The Estimation of the Contact Stiffness for Directly and Indirectly Coupled Turbine Blading

Forced vibrations can lead to a substantial damage of the blading. To reduce the vibrational amplitudes to reasonable magnitudes, several coupling concepts, like shroud coupling or underplatform dampers, have been developed in the past. Mechanical models for the analysis of the forced response of coupled turbine blading are available. These models include an appropriate contact model to account for the contact effects like frictional damping, for example. These contact models demand for a stiffness type parameter, this is the so-called contact stiffness. Unfortunately, there is no straight-forward way for the determination of this parameter. In this paper, simple mechanical models are used for the estimation of the contact stiffness. The estimated contact stiffnesses are then used in forced response computations. The results of these computations are compared to measurements in order to find the most appropriate method for the contact stiffness estimation.