Rainbow gyroscopic disk metastructures for broadband vibration attenuation in rotors

In the last decade, the study of metastructures has gained increasing attention and its engineering applications for vibration control have been gaining maturity for industrial applications. Remarkably, there is a gap on the application of the former approach for rotating machines yet to be bridged. In this work, we present an investigation on the use of locally resonant metastructures for vibration attenuation on rotating machines. A simple rotor structure with periodically attached, compliantly mounted disk resonators is modelled and its dynamical behaviour is investigated. Both forced harmonic response and modal analyses are explored and a thorough evaluation on the interactions between the resonators and main structure is presented for varying conditions of rotating speed and forward and backward excitations. Periodic and rainbow type of resonators with a gradient spatial profile are considered for translational and rotational resonators. It is shown that the former does not present any gyroscopic effect while the attenuation performance of latter depends on the interaction of the forward and backward resonating modes with the excitation. In addition, the rainbow disk metastructure presented attenuation bands up to 60% larger than the periodic case with the same added mass. The results suggest that the proposed gyroscopic periodic structures can be effectively applied for new alternatives for vibration attenuation in rotors paving the way for further innovative engineering solutions on vibration control in lightweight and high speed hermetic rotating machinery.