教学材料《机电专业英语》-Part1

PartoneLesson8LathesandLatheOperationsLesson9MetalFormingLesson10TheWeldingandWeldingArcLesson11InjectionMoldingMachines上一页返回Lesson1TheEvolutionofMechanicalEngineeringSectionⅠTextMechanicalEngineeringisanengineeringdisciplinethatinvolvestheapplicationofprinciplesofphysicsandchemistryforanalysis，design，manufacturingandmaintenanceofvarioussystems.MechanicalEngineeringisoneoftheoldestandbroadestengineeringdisciplines.Itrequiresasolidunderstandingofcoreconceptsincludingmechanics，kinematics，thermodynamics，fluidmechanics，andenergy.Mechanicalengineersusethecoreprinciplesaswellasotherknowledgeinthefieldtodesignandanalyzemanufacturingplants，industrialequipmentandmachinery，heatingandcoolingsystems，motorvehicles，aircraft，watercraft，robots，medicaldevicesandmore.下一页返回Lesson1TheEvolutionofMechanicalEngineeringHistoryandDevelopmentApplicationsofmechanicalengineeringarefoundintherecordsofmanyancientandmedievalsocietiesthroughouttheglobe.InancientGreece，theworksofArchimedes(287BC一212BC)andHeronofAlexandria(10一70AD)deeplyinfluencedmechanicsintheWesterntradition.InChina，ZhangHeng(78一139AD)improvedawaterclockandinventedaseismometer，andMaJun(200一265AD)inventedachariotwithdifferentialgears.下一页上一页返回Lesson1TheEvolutionofMechanicalEngineeringDuringtheyearsfromthe7thtothe15thcentury，therewereremarkablecontributionsfromArabiansinthefieldofmechanicaltechnology，A1Jaziri，whowasoneofthem，wrotehisfamous“BookofKnowledgeofIngeniousMechanicalDevices”in1206inwhichhepresentedmanymechanicaldesigns.Heisalsoconsideredtobetheinventorofsuchmechanicaldevicesthatnowformtheverybasicsofmechanisms，suchascrankandcamshafts.下一页上一页返回Lesson1TheEvolutionofMechanicalEngineeringDuringtheearly19thcenturyinEnglandandScotland，thedevelopmentofmachinetoolsledmechanicalengineeringtodevelopasaseparatefieldwithinengineering，providingmanufacturingmachinesandtheenginestopowerthem.ThefirstBritishprofessionalsocietyofmechanicalengineerswasformedin1847，thirtyyearsaftercivilengineersformedthefirstsuchprofessionalsociety.IntheUnitedStates，theAmericanSocietyofMechanicalEngineers(ASME)wasformedin1880，becomingthethirdsuchprofessionalengineeringsociety，aftertheAmericanSocietyofCivilEngineers(1852)andtheAmericanInstituteofMiningEngineers(1871).ThefirstschoolintheUnitedStatestoofferanengineeringeducationwastheUnitedStatesMilitaryAcademyin1817.Educationinmechanicalengineeringhashistoricallybeenbasedonastrongfoundationinmathematicsandscience.下一页上一页返回Lesson1TheEvolutionofMechanicalEngineeringThefieldofmechanicalengineeringisconsideredamongthebroadestofengineeringdisciplines.Theworkofmechanicalengineeringrangesfromthedepthsoftheoceantoouterspace.ModernToolsManymechanicalengineeringcompanies，especiallythoseinindustrializednations，havebeguntoincorporatecomputer-aidedengineering(CAE)programsintotheirexistingdesignandanalysisprocesses，including2Dand3Dsolidmodelingcomputer-aideddesign(CAD).Thismethodhasmanybenefits，includingeasierandmoreexhaustivevisualizationofproducts，theabilitytocreatevirtualassembliesofparts，andtheeaseofuseindesigningmatinginterfacesandtolerances.OtherCAEprogramscommonlyusedbymechanicalengineersincludeproductlifecyclemanagement(PLM)toolsandanalysistoolsusedtoperformcomplex下一页上一页返回Lesson1TheEvolutionofMechanicalEngineeringsimulations.Analysistoolsmaybeusedtopredictproductresponsetoexpectedloads，includingfatiguelifeandmanufacturability.Thesetoolsincludefiniteelementanalysis(FEA)，computationalfluiddynamics(CFD)，andcomputer-aidedmanufacturing(CAM).下一页上一页返回Lesson1TheEvolutionofMechanicalEngineeringAsmechanicalengineeringbeginstomergewithotherdisciplines，asseeninmechatronics，multidisciplinarydesignoptimization(MDO)isbeingusedwithotherCAEprogramstoautomateandimprovetheiterativedesignprocess.MDOtoolswraparoundexistingCAEprocesses，allowingproductevaluationtocontinueevenaftertheanalystgoeshomefortheday.Theyalsoutilizesophisticatedoptimizationalgorithmstomoreintelligentlyexplorepossibledesigns，oftenfindingbetter，innovativesolutionstodifficultmultidisciplinarydesignproblems.下一页上一页返回Lesson1TheEvolutionofMechanicalEngineeringSectionIINewWordsandPhrasesdisciplinemechanicskinematicsthermodynamicsfluidmechanicsmotorvehicleswatercraftrobotmedievalsocietyseismometerchariot下一页上一页返回Lesson1TheEvolutionofMechanicalEngineeringdifferentialgearchariotwithdifferentialgearsArabianingeniouspresentcrankcamshaftprovidemanufactureprofessionalsocietycivilengineerexhaustivevisualization下一页上一页返回Lesson1TheEvolutionofMechanicalEngineeringvirtualmatinginterfacestolerancesfatiguefatiguelifesimulationresponsemanufacturabilityproductlifecyclemanagementfinitefiniteelementanalysis(FEA)computer-aidedmanufacturing(CAM)merge下一页上一页返回Lesson1TheEvolutionofMechanicalEngineeringmechatronicsmultidisciplinaryoptimizationmultidisciplinarydesignoptimization(MDO)computationalfluiddynamics(CFD)iterativeevaluationsophisticatedwrapalgorithminovativeintelligent下一页上一页返回Lesson1TheEvolutionofMechanicalEngineeringSectionIIINotestoComplexSentences[1」Heisalsoconsideredtobetheinventorofsuchmechanicaldevicesthatnowformtheverybasicofmechanisms,suchascrankandcamshafts.

他还被认为是很多机械的发明者，这些机械演变成当今最基本的机构，如曲轴和凸轮轴。

thatnowformtheverybasicof…是定语从句，修饰devices.下一页上一页返回Lesson1TheEvolutionofMechanicalEngineering[2」…thedevelopmentofmachinetoolsledmechanicalengineeringtodevelopasaseparatefieldwithinengineering，providingmanufacturingmachinesandtheenginestopowerthem.……机器工具的发展导致机械工程从其他工程领域分离出来，专门提供机器和发动机制造。[3」Thefieldofmechanicalengineeringisconsideredamongthebroadestofengineeringdisciplines.

机械工程被认为是范围最广的学科之一。[4」Theworkofmechanicalengineeringrangesfromthedepthsoftheoceantoouterspace.

机械工程所涉及的领域遍及深海至外层空间下一页上一页返回Lesson1TheEvolutionofMechanicalEngineering[5」MDOtoolswraparoundexistingCAEprocesses，allowingproductevaluationtocontinueevenaftertheanalystgoeshomefortheday.MDO工具结合已有的CAE程序，能够让产品评估过程不间断进行，即使分析员下班回家。[6」Theyalsoutilizesophisticatedoptimizationalgorithmstomoreintelligentlyexplorepossibledesigns…

它们还应用复杂的优化算法来寻求可能的设计方案上一页返回Lesson2FundamentalsofMachineDesign

SectionⅠTextDesignisessentiallyadecision-makingprocess.Ifwehaveaproblem，weneedtodesignasolution.Inotherwords，todesignistoformulateaplantosatisfyaparticularneedandtocreatesomethingwithaphysicalreality.Abaddecisionleadstoabaddesignandabadproduct.Therearemanyfactorstobeconsideredwhileattackingadesignproblem.Inmanycasesthisisacommonsenseapproachtosolvingaproblem.Someofthesefactorsareasfollows.下一页返回Lesson2FundamentalsofMachineDesign

Whatdeviceormechanismtobeused一Thisisbestjudgedbyunderstandingtheproblemthoroughly.Sometimesaparticularfunctioncanbeachievedbyanumberofmeansorbyusingdifferentmechanismsandthedesignerhastodecidewhichoneisthemosteffectiveunderthecircumstances.Material一Thisisaveryimportantaspectofanydesign.Awrongchoiceofmaterialmayleadtofailure，overorundersizedproductorexpensiveitems.Thechoiceofmaterialsisthusdependentonsuitablepropertiesofthematerialforeachcomponent，theirsuitabilityoffabricationormanufactureandthecost.下一页上一页返回Lesson2FundamentalsofMachineDesign

Load一Theexternalloadscauseinternalstressesintheelementsandthesestressesmustbedeterminedaccuratelysincethesewillbeusedindeterminingthecomponentsize.Size，shape，spacerequirementsandweight一Preliminaryanalysiswouldgiveanapproximatesize.Butifastandardelementistobechosen，thenextlargersizemustbetaken.Shapesofstandardelementsareknownbutfornon-standardelement，shapesandspacerequirementsmustdependonavailablespaceinaparticularmachineassembly.Ascalelayoutdrawingisoftenusefultoarriveataninitialshapeandsize.Weightisimportantdependingonapplication.Manufacture一Caremustalwaysbetakentoensurethatthedesignedelementsmaybemanufacturedwitheasewithintheavailablefacilitiesandatlowcost.下一页上一页返回Lesson2FundamentalsofMachineDesign

Howwillitoperate一Inthefinalstageofthedesign，adesignermustensurethatthemachinemaybeoperatedwithease.Inmanypoweroperatedmachines，itissimplyamatterofpressingaknoborswitchtostartthemachine.Howeverinmanyothercases，asequenceofoperationsistobespecified.Thissequencemustnotbecomplicatedandtheoperationsshouldnotrequireexcessiveforce.下一页上一页返回Lesson2FundamentalsofMachineDesign

Reliabilityandsafety一Reliabilityisanimportantfactorinmachineshouldworkeffectivelyandreliably.Theprobabilitywillnotfailinuseiscalledreliability.Reliabilityliesbetween0<R<1.Toensurethiseverydetailshouldbeexamined.Possibleoverloading，wearofelements，excessiveheatgenerationandothersuchdetrimentalfactorsmustbeavoided.Thereisnosingleanswerforthisbutanoverallsafedesignapproachandcareateverystageofdesignwouldresultinareliablemachine.Safetyhasbecomeamatterofparamountimportancethesedaysindesign.Machinesmustbedesignedtoservemankind，nottoharmit.Industrialregulationsensurethatthemanufacturerisliableforanydamageorharmarisingoutofadefectiveproduct.下一页上一页返回Lesson2FundamentalsofMachineDesign

Maintenance,costandaestheticsMaintenanceandsafetyareofteninterlinked.Goodmaintenanceensuresgoodrunningconditionofmachinery.Oftenaregularmaintenancescheduleismaintainedandathoroughcheckupofmovingandloadedpartsiscarriedouttoavoidcatastrophicfailures.Lowfrictionandwearismaintainedbyproperlubrication.Thisisamajoraspectofdesignsincewherevertherearemovingparts，frictionandwearareinevitable.Highfrictionleadstoincreasedlossofenergy.Wearofmachinepartsleadstolossofmaterialandprematurefailure.下一页上一页返回Lesson2FundamentalsofMachineDesign

CostandaestheticsareessentialconsiderationstothechoiceofmaterialswhichinturndependsonAlthoughinmanycasesaestheticconsiderationsareproductdesign.Costisessentiallyrelatedstressesdevelopedinagivencondition.notessentialaspectsofmachinedesign，ergonomicaspectsmustbetakenintoconsiderations.SectionIINewWordsandPhrasesdecision-makingformulatethoroughlycircumstanceundersized下一页上一页返回Lesson2FundamentalsofMachineDesign

componentexternalinternalstressapproximatestandardelementscalescalelayoutdrawingcommonsenseapproachwitheasefacilityknob下一页上一页返回Lesson2FundamentalsofMachineDesign

sequenceexcessivereliabilityprobabilityoverloadingexcessiveheatpreliminaryassemblyparamountdetrimentalindustrialregulations下一页上一页返回Lesson2FundamentalsofMachineDesign

liabledefectiveaestheticsmaintenancecatastrophicfrictionandwearlubricationcheckupinevitableprematureergonomics下一页上一页返回Lesson2FundamentalsofMachineDesign

SectionIIINotestoComplexSentences[1」Inmanycasesthisisacommonsenseapproachtosolvingaproblem.许多场合下，通过常识就可解决问题[2」Awrongchoiceofmaterialmayleadtofailure，overorundersizedproductorexpensiveitems.选材错误会导致产品失败、尺寸过大或过小及成本过高。[3」Butifastandardelementistobechosen，thenextlargersizemustbetaken.

如果选用标准件，就要取稍大一点的尺寸。[4」Ascalelayoutdrawingisoftenusefultoarriveataninitialshapeandsize.

按比例画出一张布置图往往对形成初步的形状和尺寸很有帮助。下一页上一页返回Lesson2FundamentalsofMachineDesign

[5」…itissimplyamatterofpressingaknoborswitchtostartthemachine.……只不过是按一下旋钮开机那么简单的事情[6」Industrialregulationsensurethatthemanufacturerisliableforanydamageorharmarisingoutofadefectiveproduct.

工业法规确保制造商对有缺陷产品造成的任何损害和伤害负责[7」Costisessentiallyrelatedtothechoiceofmaterialswhichinturndependsonthestressesdevelopedinagivencondition.

成本最终取决于材料的选择，而材料的选择又取决于给定条件下的应力状况上一页返回Lesson3EngineeringMaterialsSectionⅠTextIntroductionCommonengineeringmaterialsarenormallyclassifiedasmetalsandnonmetals.Metalsmayconvenientlybedividedintoferrousandnon-ferrousmetals.Importantferrousmetalsforthepresentpurposeare(i)Castiron.(ii)Wroughtiron.(iii)Steel.下一页返回Lesson3EngineeringMaterialsSomeoftheimportantnon-ferrousmetalsusedinengineeringdesignare(i)Lightmetalgroupsuchasaluminiumanditsalloys.(ii)Copperbasedalloyssuchasbrass(Cu-Zn)，bronze(Cu-Sn).(iii)Whitemetalgroupsuchasnickel，silver，zinc，etc.FerrousMaterialsCastiron:Itisanalloyofiron，carbonandsiliconanditishardandbrittle.Carboncontentmaybewithin1.7%to3%andcarbonmaybepresentasfreecarbonorironcarbideFe3C.Wroughtiron:Thisisaverypureironwheretheironcontentisoftheorderof99.5%.Itisproducedbyre-meltingpigironandsomesmallamountofsilicon，sulphur，orphosphorusmaybepresent.下一页上一页返回Lesson3EngineeringMaterialsItistough，malleableandductileandcaneasilybeforgedorwelded.Itcannothowevertakesuddenshock.Chains，cranehooks，railwaycouplingsandsuchothercomponentsmaybemadeofthisiron.Steel:Thisisbyfarthemostimportantengineeringmaterialandthereisanenormousvarietyofsteeltomeetthewidevarietyofengineeringrequirements.Steelisbasicallyanalloyofironandcarboninwhichthecarboncontentcanbelessthan1.7%andcarbonispresentintheformofironcarbidetoimparthardnessandstrength.Twomaincategoriesofsteelareplaincarbonsteelandalloysteel.(i)Plaincarbonsteel:Thepropertiesofplaincarbonpercentagesandotheralloyingelementsarenotusuallypresentsteeldependmainly0.5%onthecarboninmorethanto1%suchas0.5%or1%Mn,etc.下一页上一页返回Lesson3EngineeringMaterials(ii)Alloysteel:Thesearesteelsinwhichelementsotherthancarbonareaddedinsufficientquantitiestoimpartdesiredproperties，suchaswearresistance，corrosionresistance，electricormagneticproperties.Chiefalloyingelementsaddedareusuallynickelforstrengthandtoughness，chromiumforhardnessandstrength，tungstenforhardnessatelevatedtemperature，vanadiumfortensilestrength，manganeseforhighstrengthinhotrolledandheattreatedcondition，siliconforhighelasticlimit.Non-ferrousMetalsMetalscontainingelementsotherthanironastheirchiefconstituentsareusuallyreferredtoasnon-ferrousmetals.Thereisawidevarietyofnon-metalsinpractice.However,onlyafewexemplaryonesarediscussedbelow.下一页上一页返回Lesson3EngineeringMaterialsAluminium:ThisisthewhitemetalproducedfromAlumina.InitspurestateitisweakandsoftbutadditionofsmallamountsofCu，Mn，SiandMagnesiummakesithardandstrong.Itisalsocorrosionresistant，lowweightandnon-toxic.Magnalium:Thisisanaluminiumalloywith2%to10%magnesium.Italsocontains1.75%Cu.Duetoitslightweightandgoodstrengthitisusedforaircraftandautomobilecomponents.Copperalloys:Copperisoneofthemostwidelyusednon-ferrousmetalsinindustry.Itissoft,malleableandductileandisagoodconductorofheatandelectricity.Thefollowingtwoimportantcopperalloysarewidelyusedinpractice.下一页上一页返回Lesson3EngineeringMaterialsNon-metalsNon-metallicmaterialsarealsousedinengineeringpracticeduetoprincipallytheirlowcost，flexibilityandresistancetoheatandelectricity.Thoughtherearemanysuitablenon-metals，plasticsisthemostimportantfromdesignpointofview.Theyaresyntheticmaterialswhichcanbemouldedintodesiredshapesunderpressurewithorwithoutapplicationofheat.Theyarenowextensivelyusedinvariousindustrialapplicationsfortheircorrosionresistance，dimensionalstabilityandrelativelylowcost.下一页上一页返回Lesson3EngineeringMaterialsSectionIINewWordsandPhrasesclassifyconvenientlyferrouscastironwroughtwroughtironalloynickelzinc下一页上一页返回Lesson3EngineeringMaterialssiliconbrittlecarbidepigironsulphurphosphorusmalleablecranehookcouplingductile下一页上一页返回Lesson3EngineeringMaterialsforgebyfarhardnessandstrengthcategoryplaincarbonsteelimpartcorrosionresistancehotrollelasticlimittoughnesstensile下一页上一页返回Lesson3EngineeringMaterialsexemplaryconstituenttungstenchromiumvanadiummanganesenon-toxicbinaryalloybrassbearingbronze下一页上一页返回Lesson3EngineeringMaterialsboilerfittingsoxidizeglandflexibilitysyntheticmould，moldextensivelydimensionalstability下一页上一页返回Lesson3EngineeringMaterialsSectionIIINotestoComplexSentences[1」Thisisaverypureironwheretheironcontentisoftheorderof99.5%

这是一种非常纯的铁，其中铁的含量约占99.5%[2」Itisproducedbyre-meltingpigironandsomesmallamountofsilicon，sulphur,orphosphorusmaybepresent.

它是由生铁重新熔化而成，其中含有少量硅和硫，或者还有少量磷[3」Thepropertiesofplaincarbonsteeldependmainlyonthecarbonpercentagesandotheralloyingelementsarenotusuallypresentinmorethan0.5%to1%suchas0.5%Siorl%Mn，etc.

纯碳钢的性能主要取决于含碳百分比，其他合金元素通常不到

0.5%~1%，例如，0.5%的硅或者1%的锰下一页上一页返回Lesson3EngineeringMaterials[4」Thesearesteelsinwhichelementsotherthancarbonareaddedinsufficientquantitiestoimpartdesiredproperties，suchaswearresistance，corrosionresistance，electricormagneticproperties.

这种钢添加了除碳以外的足够数量的其他元素，用以提供期望的性能，比如抗磨损性、抗腐蚀性、电磁特性等。[5」Itprovideshardnessbuttincontentalsooxidizesresultinginbrittleness.

它提供硬度，但锡也会氧化从而导致脆性上一页返回Lesson4BasicConceptsinMechanicsSectionⅠTextIntroductionInitsoriginalsense，mechanicsreferstothestudyofthebehaviorofsystemsundertheactionofforces.Staticsdealswithcaseswheretheforceseitherproducenomotionorthemotionisnotofinterest.Dynamicsdealsproperlywithmotionsunderforces.Mechanicsissubdividedaccordingtothetypesofsystemsandphenomenainvolved.Animportantdistinctionisbasedonthesireofthesystem.ThosesystemsarelargeenoughandcanbeadequatelydescribedbytheNewtonianlawofclassicalmechanics.Inthiscategory，forexample，arecelestialmechanics，thestudyofthemotionsofplanets，stars，andotherheavenlybodies，andfluidmechanics，whichtreatsliquidsandgasesonamacroscopicscale.下一页返回Lesson4BasicConceptsinMechanicsFluidmechanicsisapartofalargerfieldcalledcontinuummechanics，involvinganyessentiallycontinuousdistributionofmatter,whetherrigid，elastic，plastic，orfluid.Ontheotherhand，thebehaviorofmicroscopicsystemssuchasmolecules，atoms，andnucleicanbeinterpretedonlybytheconceptsandmathematicalmethodsofquantummechanics.Fromitsinception，quantummechanicshadtwoapparentlydifferentmathematicalforms:thewavemechanicsofE.Schrodinger,whichemphasizesthespatialprobabilitydistributionsinthequantumstates，andthematrixmechanicsofW.Heisenberg，whichemphasizesthetransitionsbetweenstates.Thesearenowknowntobeequivalent.下一页上一页返回Lesson4BasicConceptsinMechanicsMechanicsmayalsobeclassifiedasnonrelativisticandrelativisticmechanics，thelatterapplyingtosystemswithmaterialvelocitiescomparabletothevelocityoflight.Thisdistinctionpertainstobothclassicalandquantummechanics.Finally，statisticalmechanicsusesthemethodsofstatisticsforbothclassicalandquantumsystemscontainingverylargenumberofsimilarsubsystemstoobtaintheirlarge-scaleproperties.BasicConceptsinMechanicsThatbranchofscientificanalysiswhichdealswithmotions，times，andforcesiscalledmechanicsandismadeupoftwoparts:staticsanddynamics.Staticsdealswiththeanalysisofstationarysystems，i.e.，thoseinwhichtimeisnotafactor,anddynamicsdealswithsystemswhichchangewithtime.下一页上一页返回Lesson4BasicConceptsinMechanicsForcesaretransmittedintomachinemembersthroughmatingsurfaces，e.g.，fromageartoashaftorfromonegearthroughmeshingteethtoanothergear，fromarodthroughabearingtoalever,fromaV-belttoapulley，orfromacamtoafollower.Itisnecessarytoknowthemagnitudesoftheseforcesforavarietyofreasons.Thedistributionoftheforcesattheboundariesormatingsurfacesmustbereasonable，andtheirintensitiesmustbewithintheworkinglimitsofthematerialscomposingthesurfaces.Forexample，iftheforceoperatingonasleevebearingbecomestoohigh，itwillsqueezeouttheoilfilmandcausemetal-to-metalcontact,overheating，andrapidfailureofthebearing.Iftheforcesbetweengearteetharetoolarge，theoilfilmmaybesqueezedoutfrombetweenthem.Thiscouldresultinflakingandspallingofthemetal，noise，roughmotion，andeventualfailure.Inthestudyofdynamicsweareprincipallyinterestedindeterminingthemagnitude，directionandlocationoftheforces.下一页上一页返回Lesson4BasicConceptsinMechanicsSomeofthetermsusedinthisphaseofourstudiesaredefinedbelow.ForceMutter.Mass.InertiaWeight.Particle.RigidBody.Deformationbody下一页上一页返回Lesson4BasicConceptsinMechanicsNewton'slaws.Newton'sthreelawsareLawl:Ifalltheforcesactingonaparticlearebalanced，theparticlewilleitherremainatrestorwillcontinuetomoveinastraightlineatauniformvelocity.Law2:Iftheforcesactingonaparticlearenotbalanced，theparticlewillexperienceanaccelerationproportionaltotheresultantforceandinthedirectionoftheresultantforce.Law3:Whentwoparticlesreact，apairofinteractingforcescomesintoexistence;theseforceshavethesamemagnitudesandoppositesenses，andtheyactalongthestraightlinecommontothetwoparticles.下一页上一页返回Lesson4BasicConceptsinMechanicsMechanicsdealswithtwokindsofquantities-scalarsandvectors.Scalarquantitiesarethosewithwhichamagnitudealoneisassociated.Examplesofscalarquantitiesinmechanicsaretime，volume，density，speed，energy，andmass.Vectorquantities，ontheotherhand，possessdirectionaswellasmagnitude.Examplesofvectorsaredisplacement，velocity，acceleration，force，moment，andmomentum.下一页上一页返回Lesson4BasicConceptsinMechanicsSectionIINewWordsandPhrasesstaticsdynamicsspatialmicroscopicmacroscopicmcept<onemphasizetransitionrelativistic下一页上一页返回Lesson4BasicConceptsinMechanicspertainsurmiseneverthelessinherentquotationpertinentstatisticssleeveinertiamatingmagnitude下一页上一页返回Lesson4BasicConceptsinMechanicsmeshflakespallpulleyintuitivedeformationelasticclassicalmechanicsheavenlybodyfluidmechanics下一页上一页返回Lesson4BasicConceptsinMechanicsquantummechanicswavemechanicscontinuummechanicsrelativisticmechanicsmatrixmechanicsstatisticalmechanicsmaterialvelocitymatingsleevesurfacebearing下一页上一页返回Lesson4BasicConceptsinMechanicsSectionIIINotestoComplexSentences[1」Mechanicsissubdividedaccordingtothetypesofsystemsandphenomenainvolved.

根据系统类型和涉及的现象，力学被再次细分[2」Inthiscategory，forexample，arecelestialmechanics，thestudyofthemotionsofplanets，stars，andotherheavenlybodies，andfluidmechanics，whichtreatsliquidsandgasesonamacroscopicscale.[3」Thatbranchofscientificanalysiswhichdealswithmotions，timesandforcesiscalledmechanicsandismadeupoftwoparts:staticsanddynamics.

研究运动、时间和力的科学分支称为力学，它由两部分组成:静力学与动力学。下一页上一页返回Lesson4BasicConceptsinMechanics[4」Law2:IftheforcesactingonaparticlearenotbalancedTheparticlewillexperienceanaccelerationproportionaltotheresultantforceandinthedirectionoftheresultantforce.proportionalto…所引导的介词短语作定语，修饰acceleration.上一页返回Lesson5HydraulicsSectionⅠTextTheword“hydraulics”generallyreferstopowerproducedbymovingliquids.Modernhydraulicsisdefinedastheuseofconfinedliquidtotransmitpower,motion.Thoughhydraulicpowerintheformofwaterwheelsandothermultiplyforce，orproducesimpledeviceshasbeeninuseforcenturies，theprinciplesofhydraulicsweren'tformulatedintoscientificlawuntilthe17thbecentury.ItwasthenthatFrenchphilosopherBlaisePascaldiscoveredthatliquidscannotcompressed.Hediscoveredalawwhichstates:Pressureappliedonaconfinedfluidistransmittedinalldirectionswithequalforceonequalareas.下一页返回Lesson5HydraulicsHydraulicsystemscontainthefollowingkeycomponents.FluidReservoirortankHydraulicpumpFluidlinesorpipesHydraulicvalvesActuatorInactualhydraulicsystems，Pascal'slawdefinesthebasisoftheresultswhichareobtainedfromthesystem.Thusapumpmoves