Mixed lubrication of soft contacts: An engineering look

Abstract

Mixed elastohydrodynamic lubrication of materials with low elastic modulus (soft materials) is investigated. Expressions for prediction of film thickness and the asperity load ratio in soft line-contact elastohydrodynamic lubrication are presented. The traction behavior of soft contact in mixed elastohydrodynamic lubrication regime is also studied in terms of the Stribeck curves.

Influence of anisotropic surface roughness on lubricated rubber friction: Extended theory and an application to hydraulic seals

“…In a recent paper Masjedi and Khonsari [42] observe that similar results are obtained when adopting the GW contact mechanics, as obtained in the 2009 paper by Persson and Scaraggi [22], where a mean field lubrication theory was developed based on the Persson contact mechanics theory. Here we note that in Ref.…”

“…1a of Ref. [42]. This is likely due to a different numerical inlet distance adopted by Masjedi and Khonsari, which might sensibly affect the numerical results, as confirmed by the authors.…”

“…Using these equations we calculate β ≈ 2 nm and βnh rms ≈ 625, whereas the value adopted by Masjedi and Khonsari [42] are β = 0.02 mm and nβσ = 0.05. Thus, the model parameters adopted in Ref.…”

“…Here we note that in Ref. [42] two of the three roughness parameters, namely the mean asperity radius β and the asperity surface density n, where used as fitting parameters. Indeed, the authors claim that such parameters are difficult to obtain from a power spectral density [42], but in fact can be calculated as described by Nayak [43].…”

“…Thus, the model parameters adopted in Ref. [42] are orders away from those really describing the true contact system; as a result, the comparison reported in [42] have to be reconsidered, so that further clarifying research is needed on this aspect. In addition we note that a certain discrepancy can be observed also under elastohydrodynamics conditions, when no asperity-asperity or asperity-fluid interactions are relevant, reported on in Fig.…”