机械设计第四章摩擦磨损及润滑概述精.ppt

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1、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 de

2、sign 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

3、 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

4、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 lea

5、st 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

6、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,shearma

7、terial 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 met

8、als 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)

9、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,so

10、thatfluidclosetoAmovewithaspeedV,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、Kenimaticvisc

11、osity(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；Pre

12、ssure：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Oilin

13、ess(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）Itisimportanttoworkinhighorlo

14、wtemperature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）

15、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

16、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（

17、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

18、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)Hydrodynamiclubr

19、ication：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