Graduation Semester and Year
Summer 2025
Language
English
Document Type
Dissertation
Degree Name
Doctor of Philosophy in Mechanical Engineering
Department
Mechanical and Aerospace Engineering
First Advisor
Daejong Kim
Abstract
Bump foils are the most widely used in foil bearings, but the behaviors of bump foils are complicated, and their characteristics have been a focus of research for decades. Bump foils are usually modeled as stiffness and damping are accounted for through interactions with shaft eccentricity, loading, shaft speed and excitation frequency. These nonlinear characteristics of the bump foil of radial foil bearings can be observed during both manufacturing and operational processes because of their inherent structural properties such as bump geometry, forming process, age-hardening process and complicated contact behavior with bearing housing. These nonlinear characteristics are one of the challenges in analyzing the characteristics of the foil bearings.
In this study, the analytical models will be developed to analyze actual bump foil operational behavior which considers the bump foil nonlinear characteristics. First, the nonlinear stiffness of bump foils in flat configuration has been experimentally measured and compared with various analytical models. Furthermore, the same bump geometry but with a curved configuration for actual radial foil bearings was used to measure the structural non-linear stiffness in the bearing level in a push-pull setup and compared with analytical prediction. Thus, the nonlinear bump stiffness model was adapted to the radial foil bearing to calculate overall bearing stiffness and damping coefficients, and stability characteristics through modal analysis and transient time domain orbit simulations. Lastly, the non-linear stiffness model of the bump foils will be verified by measuring bearing coefficients using shaker systems. Therefore, the novel bump foil bearing nonlinear stiffness model has been developed and verified which is applicable to both linear bearing coefficients and nonlinear rotordynamics analyses.
Keywords
Air foil bearing, Gas bearing, Rotordynamics, Hydrodynamic, Bearing coefficients, Structural stiffness, Turbomachinery
Disciplines
Acoustics, Dynamics, and Controls | Applied Mechanics | Computer-Aided Engineering and Design | Tribology
License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Recommended Citation
Lee, Woongeon, "Nonlinear Bump Stiffness Model and Its Effect on Structural Stiffness and Nonlinear Rotordynamic Characteristic of Foil Bearing" (2025). Mechanical and Aerospace Engineering Dissertations. 431.
https://mavmatrix.uta.edu/mechaerospace_dissertations/431
Included in
Acoustics, Dynamics, and Controls Commons, Applied Mechanics Commons, Computer-Aided Engineering and Design Commons, Tribology Commons