Research On Isothermal Forging Numerical Simulation And Precision Controlling For Bevel Gear

Isothermal forging is a kind of advanced net-shape forming technology, which is applied to forge parts at a relative low strain rate, meanwhile billet and die is at the same or similar temperature. This technology can significantly improve materials’ plasticity, even make materials reach superplasticity to form complicated shape part once, which has some advantages, such as lower forming force, higher material utilization, lower residual stress, more precise and so on.This paper took a bevel gear of the differential mechanism as the research object and carried out numerical simulation for the gear of the isothermal forging forming process using DEFORM-3D software. The main works include Flow behavior and constitutive description of 20CrMnTi steel at high temperature, design of isothermal forging process, numerical simulation and analysis of isothermal forging for bevel gear and precision control research of bevel gear for isothermal forging.The isothermal compression tests of 20CrMnTi were performed using a Gleeble-3500 thermo-simulation machine to obtain stress and strain data at high temperature deformation. According to the experimental results, the Arrhenius-type constitutive equation model and the Zener-Hollomon parameter of the exponent-type were employed to establish the constitutive equation of 20CrMnTi. In addition, the compensation of strain was taken into account and a new method of modifying the constitutive model was proposed by introducing a coefficient K related to temperature and stain rate in this paper, which effectively improved the prediction accuracy of the developed constitutive equation.Then, by analyzing manufacturability of bevel gear, isothermal forging forming scheme was determined, which included drawing forging figure, calculating the press tonnage and choosing equipment, material calculation and blanking, heating, lubrication and heat treatment, design of die structure.Then, a number of numerical simulations were carried out to investigate the distribution of stress and strain, forming force, the law of metal flow and the filling. The orthogonal experimental method was employed to study the influence of some factors on the prediction load, which include ratio of height to diameter of billet, thickness of punching recess, position of punching recess, deformation temperature and velocity. Finally, taking the prediction load as the optimization objective, a set of optimum technology parameters were obtained. In addition, this paper analyzed the influence on die wear of temperature, velocity, hardness and friction factor, meanwhile analyzed the effective stress distribution of die at the end of forming.Finally, by researching the elastic deformation of die under working and prestress status, and analyzing the elastic recovery of bevel gear, the die cavity was modified using the compensation method. Meanwhile, taking the heat factor that effects the precise of forgings into consideration, another precise controlling method was proposed, which is simple and more suitable for practical production.