Fatigue Failure of Rollers in Crankshaft Fillet Rolling

In this paper, the fatigue failure of the primary roller used in a crankshaft fillet rolling process is investigated by a failure analysis and a two-dimensional finite element analysis. The fillet rolling process is first discussed to introduce the important parameters that influence the fatigue life of the primary roller. The cross sections of failed primary rollers are then examined by an optical microscope and a Scanning Electron Microscope (SEM) to understand the microscopic characteristics of the fatigue failure process. A two-dimensional plane strain finite element analysis is employed to qualitatively investigate the influences of the contact geometry on the contact pressure distribution and the Mises stress distribution near the contact area. Fatigue parameters of the primary rollers are then estimated based on the Findley fatigue theory. The results indicate that the most of damage in the primary roller is due to the contact with the secondary roller and that the predicted fatigue initiation site is in agreement with the failure location of a failed roller. The results of the finite element analysis suggest that the fatigue lives of the primary rollers highly depend on the contact geometry between the two rollers and, therefore, an appropriate adjustment of the contact geometry can significantly improve the fatigue lives of the primary rollers.