GCr15钢超高周疲劳行为的研究

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1、西南交通大学硕士学位论文GCr15钢超高周疲劳行为的研究姓名：李伟申请学位级别：硕士专业：载运工具运用工程指导教师：鲁连涛20070401西南交通大学硕士研究生学位论文第1I页AbstractConventionalfatiguedesignpointconsidersthatfatiguetestaslong嬲endurestresscirculationof107cyclescanmeetthesafetyactivityofthemechanismandengineeringstructure．B

2、utwiththehigh—speedandlarge—scaledevelopmentofmodernmechanisminrecentyears，manymechanismandengineeringstructurestillcantakeplacefatiguefailureinultra-longliferegimeexceeding107-10’cycles．Soconventionalfatiguedesignstandardandlifepredictionmethodalreadydo

3、n’tmeettheactivityacquireofmechanismequipmentinultra-longliferegime．Thestudyoftestmethodandfatiguebehaviorinultra—longliferegimealreadybecomesanimportanttaskthatthefatigueresearchersmustface．Fatiguebehaviorinultra-longliferegime(about107～1010cycles)ofhig

4、hstrengthbearsteel—GCrl5isstudiedbyusingtheconventionalrotarybendingtestandaxialloadtestmainlyandbyusingultrasonicfatiguetestsecondly．Specificallyexplainasfollows：ThefatiguecrackinitiationplaceandvicinalmarkareobservedbySEMandOMindetail．Thefatiguecrackin

5、itiationmechanismofGCrl5bearsteelisanalyzedandCanbeclassifiedintotwocrackinitiationmechanisms，oneiscalledsurfacecrackinitiationmechanism，andtheotheriscalledinternalcrackinitiationmechanism．Thematerial’fatigueS—Ncurveinthreetestsisobtainedandanalyzed．Simu

6、ltaneously,rotatebenttestdataisbetterfollowedbytheweibulldistributionandthematerial’fatigueP—s—Ncurveinrotarybendingtestisobtained．PredictionmethodofSEVisadoptedtoestimatethemaximuminclusionsizeandthefatiguestrengthofGCrl5bearsteelisestimatedbytheMurakam

7、iequation．Throughthecalculationofstressintensityfactor-A‰incrackinitiationplace，thefracturemechanicsconditionofcrackinitiationandpropagationisanalyzed．Throughthecomparisonofthetestresultsinrotarybendingtestconventionalaxialloadtestandultrasonicfatiguetes

8、t，theequivalenceofrotary西南交通大学硕士研究生学位论文第1II页bendingandconventionalaxialloadfatiguestrengthisrealizedandthecharacteroffatigueS-Ncurveandthecrackinitiationmechanismisinfluencedbythesomefactors，suchasultrasonicloadfrequencyan