A system is referred to as a sliding bearing in which the relative movement between the shaft and the bearing or an intermediate medium is a sliding movement. Depending on the perspective, plain bearings can be classified differently. Three most common groups are briefly presented below:
Classification according to the lubricant
Classification according to the functional principle
Classification according to the direction of force
Depending on the medium and parameters, different friction states occur in plain bearings, such as radial plain bearings:
These friction conditions can be defined using the Stribeck curve. They also serve to classify wear and lubrication. The Stribeck diagram shows the coefficient of friction versus the lubrication gap height. In an oil-lubricated system, a radial plain bearing passes through the main friction states of boundary friction, mixed friction and fluid friction, depending on the sliding speed and load. Solid friction does not occur in oil-lubricated systems, since in this case of tribocontact at least 1-molecular layers always occur. In addition to the Stribeck curve, the upper part of the figure also shows the dependence of wear on the friction conditions.
Federal-Mogul Deva GmbH exclusively produces self-lubricating bearings with solid lubricant depots. These are mainly used for dry running, although grease, water or oil-lubricated systems can also be considered, taking certain criteria into account. As a rule, the speeds are low and the loads are so high that hydrodynamics do not take place. The friction conditions to be expected are solid friction, boundary friction and mixed friction, since a boundary lubricating film forms as a result of the solid lubricant.
The calculation bases and use of the Stribeck curve, as is the case for typically hydrodynamically running plain bearings, are therefore not applicable or expedient for self-lubricating plain bearings in practice.