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Abstract In operation, blisks are subject to dynamic loading, which result in large response amplitudes near resonance. To reduce the response level and prevent damages caused by high cycle fatigue, friction damping sources are introduced to dissipate vibrational energy. The effectiveness of friction dampers depends not only on the mode shape of the vibrational mode being excited, but also on the damper material and geometrical properties. To create a robust design, it is necessary to parametrize the damper geometry, and to study the effect of geometric parameters on energy dissipation. The effectiveness of the damper is determined by evaluating the reduction in forced responses due to friction damping. To compute the nonlinear forced responses of a blisk–damper system, a reduced-order model is constructed with the method of coherent ring dampers (CoRiD). The equations of the reduced-order model are efficiently solved by the harmonic balance method (HBM). A parametric study on the effectiveness of a V-shaped friction ring damper is presented, focusing on the sensitivity of the damper effectiveness to variations of the dimensions of the damper geometry. Highlights • Specialized friction dampers for turbomachinery blisks are investigated. • The geometry of ring dampers is parametrized for enhancing damper effectiveness. • The damper geometry is optimized for effectiveness and robustness. • A novel design method for ring dampers is proposed, namely the frequency split. • A reduced-order modelling method (coherent ring damper, CoRID) is used. [ABSTRACT FROM AUTHOR]

In turbomachinery applications, rotating bladed disks (blisks) are often subject to high levels of dynamic loading, such as traveling wave excitations, which result in large response amplitudes at resonance. To prevent premature high cycle fatigue, various dry friction dampers are designed for blisk systems to reduce the forced responses. Ring dampers are located in the disk, underneath the blades, and are held in contact with the blisk by centrifugal loading. Energy is dissipated by nonlinear friction forces when relative motions between the ring damper and the blisk take place. To investigate the dynamic responses of blisk–damper systems in the presence of the nonlinear frictional contacts, conventional methods based on numerical time integration are not suitable since they are computationally expensive. This paper presents a reduced-order modeling technique to efficiently capture the nonlinear dynamic responses of the blisk–damper systems. Craig–Bampton component mode synthesis (CB-CMS) serves as the first model reduction step. A novel mode basis that mimics the contact behavior under sliding and sticking conditions is developed to further reduce the CB-CMS model while maintaining its accuracy. The resulting reduced nonlinear equations of motion are solved by a hybrid frequency/time domain (HFT) method. In the HFT method, the contact status and friction forces are determined in the time domain by a three-dimensional contact model at each contact point, whereas the reduced equations of motion are solved in the frequency domain according to a harmonic balance formulation. Moreover, to investigate the effects of blade mistuning, which can lead to drastic increase of forced responses, an extension of the reduced-order models (ROMs) is developed based on component mode mistuning. Forced responses computed by the proposed ROMs are validated for both tuned and mistuned systems. A statistical analysis is performed to study the effectiveness of ring dampers under random blade mistuning patterns. [ABSTRACT FROM AUTHOR]