Jixie qiangdu (Jan 2022)
EFFECTS OF SURFACE MICROMORPHOLOGY CHARACTERISTICS ON FATIGUE PERFORMANCE OF DOUBLE COLD EXPANDED HOLE
Abstract
Established the double cold expansion simulation model, and investigated the effects of surface micromorphology characteristics on the fatigue performance of double cold expanded holes. The double cold expansion process and fatigue life of the strengthened holes was simulated by using ABAQUS and MSC. Fatigue software. The hole wall element was selected, and the surface micro-profile of the hole wall was represented as the semi-ellips micro-notches. The S-N curve of the material is modified by effective stress concentration factor Kf, and investigated the effects of surface micro-profile on the fatigue performance of double cold expanded holes.The results show that there existed compressive residual stress layer on the hole wall after the double cold expansion process, and the fatigue life of the expanded sample was increased. With the increasing of the number of micro-notches in the hole wall, the stress concentration factor can be alleviated effectively, and stress concentration factor Kt is positively correlated with the depth-width ratio b/a and the distance-width ratio d/（2a）. The double cold expansion process can reduce the surface roughness of the hole wall by 21%～49%, which can effectively alleviate the notch stress concentration and improve the fatigue performance of the hole.
