Research On Thermo-mechanical Coupling Simulation Of High-Speed Ball Spinning For Thin-walled Tubes

As a special plastic processing method,ball spinning technology is widely used in the production of low plasticity,difficult deformation and high quality parts because of its high quality and high precision of thin-walled tubes.In the process of ball spinning,the temperature has a very important effect on the plastic deformation of the tube blank,which not only affects the characteristics of the material itself,but also affects the final forming quality of the tube.Taking the temperature field of high speed ball spinning process as the research object,the finite element thermo-mechanical coupling model of magnesium alloy thin-walled tube was established by finite element software,and the regularity of heat generation and the controllability of temperature rise were explored,analyzed,summarized and verified.Firstly,the finite element model of high speed ball spinning was established by finite element software ABAQUS.In order to meet the actual working conditions,the model assumption,the establishment of geometric model,the definition of material properties,the selection of elements and mesh,and the setting of boundary conditions were completed.The finite element model of high speed ball spinning was established according to the actual working condition.Secondly,the temperature field distribution state of tube billet was obtained by finite element thermo-mechanical coupling simulation,and the law of temperature field change of tube billet in the process of ball spinning was obtained in the undeformed region,deformation region and formed region.The heat rising law of inner and outer surface of tube billet during high speed ball spinning was obtained.Thirdly,the ball spinning under different process parameters was simulated,and the influence laws of feed ratio,speed,thinning amount,ball diameter and friction coefficient on the temperature field in the spinning area of magnesium alloy tube were obtained.Each process parameter has a great influence on the heat generation in the deformation zone of the tube billet.The temperature of the deformation area increases with the increase of the friction coefficient,the speed,the thinning amount and the feed ratio,and decreases with the increase of the ball diameter.The thinning amount is the most sensitive to the increase of temperature.Then,through the adjustment of the process parameters and the finite element thermo-mechanical coupling simulation,it is found that the temperature of deformation zone can reach more than 220? under high speed and larger amount of thinning,which can meet the temperature requirement of warm forming of magnesium alloy.The result verified the realizability of optimum spinning temperature of magnesium alloy thin-walled tube in warm forming.And it realized the controllability of the optimum spinning temperature.At the same time,the uniformity and controllability of the radial heat generation of tube billet were studied.Finally,the dry friction coefficient and lubricating friction coefficient at different temperature were obtained by measuring the friction coefficient between ball and tube billet.The friction coefficient which is most close to the actual condition was provided for the finite element model.The temperature values of the tube billet spinning zone under different process parameters were obtained by the ball spinning temperature measurement experiment.Compared with the simulation results,the experimental results are basically consistent with the simulation results.And the reliability of finite element thermo-mechanical coupling simulation results is verified.