| Summary: | 碩士 === 國立臺灣科技大學 === 機械工程系 === 105 === The solid-liquid coupled vibration characteristics of piezoelectric material was investigated on pump structures when piezoelectric actuator used on hydroacoustic devices. Four piezoelectric cylindrical shells were applied the electrode design method to cause different motions pushing and pulling fluids in pumps. Experimental measurements and finite element numerical calculations were used to determine the resonant frequencies and mode shapes of electrode designs for piezoelectric cylindrical shells, which could be used to promote the flow of air and water. Two different chamber sizes of piezoelectric pumps were designed to verify the solid-liquid coupled vibrations of piezoelectric elements using on pumps with piezoelectric cylindrical shells located above the surface of the fluid under quasi-free boundary. Both of designs have four piezoelectric cylindrical shells bonded to PDMS polymer membrane tube, such that resonant vibrations produce changes in the volume of the chamber, which increases the flow of fluid. Three experimental techniques were used to determine the solid-liquid coupled vibration characteristics. Electric speckle pattern interferometry (ESPI) was used to measure the resonant frequencies and mode shapes associated with out-of-plane and in-plane vibrations of piezoelectric material interacting with fluids. Second, a laser Doppler vibrometer (LDV) was used to obtain the frequency spectrum of vibrating displacement using dynamic signal swept-sine analysis. The third experiment involved analyzing impedance in the piezoelectric elements in order to identify the resonant frequencies and anti-resonant frequencies of the piezoelectric material under the influence of a fluid. The vibration coupling characteristics of piezoelectric cylindrical shells coupled with different fluids were determined by experimental measurements and the results were verified with finite element numerical calculation. Whether resonant frequencies or mode shapes in this fluid-structure coupled system, the dynamic characteristics of the piezoelectric materials have good consistence between experimental and numerical results. Finally, the results of vibration characteristics, which were obtained from this study, were applied to two different piezoelectric pumps. The effects of resonant frequencies and vibration modes on the flow rate of piezoelectric pump were discussed in open flow channel system. It provides complete information on the solid-liquid vibration characteristics of different piezoelectric pump designs.
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