Structural modification of bladed disks for friction damper interface geometry optimization

Date

2025-8-29

Author

Fenerli, Kafkan

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Friction damping is frequently employed in turbine blades to mitigate vibration amplitudes and enhance fatigue life. The performance of dry friction dampers is highly dependent upon the contact geometry. Optimizing this contact geometry is essential to achieve optimal vibrational behavior and, consequently, a longer lifespan. During the optimization process, the modal properties of the blade and damper must be updated prior to conducting nonlinear vibration analyses. In this thesis, a method for structural modification applicable to cyclically symmetrical structures is developed. This method significantly reduces the modal analysis time for large degrees of freedom cyclically symmetrical systems, such as turbine blade assemblies. Its effectiveness is demonstrated through application to various turbine blades equipped with different types of dampers, including wedge and shroud dampers, with results compared to finite element analyses. Following structural modification, the modal data obtained for different contact geometries are utilized in nonlinear forced response analyses. The Harmonic Balance Method is employed to convert nonlinear differential equations into sets of nonlinear algebraic equations during the forced response analyses. Additionally, the Modal Superposition Method is used to reduce the size of the equation set. In nonlinear analyses, a 1D macro-slip friction model with a variable normal load is utilized. The contact geometry response levels are compared across different engine orders, facilitating the identification of the most optimal geometries.

Subject Keywords

Structural modification, Turbine blades, Dry friction, Friction damping, Nonlinear vibrations

URI

https://hdl.handle.net/11511/116016

Collections

Graduate School of Natural and Applied Sciences, Thesis