Out of roundness distortion of bearing rings owing to internal stresses from tube bending

Abstract

The out of roundness distortion of bearing rings owing to relaxation of internal stresses was investigated experimentally and numerically. Internal stresses in the rings were owing to bending of the tubes from which the rings were produced. This three point bending operation can be regarded as an idealised tube straightening operation. Bending is a typical deformation mode in real tube straightening. The experiments and simulations included the following steps: three point bending of tube, ring turning, and soft annealing heat treatment (also representing the heating in a hardening operation). The ring distortion was measured after ring turning and after soft annealing. A considerable out of roundness was found in both steps but the major contribution was owing to the elastic deformation of the ring at the final stage of turning when the ring was cut off from the tube.