毕业论文外文翻译-轴承的摩擦与润滑

《毕业论文外文翻译-轴承的摩擦与润滑》由会员上传分享，免费在线阅读，更多相关内容在工程资料-天天文库。

1、外文文献原文:Friction,LubricationofBearingInmanyoftheproblemthusfar,thestudenthasbeenaskedtodisregardorneglectfriction•Actually,frictionispresenttosomedegreewhenevertwopartsareincontactandmoveoneachother.Thetermfrictionreferstotheresistanceoftwoormorepartstomovement.Frictionisharmf

2、ulorvaluabledependinguponwhereitoccurs,frictionisnecessaryforfasteningdevicessuchasscrewsandrivetswhichdependuponfrictiontoholdthefastenerandthepartstogcthcr.Beltdrivers,brakes,andtiresarcadditionalapplicationswherefrictionisnecessary.Thefrictionofmovingpartsinamachineisharmf

3、ulbecauseitreducesthemechanicaladvantageofthedevice.Theheatproducedbyfrictionislostenergybecausenoworktakesplace.Also,greaterpowerisrequiredtoovercometheincreasedfriction.Heatisdestructiveinthatitcausesexpansion.Expansionmaycauseabearingorslidingsurfacetofittightcr.Ifagreaten

4、oughpressurebuildsupbecausemadefromlowtemperaturematerialsmaymelt.Therearethreetypesoffrictionwhichmustbeovercomeinmovingparts:(1)starting,(2)sliding,and(3)rolling.Startingfrictionisthefrictionbetweentwosolidsthattendtoresistmovement.Whentwopartsareatastateofrest,thesurfaceir

5、regularitiesofbothpartstendtointerlockandformawedgingaction.Toproducemotionintheseparts,thewedge-shapedpeaksandvalleysofthestationarysurfacesmustbemadetoslideoutandovereachother.Therougherthetwosurfaces,thegreaterisstartingfrictionresultingfromtheirmovement•Sincethereisusuall

6、ynofixedpatternbetweenthepeaksandvalleysoftwomatingparts，theirregularitiesdonotinterlockoncethepartsareinmotionbutslideovereachother.Thefrictionofthetwosurfacesisknownasslidingfriction.Asshowninfigure，startingfrictionisalwaysgreaterthanslidingfriction•Rollingfrictionoccurswhe

7、nrollerdevcesaresubjectedtotremendousstresswhichcausethepartstochangeshapeordeform.Undertheseconditions，thematerialinfrontofarollertendstopileupandforcestheobjecttorollslightlyuphill.Thischangingofshape,knownasdeformation,causesamovementofmolecules.Asaresult,heatisproducedfro

8、mtheaddedenergyrequiredtokeepthepartsturningandovercomefriction.Thef