Journal of MMIJ
Online ISSN : 1884-0450
Print ISSN : 1881-6118
ISSN-L : 1881-6118
127 巻 , 6_7 号
  • 丸山 正明
    2011 年 127 巻 6_7 号 p. 237-242
    発行日: 2011/05/25
    公開日: 2012/06/06
    ジャーナル フリー
    Japan, where manufacturing is the core industry, is founded on Monozukuri, since it has abundant human resources and few mineral resources . In the near future, the import of mineral resources and raw materials, including rare earth elements, tends to become even more restricted. With this background, Japan has to find ways on how to conduct "natural-resources diplomacy," how to minimize the use of rare earth elements, how to develop alternative materials and recycle technology, and how to build its system. Inevitably, Japan will have to consider its circumstances, while giving answer to these questions, in order to ensure a continuous growth.
    Those who will plan a variety of strategies of growth and implement them need to be blessed by qualities of an entrepreneur. The natural-resources diplomacy, the minimization of the use of rare earth elements, the development of alternative materials and recycling technology, and the formulation of its system - all are difficult challenges. An answer to those issues cannot be obtained easily, unless we try to make plans again and again, untiringly continuing to tackle the difficult tasks. Therefore, Japan is most likely to nurture entrepreneurs with indomitable spirit in the process of seeking its strategy of growth. Continuing to overcome difficult tasks is the only way for Japan to grow; otherwise, the problem over natural resources cannot be resolved.
    † Monozukuri can be translated as "production" or "manufacturing" but includes both tangible and intangible qualities.
  • 伊藤 高敏, 五十嵐 哲, 山本 晃司
    2011 年 127 巻 6_7 号 p. 243-248
    発行日: 2011/05/25
    公開日: 2012/06/06
    ジャーナル フリー
    In order to clarify fracture initiation and propagation in unconsolidated sand, we carried out hydraulic fracturing tests in laboratory focusing on moderate-permeability sand. Silica sand with particle size of about 100 μm has been generally used as the simulated formation materials in laboratory fracturing experiments. Permeability of such sand is high in the order of few darcy. Thus we mixed finer particles of kaolinite with sand, and finally succeeded to prepare the mixture of sand and kaolinite with permeability of about 5 mD. We layered the mixture in a mold to form a cubical specimen of 200 x 200 x 200 mm3. At fracturing tests, the specimen was set in a loading frame of a newly-developed test system. Tri-axial compressive stresses of 2∼3 MPa were applied to the specimen. Fracturing fluid of a machine oil with viscosity of 300 cP was pumped by a constant rate of 10∼100 mL / min into a simulated borehole of a steel pipe which was buried vertically in the specimen, and then the fluid flew out inside the specimen passing through the slit of the steel pipe. After the tests, we excavated the specimen bit by bit and observed how the fracturing fluid invaded into the specimen.
    The laboratory tests demonstrated that fracture-like parting / fracture formation at macro scale was induced in the specimen by fluid injection. During fracture propagation, the pore pressure in the vicinity ahead of fracture tip seemed to increase due to fluid invasion. Fracture patters were obviously changed with injection flow rate. Lower injection flow rate led to a single and straight fracture and higher injection rate led to branching fractures, while in all cases, overall alignment of fractures was in the direction of the maximum horizontal compressive stress. Such phenomena are different from those observed in competent rocks.
  • 董 賀祥, 大久保 誠介, 福井 勝則
    2011 年 127 巻 6_7 号 p. 249-255
    発行日: 2011/05/25
    公開日: 2012/06/06
    ジャーナル フリー
    Bond characteristics considering the effects of concrete strength were investigated by pullout tests. Four polyolefin (PO) fibers were evaluated together with a steel fiber and a polyvinyl alcohol (PVA) fiber. Bond strength or the maximum pullout resistance of each fiber was found to increase with the increase of concrete strength. After careful examination of the experimental data, an experimental equation was proposed stating that the pullout resistance is proportional to 0.785 th powers of the concrete uniaxial-compressive strength. In this study, bending tests of fiber reinforced concrete were also carried out. The results of the bending test were similar to the pullout test; bending strength (modulus of rupture in bending) increased with the increase of concrete strength at similar rate with that of bond strength.
  • 中村 大, 後藤 隆司, 伊藤 陽司, 山下 聡, 鈴木 輝之, 山崎 新太郎
    2011 年 127 巻 6_7 号 p. 256-266
    発行日: 2011/05/25
    公開日: 2012/06/06
    ジャーナル フリー
    In Kitami City, Hokkaido, cracks have been found in bricks, seemingly due to frost damage have been found.
    In this research, we considered three different mechanisms of frost damage such as frost heave phenomenon, one-dimensional freeze-thaw phenomenon, and closed-type freeze-thaw phenomenon.
    We conducted frost heave experiment and two kinds of laboratory freeze-thaw experiments in order to verify the actual mechanism of the formation of the cracks in the bricks.
    From the experimental results, it has been confirmed that frost heave phenomenon does not occur in bricks and that cracks does not occur in bricks due to simple one-dimensional freeze-thaw phenomenon.
    In addition, if bricks do not melt completely during repeated freezing leaving some frozen parts and then the bricks refreeze, the melted parts refreeze surrounded by the frozen parts and cracks then appear in the bricks.
    In this research, this mechanism of frost damage has been defined as closed-type freeze-thaw phenomenon.
    This mechanism of frost damage is different from those considered in the past.
    In this article, this new mechanism of frost damage will be described.
  • 中野 博昭, 大上 悟, 梁井 広太郎, 福島 久哲, 仁科 一彦, 曽我部 信義
    2011 年 127 巻 6_7 号 p. 267-271
    発行日: 2011/05/25
    公開日: 2012/06/06
    ジャーナル フリー
    The harmful effect of impurities on the electrowinning of Zn was evaluated by a cyclic voltammetry. The voltammograms obtained from the solutions containing Cu, Ni and Sb as impurities showed a shift of hydrogen evolution potential to the noble direction and an increase in critical current density for Zn deposition. When the potential of working electrode in the voltammetry was turned back to the noble direction after Zn deposition, the deposited Zn dissolved. The potential required for initiating the dissolution of Zn was somewhat more noble in solutions containing Cu and Ni than in impurity-free solution. In solutions containing Cu and Ni, the further shift of potential to the noble direction after dissolution of Zn brought about the abrupt shift of current density to reduction side for hydrogen evolution. This is attributed to Cu and Ni with low hydrogen overpotential deposited on electrode, and showing that the voltammogram can indicate whether the impurity deposits or not. It could be concluded that the harmful effect of impurities on the electrowinning of Zn can be evaluated by the cyclic voltammetry.