Study On Dynamic Characteristics For The Damping Boring Bar System Based On Friction Energy Dissipation

Because of the acceleration of standardization process in modern manufacturing industry,there are more and more requirements on the quality of products.In the machining field,the vibration in the deep hole working reduces the quality of workpiece and seriously affects the cutting efficiency.This paper analyzes the friction factor in the friction damping boring bar system,building the dynamic model for multi-degree-of-freedom damping boring bar system by considering friction energy dissipation.The vibration characteristics of the system is studied through numerical simulation of systematic parameters.The vibration stability of the system is analyzed by the top Lyapunov exponent.According to the working principle of friction damping boring bar system,the static friction and dynamic friction of two-degree-of-freedom damping boring bar system are established based on Stribeck model and LuGre model.The system vibration equation is obtained in consider of the nonlinear vibration theory and Newton's second law.The effects of dynamic parameters on the bifurcation and chaos characteristics of the system are studied by using bifurcation map,Poincare map and phase diagram.The parameter interval of the system's stable vibration is obtained by the top Lyapunov exponent.The results show that with the increase of harmonic force frequency,the amplitude of the system increases sharply around 0.4 times frequency,the system becomes instability with resonance phenomena.Subsequently,when the harmonic force frequency continues to increase,periodic motion and chaotic motion appear alternately in the system.Complex chaotic bifurcation behaviors such as Hopf bifurcation,period-doubling bifurcation and periodic bubble appear in this process.When the stiffness coefficient of the shock absorber,the damping coefficient of the shock absorber and the mass of the friction vibrator are variable,there are inverse doubling bifurcation,nested periodic bubble and other complex bifurcation characteristics appear in the system.When the friction vibrator's quality is greater than 1 times quality of the main system,the system vibration is the stable periodic motion,enhancing the vibration stability of the system.In the design of friction damping boring bar,we should select large density mass block is used for getting better damping effect.In consider of increasing the static stiffness,the three-degree-of-freedom friction damping boring bar system has been developed.A dimensionless system equation is obtained.The effects of dynamic parameters on the bifurcation and chaos characteristics of the system are studied by using bifurcation map,Poincare map and phase diagram.The results show that the system is changeable between chaotic motion and periodic motion.It is found that the system returns to a stable vibration state when the friction vibrator's quality is greater than 0.6 times quality of the main system.And under the same conditions of other parameters,comparing the damping effect about two-degree-of-freedom and three-degree-of-freedom friction damping boring bar.The results show that under the same conditions,three-degree-of-freedom friction damping boring bar does not show the complex bifurcation chaos characteristics,namely three-degree-of-freedom friction damping boring bar system is better than two-degree-of-freedom friction damping boring bar system on the damping effect.