喷丸残余应力场与三维次表面裂纹应力强度因子求解

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1、上海交通大学硕士学位论文应力强度因子在数值上要小于表面裂纹的应力强度因子，即残余应力场对萌生于材料表面的裂纹扩展速率的影响更为明显。次表面裂纹靠近有限边界的前缘对应力变化以及距离边界的尺寸的变化更为敏感。关键词：应力强度因子，次表面裂纹，三维权函数，残余应力，喷丸II万方数据上海交通大学硕士学位论文RESIDUALSTRESSESANDTHREEDIMENSIONALSTRESSINTENSITYFACTORSOFSUBSURFACECRACKSFORSHOT-PEENED-MATERIALSABSTRACTAst

2、hemostusefulmethodtoimprovethesurfaceconditionsandincreasethefatiguelifeformaterialsandstructures,shot-peeninghasbeenwidelyusedinthedesignofaerospaceandautomobilecomponents.Themainmechanismofshot-peeningistheintroductionofresidualcompressivestressfield,whichca

3、nchangethecrackinitiationlocationsanddecreasethecrackpropagationrate.Thus,quantitativestudyoftheresidualstressesandthestressintensityfactorsaftershot-peeninghasbeenanimportantsubjectintheoreticalandpracticalfield.Firstly,withthecomparisonbetweenthepredictionsa

4、ndtestresultsofvariousshot-peenedmetals,thecapabilityoffivesolutionsincludingempiricalequations,theoreticalmodelsandFEMmodelsforpredictingthecharacteristicparametersofresidualstressfieldwasproved.TheempiricalequationsofYaohadgoodpredictionsfor40Crsteelandother

5、similarsteels，andtheempiricalequationsofWangwerecapableofvariousmetalswhiletheoreticalmodelsweresuitableformetalswithmediumstrengthandhardeningrate.Thepredictingresultsofsingle-shotFEMmodelsforcalculatingthepeeningdentsdiametersandmulti-shotFEMmodelsforcalcula

6、tingtheresidualstressfieldwereingoodagreementwithtestresultsofvariousmetalswithdifferentshot-peeningcoverage.Inpractice，combinationsofthesemethodswereneeded.Secondly,tostudythebehaviorandthethreedimensionalstressintensityfactorsofsubsurfacecracks,thecrackbodyw

7、asconsideredasellipticalcrackanddecomposedintotwokindsofslips,thatistheIII万方数据上海交通大学硕士学位论文fundamentalslipswithmulti-collinearcracksfeaturesandtheelastic-springslipswitheccentriccracksfeatures.Basedonthethreedimensionalweightfunctiontheory,thethreedimensionalwe

8、ightfunctionsofthesubsurfaceellipticalcrackswereachieved.Finally,onthebasisofthethreedimensionalsubsurfaceweightfunctions,thestressintensityfactorsofthe40Crsteelaftershot-peeningwe