Study On Bifurcation And Periodic Vibration Of Rolling Mill's Main Drive System Under Mixed Lubrication

The steel industry plays an important role in our country's economic development.Rolling is an important process in steel production.The frequent torsional vibration of the rolling mill's main drive system affects the operation of rolling mill equipment and the quality of rolled products,restricting the development of rolling technology.It is not conducive to the development of our country's economy.So it has great practical significance to explore reasons for the torsional vibration of the rolling mill's main drive system.The rolling mill's main drive system is a very complex nonlinear system,which is composed of an electric drive system,a mechanical system and a rolling process.The stability of the system is affected by above parts.In this thesis,the rolling mill's main drive system is used as the research object.The lubrication during the rolling process is considered.A non-linear torsional vibration model of the rolling mill's main drive system is established.The nonlinear dynamic behavior that causes torsional vibration is studied.Firstly,on the basis of mechanical parameters and electrical parameters,according to the theory of rolling mill lubrication,the friction stress model of the rolling working area under mixed lubrication is obtained.Then the rolling torque under the mixed lubrication state is obtained.Based on Newton's second law,the dynamic equation of the rolling mill's main drive system under mixed lubrication is establishedSecondly,the Jacobian matrix of the system is obtained by analyzing the equilibrium point of the system,and the characteristic equation of the system is obtained.With the adhesion coefficient as the bifurcation parameter,the Hurwitz criterion is used to calculate the necessary and sufficient conditions for the Hopf bifurcation of the system,and the type of bifurcation of the system is analyzed.In order to control the bifurcation of the system,a washout filter containing linear and non-linear terms is introduced for the rolling mill's main drive system.The influence of the linear part of the controller on the position of the bifurcation point of the system is studied,and the influence of the nonlinear part of the controller on the bifurcation type of the system is studied.Finally,the periodic response of the system under the action of external excitation is obtained by using the incremental harmonic balance method.By comparing with the Runge-Kutta numerical integration method,the calculation accuracy of the incremental harmonic balance method is verified.The change of the 3 superharmonic resonance behavior of the system with the variety of the amplitude of the external excitation force and the adhesion coefficient are studied.The amplitude-frequency response curve when the main resonance of the system occurs is obtained by the incremental harmonic balance method,and the change of the vibration amplitude and resonance domain of the system is studied when the external excitation force amplitude and adhesion coefficient change.This provides a certain theoretical basis for suppressing the torsional vibration of the rolling mill.