Thesis (M.S.)--Rochester Institute of Technology, 1989. / Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Jeffrey K. Bennighof. Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2002. / Vita. Includes bibliographical references. Available also from UMI Company.

Thesis (Ph. D.)--University of Rhode Island, 2006. / Includes bibliographical references (leaves 108-112).

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaf 103). Also available via the Internet.

Made available in DSpace on 2014-06-11T19:28:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-12Bitstream added on 2014-06-13T19:37:17Z : No. of bitstreams: 1 mendonca_wrp_me_guara.pdf: 1680697 bytes, checksum: bcb5ba9c7460283227da43d67a5ca331 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Estruturas e máquinas em regime operacional usualmente são submetidas a carregamentos dinâmicos ocasionados por vibração. Este fenômeno é em grande parte prejudicial, tendo em vista que podem causar falhas por fadiga, ruídos indesejáveis, etc. Com objetivo de minimizar e avaliar níveis de vibração em sistemas estruturais, técnicas de modelagem teórica e experimental vêm sendo utilizadas com freqüência. Dentre diferentes técnicas aplicadas à avaliação do comportamento dinâmico de estruturas, a análise modal figura como uma das principais.O presente trabalho tem como objetivo implementar um método de identificação de parâmetros modais no domínio da freqüência, de estruturas com vários graus de liberdade (MDOF). O método foi implementado em um ambiente computacional de baixo custo. O programa desenvolvido possibilita através de suas interfaces gráficas identificar os parâmetros modais de dados experimentais de uma estrutura metálica ensaiada, simular os modos de vibrar identificados da estrutura e permite de forma pratica que os usuários com poucos conhecimentos em análise modal interajam com todo o processo de análise dos dados experimentais. / Structures and machines in operational regime are usually submitted to dynamic loads caused by vibration. This phenomenon is largely harmful, considering can cause cracks for fatigue, undesirable noises, etc. With objective of minimize and evaluate vibration levels in structural systems, techniques of theoretical and experimental modeling have been used frequently. Among different techniques applied to the evaluation of the dynamic behavior of structures, the modal analysis present as one of the main. The present work has as objective implements a method of identification of modal parameters in the domain of the frequency to structures with multi degrees of freedom (MDOF). The method should be implemented in a low cost software. The developed software had made possible through their graphic interfaces to identify the modal parameters of experimental data of a rehearsed metallic structure, to simulate the modes of vibration identified and make possible users with few knowledge in modal analysis interact with the whole the process of analysis of the experimental data.

The sound radiated during a tennis impact has been shown to greatly influence the perception of 'feel' but has also been suggested to contribute to the perception of equipment quality, as is the case with many other consumer products. In an industry that is governed by design limitations, tennis racket manufactures are continually aiming to differentiate their products from their competitors' and the sound character of a racket is seen as one such method to do so. In order to control the sound radiated from a tennis racket it was first necessary to identify how a tennis racket radiates sound. Through a number of controlled player tests, involving groundstrokes and serves, the sound was recorded along with measurements of the physical vibrations excited in the frame. Analysis of the data revealed typical characteristics of the sound in the time and frequency domain. The sound was split into two sections to aid the analysis; an initial impulsive component that decayed very quickly and a ringing component that was of much lower amplitude but decayed at a much slower rate. The evolution of the frequency content over time was also investigated, however, the data provided much more information as to where each frequency component originated by analysing the data together with the experimental modal analysis data. The experimental modal analysis of a tennis racket was a vital stage in understanding which components of the racket were responsible for radiating the identified frequency component in the sound spectrum. The investigations identified frame bending modes, out-of-plane and inplane, as well as torsional modes, hoop modes and stringbed modes. To enable direct comparison between the natural frequencies excited during a tennis shot and the frequencies recorded from a freely suspended racket, the effect of the hand on the modal behaviour of the racket was analysed; experimental modal analysis data from a hand-gripped racket was compared with data generated by adding simulated mass to the modal model of the freely suspended racket. The first stringbed mode was identified as a key contributor to the sound of the racket, especially in the ringing component of the sound. Analysis of the physical vibrations in the frame following a tennis shot revealed that the first stringbed mode excited the frame of the racket, which is iv thought to be the reason why stringbed modes contribute to the sound more so than their surface area would suggest that they are capable of. Analysis of the relationship between subjective perceptions of players and calculated sound metrics suggest a negative correlation exists between the duration and loudness of a tennis shot and the appeal of the sound. Further investigations involving a jury to evaluate the appeal of a tennis impact sound, modified in terms of duration, revealed further evidence to support the theory that tennis impact sounds of greater duration are less appealing than those that decay quickly. This is the first study to investigate the sound radiated from a tennis racket and has identified how the sound is radiated from the racket and also suggests which parameters of the sound are considered appealing to tennis players. With this information it is possible to suggest design modifications that would influence the sound of a tennis racket in a predictable manner.

No description available.

To provide the average golfer with more consistent results, manufacturers have continued to improve the available equipment. This has led to larger club-heads, with larger ?sweet spots?, different shaft thickness for different swing styles, and the use of advanced materials, such as graphite and titanium, for the construction. The development of improved equipment, which utilizes advanced materials, has spurred the need for advanced scientific analysis using a variety of techniques. Among the most prevalent of these methods are finite element analysis and experimental modal analysis, and use of these techniques in examining a golf club is the focus of this research. The primary goals of this work are the development and correlation of an appropriate finite element model, the characterization of the hands-free boundary condition and the examination of the club golf dynamic response. To accomplish these objectives, the physical parameters of the golf club are determined to develop the finite element model. The analysis of natural frequencies and mode shapes correlate well with the results extracted from experimental modal analysis for the free-free and clamped-free boundary conditions. With the correlation established, a third boundary condition, hands-free, is tested experimentally to ascertain the effects of the golfer?s grip on the boundary conditions. With the FEA model confirmed, a nonlinear dynamic response of the club during the down-swing is investigated using the nonlinear solver in Algor, and the club-head position relative to the shaft is predicted. / Master of Science

No description available.