Development and evaluation of friction models for chatter simulation in cold strip rolling

High-speed rolling and high reduction usually are desirable as increase mill productivity in the cold strip rolling. However, most often, these conditions lead to the creation of chatter vibration which has a significant effect on the price of the rolling products. Experimental results show that friction conditions play an important role in the chatter. In this research, in order to stimulate chatter in tandem cold strip rolling mill, a new friction model has been provided based on unsteady mixed lubrication. In addition, chatter modeling has been done based on the simple friction models of Coulomb and Tresca. The friction model of Tresca has been simulated both linearly and nonlinearly, and work roll flattening and strain hardening effects have been undertaken as well. From the viewpoint of four output parameters, i.e., chatter critical speed, dominant frequency, rolling force, and rolling torque, the simulation results have been compared with experimental data taken from an industrial two-stand tandem rolling mill. Also, a parametric study on the effect of some of the major characteristics of rolling lubricant on the four output parameters is conducted. The key result of the research is that unsteady lubrication model, much better than simple friction models, can simulate friction conditions governing the chatter phenomenon.