Abstract: The study compares machined brass and pressed steel bearing cages, focusing on their impact on bearing life and performance. It highlights that international standards like ISO 281:2007 and ISO 16281:2008 consider subsurface contact fatigue but do not account for cage material. Surface fatigue, often exacerbated by poor lubrication and contamination, is a significant cause of bearing failure, particularly in steel cages.

Introduction: Bearing designers prioritize resistance to depth-initiated fatigue, but surface fatigue has become more critical due to improvements in bearing steel quality. The study emphasizes the importance of cage material in mitigating surface fatigue, with brass cages offering better resistance to adhesive wear compared to steel cages.

Rolling Contact Fatigue: The document discusses two types of contact fatigue: depth-initiated and surface-initiated. Depth-initiated fatigue is less common and occurs under long-term stress, while surface-initiated fatigue is more prevalent due to surface distress and inadequate lubrication. Contaminant particles can exacerbate surface fatigue by creating stress risers.

Basic Cage Designs: The study outlines different cage designs, including full complement, machined brass, and window-type steel cages. Machined brass cages are preferred for their resistance to wear and ability to maintain lubrication, while steel cages are lighter and cheaper but more prone to adhesive wear.

Bearing Damages Due to Cage Failure: Cage failure can lead to damage in other bearing components. Causes include vibrations, excessive speed, blockage, and wear. Steel cages are particularly susceptible to adhesive wear, leading to smearing and potential catastrophic failure.

Kinematics of the Rolling Element-Cage Contact: The document explains the kinematics of bearing operation, particularly under moderate speed conditions, where simple kinematical relationships can predict internal speeds. It highlights the importance of understanding these dynamics to prevent excessive wear and failure.

Skewing in Roller Bearings: The document discusses the skewing and tilting motions in roller bearings, particularly in misaligned bearings. Skewing occurs due to friction forces at the roller ends, leading to additional motions beyond the primary rolling motion. The skewing angle is influenced by the clearances between rollers and cage pockets or guide flanges.

High Accelerations and Skidding: At high speeds, the mass of rolling elements in bearings causes additional internal loads, leading to skidding, especially under light loads. Skidding results in reduced cage speed and can cause damage to raceway surfaces. The document highlights the importance of maintaining adequate load to prevent skidding and smearing.

Gyroscopic Motion: In ball bearings with non-zero contact angles, gyroscopic moments can cause sliding motion, particularly in high-speed applications with oil-film lubrication.

Cage Dynamics and Impact Forces: The dynamics of cage impacts are modeled considering cage stiffness and roller-race traction forces. The document describes the use of Hertzian contact theory and finite element analysis to assess impact loads and stresses. It emphasizes the importance of appropriate stiffness models to accurately simulate cage dynamics.

Load Distribution: The load distribution in bearings is influenced by static loads and centrifugal forces. The document provides equations for calculating load distribution and highlights the role of radial load, rolling elements, and contact stiffness.

Roller-Race Traction Force: Traction forces in the orbital direction affect roller speed and are influenced by resistance forces, pressure distribution, and sliding forces. The document provides equations for calculating these forces.

Experimental Validation: Experimental measurements validate the simulation models for roller-cage impact forces, showing increased impact forces with decreased radial load.

Measures to Avoid Adhesive Wear and Smearing: To prevent adhesive wear and smearing, the document recommends selecting cage materials with low friction coefficients, improving lubrication, and treating surfaces to reduce friction. Brass cages are highlighted for their resistance to adhesive bonding compared to steel cages.

Conclusions: The document concludes that while international standards focus on subsurface contact fatigue, surface-originated failures are significant. Brass cages offer better resistance to adhesive wear, potentially extending bearing life even under poor lubrication conditions.