The Analysis On Nonlinear Vertical Vibration Of Roller System In Rolling Mills

With the development of the speed and the intensity, it has become common that the phenomenon of vertical chatter of roller system in rolling mill. The vertical chatter is the more affection on the quality of products, some chatter can get heave amplitude in seconds, some chatter may bring in stripes of light and dark, though they did not make visible thickness difference, what affected the quality of products. So the study of vertical vibration of rolling mill has become an important object on improve the yield and quality of rolling mill.Firstly vibration analysis of nonlinear parametrically exited and 4-h rolling system of two degrees of freedom model is carried out. This model considers the nonlinear damping and nonlinear stiffness between working rolls. The parse approximation close to the main frequency, ultra harmonics and inferior harmonics parametric resonance are worked out using multiple-scales method. At last, the curve equation of amplitude-frequency characteristic. The stability characteristic is analyzed. The affection of each parameter on the vibration is solved by simulation analysis. With the change of nonlinear stiffness, the amplitude appears the jumping phenomenon. It leads instability of the vibration. The validity of the method is validated using numerical simulation.Secondly a vertical nonlinear parametrically exited coupling vibration model of 4-h rolling system is established, which considered the nonlinear damping and nonlinear stiffness between working rolls and supporting rolls to rolling mill's frame, The parse approximation solution under main frequency, 1:1 inner resonance are carried out by using multiple-scales method, and the curve equations of amplitude-frequency are obtained. The vibrational characteristic of system under nonlinear stiffness and nonlinear damping are analyzed. With the change of nonlinear stiffness, the amplitude appears the jumping phenomenon. It leads instability of the system. The numerical simulation indicated that the solution is validated. Local bifurcation is studied with parameters transform.Third third-harmonic chatter and five harmonic chatter models are established according the theory analyze, through analyzing the origin of the third harmonic chatter and fifth harmonic chatter. It analyzes the third harmonic chatter and fifth harmonic chatter through numerical simulation. The validity is validated though simulation at last.Last the testing system has been established through the testing project of 1780 hot rolling mill of one steel company. The vibration dates were taken by Y-D vibration sensor. It uses the LabVIEW of NI company to show and memory the vibration information. It took the new signal transacting method EMD to analyze dates and make Hilbert transformation. It achieved the aim of taking internal information and decomposition.