Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains xvii, 213 p.; also includes graphics (some col.). Includes bibliographical references (p. 206-213). Available online via OhioLINK's ETD Center

Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2005. / Includes bibliographical references. Also available in electronic version.

Made available in DSpace on 2014-06-11T19:27:14Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-09-26Bitstream added on 2014-06-13T20:35:23Z : No. of bitstreams: 1 prazzo_ce_me_ilha.pdf: 1585012 bytes, checksum: 3ddb6b2bb4fddee99d49636888c24ded (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Esse trabalho discute o uso dos materiais piezelétricos, mais especificamente, o Polyvinylidene Fluoride (PVDF) e o Lead Zirconate Titatane (PZT) na análise modal experimental (AME) de estruturas mecânicas. Materiais piezelétricos, também chamados de materiais inteligentes, têm se consolidado como uma nova tecnologia que mostra um grande potencial de aplicação em diferentes áreas da engenharia. Esse tipo de material exibe um acoplamento entre multi-domínios físicos, como por exemplo o acoplamento eletro-mecânico, o térmo-magnético, etc. O acoplamento eletro-mecânico produz um deslocamento elétrico quando o material é sujeito a uma tensão mecânica (efeito direto) e um deformação mecânica quando esse material é submetido a um campo elétrico (efeito inverso). Assim, principalmente por conta desses efeitos, seu uso no campo da análise modal experimental torna-se uma interessante questão a ser investigada. A incorporação de novas tecnologias nos testes estruturais pode agregar novos conhecimentos e avanços tanto na análise modal baseada na relação entrada-saída da estrutura, quanto na mais recente técnica, a análise modal baseada apenas na resposta das mesmas. Os conceitos teóricos para o desenvolvimento são apresentados e discutidos neste trabalho, onde é mostrada a análise modal de uma viga utilizando tanto sensores e atuadores convencionais quanto os produzidos com materiais inteligentes. Os testes de análise modal da viga foram feitos utilizando diferentes combinações de sensores e atuadores e isso pode mostrar as diferenças da estimativa de modos utilizando materiais piezelétricos. Também é apresentada a formulação da relação entre os modos em deslocamento e os modos com diferença de inclinação obtidos com materiais piezelétricos e, finalmente, uma comparação dos resultados obtidos pelas diferentes técnicas. Os testes apresentados mostram... / This work discusses the use of piezoelectric materials, more specifically, Polyvinylidene Fluoride (PVDF) and Lead Zirconate Titanate (PZT) for experimental modal analysis (EMA) of mechanical structures. Piezoelectric materials also called smart materials have becoming a consolidated new technology that shows a large potential of application for different engineering areas. These materials exhibit a multi physics domain field coupling like mechanical and electrical coupling domains, thermal and magnetic coupling and etc. The electro-mechanical coupling domains of the material produces an electric displacement when the material is subject to a mechanical stress (direct-effect) and a mechanical strain when the material is submitted to an electric field (inverse effect). So, mainly due to these effects, the use in the experimental modal analysis field appears to be an interesting issue to be investigated. The incorporation of this new technology in the structural tests might aggregate new acknowledgments and advances in the well consolidated input-output based modal analysis techniques as well as in the more recent output only-based modal analysis. This work aims to present some contribution in this area by using piezoelectric sensors, instead of the conventional ones like accelerometers for modal analysis of mechanical structures. The theoretical concepts and background for the developing of the work are presented and discussed, it is also presented the modal analysis of a beam like structure using conventional sensors/actuators and piezoelectric materials. The modal analysis tests of the beam are conducted using different kinds of sensors/actuator and they give some insight of the difference of the estimated modes shapes by using piezoelectric materials. It is also presented a formulation that shows the relation between... (Complete abstract click electronic access below)

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Ionic electroactive polymer (IEAP) actuators are a class of electroactive polymer devices that exhibit electromechanical coupling through ion transport in the device. They consist of an ionomeric membrane coated with conductive network composites (CNCs) and conductive electrodes on both sides. A series of experiments on IEAP actuators with various types of CNCs has demonstrated the existence of a direct correlation between the performance of actuators and physical and structural properties of the CNCs. Nanostructure of CNC is especially important in hosting electrolyte and boosting ion mobility. This dissertation presents a series of systematic experiments and studies on IEAP actuators with two primary focuses: 1) CNC nanostructure, and 2) ionic interactions. A novel approach for fabrication of CNC thin-films enabled us to control physical and structural properties of the CNC thin-films. We, for the first time, facilitated use of layer-by-layer ionic self-assembly technique in fabrication of porous and conductive CNCs based on polymer and metal nanoparticles. Results were porous-conductive CNCs. We have studied the performance dependence of IEAP actuators on nano-composition and structure of CNCs by systematically varying the thickness, nanoparticle size and nanoparticle concentration of CNCs. We have also studied influence of the waveform frequency, free-ions and counterions of the ionomeric membrane on the performance and behavior of IEAP actuators. Using the LbL technique, we systematically changed the thickness of CNC layers consisting of gold nanoparticles (AuNPs) and poly(allylamine hydrochloride). It was observed that actuators consisting of thicker CNCs exhibit larger actuation curvature, which is evidently due to uptake of larger volume of electrolyte. Actuation response-time exhibited a direct correlation to the sheet-resistance of CNC, which was controlled by varying the AuNP concentration. It was observed that size and type of free-ions and counterion of ionomeric membrane are also influential on the actuation behavior or IEAP actuators and that the counterion of ionomeric membrane participates in the actuation process. / Ph. D.

An elasticity solution is presented for the static equilibrium equations of an axisymmetric composite cylinder under loadings due to embedded piezoelectric laminae. The solution is used to study both uniform and non-uniform distributions of the piezoelectric effect and results are verified using the finite element method. A cylindrical truss element actuator is developed based upon this analysis and shown to be useful in damping vibrations of truss-type structures. It has also been shown that by varying the distribution of the piezoelectric effect. spatially, modal actuators capable of actuating specific modes of axial vibrations in a bar can be developed. Finally, the effects of a piezoelectric patch have been investigated. The axial forces generated at the fixed ends of a cylinder are demonstrated to be proportional to the length of the patch. / Master of Science

A mathematically one-dimensional model was developed to predict the static response of composite sandwich beams subjected to loads induced by piezoelectric (PZT) actuators. The model was derived using Reddy's (1984) displacement field for a laminated plate which consists of cubic variation of the in-plane displacement through the thickness. In this model, beam deformations include extension, bending, transverse shear, St. Venant torsion, and torsion due to warping of the cross section out of its plane. The PZT actuators can be configurated to induce a bimoment, resulting in twist cf the beam through the warping of the cross section. Hence directionally attached PZT (DAP) actuator elements, which cause twist by inducing tensile and compressive strains at 45° to the longitudinal axis of the beams, are not necessary to actuate twist. For an aluminum beam example, it is shown that the PZT bimomet control produced about 2.7 times more twist than the conventional DAP control. / Master of Science

The strain induced into isotropic flat plates by surface bonded and embedded piezoceramic patches was investigated. The free piezoceramic patch voltage/strain response was characterized using moire interferometry and Twyman-Green interferometry techniques. Moire interferometry experiments were conducted to investigate the induced strain of actuation in a flat plate with two surface bonded piezoceramic patches and a flat plate with one embedded patch. Three-dimensional finite element models of these two specimens were constructed and analyzed. The measured in-plane voltage/strain response of a free piezoceramic patch was found to be nearly linear and of a much higher magnitude than the published data. Similarly, the out-of-plane voltage/strain response was found to be much higher in magnitude than the published data as well as being non-linear. Correlation between the moire experiment concerning the surface bonded patch specimen and the corresponding finite element model was good, indicating the validity of the modeling technique. Possible depoling damage of the embedded patch caused the correlation between the experiment and analysis of this specimen to be poor. Both finite element models predicted stresses that are not statically significant but may represent problems over many loading cycles. / Master of Science

The braided composite actuator is a pressure-driven muscle-like actuator capable of large displacements as well as large blocking forces. It consists of an elastomeric tube reinforced by a sleeve braided by high performance fibers. In addition to the actuation properties, this actuator can also exhibit a large change in stiffness through simple valve control when the working fluid has a high bulk modulus. Several analytical models have been previously developed that capture the geometrical and material nonlinearities, the compliance of the inner liner, and entrapped air in the fluid. The inter fiber yarn compaction in the fiber layer, which is shown to reduce the effective closed-valve stiffness, is studied. A new analytical model for uniformly deformed actuators is developed to capture the compaction effect. This model considers the inter fiber yarn compaction effect and the fiber extensibility as well as the material and geometric nonlinearities. Analysis and experimental results demonstrate that the new compaction model can improve the prediction of the response behavior of the actuator. The compaction model is improved by considering the yarn bending stiffness. The governing equations are derived and the solution algorithm is presented. / Ph. D.