机械设计过程外文文献翻译中英翻译外文翻译.docx

机械设计过程外文文献翻译中英翻译外文翻译.docx

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机械设计过程外文文献翻译中英翻译外文翻译

TheDesignofMachineryProcess

DesignInventionCreativity

Theseareallfamiliartermsbutmaymeandifferentthingstodifferentpeople.Thesetermscanencompassawiderangeofactivitiesfromstylingthenewestlookinclothing,tocreatingimpressivearchitecture,toengineeringamachineforthemanufactureoffacialtissues.Engineeringdesign,whichweareconcernedwithhere,embodiesallthreeoftheseactivitiesaswellasmanyothers.TheworddesignisderivedfromtheLatindesignare,whichmeans“todesignate,ormarkout.”Webster’sgivesseveraldefinitions,themostapplicablebeing“tooutline,plot,orplan,asactionorwork…toconceive,invent-contrive.”Engineeringdesignhasbeendefinedas“...theprocessofapplyingthevarioustechniquesandscientificprinciplesforthepurposeofdefiningadevice,aprocessorasysteminsufficientdetailtopermititsrealization...Designmaybesimpleorenormouslycomplex,easyordifficult,mathematicalornonmathematical;itmayinvolveatrivialproblemoroneofgreatimportance.”Designisauniversalconstituentofengineeringpractice.Butthecomplexityofengineeringsubjectsusuallyrequiresthatthestudentbeservedwithacollectionofstructured,set-pieceproblemsdesignedtoelucidateaparticularconceptorconceptsrelatedtotheparticulartopic.Thesetextbookproblemstypicallytaketheformof“givenA,B,C,andD,findE.”Unfortunately,real-lifeengineeringproblemsarealmostneversostructured.Readdesignproblemsmoreoftentaketheformof“Whatweneedisaframustostuffthiswidgetintothatholewithinthetimeallocatedtothetransferofthisothergizmo.”Thenewengineeringgraduatewillsearchinvainamonghisorhertextbooksformuchguidancetosolvesuchaproblem.Thisunstructuredproblemstatementusuallyleadstowhatiscommonlycalled“blankpapersyndrome.”Engineersoftenfindthemselvesstaringatablanksheetofpaperponderinghowtobeginsolvingsuchanill-definedproblem.

Muchofengineeringeducationdealswithtopicsofanalysis,whichmeanstodecompose,totakeapart,toresolveintoitsconstituentparts.Thisisquitenecessary.Theengineermustknowhowtoanalyzesystemsofvarioustypes,mechanical,electrical,thermalorfluid.Analysisrequiresathoroughunderstandingofboththeappropriatemathematicaltechniquesandthefundamentalphysicsofthesystem’sfunction.But,beforeanysystemcanbeanalyzed,itmustexist,andablanksheetofpaperprovideslittlesubstanceforanalysis.Thusthefirststepinanyengineeringdesignexerciseisthatofsynthesis,whichmeansputtingtogether.

Thedesignengineer,inpractice,regardlessofdiscipline,continuouslyfacesthechallengeofstructuringtheunstructuredproblem.Inevitably,theproblemasposedtotheengineerisill-definedandincomplete.Beforeanyattemptcanbemadetoanalyzethesituationheorshemustfirstcarefullydefinetheproblem,usinganengineeringapproach.Toensurethatanyproposedsolutionwillsolvetherightproblem.Manyexamplesexistofexcellentengineeringsolutionswhichwereultimatelyrejectedbecausetheysolvedthewrongproblem,i.e.,adifferentonethantheclientreallyhad.

Muchresearchhasbeendevotedtothedefinitionofvarious“designprocesses”intendedtoprovidemeanstostructuretheunstructuredproblemandleadtoaviablesolution.Someoftheseprocessespresentdozensofsteps,othersonlyafew.Theonepresentedintable1-1contains10stepsandhas,intheauthor’sexperience,provensuccessfulinover30yearsofpracticeinengineeringdesign.

ITERATIONBeforediscussingeachofthesestepsindetailitisnecessarytopointoutthatthisisnotaprocessinwhichoneproceedsfromsteponethroughteninalinearfashion.Ratheritis,byitsnature,aniterativeprocessinwhichprogressismadehaltingly,twostepsforwardandonestepback.Itisinherentlycircular.Toiteratemeanstorepeat,toreturntoapreviousstate.If,forexample,yourapparentlygreatidea,uponanalysis,turnsouttoviolatethesecondlawofthermodynamics,youcanreturntotheideationstepandgetabetteridea!

Or,ifnecessary,youcanreturntoanearlierstepintheprocess,perhapsthebackgroundresearch,andlearnmoreabouttheproblem.Withtheunderstandingthattheactualexecutionoftheprocessinvolvesiteration,forsimplicity,wewillnowdiscusseachstepintheorderlistedintable1-1.

IdentificationofNeed

Thisfirststepisoftendoneforyoubysomeone,bossorclient,saying“Whatweneedis...”Typicallythisstatementwillbebriefandlackingindetail.Itwillfallfarshortofprovidingyouwithastructuredproblemstatement.Forexample,theproblemstatementmightbe“Weneedabetterlawnmower.”

Backgroundresearch

Thisisthemostimportantphaseintheprocess,andisunfortunatelyoftenthemostneglected.Thetermresearch,usedinthiscontext,shouldnotconjureupvisionsofwhite-coatedscientistsmixingconcoctionsintesttubes.Ratherthisisresearchofamoremundanesort,gatheringbackgroundinformationontherelevantphysics,chemistry,orotheraspectsoftheproblem.Alsoitisdesirabletofindoutifthis,orasimilarproblem,hasbeensolvedbefore.Thereisnopointinreinventingthewheel.Ifyouareluckyenoughtofindaready-madesolutiononthemarket,itwillnodoubtbemoreeconomicaltopurchaseitthantobuildyourown.Mostlikelythiswillnotbethecase,butyoumaylearnagreatdealabouttheproblemtobesolvedbyinvestigatingtheexisting“art”associatedwithsimilartechnologiesandproducts.Thepatentliteratureandtechnicalpublicationsinthesubjectareaareobvioussourcesofinformationandareaccessibleviatheworldwideweb.Clearly,ifyoufindthatthesolutionexistsandiscoveredbyapatentdesignsomethingwhichdoesnotconflictwiththepatent,ordroptheproject.Itisveryphaseoftheprocessinordertoavoidtheembarrassmentofconcoctingagreatsolutionlittleattentiontothisphaseandjumptooquicklyintotheideationandinventionstageoftheprocess.Thismustbeavoided!

Youmustdisciplineyourselftonottrytosolvetheproblembeforethoroughlypreparingyourselftodoso.

GoalStatement

Oncethebackgroundoftheproblemareaasoriginallystatedisfullyunderstood,youwillbereadytorecastthatproblemintoamorecoherentgoalstatement.Thisnewproblemstatementshouldhavethreecharacteristics.Itshouldbeconcise,begeneral,andbeuncoloredbyanytermswhichpredictasolution.Itshouldbecouchedintermsoffunctionalvisualization,meaningtovisualizeitsfunction,ratherthananyparticularembodiment.Forexample,iftheoriginalstatementofneedwas“DesignaBetterLawnMower,”afterresearchintothemyriadofwaystocutgrassthathavebeendevisedovertheages,thewisedesignermightrestatethegoalas“DesignaMeanstoShortenGrass.”Theoriginalproblemstatementhasabuilt-intrapintheformofthecoloredwords“lawnmower.”Formostpeople,thisphrasewillconjureupavisionofsomethingwithwhirringbladesandanoisyengine.Fortheideationphasetobemostsuccessful,itisnecessarytoavoidsuchimagesandtostatetheproblemgenerally,clearly,andconcisely.Asanexercise,list10waystoshortengrass.Mostofthemwouldnotoccurtoyouhadyoubeenaskedfor10betterlawnmowerdesigns.Youshouldusefunctionalvisualizationtoavoidunnecessarilylimitingyourcreativity!

PerformanceSpecifications

Whenthebackgroundisunderstood,andthegoalclearlystated,youarereadytoformulateasetofperformancespecifications.Theseshouldnotbedesignspecifications.Thedifferenceisthatperformancespecificationsdefinewhatthesystemmustdo,whiledesignspecificationsdefinehowitmustdoit.Atthisstageofthedesignprocessitisunwisetoattempttospecifyhowthegoalistobeaccomplished.Thatisleftfortheideationphase.Thepurposeoftheperformancespecificationsistocarefullydefineandconstraintheproblemsothatitbothcanbesolvedandcanbeshowntohavebeensolvedafterthefact.Asamplesetofperformancespecificationsforour“grassshortener”isshowninTable1-2.

TABLE1-2PerformanceSpecifications

1Devicetohaveself-containedpowersupply.2Devicetobecorrosionresistant.

3Devicetocostlessthan＄100.00.

4Devicetoemit<80dBsoundintensityat50feet.

5Devicetoshorten1/4acreofgrassperhour.6etc...etc.

Notethatthesespecificationsconstrainthedesignwithoutoverlyrestrictingtheengineer’sdesignfreedom.Itwouldbeinappropriatetorequireagasolineengineforspecification1,sinceotherpossibilitiesexistwhichwillprovidethedesiredmobility.Likewise,todemandstainlesssteelforallcomponentsinspecification2wouldbeunwise,sincecorrosionresistancecanbeobtainedbyother,less-expensivemeans.Inshort,theperformancespecificationsservetodefinetheprobleminascompleteandasgeneralamanneraspossible,andtheyserveasacontractualdefinitionofwhatistobeaccomplished.Thefinisheddesigncanbetestedforcompliancewiththespecifications.

IdeationandInvention

Thisstepisfullofbothfunandfrustration.Thisphaseispotentiallythemostsatisfyingtomostdesigners,butitisalsothemostdifficult.Agreatdealofresearchhasbeendonetoexplorethephenomenonof“creativity.”Itis,mostD,acommonhumantrait.Itiscertainlyexhibitedtoaveryhighdegreebyallyoungchildren.Therateanddegreeofdevelopmentthatoccursinthehumanfrombirththroughthefirstfewyearsoflifecertainlyrequiressomeinnatecreativity.SomehaveclaimedthatourmethodsofWesterneducationtendtostiflechil