著者

木之下 博 政安 亮祐 藤井 正浩

出版者

一般社団法人 日本トライボロジー学会

雑誌

トライボロジスト (ISSN:09151168)

巻号頁・発行日

vol.58, no.11, pp.832-840, 2013-11-15 (Released:2018-05-08)

参考文献数

22

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Sandfish (Scincus scincus), which is kind of reptile living in desert, can move in sand like swimming. It is thought that since sandfish has a low friction scales, it is able to do that. However, the mechanism of the low friction property of the scales is not yet known. In this study, a micro structure of sandfish’s scales was investigated, and their tribological properties under μN loads were measured. Cuticle-like structure, which is observed on human hairs, appeared on the scales. Detected elements on the scales were O, C, N, and S. Ca and Si, which are elements of hard shells and bones, were not detected. A contact angle of sandfish’s scale was around 90º, and polytetrafluoroethylene (PTFE) and polyimide (PI) had contact angles of approximately 110º and 60º, respectively. However, an adhesion force of sandfish’s scales was lower than those of PTFE and PI. With the exception of a few frictional conditions, a friction force of sandfish’s scales was lower than those of PTFE and PI, which would result from the low adhesion force of sandfish’s scales.

著者

藤井 正浩 國冨 裕太 石田 浩規

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.80, no.820, pp.TRANS0339, 2014 (Released:2014-12-25)

参考文献数

8

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In order to clarify the effect of surface profile on friction characteristics of viscoelastic material used for oil seal, sliding test was conducted under oil lubrication with the NBR (Nitrile Butadiene Rubber) specimen in combination with steel specimen. The sliding surface profiles with different feature in the steel specimens were introduced by polish process and blast process. The NBR specimens with different surface feature were also employed. Under a low load condition, steel specimens with plateau surface showed the lower friction coefficient. The reduction of contact area and pocket effect could lead to the lower friction coefficient. Similar effect was provided by the NBR specimens with rough surface or dimples. Friction behavior under a low load condition was influenced by adhesion force. The adhesion force decreased with increasing surface roughness, that is with decreasing contact area. Therefore, the friction coefficient decreased with increasing surface roughness in NBR specimen. The friction coefficient of the NBR specimen with dimples which had small asperity and large concave portion was remarkably small under a low load condition. On the other hand, under a high load condition, where the deformation of NBR specimen was rather large, the effect of surface profile on friction coefficient was small.

著者

木之下 博 政安 亮祐 藤井 正浩

出版者

一般社団法人 日本トライボロジー学会

雑誌

トライボロジスト (ISSN:09151168)

巻号頁・発行日

vol.59, no.9, pp.577-585, 2014-09-15 (Released:2018-02-23)

参考文献数

12

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It is thought that sandfish skink, living in desert, has scales that have low friction and high wear resistance properties. In previous study, we investigated the tribological properties of sandfish's scales under micro newton loads. It is found that the scales have low adhesion forces, which would lead to the low friction property. In this study, a tribological property of sandfish's scales was investigated under milli newton loads (of 3, 5, 10 mN) to investigate wear resistance property mainly. Tribological tests were also carried out using polytetrafluoroethylene (PTFE) and polyimide (PI) for comparison with the scales. Using a SUJ2 ball with a diameter of 1 mm, wear of sandfish scale was not occurred or much lower than those of PTFE and PI. When wear was not happened for sandfish's scale in the relative low contact pressure, a friction coefficient of the sandfish's scale was lower than those of PI and PTFE. When a tungsten probe with an apex diameter of 5 μm was used in which contact pressure was huge with compare to that using the SUJ2 ball, wears on all samples were observed. In the relative high contact pressure, the friction coefficient of sandfish's scale was higher than that of PI. Under the milli newton loads, the microstructure of the sandfish's scale did not affect its tribological property.

著者

平山 知央 松野 典朗 藤井 正浩 樋田 光

出版者

一般社団法人電子情報通信学会

雑誌

電子情報通信学会技術研究報告. MW, マイクロ波 (ISSN:09135685)

巻号頁・発行日

vol.101, no.553, pp.65-70, 2002-01-10

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2段パワーアンプにおいて、バイアス条件を調整して初段と終段で生じる相互変調歪みを相殺し、高出力時における効率を向上させる手法を提案した。初段・段間整合回路、バイアス回路を内蔵したW-CDMA用パワーアンプInGaP/GaAs HBT MMICに本手法を用いることにより、電源電圧3.6Vにおいて出力26dBm、効率44%、利得27.9dBm@ACPR=-35dBcという高効率動作を達成した。