Dynamic Analysis of Rotating Bladed Disk with Underplatform Damper

Abstract

This work presents dynamic analysis of a bladed disk system with underplatform dampers subjected to harmonic excitations. Blade vibration amplitudes are known to be seriously amplified and varied from blade to blade due to the difference in the blade geometry or due to differences in material properties. The phenomenon of having non-identical blades due to such variations is called mistuning. Since mistuning can lead to forced response amplitudes which are much larger than those predicted for a tuned assembly, additional dissipation elements (e.g., friction dampers) are sometimes integrated into the bladed disk assembly. Underplatform dampers are friction damping devices in order to decrease the amplitude of vibrations of blades in rotors. The work focuses on the studies of effects of damper wedge angle, engine order and speed to on the vibration responses at the blades. A lumped parameter model of bladed disk with underplatform damper is considered and assembled stiffness and mass matrices are used to solve the eigenvalue and transient analysis. Both the harmonic excitation and non-linear contact forces at the underplatform damper are considered as external forces. The differential equations are solved by the time integration scheme. Steady state response with under when a correct set of wedge angle of cottage roof damper and coefficient of friction between the contact surfaces is optimally selected. Contribution of present work are (1) considerations of mistuning effects in the stiffness matrix and (2) finite element analysis of a sector of a bladed disk (tuned) using cyclic symmetry boundary conditions. A scaled model of bladed disk rotor is fabricated for dynamic analysis.