机械设计英文文献

机械设计英文文献

MechanicalDesign

Abstract:

Amachineisacombinationofmechanismsandothercomponentswhichtransforms,transmits,orutilizesenergy,force,ormotionforausefulpurpose.Examplesareengines,turbines,vehicles,hoists,printingpresses,washingmachines,andmoviecameras.Manyoftheprinciplesandmethodsofdesignthatapplytomachinesalsoapplytomanufacturedarticlesthatarenottruemachines,fromhubcapsandfilingcabinetstoinstrumentsandnuclearpressurevessels.Theterm"mechanicaldesign"isusedinabroadersensethan"machinedesign"toincludetheirdesign.Forsomeapparatus,thethermalandfluidaspectsthatdeterminetherequirementsofheat,flowpath,andvolumeareseparatelyconsidered.However,themotionandstructuralaspectsandthe

provisionsforretentionandenclosureareconsiderationsinmechanicaldesign.Applicationsoccurinthefieldofmechanicalengineering,andinotherengineeringfieldsaswell,allofwhichrequiremechanicaldevices,suchasswitches,cams,valves,vessels,andmixers.

Keywords:MechanicalDesignmechanismsDesignProcessTolerance

Anoverviewofmechanicaldesign

Thefirststepinthemanufactureofanyproductisdesign.Mechanicaldesignistheapplicationofscienceandtechnologytodeviseneworimprovedproductsforthepurposeofsatisfyinghumanneeds.Itisavastfieldofengineeringtechnologywhichnotonlyconcernsitselfwiththeoriginalconceptionoftheproductintermsofitssize,shapeandconstructiondetails,butalsoconsidersthevariousfactorsinvolvedinthemanufacture，marketinganduseoftheproduct.

Peoplewhoperformthevariousfunctionsofmachinedesignaretypicallycalleddesigners,ordesignengineers.Mechanicaldesignisacreativeactivity.However,inadditiontobeinginnovative,adesignengineermustalsohaveasolidbackgroundintheareasofmechanicaldrawing,kinematics,dynamics,materialsengineering,strengthofmaterialsandmanufacturingprocesses.

Herewetaketheselectionofmaterialsasanexample.Duringrecentyearstheselectionofengineeringmaterialshasassumedgreatimportance.Moreover,theprocessshouldbeoneofcontinualreevaluation.Newmaterialsoftenbecomeavailableandtheremaybeadecreasingavailabilityofothers.Concernsregardingenvironmentpollution,recyclingandworkerhealthandsafetyoftenimposenewconstraints.Thedesireforweightreductionorenergysavingsmaydictatetheuseofdifferentmaterials.Pressuresfromdomesticandinternationalcompetition,increasedserviceabilityrequirements,andcustomerfeedbackmayallpromotematerialsreevaluation.Theextentofproductliabilityactions,oftentheresultofimpropermaterialuse,hashadamarkedimpact.Inaddition,theinterdependencebetweenmaterialandtheirprocessinghasbecomebetterrecognized.Thedevelopmentofnewprocessesoftenforcesreevaluationofthematerialbeingprocessed.Therefore,itisimperativethatdesignandmanufacturingengineersexerciseconsiderablecareinselecting,specifying,andutilizingmaterialsiftheyaretoachievesatisfactoryresultsatreasonablecostandstillassurequality.

Inmechanicsprocessing，millingandgrindingarealwaysundertheconsiderationofthedesigners.Withtheexceptionsofturninganddrilling,millingisundoubtedlythemostwidelyusedmethodofremovingmetal.Wellsuitedandreadilyadaptedtotheeconomicalproductionofanyquantityofparts,thealmostunlimitedversatilityofthemillingprocessmeritstheattentionandconsiderationofdesignersseriouslyconcernedwiththemanufactureoftheirproduct.

Grindingisoneofthemostwidelyusedmethodsoffinishingpartstoextremelyclosetolerancesandlowsurfaceroughness.Currently,therearegrindersforalmosteverytypeofgrindingoperation.Particulardesignfeaturesofapartdictatetoalargedegreethetypeofgrindingmachinerequired.Whereprocessingcostsareexcessive,partsredesignedtoutilizealessexpensive,higheroutputgrindingmethodmaybewellworthwhile.Forexample,whereverpossibletheproductioneconomyofcenterlessgrindingshouldbetakenadvantageofbyproperdesignconsideration.

Althoughgrindingisusuallyconsideredafinishingoperation,itisoftenemployedasacompletemachiningprocessonworkwhichcanbegrounddownformroughconditionwithoutbeingturnedorotherwisemachined.Thusmanytypesofforgingsandotherpartsarefinishedcompletelywiththegrindingwheelatappreciablesavingsoftimeandexpense.

Besides,theapplicationofnontraditionalmanufacturingprocesseswillbringmoreboldandinnovativedesign.Theconventionalmanufacturingprocessesinusetodayformaterialremovalprimarilyrelyonelectricmotorsandhardtoolmaterialstoperformtaskssuchassawing,drilling,andbroaching.Conventionalformingoperationsareperformedwiththeenergyfromelectricmotors,hydraulics,andgravity.Likewise,materialjoiningisconventionallyaccomplishedwiththermalenergysourcessuchasburninggasesandelectricarcs.

Incontrast,nontraditionalmanufacturingprocessesharnessenergysourcesconsideredunconventionalbyyesterday’sstandards.Materialremovalcannowbeaccomplishedwithelectrochemicalreactions,high-velocityjetsofliquidsandabrasives.Materialsthatinthepasthavebeenextremelydifficulttoform,arenowformedwithmagneticfields,explosives,andtheshockwavesfrompowerfulelectricsparks..Material-joiningcapabilitieshavebeenexpandedwiththeuseofhigh-frequencysoundwavesandbeamsofelectrons.

Inthepast50years,over20differentnontraditionalmanufacturingprocesseshavebeeninventedandsuccessfullyimplementedintoproduction.Thereasontherearesuchalargenumberofnontraditionalprocessesisthesamereasontherearesuchalargenumberofconventionalprocesses;eachprocesshasitsowncharacteristicattributesandlimitations,hencenooneprocessisbestforallmanufacturingsituations.

Inothercases,nontraditionalprocessesareusedtoreducethenumberofrejectsexperiencedbytheoldmanufacturingmethodbyincreasingrepeatability,reducingin-processbreakageoffragileworkpieces,orbyminimizingdetrimentaleffectsonworkpieceproperties.

Asstatedpreviously,thepurposeofmechanicaldesignistoproduceaproductwhichwillserveaneedforman.Inventions,discoveryandscientificknowledgebythemselvesdonotnecessarilybenefitpeople;onlyiftheyareincorporatedintoadesignedproductwillabenefitbederived.Itshouldberecognized,therefore,thatahumanneedmustbeidentifiedbeforeaparticularproductisdesigned.

Mechanicaldesignshouldbeconsideredtobeanopportunitytouseinnovativetalentstoenvisionadesignofaproduct,toanalyzethesystemandthenmakesoundjudgmentsonhowtheproductistobemanufactured.Itisimportanttounderstandthefundamentalsofengineeringratherthanmemorizemerefactsandequations.Therearenofactsorequationswhichalonecanbeusedtoprovideallthecorrectdecisionsrequiredtoproduceagooddesign.Ontheotherhand,anycalculationsmademustbedonewiththeutmostcareandprecision.

Gooddesignrequiretryingnewideasandbeingwillingtotakeacertainamountofrisk,knowingthatifthenewideanotworktheexistingmethodcanbereinstated.Thusadesignermusthavepatience,sincethereisnoassuranceofsuccessforthetimeandeffortexpended.Creatingacompletelynewdesigngenerallyrequiresthatmanyoldandwell-establishedmethodsbethrustaside.Thisisnoteasysincemanypeopleclingtofamiliarideas,techniquesandattitudes.Adesignengineershouldconstantlysearchforwaystoimproveanexistingproductandmustdecidewhatold,provenconceptsshouldbeusedandwhatnew,untriedideasshouldbeincorporated.

Duringthebeginningstagesofdesign,creativityshouldbeallowedtoflourishwithoutagreatnumberofconstraints.Eventhoughmanyimpracticalideasmayarise,itisusuallyeasytoeliminatethemintheearlystagesofdesignbeforefirmdetailsarerequiredbymanufacturing.Inthisway,innovativeideasarenotinhibited.Quiteoften,morethanonedesignisdeveloped,uptothepointwheretheycanbecomparedagainsteachother.Itisentirelypossiblethatthedesignwhichisultimatelyacceptedwilluseideasexistinginoneoftherejecteddesignsthatdidnotshowasmuchoverallpromise.

Anotherimportantpointwhichshouldberecognizedisthatadesignengineermustbeabletocommunicateideastootherpeopleiftheyaretobeincorporated.Initially,thedesignermustcommunicateapreliminarydesigntogetmanagementapproval.Thisisusuallydonebyverbaldiscussionsinconjunctionwithdrawinglayoutsandwrittenmaterial.Tocommunicateeffectively,thefollowingquestionsmustbeanswered:(1)Doesthedesignreallyserveahumanneed?(2)Willitbecompetitivewithexistingproductsofrivalcompanies?(3)Isiteconomicaltoproduce?(4)Canitbereadilymaintained?(5)Willitsellandmakeaprofit?

DesignProcess

Thedesignbeginsfromrealoforthedemandofimagination.Theexistinginstrumentmayneedtotakeintoimproveontheenduring,efficiency,weight,speedorthecost.Mayneednewinstrumenttocompletebeforefunctiondonebyperson,suchasAssembleormaintain.Thetargetisallorpartlyaftermakingsure,designofthenextmoveistoconceiveoutlinetheorganizationthatcancompletethefunctionneededanditarrangesforthis,drawinggrassdiagramtobeworthbarehandedbiggest,itisn'tonlyonepersonalrecordofviewpointwithothersdiscussionofassistancemeans,andbesuitablefortocommunicatewithownviewpointparticularly,isthestimulantwhichcreatessexwayofthinkingtostillneedextensiveknowledgeconcerningparts,becauseathesetnewmachineusuallyfrombefamiliarwithofeachkindofsparepartsrescheduleorsubstitutebutbecome,changedsizeandmaterialperhaps.Regardlessatconceiveoutlineprocessinstillafter,adesignwillcarryonafastorroughcalculationoranalyzetomakesureregulationsizeandpossibility.Whensomeconcerningneedorcanuseamountofspaceofviewpointassuranceafter,canstartproratapaintinggrassdiagram.

Finally,Icompletedaccordingtothedesignofthefunctionandthecredibility,canmakekindmachine.Iftestsatisfied,andifthedevicewantsmassproduction,willtothefirstdesigncarryonacertainmodificationtoinsurewithlowercostmass-produce.Lateronseveralyearsofmakeanduseaperiod,designprobablybecauseofconceiveoutlinenewviewpointperhapsaccordingtotestandexperiencefoundationoffurtheranalyticalthechangeshownbutchange.Sellattraction,customer'ssatisfactionandmanufacturingcoststoallhavesomethingtodowithdesign,thesuccesswhichdesignsabilityandengineeringinvestmentiscloselyrelated.

Somedesignstandards

Atthispart,someonesuggeststheattitudeoftheusagecreationcarriesonofanalysis,thiskindofanalysiscancauseagravenessimprovementandtobackuptheproductconceiveoutlinewithperfect,perhapstheproductfunctionismore,moreeconomicandmoreenduring.Creatingthestage'sneedingnotisfirstwithindependentstage.Althoughanalyzepersonnelthewholeprobablyirresponsibledesign,heisn'tonlytherightanswerof[with]problemthatcanbefromthenumeralputforwardwantinghimtoresolveonly,notonlyisgiveshoulddintvalue,thesizeworkstolimitperhaps.Hecanputforwardmoreextensiveviews,forthepurposeofimprovementnormorproject.Becauseintheanalysisthefrontortheanalysistheprocess,hewillacquaintwithtoequipanditsworkcondition,heisfullyplacedinabeneficialpositionwhichconceivesoutlinetochooseaproject.BesthecanputforwardasuggestionchangeshapetoEliminationmomentofforceorshoulddintconcentration,notallowtosetuptohavetocuttheorganizationthatnoodlesandexcessivedynamicstatecarryalotusgreatlybestishediscardshismeticulousofdesignbutisnotseeamachinediscardafterwards.

Forstiringuptocreatesexthinking,thesuggestiondesignsapersonnelandanalyticalthepersonnelusefollowingstandard.6ex-standardsareparticularlyapplicabletoananalysispersonnel,althoughhemayinvolvetoallthis10.

1.Createthephysicalfunctionthatsexlandutilizationneedwhenusingcombinethecontroldon'tneed.

2.Knowpracticalcarrylotusanditsimportance.

3.Considerinadvancethereisnofunctioncarryingalotus.

4.Inventtoaddtocarryaconditionmorebeneficially.

5.Provideminimumweightthemostbeneficialofdistributeinresponsetothedintwithrigid.

6.Useabasicandsquaredistancecalculationacomparisonandmakesizesuperiortoturn.

7.Selectbyexaminationsmaterialtoacquireafunctioncombination.

8.Atsparepartsandintegratedsparepartscarefulchoice.

9.Modifyafunctiondesignwiththeorientationproductionlineanddeclinelowcost.

10.Considertomakepartsaccuratetopositionintheassemblewitheachothernotinterference

MechanicalDesign

Thewholemachinedesignisacomplicatedprocess.Designingthepersonnelhavetoatthusofrealm,suchascalmdownmechanics,kinetics,dynamicsandmaterialmechanicshavegoodcultivatedmanners,havetoalsoacquaintwithmanufacturingmaterialandmakeacraftinaddition.Designingthepersonnelhastocancombineallrelatedfacts,carryingonTeachesWeiandcreatinggrassdiagramandgraphicstocometodeliverthemanufacturingrequesttothecar.

Thesquareonethatanyproductdesignsworksitanisthematerialthatthechoiceusedformakingeachparts.Thedesignpersonneloftodaycangetaninnumerable.Whilechoosing,function,externalappearance,materialcostandmanufacturingcostsofproductareallveryimportant.Hadtobecarefultoevaluatethefunctionofmaterialbeforeanycalculation.Itisnecessaryacarefulcalculationwiththeusefulnessofinsuringthedesign.Computetoneverappearonthediagram,butfromtenvariousreasonbesaved.Oncethewhicheverpartslosesefficacy,willclearuptodowhatwhiledesigningthisdefectivesparepartsatthebeginning;And,canacquireanexperiencedocumentfromcomputepastitem.Whileneedingthedesignforisingsimilarto,thepastrecordwillhaveatremendoushelp.Thecheckofcomputing(withdiagramtopsize)isthemostimportant.Adecimalpoint'smislayingpositioncanruinanoriginalandacceptableitem.Forexample,ifapersonwantstodesignabracketthatcanpropup100pounds,butitshouldcanpropup1000poundsoriginally,theresultaffirmationwillfail.Thesquareaspectnoodleshadtocheckachecktodesignagainawork.Thecalculatorspeakstoisanofgreatusetoolforthestaffmember,caneaseadullcalculationandprovidetoexpandanalysistotheexistingdata.Handoversystemtomakethecalculatorassistancedesign(CAD)witheachotheraccordingtothecalculatorfunctionandthecalculatorlendsupporttoamanufacturing(CAM)tomakepossible.Passthusofsystem,mayconceiveoutlineafirststeptodelivertobeatborepapertotaketousedfornumeraltoprocesscontrolbutneednottodrawformalconstructiondiagram.

Themachinedesignforthelaboratorytest,modelandkindmachineisveryhelpful.Thelaboratoryprovidedalotofbuildupbasicconceptneedofinformation,however,canalsoacquirewiththemsomeconcerningproducthowonthespotwouldtheunderstandingforworking.

Finally,adesignpersonnelofsuccessshouldofferthestepthattheutmosteffortkeepsupwithages.Willappearnewmaterialandproduceamethodeveryday.Ifpaintinganddesignpersonnel'sdon'tacquaintingwithmodernmethodandmaterialmayputoutaction.Agooddesignpersonnelshouldusuallyreadtechniqueperiodicaltokeepupwithanewdevelopment

Theengineeringworkisbad

Thesolidismadesureboundarybyitssurfaceboundary.Typicalmodelground,designapersonneltospecifyMr.tocallsizetoasparepartstomakeitcontenteditsdemand.Actuallybecauseofthesurfaceirregularandpropersurfaceroughdegree,eachsparepartscan'tmakeintoMr.tocallsize'shasingtoallowsizetohavesomevarietiescanmakewithinsuringrepeatedly.But,thevarietyallowedcan'tcertainlytoobigwithasformaketoassemblethefunctionofthepiecetobecomebad.Singlethevarietyallowedbysparepartsiscalledbusinesstrip.

Businesstripthistechnicaltermnotonlyisapplicabletofromtheacceptablescopeofthepartssizeof[with]manufacturingcraftcreation,butalsoisapplicabletoamachineorprocessesofexportation.Forexample,agivealreadysetnumberofthepowereachpedestalsofI.C.enginehavevariety.Actually,weusuallydiscoverthiskindofvarietymodelwillbeafrequencytodistributecurve,forexamplet.Thedistributes.(calltheGaussdistributeagain)Oneoftheworkwhichdesignsapersonnelisthevarietywhichspecifiessizeforasparepartsandallows,thisvaluecanproduceacceptablefunction.

Sparepartsbusinesstrip

Whenthereisnoappointedaccuratesizeinthediagram,mostorganizationsallhaveingeneralusebusinesstripofbeingapplicabletothesize.Forprocesssize,ingeneralusebusinesstrip'smayingbea±is0.5millimeters.Thereforebeingspecifiedto15.0millimeterscopesofsizescanbeof14.5-15.5millimeters.Otheringeneralusebusinesstripscanbeapplicabletosuchastheangleanddrillaholewithbluntbore,Thecasting,theforging,theweldedjointandweldtheangle）

etc.situation.

Canmakereferencetothediagramofpastorgeneralengineeringtopracticewhilegivingtheappointedbusinesstripofaspareparts.Thebusinesstripoftypicalmodel'sisingspecifiedismartialbecomeJSOstandarddefineofrange.Givetosettlebusinesstripto1,forexampleH7/s6,canuseforbeingstudyingofsparepartssizehaving1setandcharttoshouldingofnumber.Underneaththiswillgiveconcerningpackintoinsideboreoftheconcreteexamplewiththestalkorthepillarformmatch..

Thestandardmatchofboreandstalk

Astandardoftheengineeringworkisthebusinesstripwhichmakessureapillarformspareparts,installingforexampleinatubeformsparepartsorboreforcorrespondingof.perhapsisthestalkwhichrevolvesinitsinnerparttomatchwithofloosebedecidedbyapplicationtightlyforexample,awheelgearwhichpositionsonthestalkneedstobe"tight"ofquietmatch,herestalkofthediametercompareswheelgearactuallyofinsidepathalittlebitalittlebitbiginordertocandeliverneedofTorque.Furthermore,thediameterofglidebearingshastobebiginthediameterofthestalktomakeitrevolve.Onthesuppositionthatspeaktocan'tbecometheaccuratesizetothepartsmanufacturingfromtheeconomy,allofthevarietyofstalkandboresizehavetomakesure.But,varietyofscopeshouldn'tthetoobiginordertopreventassemblehourdamagedForbeingunlikelytothereiseverlastingdriveappointedbusinesstripsizeendlessly,havealreadydrawnupnationalandinternationalstandardtomakesurebusinesstriptotake,forexamplehll/cll.Forusingthisdata,gavethedefinitioninthetraditionalbusinesstripusage.UsuallywhattouseistheBasicholesystem,becausethismeetingmakescompanyinternalaugerneeded,wringknifeandpullknifeandcalculatethedecreaseoftoolcategory.

Size:Meanthenumberofthesizenumericalvaluebyappropriationunit.

Actualsize:Thepartssizegotthroughadiagraph

Sizeextremelimit:Thesparepartsallowsofbiggestwithmostbabysize.

Thebiggestsizeextremelimit:Biggerintwosizeextremelimits

Mostbabysizeextremelimit:Smallerintwosizeextremelimitsof

Basicsize:Fixthereferencesizeofsizeextremelimitinorderto

Deviation:Asizewithittoshouldofthealgebraofbasicsizebad

Actualdeviation:Actualsizewithittoshouldofthealgebraofbasicsizebad.

Lastdeviation:Thebiggestsizeextremelimitwithittoshouldofthealgebraofbasicsizebad

Descenddeviation:Mostbabysizeextremelimitwithittoshouldofthealgebraofbasicsizebad

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