A mixed elastohydrodynamic lubrication (EHL) model for a coated angular contact ball bearing is developed by coupling the influence coefficients with the unified deterministic mixed EHL model. Based on the bearing quasidynamics analysis, the influences of the surface roughness, coating thickness, and boundary friction coefficient on the mixed EHL performance of the coated bearing are discussed. The results reveal that high surface root-mean-square roughness can be detrimental to bearing lubrication performance and increase the risk of coating failures. Coating thicknesses on the order of a few microns have a limited effect on the contact load ratio, film thickness ratio, and friction coefficient while having a significant effect on the maximum surface tensile stress and interfacial shear stress, especially for high-friction low-speed conditions. A low-friction self-lubricating coating can effectively improve the tribological performance and prolong the service life of the bearing, especially in the bad lubrication state with severe asperity contacts.
We investigated the delamination behaviour of diamond-like carbon films on silicon nitride (Si 3 N 4 ) substrates, considering the effect of the substrates surface roughness. The damage evolution at the film/substrate interface during indentation was simulated using a cohesive zone model, and the interfacial stress and energy release were determined. We discuss the influence of asperity size, thickness and Young's modulus of the films. The results show that the interfacial roughness hastens the onset of interfacial damage but delays the progression of film delamination owing to the effect of mechanical interlocking. The asperity size and film thickness also strong influence the delamination of diamond-like carbon films.
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