Study on the coupled bending-torsional vibration of unbalanced rotor system with external excitations

In order to research characteristics of unbalanced rotor system with external excitations, a dynamic model of rotor was established. This model not only considered the influences of the gyroscopic effect and the gravity, but also includes two kinds of unbalance which named static/dynamic unbalance. Use the hypothesis of small angle, expression of forces and torque which caused by translation and rotational of these two unbalances and gravity was derived in detail. Using the Lagrange method with six degree of freedom, motion equations of the system were derived. Combined Runge-Kutta approach, dynamic equations of the model were solved. Moreover, nonlinear vibration characteristics were analyzed by means of three kinds of diagrams. Thus, theoretical foundations are established for optimization design and fault diagnosis of rotor-bearing system.