Analytical and Experimental Investigation of Nonlinear Dynamic Characteristics of Hydrodynamic Bearings for Oil Film Instability Detection

Nonlinear vibration phenomena, such as oil whirl and oil whip, are common indicators of oil film instability in hydrodynamic bearings and are key signs of potential faults in rotating machinery. Excessive vibrations caused by oil film instability can accelerate bearing wear and lead to the failure of the rotating system. This paper presents a model for nonlinear dynamic coefficients, aimed at providing a quantitative approach for monitoring and predicting oil film instability. The impact of operational parameters and perturbation values on both linear and nonlinear stiffness and damping coefficients is investigated. Simulation results and experimental rotor vibration signals demonstrate that the nonlinear dynamic coefficient model effectively characterizes oil film instability and accurately predicts rotor trajectory, while traditional linear models are only applicable under low-speed and small-disturbance conditions. Compared to traditional analytical models and numerical solutions, the nonlinear dynamic coefficients have higher accuracy and efficiency and can reliably identify the onset frequency of oil film instability. This study clarifies the relationship between nonlinear dynamic coefficients and rotor dynamic response, laying a theoretical foundation for the monitoring and prediction of oil film instability.