A UNIFIED MECHANISM OF FISH-EYE CRACK INITIATION ON THE LIFE OF HIGH STRENGTH STEELS IN THE VHCF REGIME

摘要

When structural alloys test in very high cycle fatigue loading, the location of crack initiation shifts from surface to internal and forming Fish-eye on fracture surface. The majority of fatigue life was estimated to forming this morphology. In present work, features of internal crack were studied on two high strength steels in very high cycle fatigue regime. Three types of initiation site were investigated. A unified internal crack initiation mechanism was suggested base on the understanding of dislocation slip from fundamental material. A physical based threshold was suggested to drawing the borderline between the initiation and propagation stages. The relation of internal crack initiation and slower decreasing of S-N curve was discussed.