Research On The Metal Forming On Bi-Spherical Cross-section Of Ring Rolling

Bi-spherical cross-section rings are widely used in applications such as bearing ring and birfield constant velocity joint cage with unique features such as demanding higher precision for inside and outside dimensions and tolerances. The traditional method in making Bi-spherical cross-section ring shape is through mechanical processing. In this thesis, ring rolling methods are used instead. The ring rolling technology is a new way to produce seamless rings with high quality and efficiency good working environment, less material waste, low production cost.Currently, many a research achievement has been accomplished in simple rectangular cross-section ring production in both theory and practice. However, as for irregular cross-section ring production, many technical difficulties are still awaiting to be solved. Therefore, the most attractive aspect in ring rolling technology is direct rolling to form special cross-section shapes. This thesis studies bi-spherical cross-section of Ring Rolling using various methods including theoretical study, numerical simulation and experimental approach. A brief introduction to the project and its main results are as follows:Based on the rectangular section ring rolling theory, a bi-spherical cross-section ring force and energy model was built, and a force and energy equation was properly conducted. Considering material deformation characteristics of Bi-spherical cross-section ring process, the study consisted of two phases, the pressing and after-pressing stages of the idle roll, and expressions for each rolling process were conducted, such as expressions for outer diameter growth, wall thickness and cross-section variations, diameter expansion rate, and rolling time, while a guider roller control method was developed.Based on studies on bi-spherical cross-section ring rolling process parameters, bank size, appropriate range of idle roller feed speed and rolling time were determined. Effects of different ring blank sizes on metal flow, stress and strain and effects of feed velocity and rolling ratio on ring transverse deformation, stress and strain for same blank sizes. The results show that the maximum rolling force, effective strain and axial metal displacement increase as the rolling ratio increases. When the ring ratio is fixed, the rolling stress and effective strain increase as the idle feed rate increases. On the other hand, as the idle feed rate increases and the axial displacement reduces, the ring face smoothes.Bi-spherical cross-section rings were successfully formed from rectangular blanks using D56G90 CNC-precision rolling mill. Effects of different feed rates on transverse deformation at inner and outer perimeters were carefully observed.