Just another doubt: as far as I understood, any fatigue analysis (both stress-life and strain-life) presupposes a linear elastic behaviour in the 1st starting cycle although, eventually, plastic local deformations might appear through the cycle (in strain-life low-cycle fatigue). Right?

But, what happens when small plastic strains already appear in the 1st cycle? Is it still applicable the fatigue analysis? The same way and with the same considerations/conclusions?