Effect of steel anisotropy on contact pressure and stress distribution in dry and lubricated point contacts: A case study with measured material properties

On a macroscopic level, bearing steel behaves isotropic all due to the aggregate effect of many anisotropic grains. However, the effects of material anisotropy on the local scale of a contact zone between rolling element and raceway may be significant for the pressure at the surface, the subsurface stresses, and for the lubricant film, particularly in extreme conditions of heavily starved contacts. Multigrid techniques were shown to allow numerical simulation with the dense grids needed to represent 3D material consisting of grains with varying crystallographic orientation. In earlier work, this was shown for grains generated by Voronoi tessellation with randomly varying orientation. Here, we demonstrate the capability of computational diagnostics using local orientation angles and phase composition of 100Cr6 (ASTM 52100) bearing steel, obtained from electron back scatter diffraction (EBSD) analysis of a ring near-raceway sample. For a circular contact under dry and elasto-hydrodynamically lubricated conditions, it is shown that the variation of the crystallographic orientation, effectively forming a variation of stiffness of the grain in load direction, leads to stress concentrations between grains with the larger differences in orientation angles. The developed algorithm can be used for criticality evaluation of measured subsurface topological/crystallographic structures and optimization.