Abstract:

According to the testing parameters of a 4200 vertical mill and by using the numerical calculation com- bined with theoretical analysis, this paper proposes a nonlinear vibration model with four degrees of freedom for the main transmission system of the vertical medium plate mill. The model is simplified and is then used to obtain the responses of the linear vibration system. The numerical solutions to the nonlinear vibration equations are obtained by means of Matlab. Afterwards, the motion state of the vibration system with a vibrating angular frequency approaching to the natural one is analyzed by means of phase graph, Poincare mapping graph and time＇history curve. Finally, the motion state of the system with a vibrating angular frequency varying in the natural frequency range is analyzed to further reveal the system stability. The results indicate that, when the angular frequency increases from the first-order natural frequency, the system is instable, with a motion state changing from a periodical mode to a quasi-periodical and even a chaotic one

Key words: vertical mill, transmission system, nonlinearity, twist vibration, numerical simulation