An Experimental Investigation in the Mitigation of Flutter Oscillation Using Shape Memory Alloys
The occurrence of aerodynamic flutter is a major concern for designers of systems involving fluid structure interactions. This phenomenon is undesired in most applications and can cause aircraft instability, fatigue, excess noise, and even catastrophic failure. The aim of this research is to quantif...
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| Format: | Dissertation |
| Language: | English |
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ProQuest Dissertations & Theses
01-01-2016
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| Online Access: | Get full text |
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| Summary: | The occurrence of aerodynamic flutter is a major concern for designers of systems involving fluid structure interactions. This phenomenon is undesired in most applications and can cause aircraft instability, fatigue, excess noise, and even catastrophic failure. The aim of this research is to quantify the effect of embedded shape memory alloys (SMA) as an active suppression system to mitigate flutter vibrations. A silicone plate with embedded SMA (Nitinol) wire was designed. Forced response vibratory testing was conducted using a dynamic shaker. Testing was also done using a subsonic wind tunnel to induce flutter. Preliminary computational studies were also performed to observe vibratory behavior of a fluttering plate upon stiffness variation. Results confirmed that an increase in system stiffness results in decreased flutter vibration amplitude and an increase in frequency. Natural frequencies for forced response testing were calculated with FRF plots through a temperature loop. Experiments resulted in an average natural frequency shift of 44.7% and an amplitude decrease of 34% at the tip of the plate. Control samples were created using the same dimensions and silicone material. One sample contained embedded aluminum while the other contained no embedded material. The addition of the unactuated SMA wire resulted in an average natural frequency shift of 160% and amplitude decrease of 44.6% while the actuated SMA wire resulted in a shift of 258% and amplitude decrease of 63.6%. FFT frequencies and tip displacements were recorded at varying temperatures in flutter testing. Experiments resulted in an average FFT frequency shift of 44.6% and an amplitude decrease of 33.6% at the plate tip. A first bending, second bending and torsional mode was observed in all test samples. Upon actuation of the SMA the amplitude of the fluttering flag was reduced by 97.5μm (34.4%) for first bending, 3.3μm (33.6%) for second bending, and 12.44μm (60.7%) for torsional modes. Experimental results indicate that SMA embedded wire has the ability to improve structural stiffness properties of a system and alter its vibrational behavior. This qualifies SMA as a feasible material in active vibration mitigation systems. SMA has the potential to mitigate flutter and other vibrational phenomena. |
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| ISBN: | 0438389581 9780438389588 |