Finite Element Modelling of the Dynamic Behaviour of Solid Elastic Rotor Under Gyroscopic Effect Stressing

Gyroscopy is key in dynamics of rotating system and interacts with non-rotating and rotating damping, thus influencing the overall dynamic stability. Centrifugal actions induce stiffening and softening effects, respectively, on deformable bodies while rotating, and couple rotor modes. In the literature, the effect of gyroscopy is predicted by analytical models, while the complex layout of industrial rotors is analyzed by solid finite elements. Those currently implemented within commercial software look unable to completely predict all gyroscopy effects. After a description of the state-of-the-arts, the finite elements currently exploited by commercial software are analyzed. A refined FEM formulation is then introduced, to include the deformations of elastic rotating elements, and evaluate their impact upon whirling motions. A preliminary validation is proposed, through the dynamic response of a test rig expressively set-up. Some differences are detected between in-plane and out-of-plane whirls, a good agreement is found between numerical and experimental evidences, and key dependencies are associated to rotor layout, size and operating conditions.