Study On Ball Spinning Process Of Magnesium Alloy Thin-walled Tube

Ball spinning is a powerful spinning process using ball as a deformable tool.and combines the advantages of forging,extrusion,pulling,bending,rolling,and rolling,and so on.For the ball spinning of the thin-walled tube,because the contact area between the ball and tube is smaller,it has a small deformation zone with low elastic deformation,but the stress value produced in the process of deformation is larger.So it is used to process the hard deformable thin-walled metal tube parts with high hardness and weak plasticity index,which can improve the material performance and surface quality.The criterion for judging the appropriate parameters of the deformation process is as follows: whether it can reduce the surface roughness of spinning tube,reduce the stress in spinning process,and ensure the smooth process of spinning.Therefore,the selection of process parameters is determined by the macroscopic surface finish,spinning force,microstructure and mechanical properties of the spinning tube.Based on the study of high speed ball spinning process,In this paper,an analytical model for the calculation of three-direction ball spinning force is established.The selection of the process parameters,the microstructure and mechanical properties of the magnesium alloy tube after the high speed ball spinning are tested and analyzed.The main contents and results are as follows:1)Based on the theory of spatial analytic geometry,an analytical model for calculating the ball spinning force in three direction is established,Through the spinning test to magnesium alloy thin-walled tube,the spinning force calculation model is verified.2)The influence of some key spinning parameters during spinning deformation on AZ31 magnesium alloy microstructure is explored.Through analysis of microstructure performance of spinning tube in different process parameters,to determine the optimum process parameters.The experimental results show that the microstructure of the tube is refined after spinning.Compared with the original extruded tube,the plasticity of the tube is further improved and the tensile strength is increased.When the feed ratio is 0.15mm/r,the thinning amount is 0.25 mm,the speed is 1250r/min,the diameter of the ball is 5.5mm,the surface roughness of the tube is the smallest and the microstructure is fine and uniform after the spinning.the corresponding tensile strength is the largest and the elongation is the highest.the results of the study greatly facilitate the selection of process parameters in the process of spinning production.3)Based on the BP neural network under the Matlab neural network toolbox,a prediction model of strain-stress neural network under different temperatures and strain rates is established.The BP network model is more accurate and convenient to use.It can replace the traditional stress constitutive model,which is easy to be applied to finite element simulation.