（机械工程专业毕业论文）基于长下坡工况树脂基制动材料摩擦学性能研究.docx

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1、基于长下坡工况树脂基制动材料摩擦学性能研究基于长下坡工况树脂基制动材料摩擦学性能研究摘要当汽车在长下坡工况进行制动时，其制动系统的工作环境会变的更加恶劣，制动性能会因此下降，甚至失效而引发安全事故。目前国内外基于该特殊工况的研究主要集中在建立数学模型以及计算机模拟仿真等方面，因此有必要从惯性模拟实验平台对该工况下制动材料的摩擦磨损性能及机理进行深入研究。本文选取了课题组制备的一种CaSO4晶须增强新型树脂基制动材料和一种市售刹车片材料为研究对象。基于长下坡工况，分别在CHASE和MM-10001I型摩擦试验机上研究摩擦时间、制动频率以及制动压力对两种制动材料摩擦学性能的影响，从而总结出长下坡工

2、况下树脂基制动材料摩擦磨损性能的变化规律，并分析摩擦磨损机理及影响其摩擦学性能的关键因素。实验结果表明：随着摩擦时间的增加，制动材料摩擦表面温度呈现出“急剧升温一温度稳定一缓慢升温”的变化过程，出现热衰退现象，摩擦系数下降并出现明显波动，制动平稳性变差并伴有制动噪声和振颤，磨损率上升；而随着制动频率的增大，由于制动材料摩擦表面进行了充分的热交换，温度上升幅度较小，摩擦系数变化平稳，制动可靠，但由于摩擦表面承受着热循环冲击应力以及界面摩擦剪切阻力的双重作用，易在其表面或亚表层形成微裂纹，而造成疲劳磨损。制动材料的摩擦学性能的变化对制动速度的敏感性大于制动初始温度，制动速度越大，摩擦系数的波动性越

3、大，而且摩擦表面温度也越高。制动压力与制动时间呈线性递减关系，而与制动材料的摩擦吸收功率呈线性递增关系。制动压力越大,摩擦力矩曲线抖动现象越严重，制动平稳性越差，但在一定范围内，制动压力的增大有利于摩擦表面形成摩擦膜，从而降低磨损率。长下坡工况下不同制动条件对树脂基制动材料摩擦学性能的影响主要体现在摩擦表面的温升情况及其受力状态。在制动过程中，由于摩擦生热使大量热量聚集在摩擦表面而引起温升，当温度超过一定范围，将引起基体树脂软化、粘流以及热分解，与对偶件的粘着效应增强，金属组分发生氧化反应，同时在界面冲击应力以及摩擦剪切阻力的作用下，磨损表面形貌特征将发生变化，部分材料发生脱落并在材料缺陷处或

4、应力集中处形成裂纹源，从而影响体系中各组元间的结构和性能以及相互之间的协同作用，引起制动材料摩擦磨损性能发生变化，造成制动性能下降。关键词：长下坡工况，制动频率，树脂基制动材料，摩擦磨损，CaSO4晶须ResearchontheTribo1ogica1PerformanceofResin-basedBrakeMateria1sBasedon1ongDownhi11conditionAbstractWhentheautomobi1eapp1ythebrakeduringthe1ongdownhi11condition,theworkingsituationofitsbrakesystemwi11

5、becomemoresevere,asaconsequence,thebrakeperformancewi11dec1ine,orevenfai1ureandthencausesafetyaccidents.Whi1etheresearchstatusbothathomeandabroadfocusonestab1ishingmathematica1mode1andconductingcomputersimu1ation,soitisnecessarytomakeanintensivestudyonthefrictionandwearpropertiesandmechanismofbrakem

6、ateria1sunderthe1ongdownhi11conditionbyinertiasimu1ationexperimentp1atform.Inthispaper,asortofCaSc)4whiskersreinforcedresin-basedcompositefrictionmateria1swhichweredeve1opedbyourownresearchteamandakindofcommercia11yavai1ab1ebrakemateria1werese1ectedastheresearchobjects.Basedonthe1ongdownhi11conditio

7、ns,theeffectoffrictiontime,brakingfrequencyandbrakingpressureontribo1ogica1propertiesoftwokindsofbrakemateria1sweretestedonCHASEandMM-IOOOIIfrictiontester,respective1y.Withthepurposetosummarizethechangeru1esoffrictionandwearpropertiesofresin-basedbrakemateria1sunderthe1ongdownhi11workingconditions,a

8、ndthenana1ysisthefrictionandwearmechanismsandthekeyinf1uencefactorstoitstribo1ogica1properties.Theexperimenta1resu1tsshowthatthefrictionsurfacetemperatureofbrakemateria1sshowedthechangeprocessfromsharpheatingtotemperaturestabi1itytos1owheatingwiththeincreasingoffrictiontime,andthenappearedtheheatfad

9、ingphenomenon,asaresu1t,thefrictioncoefficientdecreasedandf1uctuatedobvious1y,andthebrakingstabi1itybecameworseaswe11aswiththebrakenoiseandvibration,andthewearrateincreased;Whi1e,withtheincreasingofbrakingfrequency,theriseoffrictionsurfacetemperatureofbrakemateria1swassma11erforthefrictionhaveprocee

10、dedthesufficientheatexchange,therefore,thefrictioncoefficientchangedsmooth1yandshowedthere1iab1ebraking.However,itwaseasytoformthemicrocracksonthesurfaceorsubsurfaceduetothedua1actionoftherma1cyc1eimpactstressandinterfacia1frictiona1shearresistance,andthencausedfatiguewear.Thefrictionandwearproperti

11、esofbrakemateria1sshowedmoresensitivetobrakingve1ocitythaninitia1brakingtemperature,sothef1uctuationoffrictioncoefficientwasextendedwiththeincreasingofbrakingve1ocity,besides,thesurfacefrictiontemperatureraisedtoo.Furthermore,thebrakingtimeshowedadiminishing1inearre1ationshipwithbrakingpressure,whi1

12、ethefrictionpowerabsorptionofbrakemateria1sshowedanincreasing1inearre1ationshipwithit.Thegreaterthebrakingpressure,themoreseriousthefrictiontorquecurveofditheringphenomenon,andtheworsethebrakingstabi1itywou1dbecome,neverthe1ess,theincreaseofbrakingpressurewasbeneficia1totheformationoffrictionfi1mont

13、hefrictionsurfaceinacertainrange,soastoreducethewearrate.Theeffectofdifferentbrakingconditionsonthetribo1ogica1propertiesofresin-basedfrictionmateria1sunderthe1ongdownhi11workingconditionsaremain1yref1ectedinthetemperatureriseandstressstateoffrictionsurface.Duringthebrakingprocess,thefrictionsurface

14、temperaturewi11riseforthefrictionheatgenerating1argeamountsofheatandaccumu1ateonit,whenthetemperatureexceedsacertainrange,itwi11causethematrixsoftening,viscousf1owandtherma1decomposition,andtheadhesioneffectwiththedua1discwi11reinforced,besides,themeta1componentsinmateria1systemwi11occuroxidationrea

15、ctiontoo.Inaddition,withtheactionofinterfaceimpactstressandfrictionshearresistance,thewearsurfacemorpho1ogycharacteristicswi11changed,andpartofthemateria1swi11fa11offandatthemateria1defectsorstressconcentrationpointswi11formthecracksources,thusaffectingthestructureandpropertiesofeache1ementinmateria

16、1systemandweakenitssynergisticeffectbetweeneachother,asaresu1t,a11ofthosewi11changethefrictionandwearpropertiesofbrakemateria1sanddec1inebrakeperformance.Keywords:1ongdownhi11condition,Brakingfrequency,Resin-basedbrakemateria1,Frictionandwear,CaSO4whiskers摘要IAbstractII第一章绪论11.1 课题研究背景及意义11.2 汽车制动材料研究现状11.2.1 汽车制动材料主要类型11.2.2 新型树脂基制动材料研究现状21.3 晶须对复合材料的增强机理41.4 工况条件对制动材料摩擦学性能的影响61.4.1 制动摩擦时间对摩擦学性能的影响61.4.2 速度对摩擦学性能的影响61.4.3 载荷对摩擦