Dynamic Characteristics Of Boring Bar System With Dynamic Vibration Reduction Based On Regenerative Factor

In the field of mechanical processing,how to reduce the vibration and chatter generated in the cutting process has been one of the key issues of concern.One of the research focuses of the vibration reduction boring bar system is to explore the influence of dynamic parameter changes on the nonlinear characteristics and vibration reduction performance of the boring bar system.In this paper,the regeneration factor is introduced,and the nonlinear effects caused by the damping fluid and the rubber ring in the system are considered.The dynamic model of the two-degree-of-freedom vibration-damping boring bar system and the dynamic model of the three-degree-of-freedom vibration-damping boring bar are established.Based on the bifurcation chaos theory and numerical simulation method,the influence of dynamic parameter changes on the nonlinear characteristics of the two boring bar systems is studied.The specific research contents are as follows :Considering the nonlinear effects of regeneration factors,damping fluid and rubber ring,the dynamic model of two-degree-of-freedom vibration-damping boring bar system and the dynamic model of three-degree-of-freedom vibration-damping boring bar system are established by using the lumped mass method.According to Newton method and Lagrange equation,the vibration differential equation of the system is obtained,and the state equations of the two boring bar systems are obtained by dimensionless processing.Aiming at the two-degree-of-freedom vibration-damping boring bar system,the change of nonlinear dynamic characteristics of the system under specific parameters is studied by using the numerical simulation results of system bifurcation diagram,Poincaré map and phase diagram,and the stability of the system is analyzed by using the maximum Lyapunov exponent diagram.The research shows that the vibration amplitude of the system suddenly increases greatly,resulting in a sudden decline in system stability.As the frequency continues to increase,the system exhibits Hopf bifurcation,periodic doubling bifurcation,inverse periodic doubling bifurcation and other bifurcation behaviors.When the frequency is greater than the main frequency doubling,the system is dominated by periodic motion.When the stiffness coefficient of the rubber ring,the mass of the vibration absorber and the damping coefficient of the damping liquid are small,the system exhibits Hopf bifurcation,anti-periodic doubling bifurcation and periodic bubble structure.When the stiffness coefficient of rubber ring,the mass of vibration absorber and the damping coefficient of damping fluid are large,the system is dominated by periodic motion.It is found that in practical application,the vibration of boring bar can be reduced to a certain extent by selecting high density vibration absorber and damping fluid.The effects of different sizes of rubber ring stiffness and different sizes of regenerative cutting force on the bifurcation characteristics and stability interval of the two-degree-of-freedom system are studied.It is found that when the dimensionless stiffness of the rubber ring is equal to 0.05 and 0.15,the system undergoes multiple bifurcations and transits between periodic motion,quasi-periodic motion and chaotic motion.The unstable interval is large and the vibration amplitude is relatively large.When the stiffness is equal to0.1,the system is dominated by periodic motion,only a quasi-periodic window appears,the stability interval is large,and the vibration amplitude is small.When the regenerative cutting force coefficient is equal to 0.03,the bifurcation characteristics of the system are more complex,and Hopf bifurcation,periodic mutation and other behaviors appear.The bifurcation characteristics when the regenerative cutting force coefficient is equal to 0.01 and 0.05 are not as complex as that when the regenerative cutting force coefficient is equal to 0.03,but the larger the regenerative cutting force coefficient,the larger the unstable interval of the system.It can be seen that the complexity of the bifurcation characteristics of the system is not proportional to the size of the regenerative cutting force,but the larger the regenerative cutting force,the larger the unstable interval of the system.The nonlinear dynamic characteristics of the three-degree-of-freedom damping boring bar system under specific parameters are studied.It is found that with the change of four dynamic parameters,Hopf bifurcation,periodic doubling bifurcation and periodic bubble structure appear in the system,and periodic motion and quasi-periodic motion are dominant,and chaotic motion is rare.In addition,the bifurcation characteristics of the three-degree-of-freedom vibration-damping boring bar and the two-degree-of-freedom vibration-damping boring bar under the same parameter conditions are compared.It is found that the three-degree-of-freedom vibration-damping boring bar system does not have complex nonlinear behavior and the vibration characteristics are more stable.