Thin-walled Cylinder Workpiece-tool Dynamic Characteristic Matching Method And Cutting Vibration Test Research

When thin-walled cylinder workpiece is turned,due to its low relative stiffness,it is very easy to cause relative vibrations between the tool and the workpiece,which will form chatter under specific conditions and greatly reduce machining accuracy.At the same time,during the turning process,the metal material on the surface of the workpiece is continuously removed due to the simultaneous action of the main rotating motion of the workpiece and the feeding motion of the tool,which makes the dimensional parameters of the workpiece and the position of the cutting force change in real time,which means that the turning system is a time-varying system.This paper focuses on the vibration behavior of thin-walled cylinder turning under the time-varying factors and its suppression method.From the perspective of dynamics theory modeling,the effect of time-varying thickness,time-varying position and other factors are considered to analyze and study the variation law of the vibration characteristics of thin-walled cylinder workpiece turning,and according to the analysis results,the stability of the vibration system is studied and transformed into the problem of selecting the critical cutting width,and then the matching law between tool and workpiece kinetic parameters is studied in depth and optimized to improve the stability of turning processing,so that This will enable the operator to select better cutting parameters and tool parameters to avoid possible vibration problems before the actual machining.The dynamics explanation is also given based on the modal flexibility theory for the phenomenon of time-varying thin-walled cylinder surface morphology in the cutting vibration test.The main research of this paper is as follows.(1)Based on Kirchhoff-Love assumption,the vibration differential equation of the rotating thin-walled cylinder is established,the beam function method is used to solve the intrinsic frequency of the rotating thin-walled cylinder and the corresponding modal vibration pattern,and the spindle-chuck-workpiece process system model is established by using numerical simulation method,combined with the modal experiment to analyze the different wall thicknesses and cutting force positions on the intrinsic mode and frequency response function of the thin-walled cylinder cutting system The effect of different wall thickness and cutting force position on the intrinsic mode and frequency response function of thin-walled cylinder cutting system is analyzed.(2)Based on the regenerative chattering mechanism,the time lag differential equation of the two-degree-of-freedom thin-walled cylinder turning system is established,and the time lag term is processed by the analytical method to obtain the corresponding stability limit diagram.Based on the derived stability limit expressions,the influence law of different cutting parameters on the system stability is analyzed;and the relationship between the matching mode between the tool and workpiece kinetic parameters and the stability is studied,so as to provide some theoretical support for the subsequent search of the optimal matching between the tool and workpiece kinetic parameters.(3)Based on the theoretical analysis of the stability of chattering in thin-walled cylinder turning,genetic algorithm and particle swarm algorithm are used to optimize the design of the tool-workpiece parameter matching method so that the critical cutting width is maximized,i.e.,the stability of the system is optimized.And through these two algorithms compared with each other to verify the credibility of the optimization results,to assist the machinist to get the maximum stability domain under the current working conditions before the actual machining,breaking through the traditional limit of taking a small cutting amount to prevent chattering,so as to effectively reduce the actual cutting of the machine tool and tool cutting performance of unnecessary waste,improve machining efficiency and machining accuracy,and save machining costs.(4)Further verify the influence law of time-varying factors on the turning vibration characteristics of thin-walled cylinder workpiece and its turning stability by cutting vibration test,through which it is found that the chattering texture of the machined surface of thin-walled cylinder workpiece also has time-varying nature.Therefore,based on the modal flexibility theory,the harmonic response analysis of the finite element model is used to obtain the negative real part of the dynamic flexibility curves at different cutting positions,and then to determine the modal or several modal orders with large negative real part of dynamic flexibility,and to determine the main weak modal at different cutting positions by combining the modal experiments and cutting vibration experiments.The texture is intrinsically related to the inherent mode of the process system.