机械工程专业英语课件

机械工程

专业英语机械工程

1课程介绍学习专业英语的重要性学习目的为何在大三开设这门课程专业英语的英文名称“专业英语”-----EnglishforSpecialPurposeSpecifiedEnglishfor…….“机械工程专业英语”SpecifiedEnglishforMechanicalEngineering专业英语和普通英语的区别一.词义特点1.根据词类辨明词义课程介绍学习专业英语的重要性2

e.g:(1)Round(adj.)surfacereflectorisakeyunitforthesolarenergydevice.曲面反射器是太阳能装置的关键元件。(2)Thisisthewholeround(n.)ofknowledge.这是全部知识范围。2.区分场合确定词义（不同的场合，词义也不一样。要根据上下文和语言环境来确定词义）e.g:(1)pig:猪~iron生铁(机械专业)~metal金属锭~copper生铜(2)dog:狗(机械专业)~鸡心夹头,挡块

e.g:(1)Round(adj.3

3.按照习惯搭配词义e.g:(1)Ihaveashortmemory.(2)Thisbiscuiteatsshort.(3)Indeedhehasashorttemper.4.联系上下文活用词义e.g:(1)Thereisnophysicalcontactbetweentoolandworkpiece.工具和工件之间没有有形（直接）的接触。(2)High-speedgrindingdoesnotknowthisdisadvantage高速磨削不知道（存在）这个缺点。3.按照习惯搭配词义4二.句子结构特点

1.句子长2.被动语态多e.g:Therateatwhichworkisdoneiscalledpower.3.后置定语多4.名词化结构多e.g:tocontrolthemachine----thecontrolofthemachine

二.句子结构特点5学习方法与教学方法工具书的介绍

1.收词不足,收词量有限2.收词面广3.例证丰富4.释义地道,全面5.词的用法说明较详细学习方法与教学方法6Lesson1IntroductionforMaterialsDesignersandengineersareusuallymore

interestedinthebehaviorofmaterialsunderloadorwheninamagneticfieldthaninwhytheybehaveastheydo.1.are….moreinterestedin….thanin

对…..比对…..更兴趣2.underload：承载时Yetthebetteroneunderstandsthenatureofmaterialsandthereasonsfortheirphysicalandmechanicalpropertiesthemorequicklyandwiselywillhe/shebeabletochoosethepropermaterialforagivendesign.

1.thebetter….themorequicklyandwisely:越….越…..2.agivendesign:某个设计

Lesson1IntroductionforMa7Generally,amaterialpropertyisthemeasuredmagnitudeofitsresponsetoastandardtestperformedaccordingtoastandardprocedureinagivenenvironment.1.themeasuredmagnitude:测定的大小2.responseto:对…..的反应Inengineeringmaterialsthepropertiesarerecordedinhandbooksor,fornewmaterials,aremadeavailablebythesupplier.

makesth.+形容词(sth.bemake=形容词):使….怎么样thepropertiesaremadeavailable:使……可获得Generally,amaterialproperty8Frequentlysuchinformationistabulatedforroom-temperatureconditionsonly,sowhentheactualserviceconditionsareatsubfreezingorelevatedtemperatures,moreinformationisneeded.

1.room-temperatureconditions:室温状态2.theactualserviceconditions：实际工作状态3.elevatedtemperatures：高温Frequentlysuchinformationis9Thepropertiesofmaterialsaresometimesreferredtoasstructuresensitive,ascomparedtostructure-insensitiveproperties.1.bereferredtoas,beknownas:称为2.(as)comparedto(with):

与…相比,同….比较起来,与…相对应

3.structuresensitive,structure-insensitiveproperties

结构敏感性,结构不敏感性Inthiscasestructure-insensitivepropertiesincludethetraditionalphysicalproperties:electricalandthermalconductivity,specificheat,density,andmagneticandopticalproperties.electricalandthermalconductivity:导热性与导电性specificheat:比热specificweight:比重Thepropertiesofmaterialsar10Thestructure-sensitivepropertiesincludethetensileandyieldstrength,hardness,andimpact,creep,andfatigueresistance.1.thetensile(strength)andyieldstrength:拉伸强度和屈服强度2.impact,creep,andfatigueresistance:抗冲击性,抗蠕性,抗疲劳性Itisrecognizedthatsomesourcesmaintainthathardnessisnotatruemechanicalproperty,becauseitvariessomewhatwiththecharacteristicsoftheindenterandthereforeisatechnologicaltest.Itisrecognizedthat….认出,识别,考虑(认识)到somesourcesmaintain:一些资料(文件)Thestructure-sensitiveproper11

Itiswellknownthatothermechanicalpropertiesvarysignificantlywithrateofloading,temperature,geometryofnotchinimpacttesting,andthesizeandgeometryofthetestspecimen.

1.rateofloading:载荷大小2.geometryofnotchinimpacttesting:

试验中缺口的几何形状Itiswellknownthatotherm12Furthermore,sincereportedtestvaluesofmaterialpropertiesarestatisticalaverages,acommercialmaterialfrequentlyhasatolerancebandof±5percentormoredeviationfrom

agivenpublishedvalue.1.reportedtestvalues:所报道的测量值2.statisticalaverages:统计平均值3.commercialmaterial:商用材料4.toleranceband:公差带5.deviationfrom:与….的偏差6.agivenpublishedvalue:某个公布的值Furthermore,sincereportedte13Thepropertiesofmaterialsaresometimesreferredtoasstructuresensitive,ascomparedtostructure-insensitiveproperties.

bereferredtoas:指的是….;叫做;beknownas:称为;叫做Inthiscasestructure-insensitivepropertiesincludethetraditionalphysicalproperties:electricalandthermalconductivity,specificheat,density,andmagneticandopticalproperties.

1.electricalandthermalconductivity:导热性与导电性2.specificheat:比热specificweight:比重Thepropertiesofmaterialsar14

Thestructure-sensitivepropertiesincludethetensileandyieldstrength,hardness,andimpact,creep,andfatigueresistance.

1.tensileandyieldstrengthtensile(strength)andyieldstrength2.impact,creep,andfatigueresistanceimpact(resistance),creep(resistance),andfatigueresistance

抗冲击性,抗蠕变性和抗疲劳性

Itisrecognizedthatsomesourcesmaintainthathardnessisnotatruemechanicalproperty,becauseitvariessomewhat

withthecharacteristicsoftheindenterandthereforeisatechnologicaltest.

1.Itisrecognizedthat…..Itisknownthat…..Itissaidthat…..2.….varywith……Thestructure-sensitivepro15Furthermore,sincereportedtestvaluesofmaterialpropertiesarestatisticalaverages,acommercialmaterialfrequentlyhasatolerancebandof±5percentormoredeviationfromagivenpublishedvalue.…..hasatolerancebandof±5percentormoredeviationfrom……

Anyparticularmaterialcanbedescribedbyitsbehavior

whensubjectedtoexternalconditions.….describedbybehaviorwhen(anyparticularmaterial)subjectedtoexternalcondition(外力作用)Thus,whenitisloadedunderknownconditionsof

direction,magnitude,rate,andenvironment,theresultingresponsesarecalledmechanicalproperties.Whenitisloadedunderknownconditionsofdirection,magnitude,rate,andenvironment….Furthermore,sincereportedte16Mechanicalpropertiessuchasyieldstrength,impactstrength,hardness,creepandfatigueresistancearestronglystructure-sensitive,i.e.,theydependuponthearrangementoftheatomsinthecrystallatticeandonanyimperfectionsinthatarrangement,whereasthephysicalpropertiesarelessstructure-sensitive.

arrangementoftheatoms:原子排列Mechanicalpropertiessuchas17Theseincludeelectrical,thermal,magnetic,andopticalpropertiesanddodependinpartuponstructure;forexample,theresistivityofametalincreaseswiththeamountofcoldwork.1.inpart:部分2.increaseswith:随着….而提高3.coldwork:冷作;冷成型,冷加工Physicalpropertiesdependprimarilyupontherelativeexcessordeficiencyoftheelectronsthatestablishstructuralbondsandupontheiravailabilityandmobility.

1.excessordeficiency:超过或不足2.structuralbonds:结构键Theseincludeelectrical,ther18Betweentheconductorswithhighelectronmobilityandtheinsulatorswithnofreeelectrons,precisecontroloftheatomicarchitecturehascreatedsemiconductorsthatcanhaveaplannedmodificationoftheirelectronmobility.

1.highelectronmobility:高电子迁移率2.theconductorswithhighelectronmobility:高电子迁移率的导体3.theinsulatorswithnofreeelectrons:无自由电子的绝缘体4.semiconductorsthatcanhaveaplannedmodificationoftheirelectronmobility有计划改变电子迁移的半导体Betweentheconductorswithhi19Similarly,advancesinsolid-stateopticshaveledtothedevelopmentofthestimulatedemissionofelectromagneticenergyinthemicrowavespectrum(masers)andinthevisiblespectrum(lasers).1.solid-stateoptics:固态光学器件2.thestimulatedemission:激射Similarly,advancesinsolid-s20Instudyingthegeneralstructureofmaterials,onemayconsiderthreegroupings;first,atomicstructure,electronicconfiguration,bondingforces,andthearrangementoftheaggregationsofatoms;second,thephysicalaspectofmaterials,includingpropertiessuchaselectricalandthermalconductivity,specificheat,andmagnetism;andthird,theirmacroscopicproperties,suchastheirmechanicalbehaviorunderload,whichcanbeexplainedintermsofimpuritiesandimperfectionsinthelatticestructureandtheproceduresusedtomodifythatbehavior.

1.bondingforces:结合力2.aggregationsofatoms:原子团3.intermsof:用….语言来….Instudyingthegeneralstruct21专业英语的特点专业英语（specifiedEnglish）是在自然科学和工程技术的专业领域中使用的一种英语文体。它是在专业技术的不断发展中逐渐形成并与专业技术同步发展的。由于专业技术的要求语言表述能客观、严谨地反映科学研究的内容，所以，专业英语的特点，除了包含一些实验数据、公式推导和数学符号以外，在词汇含义、语法结构、句型使用和修辞手法等方面与日常英语、文学英语有不同的特点。这诚如著名科学家钱三强指出的：专业英语“无论在语法结构或词汇方面都逐渐形成它特有的习惯用法、特点与规律”。不学习和掌握这些特点与规律，就很难搞好专业英语的阅读、翻译和写作。为了掌握这些特点和规律，本章及下一章节将主要介绍专业英语的语法特点和词汇特点。专业英语的特点专业英语（specifiedEnglish）22一．专业英语的语法特点1．无人称（Impersonal）（无生命的第三人称语气或非人称语气）

科技文体第一个显著的特点就是较多地使用无生命的第三人称语气。例如：

Steppermotorsareusefulwhereveraccuratecontrolofmovementisrequired.Theyareusedextensivelyinroboticsandinprinters,plottersandcomputerdiskdrives,allofwhichrequireprecisepositioningorspeed.凡需要精确控制运动的地方,步进电机都非常有用。他们广泛用于机器人技术,打印机,绘图仪和计算机磁盘驱动器，这些需要精确的定位或速度。一．专业英语的语法特点1．无人称（Impersonal）（232．被动语态(PassiveVoice)

由于专业英语文献侧重叙事和推理，陈述的对象是客观事物。读者重视的是作者的观点和发明的内容，而不是作者本人。因此在语言表述中必然较多地使用以客观事物为主体的被动语态。专业英语中的被动语句不一定要说出行为主体，特别当行为主体是人时。但有时也用“by”引出行为者。这些行为者除了人、机构、物质以外，还包括完成该动作的方法、原因或过程等。例如：Thetemperatureoftheliquidisraisedbytheapplicationofheat.加热可以提高液体温度。Therateatwhichworkisdoneiscalledpower.3．非谓语动词动词非谓语形式有：动名词、分词、动词不定式及它们的复合结构。专业英语中，动词的非谓语形式应用广泛，这是因为专业英语要求准确、精炼，而动词的非谓语形式可以很好地实现这些要求。比如采用这一形式能用扩展的成分对所修饰的词进行严格的说明和限定。其中每一个分词定语都能代替一个从句，从而可使很长的句子匀称,避免复杂的主从符合结构，并省略动词时态的配合，使句子即不累赘又语意明确。

2．被动语态(PassiveVoice)243.1分词的使用在专业英语中，分词短语被大量地用作定语、状语和独立分词结构，取代被动态或主动态的关系从句，使句子结构得到简化。例如：1.Rammers

drivenbycompressedaircanincreasetheproductionrates.压缩空气驱动的舂砂器可以提高生产效率。2.Originallydesignedforrapid,automaticproductionofscrewsand

similarthreadedparts,theautomaticscrewmachinehaslongsinceexceededtheconfinesofthisnarrowfield,andtodayplaysavitalroleinthemassproductionofavarietyofprecisionparts.自动螺丝车床最初是用来对螺钉和类似的带有螺纹的零件进行自动化快速加工的。但是，这种车床的用途早就超过了这个狭窄的范围。现在，它在许多种类的精密零件的大批量生产中起着重要的作用。3.1分词的使用25分词独立结构，即：名词或代词＋分词短语，是一种主谓结构，在句中的作用相当于并列分句或从句。例如：3.Agitationiscritical,theaimbeingtodistributesiliconcarbideparticleshomogeneouslythroughoutthealuminummelt.搅拌至关重要，其目的是将碳化硅颗粒均匀地分布在整个铝液中。

分词独立结构前加with(without)变成起状语作用的介词短语，用于当分词的逻辑主语与句子主语不一致时。4.Intheheatexchangerofblastfurnacetheairflowsthroughtheoutsidepipe,thegasthroughtheinsidepipe,withheatexchangetakingplacethroughthewall.在高炉热交换器中，空气流过外管，燃气流过内管，热交换通过管壁进行。分词独立结构，即：名词或代词＋分词短语，是26

3.2动名词的使用动名词构成的介词短语可取代状语从句或简化陈述句，在英语中广泛应用。例如：

Inredesigninganexperimentalpartforproduction,economicaltolerancesshouldbeused.为了生产而重新设计试件时,必须使用经济公差。3.2动名词的使用273.3不定式的使用不定式在专业英语中的使用也十分频繁，在句中常用来替换表示目的功能的从句，使句子结构简练。例如：1.Toinsuremanufacturequalityofelectrodes,theAmericanWeldingSocietyhassetupcertainrequirementsforelectrodes.为了确保电极的制造质量，美国焊接学会规定了电极必须具备的一些条件。2.Thereishighrequirementofskillincarryingoutthisoperationto

produceproductswithhighperformances.进行这项操作时需要很高的技巧，以生产出具有高性能的产品。3.3不定式的使用284.名词化结构“表示动作意义的名词＋of＋名词＋修饰语”叫做名词化结构。名词化结构具有文字明了、用词简洁、结构紧凑、表意客观、信息容量大等特点，在专业英语中经常用它代替主、谓结构作各种句子成分，使句子结构简化。例如:用普通英语表达这样一句话：Theultrasonicmetalinspectionistoapplyultrasonicvibrationstomaterialswithelasticpropertiesandtoobservetheresultingactionofthevibrationsinthematerials.用名词化结构如下表述：Theultrasonicmetalinspectionistheapplicationofultrasonicvibrationstomaterialswithelasticpropertiesandtheobservationoftheresultingactionofthevibrationsinthematerials.金属超声波探伤是将超声振动施于具有弹性的材料，并观察振动在材料中产生的作用。4.名词化结构29二．专业英语的词汇特点专业英语词汇的组成专业技术词汇：polymerization聚合作用diathermometer热阻测定仪mechatronics机电一体化，机械电子学lathe车床半专业技术词汇：power力量,权力（日常英语）动力（机械专业）电力（电力专业）幂(数学专业）功率（物理专业）爆发力（体育专业）二．专业英语的词汇特点30构词法

英语的构词法包括转化、合成、派生三种形式。转化(conversion)如：

melt熔液——tomelt熔化finish光洁度——tofinish精加工、抛光alloy合金——toalloy使成合金复合法(composition)如：

waveform波形ballbearing滚珠轴承workshop车间toolroom工具室派生或词缀(derivation)如：

unavoidable不可避免的inaccuracy不精确构词法31词汇缩略首字词缩略:它是由原词组的每个词首字母组成，在阅读中首字词要逐字母读.例如：

NC数控AC自适应控制PLC可编程控制器AIEEAmericanInstituteofElectrical(Electronic)Engineers美国电气（电子）工程师学会首字词拼音:把一个词组中的首字母拼凑成一个词.例如laser—lightamplificationbystimulatedemissionofradiation激光ROM——readonlymemory只读存储器AIDS——acquiredimmunedeficiencysyndrome爱滋病词汇缩略32节略词:某些词使用频率高,为了方便，在发展过程逐渐用它们的前几个字母来表示。例如：

ref.——reference参考文献lab.——laboratory实验室in.——inch英吋ft.——foot英呎缩写词

例如：

etc.—etcetera等等i.e—thatis即e.g.—forexample例如vs.—versus对…

拼缀:即以组成复合词的各个词中各抽取一或两个词缀相拼合。例如：

transeiver(transistor＋receiver)收发机mechatronics(mechanics＋electronics)机电一体化节略词:某些词使用频率高,为了方便，在发展过程逐渐用33distinguish区别；区分distort:变形bymeansof:借助于permanent:永久的coefficient:系数steelmill:钢厂expansion：膨胀roll:轧锟reactto:对….起作用;对….的反应crack:裂开,裂纹,破裂inconnectionwith:与…..有关gradually:逐渐地fivebroadcategories:五大类elasticity:弹性ductility:延展性toughness:韧性elevator:升降机cable:电缆beam:横梁penetration:压痕,凹痕abrasion:磨损elongate:延长，伸长distinguish区别；区分34Lesson2MetalsandFerrousMetalsferrousa.铁类的，黑色的nonferrousa.有色的twogeneraltypes两大类broadmain

However,somenonferrousmetalsmaycontainasmallamountofironasanimpurity.

asmallamountof:少量的alargeamountof:大量的

varyingamounts:不同数量的Lesson2MetalsandFerrou35Steelandcastironarethemostcommonferrousmetalsingeneraluse.

castiron铸铁

generaluse

普通的用途Steelisanalloycontainingchieflyiron,……andcertainotherelementsinvaryingamounts.Awiderangeofphysicalpropertiesmaybeobtainedinsteelbycontrollingtheamountofcarbonandotheralloyingelementsandbysubjectingthesteeltovariousheattreatment.

awiderangeof:各种各样的，形形色色的besubjectedto:易受到，承受subjectsth.to……:使….承受…..Alloysteelsareformedbytheadditionofoneormoreofthefollowingelements.Steelandcastironarethemo36byfar:迄今Itistheamountofcarbonpresentwhichlargelydeterminesthemaximumhardnessobtainable.

Itis+强调部分+which……..Thehigherthecarboncontent,thehigherthetensilestrengthandthegreaterthehardnesstowhichthesteelmaybeheat-treated.

→Thesteelmaybeheat-treatedtothehardness.…….partsrequiringagreatdealofforming.

agreatdealof……:大量Medium-carbonsteelsareusedforforgingsandotherapplicationswhereincreasedstrengthandacertainamountofductilityarenecessary.Alloysteelshavespecialpropertiesdeterminedbythemixtureandtheamountofmetalsadded.mixture:混合物→金属种类byfar:迄今37Tothemetallurgistwhoworksinmetalminingandmanufacturing,steelscontainingverysmallquantitiesofelementsotherthancarbon,phosphorus,sulphur,andsiliconareknownasalloysteels.workin：从事otherthan：除了……..beknownas……:叫做,称为beknownfor….:因….而著名beknownto……:被知道Eachalloysteelhasapersonalityofitsown.机械工程专业英语课件38

Tool-and-diesteelsarealargegroupofsteelsusedwhencarefulheat-treatingmustbedone.Thesesteelsareusedforpartssuchaschisels,hammers,screwdrivers,springs,andtoolsanddies

usedtocutandformmetals.

Toolsteelswithcertainalloyingelementsaredesignedfor

specificuses.bedesignedto…..设计成能(做),用来…,目的是使…bedesignedfor…..用做…用途;为….而设计specific:a.1.比率，单位的e.g:specificheat,specificweight2.特殊(定,有,种)的;专门的;具体的,明确的

Tool-and-diesteelsarealar39

Themostcommonkindsoftoolsteelsincludehigh-speedtoolsteels,hotworktoolsteels,coldworktoolsteelsandspecial-purposetoolsteels.hotworktoolsteels热加工工具钢

coldworktoolsteels

冷加工工具钢special-purpose专用的special-purposemachinesgeneral-purpose通用的general-purposemachines

Themostcommonkindsoftool40

Rolledsteel,whichincludesbar,rod,andstructuralsteels,isproducedbyrollingthesteelintoshape.bar扁钢rod圆钢byrollingthesteelintoshape轧制成形的方法….Hot-rolledsteelsareformedintoshapewhilethemetalisred-hot.

areformedintoshape成形Themetalpassesthroughaseriesofrollers,eachalittleclosertothenextone.

roller:轧锟each,one----aseriesofrollers

Rolledsteel,whichincludes41

Asthesteelpassesthroughthelastrollers,hotwaterissprayedoverit,formingabluishscale.abluishscale淡蓝色的氧化层Thissteelisfairlyuniforminqualityandisusedformanydifferentkindsofparts.uniforma.均匀

Hot-rolledbarsofthebestqualityareusedtoproducecold-finishedsteels.cold-finishedsteels冷精轧钢

Asthesteelpassesthrought42

Cold-finishedsteelsareusedwhengreataccuracy,bettersurfacefinish,andcertainmechanicalpropertiesareneeded.surfacefinish表面光洁度Themostcommonresultsinwhatiscalledcold-workedsteel.

themostcommon(way):最常见的方法resultsin:导致,引起,产生whatiscalledcold-workedsteel:所谓的冷作钢

Cold-finishedsteelsareuse43

Afterthescalefromthehot-rolledbarsisremoved,oneoftwotechniquesisemployed.(1)Thebarsarecold-drawn,thatis,drawnthroughdiesa

fewthousandths

smallerthantheoriginalbar.cold-drawn：冷拔die：拉模(2)Thesteeliscold-rolled,thatis,rolledcoldtotheexactsize.cold-rolled:冷轧

Afterthescalefromthehot-44

Drillrodisagradeofhigh-carbontoolsteelorhigh-speedsteel.

drillrod：钻杆agradeof：一种Itisfinishedbygrindingandpolishingsothattheoutsideissmoothandveryaccurateinsize.

it:指drillrodfinish:v.精加工n.光洁度Youcanidentifydrillrodbyitsshinysurface,whichismuchsmootherthananyoftheothersteelsusedintheshop.identify……by….通过(用)……来识别shop:车间Lesson2MetalsandFerrousMetals

Drillrodisagradeofhigh-45Drill-rodbarsaregenerallymadein3-ftlengthsandcome

inround,hexagonal,andsquareshapes.Castironisusedfortheheavypartsofmanymachines.Castironislowincostandwearswell.Itisverybrittle,however,andcannotbehammeredorformed.hammeredorformed.锻压成形Thebasickindsofcastironarewhiteiron,grayiron,andmalleableiron.Drill-rodbarsaregenerallym46Malleableironisaparticularkindofcastiron,mademoremalleablebyanannealingprocedure.anannealingprocedure退火工序Malleable-ironcastingsarenotsobrittleorhard.Theycanstandagreatdealhammering.Manyplumbingfixturesaremadeofmalleableiron.plumbingfixtures:管接头Nodularironisakindofcastironthatisevenbetterforwithstandingshocks,blows,andjerks.nodulariron球墨铸铁Malleableironisaparticular47Lesson3Gearsspur(gears)andhelicalgears直齿轮与斜齿轮Agearhavingtoothelements

thatarestraightandparalleltoitsaxisisknownasaspurgear.Aspurpaircanbeusedtoconnectparallelshaftsonly.Parallelshaft,however,canalsobeconnectedbygearsofanothertype,andaspurgearcanbematedwithagearofadifferenttype(Fig.3-1).mate,mesh:啮合Topreventjammingasaresultofthermalexpansion,toaidlubrication,andtocompensateforunavoidableinaccuraciesinmanufacture,allpower-transmittinggearsmusthavebacklash.

power-transmittinggears：动力传动齿轮Lesson3Gearsspur(gears)a48Thismeansthatonthepitchcirclesofamatingpair,thespacewidthonthepinionmustbeslightlygreaterthanthetooththicknessonthegear,andviceversa.amatingpair：一对啮合齿轮viceversa：反之亦然Oninstrumentgears,backlashcanbeeliminatedbyusingagearsplitdownitsmiddle,onehalfbeingratablerelativetotheother.eliminate：消除split：裂开relativeto：相对于Aspringforcesthesplitgearteethtooccupythefullwidthofthepinionspace.Thismeansthatonthepitch49Helicalgearshavecertainadvantages;forexample,whenconnectingparallelshaftstheyhaveahigherloadcarryingcapacitythanspurgearswiththesametoothnumbersandcutwiththesamecutter.withthesametoothnumbersspurgearscutwiththesamecutter.Becauseoftheoverlappingactionoftheteeth,theyaresmootherinactionandcanoperateathigherpitch-linevelocitiesthanspurgears.

theoverlappingaction:交错重叠作用at……velocities:以….的速度Sincetheteethareinclinedtotheaxisofrotation,helicalgearscreateanaxialthrust.beinclinedto:向…..倾斜Helicalgearshavecertainadv50Ifusedsingly,thisthrustmustbeabsorbedintheshaftbearings.Ifusedsingly:ifthesinglehelicalgearisused,absorb:吸收承受Thethrustproblemcanbeovercomebycuttingtwosetsofopposedhelicalteethonthesameblank.twosetsofopposedhelicalteethonthesameblank.在同一个坯件上切削两组相反的斜齿Dependingonthemethodofmanufacture,thegearmaybeofthecontinuous-toothherringbonevarietyoradouble-helicalgearwithaspacebetweenthetwohalvestopermitthecuttingtooltorunout.

continuous-toothherringbonevariety:连续人字形adouble-helicalgear:双斜齿轮Ifusedsingly,thisthrustmu51Double-helicalgearsarewellsuitedfortheefficienttransmissionofpowerathighspeeds.Helicalgearscanalsobeusedtoconnectnonparallel,non-intersectingshaftsatanyangletooneanother.Ninetydegreesisthecommonestangleatwhichsuchgearsareused.最常用的角度为90·Double-helicalgearsarewell52wormandwormgears蜗杆蜗轮Inordertoachievelinecontactandimprovetheloadcarryingcapacityofthecrossed-axishelicalgears,thegearcanbemadetocurvepartiallyaroundthepinion,insomewhatthesamewaythatanutenvelopsascrew.

为了使交叉轴斜齿轮获得线接触和提高承载能力,可以把大齿轮作成部分绕小齿轮弯曲,就象螺母套在螺杆上一样.Theresultwouldbeacylindricalwormandgear.

结果就形成一个柱形蜗杆和蜗轮wormandwormgears蜗杆蜗轮53Wormgearsprovidethesimplestmeansofobtaininglargeratiosinasinglepair.

means:方法,手段largeratiosinasinglepair一对大速比齿轮Theyareusuallylessefficientthanparallel-shaftgears,however,becauseofanadditionalslidingmovementalongtheteeth.

anadditionalslidingmovement附加滑动Becauseoftheirsimilarity,theefficiencyofawormandgeardependsonthesamefactorsastheefficiencyofascrew.Wormgearsprovidethesimples54Single-threadswormsoflargediameterhavesmallleadanglesandlowefficiencies.

single-threadsworm单头蜗杆multiple-threadworm多头蜗杆leadangle导角Fortransmittingrotarymotionandtorquearoundcorners,bevelgearsarecommonlyused.….transmittingrotarymotionandtorquearoundcorners…传递旋转运动以及绕着一个角度传递扭距….Single-threadswormsoflarge55Theconnectedshafts,whoseaxeswouldintersectifextended,areusuallybutnotnecessarilyatrightanglestooneanother.

axis(单数),axes(复数)notnecessarily不一定tooneanother,totheother相互Whenadaptedforshaftsthatdonotintersect,spiralbevelgearsarecalledhypoidgears.

When(spiralbevelgears)adaptedforshafts…..Thepitchsurfacesofthesegearsarenotrollingcones,andtheratiooftheirmeandiametersisnotequaltothespeedratio.Theconnectedshafts,whoseax56Consequently,thepinionmayhavefewteethandbemadeaslargeasnecessarytocarrytheload.Theprofilesoftheteethonbevelgearsarenotinvolutes;theyareofsuchashapethatthetoolsforcutting