简介：TheeffectoffrequencyandsampleshapeonfatiguebehaviorsofDZ125superalloyaresystematicallystudied.Theresultsshowthatfatiguefracturestilloccursabovethecycleof10~8fortestscarriedoutatthefrequencyoff=20kHzandstressratioR=-1,sothetraditionalfatiguelimitatcycleof10~7isnotappropriateforfatiguedesign.Fatiguefracturesurfacesareperpendiculartostressaxisforcylindricalandplatespecimens,andthefatiguecracksoriginatefromtheextrasurfaceofthespecimens.Fatiguecrackisapttopropagatefromcuttingdirectiontoforwarddirection,whichoccursmainlyinthesecondpropagationstageathigherstressamplitude.ThereisanobviousfrequencyeffectforDZ125superalloy.Thehigherthetestfrequencyis,themoreserioustheeffectoffrequencyonfatiguebehaviorsofthealloy.Afterthefrequencycorrection,theultra-highcyclefatigueS-NcurvewellcoincidewiththetraditionalfatigueS-Ncurve.