一种小作用力的磁流变阻尼器

ALowForceMagneto-rheological(MR)FluidDamper:Design,FabricationandCharacterizationGOKHANAYDAR,1CAHITA.EVRENSEL,1,*FARAMARZGORDANINEJAD1ANDALANFUCHS21MechanicalEngineeringDepartmentUniversityofNevada,Reno,Reno,NV,USA2ChemicalEngineeringDepartmentUniversityofNevada,Reno,Reno,NV,USAABSTRACT:Thisstudyfocusesonthetheoreticalanalysis,design,fabricationandcharacterizationofasmallMagneto-Rheological(MR)fluiddamper.Itcanbepotentiallyappliedtoahorizontalaxis,front-loadingwashingmachine.Insuchwashingmachines,althoughwashingcycleisslow,spincycleismuchfaster.Duringaccelerationfromwashingcycletospincycle,thetubpassesthroughitsresonantspeedrequiringrelativelyhighdamping.Ontheotherhand,highdampingresultsinincreasedforcetransmissiontothehousingandnoiseathigh-speedspincycle.ControllabilityoftheMRfluiddamperallowsadjustmentofdampingrequirementsfordifferentcyclesandhelpstoreducethenoiseathighspeedspincyclewhilelimitingthetubmotionatresonance.ApatentedgeometryofanMRvalvedevelopedbyCompositeandIntelligentMaterialsLaboratoryattheUniversityofNevada,Renoisusedasthebasisofthisnewdesigntosatisfytherequirementsoftheapplication.Fabricatedprototypedamperischaracterizedusingharmonicdisplacementinput.Testresultsareingoodagreementwiththetheoreticalpredictionsanddesignvalues.KeyWords:magnetorheological(MR)fluid;controllabledamper;MRdamper;washingmachine.INTRODUCTIONOneofthemajorproblemsassociatedwithhigh-speedfront-loadingwashingmachinesishighlevelsofvibrationandnoise.Thetubofafront-loadingwashingmachineissupportedbyapairofspringsandpairofdampers.Whilethedampershelplimitamplitudeofvibrationsatresonance,theyresultinhigherforcetransmittedtothehousingandincreasednoiseatspincycle.Thegoalofthisstudyistodesign,fabricateandcharacterizeasmallMagneto-RheologicalFluid(MRF)damperthatcanbepotentiallyusedforafrontloadingwashingmachine.Itisdesiredtominimizetheamplitudeofoscillationsatresonancewithoutresultinginrelativelyhighforcetransmittedtothehousingathigh-speedspincycle.MRFaresuspensionsofmicron-sizedintenselypolarizedparticlesinacarrierfluid(SassiandCherif,2005).Theseparticles’diametersareintherangeof1–10mm(Kavlicogluetal.,2002).RecentdevelopmentsledtoMRfluidswithdesirablepropertiessuchaslowviscosity,highyieldstrength,andstablehystereticcharacteristicoverawidetemperaturescale(SassiandCherif,2005).SinceMRFdampersdonotaddenergytothesystembutdissipate,theydonothavethedestabilizingpotentialactivedevicesmayhave.Theirpowerrequirementismuchlowercomparedtoactivedevices.ThisforcecontrollabilityofMRFdampersmakesthemveryattractiveinvibrationisolationapplications(SymansandConstantinou,1997).BetterunderstandingofthecharacteristicsandbenefitsoftheMRFattheendofthe1980’sandbeginningof1990’sresultedingreatlyincreasedinterestinthistechnology(SassiandCherif,2005).ListofdevicesthatutilizeMRfluidsiscontinuallyexpandingandincludevibrationisolators,shockabsorbers,brakes,clutches,etc(Kavlicogluetal.,2002).TherearenumberofearlierworkthatdiscussesMRfluiddamperswithlowforcerangetargetedinthisstudywithdifferentapplications.ForexampleCarlson(1998)introducedanovelapplicationofMRfluidsforwashingmachinevibrationisolationinwhichthefluidisstoredinanabsorbentmatrix.TheseMRspongedevicesuseMRfluidthatisrestrainedbycapillarymovementinanabsorbentmatrixlikeasponge,opencelledfelt,foamorfabric(Carlson,1998;Carlson,1999;Carlson,2000;Carlson,2001;ChrzanandCarlson,2001;SandrinandCarlson,2001;Carlson,2002a).Also,thereareotherpatentedMRFdevicesthatareclaimedtobeapplicabletowashingmachines(Hopkinsetal.,2001;Carlson,2002b,c).DurazzaniandValent(1999)developedamethodforactivedampingofthewashingmachinevibrationusingacontrollableMRfluiddevice.AmorerecentstudybyChoietal.(2005)discussesaconventionalMRdamperanditscontrolforpossibleapplicationinvibrationisolationofavionicpackages.Thisstudyaimsdesign,fabricationandcharacteriza-tionofanMRFdamperwithpossibleapplicationinfront-loadingwashingmachines.Inordertolimitthetubdisplacementnearresonanceandminimizethenoiseathigh-speedspincycle,thedamperitisdesiredtobeactivewiththemaximumdampingforceuptoabout1.4timestheresonanttubrotationalspeed.Itshouldbeinin-activestatewithminimumdampingathigherspeeds.Toachievethis,followingcriteriaareusedforthedesignofthecontrollableMRFdamper:·Maximumactivateddampingforceshouldbeatleast150Natresonance.·Passive(no-current)dampingforceshouldbeaslowaspossible.DESIGNOFTHEMRFDAMPERGeometryThegeometryofthedesignisselectedsothatnonmagneticmaterials,suchasplastics,canbeusedforasmanypartsofthedamperaspossiblewhilesatisfyingtherequiredmagneticfieldstrengthanddistribution.Themotivationbehindthisistominimizethemanufacturingcost.AmodifiedversionofthepatentedgeometryoftheMRvalvedevelopedbytheUniversityofNevada,Renoisusedasthebasisofthisnewdesign(GordaninejadandBreese,2000).Figure1showstheschematicofourdesign.GrayarearepresentsMRfluid.LmisthelengthofMRgapthatisbetweentwoparalleldisks.AlthoughdisktypeMRvalveisveryefficientitresultsinincreasedoff-statepressuredropduetothisspecificgeometryandsharpturns,especiallyathighspeeds.Asitmaybeapparentfromthescal