材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
49 巻 , 3 号
選択された号の論文の19件中1~19を表示しています
  • 尾方 成信
    2000 年 49 巻 3 号 p. 250-256
    発行日: 2000/03/15
    公開日: 2009/06/03
    ジャーナル フリー
  • 尾方 成信, 北川 浩, 広崎 尚登, 安本 弘昭
    2000 年 49 巻 3 号 p. 257-262
    発行日: 2000/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    The deformation properties of β-silicon nitride under shear loading are investigated by molecular dynamics simulation using a three body empirical potential. Two cases of shear deformation, {1010} ‹0001› and {1010} ‹1210›, are analyzed, which are reported as the slip systems on the basis of experimental observation. The ideal shear strength of the β single crystal along these directions is somewhat smaller than the one of α-silicon nitride single crystal reported previously. Slip deformations take place in narrow bands, thickness of which are very thin. For the {1010} ‹0001› case, itis almost equal to the distance between the nearest neighbor atoms and for the {1010} ‹1210› case about 0.4nm.
  • 齋藤 賢一
    2000 年 49 巻 3 号 p. 263-268
    発行日: 2000/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Coalescence process of copper nano-clusters is investigated by molecular dynamics simulation using inter-atomic interaction based on effective-medium theory. Stable atomic configuration at 0K is determined for several spherical clusters and icosahedral structure composed of 13, 55, or 147 atoms is obtained. Excess energy of clusters averaged over approximated surface area is larger than that of a flat surface. Compressive stress and high atomic energy exist near center in small clusters. By interaction simulation between two equivalent clusters, in which they approach each other with some offset distance or some initial rotation motion and coalesce, it is found that rotation motion of the whole body is generated as a consequence and that rotational kinetic energy obtained after coalescence is affected by size of the original cluster and initial offset distance. Transition from translational kinetic energy to rotational kinetic energycompletes in less than 1 picosecond. In clusters system composed of 1366 atoms, it is shown, by the analysis of coordination number or atomic configurations and trajectories, that compressive deformation in coalescence process becomes smaller with increasing initial offset distance. In the system with small number of atoms, lattice vibration is large and it is supposed that rearrangement of atomic structure is relatively easy.
  • 小竹 茂夫, 鈴木 泰之, 妹尾 允史
    2000 年 49 巻 3 号 p. 269-274
    発行日: 2000/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    The probability density of stress on valence electron, called electron stress σ, is studied at slip planes of simple metals, K and Al, under uniaxial deformation. σ is calculated from the perturbed wave function by using pseudopotential method. Distributional change on σ indicates the properties of plastic deformation like the critical shear stress in bcc and fcc metals. The direction between the local minimum density of σ and an atom is agreeable with the slip direction of bcc and fcc metals. We also examine the force between ion and electron from virial force by concerning the electron screening effects on ions. Although the present calculations are the analysis on the perfect crystal, distributional change of σ can imply the phenomena on plastic deformation in simple metals.
  • 中谷 敬子, 中谷 彰宏, 北川 浩, 杉山 吉彦
    2000 年 49 巻 3 号 p. 275-281
    発行日: 2000/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Fractures in amorphous metal usually occur in a brittle manner. The metal is, however, essentially a ductile material, for it demonstrates high deformability, despite having a high yield strength. These two facts seem to conflict with each other at first glance. In this paper an atomistic simulation is carried out to resolve this apparent contradiction. The molecular dynamics (MD) method is applied to a cracked amorphous structure containing 102356 atoms with mode I loading. Crack growth begins at the time when a stress wave arrives at the crack tip. The amount of crack extension increases with increase in the crack-tip opening displacement, and potential energy is changed to kinetic energy with the crack growth. From an investigation of the atomic arrangement and structure of the defect atoms (which is defined by a local density), it is demonstrated that crack growth occurs with atomic deformation that takes place in a ductile manner in a local area, but in a brittle manner in a macroscopic view. Moreover, it is shown that the interaction between the crack and the void, which develops in front of the crack tip, plays some important roles during crack growth.
  • 鈴木 啓史, 大久保 忠恒
    2000 年 49 巻 3 号 p. 282-289
    発行日: 2000/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    The embedding atom method (EAM) or the Finnis-Sinclair potentials of Zr and Ti by Pasianot, Oh, and Ackland are compared, and are used to simulate wide range of static and defect properties under the same conditions. The EAM potential for Zr based on Pasianot is determined by the authors with careful selection of experimental data necessary to define parameters in the potential. Selected potentials show similar static properties like lattice constants, cohesive energy, or elastic constants. However, more complicated properties that include interstitial formation energy and interstitial formation volume are not comparable, especially low in potentials that take account of the effect of internal strain. The reason for this tendency is attributed to the difference of deformation field around an interstitial.
  • 皆木 卓士, 塩野 剛司, 西田 俊彦
    2000 年 49 巻 3 号 p. 291-295
    発行日: 2000/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Forsterite (Mg2SiO4) precursor was synthesized from a heterogeneous alkoxide solution containing MgO powder with mean particle size of 100nm. In order to improve the chemical characteristics of the precursor, a wet condition was adopted for milling. Effects of milling parameters and solvent on chemical characteristics of the precursor were studied. The mixture of ethanol and deionized water was used as a solvent. The water content was varied from 0vol% to 100vol%. The characteristics of the obtained precursors were evaluated by X-ray diffraction (XRD) method, differential thermal analysis (DTA), scanning electron microscope (SEM) and Fourier transform infrared (FT-IR) spectroscopy. Milling in water was effective to lower the crystallization temperature of the precursor to forsterite. However, the milled precursor strongly aggregated. Calcined powder was locally sintered and a dense polycrystal could not be obtained. On the other hand, milling in a solvent containing ethanol modified the surface of the precursor with ethoxy group and, due to absorption of ethanol, this resulted in an effective relaxation of the aggregates and in easy handling of the powder. The solvent with 75vol% water was the most effective among others for preparing monolithic forsterite powder which exhibits a good sinterability
  • 高 三徳, 中佐 啓治郎, 加藤 昌彦
    2000 年 49 巻 3 号 p. 296-303
    発行日: 2000/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    In order to characterize the cracking patterns observed in thermally-sprayed WC-Co cermet and Al2O3-TiO2 ceramic coatings under nonuniform two-dimensional stress, the hydraulic bulge test of a coated disk specimen with a hole and the punch press test of a disk specimen without a hole were conducted. The observed cracking patterns on the coatings changed in the radial direction depending on the relative strength of coating to interface and the stress distribution. The appearance of the cracking patterns was explained well by “FEM Analysis-Strain Combination Method” which accommodates the strain of substrate with coating from elastic-plastic analysis and the strain of substrate from finite element method. Moreover, the calculated sizes of cracks agreed well with those measured in experiments.
  • 坂井田 喜久, 田中 啓介
    2000 年 49 巻 3 号 p. 304-309
    発行日: 2000/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    A new low-capacity fatigue testing machine was developed to evaluate the cyclic fatigue behavior of porous ceramics used for dust filters. Cyclic fatigue tests were conducted by cyclic four-point bending with the stress ratio 0.5 at a room temperature. The results were summarized as follows:
    (1) The distribution of cyclic fatigue life at a given stress level can be expressed as a two-parameters Weibull distribution. From the Weibull distribution of the life, the exponent of the crack propagation equation as a function of the stress intensity factor was estimated to be 25.3.
    (2) The fatigue life decreased with increasing maximum stress. The relation between the maximum stress, σmax, and the fatigue life, N, was expressed as σmaxnN=const. The exponent of the crack propagation equation determined from the S-N relation was 20.3 which was close to the value determined of the life distribution.
    (3) Cyclic loading induced a residual bending deformation in the specimen. The amount of residual deformation increased with increasing number of stress cycles.
  • 伊藤 義康, 安藤 秀泰, 新藤 尊彦
    2000 年 49 巻 3 号 p. 310-315
    発行日: 2000/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    A thermal spraying process is useful to be able to coat on substrates without any thermal damages. Therefore, it is possible to coat the high melting-point material such as steels, on the low melting-point material such as aluminum. However, it is generally inevitable to develope residual stress due to difference in thermal expansion and temperature between coating and substrate. Therefore, the strength of thermal sprayed coatings is affected by the residual stress in the coating layer.
    In this study, the strength behavior of thermal sprayed aluminum with carbon steel and 13% chromium stainless steel was made clear by four-point bending test. The results revealed that the strength of 13% chromium stainless steel sprayed specimen showed high value in comparison with the carbon steel sprayed specimen using X-ray diffraction method. The compressive residual stress could be measured in 13% chromium stainless steel coatings. On the other hand, the tensile residual stress could be measured in carbon steel coatings. It was confirmed that the good agreement could observed between the residual stress characteristics and the bending strength of coated specimen.
  • 鈴木 惠, 木田 外明, 相川 和人, 田城 宏幸
    2000 年 49 巻 3 号 p. 316-321
    発行日: 2000/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    The fracture mechanisms and the damage rate of fatigue-damaged FRPA specimens are estimated by analyzing the AE signals detected during the tensile test. The loads Pi, Pb and Pc in change of the damage machanisms are determined by applying the AE energy gradient method to the nondamaged and the damaged specimens. It is found by AE frequency analysis at the loads that the damage mechanisms for nondamaged specimen are dominated by the fiber breaking, but the damage mechanisms at the lower ratio of N/Nf for the damaged specimens are dominated by the fiber debonding, the damaged mechanisms at the higher ratio of N/Nf are dominated by the fiber beraking and the damage modes at more higher ratio of N/Nf are changed by stress amplitude, where N is the number of cycles and Nf is the number of cycles to failure. It is also found by the relation between the ratio of load P/P(N) and the ratio of number of cycles N/Nf that the damage rate 1-Pi/Pi(N) is estimated higher than the damage rates 1-Pb/Pb(N) and 1-Pmax/Pmax(N), where P and P(N) are the loads in change of damage machanisms of the damaged and the nondamaged specimens, respectively.
  • 高橋 浩之, 宇野 哲老, 田中 弘一
    2000 年 49 巻 3 号 p. 322-326
    発行日: 2000/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Low carbon-medium nitrogen 316 stainless steel (316FR) with improved creep strength was developed for structural material for the demonstration fast breeder reactor (FBR). Fatigue, creep-fatigue and creep crack propagation tests have been conducted using CT specimens of 316FR welded joints at 650°C in order to investigate the applicability of crack propagation evaluation methods to welded joints. The results obtained are as follows. The fatigue J-integral range of welded joints could be estimated using material data of the base metal by the simplified J-integral estimation methods, the reference stress method and the GE/EPRI method, when the crack opening ratio were considered. Heating time (testing time) made a difference in creep-fatigue and creep crack propagation rates estimated by the creep J-integral range. It was considered that the degradation of microstructure (from delta ferrite into sigmaphase) by high temperature aging, which reduced ductility, affected the crack propagation behavior.
  • 菊川 久夫, 康井 義明, 戸松 泰介
    2000 年 49 巻 3 号 p. 327-333
    発行日: 2000/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    In order to examine the effect of strain rate on critical stress intensity factors of bones, fracture toughness tests were performed using compact tension specimens prepared from bovine bones under the strain rate ranging from the quasi-static to the high-speed. To confirm anisotropic properties, two different specimens were used, that is, one is the L-direction specimen with initial fissures in the bone running parallel to the axis, and the other is the T-direction specimen with fissures running perpendicular. Further, the specimens under wet and dry states were tested to ascertain the effect of humoral components contained in the bones on critical stress intensity factors. In reference to directional dependence of fissure development, anisotropic properties were observed. Stress intensity factors of the T-direction specimen are two to three times higher than that of the L-direction specimen under the quasi-static range. In the case of wet specimens, directional dependence, however, was not so clearly observed under the high-speed-strain rate compared with the case of the quasi-static range. The physiological state of bone is close to wet specimen compared with dry specimen, and wet specimens possessed a reinforcing mechanism two to three higher in terms of critical stress intensity factor. It was confirmed that the fracture toughness of bone was deteriorated in the vicinity of the strain rate from 100 to 101s-1 regardless of the humoral condition of the specimens. It is speculated that a drastic change of fracture toughness at each strain rate is caused by microfractures due to potential defects at the origin before the main fracture develops.
  • 荒井 正行, 岩田 宇一
    2000 年 49 巻 3 号 p. 334-339
    発行日: 2000/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    In this study, effect of temperature and Cu contents on Al2O3/Cu composite materials was examined experimentally. Obtained results are sumarized as follow.
    (1) Microstructure of Al2O3/Cu composite meterial is changed between 50[%] and 75[%] Cu content. That is, amatrix in Al2O3/Cu composite materials with 25[%] and 50[%] Cu content is Al2O3. On the other hand, a matrix in 75[%] Cu content is Cu. (2) Density of the composite materials increases monotonosly with Cu content. Vicker's hardness decreases with Cu content. (3) Coefficient of linear thermal expansion increases with Cu content. (4) Young's modulus decreases with Cu content. (5) Bending strength has strong effect of both of temperature and Cu content.
  • 大島 昭彦, 高田 直俊
    2000 年 49 巻 3 号 p. 340-343
    発行日: 2000/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    A series of centrifuge model test of “Compacted Bulb Foundation Method” was carried out to investigate the effect of tamping conditions, such as ram mass, ram base area and number of blows, and foundation base area on characteristics of its bearing capacity. Main conclusions are as follows: 1) ultimate bearing capacity and coefficient of subgrade reaction of compacted bulb was hundred times or more and ten times larger than untamped ground, respectively, 2) its bearing capacity was dependent on the ram mass per unit base area, 3) compacted bulb tamped by a ram having larger base area relative to loading area had lager bearing capacity.
  • 中村 一平, 上松 英司, 河本 文良, 辻野 博史, 後藤 年芳, 鈴木 教泰
    2000 年 49 巻 3 号 p. 344-347
    発行日: 2000/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    River sludge was solidified with geo-cement for utilization and clarification of the river area. During excavation work of treated sludge, odor control was required. To select the odor control method, laboratory and site investigations were performed. A spray method using ferrous chloride aqueous solution during excavation and on the surface of treated sludge was selected and was found to be effective.
  • 澤 孝平, 友久 誠司, 稲積 真哉, 橘 真理
    2000 年 49 巻 3 号 p. 348-351
    発行日: 2000/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Recently, the amount of muddy soil produced from various kinds of construction sites has been increasing. Most of the soils are difficult to reuse as construction material owing to low strength, and the disposal site of the soil has been decreasing. Therefore, it is very important to reuse the soil from the view point of natural resource preservation and environmental impact mitigation.
    The purpose of this study is to reuse the muddy soil effectively stabilized with cement, and to clarify the possibility of application of coal fly ashes as hardening additives to the soil stabilization. In this study, the hardening effects of four coal fly ashes are examined by an unconfined compression test, and the hardening reaction products of stabilized soil were measured by SEM observation and X-ray diffraction analysis.
    As a result, it has been found that coal fly ashes, especially fluidized bed combustion coal fly ash, are effective on the muddy soil stabilization as a hardening additive. The quality control of coal fly ash is very important, because the hardening activity of the coal fly ash changes due to the storage condition. Furthermore, the main reaction products which contribute to strength development are ettringite and calcium silicate hydrate compound.
  • 山崎 浩之, 中里 高密
    2000 年 49 巻 3 号 p. 352-355
    発行日: 2000/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    A new type of measures against liquefaction is developed, which densifies ground by installing soil piles with static compaction. The by-product from construction, which is added with a small amount of cement for stabilization, is used for the soil piles. This paper describes field experiment results of, 1) the effectiveness of thenew method on the densification of ground, 2) moduli of deformation of the improvedground, and 3) the lateral displacements of the surrounding soil. Ths main findings are:
    1) Ths effectiveness of the new method on the densification was validated with the Standard Penetration Test (SPT).
    The increments of the SPT-N value between piles were the almost same with those of SCP method which dynamically compacted ground. The increments were, however, larger inside of piles then those of SPT.
    2) The moduli of deformation of the ground were increased and the densification by the static compaction was confirmed.
    3) The maximum lateral displacement of 55mm of the surrounding soil was measured at 6m depth near the pile.
  • 栄 中, 村上 敬宜
    2000 年 49 巻 3 号 p. 356-361
    発行日: 2000/03/15
    公開日: 2009/06/03
    ジャーナル フリー
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