A Study On Vertical Vibration Model And Mechanism Of UCM Cold Rolling Mill

Mill vibration is a serious problem existing widespreadly to be solved during high speed rolling,which not only restricts the production efficiency,but also causes strip thickness fluctuation and chatter marks,even threatens the safety of the staff and equipment when it happens violently.Taken 1420mm UCM cold rolling mill as the research object,natural frequencies and mode shapes of the mill and work roll displacement responses with different technical parameters are analyzed.The main contents are as follows:(1)A full-scale 3D numerical simulation model of UCM cold rolling mill was established by a joint modeling of ANSYS/LS-DYNA and UG.Modal analysis was used to work roll,intermediate roll,backup roll and mill.The influence of contact and constraints on modal analysis results by comparing natural frequencies and mode shapes was discussed.It provides theoretical foundation for ensuring the frequencies of self-excited vibration in the UCM cold rolling mill.(2)Based on the 3D finite element method and influence function method,the deflections of roll stack in UCM cold rolling mill were obtained and compared by using ANSYS static algorithm and MATLAB program.A kind of contact stiffness distribution model between rolls which conforms to the bending of roll system was established.It lays a foundation of building spring-damping module in vertical vibration model of UCM cold rolling mill.(3)The mechanism of self-excited vibration and the main forms and characteristics of vertical vibration are described in detail.Based on Bland-Ford-Hill rolling force calculation model,the influence of process parameters,such as thickness,tension and friction coefficient,on vertical vibration in the cold rolling mill was obtained.(4)By utilizing contact stiffness distribution model between rolls,the vertical vibration model with mass-spring-damping was set up.The mill equivalent damping coefficient and process parameters were simulated.And the influence of them on vertical vibration was analyzed.The research suggests:the narrower of strip width,the easier vibration happens;the vibration frequency near the neck of roll is higher than the middle of the roll;The vibration of work roll is diverging when the rolling speed is 30m/s,and the main vibration frequencies are 234.78Hz and 859.38Hz.This study provides support for the quantification of the influence of process parameters on vertical vibration and the study of multi-stand coupling vibration.