The critical assessment for the fatigue limit of nanocrystallized surface with micro-notches obtained by ultrasonic surface rolling processing

摘要

The fatigue limits of micro-notched specimens with nanocrystallized surface fabricated by ultrasonic surface rolling processing (USRP) are determined at room temperature. Two kinds of metal materials of specimens, IF steel with single ferritic phase (body-centered cubic, BCC) and 316L with single austenitic phase (face-centered cubic, FCC), are selected. The experimentally determined fatigue limits of micro-notched USRP specimens, with and without stress relieving treatment, are both much higher than that of coarse grain specimens due to surface hardening and compressive residual stress. Furthermore, it is verified that the predicted value from Murakami's model agrees well with the experimental value of not only the coarse grain specimen but also the specimen with nanocrystallized surface if the surface Vickers hardness is selected.