Study on the nonlinear stiffness variation and its effect on the dynamics of the rigid rotor-bearing system

In this paper, to obtain the nonlinear stiffness behavior of ball bearing and its effect on the dynamics of the rotor-bearing system, a comprehensive theoretical study on the typical rigid rotor system supported on ball bearings is presented, and the stiffness matrix of the rotor-bearing system is derived based on a novel mathematical model of the supported ball bearings with the contact angles as the new unknown parameters. Then the change rules of the nonlinear stiffness behaviors and dynamics of the rotor system versus the initial preload, rotating speed and external load are analyzed. The results demonstrate that the rigid rotor-bearing system presents the stiffness change trend of the first “soft-spring” and then “hard-spring” under large preload and low speed condition, while presents the obvious nonlinear “hard-spring” stiffness characteristic under small preload and high speed condition.