专业英语第8课全文及翻译 滚动轴承.doc

Lesson 8 RollingBearingsRollingbearingscancarryradial,thrustorcombinationofthetwoloads.Accordingly,mostrollingbearingsarecategorizedinoneofthethreegroups:radialbearingsforcarryingloadsthatareprimarilyradial,thrustbearingsforsupportingloadsthatareprimarilyaxial,andangularcontactbearingsortaperedrollerbearingsforcarryingcombinedradialandaxialloads.Figure8.1ashowsacommonsingle-row,deepgrooveballbearing.Thebearingconsistsofaninnerring,anouterring,theballsandtheseparator.Toincreasethecontactareaand.hencepermitlargerloadstobecarried,theballsrunincurvilineargroovesintheringscalledraceway.Theradiusoftheracewayisverylittlelargerthantheradiusoftheball.Thistypeofbearingcanstandaradialloadaswellassomethrustload.SomeothertypesofrollingbearingsareshowninFigs.8.1b,8.lcand8.1d.Figure 8.1 Some type: of rolling bearings: (a) deep groove ball bearing; (b) thrust ball bearing; (c) tapered roller thrust bearing;(d) needle roller bearing. Theconcernofamachinedesignerwithballandrollerbearingsisfivefoldasfollows:(a)lifeinrelationtoload;(b)stiffness,i.e.deflectionsunderload;(c)friction;(d)wear;(e)noise.Formoderateloadsandspeedsthecorrectselectionofastandardbearingonthebasisofloadratingwillusuallysecuresatisfactoryperformance.Thedeflectionofthebearingelementswillbecomeimportantwhereloadsarehigh,althoughthisisusuallyoflessmagnitudethanthatoftheshaftsorothercomponentsassociatedwiththebearing.Wherespeedsarehighspecialcoolingarrangementsbecomenecessarywhichmayincreasefrictionaldrag.Wearisprimarilyassociatedwiththeintroductionofcontaminants,andsealingarrangementsmustbechosenwithregardtothehostilityoftheenvironment.Becausethehighqualityandlowpriceofballandrollerbearingsdependsonquantityproduction,thetaskofthemachinedesignerbecomesoneofselectionratherthandesign.Rollingbearingsaregenerallymadewithsteelwhichisthrough-hardenedtoabout900HV.Owingtothehighstressesinvolved,apredominantformoffailureshouldbemetalfatigue,andagooddealofworkiscurrentlyinprogressintendedtoimprovethereliabilityofthistypeofbearing.Designcanbebasedonacceptedvaluesoflifeanditisgeneralpracticeinthebearingindustrytodefinetheloadcapacityofthebearingasthatvaluebelowwhich90percentofabatchwillexceedalifeofonemillionrevolutions.Notwithstandingthefactthatresponsibilityforthebasicdesignofballandrollerbearingsrestswiththebearingmanufacturer,themachinedesignermustformacorrectappreciationofthedutytobeperformedbythebearingandbeconcernednotonlywithbearingselectionbutwiththeconditionsforcorrectinstallation.Thefitofthebearingringsontotheshaftsorontothehousingsisofcriticalimportancebecauseoftheircombinedeffectontheinternalclearanceofthebearingaswellaspreservingthedesireddegreeofinterferencefit.Inadequateinterferencecaninduceserioustroublefromfrettingcorrosion.Theinnerringisfrequentlylocatedaxiallybyabuttingagainstashoulder.Afilletradiusatthispointisessentialfortheavoidanceofstressconcentrationandtheinnerringisprovidedwithacornerradiusorchamfertoallowspaceforthis.Wherelifeisnotthedeterminingfactorindesign,itisusualtodeterminemaximumloadingbytheamounttowhichabearingwilldeflectunderload.Thustheconceptofstaticload-carryingcapacityisunderstoodtomeantheloadthatcanbeappliedtoabearing,whichiseitherstationaryorsubjecttoslightswivelingmotions,withoutimpairingitsrunningqualitiesforsubsequentrotationalmotion.Thishasbeendeterminedbypracticalexperienceastheloadwhichwhenappliedtoabearingresultsinatotaldeformationoftherollingelementandracewayatanypointofcontactnotexceeding0.01percentoftherolling-elementdiameter.Thiswouldcorrespondtoapermanentdeformationof0.0025mmforaball25mmindiameter.Thesuccessfulfunctioningofmanybearingsdependsuponprovidingthemwithadequateprotectionagainsttheirenvironment,andinsomecircumstancestheenvironmentmustbeprotectedfromlubricantsorproductsofdeteriorationofthebearingsurfaces.Achievementofthecorrectfunctioningofsealsisanessentialpartofbearingdesign.Moreover,sealswhichareappliedtomovingpartsforanypurposeareofinteresttotribologistsbecausetheyarecomponentsofbearingsystemsandcanonlybedesignedsatisfactorilyonthebasisoftheappropriatebearingtheory.Notwithstandingtheirimportance,theamountofresearcheffortthathasbeendevotedtotheunderstandingofthebehaviorofsealshasbeensmallwhencomparedwiththatdevotedtootheraspectsofbearingtechnology.WordsandExpressionsradialbearing向心轴承(主要用于承受径向载荷的滚动轴承)thrustbearing推力轴承(主要用于承受轴向载荷的滚动轴承)angularcontactbearing角接触轴承taperedrollerbearing圆锥滚子轴承deepgrooveballbearing深沟球轴承thrustballbearing推力球轴承(滚动体是球的推力滚动轴承)taperedrollerthrustbearing推力圆锥滚子轴承(滚动体是圆锥滚子的推力滚动轴承)needlerollerbearing滚针轴承(滚动体是滚针的向心滚动轴承)fivefolda.;ad.五倍(的)，五重的stiffnessstifnisn.刚性，刚度，稳定性deflectionn.偏差，偏移，弯曲，挠度frictionala.摩擦的，由摩擦产生的dragv.拖，牵引，摩擦，拖着，阻碍;n，阻力，摩擦力，阻尼wearv.n.磨损，磨蚀，消耗，耗损contaminantn.沾染，杂质，污染物质，污染剂sealingn.密封，封接hostilityn.敌视，敌意，敌对through-hardenv.整体淬火HV=Vickershardness维氏硬度 notwithstandingprep.;ad.;conj.虽然，尽管(还是)clearancen.间隙，裕度，空隙，余地，间距interferencen.干涉，干扰，妨碍，过盈，相互影响fretv.侵蚀，腐蚀，磨损，损坏frettingn.松散，微振磨损abutv.邻接，毗连，倚着，支撑;n.端，尽头，支架chamfern.;二在开槽，倒棱，倒角，圆角swiveln.旋转轴承，转体;v.旋转，用活节连接racewayn.轴承座圈，滚道lubricantn.润滑剂，润滑材料;a.润滑的deteriorationn.变质，退化，恶化，变坏tribologyn.摩擦学Notes1.through-hardened意为“整体淬火的，。2.frettingcorrosion意为“微动腐蚀(即由腐蚀和两固体接触面有微小振幅的振动而引起的磨损之联合作用所产生的材料破坏)”。3.staticload-carryingcapacity意为“静态承载能力”。第8课 滚动轴承滚动轴承可以承受径向载荷，轴向载荷或者同时承受这两种载荷。因而，大部分滚动轴承可以被划分为三种类型:向心轴承，主要承受径向载荷；推理轴承，主要承受轴向载荷；角接触轴承货圆锥滚子轴承，能同时承受径向和轴向载荷。一个普通的蛋类深沟球轴承的结构如图8.1a所示，它由内圈、外圈、球和保持架四部分组成。为了增加接触面积以承受更大的载荷，球在内、外圈上的被称为滚到的弧形沟内滚动。滚道的圆弧半径略大于滚动球的半径。这种轴承能够承受径向载荷，也可以承受一定的轴向载荷。其他几种类型的滚动轴承如图8.1b，图8.1c和图8.1d所示。对于球轴承和滚子轴承，一个机器设计人员应该考虑下面的五个方面：（a）寿命与载荷的关系；（b）刚度，也就是在载荷作用下的变形；（c）摩擦；（d）磨损；（e）噪音。对于中等载荷和转速，根据额定负载选择一个标准轴承，通常都可以保证其具有令人满意的工作性能。当载荷较大时，轴承零件的变形，尽管它通常小于轴和其他与轴承一起工作的零部件的变形，将会变得更重要起来。在转速高的场合需要有专门的冷却装置，而这可能会增大摩擦阻力。磨损主要是由于污染物的进入引起的，必须选用密封装置以防止周围环境的不良影响。因为大批量生产这种方式决定了球轴承和滚子轴承不但质量高，而且价格低，因而机器设计人员的任务是选择而不是设计轴承。滚动轴承通常是采用硬度约为900HV，整体淬火的钢来制造的。滚动轴承由于在工作中会产生高的应力，其主要失效形式是金属疲劳。目前人们正在进行大量的研究工作以求提高这种轴承的可靠性。轴承设计是基于能够够被人们所接受的使命值来进行的。在轴承行业中，通常将轴承的承载能力定义为这样的值，即所承担的载荷小于值时，一批轴承