SURFACE CHANGES AROUND LARGE RACEWAY INDENTATIONS DURING RUN-IN OF TAPERED ROLLER-BEARINGS

The results of an experimental study are presented in which the raceway surfaces of tapered roller bearings were intentionally predented with single, large indentations. Contact stress analysis results and the observed changes in the surface near the indentations during run-in are described. Depending on indentation size, extremely high initial contact stresses are predicted at the raised shoulders surrounding the indentations. After running-in for 7.58 million revolutions at a moderate load level, these shoulder stresses drop to approximately 4.1 GPa (600,000 psi) or less. Microcracking and micropitting are observed around the indentations, corresponding to the areas of stress elevation. The microcracking develops during the first 100,000 revolutions of the run-in period, and is often observed to follow the direction of the abrasive finishing marks on the raceway surface.