Vertical short-crack behavior and its application in rolling contact fatigue

The vertical short-crack behavior presented in rolling contact fatigue of medium carbon bainitic steel back-up roller under the conditions of low contact pressure, water lubrication and pure rolling were studied. The initiation and propagation behavior of vertical short-crack were traced by microscopic observation due to its observability on the surface of the specimen. It is found that after the short-crack initiates and quickly propagates to a certain depth from the contact surface, the vertical short-crack will stop propagating for a large number of cycles (from 104 to 3–5×105 cycles); however, while the number of cycles is up to the initiation life of rolling contact fatigue (about 3–5×105 cycles), the vertical short-crack re-propagates at a high propagation rate and along the circumferential direction of the specimen and parallel to the contact surface. Based on the observed un-propagating and re-propagating behaviors of vertical short-crack, the initiation life and surface distress life of rolling contact fatigue of the back-up roller was measured, and then, the mechanism of rolling contact fatigue was discussed.