Numerical Analysis On Resonance Of Dry-friction Structures

There broadly exist the dry friction between the components with relative motions of the mechanical systems and flexible structures. The friction can induce complicated self-excited motions, which influence negatively the system operations. Whereas it can also reduce the structure vibrations through the energy dissipation.Blades are the hearts of turbomachinery. One of the common structural failures of blades is due to excessive stresses caused by large amplitude vibrations. To reduce the vibratory stress, the integral wire, platform and shroud are widely used to reduce the structure vibrations through the energy dissipation by the dry friction between the dampers. In this paper the analyzing method for resonant response of the dry friction structures is proposed. The vibration characteristics the dry friction damped blades are discussed.Part one, the dynamic models of dry friction, the study methods and state of the dry friction system dynamics are summarized.Part two, the time field tracking method is proposed for the resonant response of single-dof dry friction systems. A complete vibration cycle of the damper is divided into four successive intervals. The system possesses linear vibration characteristic during any of these intervals, which can be determined using analytical solution forms. So an analytical solution of the system periodic motion can be formed by combining the four intervals'solutions. The jump up and down phenomena in passage through the resonant point is revealed. The mechanism of vibration suppression of the friction damper is analyzed. The criterion of determing contact pressure to acquire the best contact condition is discussed.Part three, the friction model of rate-independent hysteresis with non-local memory is introduced to numerically investigate the resonant response of a single-dof blade system. The influences of the normal pressure, the friction coefficient, the amplitude of forcing and the external damping on the resonant amplitude and the corresponding frequency are investigated. The damper attached on blade can contact with the ground and other blade as well. The results for both cases are compared.The results in this paper show that the dry friction in blades plays a very important role in reducing vibration amplitude of the blades.