Rigid-plastic finite element analysis of profile ring rolling

Abstract

The ring rolling process is incremental and involves three-dimensional non-steady metal flow and continuous change of radius and thickness of the ring workpiece. Difficulties may arise in attaining the full profile at the required final dameter and the improvements in profile filling are generally achieved by altering the blank shape and adjusting rolling conditions, by experience or by trial and error. Therefore an efficient simulation method is required, by which side spread and cavity filling can be predicted accurately. At any instant of the ring rolling jprocess the deforming region is restricted near the roll gap and the remainder of the ring workpiece remains nearly as a rigid zone. To save computation time, only the ring segment around the roll gap is analysed by introducing the boundary conditions given by the kinematics of ring rolling operation. The idle rotation of the pressure roll, which is one of the important features of the ring rolling process, is taken into account in formulating the proplem by taking the peripheral velocity of the pressure roll as an unknown variable of the funtional when the ring rolling process is analysed under the plane strain condition. It has been found that frictional conditions at the roll-ring interfaces have a relatively small influence on the computational results of the strain rate distribution, normal pressure distribution, roll separating force and driven roll torque. The approximation of frictionless pressure roll is shown to introduce only slight differences in the above-mentioned computational results because the pressure roll is idling and dissipates only negligible energy by bearing friction. When the pressure roll is treated as frictionless, the computation time is much reduced especially in the three-dimensional problem as compared with the case which does consider pressure roll friction. Ring rolling of plain rings without axial constraint has been simulated by the three-dimensional rigid-plastic finite...