Linear and Nonlinear Dynamics of a Turbine Blade in Presence of an Underplatform Damper with Friction

In this thesis, a numerical simulation of the linear behavior of a turbine blade subjected to a rotation with large displacements has been carried out by the use of a specialized code. A finite element formulation of the problem has been considered in order to to develop a realist model and examine the vibration of the blade undergoing a rigid body rotation. In or-der to achieve this goal, the dynamics of the multibody rotor blade system has been studied by the use of the Floating Frame of Reference Formulation [1] applied to the case of a de-formable body, the blade, connected to a rigid body, which represents a rotor rotating at a constant angular velocity. The second part of the thesis focuses on the non-linear dynamics of a system consisting of two blades with a underplatform damper between them. Turbine blades frequently reach the resonance conditions due to the high speed of rotation in working environment with the consequence of an increased amplitude of vibration which can cause fatigue failure of the structure. The presence of an underplatform damper can help to dissipate a part of the en-ergy at resonance through frictional contact between the blades platform and the damper, increasing the fatigue life of the blades.