棱角缺陷裂纹问题的研究论文

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1、哈尔滨工业大学工学硕士学位论文AbstractBythetraditionalconceptsandexperiences,peoplealwaysthinkthatsomeflawsinmaterialdonegativeeffecttoitsproperties.However,someflaws,suchascrack,empty,inclusions,etc.,emergesimultaneityintheproductionprocess.Asisknown,asingledefectinthematerialwillreducetheperforman

2、ce.Inthispaper,theresponseofathree-dimensionalcornercrackandaquartersphericaldefectinthesameelasticmaterialarestudied.Itisfoundthattwoormoredeficienciesinthesamematerialcanprotectstructures.Itismorehelpfultopracticalapplications.Atpresent,thefractureproblemscanbestudiedbytheoreticalme

3、thodwithsomesimplemodelsandundersomestrongassumptions.Meanwhileexperimenthashighercostandlongerperiod.Theselimitthedevelopmentoffracturemechanics.Therefore,researchersusuallyusenumericalmethodtoinvestigatethefracturebehavior,especiallytothreedimensionalsurfacecrackproblems.Itisworthpa

4、yingattentionthattheinfluenceofathree-dimensionalcornercrackinthebodywhichhasaquartersphericaldefecthasnotbeenreportedintheliteraturesofar.Bythetwo-dimensionalcrackproblemsstudiedintheexistliterature,itisfoundthatwhenthesizeoftheborderislessthanacertainvaluecomparedtothesizeofcracksiz

5、e,theimpacttostressintensityfactorofitssizecannotbeignored.Inthecurrentpaper,westudytheissueforthethree-dimensionalcornercrackofthequartersphericaldefectintheinfinitebody.Itismorecomplexthanonlycontainingasinglesurfacecrackproblem.ThestressintensityfactorofItypethree-dimensionalcorner

6、crackscanbeobtainedbyfiniteelementmethod.Itisfoundthatthesizeofquartersphericaldefecthasgreatlyaffectedtostressintensityfactorofthesurfacecracktip.Itcanpreventthecrackpropagationandmakethestructuresmoresafety.Meanwhiletheimpactofthequartersphericaldefectsizetostressintensityfactorinfi

7、nitebodyisstudied.Thenumericalresultsshowthattheeffectofquartersphericaldefecttostressintensityfactorinthefinitebodyisthesameasthatintheinfinitebody.Theinfluencetostressintensityfactorincreases-II-哈尔滨工业大学工学硕士学位论文graduallywiththereductionofitssize.Thepaperdrawsaqualitativecurvewithitss

8、izeva