DevelopmentofamagnetorheologicalbrakewithaslotteddiscChiran激tSarkar1andHarishHirani2AbstractAconventionaldiscwearsoutandthebrakepollutestheenvironmerit.BrakepaddustisreportedtobethelargestsourceofenvironmentpollutionThePsemanatingbecauseofwearofthebrakepadpollutetheenviron-men^,3,4・"additiontopollutioncausedbywearps,thefriction-inducednoisebetweenthebrakepadandthediscisalsoamajorcone备r/^so,localizedheatingoccursinaconventidiscbrake.Totacklebothoftheseproblems,conventionaldiscbrakescanbereplacedwithmanetorheologicalfluidbrakes.Magnetorheologicalfluidsarematerialshavingashearyieldstresswhichisafunctionofthemagneticfield.Ontheapplicationofamagneticfield,magnetorheologicalpsbecomealignedandincreasetheshearresistaneebetweenrelativelymovingsurfaces.Thefrictionbetweenthestatorandtherotorincreasesandfulfilsthebrakingfunction,whichmeansthatmagnetorheologicalfluidscanbeusedasbrakefrictionmaterials.Amagnetorheologicalbrakeconsistsofarotatingdiscordiscsimmersedinamagnetorheologicalfluidandenclosedinanelectromagneticcasing.Thetorquecharacteristicsofthemagnetorheologicalbrakeintheshearmodearecontrolledbyregulatingtheyieldstressofthemagnetorheologicalfluid.Anincreaseintheyieldstressincreasesthebrakingtorque,whichmeansthat,thehighertheyieldstrengthofthemagnetorheologicalfluid,thebetteristheperformanceofthemagnetorheologicalbrake.However,themajordisadvantageoftheshear-mode-basedmagnetorheologicalbrakeisitshighresistingtorqueevenintheoff-stateviscosity,andsuchmagnetorheologicalbrakescannotberecommendedforautomotiveapplications.Toobtaintheperformaneeofaconventionaldiscbrake,experimentalstudiesonaconventionaldiscbrakewereperformedusingafull-scaledynamometer.Inadditiontowearps,localizedheatingofthediscwasobserved・Thedisc-padinterfacesweremodelledtosimulatethedisctemperature.Thevaluesofthemaximumtemperature,whichwereobtainedfromsimulationsaswellasexperiments,werecompared・Thesimulationswereextendedtohypothetical360°pads,andasignificantreductioninthemaximumtemperaturewasnoted.Basedontheideaof360°pads,amagnetorheologicalbrakesubjectedtoshearingwasanalysed・TDperformexperimentsonasmall-scalemagnetorheologicalbrake,atestset-upwasdesignedanddeveloped,anditwasconfirmedthatamagnetorheologicalbrakesubjectedtoshearingprovidesabettertorquethandoesaconventionaldiscbrakeofthesamesize・Anidealmagnetorheologicalbrakeshouldexertazerofrictionaltorqueintheoff-statecornditionandacontrollablefrictionaltorqueintheon-statecondition.Anattemptwasmadetodesignsuchamagnetorheologicalbrake・Ioovercomethedisadvantageoftheshear-mode-basedmagnetorheologicalbrake,anewdesignofmagnetorheologicalbrakewithaslotteddiscwasproposed・Thedesignanddevelopmentoftheproposedmagnetorheologicalbrake,incorporatingthecompression-assistedshearmode,wasdetailed.Theresultsofthebrakingtorque,thetemperaturedistributionandtheoff-stateviscositieswereplotted.Finally,comparisonbetweentheproposedmagnetor-heologicalbrakeandasmall-scalediscbrakewaspresented.Theresultsshowthat,withanincreaseinthebrakingpressure(from2barto6bar),themaximumvalueoftemperaturerisesbecauseofenhancementofthelocalizedheatinginthedisc.Thetemperatureriseislessinthecaseoftheextendedbrakepad(360°),whichwasusedinthemagnetorheo-logicalbrake.Thesurfacetemperatureofthemagnetorheologicalbrakeincreaseswithincreasingmagneticfield.Themagnetorheologicalfluidwith50wt%ironpshasalessvi...