著者

永島 唯哉 池田 生馬 岩附 信行

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.873, pp.18-00439, 2019 (Released:2019-05-25)

参考文献数

13

被引用文献数

1

---

When one rides a car on a gravel road, a noise due to collision of gravels rolled up by tires makes him uncomfortable. The collisions are assumed as random impacts with respect to mass, collision time, position, velocity, angle and so on. In order to probabilistically estimate the noise, the time history of impact force in the case where a force sensor on a rigid pendulum hits a peripherally clamped thin rectangular plate is precisely measured for various impact speeds, angles and positions. The vibration response and sound pressure radiating from the plate are then estimated with the measured impact forces based on Rayleigh-Ritz method and impulse response method. It was then revealed that the time history of impact force could be represented with a certain time function for any impact speeds, angles and positions and that the component of the impact force perpendicular to the plate determined the maximum of the impact force. The time history of impact force can also be approximated as a superposition of the extreme function and Gaussian function. The estimated vibration acceleration of the plate and sound pressure agree very well the measured values. The noise generated by random impacts was estimated probabilistically. It was found that the noise strongly depends on the natural vibration modes of the plate.

著者

木村 直人 岩附 信行 池田 生馬

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.84, no.863, pp.18-00092, 2018 (Released:2018-07-25)

参考文献数

12

被引用文献数

2

---

Linkage mechanisms with 1 DOF consisting of links and lower pairs cannot completely generate the specified output motion. In order to solve that problem, the novel kinematic pair with 1 DOF is developed. This kinematic pair consists of two surfaces in line contact with each other and can generate relative rolling motion along the specified spatial trajectory. Thus, it is called the spatial rolling contact pair. The relative rolling motion along an arbitrary trajectory is specified so as to satisfy the kinematic condition of the spatial rolling motion. Rolling contact surfaces which can generate the specified motion are designed based on ruled surfaces of the instantaneous screw axis. Some norms to evaluate stability of rolling contact between designed pairing elements are introduced, and the pairing elements are constrained by many linear elastic elements so as to satisfy them. Some examples of the proposed kinematic pair are designed, and one of them is manufactured as a prototype. By some experiments, it is confirmed that the prototype generates the specified rolling motion and keeps rolling contact by designed elastic constraint. Finally, it is revealed that a spatial 4-bar mechanism with the spatial rolling contact pair can completely generate the specified output motion and can be synthesized more easily than the mechanism synthesized by conventional methods.

著者

稲垣 洋輔 香川 美仁 森川 広一 岩附 信行 林 巖 細川 俊之

出版者

一般社団法人日本機械学会

雑誌

Dynamics and Design Conference : 機械力学・計測制御講演論文集 : D & D (ISSN:13480235)

巻号頁・発行日

vol.2000, 2000-09-01

---

This paper describes the optimization of the case cover of small hard disk drive (HDD) used for personal computers. Small Hard disk drives are one of the main causes of noise radiated from personal computers or workstations. Nowadays the rotational speed of spindle motor used to rotate disks is increased year by year in order to increase the transfer speed. It is afraid that the noise radiated from small HDD is increasing more and more accordingly. Optimization of the shape of ribs which are attached on the case cover are hence tried in order to reduce the noise radiated from small HDD used for personal computers. Firstly, the natural modes of flexural vibration of the case covers of small HDD, which were made of aluminum, steel, and brass, were experimentally determined, and the natural frequencies, mode shapes, and damping coefficients were determined. Secondly, the sound power radiated from the case covers was theoretically estimated dy using the results of FEM modal analysis, was made sure to coincide with the measured values. Finally, the sound powers radiated when the thickness of the case cover was uniformly thickened, and when radial ribs, lattics ribs, or circular ribs were attached on the case cover, were compared. As the results, it has been revealed that the sound power is more reduced as the thickness is increased, the increase of thickness is effective especially to the low modes. For attaching ribs, radial ribs were most effective, and the sound power was more reduced as the number of ribs and/or the height was increased.

著者

林 巌 岩附 信行

出版者

東京工業大学

雑誌

基盤研究(B)

巻号頁・発行日

1996

---

我々の住む社会において,機械の振動,騒音,不快さといったNVHの分野における問題を解決し,人間にとって快適な居住空間を作り出すことが重要な課題となっている.しかし,機械から発生する騒音を最小にし,かつ心地よくリズミカルな音で機械の稼働状況を知らせる静音最適構造設計手法といったものがまだ十分に明らかにされていない.そこで本研究では,すずむし,こおろぎ,あるいはかんたんなどの鳴き声の美しい昆虫の翅の構造と発音メカニズムを工学的に解明するため,昆虫の翅の構造の精密測定と振動モード解析を行い,そしてその結果を工学的に静音最適設計へ応用するため,平板を対象として厚さを局部的に変更し,またいくつかの編み目パターンを掘り,発生する振動モードおよび音のコントロールについて検討した.本研究で,得られた結果は以下の通りである.(1)昆虫の翅の構造の精密測定こおろぎの翅をプラスチックでモ-ルドし,微少量ずつ削り出し断面を写真撮影する方法により,翅脈のため凹凸が激しい翅の形状を精密に測定でき,翅脈は波板状の構造であることが分かった.(2)昆虫の翅の振動モード解析(1)で測定したデータから,こおろぎの翅の有限要素モデルを作成し,翅脈の端にある翅と胴体の付け根,およびこすり器にたいして種々の境界条件を与え振動モード解析を行った結果,こおろぎの鳴き音の主成分の周波数に一致する固有振動数は見られなかったが,音に寄与している振動モードを確認することができた.(2)編み目模様をもつ平板の振動モード特性局部的な厚さの変化を含む編み目パターンをもつ平板の実験モード解析を行った結果,編み目による固有振動数および振動モードの特性を明らかにすることができ,編み目の変更による音響放射パワー最小化のための検討を行った.