Measuring the Performance of Underplatform Dampers for Turbine Blades by Rotating Laser Doppler Vibrometer

Underplatform friction dampers are commonly used to control the vibration level of turbine blades in order to prevent high-cycle fatigue failures. Experimental validation of highly non-linear response predictions obtained from FEM bladed disk models incorporating underplatform dampers models, has proved to be very difficult so as the assessment of the performance of a chosen design. In this paper, the effect of wedgeshaped underplatform dampers on the dynamics of a simple bladed disk under rotating conditions is measured and the effect of the excitation level on the UPDs performances is investigated at different number of the engine order excitation nearby resonance frequencies of the 1st blade bending modes of the system. The measurements are performed with an improved configuration of a rotating test rig, designed with a noncontact magnetic excitation and a non-contact rotating SLDV measurement system.