Experimental study on vibration characteristics of dry friction damping of turbine blade with integral shroud

Dry friction structures have been widely used in turbine blade to increase damping and reduce vibration stress. In order to study the vibration characteristics of turbine blade with dry friction damping structure, a test rig was built, the laser vibrometer and eddy current sensors were utilized to measure the vibration characteristics of a blade with dry friction damping structure, vibration response curves and modal damping ratio of the blade with different shroud loads and different exciting forces were obtained. The experimental results show that the resonance frequency of the blade increases as the shroud load increases with a certain exciting force. It is also seen by the experimental results there is an optimal shroud load which can lead to the minimum vibration amplitude and the maximum modal damping ratio of blade, then the best damping effect is attained. The system features the dry friction damping with nonlinear characteristics, so the resonance frequency of the blade decreases as the amplitude of the exciting force increases and the modal damping ratio increases as the amplitude of the exciting force increases under a certain exciting force.