Thesis (M.S.)--Mechanical Engineering, Georgia Institute of Technology, 2004. / Berthelot, Committee Chair; Lynch, Committee Member; Jacobs, Committee Member. Includes bibliographical references (leaves 111-113).

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Physics and Astronomy." Includes bibliographical references (p. 86-91).

Thesis (MTech (Mech. Eng.))--Peninsula Technikon, 1999. / Word processed copy. Summary in English. Includes bibliographical references (leaves 72-75). Also available online.

Transducers utilizing single crystal piezoelectrics as the active elements have been shown to exhibit broader operating bands, higher response levels, and higher power efficiency than transducers using piezoceramics while also reducing the size and mass of the transducer (Moffett et al., J. Acoust. Soc. Am., 2007). The key to these high performance characteristics is the piezocrystal's inherent high electromechanical coupling coefficient. One potential application is to replace multiple narrowband piezoceramic transducers with a single broadband piezocrystal transducer which reduces the system's weight and size. This is very important for the new generation of smaller and power efficient unmanned underwater vehicles (UUVs). A third application is for use in very broadband communication networks. The work presented here focuses specifically on the design, modeling, and construction of Tonpilz transducers using piezoelectrics as the active material. The modeling includes lumped element and finite element analysis to approximate the performance of these transducers. These models serve as the main structure of an overall iterative design process. The objective of this research is to compare the performance characteristics of a piezocrystal and a piezoceramic Tonpilz transducer and to validate the models by comparing the model predictions with experimental results. / text

Galloping of structures such as transmission lines and bridges is a classical aeroelastic instability that has been considered as harmful and destructive. However, there exists potential to harness useful energy from this phenomenon. The study presented in this paper focuses on harvesting wind energy that is being transferred to a galloping beam. The beam has a rigid prismatic tip body. Triangular and D-section are the two kinds of cross section of the tip body that are studied, developed and tested. Piezoelectric sheets are bonded on the top and bottom surface of elastic portion of the beam. During galloping, vibrational motion is input to the system due to aerodynamic forces acting on the tip body. This motion is converted into electrical energy by the piezoelectric (PZT) sheets. A potential application for this device is to power wireless sensor networks on outdoor structures such as bridges and buildings. The relative importance of various parameters of the system such as wind speed, material properties of the beam, electrical load, beam natural frequency and aerodynamic geometry of the tip body is discussed. A model is developed to predict the dynamic response, voltage and power results. Experimental investigations are performed on a representative device in order to verify the accuracy of the model as well as to study the feasibility of the device. A maximum output power of 1.14 mW was measured at a wind velocity of 10.5 mph. / text

Actuating a cantilever piezoelectric element over a frequency spectrum, the movement will show resonances and hysteresis behavior not present in the input signal. Excursion modeling and open loop control of a cantilever piezoelectric bimorph actuator was studied in this thesis, with the aim to enhance the actuator's movement to more accurately render audible input. This actuator has lower energy consumption and presents new possibilities for speaker design in constrained situations compared to conventional micro speaker technology. Much work has previously been done to model piezoelectric cantilever actuators below the first and second resonance frequency. This thesis describes a physical linear model and its modifications to render the eight first resonance frequencies below 20 kHz, as well as the model's performance in open loop control. This was performed on a single piezoelectric beam and a concept piezoelectric speaker. For the single piezoelectric beam the model was validated with fair overall result below 3 kHz. The model is suggested to have fair overall behavior up to 15 kHz. Above 15 kHz the experiments showed changed characteristics that were not modeled well. The open loop control had the intended behavior but severe resonances and physical constraints made the open loop control ineffective to enhance the sound rendering. Two different approaches were used for trying to improve the sound rendering based on an excursion model. These approaches did not generate useful methods but present viable input to future work with this type of speaker structure, for reducing disharmonics and creating a physical design tool for sound simulation. For the concept piezoelectric speaker, due to difficulties in measuring excursion, the model could not be validated. This made the approaches for enhancing the sound rendering ineffective. However, it can be concluded from the concept speaker that the cantilever piezoelectric speaker technology has qualities that could compete with the conventional micro speaker technology. Challenges remain in electric hardware, actuator configuration and acoustic design as well as in fine tuned signal processing for the concept speaker to become a competitive product.

No description available.

No description available.

No description available.

No description available.