Thin film lubrication (TFL), a lubrication regime that fills the gap between boundary lubrication (BL) and elastohydrodynamic lubrication (EHL) regimes, was proposed 20 years ago. Since it was first recorded in the literature, TFL has gained substantial interest and has been advanced in the fields of theoretical and experimental research. Following the revelation of the TFL phenomenon and its central ideas, many studies have been conducted. This paper attempts to systematically review the maj...

The stability of the tribological properties of polymer coatings is vital to ensure their long term use. The superlubricity of the poly(vinylphosphonic acid) (PVPA)-modified Ti6Al4V/polytetrafluoroethylene (PTFE) interface can be obtained when lubricated by phosphate-buffered saline (PBS, pH = 7.2), but not when lubricated by deionized water and ethanol. Therefore, the mechanisms for the superlubricity of PVPA coatings affected by lubricant were investigated in detail. The stability of the PV...

The mechanism of grease replenishment in and around a starved point contact was studied in this work. Greases made of different thickeners and same base oil were tested and compared. Disappearing and re-formation of a dynamic grease reservoir during operation revealed that grease bled oil to replenish contact. However, the replenishment process was slow because of the presence of grease fingers along the track and thickener-deposited film inside the track. The contact angles of base oil on th...

There are few experimental results available on film thickness at speeds above 5 m/s and they are almost all based on the optical ball-on-disc test rig. In contrast to the contacts in a rolling bearing, in which the lubricant in the oil reservoir distributes symmetrically, ball-on-disc contact shows asymmetry of lubricant distribution due to centrifugal effects. In order to closely imitate the contact occurring between the ball and the outer ring of a ball bearing, this study proposes an expe...

To reduce the friction of a piston ring while maintaining a large oil film load-carrying capacity, an approach comprising of the inverse method and the sequential quadratic programming algorithm was proposed. The approach considers the variation of mixed lubrication and variable lubricant viscosity with temperature along the engine stroke, is developed to optimize the profile of a piston ring. A piston ring profile is represented by a polynomial function. A case study of the second piston rin...

The effects of boundary (liquid/solid) slip on hydrodynamics are well recognized. However, it is extremely difficult to quantify in-situ boundary slip in a lubrication contact. Therefore, an effective interfacial parameter that is well correlated with the lubrication effect is of practical significance. This paper presents an examination of common interfacial parameters, including surface tension, contact angle, contact angle hysteresis, and a recently proposed spreading parameter. Spe...

Oil–air lubrication supplies lubricants in the form of droplets to elastohydrodynamic lubrication (EHL) contacts, such as those in high-speed spindle bearings. However, there is a paucity of information related to understanding the lubrication behaviors of oil droplets within EHL contacts. In this study, behaviors of lubricant droplets, in terms of spreading around a static contact as well as passing through a rolling contact, were studied with an optical ball-on-disk EHL test rig. Influences...

Thin film and elastohydrodynamic lubrication regimes are rather young domains of tribology and they are still facing unresolved issues. As they rely upon a full separation of the moving surfaces by a thin (or very thin) fluid film, the knowledge of its thickness is of paramount importance, as for instance to developing lubricated mechanisms with long lasting and efficient designs. As a consequence, a large collection of formulae for point contacts have been proposed in the last 40 years. Howe...

To further extend knowledge about fluid film friction in elastohydrodynamic contact, it is important to examine how lubricant flows. In this paper, several film thickness results obtained by interferometry technique for different kinds of experiments were analyzed and discussed based on lubricant flow continuity. Results of two steady-state and two transient experiments are presented. Possible speed profiles that can explain observed film thickness distributions were suggested. It is shown th...