This document specifies a method of improving test result comparability by evaluating the stresses in the bearing layers leading to fatigue (see Annex A). A similar evaluation is required in practical applications. Because the stresses are the result of pressure build-up in the hydrodynamic film, it is essential to fully state the conditions of operation and lubrication. In addition to dynamic loading, dimensional and running characteristics, the inclusion of the following adequately defines the fatigue system:
a) under conditions of dynamic loading the minimum bearing oil film thickness as a function of time and location to ensure no excessive local overheating or shearing as a result of mixed lubrication when running in;
b) the distribution of pressure circumferentially and axially with time under dynamic loading;
c) from this the resulting stresses in the bearing layers as a function of time and location, especially the maximum alternating stress.
Furthermore, bearing fatigue can be affected by mixed lubrication, wear, dirt, tribochemical reactions and other effects encountered in use thus complicating the fatigue problem. This document is therefore restricted to fatigue under full hydrodynamic separation of the bearing surfaces by a lubricant film.

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