机械设计专业的毕业设计英文版.docx

机械设计专业的毕业设计英文版.docx

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机械设计专业的毕业设计英文版

MechanicalEngineering

IntroductiontoMechanicalEngineering

Mechanicalengineeringisthebranchofengineeringthatdealswithmachinesandtheproductionofpower.Itisparticularlyconcernedwithforcesandmotion.

HistoryofMechanicalEngineering

Theinventionofthesteamengineinthelatterpartofthe18thcentury,providingakeysourceofpowerfortheIndustrialRevolution,gaveanenormousimpetustothedevelopmentofmachineryofalltypes.Asaresultanewmajorclassificationofengineering,separatefromcivilengineeringanddealingwithtoolsandmachines,developed,receivingformalrecognitionin1847inthefoundingoftheInstitutionofMechanicalEngineersinBirmingham,England.

Mechanicalengineeringhasevolvedfromthepracticebythemechanicofanartbasedlargelyontrialanderrortotheapplicationbytheprofessionalengineerofthescientificmethodinresearch,design,andproduction.

Thedemandforincreasedefficiency,inthewidestsense,iscontinuallyraisingthequalityofworkexpectedfromamechanicalengineerandrequiringofhimahigherdegreeofeducationandtraining.NotonlymustmachinesrunmoreeconomicallybutcapitalCostsalsomustbeminimized.

FieldsofMechanicalEngineering

Developmentofmachinesfortheproductionofgoodsthehighmaterialstandardoflivinginthedevelopedcountriesowesmuchtothemachinerymadepossiblebymechanicalengineering.Themechanicalengineercontinuallyinventsmachinestoproducegoodsanddevelopsmachinetoolsofincreasingaccuracyandcomplexitytobuildthemachines.

Theprincipallinesofdevelopmentofmachineryhavebeenanincreaseinthespeedofoperationtoobtainhighratesofproduction,improvementinaccuracytoobtainqualityandeconomyintheproduct,andminimizationofoperatingcosts.Thesethreerequirementshaveledtotheevolutionofcomplexcontrolsystems.

Themostsuccessfulproductionmachineryisthatinwhichthemechanicaldesignofthemachineiscloselyintegratedwiththecontrolsystem,whetherthelatterismechanicalorelectricalinnature.Amoderntransferline（conveyor）forthemanufactureofautomobileenginesisagoodexampleofthemechanizationofacomplexseriesofmanufacturingprocesses.Developmentsareinhandtoautomateproductionmachineryfurther,usingcomputerstostoreandprocessthevastamountofdatarequiredformanufacturingavarietyofcomponentswithasmallnumberofversatilemachinetools.Oneaimisacompletelyautomatedmachineshopforbatchproduction,operatingonathreeshiftbasisbutattendedbyastaffforonlyoneshiftperday.

DevelopmentofmachinesfortheproductionofpowerProductionmachinerypresupposeanamplesupplyofpower.Thesteamengineprovidedthefirstpracticalmeansofgeneratingpowerfromheattoaugmenttheoldsourcesofpowerfrommuscle,wind,andwaterOneofthefirstchallengestothenewprofessionofmechanicalengineeringwastoincreasethermalefficienciesandpower。

thiswasdoneprincipallybythedevelopmentofthesteamturbineandassociatedlargesteamboilers.The20thcenturyhaswitnessedacontinuedrapidgrowthinthepoweroutputofturbinesfordrivingelectricgenerators,togetherwithasteadyincreaseinthermalefficiencyandreductionincapitalcostperkilowattoflargepowerstations.Finally,mechanicalengineersacquiredtheresourceofnuclearenergy,whoseapplicationhasdemandedanexceptionalstandardofreliabilityandsafetyinvolvingthesolutionofentirelynewproblems-Thecontrolsystemsoflargepowerplankandcompletenuclearpowerstationshavebecomehighlysophisticatednetworksofelectronic,fluidic.Electric,hydraulic,andmechanicalcomponents,ailoftheseinvolvingmeprovinceofthemechanicalengineer.

Themechanicalengineerisalsoresponsibleforthemuchsmallerinternalcombustionengines,bothreciprocating（gasolineanddiesel）androtary（gas-turbineandWankel）engines,withtheirwidespreadtransportapplications-Inthetransportationfieldgenerally,inairandspaceaswellasonlandandsea.themechanicalengineerhascreatedtheequipmentandthepowerplant,collaboratingincreasinglywiththeelectricalengineer,especiallyinthedevelopmentofsuitablecontrolsystems.

DevelopmentofmilitaryweaponsTheskillsappliedtowarbythemechanicalengineeraresimilartothoserequiredincivilianapplications,thoughthepurposeistoenhancedestructivepowerratherthantoraisecreativeefficiency.Thedemandsofwarhavechanneledhugeresourcesintotechnicalfields,however,andledtodevelopmentsthathaveprofoundbenefitsinpeace.Jetaircraftandnuclearreactorsarenotableexamples.

BiaengineeringBioengineeringisarelativelynewanddistinctfieldofmechanicalengineeringthatincludestheprovisionofmachinestoreplaceoraugmentthefunctionsofthehumanbodyandofequipmentforuseinmedicaltreatment.Artificiallimbshavebeendevelopedincorporatingsuchlifelikefunctionsaspoweredmotionandtouchfeedback.Developmentisrapidinthedirectionofartificialspare-partsurgery.Sophisticatedheart-lungmachinesandsimilarequipmentpermitoperationsofincreasingcomplexityandpermitthevitalfunctionsinseriouslyinjuredordiseasedpatientstobemaintained.

EnvironmentalcontrolSomeoftheearliesteffortsofmechanicalengineerswereaimedatcontrollingman'senvironmentbypumpingwatertodrainorirrigatelandandbyventilatingmines.Theubiquitousrefrigeratingandair-conditioningplantsofthemodemagearebasedonareversedheatengine,wherethesupplyofpower"pumps"heatfromthecoldregiontothewarmerexterior.

Manyoftheproductsofmechanicalengineering,togetherwithtechnologicaldevelopmentsinotherfields,havesideeffectsontheenvironmentandgiverisetonoise,thepollutionofwaterandair,andthederelictionoflandandscenery.Therateofproduction,bothofgoodsandpower,isrisingsorapidlythatregenerationbynaturalforcescannolongerkeeppace.Arapidlygrowingfieldformechanicalengineersandothersisenvironmentalcontrol,comprisingthedevelopmentofmachinesandprocessesthatwillproducefewerpollutantsandofnewequipmentandtechniquesthatcanreduceorremovethepollutionalreadygenerated.

FunctionsofMechanicalEngineering

Fourfunctionsofthemechanicalengineering,commontoallthefieldsmentioned,arecited.Thefirstistheunderstandingofanddealingwiththebasesofmechanicalscience.Theseincludedynamics,concerningtherelationbetweenforcesandmotion,suchasinvibration。

automaticcontrol。

thermodynamics,dealingwiththerelationsamongthevariousformsofheat,energy,andpower。

fluidflow。

heattransfer。

lubrication。

andpropertiesofmaterials.

Secondisthesequenceofresearch,design,anddevelopment.Thisfunctionattemptstobringaboutthechangesnecessarytomeetpresentandfutureneeds.Suchworkrequiresnotonlyadearunderstandingofmechanicalscienceandanabilitytoanalyzeacomplexsystemintoitsbasicfactors,butalsotheoriginalitytosynthesizeandinvent.

Thirdisproductionofproductsandpower,whichembracesplanning,operation,andmaintenance.Thegoalistoproducethemaximumvaluewiththeminimuminvestmentandcostwhilemaintainingorenhancinglongertermviabilityandreputationoftheenterpriseortheinstitution.

Fourthisthecoordinatingfunctioningofthemechanicalengineering,includingmanagement,consulting,and,insomecases,marketing.

Inallofthesefunctionsthereisalongcontinuingtrendtowardtheuseofscientificinsteadoftraditionalorintuitivemethods,anaspectoftheever-growingprofessionalismofmechanicalengineering.Operationsresearch,valueengineering,andPABLA（problemanalysisbylogicalapproach）aretypicaltitlesofsuchnewrationalizedapproaches.Creativity,however,cannotberationalized.Theabilitytotaketheimportantandunexpectedstepthatopensupnewsolutionsremainsinmechanicalengineering,aselsewhere,largelyapersonalandspontaneouscharacteristic.

TheFutureofMechanicalEngineering

Thenumberofmechanicalengineerscontinuestogrowasrapidlyasever,whilethedurationandqualityoftheirtrainingincreases.Thereisagrowing:

awareness,however,amongengineersandinthecommunityatlargethattheexponentialincreaseinpopulationandlivingstandardsisraisingformidableproblemsinpollutionoftheenvironmentandtheexhaustionofnaturalresources。

thisclearlyheightenstheneedforallofthetechnicalprofessionstoconsiderthelong-termsocialeffectsofdiscoveriesanddevelopments.-Therewillbeanincreasingdemandformechanicalengineeringskillstoprovideforman'sneedswhilereducingtoaminimumtheconsumptionofscarcerawmaterialsandmaintainingasatisfactoryenvironment.

IntroductiontoDesign

TheMeaningofDesign

Todesignistoformulateaplanforthesatisfactionofahumanneed.Theparticularneedtobesatisfiedmaybequitewelldefinedfromthebeginning.Herearetwoexamplesinwhichneedsarewelldefined:

1.Howcanweobtainlargequantitiesofpowercleanly,safely,andeconomical/withoutusingfossilfuelsandwithoutdamagingthesurfaceoftheearth?

2.Thisgearshaftisgivingtrouble。

therehavebeeneightfailuresinthelastsixweeks.Dosomethingaboutit.

Ontheotherhand,thestatementofaparticularneedtobesatisfiedmaybesonebulousandilldefinedthataconsiderableamountofthoughtandeffortisnecessaryin（ordertostateitdearlyasaproblemrequiringasolution.Herearetwoexamples.-

1.Lotsofpeoplearekilledinairplaneaccidents.

2.Inbigcitiestherearetoomanyautomobilesonthestreetsandhighways.

Thissecondtypeof