Wavepropagationanalysisontherailwaytrackwithperiodicallyattachedtunedparticleimpactdampersforrollingnoisereduction

Abstract

Thisstudywascarriedoutthroughthe“Developmentofsustainabletechnologyforrailwaynoiseandvibrationreductiontechnology”projectbytheKoreaRailroadResearchInstitute[1].Withthedevelopmentofhigh-speedtrains,complaintsaboutrailwaynoiseareconstantlybeingraised.Vibrationsandnoisefromoperatingtrainsshouldbereducedtomaintainthequietnessofresidentialareasforminimizingdisturbancetoresidents.Rollingnoiseisanimportantnoisesourcefromoperatingtrains.Itisgeneratedbythevibrationofrailsandwheelsowingtoirregularcorrugationsonthecontactingsurface.Inthisstudy,tunedparticleimpactdamperandananalyticalconsideringclampingforceeffectwereproposed.Themechanismofvibrationalenergydissipationwiththeproposeddamperwasinvestigatedusingexperimentsandrelevantanalyticalmodelling.Thedampingeffectowingtotheexcitationforceandrestitutioncoefficientwasinvestigatedandoptimalvaluesofparticlemassandsystemclearancewereexaminedthroughanalyticalmodeling.Inaddition,clipclampingforceeffectwasalsoconsideredandspectraldampingeffectduetothemagnitudeofclampingforcewascalculatedbytheProny’smethod.Thetunedparticleimpactdamperdissipatedrailvibrationenergymoreeffectivelycomparedwiththetuneddynamicabsorberandenabledvibrationreductioninawiderfrequencyrange.Thevibrationreductionperformancewassignificantlyaffectedbythepartiallyinelasticimpactswiththemainvibratingsystem.Toinvestigatethevibrationdampingduetothetunedparticleimpactdamper,theproposeddamperwasinstalledonanactualrail.Thevibrationdampingfromthetunedparticleimpactdamperwasmoreefficientthantheviscoelasticdampingonly.Theproposedparticleimpactdamperwasexpectedtoreducetherollingnoiseinbroadbandfrequenciesefficiently. Ananalyticalmethodtoinvestigatethewavepropagationcharacteristicsofrailwaysystemwasproposedinthisstudy.Therailwaysystemwasformedwithslabandsleeperrailwaytrack,itwassimulatedwithaninfinitebeamandsupports.Toinducebroadbandvibrationreductionandrollingnoisereduction,two-dimensionaltunedparticleimpactdampersconsideringthetranslationalmotion,rotationalmotionwasproposed.ThefreewavepropagationconstantsandwavenumbersofinfinitedampedtrackwerepredictedwithWFE(wavefiniteelement)method.Thewavepropagationmodelingofslabtrackandsleepertracksystemwassimulatedandwavepropagationconstantofthedampedtracksystemattachingwithtwo-dimensionaltunedparticleimpactdamperswascalculated.Themechanismofvibrationalenergydissipationwiththeproposedmetadamperwasinvestigatedbyfiniteelementmodelingandbyexperimentationina3mlongfreelysupportedrailbeam.Theeffectofinsertedimpactballsonthevariationoftheraildynamicpropertieswasmeasuredbythevibrationtestmethod.Theaveragedfrequency-dependentbendingstiffnessandlossfactorwerecomparedtofindtheeffectsofimpactparticleparameters(mass,diameter,restitutioncoefficientandgeometry).Thus,optimalparametertuningoftheproposedmetadamperforinducinglargetrackdecayratewasavailable.Theproposedmetadampersampleswerefabricatedandattachedtotheexperimentaltrack,thetrackdecayratewasdevelopedinbroadbandfrequencydomainby2.94,1.45dB/minverticalandhorizontaldirection,respectively.Theinfinitedampedtrackmodelwasappliedforrollingnoisepredictionwithmovingloadmethod.Thecriticalspeedoftherailwaytrackwasdecreasedfrom229.4to166.4km/hattachingthetwo-dimensionaltunedparticleimpactmetadampers.Therollingnoisewaspredictedtoreducefrom129.2to123.8dBundertheloadvelocityof250km/h,from81.9to78.3dBunder80km/hloadvelocityconsequently.Throughtheproposedtwo-dimensionaltunedparticleimpactmetadampers,therailwaytrackvibrationandtherollingnoisefromthehigh-speedtraincanbereducedeffectivelywithsmallmassloadingandexpense. Intheresearchproject[1],afieldexperimentaltestwasconductedbyKoreaRailroadResearchInstitute.TheexperimentwascarriedoutonIncheonsubwayline2toverifywhethertherollingnoisereductioneffectoccurswhenthetwo-dimensionaltunedparticleimpactmetadamperreferringthespecificationISO3095:2005.ThetestsectionwastheascendingsectionfromWanggilStationtoGeomdan-OryuStation.AsecondversionofthetunedparticleimpactdamperforKRS50railwaytrackwasmanufacturedandinstalledfor150monthetestsection.TrackdecayratewasalsomeasuredbyreferringthespecificationEN15461:2008.At100~5000Hzwhichisthemainfrequencydomainofrollingnoisegeneration,thevalueofdecayratewasincreasedby3.2and2.2dB/mtooveralllevelinverticalandhorizontaldirectionrespectively.Twomicrophoneswerefixedat1.75and7.5mawayfromthecenterofthetrackcentertomeasurethenear-fieldandfar-fieldrollingnoiserespectively.Therollingnoiseofthenear-fieldmicrophoneduetothedamperfasteningwasreducedby3.3dBA,and4.0dBAatthefar-fieldmicrophone,respectively.Toverifywhethertheindoornoiseoftheoperatingtraintoreduce,thetrainindoornoisemeasurementwasconductedaccordingtothedistanceoftheinstallationintervalofthetunedparticleimpactdampers.ThemeasurementwascarriedoutbyreferringthespecificationISO3381:2005andthesoundqualityfactors(loudnessandroughness)werecompared.3.25dBAindoornoisereductionwasconfirmedtooveralllevel.Inaddition,theloudnessandroughnessofthetrainindoornoisewerereduced4.7soneand0.33asper,respectively.Toaccuratelyanalyzethevibrationalbehavioroftherailwayduetothetrainload,infinitetrackmodelconsideringthewavepropagationcharacteristicsandthepredictionofdynamicpropertiesofrailbeamwererequired.Anon-destructive,high-accuracyraildynamicpropertymeasurementmethodwasdevelopedinthisstudy,andtheequivalentbendingstiffnessandlossfactorofthedampedrailcanbepredictedwiththemeasuredtransferfunctions.Foraccurateprediction,thechangesinthepropertiesoftherailpadaccordingtothecompressiveloadwereconsideredandthedynamicpropertiesoftherailpadwerederived.TosimulatetheequivalentstiffnessofthefasteningsystemconsideringtheSFCdeviceandtherailpadeffect,aclampingsystemmodelingwasproposedandtheequivalentstiffnesswascalculated.Discretelysupportedtrackwasmodeledusingthetransferfunctionmethod,andresponsecharacteristicsaccordingtothedifferentlengthofrailspanwereanalyzed.Whilethelengthofthetrackdecreases,theinfluenceofthereflectionwavegeneratedfromthejointsisdominant,thusthecharacteristicsofthefinitelengthoftracksystemcanbeobserved.Asthelengthofthetrackincreases,theinfluenceofthereflectedwavedeclines,resultinginthedominantwavecharacteristicsbythetravelingwave.Thetransferfunctionswerepredictedbywavepropagationapproachtosimulatethewavepropagationcharacteristicsoftheinfiniterailwaytrack,andvibrationcharacteristicssimilartotheexperimentaltransferfunctionwereconfirmed.TheequivalentpropertiesofrailbeamindiscretelysupportedtrackwerecalculatedforeachfrequencybyusingNewton-Raphsonnumericalmethod.TheequivalentbendingstiffnessandlossfactoroftherailbeamofIncheonSubwayLine2wereconfirmedas4.156MNm2,0.021,respectively,andappearsimilartothespecificationpropertiesoftheKRS50rail.Inaddition,duetothevibrationalattenuationeffect,theequivalentdynamicpropertiesofthedampedrailbeamincreaseeffectivelyto4.780MNm2and0.149,respectively.Therefore,theproposedwavepropagationmethodcanbeusedtomeasuretheequivalentrailpropertiesofdiscretesupporttracksandisexpectedtobeapplicabletoothertypesofrailotherthanKRS50.