Search

This article investigates the effect of temperature on the lubrication and wear behavior of a grease-lubricated spherical roller bearing (SRB) assuming mixed-elastohydrodynamic lubrication (mixed-EHL) where the contact load is shared between the lubricant film and contact asperities. Temperature effects on internal load distribution and elastic modulus and their subsequent effect on the wear are also analyzed. The effect of temperature is investigated, first on the film thickness and load sharing, and then on the friction and wear. If the temperature rises from ambient to 110 °C, the increase in the contact patch dimensions, due to the decrease of elastic modulus, is only approximately 1% and the decrease in mean contact pressure is approximately 2%. Moreover, the load at ψ = 0 ° decreases by approximately 4%, and the load zone increases by approximately 5%. As the temperature rises from 50 to 110 °C, the asperity portion of the contact load at ψ = 0 ° position is increased by 350%. At 50 °C, only 20% of the total traction is contributed by the contact asperity, which is 80% at 110 °C. For the temperature rise from 50 to 110 °C, the wear volume loss increases by 238% and nonlinearly, due to viscosity reduction and its effect on the reduction of film thickness. The isolated change of internal load distribution and elastic modulus due to temperature rise causes a relatively insignificant change in wear. Hence, the predominant effect of temperature rise on wear is due to a decrease in lubricant film thickness causing the asperity component of the contact load to increase. [ABSTRACT FROM AUTHOR]

This work presents an approach for modeling grease-lubricated bearing wear by coupling models for boundary-lubricated wear and bearing lubrication state. The lubrication model takes a mass balance approach, using previously developed models for pressure-driven side flow loss and centrifugally driven bleed supply mechanisms. These are combined with a contact model to determine the level of surface interaction and the impact that this interaction has on the lubricated wear and friction coefficients. The developed model was used in numerical simulation of the wear over time during operational conditions representative of 2 Mkm travel distance of a passenger train and the results were compared with experimental investigation of wear particles collected from field test lubricating grease. The results suggest nonlinear behavior with an increasing wear rate over time. Comparison between model results and wear volume estimated from collected wear particles is inconclusive and requires further investigation. A sensitivity analysis of the wear rate found that early in life the model is most sensitive to parameters that directly influence contact properties (load, boundary-lubricated friction coefficient, and wear coefficient). At later stages this shifts as parameters that affect the lubricant loss and supply mechanisms (temperature, base oil viscosity, lubricant fill) become equally or more important. [ABSTRACT FROM AUTHOR]

This study presents a novel and non-destructive method for quantitatively analysing grease lubricated bearing wear by using X-ray microcomputed tomography (μCT). The efficacy of μCT to measure rolling contact wear via wear debris analysis was demonstrated, as was quantifying grease contamination and wear debris identification. Test rig experiments of grease lubricated spherical roller bearings, were performed to simulate rolling contact wear. Six grease samples were collected from two bearings at three different intervals to investigate wear progression. Results showed μCT measured wear volume increased exponentially with increasing bearing operation times. Grease cleanliness (particle counts per ml) worsened nonlinearly due to the exponential growth of wear debris over longer bearing operational times. Comparing the conventional ISO281 bearing assembly and operating condition assessment, a particle-count based method via μCT analysis provided a less subjective and dynamic assessment for quantifying grease contamination. Grease contamination was found to increase with longer operational timeframes due to the combination of wear debris growth and decreased lubrication film thickness. Finally, laminar, chunk and spherical wear particles, associated with rolling contact wear, were identified by the morphometric parameters measured by μCT. This study highlights the potential of μCT as a wear monitoring and grease quality assessment technique for railway bearing applications. • Microcomputed tomography is pioneered to measure wear in test rig bearings. • The proposed method is nondestructive and requires no sample manipulation. • The efficacy in wear measurement is proven through debris analysis in grease. • Quantitative analysis of 3D wear debris images provides wear mechanism assessment. • Grease contamination worsens with wear debris growth exponentially and lubricant film thinning. [ABSTRACT FROM AUTHOR]