Understanding friction in boundary lubrication remains a major challenge in tribology. The common assumption is that, in this regime, friction mainly originates from direct asperity contact in the boundary layer once the lubricant film becomes extremely thin. But is this solid body contact really the dominant mechanism, or could the shearing of ultra-thin lubricant films inside asperity contacts still control friction behavior?
In our very recent OpenAccess publication in Lubricants, we explore this question by combining contact mechanics simulations (BEM) with a pressure-dependent limiting shear stress model:
https://doi.org/10.3390/lubricants14030125
By simulating a lubricated two-disc contact and comparing the predictions with experimental results for different base oils, we investigate whether boundary friction can be explained by the limiting shear stress of thin lubricant films within the contact.
The results suggest that boundary friction is best described by a combination of lubricant rheology, represented through the limiting shear stress and solid body contact at highly loaded asperities. This helps bridge the gap between classical asperity contact models and fluid-based friction descriptions and may support more physically grounded friction modeling for lubricated MachineElements.
