Abstract :
Theaimofthisstudyistoproposeaphysicallybasedintergranularcreepdamagemodelfornumericalsimulationsonextrapolatedsituations.Acontinuumdamageformulationisproposedtoevaluatenucleation,growthandcoalescenceofintergranularcreepcavities.Nucleationisbasedonanempiricallawwherevoidfractiongrowthrateisproportionaltothecreepstrainrate.Voidgrowthrateincludesthecontributionof:viscoplasticstrainrateofsurroundinggrains(Gurson),andvacancydiffusionalonggrainboundaries(HullandRimmer).Voidcoalescenceisbasedonamechanicalfracturecriterion,wherethecompetitionbetweendamagesofteningandviscoplastichardeningisconsidered.Theidentificationprocedureneedsonlytheresultsofuniaxialcreeptensiletestswitharangeoftimetorupturethatenablesasufficientdiffusioncontribution.Theconstrainteffectistakenintoaccountintheformulationofthemodelanddoesnotneedaspecificidentification.Toillustratethecapacityoftheproposedmodel,applicationsarepresentedforanausteniticstainlesssteeltestedat600°C.Itappearsthattheconstrainteffectassessmentisingoodagreementwithexperimentalresults,whenwecomparetimetoruptureandintergranulardamagelocalisationonnotchedspecimens,orcrackinitiationtimeandcrackgrowthrateonfatiguepre-crackedspecimens.
