Comparison of Two Widely-Used Frequency-Time Domain Contact Models for the Vibration Simulation of Shrouded Turbine Blades

Abstract

Friction damping is often used in turbomachinery to reduce the vibration amplitudes of turbine blades in operation. Different approaches can be used to simulate the friction contact in the design process. For nonlinear steady state simulations, the Multi-Harmonic Balance Method (MHBM) is often used in combination with an Alternating Frequency Time (AFT) Method. The friction contact can be modeled by introducing normal and tangential stiffnesses and a Coulomb friction law. However, it is difficult to identify these contact stiffnesses experimentally. Alternatively, a formulation with Dynamic Lagrangians can be chosen. This contact model can be formulated without the need for contact stiffnesses. Both widely-used approaches are applied to a model bladed disk with nonlinear shroud contact and compared with a special focus on the predicted vibrational behaviour, numerical convergence, and their sensitivity towards changes in the input parameters.