Thesis (M.S.)--University of Wisconsin--Madison, 1975. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

The problem of this study was to investigate the resilient effects of selected string tensions in various types of tennis rackets. The rackets selected were the Wilson T-2000, Head Professional, Head Master, Dunlop Fort, Dunlop Austral, and Yamaha Composite. Each racket was randomly strung and tested at 45, 52.5, and 60 pounds of string tension. The testing involved dropping a tennis ball 100 inches onto the racket face, which was stationary, and measuring the height of the ball bounce. The data collected from the rackets and string tensions were analyzed by the analysis of variance and the .05 level of confidence was used to determine significance. A significant difference occurred between the Head Professional and Wilson T-2000 and the Head Professional and Yamaha Composite. Significant differences occurred between all three string tensions.

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The aim of this study was to evaluate, by means the axial pull-out strength, the influence of using conventional metal brackets and metal and ceramic self-ligating, in the intensity of the frictional force generated when associated with orthodontic wires of circular and rectangular sections of different diameters. Three types of brackets were used in this work: metallic conventional (G1); metallic self-ligating (G2) and ceramic self-ligating (G3). Bars were made of polyethylene (10 cm long x 3.5 cm thick x 3.5 cm wide) where three brackets were bonded (canine, first and second premolars rights) previously aligned and leveled. The groups of brackets were associated with orthodontic wires, stainless steel (Cr-Ni) of circular and rectangular sections in three dimensions, F1: 0.020" circular, F2: 0.017 x 0.025 , F3: 0.019" x 0.025" rectangular, resulting Groups: G1F1, G1F2, G1F3, G2F1, G2F2, G2F3, G3F1, G3F2 and G3F3. For each type of bracket were prepared 10 specimens. All groups were tested in a universal testing machine (EMIC DL 2000). easurements of friction were obtained every 0.5 mm distance to travel a total of 5 mm. The values found were submitted to the analysis of Kruskal-Wallis and Tukey. The results showed that self-ligating brackets showed lower friction resistance when compared to conventional brackets used with circular and rectangular wire sections. The differences in the values of the friction encountered between conventional and selfligating brackets have a direct influence of association with the section of wire used. / O objetivo deste estudo foi avaliar, por meio de ensaio de tração, a influência do uso de braquetes convencionais metálicos e autoligados metálicos e cerâmicos, na intensidade da força de atrito gerado, quando associados a fios ortodônticos de secções circular e retangular em diferentes diâmetros. Três tipos de braquetes foram utilizados neste trabalho: convencional metálico (G1); autoligado metálico (G2) e cerâmico (G3). Foram confeccionados barras em polietileno (10 cm de comprimento x 3,5 cm de espessura x 3,5 cm de largura) onde foram colados três braquetes (canino, primeiro e segundo pré-molares superiores direitos) previamente alinhados e nivelados. Os grupos de braquetes foram associados a fios ortodônticos de aço inoxidável (Cr-Ni) de secções circulares e retangulares de três dimensões, F1: 0.020 circular; F2: 0.017 x 0.025 , F3: 0.019 x 0.025 retangulares, originando os grupos: G1F1, G1F2, G1F3, G2F1, G2F2, G2F3, G3F1, G3F2 e G3F3. Para cada tipo de braquetes foram confeccionados 10 corpos de prova. Todos os grupos foram testados em uma máquina de ensaios universais (Emic DL 2000) . As mensurações do atrito foram obtidas a cada 0,5 mm de deslocamento até percorrer um total de 5 mm. Os valores achados foram submetidos as análises de Kruskal-Wallis e Tukey. Os resultados demonstraram que os braquetes autoligados apresentaram menor resistência ao atrito em relação aos convencionais quando utilizados com fios de secções circular e retangular. As diferenças nos valores do atrito estático encontradas entre os braquetes autoligados e convencionais possuem influência direta com a secção e espessura do fio utilizado.