Theaimofthisresearchistocharacterizethedevelopmentoffatiguedamagebymeansofstress-strainhysteresis.Experimentswereconductedon14specimensmadeofcold-finishedunannealedAISI1018steel.Resultsdemonstratethatthemechanicalhysteresisloopareas,whenplottedasafunctionofthenumberofloadingcycles,showsignificantvariationsanddemonstratethethreeprincipalstagesconcerningtheprogressofthefatiguefailure—initialaccommodation,accretionofdamageandterminalfailure.ThesethreestagesoffatiguearemarkedbythetransitionsatcyclesN2andN3.ExperimentalresultsshowthatalthoughfatiguelifeNfrangesfrom2644cyclesto108992cycles,theratiosofN2/NfandN3/Nftendtobestable:N2/Nf=10.7%,N3/Nf=91.3%.
