StudyofcleavageinitiationunderthermalshockbytestsoncrackedringsandthermomechanicalcalculationsOriginalResearchArticle

Thisarticledescribesanewtypeoftestthateasilycreatesathermalshockcombinedwithmechanicalloadingbyusingstandardlaboratoryequipments.Themethodconsistsofrapidlyheatingaringinitiallyat−175°Cbycirculatinghotwaterthroughjudiciouslyplacedholes.Itallowstoobtain,atminimalcost,dataoncrackinitiationunderthermalshockinthetransitionzoneofsteel16MND5usedforpressurevessels,thesedatabeingnecessaryforworkonfracturecriteria.Detailsoftwotestsaregiven,onewithpreloadinginwhichcleavagefracturewasobservedandonewithoutpreloadinginwhichcleavageinitiationdidnotoccur.Thethermomechanicalcalculationsnecessaryfortheinterpretationofbothtestsarealsogiven.Finally,theglobalapproachtofractureisusedinvolvingcomparisonoftheloadingpathsJ(T)withthemastercurves[ASTME1921-97,1997.Standardtestmethodfordeterminationofreferencetemperaturetoforferriticsteelsinthetransitionrange,ASTMstandards],aswellasthelocalapproachproposedbyBeremin[Beremin,F.M.,1983.Alocalcriterionforcleavagefractureofanuclearpressurevesselsteel.Metall.Trans.A14A,2777–2287]forestimatingtheprobabilityoffractureofsuchrings.Itisshownthat,inbothapproaches,thecalculatedprobabilitiesareconsistentwiththeexperimentalobservations.