Transient Rotor Dynamics Behaviour of Shrink-Fitted Overhung Rotor

The paper aims to predict the transient behaviour of a vertically overhung high-speed rotor bearing system known as a spin test apparatus. The spindle and arbor are shrink-fitted and, hence, at very high-speed conditions are liable to alter the fit condition at the interface. The paper proposes a method to determine the contact stiffness at spindle-arbor assembly—the contact pressure at the interface, obtained through Lame's theorem. The dynamic contact stiffness under the influence of centrifugal force is determined at different spin speeds and modelled as uniformly distributed translational and rotational springs at the interference of spindle and arbor node locations. The contact stiffness is assumed as a function of radial interference and rotational speed and its influence on the stability of the rotor bearing system is investigated. The external damper at the spindle location controls the vibrational amplitude during coast up and affects the system's critical speeds. The predicted transient response agrees well with the experimental response, verifying the proposed identification method of the contact stiffness.