AstudyontheevolutionofcracknetworksunderthermalfatigueloadingOriginalResearchArticle

Thecracknetworkisatypicalcrackingmorphologycausedbythermalfatigueloading.Itwaspointedoutthatthecracknetworkappearedunderrelativelysmalltemperaturefluctuationsanddidnotgrowdeeply.Inthisstudy,themechanismofevolutionofcracknetworkanditsinfluenceoncrackgrowthwasexaminedbynumericalcalculation.First,thestressfieldneartwointeractingcrackswasinvestigated.Itwasshownthattherearestress-concentrationandstress-shieldingzonesaroundinteractingcracks,andthatcrackscanformanetworkunderthebi-axialstresscondition.Secondly,aMonteCarlosimulationwasdevelopedinordertosimulatetheinitiationandgrowthofcracksunderthermalfatigueloadingandtheevolutionofthecracknetwork.Thelocalstressfieldformedbypre-existingcrackswasevaluatedbythebodyforcemethodanditsroleintheinitiationandgrowthofcrackswasconsidered.Thesimulationcouldsimulatetheevolutionofthecracknetworkandchangeinnumberofcracksobservedintheexperiments.Itwasrevealedthatreductioninthestressintensityfactorduetostressfeatureinthedepthdirectionunderhighcyclethermalfatigueloadingplaysanimportantroleintheevolutionofthecracknetworkandthatmechanicalinteractionbetweencracksinthenetworkaffectsinitiationratherthangrowthofcracks.Thecracknetworkappearsonlywhenthecrackgrowthinthedepthdirectionisinterrupted.Itwasconcludedthattheemergenceofthecracknetworkispreferableforthestructuralintegrityofcrackedcomponents.