多数の歩行者と歩道橋の連成による振動問題

textapplication/pdfresearch repor

柔軟回転軸に発生する摩擦振動

４ 若手研究及び基礎研究textapplication/pdfresearch repor

同期現象とその応用

textapplication/pdfjournal articl

落下水膜振動の抑制に関する研究(機械力学,計測,自動制御)

This paper describes experimental study on suppressing oscillation of a falling water sheet. Falling water sheet flowing over a dam sometimes oscillates at a low frequency. The water sheet oscillation causes vibrations of paper sliding doors or windowpanes of houses in the neighborhood. Experiental results show that the frequency of water sheet is the same as that of the pressure variation in an air chamber behind a water sheet. Therefore, water sheet vibration is closely related to the pressure variation in an air chamber. We show experimentally that water sheet vibration can be suppressed by setting obstacles at the lower end of a falling sheet or by modifying the shape of the upper end of a falling sheet.textapplication/pdfjournal articl

振動系の同期現象 : 2台のメトロノームを対象とした実験と解析

This paper describes experimental and analytical investigation on synchronized phenomena conducted with two metronomes on a base plate suspended by four wires. Two modes of synchronized phenomena, i.e., in-phase synchronization and out-of-phase synchronization, are experimentally observed. The synchronization mode and frequency in synchronization is strongly influenced by the natural frequency of the base plate. Calculated results based on a physical model of the experimental apparatus show good agreement with the experimental ones, not only qualitively but also quantitatively.textapplication/pdfjournal articl

摩擦力の作用する柔軟回転軸の振動 : 実験(機械力学,計測,自動制御)

A soot blower is used to blow off soot on tubes in a tubular heat exchanger, or a gas heater. The soot blower has a long flexible tube, that is, a lance tube, 8 m long and 76.2 mm in diameter, which is put slowly into/out of a gas heater. Steam flows through the lance tube and is discharged at the free end to blow off soot. The lance tube, rotating slowly about its axis at about 12 rpm, is supported at an intermediate position by a support bearing, that is, a lance bearing. Vibrations and noises occurred in operation while a lance tube is being put into a gas heater slowly. They are considered self-excited vibrations due to friction between the lance tube and the lance bearing. From frequency analysis dominant frequencies of the observed vibrations are the eighth to tenth natural frequencies. Experimental study is done to clarify the mechanism of the vibration. Accordingly, backward whirling motion of a shaft is observed. As the clearance between the flexible shaft and the circular support is reduced, higher modes appear.textapplication/pdfjournal articl

液体を内蔵する中空回転体の安定性 : 液体が遠心力によって排出される影響

This paper describes experimental study on the stability characteristics of a rotor partially filled with water. Constant amount of water is aupplied to the rotor continuously and is discharged radially by centrifugal force. Consequently, the rotor becomes unstable for some rotating speed range. The unstable speed range depends on the water supply rate as well as the amount of water in the rotor. Formardly traveling surface waves are also observed while the rotor undergoes an unstable orbital whirling motion. The wave travels at the same frequency as the rotor vibration frequency. As the water supply rate increases, the rotor becomes more stable.textapplication/pdfjournal articl

固定堰及びため池等の洪水吐における水膜振動・騒音低減工法の開発

This paper describes experimental study on sound reduction from nappe oscillation. Nappe oscillation at weir sometimes produces a low frequency sound. The low frequency sound sometimes causes vibrations of windowpanes of houses and so on. We show that low frequency sound can be suppressed experimentally by setting obstacle at the lower end of a falling water sheet.textapplication/pdfdepartmental bulletin pape

複数回転機械の危険速度通過振動(機械力学, 計測, 自動制御)

Vibration characteristics of a structure on which unbalanced rigid rotors are operated are investigated experimentally and analytically. Rotor speeds cannot exceed a critical speed when drive power to each rotor is not enough. Further running speeds of rotors are entrained into a single speed just below the critical speed and phases of rotor unbalance are locked so as to excite the structure violently. On the other hand, two or three rotors operated by sufficient power supplies can run above the critical speed and unbalance forces cancel each other, that is, vibration is very small. When four rotors are operated with enough power supplies, the phases of rotor unbalance are not locked for speeds above a critical speed.rights: 社団法人日本機械学会 rights: 本文データは学協会の許諾に基づきCiNiiから複製したものである relation: IsVersionOf: http://ci.nii.ac.jp/naid/110006264818/textapplication/pdfjournal articl

スケートボードの推進メカニズム(機械力学, 計測, 自動制御)

This paper describes the propulsion mechanism of a skateboard. We observed the behavior of a rider on a skateboard and built experimental apparatuses. Further we analyze the characteristic by using a two dimensional analytical model. Comparing experimental and analytical results we show that primary propulsion of a skateboard is given by twisting motion of a rider. Propulsion is influenced considerably by the phase difference between twisting motion and tilting the front and rear wheel axles, that is, torque acting on a skateboard and angle of the two axles.rights: 社団法人日本機械学会 rights: 本文データは学協会の許諾に基づきCiNiiから複製したものである relation: IsVersionOf: http://ci.nii.ac.jp/naid/110006153484/textapplication/pdfjournal articl