Abstract: With four-high plate mill as an example, two nonlinear constraints that are segmented elastic force and friction force of hydraulic screw-down cylinders and bending cylinders in rolling mill roll system vibration are analyzed, the model that nonlinear roll system vibration under the nonlinear constraint action from hydraulic cylinder is established, and amplitude-frequency response of the vibration system is obtained by using average method. The behavior characteristic of roll system under the action of segment elastic force and friction force is studied by analysis of vibration curves under the function produced by two kinds of nonlinear factors. The law of amplitude-frequency characteristics of roll system influenced by two kinds of nonlinear factors respectively is studied by taking different segmented elastic force and friction force. The results show that vibration speed is affected by the magnitude of elastic force, the instability frequency area is wider with increases of segmented elastic force increasing, and the influence on the vibration behavior of the roll system turns damping into nonlinear with friction force increasingly. This conclusion provides a theory reference for roll system vibration control.

Key words: amplitude-frequency characteristic, hydraulic cylinder, nonlinear constraints, roll system