The Influence of Certain Raceway Dent Geometries (3-D) on Contact Stresses and Rating Fatigue Life of Rolling Bearings

Abstract

With hard metal balls of 1 mm diameter, small indentations are pressed into the inner ring of a 6205 deep groove ball bearing in the middle of the track. Running the bearing over a short period of time, under a suitable load causes the dents to change shape. The deformed dent shape is theoretically transposed to a particular 7205B angular contact ball bearing geometry in the middle of its running track, and the possibility of theoretical 3-D analysis is explored. As a first step, pressure distributions in the ball-raceway contacts are calculated with a theoretical 3-D model, with due consideration of the indentations. This is followed by computation of subsurface stresses by means of another mathematical 3-D model. Finally, fatigue life is analyzed by integrating a fatigue (survival probability) function over the endangered volume in the inner ring, using a general 3-D model featuring a fatigue stress limit. As observed in experiments with similar dents, reported in the literature, the analysis predicts considerable reduction in fatigue life. Also, the maxima of fatigue stress and fatigue function are predicted in the experimentally observed region of initiation of failure.