外文翻译--机械工程简介.doc

-1-IntroductiontoMechanicalEngineeringMechanicalengineeringisthebranchofengineeringthatdealswithmachinesandtheproductionofpower.Itisparticularlyconcernedwithforcesandmotion.HistoryofMechanicalEngineeringTheinventionofthesteamengineinthelatterpartofthe18thcentury,providingakeysourceofpowerfortheIndustrialRevolution,gaveanenormousimpetustothedevelopmentofmachineryofalltypes.Asaresultanewmajorclassificationofengineering,separatefromcivilengineeringanddealingwithtoolsandmachines,developed,receivingformalrecognitionin1847inthefoundingoftheInstitutionofMechanicalEngineersinBirmingham,England.Mechanicalengineeringhasevolvedfromthepracticebythemechanicofanartbasedlargelyontrialanderrortotheapplicationbytheprofessionalengineerofthescientificmethodinresearch,design,andproduction.Thedemandforincreasedefficiency,inthewidestsense,iscontinuallyraisingthequalityofworkexpectedfromamechanicalengineerandrequiringofhimahigherdegreeofeducationandtraining.Notonlymustmachinesrunmoreeconomicallybutcapitalcostsalsomustbeminimized.FieldsofMechanicalEngineeringDevelopmentofmachinesfortheproductionofgoodsThehighmaterialstandardoflivinginthedevelopedcountriesowesmuchtothemachinerymadepossiblebymechanicalengineering.Themechanicalengineercontinuallyinventsmachinestoproducegoodsanddevelopsmachinetoolsofincreasingaccuracyandcomplexitytobuildthemachines.Theprincipallinesofdevelopmentofmachineryhavebeenanincreaseinthespeedofoperationtoobtainhighratesofproduction,improvementinaccuracytoobtainqualityandeconomyintheproduct,andminimizationofoperatingcosts.Thesethreerequirementshaveledtotheevolutionofcomplexcontrolsystems.Themostsuccessfulproductionmachineryisthatinwhichthemechanical-2-designofthemachineiscloselyintegratedwiththecontrolsystem,whetherthelatterismechanicalorelectricalinnature.Amoderntransferline(conveyor)forthemanufactureofautomobileenginesisagoodexampleofthemechanizationofacomplexseriesofmanufacturingprocesses.Developmentsareinhandtoautomateproductionmachineryfurther,usingcomputerstostoreandprocessthevastamountofdatarequiredformanufacturingavarietyofcomponentswithasmallnumberofversatilemachinetools.Oneaimisacompletelyautomatedmachineshopforbatchproduction,operationonathree-shiftbasisbutattendedbyastaffforonlyoneshiftperday.DevelopmentofmachinesfortheproductionofpowerProductionmachinerypresupposesanamplesupplyofpower.Thesteamengineprovidedthefirstpracticalmeansofgeneratingpowerfromheattoaugmenttheoldsourcesofpowerfrommuscle,wind,andwater.Oneofthefirstchallengestothenewprofessionofmechanicalengineeringwastothesteamturbineandassociatedlargesteamboilers.The20thcenturyhaswitnessedacontinuedrapidgrowthinthepoweroutputofturbinesfordrivingelectricgenerators,togetherwithasteadyincreaseinthermalefficiencyandreductionincapitalcostperkilowattoflargepowerstations.Finally,mechanicalengineersacquiredtheresourceofnuclearenergy,whoseapplicationhasdemandedanexceptionalstandardofreliabilityandsafetyinvolvingthesolutionofentirelynewproblems.Thecontrolsystemsoflargepowerplantsandcompletenuclearpowerstationshavebecomehighlysophisticatednetworksofelectronic,fluidic,electric,hydraulic,andmechanicalcomponents,alloftheseinvolvingtheprovinceofthemechanicalengineer.Themechanicalengineerisalsoresponsibleforthemuchsmallerinternalcombustionengines,bothreciprocating(gasolineanddiesel)androtary(gas-turbineandWankel)engines,withtheirwidespreadtransportapplications.Inthetransportationfieldgenerally,inairandspaceaswellasonlandandsea,themechanicalengineerhascreatedtheequipmentandthepowerplant,collaboratingincreasinglywiththeelectricalengineer,especiallyinthedevelopmentofsuitablecontrolsystems.-3-DevelopmentofmilitaryweaponsTheskillsappliedtowarbythemechanicalengineeraresimilartothoserequiredincivilianapplications,thoughthepurposeistoenhancedestructivepowerratherthantoraisecreativeefficiency.Thedemandsofwarhavechanneledhugeresourcesintotechnicalfields,however,andledtodevelopmentsthathaveprofoundbenefitsinpeace.Jetaircraftandnuclearreactorsarenotableexamples.BioengineeringBioengineeringisareactivelynewanddistinctfieldofmechanicalengineeringthatincludestheprovisionofmachinestoreplaceoraugmentthefunctionsofthehumanbodyandofequipmentforuseinmedicaltreatment.Artificiallimbshavebeendevelopedincorporatingsuchlifelikefunctionsaspoweredmotionandtouchfeedback.Developmentisrapidinthedirectionofartificialspare-partsurgery.Sophisticatedheart-lungmachinesandsimilarequipmentpermitoperationsofincreasingcomplexityandpermitthevitalfunctionsinseriouslyinjuredordiseasedpatientstobemaintained.EnvironmentalcontrolSomeoftheearliesteffortsofmechanicalengineerswereaimedatcontrollingmansenvironmentbypumpingwatertodrainorirrigatelandandbyventilatingmines.Theubiquitousrefrigeratingandair-conditionplantsofthemodernagearebasedonareversedheatengine,wherethesupplyofpower“pumps”heatfromthecoldregiontothewarmerexterior.Manyoftheproductsofmechanicalengineering,togetherwithtechnologicaldevelopmentsinotherfields,havesideeffectsontheenvironmentandgiverisetonoise,thepollutionofwaterandair,andthederelictionoflandandscenery.Therateofproduction,bothofgoodsandpower,isrisingsorapidlythatregenerationbynaturalforcescannolongerkeeppace.Arapidlygrowingfieldformechanicalandotherisenvironmentalcontrol,comprisingthedevelopmentofmachinesandprocessedthatwillproducefewerpollutantsandofnewequipmentandtechniquesthatcanreduceorremovethepollutionalreadygenerated.FunctionsofMechanicalEngineeringFourfunctionsofthemechanicalengineering,commontoallthefieldsmentioned,becited.Thefirstistheunderstandingofanddealingwiththebases-4-ofmechanicalscience.Theseincludedynamics,concerningtherelationbetweenforcesandmotion,suchasinvibration；automaticcontrol；thermodynamics,dealingwiththerelationsamongthevariousformsofheat,energy,andpower；fluidflow；heattransfer；lubrication；andpropertiesofmaterials.Secondisthesequenceofresearch,design,anddevelopment.Thisfunctionattemptstobringaboutthechangesnecessarytomeetpresentandfutureneeds.Suchworkrequiresnotonlyaclearunderstandingofmechanicalscienceandanabilitytoanalyzeacomplexsystemintoitsbasicfactors,butalsotheoriginalitytosynthesizeandinvent.Thirdisproductionofproductsandpower,whichembracesplanning,operation,andmaintenance.Thegoalistoproducethemaximumvaluewiththeminimuminvestmentandcostwhilemaintainingorenhancinglongertermviabilityandreputationoftheenterpriseortheinstitution.Fourthisthecoordinatingfunctionsofthemechanicalengineering,includingmanagement,consulting,and,insomecases,marketing.Inallofthesefunctionsthereisalongcontinuingtrendtowardtheuseofscientificinsteadoftraditionalorintuitivemethods,anaspectoftheever-growingprofessionalismofmechanicalengineering.Operationsresearch,valueengineering,andPABLA(problemanalysisbylogicalapproach)aretypicaltitlesofsuchnewrationalizedapproaches.Creativity,however,cannotberationalized.Theabilitytotaketheimportantandunexpectedstepthatopensupnewsolutionsremainsinmechanicalengineering,aselsewhere,largelyapersonalandspontaneouscharacteristic.TheFutureofMechanicalEngineeringThenumberofmechanicalengineerscontinuestogrowasrapidlyasever,whilethedurationandqualityoftheirtrainingincreases.Thereisagrowingawareness,however,amongengineersandinthecommunityatlargethattheexponentialincreaseinpopulationandlivingstandardsisraisingformidableproblemsinpollutionoftheenvironmentandtheexhaustionofnaturalresources；thisclearlyheightenstheneedforallofthetechnicalprofessionstoconsiderthelong-termsocialeffectsofdiscoveriesanddevelopments.Therewillbean