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1、FundamentalsofMechanicalDesignMechanicaldesignmeansthedesignofthingsandsystemsofamechanicalnature—machines,products,structures,devices,andinstruments.Forthemostpartmechanicaldesignutilizesmathematics,thematerialssciences,andtheengineering-mechanicssciences.Thetotaldesignprocess
2、isofinteresttous.Howdoesitbegin?Doestheengineersimplysitdownathisdeskwithablanksheetofpaper?And,ashejotsdownsomeideas,whathappensnext?Whatfactorsinfluenceorcontrolthedecisionswhichhavetobemade?Finally,then,howdoesthisdesignprocessend?Sometimes,butnotalways,designbeginswhenaneng
3、ineerrecognizesaneedanddecidestodosomethingaboutit.Recognitionoftheneedandphrasingitinsomanywordsoftenconstituteahighlycreativeactbecausetheneedmaybeonlyavaguediscontent,afeelingofuneasiness,ofasensingthatsomethingisnotright.Theneedisusuallynotevidentatall.Forexample,theneedtod
4、osomethingaboutafood-packagingmachinemaybeindicatedbythenoiselevel,bythevariationsinpackageweight,andbyslightbutperceptiblevariationsinthequalityofthepackagingorwrap.Thereisadistinctdifferencebetweenthestatementoftheneedandtheidentificationoftheproblem.Whichfollowsthisstatement
5、?Theproblemismorespecific.Iftheneedisforcleanerair,theproblemmightbethatofreducingthedustdischargefrompower-plantstacks,orreducingthequantityofirritantsfromautomotiveexhausts.Definitionoftheproblemmustincludeallthespecificationsforthethingthatistobedesigned.Thespecificationsare
6、theinputandoutputquantities,thecharacteristicsofthespacethethingmustoccupyandallthelimitationsonthesequantities.Wecanregardthethingtobedesignedassomethinginablackbox.Inthiscasewemustspecifytheinputsandoutputsoftheboxtogetherwiththeircharacteristicsandlimitations.Thespecificatio
7、nsdefinethecost,thenumbertobemanufactured,theexpectedlife,therange,theoperatingtemperature,andthereliability.Therearemanyimpliedspecificationswhichresulteitherfromthedesigner'sparticularenvironmentorfromthenatureoftheproblemitself.Themanufacturingprocesseswhichareavailable,toge
8、therwiththefacilitiesofacertainplant,constituterestric