著者

酒井 忍 保富 大輔 史 金星 浦上 晃 溝口 正人

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.85, no.877, pp.19-00118, 2019 (Released:2019-09-25)

参考文献数

19

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In rubber baseball games, when the rubber ball is hit by a baseball bat, the rubber ball is deformed greatly comparing to an official baseball ball, and the batted ball speed decreases due to the energy loss during the deformation. Since the new rubber ball has been applied in games from 2018, the material properties and the restitution characteristics of the new rubber ball attract plenty of attention among scholars. In this study, the difference of the material properties and the restitution characteristics between the new and old rubber balls is investigated deeply by the static compression and collision tests. According to the static compression test, we find that the new rubber ball is harder and more difficult to generate deformation than the old one. In the collision test, the rebound ball speeds of both of the new and the old balls become faster when using a smaller diameter of steel cylinder instead of baseball bat, and the rebound ball speed of the new ball is slower than that of the old one under the same experimental conditions. Furthermore, to develop high performance baseball bats adapting to the new rubber baseball, the diameter of the baseball bat is studied by the impact simulation based on the finite element analysis. In the simulation, the batted ball speed under the analytical conditions of different offset heights and different barrel diameters of the bat are evaluated considering the initial spin. As a result, the batted ball speed generated by the bat with diameter φ55 mm is faster than generated by the bat with diameter φ70 mm when the offset height range is smaller than 14.6 mm, so that the bat diameter φ55 mm is recommended according to the present work.

著者

史 金星 山田 陸人

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.89, no.922, pp.23-00054, 2023 (Released:2023-06-25)

参考文献数

20

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Lure fishing is a well-known type of fishing that uses artificial lures instead of traditional live baits. Vibratory lure is a kind of lures performs greater vibration behavior than other kinds of lures. In common, more excellent vibration behavior of vibrating lure can attract carnivorous fish more efficiently. Up to now, lure design is generally based on the intuition of the designer, and there is little academic research on vibrating lure. In this study, we build the finite element model of a commercial vibration lure using a 3D scanner at first. Then, fluid–structure interaction (FSI) analysis is carried out to reproduce underwater motion of the vibration lure, where we can calculate the frequency of the flow induced vibration (FIV). Finally, in order to obtain the best FIV behavior of the vibration lure, based on the simulation results of FSI analysis, we perform structural design optimization of the vibration lure using the Box-Behnken design method, which belongs to the response surface methodology. In the structural design optimization, we set three design variables, which are the positions (x and z) of the weight placed in the lower part of the lure, and the eye position (i.e., the knot position between fishing line and lure) along the lure body. According to optimal results, the highest frequency of the FIV can reach 7.07 Hz. However, the present work is still in the early stage of the academic research on lure design, we aim to develop more optimization method for lure design that make lure fishing more interesting for both beginners and anglers.

著者

史 金星 大村 渓一朗 下田 昌利

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.83, no.853, pp.17-00077-17-00077, 2017 (Released:2017-09-25)

参考文献数

28

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Because of their superior mechanical, structural, and electronic properties, carbon nanomaterials (CNs) (e.g. graphene sheets and carbon nanotubes) are supposed to be base materials for nanoelectromechanical systems (NEMS). In the present work, we propose a structural optimization method of carbon nanomaterials by introducing topological defects, which consists of the molecular mechanics method, the free-form optimization method, the Phase-Field-Crystal (PFC) method, Voronoi tessellation, and molecular dynamics (MD) simulation. The C-C bonds of CNs are simulated as equivalent continuum beams by a combination of molecular and continuum mechanics, so the atomic structures of CNs can be treated as frame structures. We adopt the free-form optimization method for frames to determine the optimal shapes of CNs in stiffness maximization problem. For obtaining the stable atomic structures of the optimal shapes of CNs, topological defects are introduced in the optimal shapes of CNs using a combination of PFC method, Voronoi tessellation, and MD simulation. The numerical results show that the compliance of CNs can be significantly reduced according to the structural optimization method, which is helpful for designing CNs components in NEMS.