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1、河南理工大学万方科技学院本科毕业论文外文资料和中文翻译外文资料ResidualStressesAresidualstressisonethatexistswithoutexternalloadingorinternaltemperaturedifferencesonastructureormachine.Itisusuallyaresultofmanufacturingorassemblingoperations.Sometimesitiscalledinitialstress,andtheoper
2、ation,pressureswhenthestructureormachineisputintoservice,theserviceloadssuperimposestresses.Iftheresidualstressesaddtotheservice-loadssuperimposestresses,theyaredetrimental;iftheysubtractfromtheservice-loadstressestheyarebeneficial.Onlyafewexamplesofde
3、trimentalresidualstresseswillbegivenhere.One,intheassemblyofmachinery,occurswhentwoshaftsarenotinlineorareafewthousandthsofaninchoutofparallel,andtheyareforcedintoconnectionbyrigidcouplings.Theresultingstressesintheshaftsbecomereversingstresseswhenthes
4、haftsarerotated.Thecorrection,whenperfectalignmentcannotbeeconomicallyattained,asisfrequentlythecase,istouseflexiblecouplingsofatypenecessaryforthedegreeofmisalignment.Theprecedingcaseoccurswithelasticstressesonly,andtheresidualstressesaremaintainedbyb
5、earingconstraints.Inapplicationwheremechanicalworkcausesplasticyielding,stressesremainwhentheconstraintsareremoved.Forexample,theforgingofshaftsandcrankshaftsandthecoolingafterforgingmayinduceresidualstresses,theequilibriumofwhichischangedinmachining,c
6、ausingsomewarpingoftheshafts.Itisthencommonpracticetostraightentheshaftsinapressbeforethefinalmachining9河南理工大学万方科技学院本科毕业论文operation.Straighteningrequiresabendingmomentlargeenoughtocausepermanentsetoryielding.Detrimentalresidualstressescommonlyresultfro
7、mdifferentialheatingorcooling.Aweldisacommonexample.Theweldmetalandtheareasimmediatelyadjacentare,aftersolidification,atamuchhighertemperaturethanthemailbodyofmetal.Thenaturalcontractionofthemetalalongthelengthoftheweldispartiallypreventedbythelargeadj
8、acentbodyofcoldmetal.Henceresidualtensilestressesaresetupslingtheweld.Ingeneral,localorshallowheatingwhichwouldexpandtheregionorsurface,Iftitwerefree,adistancewellbeyondthatwhichtheadjacentlargervolumewillallowcauseyieldingandupsettingo
