Dynamic Modeling Of Thin-walled Workpiece Mirror Cutting And Optimization Design Of Damping Boring Bar

Thin-walled workpiece is characterized by high specific strength,good tensile strength,light weight and space saving.They are widely used in nuclear energy,aerospace,chemical,etc.However,Thin-walled parts are prone to process distortion and vibration during the cutting process because of its low rigidity and high elastoplasticity.Therefore,the conventional manufacturing method for cutting thinwalled workpiece is difficult to ensure the processing quality,and the processing efficiency is low.The mirror cutting method is a new process for thin-walled workpiece.The process system consists of an external turning tool,an internal round mast,a thinwalled workpiece and the fixed support structure.During machining,the external turning tool and the internal boring bar are simultaneously cutting the thin-walled working surface,which offsets the radial cutting force of the workpiece.At present,it has been applied in the actual production of thin-walled cylindrical shell,but relevant theoretical research is still scarce.In this paper,theoretical research is carried out on the mirror cutting method of thin-walled workpiece.First,study the dynamic model of mirror cutting vibration;econdly,study the mirror cutting chatter problem and prediction of cutting stability;Finally,for the weak-link internal boring bar which is easy to vibrate in mirror cutting,the vibration damping structure is designed and the design parameter optimization are carried out for the purpose of improving dynamic stiffness and cutting stability.The main contents are as follows:(1)Based on the state space method of modern control theory,a dynamic modeling method for multi-input and multi-output double-dynamic cutting system is proposed.A mirror cutting vibration dynamics model of external turning,internal boring,flexible workpiece and boring bar was established.The dynamic simulation of the cutting process of the mirror cutting system was realized and verified by comparison with the experimental signals.(2)Aiming at the problem of machining stability caused by chatter of double-tool mirror cutting,based on the dynamic model,the amount of time-delay of the chatter is introduced into the inner and outer machining surfaces,and the mirror-cut chatter model is established.The state transition matrix is constructed by the semi-discrete method,and the stability of the mirror cutting system is determined according to the Floquet theory.Stable lobe graph of the mirror cutting system is plotted,and the stability of the cutting process is predicted to provide a basis for the reasonable selection of cutting parameters.(3)For the boring bar in the mirror cutting system,the cutting stability is analyzed by the transfer function method.A spring-damped absorber damping damper that significantly increases the dynamic stiffness is designed.And optimize the design parameters and material properties of the damping boring bar for the purpose of improving the stable cutting width.The Ansys Workbench is used to establish the 3D solid model of the damping mast,and the optimized design is carried out to obtain the design parameters of the damping boring bar with optimal cutting stability.The optimized cutting width range of the damping boring bar is significantly increased.