机械制造专业英语课后翻译答案

第一单元应力与应变Thatbranchofscientificanalysiswhichmotions,timesandforcesiscalledmechanicsandismadeupoftwoparts,staticsanddynamics.研究位移、时间和力运动乘力是科学分析法的一个分歧，被称作力学，力学由两大部分组成，静力学和动力学。Forexample,iftheforceoperatingonasleevebearingbecomestoohigh,itwillsqueezeouttheoilfilmandcausemetal-to-metalcontact,overheatingandrapidfailureofthebearing.例如：如果止推轴承上的作用力过大的话，会挤出油膜，引起金属和金属之间的相互接触，轴承将过热而迅速失效。Ourintuitiveconceptofforceincludessuchideasasplaceofapplication,direction,andmagnitude,andthesearecalledthecharacteristicsofaforce.力的直观概念包括力的作用点、大小、方向，这些被称为力的三要素。Allbodiesareeitherelasticorplasticandwillbedeformedifacteduponbyforces.Whenthedeformationofsuchbodiesissmall,theyarefrequentlyassumedtoberigid,i.e.,incapableofdeformation,inordertosimplifytheanalysis.所有的物体既可以是弹性的也可以是塑性的，如果受到力的作用就产生变形。当变形很小的时候它们被假设成刚体，也就是不产生变形,以此来简化分析。Therigid-bodyassumptioncannotbeusedininternalstressesandstrainsduetotheappliedforcestobeanalyzed.Thusweconsiderthebodytobecapableofdeforming.刚体假设不能应用于内应力和内应变的分析，所以在实际力的分析时，要考虑物体的形变。Ifalltheforcesactingonaparticlearebalanced,theparticlewilleitherremainatrestorwillcontinuetomoveinastraightlineatauniformvelocity.如果作用在质点上所有的力是平衡的，质点将会保持静止或做做匀速直线运动。第二单元材料的强度与塑性Atensiletestconsistsofslowlypullingasampleofmaterialwithatensileloaduntilitbreaks.Theendsoftensilespecimensareusuallyenlargedtoprovideextraareaforgrip-pingandtoavoidhavingthesamplebreakwhereitisbeinggripped.拉伸试验包括慢慢加载拉伸载荷直到断裂。拉伸试件两端加粗为了提供装夹区域和避免试件断裂。Theusualmannerofconductingthetestistodeformthespecimenataconstantspeed.Forexample,intheuniversaltestingmachines,themotionbetweenthefixedandmovingcrossheadscanbecontrolledataconstantspeed.通常进行试验的方法就是使试件以恒定速度发生变形。例如，在万能拉伸试验机上，固定端和移动的十字滑块之间的变形是以恒定速度进行的。Theloadthatmustbeappliedtoenforcethisdisplacementratevariesasthetestproceeds.ThisloadFmaybedividedbythecross-sectionalareaAtoobtainthestressinthespecimenatanytimeduringthetest.随着实验的进行，用来产生位移的载荷是随位移的变化而变化。在实验中，载荷F除以横截面积A可以得到任意时刻点的应力。HoweveractualmeasurementofΔLispreferablewherethisisfeasible.Stressandstrainbasedontheinitial(undeformed)dimensions,AiandLi,arecalledengineeringstressandstrain.然而，在可行的位置上ΔL的实际测量是更可取的，基于原始尺寸Ai和Li的应力和应变称为工程应力和工程应变。Ductileandbrittlematerialsbehavedifferentlyincompressiontestaswell.Thecompressiontestisconductedonshortcylindricalspecimensplacedbetweenparallelplates.塑性和脆性材料在压缩试验中表现的特性是不相同的。压缩试验是把短圆柱形试件放在两平行平板之间进行的。Thecompressiontestdiagramforthesematerialsretainsthequalitativefeaturesofthetensiontestdiagram.Theultimatecompressivestrengthofabrittlematerialisdeterminedinthesamewayasintension.材料压缩试验图保持了拉伸试验图性能上的特征。脆性材料的最大压缩强度与最大拉伸强度得到的方法相同。第三单元轴设计Virtuallyallmachinescontainshafts.Themostcommonshapeforshaftsiscircularandthecrosssectioncanbeeithersolidorhollow(hollowshaftscanresultinweightsavings).几乎所有的机器都有轴，最常用的外形是圆形的，横截面是空心的或实心的圆形截面（空心轴可以减少重量）。Ashaftmusthaveadequatetorsionalstrengthtotransmittorqueandnotbeoverstressed.Itmustalsobetorsionallystillenoughsothatonemountedcomponentdoesnotdeviateexcessivelyfromitsoriginalangularpositionrelativetoasecondcomponentmountedonthesameshaft.一个轴必须有足够的扭转强度来传递扭矩而不会破坏，同样也必须有足够的扭转刚度，这样安装轴就不能过度偏离相对于安装在同一轴上第二个零件的原始位置。Shaftsaremountedonbearingsandtransmitpowerthroughsuchdevicesasgears,pulleys,camsandclutches.Thesedevicesintroduceforceswhichattempttobendtheshaft;hence,theshaftmustberigidenoughtopreventoverloadingofthesupportingbearings.轴安装在轴承上通过齿轮，滑轮，凸轮和离合器这些装置传递力。这些装置可以产生使轴弯曲的力，所以轴必修有足够的刚性防止支撑轴承的过载。Inaddition,theshaftmustbeabletosustainacombinationofbendingandtorsionandbending.另外，轴必须能承载弯扭组合的载荷，因此，这样就必须考虑弯扭组合的等效载荷。Componentssuchasgearsandpulleysaremountedonshaftsbymeansofkey.Thedesignofthekeyandthecorrespondingkeywayintheshaftmustbeproperlyevaluated.齿轮和滑轮构件是用键的方式连接在轴上的，键和对应的键槽的设计必须进行估算。Anotherimportantaspectofshaftdesignisthemethodofdirectlyconnectingoneshafttoanother.Thisisaccomplishedbydevicessuchasrigidandflexiblecouplings.轴设计的另一个重要方面是直接连接两轴，通过刚性和柔性的联轴器装置来实现。第四单元SpurGears齿轮Pressureanglesforspurgearsareusually14.5or20degrees,althoughothervaluescanbeused.Meshinggearsmusthavethesamepressureangles.直齿轮的压力角通常为14.5°或20°，另外也使用其它的角度，啮合齿轮必须具有相同的压力角。Theshapeofthespacebetweengearteethonthegearaswellastoothmodule,somostgearmanufacturingmethodsgeneratethetoothflankinsteadofforming.齿轮轮齿之间齿槽的形状是复杂的，并且随着齿的数目和模数变化而变化，因此大多数齿轮的加工方法是展成齿腹齿廓而不是齿形成形加工。Wormgearsareusedwherehighratiosaredesiredandwheretheshaftsarenonintersectingandatrightangles.蜗杆蜗轮应用于传动比大而且两轴不相交但相互垂直的情况下。Ithasthegreatadvantagethatthecuttingtoolisasimplerackwith(nearly)straightsidedteethwhichcaneasilybegroundaccurately.这种方法有很大的优势，切削工具是一个简单的带有直齿边的齿条Modernshaperscuttingcargearscanrunat2000cuttingperminute.Theshapeofthecutterisroughlythesameasaninvolutegearbutthetipsoftheteetharerounded.现代切削汽车的成型器齿轮转速可达每分钟2000转，齿刀形状与渐开线大致相同，但齿顶是圆形的。Bevelgearsareoftenusedwhentwoshaftsareatrightanglestoeachotherandtheircenterlineextensionsintersect;however,somebevelgearsareatanglesotherthan90degrees.圆锥齿轮一般应用于相互垂直的两轴或两个中心线延长线的相交轴中，也可用于不垂直的两轴中。第五单元cams凸轮Thepurposeofanycamistoproduceadisplacementofitsfollower;asecondaryfollowerisoftenusedtoproduceadditionaldisplacementinanotherlocation.使用凸轮的目的是使从动件产生位移，次级从动