Radially loading rotary extrusion for manufacturing large-size conical cylinders with inner transverse high ribs

The Large-size Conical Cylinders with Inner Transverse High Ribs(LCCWITHR) can reduce the weight of the parts while maintaining high rigidity and strength. Radially Loading Rotary Extrusion(RLRE) forming technology can achieve integral forming of LCCWITHR through the synergy of radial and rotary movements of dies. The flow law of the material during the forming process is the key to forming large-size inner ribs. At present, there is no unified understanding of the metal flow law of RLRE forming technology. An analytical expression was derived to predict the Radial Direction(RD) deformation loads. The FE simulation and process experiment were carried out to investigate the effects of the inclination angle, thickness factor and transition arc radius of the split top dies on the spacing of the metal diversion plane, the metal flow velocity of the rib area and the final radius of the inner rib. The influence of the split top dies loading distance and the bottom die rotation angle of each pass on the inner radius of the inner rib was verified. And the optimal combination of dies shape parameters and loading paths which can make the metal flow orderly was obtained: the inclination angle is 140°, the thickness factor is 3.64, the transition arc radius is 16 mm;the top dies loading distance is 15 mm, the bottom die rotation angle is 45°.The FE simulation results have been found to be in close agreement with physics experiment.The research results reveal the metal flow law of rib growth in the RLRE of LCCWITHR, which lays a theoretical foundation for subsequent thorough research and process optimization.

TRANSITION TO TAYLOR VORTEX FLOW BETWEEN ROTATING CONICAL CYLINDERS

Transition to Taylor vortex flow between two conical cylinders,with the inner one rotating and the outer one stationary,is studied by the numerical method in this article.It is found that the basic flow becomes unstable with increasing of Reynolds number（Re ） above a certain critical value Rec =117 and with the further increase of Re to about Re=300,the first stable vortex is formed near the top of the flow system.The annulus is filled with six pairs of vortices at about Re=800.These are confirmed by experimental observations.Moreover,the local extreme values of pressure and velocity are reached at the adjacent lines between neighboring vortices or at the medium lines of large vortices.The local minimum values of velocity and the local maximum values of pressure are reached at the same point,whereas the local maximum values of velocity of the flow are assumed at the point of inflection for pressure.

A numerical investigation of the flow between rotating conical cylinders of two different configurations

The flow between two coaxial conical cylinders is numerically studied for two different configurations, with the inner cone rotating and the outer one at rest. It is found that, in one configuration,at least at a small Reynolds number（Re）, the pressure is a decreasing function of z while in the other configuration, it is an increasing function of z. In the first configuration, the pressure curves for different Re have intersections, while in the second configuration they do not. The gap between two conical cylinders is filled with six pairs of Taylor vortices at about the same Reynolds number and in each pair of vortices in the first configuration, the upper vortex is larger than the bottom one while in the second configuration, the bottom vortex is larger than the upper one.