Nonlinear dynamics of a non-stationary rotor-disk-bearing system with rub-impact and geometric nonlinearity under non-ideal excitation

This study investigates the nonlinear dynamic behavior of a non-stationary rotor-disk-bearing system subjected to rub-impact phenomena under varying operational conditions. The rotor is modeled as an Euler-Bernoulli beam, with rigid-body disks and bearings represented using both linear and nonlinear spring elements to accurately capture dynamic characteristics. The model incorporates inherent system nonlinearities, including large deflections, non-ideal external excitations, and rub-impact forces consisting of normal contact and frictional components. Rub-impact is triggered when the rotor's vibrational amplitude exceeds the radial clearance, activating contact interactions with the stator. The governing equations of motion are derived and solved using both numerical simulations and the analytical averaging method, demonstrating strong agreement. Results show that rub-impact significantly alters the system's vibrational response, particularly near critical speeds, leading to amplitude amplification, prolonged resonance, energy localization, and the emergence of the Sommerfeld effect. Parametric studies further evaluate the effects of damping, nonlinear bearing stiffness, and variations in applied torque on system behavior.