,whilemaintainingasurvivalzonefortheoperator.ThedesignandanalysisofROPSiscomplexandrequiresdualcriteriaofadequateflexibilitytoabsorbenergyandadequatestiffnesstomaintainasurvivalzonearoundtheoperator.EvaluationtechniquesusedinthecurrentAustralianstandardforearthmovingmachineryprotectivestructuresAS2294–1997aresimplifiedandinvolvefullscaledestructivetestingofROPSsubjectedtostaticloadsalongtheirlateral,vertical,andlongitudinalaxes.Thestandardisperformancebased,withcertainforceandenergyabsorptioncriteriathatarederivedfromempiricalformulaerelatedtothetypeofmachineandoperatingmass.DeflectionrestrictionsarealsoemployedtoenableasurvivalspaceknownasthedynamiclimitingvolumeDLVtobemaintainedforthevehicleoperator.Thesesimplifiedprovisionsprovidedesignguidelinesthatwillsubstantiallyimprovetheoperatorschancesofsurvivalduringanaccidentalrollover.ThisformofcertificationcanbetimeconsumingandextremelyexpensiveC©2008ComputerAidedCivilandInfrastructureEngineering.PublishedbyBlackwellPublishing,350MainStreet,Malden,MA02148,USA,and9600GarsingtonRoad,OxfordOX42DQ,UK.Dynamicresponseofarolloverprotectivestructure449asestablishingtheforceandenergycriteriacaninvolvelargeloadsthatmaythereforerequiretheuseofaspecializedtestingfacility.CertificationofROPSbymoreeconomicalanalyticalmodelingtechniquesiscurrentlynotpermittedbyROPSstandardsforearthmovingmachinerybothinAustraliaandinternationally.Reasonsfortheexclusionareattributedtoalackofknowledgeandresearchinformationonthebehaviorofthesestructuresinthepostyieldregionandtheirenergyabsorptioncapacity.PreliminaryresearchhasshownpromisefortheuseofanalyticaltechniquestomodelthenonlinearresponseofROPS.TheseanalyticalmethodswereverysimplifiedandinvolvedtheuseofelastoplasticbeamelementstosimulatethebehaviorofROPSsubjectedtoastaticlateralload.Inrecentyears,substantialadvanceshavebeenmadeinbothcomputationalpowerandtheimplementationofadvancedelementtypesinFiniteElementFEtechniquesthatcanaccuratelymodelandpredictthenonlinearresponseofstructures,particularlyinthepostyieldregion.ResearchcarriedoutonROPSbehaviorusinganalyticalandexperimentaltechniquesincludethoseofClarketal.2006a,b,KimandReid2001,Tomasetal.1997,Swan1988,andHuckleretal.1985.AcomprehensiveresearchprojectwasundertakenattheQueenslandUniversityofTechnologytoinvestigateROPSbehaviorusingcomputersimulationssupportedbyexperimentsto1enhanceourunderstandingofROPSbehavior,2improveenergyabsorptionandsafety,and3generateresearchinformationtofacilitatethedevelopmentofanalyticaltechniquesfordesignandevaluationthatmaylessentheneedfordestructivefullscaletestingClark,2006a.ThisarticletreatsthedynamicresponseoftheROPSmodelforaK275bulldozer,usingcalibratedFEmodels.TheexperimentaltestingandcalibrationofthecomputemodelofthisparticularROPSmodelarereportedelsewhereClark,2006a,b.Thedynamicimpactloadsarecharacteristicofthosethatareexperiencedduringthesidewardsrolloverofavehicleonafirmslope.AsimplifiedmethodbasedonaconservationofangularmomentumapproachreportedbyWatson1967isusedtoestimatethedynamicimpactparametersfortheROPSduringasidewardsoverturn.TheexplicitFEcodeLSDynav970wasusedtoconductthenecessarydynamicimpactmodelingforrolloverimpactsonfirmslopeswithinclinationsof15◦,30◦,and45◦.TheinfluenceofcontrollingvariablessuchasROPSstiffness,impactvelocity,anddurationandrollslopeangleonthedynamicresponseoftheROPSwasstudied.Theresultsarecomparedwiththosefrompreviousstaticanalysistoestablishtheeffectofpossibledynamicamplificationsandtheadequacyofcurrentstandardprovisions.1.1DynamicfiniteelementanalysisRolloversimulationusingFEanalysishasreceivedlittleattentionfromresearchers.Chouetal.1998highlightedthatthemajordifficultyassociatedwithusingFEforrolloveranalysiswasthelargesimulationtimerequiredtocapturetheeventaccurately.Indirectparalleltothis,Klose1969alsoemphasizedthattherolloverprocesswasextremelydifficulttomodelasitinvolvedthecomplexinteractionofnumerousparametersthatinfluencedthebehavioroftherollingvehicle.Intheopenliterature,theFEmodelingofrolloverprotectivestructuresunderdynamicloadinghasbeenlimitedtoresearchperformedbyTomasetal.1997andHarrisetal.2000.TheworkperformedbyHarris2000examinedtherearwardrolloverofatractorwhereasTomassresearchusedtheprogramMADYMOtostudytheeffectofROPSstiffnessandoccupantrestraintduringthesidewardsrolloverofanearthmovingmachine.AlthoughthemodelingtechniquesemployedbyeachoftheseauthorshaveassistedwithassessingtheperformanceofROPSundersimulateddynamicimpactloads,littlecomparisonhasbeenmadewithreferencetotheadequacyofthestaticloadingproceduresadoptedincurrentROPSstandardsandthepossibledynamicamplificationsthatmaytakeplaceduringsuchloadingconditions.WiththeseviewsinmindthesimplifiedprocedureproposedbyWatson1967isusedasabasisforadynamicimpactstudytoinvestigatetheinfluenceofcriticalparametersthatcontroltheresponsebehaviorofROPSsubjectedtosuchloadingconditions.2ROPSFORK275BULLDOZERTheK275bulldozerisacrawlertypedozerwithagrossvehicleweightofapproximately50tonscommonlyusedintheconstructionandminingindustriesforearthmovingpurposes.RolloverprotectionfortheoccupantisaffordedthroughatwopostrollbartypeROPS,whichisshowninFigure1.ThisROPSisprimarilyafixedbaseportalframe,consistingoftwopostsandabeam,rigidlyconnectedtothechassisofthevehicle.InadditiontotheROPS,anadditionalroofcanopysectionknownastheFallingObjectProtectiveStructureFOPS,isincorporatedtoprovideprotectiontotheoperatorunderfallingobjects.Inthisstudy,theFOPS,whichisaseparatedetachablestructure,wasomitted.TheoverallgeometryofthefullscaleK275ROPSmodelwasestablishedfromsitemeasurementstakenatthemanufacturersstorageyard.AppropriateRHS/SHSmembersizeswereselectedsothattheROPSwouldpossesssufficientstrengthandenergyabsorptioncharacteristicsthatwouldenableittosuccessfullypasstherequirementsoftheAustralianStandard.450Thambiratnam,ClarkPereraFig.1.K275bulldozerwithROPS.2.1HalfscaleROPSmodelPreviousresearchbySrivastavaetal.1978hasshownthatprinciplesofsimilitudemodelingcouldbesuccessfullyappliedtoROPStestingtechniques,andcouldleadtolargescaleeconomicsavings.BasedontheresearchfindingsoftheseauthorstheprinciplesofsimilitudewereappliedtotheK275bulldozerROPStolessenfabricationcostsandreducethemagnitudesofthetestloadstobeappliedtotheROPS.ReductioninthemagnitudesoftheloadswasessentialasafullscaletestofROPSforavehiclesuchasthiswasextremelylargeandwouldrequiretheuseofanextensivelaboratorytestingfacility.Ascalingfactorforsizewasthenselectedbetweenthemodelandprototypethatgaverisetothescalingfactorsof1/8forenergyabsorbedunderlateralload,1/4forloads,and1/2fordeflections.AhalfscalemodeloftheK275ROPSwithlength1,000mm,height900mm,andsectionproperties125755mmforthepostsand1251255mmforthebeam,wasdesignedandfabricatedandsubjectedtotheloadingandenergyrequirementsofAS2294–1997.ThemembertypesusedfortheROPSconsistedof350gradeRHSwithfullpenetrationbuttweldedmomentresistingconnections.ThehalfscaleK275ROPSmodelwasexperimentallytestedundertherequiredlateral,vertical,andlongitudinalloadsClark,2006a.TheloadandenergymagnitudesestablishedfromAS2294.2–1997weremodifiedtotakeintoaccountthesimilituderelationshipsestablishedforthismodel.Strainanddeflectionmeasurementswererecordedforeachloadingsequence.TheexperimentaltestingwasfollowedbyFEanalysisofthehalfscaleROPSmodelunderthesameloads,usingtheprogramABAQUSstandardv6.3.ScalinglawsfromthesimilitudestudyalongwiththeprogramMSCPatranwereusedtodevelopthenecessarygeometryfortheFEmodel.Figures2and3showtheexperimentaltestingoftheROPSmodelunderlateralloadandtheFEmodelofFig.2.LateralloadtestingofK275ROPS.thesameROPS,respectively.TherectangularportioninlightershadeatthetoprighthandpostintheFEmodelshowstherigidbodyusedtoapplythedynamicimpactloadingdescribedlateroninthearticle.ThelateralloaddeflectionplotsobtainedexperimentallyandfromtheFEanalysisshowninFigure4demonstrateexcellentagreementbetweenthetwosetsofresults.ThevariationofthestresswithloadatthebaseoftheROPSpostacriticalregion,alsoshowedexcellentagreementbetweentheexperimentalandanalyticalresultsClark,2006a.ThiscalibratedFEROPSmodelwasusedforthedynamicanalysisunderlateralimpactloads.Fig.3.FiniteelementmodelofK275ROPS.Dynamicresponseofarolloverprotectivestructure451Fig.4.LateralloaddeflectionresponsefromexperimentLVDT1andFEA.3DEVELOPMENTOFPARAMETERSFORDYNAMICIMPACTANALYSISFORK275BULLDOZERWatsonsprocedure1967basedonconservationofangularmomentum,isusedtodeterminetheimpactparametersfortheRPOSmodelforrollslopeinclinationsFig.5.aInitialrolloverconditions,bimpactonwheelatpointB,andcimpactonROPSatpointD.ofα15◦,30◦,and45◦.Thesimplifyingassumptionsofthisprocedureincludeneglectingforwardvelocity,useofatwodimensionalvehiclemodel,assumingthevehiclescenterofgravitytobedirectlyabovethepointofrotationatthewheeljustbeforetheroll,andtreatingthevehicleasarigidbodythatfallssidewaysfreelyundergravitywithnochangeinangularmomentumaboutthepointofimpact.3.1DerivationofK275bulldozerrolloverparametersFigures5a–cillustratethethreestagesintherolloverofavehicle,whichinitiallyrollsaboutA,thenaboutB,andfinallymakesimpactwiththegroundatDatwhichitalsorolls.LossinpotentialenergyGaininKEMgradicalbigx2y2bracketleftBig1−sinbraceleftBigtan−1parenleftBigyxparenrightBig−αbracerightBigbracketrightBig12Mk2x2y2ω2A.1Fromwhich∴ωAradicalBigg2gx2y2bracketleftbig1−sinbraceleftbigtan−1parenleftbigyxparenrightbig−αbracerightbigbracketrightbigk2x2y2.2

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