Influence of crowning on rolling contact fatigue strength and failure mode of steel roller

The rolling contact fatigue of crowned rollers made of bearing steel SUJ2 was investigated with a two-roller test machine under a sliding-rolling contact condition with oil lubricant. The nominal crowning radii of the rollers were 110 mm, 90 mm and 60 mm. The roller was mated with a noncrowned roller or a roller with a concave crowning radius of 110 mm. The contact pressure and subsurface stress were analyzed with three dimensional FEM. Within the applied load in this experiment no edge loading or minor edge loading occurred in the crowned rollers mated with the non-crowned roller and major edge loading occurred in the crowned rollers mated with the concave crowned roller. In case that no edge loading or minor edge loading occurred, the failure mode of the rollers were pitting caused by surface cracking and the rolling contact fatigue strength evaluated with the normal load increased with increasing crowning radius. In case that the edge loading was great, the failure mode of the rollers tended to be spalling caused by subsurface cracking and the influence of the crowning radius on the rolling contact fatigue strength was little.