Research On Vertical And Horizontal Nonlinear Vibration Of Asynchronous Cold Rolling

Exploring the occurrence mechanism and instability mechanism of vertical and horizontal vibration of asynchronous cold rolling under the influence of nonlinear factors is the key to improve the rolling precision and rolling efficiency.Aiming at the problem of asynchronous cold rolling vibration,this paper analyzes the asynchronous rolling conditions where the upper and lower work rolls have the same roll diameter and different speeds.Through theoretical analysis and numerical simulation,the mechanism of vertical and horizontal vibration of asynchronous cold rolling under the influence of nonlinear factors is investigated.The research results can provide a theoretical reference for vibration reduction and suppression of asynchronous cold rolling and improvement of the rolling precision.First,the vertical flutter and forced vibration model of asynchronous cold rolling under the influence of damping,clearance,speed and different speed ratio are established.Single parameter bifurcation characteristics and kinematic characteristics in the dual parameter domain are obtained by numerical simulation.It is clear that vertical flutter is more sensitive to rotational speed than vertical forced vibration,and the parameter domain of vertical forced vibration for periodic motion is larger than the range of vertical flutter.Under the premise that vibration is inevitable,vertical forced vibration in the actual system is easier to control than vertical flutter.Secondly,the upper roll system of the asynchronous cold rolling mill is simplified by high pair and low generation,and the horizontal nonlinear vibration model induced by vertical vibration is established.Through the investigation of the 1/2 subharmonic resonance characteristics of the system,it is clarified that the change of the system parameters will lead to the increase of the bandwidth of the amplitude frequency resonance region,the increase of the resonant amplitude value,the multi-value property and the shift in the resonance region.Increasing the first-order damping and cubic stiffness can reduce the resonant amplitude.Increasing the excitation parameters of the vertical displacement will lead to an increase in the resonance region bandwidth and an increase in the common amplitude value.According to Melnikov theory,the chaotic motion analysis is performed to obtain the necessary conditions for chaotic motion of the system,which provides a theoretical reference for the prediction of actual rolling instability.Further,the single parameter bifurcation characteristics and dual parameter domain motion characteristics of horizontal nonlinear vibration induced by asynchronous cold rolling vertical vibration with and without elastic deformation are investigated separately.With the change of parameters such as displacement excitation parameters and squashing deformation parameters,the system exhibits dynamic behaviors such as period doubling bifurcation,periodic motion and chaotic motion,and obtains parameter matching value ranges for periodic and chaotic motion.The system's attractor and attraction domain transition process are investigated separately with and without elastic deformation.It is found that the periodic attractor and chaotic attractor coexist in the case of inelastic deformation.The system's periodic attractor and chaotic attractor are central symmetrically distributed in the case of elastic deformation.The evolution mechanism of horizontal nonlinear vibration induced by vertical vibration is revealed.Finally,the movement characteristics of asynchronous cold rolling in the vertical equilibrium state are analyzed,and the free movement,contact movement and collision movement of the vertically moving parts between equilibrium positions are discussed.Through numerical simulation,the dynamic behavior transition mechanism such as bifurcation,period and chaos during collision motion and corresponding parameter domains are clarified.