Bearing cage dynamics: Cage failure and bearing life estimation

Abstract

Nowadays, given the widespread use of rolling bearings in mechanical applications, an important topic is investigate which parameters influence their wear in order to estimate the real bearing life. The cage is one of the critical element in the bearing, its dynamics is complex and nonlinear due to the intermittent contacts with various elements (e.g. balls and races) with a resulting not regular trajectory of its center that can lead to the cage failure. While the races have a simple rotational motion, the balls usually have a more complex dynamics due to the stick-slip motion and the action of the external contact forces. In this work a lumped model of the cage is presented focusing of its possible kind of motions: cage in free-flight (just inertial and Coriolis forces act on it), race contact, balls contact, race and balls contact. A numerical code is developed taking into account a three DOFs model for the cage, contacts and lubrication. The goal of this work is to identify the most important parameters influencing the motion and the life of the cage. Furthermore, some chaotic aspects in the dynamics of the bearing are investigated to understand their influence on the cage failure.