机械设计第四章摩擦磨损及润滑概述精.ppt
机械设计第四章摩擦磨损及润滑概述第1页，本讲稿共25页Lubrication（润滑）（润滑）The condition of having been made smooth or slippery by the applicat-ion of a lubricant such as oil or grease(脂)Tribology（摩擦学）（摩擦学）The branch of engineeri-ng that deals with the interaction of surfaces in relative motion(as in bearings or gears):their design and friction and wear and lubrication第2页，本讲稿共25页IIFriction(摩擦摩擦)1.ClassificationClassifiedbywhethertwopartshaverelativemovementStaticalfriction(静摩擦静摩擦)friction between two or more solid objects that are not moving relative to each other；Kineticfriction(动摩擦动摩擦)occurs when two objec-ts are moving relative to each other and rub together(like a sled(雪橇)on the ground).第3页，本讲稿共25页Classifiedbymovementtype（important）Slidingfriction（滑动摩擦）（滑动摩擦）occurswhen two objects slide across from one another；Rollingfriction(滚动摩擦滚动摩擦)occurs when a body(such as a ball,tire,or wheel)rolls on a surface.第4页，本讲稿共25页Classifiedbylubricant（important）Dryfriction(干摩擦干摩擦)resists relative lateral motion of two solid surfaces in contactFluidfriction（流体摩擦）（流体摩擦）the friction between layers within a viscous fluid that are moving relative to each other；第5页，本讲稿共25页Boundaryfriction（边界摩擦）（边界摩擦）occurs when a surface is at least partially wet,but not so lub-ricated that there is no direct friction between two surfaces;Mixedfriction（混合摩擦）（混合摩擦）a kind of friction including both boundary friction and fluid fric-tion.第6页，本讲稿共25页IIIWear(磨损磨损)Threestagesofwear*run-inwear(磨合磨损磨合磨损)（useful）Stablewear(稳定磨损稳定磨损)（work）Severewear(剧烈磨损剧烈磨损)（failure）Wear rate：=q t q Wear magnitudeDesignoruseamachine,youshoulddoyourbesttoreducerun-intime,increasestableweartimeandpostponethearrivalofseverewear.第7页，本讲稿共25页1.Adhesive wear(粘着磨损粘着磨损)3.Fatigue wear(疲劳疲劳磨损磨损)Pressurelocal temperature increasesadhesion(weld)Friction forceavulsion,shearmaterial transfer Fluctuating stressescrack propagatio-nsurface delamination(表面剥落)pit（pitting corrosion,疲劳点蚀）2.Abrasive wear(磨料磨料磨损磨损)Surface material drops off,oil contains impurity(杂质),rigid grains become abrasive grains(磨料)4.Corrosion wear(腐蚀磨损腐蚀磨损)5.Erosion(冲蚀磨损冲蚀磨损)A state of deterioration in metals caused by oxidation or chemical actionErosion caused by gas and fluid第8页，本讲稿共25页IVLubrication（润滑）（润滑）Decreasefriction,reducewear；Preventpartsfromrust；Heatoutputandtemperaturereduction（circulationoil,循环油）；循环油）；Cushionandabsorbshock(缓冲吸振缓冲吸振)；Seal（Greaselubricant）1.EffectsofLubrication(润滑的作用润滑的作用)第9页，本讲稿共25页2、Lubricantanditsindex（润滑剂及主要指标（润滑剂及主要指标)（1）Lubricatingoil（润滑油）（润滑油）Animaloil,vegetableoil,MineraloilandchemicalsynthesisoilViscosity（粘度）（粘度）Resistance of a liquid to shear forces(and hence to flow)第10页，本讲稿共25页Newtonianfluidfrictionlaw(牛顿流体摩擦定律牛顿流体摩擦定律)：AmovewithaspeedV，andBisholdstill,sothatfluidclosetoAmovewithaspeedV,andfluidclosetoBplateisstatic.Themovementofthefluidislaminarflow,thereexistrelativeslipbetweenarbitrarytwolayers,shearstressesexistattheinterfaceoflaminarflow,i.e.,第11页，本讲稿共25页A.Kineticviscosity（动力粘度）（动力粘度）Unit：Pas（ISO），），Ns/m2（C.G.S,厘米厘米-克克-秒秒制单位）制单位）B、Kenimaticviscosity(运动粘度运动粘度)Unit：m2/s Fluid densityC、Specificviscosity(条件粘度条件粘度)EUnit：Englerdegree(恩氏度恩氏度,Et）Oilnumber(Table4-1):AccordingtoGB/T314-1994,oilnumberisthecentralvalueofkenimaticviscosityat40C第12页，本讲稿共25页Influencingfactorofviscosity(影响粘度的因素影响粘度的因素)Temperature：high temperature causes low viscosity；Pressure：Viscosity increases with increasing press-ure.When pressure is lower than 20MPa,its effects can be ignored.When pressure exceeds 20MPa,they must be considered.pViscosity under pressure p，Pas；0Viscosity under pressure 105Pa，Pas；Pressure viscosity coefficient(粘压系数)，（13）10-8 m2N。第13页，本讲稿共25页Oiliness(油性油性)Physicalorchemicalabsorptionfilm(吸附膜吸附膜)decreasefrictionandwearExtremepressureproperty(极压性极压性)Createwear-resisting,highpressureresisti-ngchemicalboundaryfilmOxidationresistance(氧化稳定性氧化稳定性)TheabilitytoresistoxidationFlashpoint（闪点）（闪点）andSolidifyingPoint（凝固（凝固点）点）Itisimportanttoworkinhighorlowtemperature第14页，本讲稿共25页（2）Lubricantgrease（润滑脂）（润滑脂）Calciumbase(钙基钙基)grease,Sodium(钠基钠基)basegrease，lithiumbase(锂基锂基)grease,aluminumbase(铝基铝基)greasePenetration(针入度针入度)LowerpenetrationincreasesbearingcapacityDroppingpoint(滴点滴点)Measurethehighthermalresistanceofthegrease第15页，本讲稿共25页（3）Additive（添加剂）（添加剂）EffectsoftheadditiveImproveoiliness,extremepressurepropertyandworkabilityunderextremeoperatingconditions；Deferageingandprolongservicelife；ImprovephysicalpropertyTypicaladditive：detergentdispersant(清净分清净分散剂散剂),antioxidant(抗氧化剂抗氧化剂),oilinessadditive(油性添加剂油性添加剂),extreme-pressureandantiwearadditive(极压与抗磨添加剂极压与抗磨添加剂),pourinhibitor(降凝剂降凝剂),tackifier(增粘剂增粘剂)第16页，本讲稿共25页Lubricating methods(oil and grease lubrication）1.Oil lubrication(油润滑油润滑)Force filling oil cup(压注油杯）Oil pot with turning sleeve（旋套油杯）第17页，本讲稿共25页（1）Drip feed lubrication(滴油润滑)Oil pot with needle valve(针阀油杯)Wick oiler(油芯注油器)第18页，本讲稿共25页（2）Oil-ring lubrication (油环润滑)（3）Splash lubrication(飞溅润滑)（4）Pressure circulation (压力循环润滑)第19页，本讲稿共25页 2.Grease lubrication (脂润滑脂润滑)Grease cup with turning sleeve(旋盖式油脂杯)Grease gun(油脂枪)第20页，本讲稿共25页44Hydrodynamicandhydrostaticlubrication(液体动力润滑和流体静力润滑液体动力润滑和流体静力润滑)I.Newtonianlawoffriction(viscosity)牛顿流体摩擦的摩牛顿流体摩擦的摩擦定律（粘性定率）擦定律（粘性定率）Tangentialstressesinanypointoffluidaredirectlypro-portionaltolocalvelocitygradientProportionalitycoefficients(比例系数比例系数)Kinetic viscosity of the fluid Shear resistance per unit area(单位面积的剪切阻力单位面积的剪切阻力):第21页，本讲稿共25页II.Hydrodynamiclubrication(流体动力润滑流体动力润滑)Hydrodynamiclubrication：Frictionsurfacesoftworelativemotionbodyaredividedbyoilfilmcausedbyrelativespeed,andtheexternalloadsarebalancedbytheoilfilmpressure.第22页，本讲稿共25页 Wedge-shaped carrying mechanism (楔效应承载机楔效应承载机理理)ParallelplaterelativemotionFlowvelocityislinearnopressureinoilNon-parallelplaterelativemotionFlowvelocitychangeswithpositionproducepressureinoil第23页，本讲稿共25页流体静力润滑：流体静力润滑：从外部加压的油送入摩擦面间，强迫形成承载油膜的润滑第24页，本讲稿共25页1.(1);2.(2);3.(4);4.(1);5.(2);6.(4);7.(4);8.(2);9.(1)第25页，本讲稿共25页
