Materials for plain bearings

The main aim of this article is to provide guidelines for the bearing user when choosing an antifriction material. Due to the complexity and diversity of bearing problems, it is not possible to cover the subject exhaustively. However, if, after reading this article, the potential user possesses the main keys to defining the family of antifriction products he should use, then we would consider the objective we had set ourselves to have been achieved. For tricky problems, you'll need to contact a specialist.

Depending on the author, the term bearing can have different definitions. We'll use the ISO 4378/1 definition, which is: a support or guide that determines the position of a moving part in relation to the other parts of the mechanism. Because of the freedom allowed by this definition, we'll consider that the bearing is made up of the shaft, the housing, the antifriction material and its support, and the lubricant, as these four elements are what give the bearing unit its performance.

We have intentionally limited the presentation of anti-friction materials for plain bearings to the case of cylindrical bearings subjected to radial loads. However, most of the remarks can be applied to other types of bearing which use the same types of materials, e.g. sliding blocks, spherical thrust bearings, clutch thrust plates, etc. However, certain precautions need to be taken when extrapolating the results obtained from these materials. However, certain precautions must be taken when extrapolating the results obtained for cylindrical bearings.

There are two types of bearing: radial-load bearings and axial-load or thrust bearings.

—Radial-load bearings are generally made up of two 180°-arc elements, more commonly known as half-bearings, and one 360°-arc element, known as a bushing.

—Axial-load bearings are generally made up of half-shells (crankshaft half-shells) or complete washers.

Regardless of the type of bearing considered, it can be single-layer (e.g. a solid bronze bearing) or multi-layer (e.g. a copper-lead bearing on a steel backing). For severe applications, the properties required for the bearing to function properly are often antagonistic, and the most elegant way of getting around this difficulty is to use multi-layer materials that provide the desired properties at the core or surface.

In order to fully grasp the problems associated with antifriction materials, we felt it would be useful to devote several paragraphs to what we consider to be the basic notions, which are :

• bearing operating speeds, since these are among the most important parameters in defining a material;

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