Mechanism and force-energy parameters of a hollow shaft’s multi-wedge synchrostep cross-wedge rolling

Abstract

First, the rotation condition of a hollow shaft’s multi-wedge synchrostep cross-wedge rolling (MSCWR) is determined and the relevant influencing rule is illustrated based on a mechanical model of the hollow shaft and the theory of solid shaft’s rotation condition. The influence rule states that the increasing number of wedges increases the shrinkage rate of the hollow shaft and diminishes the rotation conditions, which can be improved by increasing μ on the forming surface of the hollow rolling mold, setting the stretching β, and forming α angles at approximately 4°–12° and 15°–35°, respectively. Second, a rigid-plastic finite element model is established for the hollow shaft with MSCWR by using the DEFORM-3D software, and the deformation mechanism of the hollow shaft is illustrated. The deformation degree of the rolling piece at the stretching stage decreases gradually from the surface to the interior of the hollow shaft, and radial compressive and transverse tensile strains interact with each other, thus resulting in an elliptic cross section of the hollow shaft. Stress field is mainly distributed in the exterior margin and then permeates into the inner part along the direction of the wall thickness, gradually transforming from compressive stress into tensile stress. Third, the influence of mechanical parameters on hollow shaft rolling is analyzed. The increased stretching angle increases the radial force, transverse force, and rolling torque and decreases the axial force. Moreover, the enlarged forming angle reduces the radial and transverse forces, while the decreased rolling torque increases the axial force. Finally, the 1:5 MSCWR experiment on the hollow shaft verifies the proposed finite element model’s accuracy. Results of the research provide a theoretical basis for the MSCWR of a precise hollow shaft.