Author/Authors :
NobuhiroIsobe، نويسنده , , MasayukiSukekawa، نويسنده , , YasunariNakayama، نويسنده , , ShingoDate، نويسنده , , TomomiOhtani، نويسنده , , YukioTakahashi، نويسنده , , NaotoKasahara، نويسنده , , HiroshiShibamoto، نويسنده , , HideakiNagashima، نويسنده , , KazuhikoInoue، نويسنده ,
Abstract :
Theeffectofratchetingonfatiguestrengthwasinvestigatedinordertorationalizethestrainlimitasadesigncriterionofcommercializedfastreactorsystems.Ratchetingfatiguetestswereconductedat550°C.Durationoftheratchetstrainingwassetforacertainnumberofstraincyclestakingtheloadingconditionoffastreactorsintoaccount,andthenumberofcyclesforstrainaccumulationwasdefinedastheratchet-expiredcycle.Fatiguelivesdecreaseastheaccumulatedstrainbyratchetingincreases.Meanstressincreasedduringtheratchetingcycleanditsmaximumvaluedependedontheaccumulatedstrainandtheratchet-expiredcycle.Fatiguelifereductionwasnegligiblewhenthemaximummeanstresswaslessthan25MPa,correspondingtoanaccumulatedstrainof2.2%.Accumulatedstrainislimitedto2%inthepresentdesignguidelinesandthisstrainlimitisconsideredeffectivetoavoidreducingfatiguelifebyratcheting.Microcrackgrowthbehaviorswerealsoinvestigatedinthesetestsinordertodiscussthelifereductionmechanismsinratchetingconditions.
