故障的分析、尺寸的决定以及凸轮的分析和应用-毕业设计外文翻译

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1、FailureAnalysis，DimensionalDeterminationAndAnalysis，ApplicationsOfCamsINTRODUCTIONItisabsolutelyessentialthatadesignengineerknowhowandwhypartsfailsothatreliablemachinesthatrequireminimummaintenancecanbedesigned．Sometimesafailurecanbeserious，suchaswhenatireblowsoutonanautomo

2、biletravelingathighspeed．Ontheotherhand，afailuremaybenomorethananuisance．Anexampleisthelooseningoftheradiatorhoseinanautomobilecoolingsystem．Theconsequenceofthislatterfailureisusuallythelossofsomeradiatorcoolant，aconditionthatisreadilydetectedandcorrected．Thetypeofloadapart

3、absorbsisjustassignificantasthemagnitude．Generallyspeaking，dynamicloadswithdirectionreversalscausegreaterdifficultythanstaticloads，andtherefore，fatiguestrengthmustbeconsidered．Anotherconcerniswhetherthematerialisductileorbrittle．Forexample，brittlematerialsareconsideredtobeu

4、nacceptablewherefatigueisinvolved．Manypeoplemistakinglyinterpretthewordfailuretomeantheactualbreakageofapart．However，adesignengineermustconsiderabroaderunderstandingofwhatappreciabledeformationoccurs．Aductilematerial，howeverwilldeformalargeamountpriortorupture．Excessivedefo

5、rmation，withoutfracture，maycauseamachinetofailbecausethedeformedpartinterfereswithamovingsecondpart．Therefore，apartfails(evenifithasnotphysicallybroken)wheneveritnolongerfulfillsitsrequiredfunction．Sometimesfailuremaybeduetoabnormalfrictionorvibrationbetweentwomatingparts．F

6、ailurealsomaybeduetoaphenomenoncalledcreep，whichistheplasticflowofamaterialunderloadatelevatedtemperatures．Inaddition，theactualshapeofapartmayberesponsibleforfailure．Forexample，stressconcentrationsduetosuddenchangesincontourmustbetakenintoaccount．Evaluationofstressconsidera

7、tionsisespeciallyimportantwhentherearedynamicloadswithdirectionreversalsandthematerialisnotveryductile．Ingeneral，thedesignengineermustconsiderallpossiblemodesoffailure，whichincludethefollowing．——Stress——Deformation——Wear——Corrosion——Vibration——Environmentaldamage——Loosening

8、offasteningdevicesThepartsizesandshapesselectedalsomusttakeintoaccountmanydimensio