Lubrication-induced vibrations in rotating shaft systems: A dynamic model of elastohydrodynamic ball bearings

Investigating the dynamics of ball bearings is critical for mechanical system, as relative motion is transmitted through shafts supported by bearings. Despite their pivotal role and direct influence on vibrational characteristics, mostly simplified kinematic employed and tribological complexities ignored arising from lubrication. This study introduces a dynamic bearing model incorporating elastohydrodynamic lubrication (EHL) to enhance vibration analysis in rotating machinery. A five-degree-of-freedom rigid shaft-bearing system is formulated, accounting for bidirectional interactions between shaft dynamics and bearing vibrations. Nonlinear equations of motion are solved numerically for diverse lubricants. Results align closely with empirical benchmarks, notably for oil film thickness and contact behavior. Lubricant viscosity exhibits a proportional relationship with bearing stiffness, while damping coefficients inversely depend on angular velocity and directly on viscosity under EHL. System vibrations demonstrate heightened complexity compared to unlubricated configurations, with natural frequency dynamically shifting with shaft speed—a behavior linked to lubrication-structure coupling. These findings validate the model’s capability to characterize lubrication-dependent vibration mechanisms, providing a framework for optimizing high-precision rotating machinery.