E-Thesis 94 views 56 downloads
Nonlinear Interactions in Rotordynamics: Numerical and Experimental Investigations of Internal Resonances / MEHMET AKAY
Swansea University Author: MEHMET AKAY
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PDF | E-Thesis – open access
Copyright: the author, Mehmet Selim Akay, 2025. Distributed under the terms of a Creative Commons Attribution-NoDerivatives 4.0 License (CC BY-NC 4.0)
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DOI (Published version): 10.23889/SUThesis.71787
Abstract
In rotating machinery, tighter tolerances are crucial for efficiency, making rotor-stator interaction a key research area. This thesis explores the diverse nonlinear responses of rotordynamic systems, focusing on quasiperiodic internal resonances (IRs) in rotor-stator interactions through numerical an...
| Published: |
Swansea
2025
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| Institution: | Swansea University |
| Degree level: | Doctoral |
| Degree name: | Ph.D |
| Supervisor: | Shaw, A., and Friswell, M. |
| URI: | https://cronfa.swan.ac.uk/Record/cronfa71787 |
| Abstract: |
In rotating machinery, tighter tolerances are crucial for efficiency, making rotor-stator interaction a key research area. This thesis explores the diverse nonlinear responses of rotordynamic systems, focusing on quasiperiodic internal resonances (IRs) in rotor-stator interactions through numerical and experimental analysis. Numerical continuation and time simulations were utilized on a nondimensional 2-degree-of-freedom (2-dof) gyroscopic model where a cubic stiffness was employed, as well as a hyperbolic tangent (tanh) con-tact model that approximates discontinuous contact. A novel quasiperiodic continuation method was introduced, demonstrating that periodic continuation methods can be ex-tended to include nonautonomous quasiperiodic responses which included an adaptation of the Floquet theory. Nonlinear normal modes (NNMs) was also applied to study forward (FW) and backward (BW) mode coupling.Key findings from theoretical studies indicate that IRs of frequency ratio 2:1 and 3:1 can arise even with soft nonlinearities, with damping playing a crucial role in their persistence and amplitude. Homotopy method used to switch the bifurcation diagram between different nonlinearities facilitated bifurcation analysis without prior knowledge. Experimental validation was conducted using a test rig designed to reflect the theoretical model.Experimental results confirmed the influence of damping, while additional bifurcations were attributed to real-world boundary conditions. The transition from FW and BW precession of IRs was observed in both simulations and experiments, which was termed stagnation at the point where this occurs. However, the IRs of coupling between the swinging and rotational modes were not achieved experimentally due to small basins of attraction. The use of continuation in various forms proved valuable for the analysis of the nonlinear rotating machinery.This work advances the understanding of nonlinear rotor-stator dynamics by providing new methods for analysing and classifying IRs, while generating several future work ideas.The findings have implications for designing more robust rotating machinery, considering both numerical predictions and experimental constraints. |
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| Keywords: |
rotordynamics, bifurcation, continuation, internal resonance, homotopy, nonlinearnormal modes |
| College: |
Faculty of Science and Engineering |
| Funders: |
National Ministry of Education of Türkiye |