Dynamic Response Sensitivity to a Hydrodynamic Bearing Wear Model

Tiago Henrique Machado¹; Ricardo Ugliara Mendes¹; Katia Lucchesi Cavalca¹

¹ Faculty of Mechanical Engineering, UNICAMP

doi:10.20906/CPS/COB-2015-1594

Resumo

This work aims to analyze the influence of a wear model in cylindrical hydrodynamic bearings on the Frequency Response Function (FRF) of a rotor-bearing system. As noted in the past, the geometric discontinuities present in worn bearings causes an asymmetry in the dynamic properties and its influence can be noticed in the directional FRF of the rotating system, with the backward component changing in the presence of wear. Previous works evaluated the unbalance response in different rotational speeds; therefore, this study analyzes the FRF in order to represent a more realistic case, when it is not possible to operate the rotor near the critical speeds. In this case, the FRF simulate an experimental condition where a magnetic actuator could be used to excite the rotor and the measurement is made in the bearing position. In this paper the analysis will be done through the evaluation of the vibration amplitude in the natural and whirl frequencies. The dynamic coefficients of the bearings are obtained with a spring-damper concept, in order to represent the inherent flexibility and damping of the oil film. In this case, the coefficients are evaluated by the classical perturbation theory applied to the displacements and velocities of the shaft center inside the bearings.

Palavras-chave: Wear Model; Hydrodynamic Bearing; Linearized Dynamic Coefficients; Frequency Response Function (FRF)