Study On Vertical-Horizontal Coupling Nonlinear Vibration Characteristics Of Strip Rolling Mill Under Mixed Lubrication

The industrial is developing at a high speed in our country,and the development direction of steel rolling is gradually developing towards high-speed and high-quality,but the vibration problem of the rolling mill has always existed.The state of lubrication and friction in the rolling interface is complicated when steel rolling,and it has a great influence on the quality of the product.In this paper,the lubrication friction model between the rolling interfaces is considered as the mixed lubrication friction model,and the nonlinear vibration model and dynamic rolling force model of the rolling mill system under the state of mixed lubrication friction are established.Regarding the thickness of the lubricating oil film as a variable,it establishes a connection with the vibration model of the rolling mill and the dynamic rolling force,and conducts in-depth research and analysis on this.The main contents of this paper are as follows:(1)Based on the Karman differential equation of unit pressure,the friction model is replaced with a mixed friction model.According to the assumption that the rolling pressure is approximately linearly distributed,the dynamic rolling force is calculated.Considering the structure of the rolling mill system,a single degree of freedom vertical vibration model of the roll is established.The multi-scale method is used to solve the vibration model,an amplitudefrequency equation is obtained.Finally,the numerical simulation is carried out by using 1780 rolling mill parameters,the primary resonance frequency characteristics and bifurcation characteristics of the vertical vibration are analyzed.(2)Considering the influence of the horizontal vibration of the roll on the oil film thickness,based on the average flow Reynolds formula,the lubricating oil film thickness is deduced and calculated,and the dynamic expression of the lubricating oil film thickness is obtained.(3)Considering the influence of the horizontal vibration of the roll on the oil film thickness,the dynamic oil film thickness expression is solved.Considering the vertical and horizontal vibration of the roll and the geometry of the deformation area,based on the Karman differential equation,the dynamic rolling force in the vertical and horizontal directions is calculated by integrating the rolling pressure.A vertical-horizontal coupled vibration model of the rolling mill with three degrees of freedom is established connecting with the thickness of the lubricating oil film.The multi-scale method is used to obtain the vertical and horizontal amplitude-frequency equations.Using 1780 rolling mill parameters for simulation,the time-domain response curve and the amplitude-frequency curve when the primary resonance of the system occurs in both the steady state and the unsteady state are analyzed.