The Prediction And Control Of Precision Turning Deformation For A Pure Iron Thin-walled Shell

With the development of aerospace,energy and precision instruments,the use of thin-walled parts has increased significantly,and the accuracy requirements have also been improved.Because of the weak structural stiffness of the thin-walled parts,large deformation will be produced by the factors such as clamping force,cutting force and residual stress in the process of cutting,and the machining precision of the parts is often difficult to guarantee.As a difficult-to-machine material,pure iron has poor machinability,and the precision machining of pure iron thin-walled parts cannot be solved for a long time,which restricts the application and development of the related industries.Therefore,around the precision machining of pure iron thin-walled parts,the finite element simulation and other technical means are used to study the machining process and optimize the machining technology.It has important theoretical and practical value for the improvement of the machining precision of the pure iron thin-walled parts.In this paper,thin-walled revolving part of pure iron is taken as the object.In order to reveal the influence of various factors on the machining deformation and optimize the processing technology according to this,in view of the problem of turning deformation,considering cutting force,clamping force and residual stress,the finite element analysis and cutting experiments are adopted to study the problems of the deformation in the turning process of the thin-walled revolving part.The specific research work is as follows:Based on large general finite element software ABAQUS,the elastic contact model of workpiece and fixture is established,and the clamping deformation of the thin-walled shell of pure iron is predicted.With minimum clamping deformation under the same clamping condition as the goal,different clamping schemes proposed are optimized.Considering the different profile of locating plane,the clamping deformation when locating plane has flatness and parallelism error is analyzed,and the corresponding improvement suggestions are put forward.The key technology of metal cutting simulation is studied.On the basis of this,a simulation model of three-dimensional thermomechanical coupled cutting is established.The cutting process of continuous chip forming of pure iron is simulated,the cutting force and the residual stress in the process are predicted.Based on the simulation results,the characteristics of pure iron material cutting are studied,and the theory of cutting deformation is verified.Based on the basic principle of deformation prediction by mapping method,considering the nonuniformity of the stress field caused by the change of the related parameters in the machining process of the thin-walled complex curved surface,the non uniform residual stress field is reconstructed by multidimensional interpolation,and the prediction model of the global deformation of the workpiece under the non-uniform stress field is established.With the help of the secondary development function of ABAQUS,the model is used to predict the turning deformation of the thin-walled revoving part.The turning experiments of pure iron material are carried out.The cutting forces in the turning process of pure iron are tested by the Kistler cutting force test system.The residual stress distributions along the depth of the pure iron cutting surface are tested by the Prism residual stress testing system and compared with the simulation results.The accuracy of the three-dimensional thermomechanical coupled cutting simulation model is verified.