Hysteretic Damping and Stress Evaluation of Rotor-Bearing Systems in the Resonance Zone

Rotor dynamics considerations play an important role in the design of a number of machine elements, especially those that operate at high rotational speeds. During system start-up and shutdown, the rotor and bearing materials are subjected to high mean and alternating stresses that cause fatigue, particularly when the rotor is running at critical speeds. In this paper, a new method is proposed in order to calculate the eigenvalues and mean and alternated stresses in the resonance zones of damped rotating systems by using FEM. The damped system is defined by the hydrodynamic bearings and hysteretic damping of the rotor material. The method is based on the calculation of eigenvalues in the resonance zone by varying the exciting frequency to minimize the complex frequency determinant. The alternated bending stresses are calculated after computing the eigenvalues of the systems, and a relevant analytically-derived mathematical model is presented.