Vibration fatigue analysis and testing of notched beams

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2019

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Demirel, Gürzap İsmail

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Mechanical fatigue is an important phenomenon when the structures are exposed to dynamic, fluctuating loadings. Especially aerospace structures are commonly exposed to random vibration loadings. Even if the components are stable and durable for static requirements, vibration fatigue failures can occur due to the dynamic and fluctuating loadings. Moreover, if the loading frequency has a wide bandwidth as in random vibration loadings, the natural frequencies or resonance regions of the structures are disturbed with high probability. Therefore, in this thesis, vibration fatigue is studied both numerically and experimentally. The main focus of this thesis study is the research of the vibration fatigue. Hence, besides the analyses, the tests are conducted. In order to study the analyses and tests, aluminum and steel rectangular cross-section beams are designed and manufactured. In order to obtain a more distinct fatigue life than other parts of the beams, the notched areas added to beam geometry. Firstly, in order to ensure the reliability of the finite element model, mesh refinement works are conducted. Then, to decide the frequency interval of the analyses, modal analyses are carried out. Moreover, in order to obtain the appropriate damping ratios of the notched beams, which are an input of frequency response analysis, modal tests are carried out. Then, frequency response analysis of the beams are conducted. After that, vibration fatigue analyses are conducted. Furthermore, the effect of different damping ratio values is investigated in the analyses. Finally, the vibration fatigue tests of notched beams are conducted.

Subject Keywords

Girders., Keywords: Vibration Fatigue, Damping Ratio, Finite Element Method.

URI

http://etd.lib.metu.edu.tr/upload/12623260/index.pdf
https://hdl.handle.net/11511/43423

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

G. İ. Demirel, “Vibration fatigue analysis and testing of notched beams,” Thesis (M.S.) -- Graduate School of Natural and Applied Sciences. Aerospace Engineering., Middle East Technical University, 2019.