Fatigue life investigation of solid and hollow rollers in pure rolling contact

Solid and hollow cylindrical rollers in pure rolling contact have been modeled using the finite element package, ABAQUS, to study the stress distribution and the resulting deformations in the rollers' bodies when the two rollers are subjected to a pure normal loading or to a combined normal and tangential loading. The tangential loading is one third of the normal loading value. Then the Ioannides-Harris fatigue life model for rolling bearings has been applied on the ABAQUS numerical results to investigate the fatigue life of the solid and hollow rollers. Using the fatigue life of the solid rollers as the reference fatigue life, the relative fatigue lives of hollow rollers have been determined. Different percentages of hollowness between 20% and 80% have been studied. For each of these hollowness percentages, two cases were studied---when the two rollers in contact are hollow and when one hollow roller is in contact with a solid roller. This study included two main models, Model 1 where the two cylindrical rollers in contact are of the same size and Model 2 where the two rollers in contact are not of the same size. Investigations have been made for five different materials, CVD 52100, Carburized steel, VIMVAR M50, M50NiL and Induction-hardened steel.; The estimated relative fatigue lives of hollow rollers showed a great improvement of the fatigue life compared to solid rollers under the same loading conditions. This was a result of decreasing the contact stresses in case of hollow rollers due to the flexibility of the hollow roller and the increase of the contact patch width. Factors affecting the optimum percentage of hollowness have been studied, and it was found that the optimum percentage of hollowness ranges between 50% and 70%. Increasing the hollowness more than the optimum increases the flexibility of the system and reduces its load carrying capacity and decreases the fatigue life by increasing the effect the bending stresses on the inner surface which increase the contact stresses.