机械设计第四章摩擦磨损及润滑概述

机械设计第四章摩擦磨损及润滑概述第1页，课件共25页，创作于2023年2月Lubrication（润滑）——Theconditionofhavingbeenmadesmoothorslipperybytheapplicat-ionofalubricantsuchasoilorgrease(脂)Tribology（摩擦学）——Thebranchofengineeri-ngthatdealswiththeinteractionofsurfacesinrelativemotion(asinbearingsorgears):theirdesignandfrictionandwearandlubrication第2页，课件共25页，创作于2023年2月IIFriction(摩擦)1.Classification①

ClassifiedbywhethertwopartshaverelativemovementStaticalfriction(静摩擦)——frictionbetweentwoormoresolidobjectsthatarenotmovingrelativetoeachother；Kineticfriction(动摩擦)——occurswhentwoobjec-tsaremovingrelativetoeachotherandrubtogether(likeasled(雪橇)ontheground).第3页，课件共25页，创作于2023年2月②

Classifiedbymovementtype（important）Slidingfriction（滑动摩擦）——occurs

whentwoobjectsslideacrossfromoneanother；Rollingfriction(滚动摩擦)——occurswhenabody(suchasaball,tire,orwheel)rollsonasurface.第4页，课件共25页，创作于2023年2月③

Classifiedbylubricant（important）Dryfriction

(干摩擦)——resistsrelativelateralmotionoftwosolidsurfacesincontactFluidfriction（流体摩擦）——thefrictionbetweenlayerswithinaviscousfluidthataremovingrelativetoeachother；

第5页，课件共25页，创作于2023年2月Boundaryfriction（边界摩擦）——occurswhenasurfaceisatleastpartiallywet,butnotsolub-ricatedthatthereisnodirectfrictionbetweentwosurfaces;Mixedfriction（混合摩擦）——akindoffrictionincludingbothboundaryfrictionandfluidfric-tion.第6页，课件共25页，创作于2023年2月III

Wear(磨损)Threestagesofwear

*run-inwear(磨合磨损)（useful）Stablewear(稳定磨损)（work）Severewear(剧烈磨损)（failure）Wearrateε：ε=△q／△t△q——WearmagnitudeDesignoruseamachine,youshoulddoyourbesttoreducerun-intime,increasestableweartimeandpostponethearrivalofseverewear.第7页，课件共25页，创作于2023年2月1.Adhesivewear(粘着磨损)3.Fatiguewear(疲劳磨损)Pressure—localtemperatureincreases—adhesion(weld)

Frictionforce—avulsion,shear—materialtransferFluctuatingstresses—crackpropagatio-n—surfacedelamination(表面剥落)—pit（pittingcorrosion,疲劳点蚀）2.Abrasivewear(磨料磨损)Surfacematerialdropsoff,oilcontainsimpurity(杂质),rigidgrainsbecomeabrasivegrains(磨料)4.Corrosionwear(腐蚀磨损)5.Erosion(冲蚀磨损)AstateofdeteriorationinmetalscausedbyoxidationorchemicalactionErosioncausedbygasandfluid第8页，课件共25页，创作于2023年2月IVLubrication（润滑）Decreasefriction,reducewear；Preventpartsfromrust；Heatoutputandtemperaturereduction（circulationoil,循环油）；Cushionandabsorbshock(缓冲吸振)；Seal（Greaselubricant）1.EffectsofLubrication(润滑的作用)第9页，课件共25页，创作于2023年2月2、Lubricantanditsindex（润滑剂及主要指标)（1）

Lubricatingoil（润滑油）

Animaloil,vegetableoil,Mineraloilandchemicalsynthesisoil①

Viscosity（粘度）Resistanceofaliquidtoshearforces(andhencetoflow)第10页，课件共25页，创作于2023年2月Newtonianfluidfrictionlaw(牛顿流体摩擦定律)：AmovewithaspeedV，andBisholdstill,sothatfluidclosetoAmovewithaspeedV,andfluidclosetoBplateisstatic.Themovementofthefluidislaminarflow,thereexistrelativeslipbetweenarbitrarytwolayers,shearstressesexistattheinterfaceoflaminarflow,i.e.,第11页，课件共25页，创作于2023年2月A.Kineticviscosity（动力粘度）

Unit：Pa·s（ISO），N·s/m2（C.G.S,厘米-克-秒制单位）B、Kenimaticviscosity(运动粘度)

Unit：m2/s

＝

／

——FluiddensityC、Specificviscosity(条件粘度)

EUnit：Englerdegree(恩氏度,°Et）Oilnumber(Table4-1):AccordingtoGB/T314-1994,oilnumberisthecentralvalueofkenimaticviscosityat40ºC第12页，课件共25页，创作于2023年2月Influencingfactorofviscosity(影响粘度的因素)Temperature：hightemperaturecauseslowviscosity；Pressure：Viscosityincreaseswithincreasingpress-ure.Whenpressureislowerthan20MPa,itseffectscanbeignored.Whenpressureexceeds20MPa,theymustbeconsidered.

p——Viscosityunderpressurep，Pa·s；

0——Viscosityunderpressure105Pa，Pa·s；

——Pressure–viscositycoefficient(粘压系数)，

＝（1~3）×10-8m2／N。第13页，课件共25页，创作于2023年2月②

Oiliness(油性)Physicalorchemicalabsorptionfilm(吸附膜)→decreasefrictionandwear③Extremepressureproperty(极压性)Createwear-resisting,highpressureresisti-ngchemicalboundaryfilm④Oxidationresistance(氧化稳定性)Theabilitytoresistoxidation⑤

Flashpoint（闪点）andSolidifyingPoint（凝固点）Itisimportanttoworkinhighorlowtemperature

第14页，课件共25页，创作于2023年2月（2）Lubricantgrease（润滑脂）Calciumbase(钙基)grease,Sodium(钠基)basegrease，lithiumbase(锂基)grease,aluminumbase(铝基)grease①Penetration(针入度)Lowerpenetrationincreasesbearingcapacity②Droppingpoint(滴点)Measurethehighthermalresistanceofthegrease第15页，课件共25页，创作于2023年2月（3）Additive（添加剂）EffectsoftheadditiveImproveoiliness,extremepressurepropertyandworkabilityunderextremeoperatingconditions；Deferageingandprolongservicelife；ImprovephysicalpropertyTypicaladditive：detergentdispersant(清净分散剂),antioxidant(抗氧化剂),oilinessadditive(油性添加剂),extreme-pressureandantiwearadditive(极压与抗磨添加剂),pourinhibitor(降凝剂),tackifier(增粘剂)第16页，课件共25页，创作于2023年2月Lubricatingmethods(oilandgreaselubrication）1.Oillubrication(油润滑)Forcefillingoilcup(压注油杯）Oilpotwithturningsleeve（旋套油杯）第17页，课件共25页，创作于2023年2月（1）Dripfeedlubrication(滴油润滑)Oilpotwithneedlevalve(针阀油杯)Wickoiler(油芯注油器)第18页，课件共25页，创作于2023年2月（2）Oil-ringlubrication(油环润滑)（3）Splashlubrication(飞溅润滑)（4）Pressurecirculation(压力循环润滑)第19页，课件共25页，创作于2023年2月2.Greaselubrication(脂润滑)Greasecupwithturningsleeve(旋盖式油脂杯)Greasegun(油脂枪)第20页，课件共25页，创作于2023年2月§4—4Hydrodynamicandhydrostaticlubrication(液体动力润滑和流体静力润滑)I.Newtonianlawoffriction(viscosity)牛顿流体摩擦的摩擦定律（粘性定率）Tangentialstressesinanypointoffluidaredirectlypro-portionaltolocalvelocitygradientProportionalitycoefficients(比例系数)η—

KineticviscosityofthefluidShearresistanceperunitare