Thesis (M.S. in mechanical engineering)--Washington State University. / Includes bibliographical references.

On January 1, 2000, the Amateur Softball Association of America (ASA) imposed maximum bat performance limitations on commercial softball bats. The ASA adopted a testing standard defined by the American Society of Testing and Materials (ASTM) to determine the bat performance factor (BPF), a normalized coefficient of restitution that must be less than 1.2 for the bat to be eligible for ASA sanctioned events. The ASTM standard requires that the softball strike the bat, which is free to rotate in the horizontal plane, at 26.8 mfs ± 0.3 mfs (88 ftfs ± 1 ftfs) with little or no spin. The central project goal was to develop the ASTM test apparatus, which consisted of a precision ball launcher, a pivoting stage for the bat, and instrumentation for velocity measurements. The key feature of the testing apparatus developed in this project was the ability to measure the rebound velocity of the ball directly-ASTM method derives the ball rebound velocity by assuming the bat behaves as a rigid body and applying conservation of angular momentum. Tests revealed a discrepancy in the BPF between the ASTM method and an alternative method,. termed the direct method, which uses the direct measurement of the ball rebound velocity. Furthermore, the ASTM method proved to be very sensitive to parameter errors, demonstrated by magnification factors between 2.0 and 3.0. The direct method was insensitive to parameter variation with magnification factors between o and 1.0. The ball rebound velocity discrepancy was also analyzed with mechanism simulation software. A three-degree-of-freedom model of the bat was used to test the effects of elasticity and pivot friction. The analysis determined that applying conservation of angular momentum on an elastic body caused transient errors in the derivation of the ball rebound velocity; and pivot friction significantly affected the motion of the bat and thus, the derived ball rebound velocity. The experimental results show that the direct method was more accurate than the ASTM method in calculating the BPF; and the conclusion of the analytical model shows that the ASTM method can be corrected by precisely identifying external moments in the system.

Thesis (Ph.D.)--University of Western Australia, 2003.

Thesis (M.S. in mechanical engineering)--Washington State University, August 2006. / Includes bibliographical references.

[Formulae and special characters can only be approximated here. Please see the pdf version of the abstract for an accurate reproduction.] Ball-impact injuries in baseball, while relatively rare, have the potential to be catastrophic. These injuries are primarily attributed to impact by the ball after it has been hit, pitched or thrown. As the closest infielder to the hitter, the pitcher is at greatest risk of being struck by the batted ball. This thesis investigated the influence of bat and ball design on ball exit velocity (BEV) and the potential for impact injury to pitchers. Finite element analysis (FEA) was used to quantify the dynamics of bat-ball impact for bats of various moment of inertia and baseballs with different mechanical properties. The analysis was conducted using ANSYS/LSDYNA explicit dynamics software. To replicate a typical bat-ball impact in the field, the model required input of bat linear and angular velocity and orientation in three-dimensional (3-D) space, at the instant prior to impact. This data was obtained from 3-D kinematic analysis using two high-speed video cameras operating at 200 Hz. Seventeen high-performance batters used a wood bat and a metal bat of equal length and mass to hit baseballs thrown by a pitcher. Hitters developed significantly higher resultant linear velocity for both the proximal (38.3 ± 1.8 ms-1;) and distal (8.1 ± 1.8 ms-1) ends of the metal bat (compared with 36.4 ± 1.7 ms-1 and 6.9 ± 2.1 ms-1 respectively for the wood bat). They also achieved a significantly more “square” bat position just prior to impact with the ball (264.3 ± 9.1 deg compared with 251.5 ± 10.4 deg). These factors are important in transferring momentum to the batted ball. Mathematical description of the large-deformation material behaviour of the baseball was also required for this analysis. Previous research is limited to compression tests to 10 % of ball diameter, despite conjecture that during impact with the bat, the ball might deform to 50 % of its original diameter. Uniaxial quasi-static compression tests on seven models of baseballs investigated baseball behaviour during deformation to 50 % of ball diameter. The resulting force-displacement relationship was highly non-linear. Hence FEA was used to derive and verify a relationship to describe the time-dependent and elastic behaviour of the ball during the 1 ms period typical of bat-ball impact. The results of the bat-ball impact analysis indicated that for hits made at the point of maximum momentum transfer on the bat, the metal bat produced greater BEV than the wood bat (61.5 ms-1 and 50.9 ms-1 respectively). The higher BEV from the metal bat was attributed to greater pre-impact bat linear velocity, and bat orientation during impact. The more perpendicular horizontal orientation of the metal bat at the instant of impact resulted in a greater proportion of resultant BEV being directed in the global x-direction (toward the pitcher), compared with the wood bat. This indicates increasing bat moment of inertia (the relative mass of the bat barrel) may be a potential control strategy for BEV. BEV was also reduced for impacts using a baseball with values for instantaneous shear and relaxed modulii approximately 33 % less (9.9 % reduction in BEV for metal bat, 9.7 % for the wood bat).

Submitted by Kamila Costa (kamilavasconceloscosta@gmail.com) on 2015-08-13T13:58:22Z No. of bitstreams: 2 Dissertação - Claudio L de O Filho.pdf: 2340658 bytes, checksum: 48ae8b251a67478fbd575dfdf9421e56 (MD5) ficha catalografica.pdf: 1852 bytes, checksum: 8abcc5e009ccf6d18dcfaad0e62e232a (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-08-14T19:27:02Z (GMT) No. of bitstreams: 2 Dissertação - Claudio L de O Filho.pdf: 2340658 bytes, checksum: 48ae8b251a67478fbd575dfdf9421e56 (MD5) ficha catalografica.pdf: 1852 bytes, checksum: 8abcc5e009ccf6d18dcfaad0e62e232a (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2015-08-14T19:31:42Z (GMT) No. of bitstreams: 2 Dissertação - Claudio L de O Filho.pdf: 2340658 bytes, checksum: 48ae8b251a67478fbd575dfdf9421e56 (MD5) ficha catalografica.pdf: 1852 bytes, checksum: 8abcc5e009ccf6d18dcfaad0e62e232a (MD5) / Made available in DSpace on 2015-08-14T19:31:42Z (GMT). No. of bitstreams: 2 Dissertação - Claudio L de O Filho.pdf: 2340658 bytes, checksum: 48ae8b251a67478fbd575dfdf9421e56 (MD5) ficha catalografica.pdf: 1852 bytes, checksum: 8abcc5e009ccf6d18dcfaad0e62e232a (MD5) Previous issue date: 2015-06-19 / Não informada / The purpose of this study was to evaluate species of woods from Amazonia forest with technological potential for making baseball bats. For this, it was used as a parameter fundamental properties of wood inherent in the product. First was created a database with all the technology described species, including the very American species to baseball bats. Given the wide variety of species from Amazonia forest , the method used three steps in order to sift through the data. It began with the multivariate analysis, which determined 4 groups by similarity. These groups was selected those who had species from Amozonia forest along with other species used for baseball bats (Acer saccharum, Fraxinus americana, Betula alleghaniensis and American Patagonula).Later, the species from the selected groups were compared to the list of commercially exploited woods. Crossing intersection removed all species with different grain classification then straight grain type. Therefore, there were only three species - Endopleura uxi, Qualea paraensis and Roupala montana, the last two of which have been selected for making prototypes, since the first unfavorable characteristics presented in the drying process. The prototypes were evaluated by amateur players from adult and master Amazonas selection team. From all species from Amazonia forest, the Qualea paraensis was the one that had the best result, with its final mass of 838g to 12.9% moisture content, similar to the original baseball bats - which demonstrates its quality, since the mass factor It has great influence on product qualification. / A proposta do trabalho foi avaliar espécies de madeiras amazônicas com potencial tecnológico para a confecção de taco de beisebol. Usou-se como parâmetro propriedades fundamentais das madeiras inerentes ao produto. Primeiramente criouse um banco de dados com todas as espécies catalogadas tecnologicamente, inclusive com as espécies americanas próprias para tacos de beisebol. Tendo em vista a grande variedade de espécies amazônicas, o método utilizou três etapas a fim de peneirar os dados. Iniciou-se com a análise multivariada, a qual determinou 4 grupos por similaridade. Destes grupos selecionou-se aqueles que haviam espécies amazônicas junto com outras espécies utilizada para tacos de beisebol (Acer saccharum, Fraxinus americana, Betula alleghaniensis e Patagonula americana). Posteriormente, fez-se uma cruzamento das espécies pertencentes aos grupos selecionados com a lista de madeiras exploradas comercialmente. Da interseção do cruzamento eliminou-se todas as espécies com classificação de grã diferente do tipo direita. Por conseguinte, restaram apenas três espécies – Endopleura uxi, Qualea paraensis e Roupala montana, das quais as duas últimas foram selecionadas para a confecção de protótipos, já que a primeira apresentou características desfavoráveis no processo de secagem. Os protótipos foram avaliados por jogadores amadores da seleção do Amazonas adulto e master. Das espécies amazônicas, a Qualea paraensis foi a que obteve o melhor resultado, tendo sua massa final igual a 838g a 12,9% de teor de umidade, similar aos os tacos originais - o que demostra sua qualidade, uma vez que o fator massa tem grande influência na qualificação do produto.

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