Bearing Design Considerations

The sliding bearing, also known as a journal or sleeve bearing, is a plain shell bearing that is used to support rotating shafts or journals. These bearings are anti-frictional and have a cylindrical or semi-cylindrical bushing made from a suitable, soft material. They are generally classified into full, partial, and fitted bearings depending on the extent to which the bearing envelops the journal. A Babbitt bearing is any journal or shell bearing that is coated with a layer of Babbitt material on the contact surface. Some typical applications of journal and Babbitt bearings include automotive engines like connecting rods and crankshaft that offer high temperature, speed, as well as varying load.

Bearing Materials:

An integral part of designing a bearing is selecting the material, since the bearing materials constitute an important part in the journal bearing. This maxim is particularly important for Babbitt bearings. The materials that are chosen are especially significant when considering the beginning of the hydrodynamic lubrication process, when contact occurs between the rotating shaft and the bearing. The bearing materials must be soft enough to resist the wear and endure load under gas pressure. In addition, they must also possess good compressive and fatigue strength. While the compressive strength is to withstand the temperature variations, the fatigue strength is to resist cyclic loading of the journal when it is revolving. Finally, the material should also have a low shear strength aimed at easy smoothing of surface asperities.

Some other important considerations of the bearing materials include a low coefficient of friction, reliability, and resistance to corrosion. In addition, they must also have good thermal conductivity to dissipate the frictional heat. Considering all these requirements, Babbitt alloys are one of the most commonly used bearing materials.