Dissertation (Ph. D.)--University of Akron, Dept. of Civil Engineering, 2009. / "August, 2009." Title from electronic dissertation title page (viewed 9/16/2009) Advisor, Craig C. Menzemer; Committee members, Wieslaw Binienda, Robert Liang, D. Dane Quinn, Kevin L. Kreider; Department Chair, Wieslaw Binienda; Dean of the College, George K. Haritos; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.

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

Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2007. / William Singhose, Committee Chair ; Steven Danyluk, Committee Member ; Donna Llewellyn, Committee Member ; Nader Sadegh, Committee Member ; Neil Singer, Committee Member.

Thesis (M.S.)--Miami University, Dept. of Physics, 2007. / Title from first page of PDF document. Includes bibliographical references (p. 52-53).

Thesis (Ph.D. in Mechanical Engineering) -- University of Dayton. / Title from PDF t.p. (viewed 10/06/09). Advisor: Reza Kashani. Includes bibliographical references (p. 98-102).

Thesis (M.S.)--Rochester Institute of Technology, 1993. / Typescript. Includes bibliographical references (leaves 100-102).

This thesis presents the results obtained from a preliminary investigation into the potential application of the friction damping concept to wood structures to improve their seismic response. Sliding friction devices which contain heavy duty brake lining pads have been proposed in order to enhance a wood structure's seismic performance. The devices are mounted onto a structure's shearwalls to dissipate seismic energy input during the wall's deformation in an earthquake. Prototypes of the four friction damping devices were tested to examine their hysteretic behaviour. Conventional full scale, 2.44 x 2.44 m (8 x 8 ft) timber shearwalls, typical of ones used in residential and light-commercial building applications, and ones retrofitted with the friction damping devices were tested on a shake table. Three set of tests were conducted. They involved loading the walls under unidirectional racking, static-cyclic and simulated earthquake loads. Test results from the two types of shearwalls were compared against each other and against the findings from the computer programs SADT and FRICWALL. SADT is a finite elements program which computes the load-deformation behaviour of shearwalls. FRICWALL is an inelastic time-history dynamic model which computes the response time-history of a shearwall under a simulated seismic event. The cyclic tests of the friction damping devices showed that they exhibited very stable and non-deteriorating hysteretic behaviour. The shake table tests of the full scale timber shearwalls showed that the friction damped walls were stiffer, can sustain an average of 23.7 % higher racking load and dissipate an average of 42.9 % more energy than the conventional ones before a ductile failure. Failure in the conventional walls was brittle. These results were in agreement with the SADT findings. Under slow cyclic loads, they dissipated more energy, but because their overall hysteretic behaviour was still pinched, they were just as inefficient as the conventional walls at dissipating energy. On the average, their seismic performance was only marginally better than that of the conventional wall, with an average drop of 9.6 % in peak wall deflection. This is far short of the average of 29.5 % computed by FRICWALL. Detailed analysis of the results show that due to bending in the framing members of the shearwall, the load necessary to cause slippage of the friction devices was not achieved until wall deflections in the order of 25.4 mm (1.0 in) was reached. Since only at the peak or near-peak excitation levels of an earthquake did shearwall deflections surpass this magnitude, the devices were not able to contribute to the energy dissipation of the shearwalls during the majority portion of a seismic event. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Orientador: Marcos Silveira / Banca: Paulo José Paupitz Gonçalves / Banca: Fabrício Cesar Lobato de Almeida / Resumo: Neste trabalho, o comportamento dinâmico de um giroscópio do tipo diapasão para recuperação de energia será estudado. O giroscópio consiste em duas vigas verticais engastadas sobre uma massa de suspensão. A massa suspensa é sujeita a força de excitação vertical, e pode-se mostrar que o sistema é um sistema parametricamente excitado. Quando as vigas oscilam em fase, a excitação paramétrica pode levar a vibração no movimento horizontal da massa de suspensão. O problema é particularmente interessante para captação ou recuperação de energia. Devido à interação entre os graus de liberdade do sistema, a energia é transferida a partir da direção vertical à direção horizontal. Estudos paramétricos serão realizados para analisar o comportamento dinâmico do sistema no que se refere ao desempenho de recuperação de energia. Será analisado o impacto da introdução de não linearidades de rigidez e amortecimento para aumentar a eficiência do dispositivo. Será analisada também a existência de regimes periódicos e caóticos, e sua influência na transferência de energia entre as direções vertical e horizontal / Abstract: In this work, the dynamical behaviour of a tuning-fork gyroscope for energy harvesting will be studied. The gyroscope consists of two vertical beams fixed on a suspension mass, which is subject to vertical excitation force. It can be shown that the system is parametrically excited. When the beams oscillate in phase, the parametric excitation can lead to vibration in the horizontal direction. The problem is particularly interesting for energy harvesting. Due to the interaction between the degrees of freedom of the system, energy is transferred from the vertical toward the horizontal direction. Parametric studies will be performed to analyse the dynamical behaviour of the system with respect to energy recovery performance. The impact of the introduction of nonlinear stiffness and damping to increase the device efficiency will be analised. The existence of periodic and chaotic regimes will be investigated, and its influence on the energy transfer between the vertical and horizontal directions / Mestre

Present-day builders of harpsichords disagree as to the use of iron or carbon-steel wire in their attempt to duplicate the tonal qualities of the early 16th century instruments. The variations in tone produced by vibrating iron and steel wires may be due, at least in part, to differences in their decay characteristics. A wire was set into vibration by placing a section in a magnetic field and passing a variable-frequency alternating current through it. A condition of resonance was established by appropriately selecting frequencies, lengths, and tensions that would simultaneously satisfy the relationship: fr = n/2L(T/p)1/2. Then measurements of decay time as a function of frequency were made for a variety of typical harpsichord strings: iron, steel, brass, bronze, etc. Samples varied in diameter from 170 mm to 600 mm and the resonant frequencies ranged from 20 Hz to 12,000 Hz. Changes in energy loss through the supports were measured by varying the size and mass of the supports and by modifying the method of attachment of the wire. Differences in loss of energy due to internal friction were noted in the comparison of decay times for different wire materials and diameters. The energy losses due to sound radiation and viscous damping were examined by placing the vibrating wire in a vacuum. Two significant conclusions, among others gathered from the data, indicate that: 1. For similar samples of iron and steel wire vibrating under like conditions, the steel wire will vibrate for a longer period of time than the iron wire. 2. Energy losses to sound radiation and viscous damping greatly exceed all other modes of energy loss from the wire. Suggestions for additional investigations based On the results of this paper are presented in the concluding pages.

This dissertation concentrates on the three principal problems facing experimentalists during their attempts to identify and control lightly damped, large space structures (LSS). The problems are low damping, high modal density, and low natural frequencies of oscillation. They present a blend of difficulties which lead the experimentalist to turn to multiple-input multiple-output (MIMO) identification techniques and high performance compensators. Presented here are two MIMO modal identification techniques: Polyreference, and the Eigensystem Realization Algorithm, as well as two types of compensator-based controllers: Linear Quadratic Gaussian, and Independent Modal Space Control. The various techniques are described in the context of controlling lightly damped LSS. Because the research in this dissertation is primarily applications oriented, problems which experimentalists encounter in the laboratory are addressed as well as the performance of the different identification and control techniques on the test articles. Polyreference and ERA are both shown to perform very well in identifying modal frequencies while overestimating model damping ratios. Simulations show that high modal density combined with noisy data results in standard deviations that increase linearly with respect to mode separation. Pseudo- Inverse IMSC is shown to be robust with respect to system uncertainties. Block Independent Control is shown to possess minor coupling between blocks and provides a powerful control approach to overcome actuator bandwidth limitations. / Ph. D.