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1、FundamentalsofMechanicalDesignMechanicaldesignmeansthedesignofthingsandsystemsofamechanicalnature—machines,products,structures,devices,andinstruments.Forthemostpartmechanicaldesignutilizesmathematics,thematerialssciences,andtheengineering-mechanicssciences.Thetotaldesignprocessisofinteresttous.
2、Howdoesitbegin?Doestheengineersimplysitdownathisdeskwithablanksheetofpaper?And,ashejotsdownsomeideas,whathappensnext?Whatfactorsinfluenceorcontrolthedecisionswhichhavetobemade?Finally,then,howdoesthisdesignprocessend?Sometimes,butnotalways,designbeginswhenanengineerrecognizesaneedanddecidestodo
3、somethingaboutit.Recognitionoftheneedandphrasingitinsomanywordsoftenconstituteahighlycreativeactbecausetheneedmaybeonlyavaguediscontent,afeelingofuneasiness,ofasensingthatsomethingisnotright.Theneedisusuallynotevidentatall.Forexample,theneedtodosomethingaboutafood-packagingmachinemaybeindicated
4、bythenoiselevel,bythevariationsinpackageweight,andbyslightbutperceptiblevariationsinthequalityofthepackagingorwrap.Thereisadistinctdifferencebetweenthestatementoftheneedandtheidentificationoftheproblem.Whichfollowsthisstatement?Theproblemismorespecific.Iftheneedisforcleanerair,theproblemmightbe
5、thatofreducingthedustdischargefrompower-plantstacks,orreducingthequantityofirritantsfromautomotiveexhausts.Definitionoftheproblemmustincludeallthespecificationsforthethingthatistobedesigned.Thespecificationsaretheinputandoutputquantities,thecharacteristicsofthespacethethingmustoccupyandalltheli
6、mitationsonthesequantities.Wecanregardthethingtobedesignedassomethinginablackbox.Inthiscasewemustspecifytheinputsandoutputsoftheboxtogetherwiththeircharacteristicsandlimitations.Thespecificationsdefinethecost,thenumbertobemanufactured,theexpectedlife,therange,theoperatingtemperature,andtherelia
7、bility.Therearemanyimpliedspecificationswhichresulteitherfromthedesigner'sparticularenvironmentorfromthenatureoftheproblemitself.Themanufacturingprocesseswhichareavailable,togetherwiththefacilitiesofacertainplant,constituterestric
