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1、西北工六大李硕一!:学位论文ABSTRACTLaserRapidForming(LRF)isanewandadvancedSolidFreedomFabricationtechnologywhichhasbeendevelopedrapidlyintherecenttenyears.ThistechnologyintegratesvirtuesofRapidPrototypingandLaserCladdingtechnology,andcanataindirectlyhighperformanceanddensemetalpartwithoutmould,withwide
2、rapplicationforeground.ThispaperstudiesmechanicalbehaviorofLaserRapidFormingmetalpartbyexperiment,includingcrackingbehavior,residualstressdistributionandmechanicalproperty.Theformingmechanismandinfluencingfactorsofcrackinlaserrapidformingcladdinglayersareinvestigatedthroughmicromeasurement
3、andanalysismethods.Fornickel-baseself-fusedalloys,thecrackingofcladdinglayersbelongstothecoldcrackdomain,Whichistheresultofcollectiveeffectoflowductilityofsuchalloysandresidualstressinducedincladdinglayers.For316Lstainlesssteelalloy,thecrackingofcladdinglayersbelongstothehotcrackdomain,Whi
4、chismainlycausedbytheseparationofliquidfilmsinthegrainboundaryundertheeffectoftensilestressincladdinglayers.Twokindsofcrackingsshowthatthetensilestressinducedforasymmetrictemperaturedistributionduringlaserrapidformingprocessingistheexternalreasonwhichresultsincracks.Theplanarresidualstress
5、esofLaserRapidFormingsheetsamplesaremeasuredbythehole-drillingmethod.Theresultsshowthattheresidualstressayparalleltolaserscanningdirectionisthemajorresidualstressofsamples,whichispositive.Comparably,theresidualstressa.perpendiculartolaserscanningdirectionissmaller.ForNi20alloy,Inthelimited
6、claddingheight,ayisnegativenearsubstrateandbeginstoturntotensilestressascladdinglayersincrease,thetensilestressnumericalvalueincreasesgradually,whichimpliesthatresidualstressaccumulatesaslaserenergyinputscontinuously.。:ispositiveincladdinglayers,numericalvalueissmall.Thetensilestressdecrea
7、sesascladdinglayersincrease,hasatrendtoturntocompressivestress.For316Lstainlesssteelalloy,Inthewholecladdingheight,ayanda.arepositiveBecauseresidualstressaccumulatesgradually,6,,islargertensilestressnearsubstrateaboveoneheight,aydecreasesandgoessteadyascladdin
