Abstract:

ESDU 87007 gives a procedure for the selection of bearing materials for use in applications in which a film of fluid cannot be maintained. The range of commercially available materials for journal or thrust bearings is covered, but the procedure can be applied with care to dry rubbing bearings of any configuration. As a preliminary step, the requirements on the bearing must be specified (type of motion, loading, required life, environment). Then, against a series of criteria, particular materials are systematically eliminated from consideration. First the required clearance is established, which depends on thermal expansion, and expansion due to water absorption. The environment (water, oil, acid, alkali, vacuum or radiation) is considered, and materials eliminated for incompatibility, and for failure to meet requirements on permissible bearing pressure/operating temperature, limiting rubbing speed or working temperature range. The wear rate of the remaining materials under operating conditions (including surface temperature for which a calculation method is included, and allowing for the roughness of the mating material) is established for comparison with the allowable rate to meet the required life. Finally, data on relative costs allow a choice to be made on that basis from the candidate materials remaining, and a list of manufacturers is included so that price and delivery may be readily established. A worked example, for a journal bearing application, is used to illustrate each step in the procedure.