Predicting the abrasive wear of ball bearings by lubricant debris

Abstract

Solid debris particles in a lubricant can become entrained into the contacts of ball bearings. The particles damage the bearing surfaces. This can lead to rolling contact fatigue failure or material loss by three body abrasion. This work concentrates on modelling the later process for brittle debris materials. A brittle particle is crushed in the inlet region and the fragments are entrained in to the contact. Rolling bearing contacts (because of the high degree of conformity) are subject to contact microslip. When this slip takes place, the trapped particle scratches the bearing surfaces. Repeated scratching by many particles results in substantial material removal. Although this failure mechanism is usually not as rapid as debris initiated fatigue, it is frequently important in mineral handling or desert environment rolling bearing applications. A simple model has been developed which considers the wear as the sum of the individual actions of each particle. The number of debris particles is determined by considering the volume of oil entrained into the bearing contacts and an empirically derived Ôparticle entry ratioÕ. The abrasive action of each particle is determined by the volume of material displaced during sliding and another empirical factor for the proportion of this removed as a wear particle. The predictions are compared with some experimental results. The correlation between bearing wear and the debris particle size is encouraging.

In contact observation of model synovial fluid lubricating mechanisms

“…Inlet aggregation behavior has been reported previously for suspended material in both hard [22][23][24][25] and soft lubricated contacts [26]. In this work the ability of the suspended proteins to form inlet aggregates and then pass through the contact is controlled by a combination of contact conditions (load, speed, SRR) and lubricant properties (protein concentration, size and morphology).…”

“…As entrainment speed is increased the contact inlet is fed with proteins at an increasing rate, causing the new inlet reservoir to grow and become visible. However hydrodynamic forces also increase causing a greater degree of contact evasion for smaller proteins [24]. The larger protein-aggregates which are left in the inlet reservoir require greater frictional forces to drag them into the contact [25], causing the film thickness to decrease.…”

“…Once these protein aggregates collect in the contact inlet zone the overall size may be much larger than the central contact film thickness. For hard non-complaint particles in metallic bearing contacts there is a maximum size of particle that can be entrained into a contact due to geometry [24]. This is unlikely to be a problem with protein aggregate entrainment, as these will easily deform, allowing for very large aggregates to be entrained.…”

The Adverse Effect of Steel Particle Contaminants on Fatigue Life of Grease Lubricated Ball Bearings

“…In terms of contaminant sizes (Maru et al, 2007;Dwyer-Joyce, 1999) state that the critical size is in the order of the lubrication film thickness as particles entrapped in the contact zone are causing local oil starvation, increased heating and material melting, while others report that when particles larger than the oil film thickness enter the contact zone, they cause stress peaks and permanent indentations in the raceway as they are over rolled. These stress peaks lead to a reduced life of the rolling bearing due to fatigue.…”

Cosmetic powder suspensions in compliant, fingerprintlike contacts

“…At higher entrainment speeds, the drag forces on the particles are increased, which results in a greater degree of contact evasion. 23 For the contact of interest the SM volume rapidly decreases. Therefore, fluid forces rapidly become negligible and then surface forces will dominate.…”