Experimental study of friction damping of blade with loosely assembled dovetail attachment

In order to study the friction damping characteristics of blade with loosely assembled dovetail attachment, an experimental method and a test rig are presented in this article. In the experiment, a axial load is imposed at the bottom of blade attachment to simulate the blade centrifugal force. A harmonic force is imposed on the blade as airflow force. The forced responses of a group of plane blades and a compressor blade are measured at different centrifugal forces. The results show that the resonant frequency increases with the centrifugal force, and gradually reaches the maximum. When the centrifugal force increases, the amplitude of resonant response decreases at the beginning and then increases. There is an optimal centrifugal force under which the resonant amplitude is minimal and the friction damping effect is the best. There is softening spring effect when the friction forces worked on blade system. From the results of compressor blade, it is found that when the centrifugal force is 1.5 kN, the resonant amplitude reaches the least value of 3.42 g, which is only 22.4% of the biggest value 39.88 g. This means that 1.5 kN is the optimal centrifugal force.