OriginalArticle
Developmentofamagnetorheological
brakewithaslotteddisc
1andHarishHirani2 ProcIMechEPartD: JAutomobileEngineering 2015,Vol.229(14)1907–1924 óIMechE2015 Reprintsandpermissions: sagepub.co.uk/journalsPermissions.nav DOI:10.1177/0954407015574204 pid.sagepub.com ChiranjitSarkar
Abstract
Aconventionaldiscwearsoutandthebrakepollutestheenvironment.Brakepaddustisreportedtobethelargest 1.Theparticlesemanatingbecauseofwearofthebrakepadpollutetheenviron- sourceofenvironmentpollution 2,3,4.Inadditiontopollutioncausedbywearparticles,thefriction-inducednoisebetweenthebrakepadandthe ment 5.Also,localizedheatingoccursinaconventionaldiscbrake.Totacklebothoftheseprob- discisalsoamajorconcern lems,conventionaldiscbrakescanbereplacedwithmanetorheologicalfluidbrakes.Magnetorheologicalfluidsaremate- rialshavingashearyieldstresswhichisafunctionofthemagneticfield.Ontheapplicationofamagneticfield,
magnetorheologicalparticlesbecomealignedandincreasetheshearresistancebetweenrelativelymovingsurfaces.The frictionbetweenthestatorandtherotorincreasesandfulfilsthebrakingfunction,whichmeansthatmagnetorheological fluidscanbeusedasbrakefrictionmaterials.Amagnetorheologicalbrakeconsistsofarotatingdiscordiscsimmersed inamagnetorheologicalfluidandenclosedinanelectromagneticcasing.Thetorquecharacteristicsofthemagnetorheo- logicalbrakeintheshearmodearecontrolledbyregulatingtheyieldstressofthemagnetorheologicalfluid.Anincrease intheyieldstressincreasesthebrakingtorque,whichmeansthat,thehighertheyieldstrengthofthemagnetorheologi- calfluid,thebetteristheperformanceofthemagnetorheologicalbrake.However,themajordisadvantageoftheshear- mode-basedmagnetorheologicalbrakeisitshighresistingtorqueevenintheoff-stateviscosity,andsuchmagnetorheo- logicalbrakescannotberecommendedforautomotiveapplications.Toobtaintheperformanceofaconventionaldisc brake,experimentalstudiesonaconventionaldiscbrakewereperformedusingafull-scaledynamometer.Inadditionto wearparticles,localizedheatingofthediscwasobserved.Thedisc–padinterfacesweremodelledtosimulatethedisc temperature.Thevaluesofthemaximumtemperature,whichwereobtainedfromsimulationsaswellasexperiments, werecompared.Thesimulationswereextendedtohypothetical360°pads,andasignificantreductioninthemaximum temperaturewasnoted.Basedontheideaof360°pads,amagnetorheologicalbrakesubjectedtoshearingwasanalysed. Toperformexperimentsonasmall-scalemagnetorheologicalbrake,atestset-upwasdesignedanddeveloped,andit wasconfirmedthatamagnetorheologicalbrakesubjectedtoshearingprovidesabettertorquethandoesaconventional discbrakeofthesamesize.Anidealmagnetorheologicalbrakeshouldexertazerofrictionaltorqueintheoff-statecon- ditionandacontrollablefrictionaltorqueintheon-statecondition.Anattemptwasmadetodesignsuchamagnetor- heologicalbrake.Toovercomethedisadvantageoftheshear-mode-basedmagnetorheologicalbrake,anewdesignof magnetorheologicalbrakewithaslotteddiscwasproposed.Thedesignanddevelopmentoftheproposedmagnetorheo- logicalbrake,incorporatingthecompression-assistedshearmode,wasdetailed.Theresultsofthebrakingtorque,the temperaturedistributionandtheoff-stateviscositieswereplotted.Finally,comparisonbetweentheproposedmagnetor- heologicalbrakeandasmall-scalediscbrakewaspresented.Theresultsshowthat,withanincreaseinthebrakingpres- sure(from2barto6bar),themaximumvalueoftemperaturerisesbecauseofenhancementofthelocalizedheatingin thedisc.Thetemperatureriseislessinthecaseoftheextendedbrakepad(360°),whichwasusedinthemagnetorheo- logicalbrake.Thesurfacetemperatureofthemagnetorheologicalbrakeincreaseswithincreasingmagneticfield.The magnetorheologicalfluidwith50wt%ironparticleshasalessviscoustorqueintheoff-stateconditionandahigh-field torqueunderthecompressionmechanisminthemagnetorheologicalbrake,whichfulfilsthecriterionforanidealmag- netorheologicalbraketoreplaceaconventionaldiscbrakeofthesamesize.
1DepartmentofMechanicalEngineering,DelhiTechnologicalUniversity,
Delhi,India
2DepartmentofMechanicalEngineering,IndianInstituteofTechnology
Delhi,Delhi,India
Correspondingauthor:
ChiranjitSarkar,DepartmentofMechanicalEngineering,Delhi
TechnologicalUniversity,Delhi110042,India.
Email:chiranjit.ju@gmail.com
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