Advances in thin film lubrication (TFL): From discovery to the aroused further researches

Abstract

Thin film lubrication (TFL) is known as a mode of fluid-film lubrication regime bridging the gap between elastohydrodynamic lubrication (EHL) and boundary lubrication (BL). Since the first recorded literature published in 1995, TFL has become one of the landmarks in the development of lubrication theory over the last twenty years. This article presents an overview of the advances in the research of TFL regime. We first begin with a brief introduction of the discovery of the phenomenon, followed by the discussion of the relevant essential aspects, such as the performing approach, theory and physical model. The state-of-the-art studies on both the theoretical and experimental fields are also presented, also latter with emphasis on the review of researches in several promising applications. thin film lubrication, film thickness, ordered structure, interface Citation:Ma L R, Luo J B. Advances in thin film lubrication (TFL): From discovery to the aroused further researches.

Thin film lubrication in the past 20 years

“…Surface forces are finally determined as a function of the separation of two back-silvered atomically smooth mica surfaces in crossed-cylinder geometry, as shown in Fig. 4 [49,52]. Interference fringes can be obtained between the two sliver mirrors, with white light going through an optical multilayer.…”

“…Molecular spectroscopy, including Raman spectroscopy, infrared spectroscopy and so on, is recognized to be quite efficient in achieving the in situ detection of lubricant molecular structures. The facilities constructed by introducing spectroscopy in the tribosystems have been demonstrated to be powerful enough to detect the ordering and orientation of lubricant molecules and the change in chemical bonds during the shearing process [52]. Using infrared spectra, Cann and Spikes [67,68] have explored the chemical reaction and composition of lubricants during sliding, as shown in Fig.…”

“…They suggested that such excellent film formation abilities of emulsions with ultra-low oil concentrations can be attributed to the tenacious wetting oil nanolayer on the solid surfaces. [52,125] Attempts to effectively reduce friction can be retrospect to antiquity. Superlubricity has been always a great concern, since it was proposed by Hirano and Shinjo [123, 124] around 26 years ago.…”

On the Relation between Friction Increase and Grease Thickener Entraining on a Border of Mixed EHL Lubrication

“…The friction increase could be caused by the increase in lubricant viscosity due to the tapering gap between surfaces [22,23] or due to the pressure ripples caused by the entrance of surface asperities to the contact area [24,25]. Other possible explanations could be based on the change of molecules ordering in the lubricant [26]; also due to the change of the lubricant flow in the contact area [27,28] or at the contact area inlet.…”

Structural Superlubricity Based on Crystalline Materials

“…For example, single‐crystalline solid–solid incommensurate contact interface was used to achieve structural superlubricity, liquid superlubricity by surface fluid molecules serving as tribological buffer layer, and dynamic superlubricity via mechanical modulation of the normal load and lateral force were proposed. Due to the many intriguing physical phenomena observed and great potential applications, there have been a few excellent reviews in this field …”