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A flexible rotor supported by two journal bearings under nonlinear suspension and the lubricating oil is assumed to be temperature dependent in this study. Analytical tools were inclusive of bifurcation diagrams, dynamic trajectories, power spectra, Poincaré map, fractal dimension, and Lyapunov exponent are used to verify the dynamic characteristics of the rotor-bearing system, and abundant periodic, subharmonic, quasi-periodic, and even chaotic motions are found in this study. From the simulation results, the higher operating temperature will also cause the dynamic trajectory of the system to become non-periodic vibration. The rotor-bearing system operating in a non-periodic motion state may lead to possible broadband vibration with large amplitude and increase the possibility of fatigue or failure of the system. Such simulation analysis will help engineers avoid unnecessary trial and error when designing and applying rotor-bearing systems. [ABSTRACT FROM AUTHOR]

In this study, the nonlinear dynamic analysis of the hybrid squeeze film damper mounted on a gear-rotor-bearing system is presented. The strong nonlinear oil film force, nonlinear rub-impact force between the rotor and stator, and the gear meshing force are considered in this study. The bifurcation diagrams are plotted using a dimensionless imbalance factor, damping coefficient, and speed ratio as control parameters in this study. The beginning of chaotic motion is identified by phase diagrams, power spectrum, Poincaré maps, bifurcation diagrams, maximum Lyapunov exponent, and the fractal dimension of the system. The numerical results provide useful insights into the design and development of a gear-rotor-bearing system for rotating machinery that operates at high speeds and highly nonlinear conditions. Hybrid squeeze film damper is used to suppress irregular dynamic behaviors and reduce greater amplitude, even if the rotational speed of the rotating machine is higher, which is also confirmed in this study. [ABSTRACT FROM AUTHOR]