- Title
- The string vibrator experiment-experimental and analytical determination of system fundamental natural frequencies
- Creator
- Gordon, Mark Leonard
- Subject
- Vibration
- Subject
- Nonlinear oscillations
- Subject
- Waves
- Date
- 2011-11
- Type
- Doctoral theses
- Type
- text
- Identifier
- http://hdl.handle.net/10353/24002
- Identifier
- vital:62245
- Description
- This thesis represents an experimental and intellectual journey of more than three years. The String Vibrator Experiment (SVE) is an experimental payload on the SumbandilaSat, satellite. The experiment was initially designed to compare low-earthorbitstretched string nonlinear dynamics with those found terrestrially, with particular emphasis on the effects of micro-gravity and near vacuum. Due to the damage of some internal components of the SVE, the terrestrial experiment had to be characterized by finding both transverse fundamental natural frequencies and the longitudinal system fundamental natural frequency. Forced and free vibration tests were performed on the SVE, with comparable results. The percentage frequency difference between measurement results obtained for the said natural frequencies was found to be acceptable. An analytical model for the string longitudinal system was developed using Energy Methods, assuming linear coupling of the stretched string and the flexible support. Bessel Functions were used to find the natural frequency of the flexible support, which is made of a thin-circular plate loaded centrally by the stretched string and fixed on its outer boundary. The natural frequency thus predicted, corresponds closely with that measured by Laser Doppler Vibrometry. It was found that the longitudinal system behaves in an uncoupled, manner. In this study use was made of piezo bi-morph sensors as vibration measuring devices, with promising results. A method called the peak amplitude discrimination method is introduced to find the respective resonant frequencies; this method is an adaptation of the sweptsine frequency method Nonlinear behavior of the SVE was found to exist exhibiting Sub-harmonics, Super-harmonics, Combination harmonics and Internal Resonances. It is hoped that the experimental methods used in this study would aid in the measurement and analysis of longitudinal vibrations found in flexible cables, rods and rigid bars.
- Description
- Thesis (PhD) -- Faculty of Science and Agriculture, 2011
- Format
- computer
- Format
- online resource
- Format
- application/pdf
- Format
- 1 online resource (138 leaves)
- Format
- Publisher
- University of Fort Hare
- Publisher
- Faculty of Science and Agriculture
- Language
- English
- Rights
- University of Fort Hare
- Rights
- All Rights Reserved
- Rights
- Open Access
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Collections
UFH Department of Physics
| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | SOURCE1 | PhD Physics (May 2012) GORDON.pdf | 10 MB | Adobe Acrobat PDF | View Details Download |