Fatigue strength of small-scale type 304 stainless steel thin films

This paper presents an experimental study of the fatigue strength of micrometer scale 304 stainless steel (SS) thin films using dynamic bending microbeams. The stress-life data was extended from the tests with R = 0.15 to the condition of fully reversed loading in order to compare with literature values of the bulk 304 SS. Fatigue damage process was characterized in detail. The results show that the fatigue endurance limit of the micrometer scale samples is higher than that of the bulk 304 SS. Fatigue damage was found to originate from cyclic strain localized regions within the grains. It is argued that fatigue damage behaviors in the micrometer scale 304 SS still follow that of the bulk material, but the fatigue strength has been enhanced due to the influences of both fine grain size and small geometrical dimensions.