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1、本科生毕业论文（设计）外文翻译FACTORSAFFECTINGTHEENDURANCESTRENGTHPublisheddataforendurancestrengtharedeterminedbyspecialfatiguetestingdevices,whichtypicallyuseapolishedspecimensubjectedtoareversedbendingload,similarthatsketchedinfigure.Iftheactualoperatingconditionsofapartinamachinearedifferent.andtheyus
2、uallyare,thefaiguestrengthmustbereducedfromthereportedvalue.Someofthefactorsthatdecreasetheendurancestrengtharediscussednext.Thisdiscussionrelatestotheendurancestrengthformaterialssubjectedonlytotensilenormalstresses,thatis,tensilestressesresultingfrombendingactionsoraxialtension.Casesinvol
3、vingfluctuatingtorsionalshearstressesarediscussedseparately.Fatiguefailuresaremostlikelytooccurinregionsofhightensilestressratherthancompressivestress.第17页共17页本科生毕业论文（设计）SizeofthesectionThetestspecimenisusually0.30inch(7.6mm)indiameter.Largersectionsizesexhibitlowerstrengths,havealessfavora
4、blestressdistribution,andhavelessuniformityofproperties,particularlywithheat-treatedparts.Reference1includesasuggestedmethodofdetermingthesizefactorforrotatingshaftsupto10.0inches(250mm)indiameter.Wewillusethatmethodherealsobecausewearebasingouranalysisonthereversedbendingphenomenon.Tablesh
5、owsthesuggestedrelationshipsfordetermingasizefactor,tobeappliedtotheendurancestrengthtoaccountforthesizeofthecrosssection.FigureshowsplotsoftheequationsfromTable,withsomeblendingofthecurves,Readingfromthecurvesshouldprovideacceptableaccuracy.Whenthecomponentbeingdesignedisnotcircularlikeash
6、aft,judgmentisrequiredtodeterminethecharacteristicdimensiontouseintheformulas.Forflat,rolledshapes,thethicknessshouldbeused.Notedthattheuseoftheseequationsisapproximate.SurfaceFinishAnydeviationfromapolishedsurfacereducesendurancestrength.Figureshowsroughestimatesfortheendurancestrengths,co
7、mparedwiththeultimatetensilestrengthofsteelsforseveralpracticalsurfaceconditions,Itiscriticalthatpartssubjectedtofatigueloadingbeprotectedfromnicks,scratches,andcorrosionbecausetheydrasticallyreducefatiguestrength.第17页共17页本科生毕业论文（设计）StressConcentrationsS
