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wordruggedrgid a.结实的，坚固的filletfilit n.嵌条，(内)圆角notchnt n.;vt.槽口，凹口，刻痕，开槽tolerancetlrns n.;vt.公差，容许量nuisancenju:sns n.讨厌的人或东西，麻烦事loosenlu:sn v.解开，放松，松开radiatorreidieitn.散热器，电暖炉，辐射体 Designofmachineandmachineelements1wordfracturefrkt v.;n.(使)断裂，(使)破裂碎wearw v.;n.磨损蚀，破，坏，损耗(量)stressconcentration应力集中geometricdimetrik a.几何的，几何学的discontinuitydisconti nju(:)iti n.间断，不连续，中断Designofmachineandmachineelements2Machine designMachine design is the art of planning ordevisingdvazneworimprovedmachinestoaccomplishspecificpurposes.Ingeneral,amachinewillconsistofacombination of several different mechanicalelements properly designed and arranged toworktogether,asawhole.机器设计是计划或设计(发明)新的或改进机器以达到特定目的的艺术。一般来说，一台机器将由几个不同的机械元件组合而成，它们被适当地设计和排列成一个整体。3Machine designDuringtheinitialplanningofamachine,fundamentalfndmentldecisions dsn must be made concerning loading,type ofkinematicknmtkelementstobeused,andcorrectutilizationjutlazenofthepropertiesofengineeringmaterials.在对机器进行初步规划时，必须对装载、使用的运动(学的)元件的类型和工程材料的正确使用作出基本决定。4Machine designEconomici:kn:mkconsiderationsareusuallyofprimepramimportance when the design of new machinery is undertaken.Ingeneral,thelowestover-allcostsaredesigned.在设计新机器时，经济的因素通常是最重要的。一般来说，选择总成本最低的设计方案。undertakenndteknv.担任;着手5Machine designConsiderationshouldbegivennotonlytothecostofdesign,manufacture,saleandinstallation,but also to the cost of servicings:rvs.The machine should of courseincorporatenk:rpretthenecessarysafety features and be of pleasing externalappearance.不仅要考虑设计、制造、销售和安装的费用，还要考虑服务的成本。机器当然应该包括必要的安全特性和美观的外形。pleasingplizadj.令人愉快的，讨人喜欢的6Machine designTheobjectiveistoproduceamachinewhichisnotonlysufficientlysfntlruggedrdtofunctionproperlyforareasonablelife,but is at the same time cheap enough to be economicallyi:kn:mklifeasiblefizbl.目标是要生产一台机器，它不仅在合理寿命期内坚固耐用，同时价格低廉足以在经济上是可行的。7Machine designThe engineer in charge of the design of amachine should not only have adequatedkwt technical training,but must be amanofsoundjudgmentandwideexperience,qualitieswhichareusuallyacquiredonlyafterconsiderable time has been spent in actualprofessionalwork.负责设计一台机器的工程师，不仅应有足够的技术训练，而且还必须是一个有正确(良好的)判断力和丰富经验的人，只有花费大量(相当大的)时间从事实际专业工作后才能获得这种素质。8Design of machine elementsTheprinciplesofdesignare,ofcourse,universalju:nv:rsl.Thesametheoryorequationsmaybeappliedtoaverysmallpart,asinaninstrumentnstrmnt,or,toalargerbutsimilarpartusedinapieceofheavyequipment.当然，设计原则是普遍的。同样的理论或公式可以应用于一个非常小的零件上，如在一个仪器中，或在一个重型设备中使用的较大但相似的零件上。9Design of machine elementsIn no case,however,should mathematicalmmtkl calculations klkjlenzbelookeduponp:nasabsoluteandfinal.They are all subject sbdekt to theaccuracykjrsiofthevariousassumptionssmpnz,whichmustnecessarilynssrlibemadeinengineeringwork.既然如此，毫无疑问，数学计算不应该被看作是绝对的和最终的。它们都要服从(adj)各种假设的准确性，而这些假设必须(的)在工程工作中进行。10Design of machine elementsSometimesonlyaportionp:rnofthetotalnumberofpartsinamachine are designed on the basis of analytic nltkcalculations.The form and size of the remaining parts are thenusuallydeterminedbypracticalconsiderations.有时，机器中零件的总数量只有一部分是在分析计算的基础上设计的。其余部分的形状和尺寸通常由实际考虑来确定。11Design of machine elementsOntheotherhand,ifthemachineisveryexpensive,orifweightisafactor,asinairplanes,designcomputationsmaythenbemadeforalmostalltheparts.另一方面，如果机器非常昂贵，或者重量是一个因素，就像飞机一样，那么几乎所有零件都可以进行设计计算。12Design of machine elementsThepurposeofthedesigncalculationsis,ofcourse,to attempt to predict the stress ordeformation in the part in order that it maysafelycarrytheloads,whichwillbeimposedonit,andthatitmaylastfortheexpectedlifeofthemachine.设计计算的目的当然是试图预测零件的应力或变形，以便它能够安全地承受载荷，这是必要的，并且其也许会影响到机器的预期寿命。imposempozvt.强加13Design of machine elementsAllcalculationsare,ofcourse,dependentonthephysicalpropertiesof the construction knstrkn materials as determined bylaboratorytests.当然，所有的计算都取决于实验室试验所确定的建筑(工程)材料的物理性质。14Design of machine elementsArationalmethodofdesignattemptstotaketheresultsofrelativelysimpleandfundamentaltestssuchastension,compression,torsion,and fatigue and applythem to all the complicated and involvedsituationsencounteredinpresent-daymachinery.一种合理的设计方法，试图将相对简单而基本的测试结果，如拉伸、压缩、扭转和疲劳等结果及应用到当今机械所遇到的所有复杂和牵涉的情况中。15Design of machine elementsInaddition,ithasbeenamplymplprovedthatsuchdetailsassurface condition,fillets flts,notches nt,manufacturingtolerances,andheattreatmenthaveamarketeffectonthestrengthandusefullifeofamachinepart.另外，充分证明了表面条件、圆角、缺口、加工公差和热处理等细节对机械零件的强度和使用寿命有着一定的影响。16Design of machine elementsThe design and drafting departments must specify spsfacompletelyallsuchparticulars,andthusexercisethenecessaryclosecontroloverthefinishedproduct.设计和起草部门必须明确规定所有这些细节，从而对成品进行必要的严格控制。exerciseeksrsazn.运动vi.练习17Design of machine elementsAs mentioned above,machine design is a vast vst field ofengineeringtechnology.Assuch,itbeginswiththeconceptionofanidea and follows through the various phases of design analysis,manufacturing,marketing,andconsumerismknsju:mrzm.综上所述，机械设计是一个巨大的工程技术领域。例如，从设计理念到设计分析的每一个阶段，制造，市场及销售。18Design of machine elementsThe major areas of consideration in the generalfieldofmachinedesignareasfollows:1)Initialdesignconception2)Strengthanalysis3)Materialsselection4)Appearance5)Manufacturability6)Economyk:nmi7)Safety8)Environmentnvarnmnteffects9)Reliabilityandlife10)Legalconsiderations在机械设计的一般领域中，主要考虑的范畴如下：1)初步设计构思2)强度分析3)材料选择4)外观5)可制造性6)经济性7)安全8)环境效应(果)9)可靠性和寿命10)合法(法律)的考虑19Failure Analysis and Dimensional DeterminationItisabsolutelyessentialsnlthatadesignengineerknowshowandwhypartsfailsothatreliable machines which require minimummaintenancecanbedesigned.Sometimes,afailure can be serious,such as when a tireblowsblooutonanautomobiletravelingathighspeeds.显而易见的设计工程师必须(必要的)知道零件的故障原因，这样就可以设计出最低维护要求而可靠的机器。有时，故障可能是严重的，例如当轮胎在高速行驶的汽车上爆胎时。20Failure Analysis and Dimensional DeterminationOntheotherhand,afailuremaybenomorethananuisance.Anexampleisthelooseningoftheradiatorhoseintheautomobilecoolingsystem.Theconsequenceofthislatterfailureisusuallythelossofsomeradiatorcoolant,aconditionwhichisreadilyrdlidetectedandcorrected.另一方面，失效是一件讨厌的事。汽车冷却系统中散热器软管的松动就是一个例子。这种故障的后果通常是一些散热器冷却剂的损耗，这种情况很容易被检测和纠正。21Failure Analysis and Dimensional DeterminationThetypeofloadapartabsorbsbs:rbzisjustassignificantasthemagnitude.Generally speaking,dynamic loads with directionreversals rv:slz cause greater difficulties than static loads and,therefore,fatiguestrengthmustbeconsidered.零件吸收的载荷类型是相当重要的。一般来说，有方向反转的动载荷比静载荷造成更大的困难，因此必须考虑疲劳强度。22Failure Analysis and Dimensional DeterminationAnotherconcerniswhetherthematerialisductileorbrittlebrtl.Forexample,brittlematerialsareconsideredtobeunacceptablewherefatigueisinvolved.另一个问题是这种材料是韧性的还是易碎的。例如，在涉及疲劳的情况下，易碎的材料被认为是不可接受的。ductilitydktilitin.延(展)性，韧性fragilityfrdltn.脆性23Failure Analysis and Dimensional DeterminationManypeoplemistakinglyinterpretnt:rprtthewordfailuretomeanthe actual breakage of a part.However,a design engineer mustconsider a broader br:dr understanding of what constitutesknsttju:tsfailure.许多人错误地解释“失败”这个词意味着一个零件的实际破坏。然而，设计工程师必须考虑更广泛的理解是什么构成了失败。24Failure Analysis and Dimensional DeterminationForexample,abrittlematerialwillfailundertensileloadbeforeanyappreciablepribldeformationoccursk:z.Aductilematerial,howeverwilldeformalargeamountpriorpratorupturerpt.例如，易碎的材料在任何明显的(相当可观的)变形发生之前都会在拉伸载荷下失效。然而，韧性材料在破裂之前会大量变形。25Failure Analysis and Dimensional DeterminationExcessive kssv deformation,without fracture,may cause amachinetofailbecausethedeformedpartinterferesntrfrzwithamovingsecondpart.过大的变形，没有断裂，可能导致机器失效，因为变形部分干扰(干涉)移动的第二部分。26Failure Analysis and Dimensional DeterminationTherefore,apartfails(evenifithasnotphysicallybroken)wheneveritnolongerfulfillsflflitsrequiredfunction.Sometimesfailuremaybe due to wear that can change the correct position of matingmetparts.因此，当一个零件不再履行(执行)其所需的功能时，它就失效（即使它没有物理损坏）。有时故障可能是由于磨损而改变了匹配(配合)部件的正确位置。27Failure Analysis and Dimensional DeterminationThewearmaybeduetoabnormalbn:rmlfrictionorvibrationbetweentwomatingparts.Failurealsomaybeduetoaphenomenoncalled creep,which is the plastic flow of a material under load atelevatedlvetdtemperatures.磨损可能是由于两个零件之间的摩擦或振动异常引起的。故障也可能是由于蠕变现象，即材料在负载及(提)高温下的塑性流动。28Failure Analysis and Dimensional DeterminationIn addition,the actual shape of a part may be responsiblersp:nsblforfailure.Forexample,stressconcentrationsduetosuddenchangesincontourk:ntrmustbetakenintoaccount.此外，零件的实际形状可能要对失败负有责任的。例如，必须考虑由于轮廓突变引起的应力集中。29Failure Analysis and Dimensional DeterminationEvaluation vljen of stress considerations is especiallyimportantwhentherearedynamicloadswithdirectionreversalsandthematerialisnotveryductile.当有方向反转的动态载荷和材料不是很有韧性时，应力的考虑尤其重要。Evaluationvljenn.评价(评估)30Failure Analysis and Dimensional DeterminationIngeneral,thedesignengineermustconsiderallpossiblemodesoffailure,whichincludethefollowing:1)stress2)deformation3)wear4)corrosion5)vibration6)environmentaldamagedmd7)looseningoffasteningfsndevices一般来说，设计工程师必须考虑所有可能的失效模式，其中包括以下几点：1)应力2)变形3)磨损4)腐蚀5)振动6)环境损害7)紧固装置松动31Failure Analysis and Dimensional DeterminationThepartsizesandshapesselectedmustalsotakeintoaccountmanydimensional factors which produce external load effects such asgeometricdiscontinuities,residualrzdulstressesduetoformingofdesiredcontours,andtheapplicationofinterferencefitjoints.所选择的零件尺寸和形状也必须考虑到许多会产生外部载荷效应的维度因素，如几何不连续性、成形加工预期轮廓引起的残余应力以及过盈(干涉)配合接头的应用。3233
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