| The elementary forming of the blank is all important in the manufacturing of the gear-shaft. To improve the utilization rate of material and save the resource and energy so as to ensure sustainable development and protect the environment is one of the key tasks in studying forming mechanism and technology. The dissertation combines the cross wedge rolling (CWR) with gears generating to form a gear blank, so that the process of the gear shaft can be simplified, the materials can be saved, the manufacture cost can be reduced and the fatigue strength, the wear resistance of the gear can be enhanced. Therefore the research has theoretical significance and application value.The CWR plastic forming technology, the plastic forming technology of gear and gear-shaft and numerical simulation technology of plastic forming are reviewed. The large deformation rigid-plastic finite element equations are introduced in detail including rigid-plastic constitutive equations and rigid-plastic finite element generalized variational principles. The related aspects such as solid element, solution of the stiffness equations, deformation and heat transfer, temperature field and thermal-mechanical couple are discussed.An innovative idea about gear-shaft CWR forming technology is proposed and studied, combining the CWR technology with meshing of the gear and rack (the patent had been authorized) . The process is discussed in detail with emphasis on the feeding of the teeth rolling, the indexing of the teeth number and the die combination of the gear and the wedge for the gear die. The theoretical and geometrical models of the CWR forming of involute gear-shaft are created. The feasibility of the CWR forming of involute gear-shaft is analyzed and the hypothesis of the kinematically admissible velocity field in the wedging zone is verified.The 2D and 3D thermal-mechanical coupled finite element models for involute gear-shaft are created, including the materials, mesh generation and regeneration, contact, thermal boundary condition, initial condition and load cases. Then the traditional load cases (total 11 load cases) are numerical analyzed. The stress and strain field, the temperature field, the filling of the die and the flowing of the material and the rolling force and energy parameters are obtained. The forming law and general deformation feature of the teeth forming are characterized with 2D simulation. The effect of the 4 design parameters (rolling temperature, teeth number, feeding mode and rolling velocity) on the rolling force is compared. The forming process of the gear-shaft is simulated with 2D and 3D methods, the deforming mechanism of the rolled parts and the effect of simultaneous forming the teeth and the shaft are demonstrated visually. Therefore the established finite element model and the simulation results are exact and effective.The undercutting phenomenon of the CWR for gear shaft is interpreted by simulation of a special load case. The critical number of no undercutting in CWR is obtained by analysis of the force and movement of the gear blank and the die. As for the odevity of the gear teeth, a rolling process of adjusting the position of the upper and the lower die is proposed and verified to roll the gear with odd teeth number. The causes of rolling flaws are analyzed with classical Material Mechanics failure theories and numerical simulation stress results.The similar environment of actual CWR rolling process is established. The forming of the gear-shaft is simulated in a lab-simulated unit, with the sculpture mud made blank to verify qualitatively part of the 2D and 3D thermal-mechanical coupled numerical simulation results and the feasibility of the CWR forming of the gear-shaft. The causes of the rolling flaws such as concavity on the end of workpiece,Mannesmann effect,spiral roll mark on the axle head and tooth roll mark etc in the lab-simulated experiment are analyzed to provide suggestion for the application of the CWR forming process of gear-shaft.
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