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Lesson11、thebranchofscientificanalysis,whichdealswithmotions,time,andforces,iscalledmechanicsandismadeupoftwoparts,staticsanddynamics.Staticsdealswiththeanalysisofstationarysystems,i.e.,thoseinwhichtimeisnotafactor,anddynamicsdealswithsystems,whichchangewithtime.对运动时间和作用力作出科学分析的分支成为力学。他由静力学和动力学两部分组成。静力学对静止系统进行分析，即在其中不考虑时间这个引述，动力学对事件而变化的系统进行分析。2、Anytwosuchforcesactingonabodyconstituteacouple.Thearmofthecoupleistheperpendiculardistancebetweentheirlinesofaction,andtheplaneofthecoupleistheplanecontainingthetwolinesofaction.作用在一个刚体上的两个这样的的里构成一个力偶。力偶臂是这两个条作用线之间的垂直距离，力偶面是包含着两条作用线的平面。3、Mechanicsdealwithtwokindsofquantities:scalarsandvectors.Scalarquantitiesarethosewithwhichamagnitudealoneisassociated.Examplesofscalarquantitiesinmechanicsaretime,volume,density,speed,energy,andmass.Vectorquantities,ontheotherhand,possessdirectionaswellasmagnitude.Examplesofvectorsaredisplacement,velocity,acceleration,force,moment,andmomentum.力学涉及两种类型的量，标量和矢量。标量是那些只有大小的量。在力学中标量的例子有时间、体积、密度、速率、、能量和质量。另一方面，矢量既有大小又有大小又有方向。矢量的例子有位移、速度、加速度、力、力矩、动量。Lesson2（此课后面没翻译，翻译的不太准确谅解）1、Theturningofapartinalatheisanotherexampleofseveralforcesinaction.（asshowninfigure1）车床车削是一些力在起作用的另一个例子。figure1(如图)。2、Ifthisworkpieceisheldbetweenthecentersofthelathe,thecentersexertacompressiveforceagainstthework.如果这个工件在放在车床中心之间,中心车床对工作产生压力。3、Rotarymotionisrequiredtodrillholes,turnpartsinalathe,millsurfaces,ordriveageneratororfanbelt.扶轮运动需要去钻孔，在车床上转换两件,表面,或驱动发电机或风扇皮带4、HarmonicandIntermittentMotion（谐和运动和间歇运动）:Anysimplevibration,suchastheregularback,andforthmovementoftheendofapendulum,issimpleharmonicmotion.Lesson41、Virtuallyallmachinescontainshafts.Themostcommonshapeforshaftsiscircularandthecrosssectioncanbeeithersolidorhollow.实际上，几乎所有的机器中都装有轴。轴的最常见的形状是圆形，其截面可以是实心的，也可以是空心的（空心轴可以减轻重量）。有时也采用矩形轴，例如，螺丝起子的头部.套筒扳手和控制旋钮的杆。2、Ashaftmusthaveadequatetorisonalstrengthtotransmittorqueandnotbeoverstresseditmustalsobetorsionalstiffenoughsothatonemountedcomponentdoesnotdeviateexcessivelyfromitsoriginalangularpositionrelativetoasecondcomponentmountedonthesameshaft.为了在传递扭矩时不发生过载，轴应该有适当的抗扭强度。轴还应该具有足够的抗扭强度，以使在同一轴上的两个传动零件之间的相对转角不会过大。3、Componentssuchasgearsandpulleysaremountedonshaftsbymeansofkey.Thedesignofthekeyandthecorrespondingkeywayintheshaftmustbeproperlyevaluated.Forexample,stressconcentrationsoccurinshaftsduetokeyways,andthematerialremovedtofromthekeywayfurtherweakenstheshaft.齿轮和皮带轮等零件通过键连接在轴上。在键及轴上与之相对应的键槽的设计中，必须进行认真的计算。例如，轴上的键槽会引起应力集中，由于键槽的存在会使轴的横截面积减小，会进一步减弱轴的强度。4、Anotherimportantaspectofshaftdesignisthemethodofdirectlyconnectingoneshafttoanother.Devicessuchasrigidandflexiblecouplingsaccomplishthis.轴的设计工作中的另一个重要方面是一根轴与另一根轴之间的直接连接方法。这是由刚性或者弹性联轴器来实现的。Lesson51、Thetermshaftusuallyreferstoarelativelylongmemberofroundcrosssectionthatrotatesandtransmitspower.Oneormorememberssuchasgears,sprockers,pullys,andcamsareusuallyattachedtotheshaftbymeansofpins,keys,splines,snaprings,andotherdevices.Theselattermembersareamongtheassociatedpartsconsederedinthistext,asatecouplingsanduniversaljoints,whichservetoconnecttheshafttothesourceofpowerorload.2、Itisapparentthatshaftscanbesubjectedtovariouscombinationsofaxial,bending,andtorsionalloads,andthattheseloadsmaybestaticorfluctuating.3、Torsionaldefectioncanaffecttheaccuracyofacamorgeardrivenmechanism.Furthermore,thegreatertheflexibility-eitherlateralortorsional-thelowerthecorrespondingcriticalspeed.4、Agearcanbegrippedaxiallybetweenashoulderontheshaftandaspacer,withtorquebeingtransmittedthroughakeyways.Lesson71、Fastenersaredeviceswhichpermitoneparttobejoinedtoasecondpartand,hence,theyareinvolvedinalmostalldesigns.Theacceptabilityofanyproductdependsnotonlyontheselectedcomponents,butalsoonthemeansbywhichtheyarefastenedtogether.Theprincipalpurposesoffastenersaretoprovidethefollowingdesignfeatures;紧固件是将一个零件与另一个零件进行连接的零件。因此，几乎在所有的设计中都要用到紧固件。人们对于任何产品的满意程度不仅取决于其组成部件，还取决于其连接方式。2、Theimportanceoffastenerscanberealizedwhenreferringroanycomplexproduct,Inthecaseoftheautomobile,thereareliterallythousandsofpartswhicharefastenedtogethertoproducethetotalproduct.Thefailureorlooseningofasinglefastenercouldresultinasimplenuisancesuchasadoorrattleorinaserioussituationsuchasawheelcomingoff.Suchpossibilitiesmustbetakenintoaccountintheselectionofthetypeoffatenerforthespecificapplication.通过任何一个复杂的产品，都可以认识到紧固件在其中的重要性。以汽车为例，它是由数千个零件连接在一起而成为一辆车。一个紧固件的失效或松脱可能会带来像车门嘎嘎响这类小麻烦，也可能造成像车轮脱落这种严重的后果。因此，在为一个特定的用途选择紧固件时，应该考虑到上述各种可能性。Lesson81、Threadedfasternersperformthefunctionoflocating,clamgping,adjusting,andtransmitingforcefromonemachinemembertoanother.Theyarethoroughlystandardizedandgenerallydesignedforuseinmassproductionofmachines.2、Matchingexternalandinternalthreadssothattheyaremaybeassembledisthekeytoallthreadfasteners.3、AparticularSAEgradespecilicationcanbemetbyanumberofdifferentsteels,thusfastermanufacturershavesomelatitudeinselectingthematerialsbestsuitedtotheirspecificproductionfaclities.4、Formoderateloadsandspeedesthecorrectselectionofastandardofthebearingonthebasisofloadratingwillusuallysecuresatisfactoryperformance.对于中等载荷和转速，根据额定负荷选择一个标准轴承，通常都可以保证其具有令人满意的工作性能。5、Thedeflectionofles