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.

Wireless sensing applications have extended into power transmission line monitoring applications. Minimal power consumption of sensor electronics have enabled kinetic energy harvesting systems to provides a means of self sustainability in the form of parasitic energy harvesting from power transmission lines. With this goal in mind, a miniature piezoelectric bimorph cantilever harvester has been developed using a magnetic tip mass which interacts with the oscillating magnetic flux surrounding power transmission wires. The focus of this thesis is develop an analytical model which can be used to optimize the amount of piezoelectric material to support sensory electronics. Special emphasis has also been placed on magnet orientation and geometry to ensure optimal magnetic flux interaction between input and output mechanisms. A single prototype harvester is designed with an arbitrary piezoelectric material length and experimentally validated at different conductor wire currents. The analytical model shows excellent agreement in frequency prediction for the prototype tested. Two damping techniques are used to experimentally extract modal damping ratios to predict peak mechanical and electrical responses at resonance frequencies. The miniature prototype design is less than 30 mm in length with only 10 mm piezoelectric material to produce a total volume of 154 10^-12 cm^3. The power output is measured at 174.1 W of power when positioned over top a 10 AWG copper conductor a distance of 6 mm with approximately 16 Amps of current passing though the conductor.

In-vessel tungsten components of a future demonstration fusion reactor are likely to be operated in the material's non-ductile regime. Assessment of the components' reliability is not possible with current ductile design codes or through experimental qualification. There is therefore an urgent need for non-ductile assessment procedures. One such approach currently considered is Weibull's weakest link theory, which is based on linear-elastic fracture mechanics and has its origins in ceramics. A full assessment of its validity has been performed, and the challenge of obtaining irradiated material data addressed. Bend tests at the macroscopic scale confirm previous findings that the scatter in strength of pure tungsten follows a two-parameter Weibull distribution, provided the material fractures within its elastic regime. However, tests conducted over a range of specimen sizes reveal the technique's shortcomings in accurately predicting the material's size effect in fracture, questioning its applicability to pure tungsten and also other brittle metallic materials. Fracture strength tests conducted at the micrometre scale through cantilever bending have addressed the challenge of obtaining irradiated material data. An ultra-fine grained self-passivating tungsten alloy, considered as an alternative contender to tungsten for in-vessel components, is shown to fracture within its linear-elastic regime at the microscopic scale. A reliable and repeatable measurement of its strength of approximately 5.9 GPa is obtained. The scatter in measurements is shown to be greater than random errors, and to be described well by a two-parameter Weibull distribution. Cantilever tests conducted over a range of specimen sizes reveal a strong size effect (4.3 - 9.0 GPa), which is accurately predicted by Weibull's weakest link theory. Ion implantations, conducted in the tungsten alloy to mimic neutron induced elastic collision damage, result in a statistically confirmed drop (6 %) in cantilever measured fracture strength at low doses (0.7 dpa), and an increase (9-16 %) at higher doses (7 dpa).The cantilever test technique is therefore suitable for the measurement of ion and neutron irradiation effects on the material's fracture strength. Provided a full validation of Weibull's weakest link theory strength extrapolation from the micro- to macroscopic scale is realised on a future heterogeneity free material batch, irradiated material data obtained from cantilever tests could be used to assess the reliability of in-vessel components fabricated from a self-passivating tungsten alloy, and fill the current gap in non-ductile design assessment procedures.

Orientador: Altair Antoninha Del Bel Cury / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Odontologia de Piracicaba / Made available in DSpace on 2018-07-25T05:48:51Z (GMT). No. of bitstreams: 1 Vaz_MarcosAndreKalabaide_D.pdf: 3759338 bytes, checksum: 7c236aca974ddaa171bffd6559a36b2f (MD5) Previous issue date: 1999 / Resumo: Este estudo verificou a distribuição de tensões na mandíbula pela simulação dos esforços mastigatórios em próteses fixas em "cantilever" implanto-suportadas. Foram confeccionadas 12 réplicas de mandíbulas, a partir da usinagem de um bloco de resina fotoelástica PLM-48 (Photolastic Inc., Raleigh, USA), nos quais foram instalados um par de implantes Restare (Lifecore, Chaska, USA) individualmente. Fixou-se implantes de 4 mm de diâmetro, variandose o comprimento dos mesmos, dividindo-os em 4 grupos: grupo I, um par de implantes de 11,5 mm de comprimento; grupo II, implantes de 13 mm de comprimento; grupo III, implantes de 15 mm e grupo IV, implantes de 18 mm. Estes implantes foram posicionados na região dos 2 pré-molares inferiores e sobre estes, foi confeccionada uma prótese fixa com pôntico distal em "cantilever" que permitiu a aplicação do carregamento em 5, 10, 15 e 20 mm nesta extensão. O carregamento foi aplicado com um dispositivo mecânico e calibrado por um dinamômetro (89 N). Cada conjunto foi levado individualmente ao polariscópio de transmissão (Série 080) para a visualização e interpretação das franjas fotoelásticas, obtendo-se desta maneira, valores numéricos que correspondem a ordem de franja para cada ponto marcado previamente nas réplicas. Concluiu-se que: 1) Os quatro grupos testados apresentaram padrões semelhantes quanto à distribuição de tensão quando submetidos à carga de 89 N. Porém, diferiram quanto à intensidade. 2) Quanto mais distante o ponto de aplicação do carregamento no "cantilever", maior a tensão transmitida à resina fotoelástica. 3) A concentração de tensão mais evidente deu-se na região inter-implantes, independentemente do comprimento do implante ou do "cantilever" / Abstract: This study verified tension distribution in the mandibular bone by masticatory efforts simulation on cantilever implant supported fixed prosthesis. Twelve mandibular bone replicas were obtained by milling a photoelastic material block (pLM-4B, Photoelastic Inc., Raleigh, USA). A pair of Restore implants (Lifecore, Chaska, USA) was insta1led on each resin replica. Four millimeter in diameter implants of various lengths were fixated and were divided into 4 groups. Group L a pair of 11,5 mm implants; Group 11, a pair of 13 mm implants; Group III, a pair of 15 mm implants and Group IV, a pair of 18 mm implants. These implants were positioned on the lower second pre-molars region. A fixed prosthesis was fabricated with cantilever distal pontic and was placed, over the implants, which allowed load application on 5, 10, 15 and 20 mm of the cantilever's extension. The load was applied with a mechanical device which was calibrated with a dynamometer at 89 N. Each set was individually taken to a transmission polariscope (Series 080) for visualization and interpretation of photoelastic fringes. Numerical values of finges order were obtained for each pre-determined point in the replicas. It could be concluded that: 1 )The four tested groups showed similar patterns of tension distribution when submitted to a 89 N load application. But they were different in relation to intensity. 2) The farther the point of load application on the cantilever, the greater the transmitted tension to the photoelastic resin. 3) There was a greater tension concentration at the inter-implant region, which did not depend on the implant or cantilever length / Doutorado / Protese Dental / Doutor em Clínica Odontológica

This thesis proposes a control system to widen the bandwidth of piezoelectric transducers (PZTs) for vibration energy harvesting while extracting maximum power. A straightforward complex conjugate match achieves maximum power transfer only at a single frequency while requiring an impractically large inductance. The proposed system intends to address these problems. It incorporates a bi-directional DC/DC converter with feed-forward control to achieve a complex conjugate match over a wide range of frequencies.  Analysis of the proposed system and simulation results are presented to verify validity of the proposed method. / Master of Science

No description available.

The goal of this research is to measure viscosity via the analysis of amplitude response of a piezo driven vibrating cantilevers partially immersed in a viscous medium. As a driving frequency is applied to a piezoceramic material, the external forces acting on the system will affect its maximum amplitude. This thesis applies this principle through experimental and analytical analyses of the proportional relationship between viscosity and the amplitude response of the first natural frequency mode of the sinusoidal vibration. Currently, the few cantilever-based viscometer designs that exist employ resonant frequency response as the parameter by which the viscosity is correlated. The proposed piezoelectric viscometer employs amplitude response in lieu of resonant frequency response. The goal of this aspect of the research was to provide data confirming amplitude response as a viable method for determining viscosity. A miniature piezoelectric plate was mounted to a small stainless-steel cantilever beam. The tip of the cantilever was immersed within various fluid test samples. The cantilever was then swept through a range of frequencies in which the first frequency mode resided. The operating principle being as the viscosity of the fluid increases the amplitude response of cantilever vibration will decrease relatively. What was found was in fact an inversely exponential relationship between dynamic viscosity and the cantilever beam's vibrational amplitude response. The experiment was performed using three types of cantilevers as to experimentally test the sensitivity of each.

No description available.