Dry-Friction Damping in Vibrating Systems, Theory and Application to the Bladed Disc Assembly

The chapter deals with a dry friction damping in the dynamics of model blade systems. The main emphasis is to the solution of damping effects of dry friction contacts in tie-bosses and shrouds. Friction is considered herein from phenomenological view. The variety of modified dry-friction models and results of their equivalent linearization are presented at the beginning. Then numerical models, i.e. discrete analytical, reduced and full finite element, used in our research of non-linear dynamic behavior of the blade cascades and bladed wheel with dry friction contacts are discussed. Dynamics states, such as resonant vibration, free attenuation, self-excitation, are considered. The detailed dynamic analysis of non-linear behavior of these systems due to dry-friction contacts is presented for discrete analytical model with the stick-slip friction contact. Furthermore, the solution of the blade bundle dynamics with the tie-boss coupling by the 3D FE model with surface to surface contacts is described. Because of the rotary periodicity, the bladed wheels bring special resonant vibration mode, i.e. travelling wave mode, in dependence on a type of wheel excitation, the dynamic responses of the wheel to nozzle excitation and self-excitation are studied, too. For validation purposes, we describe the experiments and their results on blade bundles with two types of dry friction coupling. The comparisons with the numerical results show that in spite of simplifications in the modelling of the dry-friction contacts, the used numerical models can deliver very useful information about additional stiffness, damping and stabilization effect.