In this study, the steady state response to the gravity and the unbalance force, and the major natural vibration of a general rotor bearing system with the open or open-close type crack, is analyzed along the iterative numerical calculation method (the transfer matrix method). The open-close type crack is idealized as a step function of the bending moment. The nonlinear equations are linearized by using the Fourier expansion technique, and its solutions are given approximately with the static deflection, the once/rev. vibration, and the twice/rev. vibration. The analyzed calculated method is confirmed by comparing the calculations with the experiments for a small test rotor. The rotor bearing system model in this method is as accurate as the usual numerical rotor dynamic analysis model, and also the required procedures for the calculation are almost the same.

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This paper presents an analytical method for the evaluation of the synchronous response of a general asymmetric rotor-bearing system. In the analysis, slightly asymmetric shaft stiffness in bending and shearing, which distribute along the rotor, and asymmetric transverse mass moment of inertia are considered. The dynamic properties of bearings and pedestals are assumed to be anisotropic and coupled in each direction. The equations of motion with periodic time dependent coefficients are solved by the Harmonic Balance Method and formulated to the transfer matrix. These solutions include the “Modified Holzer-Myklestad-Prohl Method by Lund & Orcutt” as a special case. The results of the analysis are confirmed by a simple model test and field measurements of large turbosets.