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This work provides a study of the natural frequencies of a cantilevered beam with tip mass and axial load. Displacement feedback control is applied using piezo actuators attached to the top and bottom of the beam. The center of gravity of the mass and its rotary inertia are accounted for in the solution. The analysis of flexible components is essential to provide for the successful design of various engineering structures. This study provides an analytical solution to the dynamic behavior of a cantilevered beam carrying a mass at the free end, while being subjected to constant axial load. The structure is modeled using the Euler-Bernoulli theory and the contributions of the mass, thickness and stiffness of the piezoelectric actuators to the structure are taken into account. The effects of the piezo input voltage polarity is also taken into account. The natural frequencies of the beam can be altered by applying a voltage in the desired polarity and thereby causing an extension or contraction in the piezo actuator. This mechanical response alters the frequencies of the piezoelectric beam. The piezoelectric effect causes a compression or extension strain when a voltage is applied along the direction of polarization. The strain in the piezoelectric beam causes a moment at the free end, which directly affects the natural frequencies. By applying a voltage in the same or opposite direction of the poling of the piezo, the result is a compression or extension perpendicular to the poling. An applied voltage in the same direction can be considered positive and reduces the frequencies, whilst in the opposite direction negative and increases the natural frequencies. In this investigation the piezo layer thickness is varied, which in turn allows for a variable voltage input. For a thicker layer, the voltage can be increased and the actuation strain increased. The frequency content of the dynamically varying forces applied to a structure has the potential to excite the structure at one or more of its natural frequencies. Using piezo actuators, the natural frequencies and the natural frequency gaps can be maximized. Maximizing the natural frequencies is useful to avoid resonance when the external excitation frequency is less than the natural frequency. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2014.

Thesis (M.S.)--Ohio University, November, 2001. / Title from PDF t.p.

Tez (Yüksek Lisans) - Süleyman Demirel Üniversitesi, Fen Bilimleri Enstitüsü, Makine Eğitimi Anabilim Dalı, 2008. / Bibliyografya var.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 69-71). Also available on the Internet.

Thesis (M.S.)--Rochester Institute of Technology, 2008. / Typescript. Includes bibliographical references (leaves 73-75).

Dissertation (Ph.D.)--University of Akron, Dept. of Mechanical Engineering, 2005. / "August, 2005." Title from electronic dissertation title page (viewed 12/27/2005) Advisor, Pizhong Qiao; Co-Advisor, Gangbing Song; Committee members, Wieslaw K. Binienda, Kevin L. Kreider, Paul C. K. Lam, Dane Quinn; Department Chair, Celal Batur, Wieslaw K. Binienda; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome Includes bibliographical references.

Thesis (M.S.)--University of Missouri-Columbia, 2004. / Typescript. Includes bibliographical references (leaves 69-71). Also available on the Internet.

L'essor des cristaux phoniques (CP) , structures constituées d'un arrangement périodique de différents matériaux dans des domaines d'applications variés tient principalement aux propriétés exceptionnelles qui permettent le contrôle de la propagation des ondes. Des travaux récents se sont intéressés à l'accordabilité en fréquence des CP. Notamment en insérant des matériaux actifs, il a été montré qu'il était possible de moduler la position en fréquence ou la largeur de bandes interdites sans avoir à changer la géométrie du CP. Dans ce contexte, on étudie la propagation d'ondes de Lamb dans une plaque piézoélectrique homogène couverte par des électrodes disposées périodiquement sur les deux faces. Différentes conditions aux limites électriques (CLE) ont imposées sur ces électrodes afin d'agir sur la dispersion des ondes de Lamb. On montre expérimentalement et numériquement que l'application de ces CLE permet des couplages de modes de Lamb de mêmes symétries ou de symétries différentes. / One of the most important properties of phononic crystals (PCs) is their ability to prohibit the propagation of acoustic waves in specific frequency ranges called band gaps (BG). Bragg scaterring and mode hybridization are the two principal known mechanisms for BG nucleation. Recently, the interest for BG tunability has grown rapidly. This study concerns the development of a piezoelectric PC that is able to generate and control the propagation of guided Lamb waves, thus offering tunability of the band structure. A piezoelectric plate covered by ID periodic arrangement of thin electrodes is investigated. It is shown that the application of various electrical boundary conditions (EBCs) on the electrodes allows to change the effective properties of the piezoelectric plate. The dispersion of the waves is then electrically tuned and, depending on the applied EBCs, we demonstrate experimentally and numerically the possibility of opening Bragg or hydridization gaps in the subwavelength regime.

Piezoelectric composite materials, consisting of a ferroelectric ceramic in an electrically-inactive polymer matrix, have been shown to greatly outperform single phase materials for certain applications. A new assembly technique, which electrically controls the spatial distribution of the ceramic within the polymer, promises to enhance the sensitivity of 0-3 type piezoelectric composites. The materials so-produced have a quasi 1-3 structure and it is intended that they will exhibit some of the advantages of 1- 3 piezoelectric composites, whilst retaining the simplicity of 0-3 manufacturing. The electric field structuring technique exploits the electrokinetic phenomenon of dielectrophoresis, which is responsible for the electrorheological effect. When a suspension of ceramic particles in an insulating fluid is exposed to a moderate AC electric field, the particles polarize and as a result they exhibit a mutually attractive force. Under suitable conditions the particles assemble into 'pearl-chains', 'fibrils' or columns, oriented parallel to the applied field. If the fluid is a resin pre-polymer, this can then be cured and the newly formed structures frozen into place to form a composite material with anisotropic properties. The key process parameters are explored and the implications of employing this method to produce technologically useful materials are discussed. It is demonstrated, for the first time, that dielectrophoresis can be used to induce anisotropic dielectric and piezoelectric properties in 55%vol. fraction ceramic/polymer composites. A model composite system of pure lead titanate in an epoxy resin is considered in basic detail. A method of producing a lead zirconate titanate (PZT) powder with a narrow particle size distribution, by flux growth, has been shown to be effective. New concepts in multiphase composites are introduced, whereby chains are formed within the confines of a second immiscible fluid or where particles of two different materials are mixed in a suspension, each material having its own 'polarization signature'.