Nonlinear Dynamics Analysis Of Rolling Mill System

The plastic processing of most metal materials is completed by rolling mill.Therefore,rolling process is very important in metallurgical industry and national economic production.With the advancement of technology in recent years,the people have higher requirements for the appearance of the products and the comfort of using the products,which places higher demands on the level of the rolling mill rolling process.The problems that occur in rolling mills are also being focused on more and more,with the vibration problems of rolling mills receiving the most attention.The vibration produced by the mill will make scratches on the surface of the rolled parts,and more serious will also produce different shades of stripes,resulting in product quality decline,affect the quality of the rolled parts.Therefore,it is an urgent problem to analyze mill dynamic behavior and maintain mill stable operation.This paper mainly focuses on the characteristics of the vertical vibration system of the mill,as well as vibration suppression aspects,analyzed a variety of factors affecting the vibration of the mill,and carried out related research,the main research content is as follows:Firstly,by analyzing the structure and force characteristics of the mill roll system,it is considered that the hydraulic cylinder and the balance cylinder are segmental to the restraining effect of the mill roll system.The upper roll system is taken as the object of study,and a single-degree-of-freedom segmented nonlinear dynamics model of the mill roll system is established.Then the amplitude-frequency characteristic equation of the system is solved approximately.Through the analysis of the amplitude-frequency characteristic of the system,the effects of the primary term stiffness coefficient,the tertiary term stiffness coefficient and the damping coefficient on the amplitude-frequency characteristic of the system are found respectively;The effects of amplitude and damping on the dynamics of the single-degree-of-freedom system were found,and the bifurcation behavior in the single-degree-of-freedom system was mainly based on multiplicative bifurcation.In view of the vibration of the mill,the displacement of the roll in the vertical orientation and the influence of the mechanical structure of the mill on the roll system,a two-degree-of-freedom nonlinear vertical vibration model considering the dynamic rolling forces is established,and the differential equations of the system are established using Newton’s second law,and the equations are solved using the multiscale method.The two-degree-of-freedom mill system is simulated by MATLAB software,and the influence of external excitation frequency on the dynamic behavior of the system is found.By changing the dimensionless parameters,the complex bifurcation behavior is found to exist in the two-degree-of-freedom system,which mainly contains multiplicative bifurcation and Hopf bifurcation.The composition of the machine system is very complex,and the system also contains a large number of nonlinear factors.Considering the influence of nonlinear factors in the system on the vertical vibration of the system,a four-degree-of-freedom nonlinear vertical vibration model containing nonlinear damping and stiffness is established.Newton’s second law is applied to analyze the dynamics model,and the corresponding differential equations of the nonlinear dynamics are obtained.The simulation of the four-degree-of-freedom vertical vibration model is carried out by MATLAB software,and the bifurcation behavior of the system under the action of external disturbance force is studied.It is found that Hopf bifurcation is easy to occur in the four-degree-of-freedom system,and some parameters in the steady state of the system are obtained by combining the time course diagram,phase diagram,cross-section diagram and spectrum diagram,which provides some theoretical reference for the optimal design of the mill system.