An evaluation of the effect of simulated launch vibration on the friction performance and lubrication of ball bearings for space applications

Abstract

Ball bearings in space mechanisms are subjected to vibration during launch which can lead to a temporary loss of contact between the balls and the raceway. On re-establishing contact the transient high contact stresses which arise may cause damage to the bearing. This transient loss of contact is referred to as “gapping”. Despite the fact that it is clearly of interest to understand how exposure to the launch vibration impacts upon bearing and lubricant performance, the dynamic behaviour of bearings subjected to vibration typical of that occurring during launch has been little studied. This paper describes a theoretical and experimental investigation to examine the influence of simulated launch vibration on the torque performance of solid and liquid lubricated ball bearings. A fixture containing a pair of preloaded face-to-face angular contact bearings was mounted on an electro-dynamic vibrator. Two laser triangulation transducers were used to measure the relative axial displacement of the bearing components at a range of acceleration levels. A simple analytical model was also developed to predict gapping for a range of different test conditions. Data from this model was compared to measured gapping. The effect of vibration on bearing torque was measured following each level of acceleration. Finally, features arising in the bearing raceway due to vibration testing were assessed.