日本レオロジー学会誌
Online ISSN : 2186-4586
Print ISSN : 0387-1533
ISSN-L : 0387-1533
38 巻, 1 号
選択された号の論文の6件中1~6を表示しています
論文
  • 牛田 晃臣, 長谷川 富市, 鳴海 敬倫, 工藤 昇太
    2010 年 38 巻 1 号 p. 1-8
    発行日: 2010/04/15
    公開日: 2010/04/12
    ジャーナル フリー
    Micro fluid mechanics is one of interesting fields in modern fluid mechanics, because it is applied to physical, industrial, and biological research. In the present study, pressure drops were measured for some kinds of liquids passing through various micro orifices at low Reynolds numbers. It was found that the measured pressure drops almost agree with the prediction by Navier-Stokes equation for orifices smaller than or equal to 50 micron meters in diameter for water and glycerol aqueous solution, but they increase over the prediction for orifices of 100 and 200 micron meters in diameter. Dimensionless pressure drops appear not to be correlated with Reynolds number for some surfactant solutions.
  • 玉野 真司, 伊藤 基之, 楊 文彬, 横田 和彦
    2010 年 38 巻 1 号 p. 9-16
    発行日: 2010/04/15
    公開日: 2010/04/12
    ジャーナル フリー
    In order to investigate the secondary flow patterns of viscoelastic swirling flows in a cylindrical casing with a partially rotating disc, the numerical simulation of the confined swirling flow was performed at low Reynolds numbers, in which the Giesekus model was used as a constitutive equation. The Giesekus model parameters were obtained for polyacrylamide solutions whose concentrations were from 0.025 wt% to 0.2 wt%. The aspect ratio of the distance H between the casing end wall and the rotating disk to the container radius Rc was fixed to H/Rc = 2.0. The ratio of rotating disc radius Rd to Rc, s = Rd /Rc, was 0.4, 0.6 and 1.0. Five kinds of secondary flow patterns, which were classified using the Reynolds and elastic numbers, were observed, which was almost independent of the s.
  • Takehito Kikuchi, Kikuko Otsuki, Junji Furusho, Hiroya Abe, Junichi No ...
    2010 年 38 巻 1 号 p. 17-22
    発行日: 2010/04/15
    公開日: 2010/04/12
    ジャーナル フリー
    There is a strong demand for a human-machine-coexistent machine, e.g. a power-assist system or a computer-aided rehabilitation system, in the context of the super-aging society. In such a human-machine-coexistent system, it is important to guarantee hardware-level safety by utilizing human-friendly actuators. In this paper, we developed two types of compact MR fluid clutches (CMRFC) for human-friendly actuators, which performs about 5Nm torque by applying 1A current and have two different gap-size (50 mm and 100 mm). We tested their static torque. First, we used a conventional MR fluid as a working material of the CMRFCs. Then we used new MRF, which consist of nano-sized (104 nm) Fe particles. According to the experimental results, gap-size affects not only magnetic property but also easiness of filling of MRF (or particles).
  • Xiuying Qiao, Mingwen Bai, Ke Tao, Xinglong Gong, Rui Gu, Hiroshi Wata ...
    2010 年 38 巻 1 号 p. 23-30
    発行日: 2010/04/15
    公開日: 2010/04/12
    ジャーナル フリー
    Polyethyene glycol (PEG)-coated Fe3O4 ferrofluids were prepared by suspending the PEG-coated Fe3O4 nanoparticles in an oligomeric PEG-400 carrier liquid, and their magnetorheological steady flow behavior was investigated. The PEG modification did not change the crystalline structure of Fe3O4, and the PEG-coated Fe3O4 nanoparticles were of nearly spherical shape and had a narrow size distribution (4±1 nm in diameter). These nanoparticles exhibited no significant aggregation in the absence of the magnetic field. Under the magnetic field, the nanoparticles aggregated into string-like clusters oriented in the direction of the field. Correspondingly, the ferrofluids behaved essentially as the Newtonian fluids in the absence of the magnetic field but exhibited, under the magnetic field, a magnetorheological effect, i.e., the increase of the shear stress/viscosity associated with a pseudo-plastic and thinning character with no real yield stress. This lack of the real yield stress, possibly reflecting the absence of huge clusters connecting the measuring parts (plates) in the rheometer, suggested that the magnetorheological effect of the ferrofluids were related to deformation/disruption of the magnetically formed clusters of finite sizes under the shear. Interestingly, this effect was most significant for the Fe3O4 nanoparticles having an intermediate amount of PEG coating. This result suggested a possibility that the relaxation of PEG chains in the coating layers of nanoparticles in the clusters contributed to the magnetorheological effect.
  • Kenji Nakamura, Shuta Takase, Toshiyuki Shikata
    2010 年 38 巻 1 号 p. 31-40
    発行日: 2010/04/15
    公開日: 2010/04/12
    ジャーナル フリー
    We investigated the linear and non-linear viscoelastic behavior of aqueous solutions of hybrid threadlike micelles formed by cetyltrimethylammonium poly (p-vinylbenzoate) (CTAPVB) and some additive simple salts at various pH values. The system showed marked viscoelasticity at lower pH values ca. 2.5. The obtained mechanical relaxation time of the system was proportional to the molecular weight of the incorporated CTAPVB, and lengthened strongly depending on the species of anions in the order of the Hofmeister series. Remarkable stress overshoot phenomena related to strain-hardening were observed under start-up shear flow experiments at high shear rates. Distinct shear-thickening never found in the previously studied threadlike micellar systems was observed in the system. The essential mechanism for viscoelastic behavior unique to the present hybrid threadlike micellar system was discussed.
  • 浦川 理, 信川 省吾, 四方 俊幸, 井上 正志
    2010 年 38 巻 1 号 p. 41-46
    発行日: 2010/04/15
    公開日: 2010/04/12
    ジャーナル フリー
    We studied dielectric and viscoelastic relaxation behavior for blends of low mass compounds (LM) and polymers. Specifically the polymers used are polystyrene (PS) and poly(vinylethylene) (PVE), and the LMs are alkyl-cyanobenzene (nCBz, n = 0,5), alkyl-cyanobiphenyl (nCB, n = 0,1,3,5,7), and alkyl-cyanoterphenyl (nCT, n = 5), where n represents the number of carbons in the normal alkyl groups of the LMs. The objective of this study is to clarify the effect of the sizes of LM molecules and those of polymer segments on the cooperative dynamics between those two dynamical units in the miscible state. Due to large dipole moment of the cyano-group, only the LM motions were observed by dielectric measurements even for blends with low LM content such as 5 %. On the other hand, viscoelastic terminal relaxation reflects the polymer component dynamics. By performing both dielectric and viscoelastic measurements we found the followings. (1) Rotational motion of the smallest LM, i.e., 0CBz, decoupled with the segmental motion of PS, however the other LMs with larger sizes than 0CBz exhibited cooperative dynamics with the segmental motion. (2) Below the glass transition temperature of LM / polymer mixtures, fast relaxation process (β relaxation) corresponding to the spatially restricted motion of LMs in the glassy state was observed. However for the mixtures of 5CT(5 wt%) / PS and 5CB(5 wt%) / PVE, b relaxation did not appear. This result suggests that the local wiggling motion of LM (β relaxation) is highly suppressed when the LM size becomes large and comparable with the segmental size of a polymer.
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