Friction-reducing properties of grease in plain bearings

The lubrication mechanism of grease is not clearly defined, and the early view was that only the base oil plays a lubricating role in grease, while the thickener only plays a storage role. However, studies under different test conditions have led to different conclusions, and this paper describes the friction-reducing effect of grease in sliding bearings. The researchers used soap-based greases in bronze-steel plain bearings as a test, which was carried out at a load of 3.781kN at 37.8°C. The effect of grease composition on friction reduction was examined, and the frictional torque of plain bearings lubricated with various grease samples was measured at different journal speeds, and a sharp rise in frictional torque was used as a marker for the change to a mixed lubrication boundary. The frictional torque was measured at different journal speeds and the sharp rise in frictional torque was used as an indication of the change to mixed lubrication boundary.

The lower the journal speed or the smaller the friction torque at a certain speed, the better the friction reducing properties of the grease. The test results show that soap in the lubrication of grease not only plays a role in oil storage, but also plays a role in friction reduction, soap-based grease than its base oil friction coefficient is low.

Soap-based grease composition on the friction reduction of the impact of:

1, the influence of the viscosity of the base oil: the viscosity of the base oil increases, the friction torque decreases;

2, the impact of soap concentration: in the boundary lubrication conditions, soap concentration increases, the friction torque decreases;

3, the impact of the type of thickener: the impact of the type of thickener on the friction, researchers have experimented with different metal soap thickened with the same base oil made of grease, in the bronze steel bearings for experiments.

As a result, in the boundary lubrication that is low speed area, grease are better than the base oil, a variety of grease friction torque difference is very large. For example, greases thickened with lithium soap have a much lower frictional torque than aluminium-based greases, with calcium and sodium-based greases in the middle. These results are representative of the range of variation in other types of grease. In addition, similar results have been obtained in bearing tests with steel-to-steel or pasteurised alloy-to-steel.

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