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The additive chemistry of some gear lubricants can have a major impact on the surface durability of rolling element bearings (1). Lubricant formulation has been slanted heavily toward protecting gear concentrated contacts from galling and wear. As such, much of the performance differentiation of lubricants has been dependent on highly accelerated, standardized laboratory tests related to gears. Methods have been proposed to evaluate and quantify a lubricant's performance characteristics as they relate to rolling element bearings (2). Results from several lubricant performance evaluations are presented. The implications of these findings suggest that the detrimental performance effects on rolling element bearings need further fundamental study by the lubricant industry.

The aspects of real engineering surfaces are discussed with regard to their three-dimensional nature. A review of potential uses of surface finish measurement methods is discussed for characterization of functional surfaces. Using an optical-based system and a set of specific measurement procedures, two functional surfaces with different roughness were analyzed to illustrate a typical surface topography evaluation. A simple sliding test was then utilized to show that a special finish produced by a proprietary finishing process can provide improved performance, as measured by wear differences, frictional properties and operating temperature of the system. A special surface treatment was then evaluated in conjunction with the special finish in order to enhance its functional load support. Simple sliding test results indicates a potential new engineered surface for improving tribological contact performance.

Lubricant formulations and lubricant additives have been slanted heavily toward protecting gear concentrated contacts from galling and wear. Much of the performance differentiation of these lubricants has been dependent on highly accelerated standardized laboratory testing. The area of contact fatigue has played a less important role in shaping lubricant formulations, but new test results for several commercially available gear lubricants suggest this area warrants a closer examintion. The implications of these findings for equipment applications are discussed, and suggestions are made for ways to minimize or avoid potential detrimental performance effects.

Lubricant formulations and lubricant additives have been demonstrated to have a major impact on the surface durability of rolling element bearings. However, there are very few standard tests used to assess the performance aspects of lubricants as they relate to bearing surface performance. Lubricant formulations have been slanted heavily toward protecting gear concentrated contacts from galling and wear. In addition, much of the performance differentiation of lubricants has been dependent on highly accelerated, standardized laboratory tests related to gears. Methods have been developed for properly evaluating a lubricant's performance characteristics as they relate to bearings. These methods are explained and the corresponding test results are reviewed, to show their effectiveness as lubricant performance evaluation tools.

Debris particle contamination in lubricants has been identified as a major cause of premature bearing and gear failure, with accompanying costs in equipment downtime, warranty, and lost productivity. Various experimental and predictive methods have been developed to assist the design engineer in analysis and development of equipment that is less sensititive to such contamination. This paper provides an overview and new data comparing bearing life test results and predictive analysis methods for various tapered roller bearings operating under debris-contaminated conditions. As a baseline, some past work in these areas is briefly summarized and referenced. Recent work has refined one analytical method (using a surface characterization technique), correlated this method with bearing test lives in debris conditions, and pointed to design and manufacturing modifications in the bearings themselves, making the bearings live longer in debris-contaminated environments.

The aspects of real engineering surfaces are discussed with regard to their three-dimensional nature. A review of potential uses of surface finish measurement methods are discussed for characterization of functional surfaces. The use of an optical-based system and measurement procedures are discussed as a means of differentiating surface roughness and its texture of functional surfaces by surface engineering parameters. Using an optical-based system and a set of specific measurement procedures, two functional surfaces with different roughness were analyzed to illustrate a typical surface topography evaluation. A simple sliding test is then utilized to show that a special finish produced by a proprietary finishing process can provide improved performance, as measured by wear differences, frictional properties and operating temperature of the system.

A debris-contaminated lubrication environment is inherent in many equipment applications and requires mechanical components that, as much as possible, are resistant to the potential detrimental effects of debris particles. In addition, lubricants are formulated with chemistry targeted to prevent wear in mechanical systems, and standard tests are used to evaluate the lubricant's ability to impact this failure mechanism. However, many researchers and lubricant specialists often overlook potential relationships between the various failure modes and the engineering solutions that are created to overcome them. The role played by lubricant additives and debris-contaminated lubricants in the failure mechanisms of bearings is just one example requiring closer consideration. Performance evaluation results of tapered roller bearings in the areas of material fatigue and wear in connection with lubricant contamination and lubricant chemistry will be discussed.

Many lubrication environments in various equipment applications are inherently contaminated with debris and require mechanical components that are, as much as possible, resistant to the potential detrimental effects of debris particles. Many design engineers and lubricant specialists often overlook potential relationships between the various component failure modes, lubricant debris contamination level and the engineering solutions that are created to overcome them. Various methods for evaluating the effectiveness of debris resistant bearings have been proposed for development. Some of these methods have become standard methods within each bearing manufacturer's organization. Using an experimental method, performance evaluation results of tapered roller bearings in the areas of material fatigue will be discussed. The potential performance advantages will be placed in context of understanding the performance needs in the application.

Predicting fatigue performance in concentrated contacts under thin film (or mixed) lubrication conditions has historically involved various empirical approaches. Typically a lubrication parameter is used in an experimentally derived equation to predict the expected rolling contact performance. However, this model doesn't explain the performance improvements. Enhanced finish bearings have exhibited longer life than standard finish bearings, especially when bearings are operated with thin EHL film. In this paper, the contact surfaces of test bearings were analyzed by using a micro-macro contact model in which the macro-contact was elastic contact, and the micro-contact was elastic-plastic contact. The interior subsurface stress maps were calculated from the real contact surfaces, which included the effects of roughnesses, waviness, and profiles.