Abstract :
Inengineeringapplication,almostallstructuresandcomponentscontainnotchesorholes.Theyoftenexperienceseverefatigueloading,andhavebeenrecognizedasapotentialsiteforsmallfatiguecrackinitiationandpropagation.Inthispaper,theeffectsofnotchplasticfieldonsmallfatiguecrackinitiationandpropagationfromnotchmember,undercyclictensileloadingcontrol,areinvestigated.Experimentshowsthatsmallcrackinitiatesfromnotchspecimenatfarhigherratethanthatofsmoothspecimen;smallcrackpropagationisstillfasterthanthatofsmoothspecimenwithinnotchplasticfield,thoughthisdifferenceisprogressivelylessening;beyondnotchplasticzone,smallcrackgrowthrateisapproachinglongcrackgrowthrate.Analysisviafiniteelementandanalyticalmethodrevealsthatnotchplasticityhaskeyinfluenceonsmallcrackinitiation,cracktipgeneratedplasticityhascriticalimpactonsmallcrackpropagationwithinnotchplasticfield,whileplasticityinducedcrackclosurehasdominanteffectoncrackpropagationoutofnotchplasticfield.Acomparisonbetweenexperimentalandanalyticalresultsismadetoidentifythemechanismsofsmallfatiguecrackinitiationandpropagationwithinnotchplasticfield.
