In order to investigate the propagation behavior of an internal crack in surface treated steel, rotaing bending fatigue tests were carried out for a radical-nitrided bearing steel. The fracture occurred from a specimen surface under high stress levels, whereas a fish-eye fracture occurred under low stress levels. Consequently, <I>S-N</I> curve was duplex <I>S-N</I> one. A circular trace was observed inside the fish-eye when the fracture occurred under two-step variable stress amplitude test. It was suggested that the trace was formed by the change in stress amplitude. Moreover, from the change in the trace size depending on the stress level and the number of stress cycles, it was concluded that there is a fatigue limit for the internal fracture meaning the limit for crack propagation and most of fatigue life the internal fracture was occupied by the growth life of a small internal crack.
|Translated title of the contribution||Propagation Behavior of an Internal Crack of a Radical-nitrided Bearing Steel|
|Number of pages||7|
|Journal||Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A|
|Publication status||Published - 2005|