Forrai dealt with the stability analysis of self-excited bending vibrations of linear symmetrical rotor-bearing systems with internal damping. investigated the modal characteristics of complex rotor-bearing systems using finite element method and came to the conclusion that the results including the rotational effects were more accurate. investigated two different approaches (Floquet theory and coordinate transformation) to develop the complex modal analysis for periodically time-varying linear rotor systems and found that the results of coordinate transformation are much efficient. analyzed the effect of fluid film bearing on whirl speeds of rotor-bearing system and found that a half whirl exists in the rotation caused by hydrodynamic bearings. developed a Timoshenko beam finite element model and studied the combined effects of shear deformations and internal damping on forward and backward whirl speeds. , dynamic analysis of rotor system was investigated based on finite element method, and the critical speeds were calculated, which included the effect of various parameters such as rotary inertia, gyroscopic moment, and internal damping.

In the studies by Nelson and Zorzi et al. There are many studies on dynamic analysis of rotor system for the solution of critical speeds and natural frequencies.

Rotor is the key component of rotating machinery, which is widely used in mechanical devices including gas turbines, aeroengines, industrial compressors, and motors etc., and the accurate prediction of natural frequencies of rotor is important for the safe operation of rotating machineries. The results show that the calculation values using enhanced stiffness of assembly part are in good agreement with those of ANSYS Workbench and experiment, and the percent errors of the first natural frequency and the second natural frequency are down to about 0.32% and 0.83%, respectively. At last the modal experiment is done to verify the accuracy of calculation and simulation. Then the modal analysis is performed to get the natural frequencies in ANSYS Workbench, in which the friction coefficient and interference fit are set to be the same as those of the finite element calculation method.

Secondly, the effect of the width of thick disk on diametrical moment of inertia, as well as the enhanced coefficient of bending stiffness of interference-fit part between disk and shaft, is included in the motion equations of thick-disk rotor, which are established based on finite element method, and the natural frequencies of rotor are obtained by solving the motion equations. Firstly, the friction moment on the contact surface of disk and shaft is deduced in terms of elastic theory, and a new enhanced coefficient of bending stiffness of assembly body is proposed and calculated for the first time. This paper is concerned with the modal analysis of a thick-disk rotor, which consists of an elastic shaft with a rigid thick disk assembled by interference fit, and the width of the thick disk is not negligible.

Ansys modal analysis