Influence of non-Newtonian fluids on the performance of a soft elastohydrodynamic lubrication contact with surface roughness

Abstract

The paper focuses on the development and results of a numerical model to evaluate the fluid transfer behaviour for non-Newtonian fluids in a rough soft elastohydrodynamic nip contact. The solution required coupling of the fluid and elastomer regimes, with a multi-gridding technique to facilitate the high mesh densities required to capture the rough surface representation. The non-Newtonian fluid behaviour was modelled using a power-law model. The study evaluated circumferential and longitudinal roughness forms. The introduction of longitudinal roughness introduced significant shear in the nip with the resultant large change to the viscosity profile. This also removed the stagnation point in the centre of the nip. The longitudinal roughness had a large impact on the film thickness and flow through the nip while the circumferential affected the local performance of the nip but not its overall pumping capacity.

Mixed lubrication of soft contacts: An engineering look

“…[38][39][40][41] These models are particularly useful for treating the contact of hard materials. 27,28,42,43 For the soft materials, the deformation of the asperities is generally elastic and the original GW model provides reasonable results as documented in Kim et al, 21 Bohan et al, 22 and Guo et al 23 Accordingly, in the current study, we utilize the GW model as an engineering approach to evaluate the behavior of surface asperities in soft EHL.…”

“…14,15 Within the context of mixed EHL, the modified Reynolds equation by Patir and Cheng 16 has been utilized in soft contacts to predict the changes in the lubricant flow due to the surface roughness. [17][18][19] For modeling the behavior of asperities, the statistical micro-contact model by Greenwood-Williamson known as GW 20 has been used in some studies, [21][22][23] while the fractal models have been utilized in some other studies. [24][25][26] In the present study, the line-contact mixed elastohydrodynamic lubrication of soft materials is studied.…”

A computational homogenization framework for soft elastohydrodynamic lubrication

“…In order to form a thin channel, a flat surface L u + is placed at a distance h above the mean plane of the rough surface L u − . For this purpose, introducing The former assumption is particularly convenient because it allows a static analysis and is a common starting point in many works [1,2,4,11,15,18,28,41,42,62]. In contrast to this setting, two rough surfaces moving against another or accounting for tangential contact demands a time dependent analysis [49,52,55,72,80].…”

“…Consequently, making use of the macroscopic identifications for the flux (sec 7.2.2) and the pressure gradient (sec 7.2.3), preservation of dissipation across the scales requires satisfying 15) which will be referred to as the micro-macro dissipation equality. The satisfaction of this equality is guaranteed by the periodic boundary conditions employed in this work [78] and therefore the thermodynamical consistency of the computational homogenization approach is guaranteed.…”

“…finite deformation, elasto-hydrodynamic lubrication. The multiscale problem in the context of elasto-hydrodynamic lubrication has been investigated in Bayada et al [11], Bohan et al [15], Dowson [27] and explicit numerical solution strategies for the coupled problems of elasticity and lubrication have been proposed [45]. Although finite deformation effects have also been investigated in Shi and Salant [66], Shinkarenko et al [67], Stupkiewicz and Maciniszyn [72], a sufficiently general computational homogenization framework that takes into surface texture evolution effects due to large macroscopic deformations of the lubricated interface appears not to have been proposed.…”