汽车噪音震动论文英文版Word格式.docx
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汽车噪音震动论文英文版Word格式.docx
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Vehiclenoise,vibrationandharshness(NVH)isusuallythemajorattributebecauseofitspriorityinthedesignofvehicles.NVHaffectsthedesignandmanufactureprocessofavehicleashighercustomersatisfactionareattributedbyagoodNVHbehavior.TheresearchonNVHreliesonavarietyofcomputersoftwaretoimproveandcontrolNVH.Inthispaper,severalvehiclecomponentsincludingrubberdampersandisolatorswhichplayanimportantroleincontrollingtheNVHarepresented.AdescriptionofsourceofNVHinavehicleisshown.
Keywords:
NVH;
rubberdamper;
isolator;
research.
1.Introduction
Vehiclesconsistofspacevehicles,airplanes,submarines,trains,road,off-roadandothers[1].Vehiclenoise,vibration,andharshness(NVH)isamajorproblemintheautomobilemanufacturingprocessandaffectsthecustomersatisfactionofautomobileowners.Theresearchesofvehiclenoise,vibration,andharshness(NVH)arenotonlysuitableforthedesignprocessofnewautomobiles,butcontributetoimprovethecomfortandperformanceofcurrenttypeofautomobiles.Thoseresearchesarelargelyduetotheincreasingdemandsofvehiclemanufacturers,OriginalEquipmentManufacturers(OEMs)andcustomers.TheOEMsaimtolookfortheproductsthataddressissuesofNVH,reducevehicleweight,improvestiffness,andareeasytomodel,lowercosts,andareenvironmentallyfriendly[2].Automotivenoise,vibrationandharshnessarethemostimportantissueswhenthecustomersassessvehiclequality[1].Ontheotherhand,somemanufacturersrefusetocorporateautomationintovehicledesign,asaddressingtheissuesofNVHwhichmakesvehiclestooquietmayposeathreattothesafetyofpedestrians[4].Thevehicularnoisecanactasawarningsignalforpedestrians.
SomecomponentsinthevehiclesplayimportantrolesinreducingNVH,namelyrubberdampers,thepowerplants,chassiscoupling,andelastomericisolators.
Rubberdampersinsertbetweenthefinsandrubberdampersreducetheamplitudeofvibrationoffinswhichareusedtospeeduptheheattransferfromtheenginesurfaces[3].
Invehicles,theenginemountsaffectlargelythenoise,vibration,andharshnesscomfort.Themountsareusedtoprovidesupportsforthepowerplantandtoisolatethevibrationsofthepowerplantfromtherestofthevehicles[6].
Amultiplicityofelastomericisolatorsisneeded,includingenginemounts,suspensionbushings,andframeandsubframemounts[5].Somefunctionalrequirementsforisolatorsinvolvesteering,braking,package,anddurability,althoughthesedesiredcharacteristicsconflictfrequently.
2.TheresearchonNVH
Forvehicles,theissueofvibration,noise,andharshness(NVH)existsmainlyintheengine,carbody,andenginemounts.Duringtheworkingofthesecomponents,theyareaffectedbyaerodynamic(NVH),air-conditioningsystem(NVH)andbrakesystem(NVH).VehicleNVHemphasisthefeelingofhumanbeingsforvibrationandnoiseandcannotbemeasureddirectly.TheresearchonNVHconsistsofthecomfortofpassengersinvehiclesandintensityproblemsofvehicles’componentscausedbyvibration.TheresearchonthecharactersofvehicleNVHshouldconcentrateonentirecarsandseparateentirecarsintosubsystems,suchasenginesystem,enginemountsystemandcarbodysystem.
TheissueofvehicleNVHisnotcausedbyrelativelyseveralreasonsratherthansimplyonereason.Forinstance,thenoiseinthecarmaybeduetothehighlevelofnoiseoftheengine,thepourisolationeffectofsuspensionaroundtheengine,orlimitedtechnologyofsound-proofingbetweenthecarbodyandpowersystem.
TherearesomebasictheoriesandmethodologieshelpingunderstandandstudythecharacterofNVH.
Finiteelementmethodsaretoseparatecontinuouselastomerintothelimitednumberofunitsandcalculatethesystemdeformation,stress,anddynamicscharacterthroughthefiniteelementmodelsonthecomputer.Becauseoftherapiddevelopmentoffiniteelementmethodsandthematurityofrelativeanalysissoftware,FEMhasbecomeanessentialmethodtoanalyzethecharacterofvehicleNVH.FEMissuitableforthemodelinganalysisofvehiclebodystructurevibrationandcarinteriorcavitynoise.Ontheotherhand,combiningFEMwithmulti-systemdynamicstoanalyzeenginemountsystemcanincreasetheaccuracyofdynamiccharacteroftheenginemount.
BEMisshortforthebladeelementmomentum.ComparedwithFEM,BEMdecreasesthedimensionofquestions,makingitconvenienttohandletheissuesofunlimitedfieldandestablishtheefficientnetworkonthecomputer.TheBEMtheoryisgreatlyemployedforpracticalengineeringapplication,especiallyinthefieldofNVH[16].TheshortageofBEMtoaddresstheproblemofNVHislowspeedofcalculation.
Experimentaltransferpathanalysis(TPA)isafairlywellestablishedtechniqueforestimatingandrankingindividuallow-frequencynoiseorvibrationcontributionsviathedifferentstructuraltransmissionpathsfrompoint-coupledpowertrainorwheelsuspensionstothevehiclebody[11].Experimentaltransferpathanalysisisafavoredtechniquetoinvestigatefurtherpossibilitiestofine-tunetherubbercomponentsoftheengineandwheelsuspensionwithrespecttoNVH.
TheexperimentaltransferpathanalysismethodinvolvesanindirectmeasurementprocedureforestimatingoperatingforcecomponentsactingatthecoupledDOFs(degreeoffreedom).TPAalsoinvolvesadirectmeasurementofalltransferfrequencyresponsefunctionsbetweenresponseinpointsofinterestandpointswheretheseforcesact[11].
Designofexperimentsmethod(DOE)canbeusedtominimizethetransmittedengine-inducedharshnesstothebodyandimproveavehiclebodystructure.TheDOEmethodincludesfactorialandresponsesurfacemethods.ThesurfacemodelingisaccomplishedforthevehiclebodywithCATIAandHYPERMESHsoftwarewhichisusedtocreateandoptimizetheFEAmodal.NASTRANsoftwareisusedtoanalyzethemodalinafrequencyrangebetween0-50Hz[17,18].
3.TheeffectofrubberdampersonNVH
Therubberdamperisanimportanttypeofequipmenttoreducenoise,vibration,andharshness(NVH),widelybeingusedinanumberofmachines,vehicles,trainsandaircrafts.Thepopularityofrubberdampersisduetothecharacteristicsofrubberwithhighvisco-elasticityandhighelasticity.Comparedwithsteel,elasticdeformationofrubberislargeandelasticitymodulusofrubberissmall.Aswell,rubberisconsideredasincompressiblematerial.
Thefunctionofrubberdampersbetweenthefinsistomakeacompromisebetweenvibrationamplitudeincreasesandfinbasetemperaturedecreases.Throughtheresearchontheeffectofrubberdampersontheradiatednoisefromengine,itisconcludedthattheeffectoftherubberdampersistoreduceenginehighfrequencynoiselevel,whichmeanstheproblemofvehiclenoisevibrationandharshnesscanbepartlyhandledbyusingtherubberdampers.
Engineerscontinuetoworkontheissuesofhighvehiclenoisevibrationandharshnesswhenanenginedoesnotrubberdamperswithtwomethods.Thesetwoapproachesarerelatedtostructuralnoiseproblems.
Thefirstmethodistofindwaysofreducingthesoundpowerbypassivemeansandtheothermethodistouseactivecontrolapproaches.Comparedwithactivecontrolsolutionswhichmaybesuitableinthefuture,passivecontrolshouldnotbeignoredasitisusefulforhighfrequencynoise[3].
Rubberdampersarenottheonlyequipmentusingrubberinvehiclesandsomerubberconnectionsarewidelyemployedforstructuralparts.Achangeinrubberjointmaterialpropertiescanhelpevaluatethesensitivityofthefull-scalesystemvehiclenoisevibrationandharshness(NVH)[7].Athreelevelmodelingapproachwithamaterial,acomponent,andasystemlevelhasbeenintroducedtoevaluatethesensitivityoftheNVH.
4.powerplantmountingsystemNVH
Thebasicfunctionofenginemountistosupporttheweightofpowertrainandtoisolatethevibrationandharshnesstransmissionfromenginetobody,tosegregatethetransmissionfromroadsurfaceexcitationtopowertrain[8].Aswell,inordertolightenthecarbody,increasepower-intensiveengineandrequirevibration,noise,andharshnessisolationforpassengercars,theperformanceofthepowerplantmountsystemneedtobeimproved.Manyfactors,suchastheenginelayoutstate,thesupportingpositionsofchassismount,thefixedpositionsonthecylinderofthemountandthelayoutofsurroundingparts,shouldbeconsideredbeforethedesignationofenginemount[9].
TheresponsesofthepowerplantmountingsystemtolowfrequencyvibrationsareimportantforimprovingtheNVHintermsofrigidityanddamping.SomedesignsofpowerplantmountingsystemtrytohandletheissuesofNVHbyconcentratingonthepositioninganddesignofresilientsupports.Howevertheyfailtoconsiderchassisandsuspensionsysteminteractionsasthesedesignsarebasedondecouplingrigidbodymodesfromagroundedpowerplantmode.
Fig.1.Powerplantmountingsystem
Thetraditionalenginemountdesignstrategiesconsideronlytherigidbodymodesofagroundedengineandarrangementsofpowerplantrigidbodymode[6].Whenconsideredasarigidbody,threetranslationalmodesandthreerotationalmodesofframerepresentthevibration,noise,andharshness(NVH)ofpowerplantusingdynamicdecouplingmethod.Indetail,threetranslationalmodesarebounce,lateral,andlongitudinalvibrationsandthreerotationalmodesarecalledbyrotationsaboutpitch,rollandyaw.Itisbelievedthatthevibration,noiseandharshness(NVH)transferredtothecarbodystructurecanbereducedbyconditioningthepowerplantmo
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