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CFSMA,Guangzhou,ChinaMarch15–182005DonaldE.YuhasPh.DIndustrialMeasurementSystems,Inc.2760BeverlyDrive#4AuroraIL60504USADyuhas@imsysinc.comNVHIssuesinAutomotiveBrakesNVH(Noise,Vibration,&Harshness)DefinitionoftheProblemOverviewofBrakeNoiseModeling&SimulationStrategySurveyofMeasurementMethodsElasticPropertyMeasurementsCFSMA,Guangzhou,ChinaMarch15–182005NVHIssuesinAutomotiveBrakesNVH(Noise,Vibration,&Harshness)Rationale:NVHhasbeenacostlywarrantyproblemintheautomotiveindustryfordecades.NVHMorethan$100millionisspentannuallyonbrakeNVHwarrantyworkinNorthAmericaalone.NVH1.NVHIssuesinAutomotiveBrakesNVH(DefinitionoftheProblem)WarrantyCosts:•Replacementofdefectivecomponents••Lostproductivityduetorework••Diminishedcustomerconfidence•NVHIssuesinAutomotiveBrakesNVH(DefinitionoftheProblem)HISTORY:ThefirstbrakesquealonrecordwasfromaSumerianquarrycart,3,500yearsago3500SumerianModernEra:1908HerbertFroodpatentsfirstasbestosbrakelinings1908HerbertFrood1938Noise(squeal)identifiedasaproblem19381980’sNVHissuesassociatedwiththeformulationofnon-asbestosorganic(NAO)padsleadstonewmeasurement&analysismethods1980’sNVH1990’sLumpedparameterModels;IndividualComponentSimulationModels;Non-contactMeasurements;AutomatedDataAcquisition1990’s2000’sLargeSystemsSimulations;ImproveFrictionMaterialCharacterization;Non-linearBehavior2000’sNVHIssuesinAutomotiveBrakesNVH(DefinitionoftheProblem)FrequencyRangeforNVHNVHNVHIssuesinAutomotiveBrakesNVH(OverviewofBrakeNoise)VeryLowFrequencyVibrationsBrakeRoughnessisthevehiclevibration,jerkiness,orpulsations.AlsocalledJudderorShudder•Duringabrakingstop•Sensedasashakeornibblethroughsteeringwheel,floorboards,dashpanel,carseat,orbrakepedal•Createdbyrepetitivevariationintorqueoutputfromthebrake•Typicallyinthe5-60hzrange5-60hz•Frequencyvarieswithwheelspeed•Generally1to2pulsationsperrevolutionbutcanreachupto101-210NVHIssuesinAutomotiveBrakesNVH(OverviewofBrakeNoise)Roughness5-60HzDTVGroanisalowfrequencynoisethatismoredistinctlyheardinsidethevehiclethanoutsidethevehicle:Emanatesfrombodystructureinresponsetovibrations/pulsationscreatedinbrakeFrequencytypicallyinrangeof30-600Hz30-600HzFrequencycontentusuallycontrolledbyresonancemodesinbodyandsuspensionsystemcomponentsFrequencysometimesdrivenbyhigherorderofwheelrotationalspeedNVHIssuesinAutomotiveBrakesNVH(OverviewofBrakeNoise)GroanPotentialContributorstoGroanRotorDeformations-vane/channelsurfaceripples,grind/swirlsurfacefinishpatterns-PadthermaldeformationPadloadpatternFrictionfilmonrotor,FrictionvariationµPadphysicalpropertyvalues,shearandcompressionFrictioncoefficientversusspeed,static/dynamicCaliperstiffnessBushingstiffnessNVHIssuesinAutomotiveBrakesNVH(OverviewofBrakeNoise)GroanBrakeSquealBrakesquealisaphenomenonofdynamicinstabilitythatoccursatoneormoreofthenaturalfrequenciesofthebrakesystem.•Theexcitationcomesfromthefrictioncouple.•Thediscrotorisactinglikea“speaker”(soundwaveradiatedfromtherotorsurfaces).•Padsandrotorcouplinghasmajorimpactonmidtohighfrequency(4~16kHz)squeal.4-16khz•Lowfrequency(1~3kHz)squealtypicallyinvolvescaliper,anchorbracket,knuckleandsuspension,inadditiontopadsandrotor.1-3khzNVHIssuesinAutomotiveBrakesNVH(OverviewofBrakeNoise)SquealFactorsInfluencingLowFrequencyBrakeNoiseNVHIssuesinAutomotiveBrakesNVH(OverviewofBrakeNoise)Stiffness/massLowFrequencyBrakeNoiseThicknessPadSuspensionKnuckleCaliperRotorVanePatternHatSectionMaterialBridgeAnchorBracketClipsBridgeStiffness/massDampingFrictionMaterialGeometryInsulatorFactorsInfluencingHighFrequencyBrakeNoiseNVHIssuesinAutomotiveBrakesNVH(OverviewofBrakeNoise)HighFrequencySquealThicknessRotorVanePatternHatSectionMaterialCaliperAnchorBracketPadFrictionMaterialGeometryInsulatorNVHIssuesinAutomotiveBrakesNVH(Modeling&SimulationExample)3to60DOF3-60300,000DOF300000{l2[M]+l[C]+[K]}(F)=0Equationofmotion:NVHIssuesinAutomotiveBrakesNVH(Modeling&SimulationExample)BrakeSquealModels:Complexmodesanalysis(frequencydomain)IncorporatessophisticatedcontactsurfaceanalysisAccommodatesrealisticfrictionlawsComputationallytractableCommercialcodesavailableOnlyaccurateforsteadystatesliding(timedependentmaterialpropertiescannotbetreated)Transientanalysis(Timedomain)More“real-world”treatmentforproblemHandlesmovingloadsbetterMoreflexiblewithcontactproblemsandfrictionmodelsTimedependentmaterialpropertiesComputationallyintenseslowturnaroundfordesigniterationsNVHIssuesinAutomotiveBrakesNVH(Modeling&SimulationExample)Correlationofdrivingpointfrequencyresponseofrotoratfree-freeboundaryconditions1.E-021.E-011.E+001.E+011.E+021.E+031.E+041.E+051.E+06012345678910111213141516Frequency(Khz)Accelerant(mm/s^2*N)FEAEXPTakenfromKunget..al.2003PredictivenatureofFEAforcomplexgeometryrotorNVHIssuesinAutomotiveBrakes(Modeling&SimulationExample)FrictioninducedmodecoalesceascalculatedbyFEA19401950196000.10.20.30.40.50.6FrictionCoefficientFrequency(Hz)TakenfromKunget..al.2003NVHIssuesinAutomotiveBrakes(Modeling&SimulationExample)CurrentFEAmodelscanincludeNegativeµ-velocityrelationFEAµAssesstheroleofstick-sliponfrictioninducedvibrationsStickSlipIft