I.C. Faraon

Stribeck Curve for Starved Line Contacts

This paper discusses a mixed lubrication model in order to predict the Stribeck curve for starved lubricated line contacts. This model is based on a combination of the contact model of Greenwood and Williamson and the elastohydrodynamic (EHL) film thickness for starved line contacts. The starved solution to be implemented in the EHL component is obtained by using numerical data of Wolveridge, who computed the starved film thickness for smooth line contacts. Calculations are presented for different oil supply layer thickness over roughness values (hoil/s). For values of the oil layer thickness over roughness ratio larger than approximately 6, the Stribeck curve and separation between the rough surfaces do not change compared to the fully flooded situation. If the oil layer thickness over roughness ratio is in the range of 6 down to 0.7, friction starts to increase and the film thickness decreases. When the oil layer thickness over roughness ratio is less than approximately 0.7, the Stribeck curve tends to transform into a straight line and separation stays at the same value as in the boundary lubrication regime. Comparison between measurements and calculations is made and a good agreement is found.

Stribeck Curve for Starved Concentrated Contacts

This paper discusses a mixed lubrication model in order to predict the Stribeck curve for starved lubricated line contacts. Themodel is an extension of themixed lubrication model of Gelinck and Schipper [1]. In order to build the starved Stribeck curve model, the contact model of Greenwood and Williamson [2] and the EHL film thickness for starved line contacts making use of the assumption of Johnson et al. [3] is combined. The starved solution to be implemented in the EHL component is obtained by fitting numerical data of Wolveridge et al. [4] who computed the starved film thickness for smooth line contacts. Calculations are presented for different oil supply layer thickness over roughness values. For values of oil layer thickness over roughness ratio (h oil/σ s) larger than approximately 6, the Stribeck curve and separation do not change. If the oil layer thickness over roughness ratio is in the range of 6 to 0.7 friction starts to increase and the film thickness decreases. When the oil layer thickness over roughness ratio is less than approximately 0.7 the Stribeck curve tends to transform into a straight line and separation stays on the same value as in the BL regime.