The effects of the thickener structure and base oil viscosity on the grease film formation in rolling point elastohydrodynamic contacts have been discussed on the basis of direct observation using the optical interferometry technique. Three different types of diurea greases without additives have been used as test greases. As the base oils three kinds of ether-type synthetic oils having similar molecular structures but different viscosities were used. The film behaviour of fresh greases has also been compared with that of the degraded greases. It has been found that the behaviour of grease elastohydrodynamic lubrication films is basically influenced by the thickener structure and base oil viscosity. The adhesion or deposition of the thickener on the contacting surfaces and oil starvation which affect film formation depend on the thickener structure, base oil viscosity and rolling speed. Furthermore, it has been suggested that there is an optimum temperature which gives a maximum film thickness acc...

Effects of a thickener structure on grease elastohydrodynamic lubrication films

Film thickness in grease lubricated slow rotating rolling bearings

Film thickness in a grease lubricated ball bearing

Grease-lubricated bearings often show a sharply fluctuating temperature signal. At the start of the bearing operation the temperature rises. This is generally ascribed to grease churning. This phase takes approximately 2–5 h. After that the temperature usually reaches a quasi-steady-state value. Quite often, this situation is not maintained and the temperature signal typically shows “events,” characterized by periods where the temperature rises significantly and falls back to the “steady-state” value after some duration in time. The time intervals between the events and their duration vary significantly throughout a single bearing test. Moreover, this signal varies markedly for individual bearings tested under the same conditions with identical grease. This article gives an analysis of the temperature and relative film breakdown time series signals from various tests using the concepts of nonlinear dynamics and chaos. The analysis demonstrates that the embedding dimension of the system for the group of be...

On the Chaotic Behavior of Grease Lubrication in Rolling Bearings

The ability of grease to generate elastohydrodynamic (EHD) films has been studied and interpreted in terms of the response of grease structure to contact conditions. For most liquid lubricants, EHD film thickness depends upon the rheological properties of the fluid in the contact inlet. This mechanism is reasonably well understood for fluids that are Newtonian in behaviour. However, greases have complex bulk structures, the scale of which is larger than the dimensions of a contact inlet. The EHD performance of grease must therefore depend upon the response of grease structure to the high-shear inlet conditions. In this study, EHD film thickness has been measured for a range of greases using optical interferometry. In parallel work, grease structural changes have been monitored directly in the inlet of EHD contacts using reflection-absorption infrared spectroscopy. By using these two approaches in combination, changes in composition and loss of bulk grease structure have been observed and correlated with the ability of greases to form films under EHD conditions.

https://iopscience.iop.org/article/10.1088/0022-3727/25/1A/020/pdf

The behaviour of greases in elastohydrodynamic contacts

The lubricant film thickness of grease-lubricated, cylindrical roller thrust bearings was measured, using a capacitance type displacement probe. For comparison, the same tests were also performed with the bearings lubricated with mineral oils. The film thickness and friction torque as a function of rotational speed were determined both under fully flooded and starved lubrication conditions. The test results show that the lubricant film thickness in grease-lubricated bearings is influenced by the base oil, and the thickener. Presented as an American Society of Lubrication Engineers paper at the ASLEIASME Lubrication Conference in Minneapolis, Minnesota, October 24–26, 1978

H. J. R. Gloeckner

Papers

Elastohydrodynamic Lubrication of Grease-Lubricated Rolling Bearings