Research On Virtual Ring Rolling Technology And Rolling Process Optimization

Ring rolling technology is a specialized partial plastic rolling process in which a pre-designed cross-section is formed using a rolling mill. Very often, the wall thickness of the ring is decreased with increase in the diameter. Due to its competitive advantages, such as high efficiency and low cost, this technology has been widely used in mechanics, metallurgy, energy, aerospace, chemical engineering. Nowadays, ring rolling is one of the major advanced methods for production of seamless annular-shaped components, such as bearing races, gear ring, flange ring, railway wheel, turbine ring and pressure vessel ring. The development trend of ring rolling nowadays is to achieve high productivity, precision, complexity and flexibility in production. The traditional trial-and-error method can not respond rapidly to the market change and realize the green manufacture.During the past 20 years, with the rapid development of finite element theory and the availability of commercial finite element codes, the trial-and-error approach has been replaced gradually by numerical simulation. However, the ring rolling process carries the characteristics of plate rolling, asynchronous rolling and multi-way rolling. Moreover, it also relates to the feed movement of the mandrel and the axial rolls, the rotation of the main roll, the movement of the guide rolls as well as the rotation of the ring itself with the expansion of its diameter. Therefore it is difficult to determine the metal flow process using conventional methods. Particularly, the forming process is affected real-time by the change of each roller movement, which is the main barrier in the virtual ring rolling research. To overcome this barrier and address the research focuses, the following tasks have been completed on the basis of some former research work:(1) Firstly, a numerical metal flow model for the ring rolling process was created by using the general dynamic explicit code LSDYNA. In the simulation model, the mass shrink technology was also adopted to reduce the running time, therefore the model released the general requirement of high computer performance and long computation time. Secondly, the ring rolling control process was modeled using a complex numerical simulation technique that made use of the finite element software ANSYS with APDL (ANSYS Parametric Design Language). With the real-time transfer and the modification of movement parameters, the numerical control model could overcome the difficulties in determining the unknown parameters. Lastly, the two simulation models were integrated to form a self-adjusted ring rolling finite element simulation tool (AMFE) for realizing real-time coupling simulations for both the ring metal flow and the numerical control system.(2) Based on the AMFE, the rolling process of a ring with rectangular cross-section was simulated for one complete cycle of production. The simulation results were compared with ROLLTECH experimental data reported by the German SMS Wagner-Banning company and the UBET results reported by P. V. Ranatunga. The AMFE was hence validated as good agreement between these results had been found. Moreover, the AMFE simulation also provided dynamic information on the stress, strain and displacement contours of the ring as well as the damage evolution process. Apart from many other advantages, such as high calculation efficiency and versatility, the information provided by the AMFE is very important to conduct a ring rolling process, but usually difficult to be determined experimentally. Therefore, this project is amongst the first attempt to simulate the entry ring rolling process and overcome the limitations in conventional transient studies.(3) Two optimization schemes were firstly developed and incorporated into the AMFE simulation model. One was to utilize the MATLAB neural networks toolbox to optimize the rolling process and the initial billet structure of the ring. The other one was to create the optimum model for the ring rolling process, in which the rolling time was taken as the target function and the optimization variables, the strategies as well as the process were analyzed. With the former rectangular cross-section ring being taken as the research object, the rolling process was optimized separately by using the two proposed schemes and the optimization variables were analyzed in detail. Eventually, the whole process of ring rolling was optimized with the optimum rolling process parameters and rolling billet structure found. The contributions of this research do not only create a 3D finite element model, but also provide a computational tool for optimization of a ring rolling process.(4) Further research work was conducted to study the ring rolling process of a profiled cross-section ring using the AMFE simulation model. The rolling characteristics of a profiled ring were firstly analyzed, and some solution schemes were proposed accordingly. The AMFE models for theΦ500 radial ring rolling machine and RAW200/160-5 radial-axial ring rolling machine were also created. The whole dynamic rolling process within a complete production cycle was simulated for three kinds of complex profiled rings: a rear axle bevel gear blank, an aero-engine turbine casing blank, and a great conical ring of 600MW nuclear reactor shell. The simulation results matched well with the actual production process, and thus it was proved the validity of the virtual rolling model. The method for studying the profiled ring rolling process may also be used to examine the feasibility of the profiled ring rolling process, and develop a rolling process for a new cross-section profiled ring. The deliverables of this project contribute to save the R&D cost, shorten the overall cycle time, respond more rapidly to the market requirement, and help realizing the green manufacture objective.