材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
51 巻 , 2 号
選択された号の論文の19件中1~19を表示しています
  • 市川 康明
    2002 年 51 巻 2 号 p. 130-134
    発行日: 2002/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    The double porosity theory was first given by Bareblatt, Zheltov and Kochina1), which considers the effect of fissures and matrix porosity in the rock-mass seepage problem, and they introduced an assumption that the mass flow between the two porosity systems is detrmined by the pressure gap of the two systems. It was extended to deformable porous media (i.e., consolidation theory)2-5. These conventional double porosity theory is based on a local-averaged mixture theory.
    The modern homogenization theory6), 7) was developed for the materials with periodic micro-structures. Starting with Navier-Stokes and mass-conservation equations and applying the homogenization procedure to a porous media flow yield Darcy's law and the seepage equation6). It is important that the flow field in porous media is determined on a balance of the pressure field and the velocity field, and that we can identify the local pressure/velocity field by the homogenization theory.
    We here present a new double porosity theory applying on a multiscale homogenization analysis method8) for porous materials with two-scale porosity systems.
  • 小林 昭一, 吉川 太
    2002 年 51 巻 2 号 p. 135-139
    発行日: 2002/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    The present paper describes a new technique for estimating initial stresses in rock mass by measuring phase velocity of ultrasonic (elastic) waves in a specimen shaped from the bored core. The technique is supported by the following facts observed in the tests carried out for andesite, basalt, granite and sandstone specimens.
    1) Phase velocities of both longitudinal and shear waves traveling in the perpendicular direction to the loading axis in the uniaxial compression test change considerably at the pre-experienced maximum stress.
    2) The pre-experienced maximum stress is remembered at least one week.
    3) The phase velocity of shear wave polarized in the perpendicular to the loading direction is not affected by the pre-existed stresses in other directions.
  • 渡辺 英彦
    2002 年 51 巻 2 号 p. 140-145
    発行日: 2002/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    In order to clarify the influence of confining pressure on the Kaiser effect in post-failure region, acoustic emission (AE) experiments were performed under triaxial loading conditions using Oya-tuff. Triaxial compressive pre-loading was performed until post-failure region, and then re-loading test was performed under different confining pressure. The rapidly increasing point of cumulative AE event count was determined as the peak point of AE event count rate increment. The estimated stress was compared with pre-stress. The main results are summarized as follows. (1) In the case of the re-loading test performed under the same confining condition, the remarkable AE increase appeared at the differential stress level at the previous residual strength. (2) In the case of the re-loading test under the lower re-confining pressure than the pre-loading test, the estimated stress is smaller than differential stress at previous residual strength. (3) In the case of the re-loading test under higher confining pressure, the estimated stress was equivalent to the differential stress at the previous stress peak.
  • 楠見 晴重, 白神 敦, 片江 敏雄
    2002 年 51 巻 2 号 p. 146-151
    発行日: 2002/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    The surface of cutting rock slope has exposed to alternate dry and wet conditions for a long time, and they are weathered. We developed direct shear testing apparatus that can expose soft rock specimen to alternate dry and wet conditions under constant shear and normal stress, and are investigated about relationship between deformation properties and the shear behavior of soft rock under dry and wet conditions.
  • 松岡 俊文, 深森 広英, 芦田 讓
    2002 年 51 巻 2 号 p. 152-156
    発行日: 2002/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    We investigate an inverse problem for mapping the hydraulic fracture geometry using surface tilt data. It is well known that this problem becomes a non-linear inverse problem. If the inversion algorithm can be separated into two stages as: (1) the identification of the fracture plane and (2) the estimation of the fracture aperture distribution, then the computation scheme becomes robust and stable. We call this methodology as a cascade inversion scheme for tilt data.
    At the first stage of the inversion, the fracture plane is estimated by the Nelder-Mead simplex method and we can determine the fracture plane. And then the fracture aperture distribution is determined by the successive linear inversion stage. In the second stage, the fracture plane is divided into the small rectangular peaces and each peace has the different fracture aperture. The normal equation, where the fracture apertures are unknowns, can be solved by the least squared methods with two constraints as the smoothness and non-negative values of the fracture apertures. The proposed methodology was applied to the synthetic and field data. The inversion results are quite acceptable and we conclude this cascade inversion scheme is a robust method and easy to handle the field data.
  • 拡張カルマンフィルタによる解析法の現地計測結果への適用
    大友 譲, 國井 仁彦, 谷本 親伯
    2002 年 51 巻 2 号 p. 157-161
    発行日: 2002/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    The electorical resistivity prospecting is a useful method to detect the distribution of discontinuities in rock mass.
    Authors firstly verify the algorithm of inversion analysis method, which developed for 3D-FEM. to identify resistivity values through an extended Kalman filter by case studies of 3-D FEM numerical simulation. Secondly based on the results of this simulation, an application of new method to the jointed rock mass survey is done.
    It is concluded that the inversion technique, which we have established through an extended Kalman filter, works effectively.
  • 久武 勝保
    2002 年 51 巻 2 号 p. 162-167
    発行日: 2002/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    In order to make clear reasonable executive conditions of steel fiber reinforced high strength shotcrete (SFRS) constructed in an elastic or a time dependent soft rock tunnel with large scale, a numerical analysis has been conducted, by taking the velocity of tunnel face progress, the elasto-plastic behavior of steel supports and the time dependency of strength of SFRS into account. It has been recognized that SFRS is a reasonable primary lining for several types of ground conditions, especially for the squeezing ground with time dependency. High strength at early stage of its execution and the toughness after its yielding contribute to the safety construction of a large scaled tunnel.
  • 鎌田 浩毅, 須田 恵理子, 齋藤 武士, 飯澤 功, 酒井 敏
    2002 年 51 巻 2 号 p. 168-175
    発行日: 2002/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    Volcanic debris avalanche is a large-scale landslide which occurs at unstable volcanic edifice and often creates horseshoe-shaped crater at its source with hummocky deposits of volcanic debris including large blocks inside. Dynamic pressure model has recently been proposed to explain flow behavior of volcanic debris avalanches: Kinetic friction of debris avalanche decreases systematically at threshold of a certain critical speed for flotation. We have done a sliding experiment using flour powder as debris avalanche matrix and metal disks that slide on a powder layer as incorporated large blocks. Sliding traces left on a powder layer showed that a disk was floating over a certain critical speed. Kinetic friction coefficients, calculated by the position of a sliding disk recorded on a digital video, become small at a higher speed which exceeds critical floating speed, and provide smaller coefficient than those of normal surface of a rigid body. The critical floating speed deduced from dynamic pressure model is consistent with our experiment. In order to verify this model as the major driving force to float megablocks incorporated commonly in a volcanic debris avalanche, critical floating speeds for two geological cases at the collapses of 1980 Mount St. Helens and 1984 Ontake, central Japan, are examined and compared with the observed flow velocities. Estimated velocities deduced from the dynamic pressure model correspond fairly well to the actual velocities. This strongly suggests that the model gives the most convincing explanation for transportation and deposition mechanism of volcanic debris avalanche.
  • 石場 隆司, 飛田 守孝, 榊原 精
    2002 年 51 巻 2 号 p. 177-181
    発行日: 2002/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    Molecular dynamics simulation of nickel single nanocrystal composed of 1550 atoms in the uniaxial tensile and compressive deformation was performed using three kinds of potentials (Morse, Finnis-Sinclair and EAM potential) to investigate the effect of potential on the deformation mode. The effect of potential was observed under tensile loading; phase transformation (fcc→hcp) occurred above the elastic limit of elongation in the case of Morse and Finnis-Sinclair potential, and (111) [101] slip was observed in the case of EAM potential. Similar development of twin deformation, (111) [112], was observed in all the cases under compressive loading.
  • 伊藤 明洋, 杉田 雄二, 桜井 茂雄, 亀田 純
    2002 年 51 巻 2 号 p. 182-187
    発行日: 2002/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    The degradation of coatings and substrates would be a great influence on the integrity of gas turbine blades for electric power generation. This paper describes the effect of thermal aging at 870°C and 920°C for 8000h in air on the microstructure and chemical composition in aluminized CoCrAlY coatings and directionally-solidified Ni-base superalloy substrates of advanced gas turbine blades. The unaged and thermally aged coatings consisted of four layers with different microstructure and chemical composition. Thermal aging led to a little oxidation, nitridation and decrease in the Al content in near-surface regions. In the adjacent region, coarse Cr rich precipitates formed during the thermal aging. During the thermal aging, Ni diffused extensively from the substrates into near-surface regions. The interdiffusion of Ni/Co resulted in the formation of Al/Ni rich intermetallic phases in various coating regions. The thermal aging formed the coating/substrate interdiffusion zone, which comprised Al/Ni rich elongated precipitates.
  • 黒田 敏雄, 池内 建二, 北川 良彦
    2002 年 51 巻 2 号 p. 188-194
    発行日: 2002/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    The algorism of the reconstruction of three-dimensional topography from stereoscopic SEM fractographs has been developed. This is an area-based multi-step stereo matching algorithm in order to achieve high accuracy, that is, the corresponding points in stereo photography were searched using a large window area and search area without occurrence of mismatching for the first step. For the next step, the sizes of widow area and search area were set smaller than those of the first step around the first corresponding point and then the second corresponding point is determined. This procedure is repeated up to fourth step.
    DEMs (Digital Elevation Model) of the fracture surfaces of ferritic-austenitic duplex stainless steels were reconstructed using the developed algorithm. The DEMs showed slanted surfaces, and direct comparison of the cross sectional topography between the reconstructed DEMs and the real surface was performed. The reconstructed DEM revealed exactly the shape of the dimple patterns and detailed features on the fracture surface.
  • 大谷 俊博, 荻 博次, 平尾 雅彦
    2002 年 51 巻 2 号 p. 195-201
    発行日: 2002/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    We studied microstructure evolution caused by creep in 2.25%Cr-1%Mo steel using ultrasonic attenuation. The material was exposed to the temperature of 923K at various stresses. We used electromagnetic acoustic resonance (EMAR) to measure attenuation. EMAR is a contactless acoustic-resonance method and free from energy losses associated with contact transducer, resulting in the intrinsic attenuation in solids. We used axial-shear-wave EMAT, which transmits and receives SH wave propagating in the circumferential direction of a cylindrical specimen. The attenuation coefficient was obtained from the ringdown curve at the resonance by interrupting the creeping. The attenuation exhibits much larger sensitivity to the damage accumulation than the velocity. Approaching the rapture, the attenuation coefficient becomes five times as large as the initial state. We correlate this attenuation evolution with the microstructure change, especially, the changes in dislocation structure that most contributes to the attenuation change. This is supported by TEM observations. The technique has a potential to assess the damage advance and predict the creep life of metals.
  • アラミド繊維強化基板の穴あけ加工時の壁面温度と損傷
    廣垣 俊樹, 青山 栄一, 片山 傳生, 前田 伸治, 近藤 久弥, 井上 久弘
    2002 年 51 巻 2 号 p. 202-206
    発行日: 2002/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    This paper describes the relationship between the temperature and the damage at the hole wall of AFRP (Aramid fiber reinforced plastic) for printed wiring boards (PWB) in laser drilling. First, the temperature is measured by a thermocouple at various positions on the drilled hole wall in laser drilling. Second, we researched the heat affected damage at the hole wall by an optical microscope after drilling. Comparing these results, we clarified the temperature in the hole wall where the heat affected damage occurred. Finally, the thermal transfer model paying attention to the thermal properties of aramid fiber is proposed to predict the heat affected width of the hole wall after laser drilling. It is confirmed that the calculated results by an axisymmetric model were in good agreement with the experimental ones.
  • 斎藤 篤, 嚴 翼鎮, 高橋 博正
    2002 年 51 巻 2 号 p. 207-214
    発行日: 2002/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    The friction and wear properties of filled polyacetal (POM)/polyethylene (PE) blends have been studied. The fillers used were amino silane coupling agent treated and untreated bronze powder. And low density polyethylene (LDPE), high density polyethylene (HDPE) and high molecular weight high density polyethylene (HMWHDPE) were used as blended polymers in POM. A thrust washer type testing apparatus, in which the end surface of the tubular specimen is rubbed with a slider (S45C) under unlubricated conditions, was employed for the friction and wear tests. Frictional surfaces were observed using an optical microscope and an electron probe X-ray microanalyzer to examine the role of filler and blended polymers in the friction and wear of filled polymer blends. The wear rates of bronze powder filled POM/PE (LDPE, HDPE, HMWHDPE) blends were smaller than those of POM/PE (LDPE, HDPE, HMWHDPE) blends and bronze powder filled POM. The synergistic effect of bronze powder and PE particle of blended polymers decreased the wear rate of bronze powder filled POM/PE. The coefficients of friction of bronze powder filled and unfilled POM/PE (LDPE, HDPE) were smaller than that of POM. The effect of the surface treatment of the bronze powder treated with amino silane coupling agent improved for the coefficient of friction and wear rate of bronze powder filled POM and POM/PE (LDPE, HMWHDPE) blends. It was suggested that bronze powder and the PE particle of blended polymers in POM mainly bore the load applied to the frictional surface (namely load bearing action) and contributed to enhance the friction and wear properties.
  • 藤井 秀幸, 松永 久生, 村上 敬宜
    2002 年 51 巻 2 号 p. 215-220
    発行日: 2002/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    To study the influence of δ ferrite on the fatigue mechanism of SUS630 stainless steel, rotating-bending fatigue tests were carried out in air at room temperature. The observation of the fatigue process at specimen surface by plastic replica method clarified that the crack initiation sites are soft δ ferrite grains and the size of δ ferrite is a crucial influencing factor for the fatigue strength. At the stress of the fatigue limit, many cracks initiated from the slip bands in δ ferrites, grew into the martensitic matrix and stopped. The aspect ratio b/a of the crack that was initiated from slip band in a δ ferrite was b/a≅0.5. If δ ferrites are considered equivalent to defects, the fatigue limit can be estimated accurately by the √area parameter model.
    To estimate the lower limit of the fatigue limit, the maximum width of δ ferrite was predicted by statistics of extremes. In fact, fatigue crack did not always initiate in maximum δ ferrite grain because crack initiation is strongly influenced by the crystallographic orientations. However, from the viewpoint of the quality control of large number of machine parts, statistics of extremes is useful to estimate the lower limit of the fatigue limit.
  • 磯部 展宏, 桜井 茂雄
    2002 年 51 巻 2 号 p. 221-226
    発行日: 2002/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    Tensile-torsional-combined biaxial low-cycle fatigue tests on welded tubular specimens of the Ni-base superalloy Hastelloy-X were carried out and the micro-crack growth behavior in the weldments was investigated with the aim of improving life assessment methods for high-temperature components. Welded hollow cylindrical specimens of two types were prepared, one welded in the axial direction and the other welded in the circumferential direction. Straincontrolled low-cycle fatigue tests were carried out at 700°C. Fatigue lives of the welded specimens were about one-half that of the base metal specimens and the corresponding fatigue strength reduction factor was about 1.4. Microcracks also observed by using a replication technique during occasional interruptions of the tests. In both weld and base metal, the initiation of micro-cracks was observed in the early stage of life, but the initiated lengths of the microcracks in the weld metal was about 0.5mm while the equivalent figure for base metal was about 0.1mm. The Grain boundary oxidation would strongly affect these crack initiations. The crack growth life from 0.5mm to failure in the base metal specimen almost coincided with the failure life in the welded specimen. Therefore, the reduction of the fatigue life of welded specimen is because the initiated lengths of micro-cracks in the weldment are greater the lengths in the base metal. The maximum principal strain was confirmed as a good parameter for the evaluation of crack growth rates for both weldments and base metal. This result shows that the fatigue strength reduction is not due to the strain concentration at the weld. The initiated lengths of micro-cracks affect the fatigue life of weldments of Hastelloy-X.
  • 竹田 英俊, 中島 美樹子, 庄子 哲雄
    2002 年 51 巻 2 号 p. 227-232
    発行日: 2002/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    As an alternative to the conventional Izod method, we investigated a new impact-resistance test method employing a high speed tensile tester and stress-concentrated specimens. We proposed a more practical method of impact resistance evaluation based on the combined use of a high speed tensile tester and stress-concentrated specimens. We clarified that this method has the following excellent features: 1) The method allows a tensile rate and notch radius to be selected for the specimen in accordance with the product's usage conditions. In addition, quantitative evaluation of the effects of these specimen-related factors on the impact-resistance performance of the final products can be conducted. 2) The method enables the creation of injection-molded specimen surfaces more like those of actual final products than previous methods. 3) This makes it possible to obtain not just energy values, but trends of stress and displacement behavior, enabling identification of the contribution of each behavior to effective energy development. 4) The low variation in measured values enables evaluations to be conducted using a small amount of specimen material and assures the high reliability of the resulting data.
    When this evaluation method was used to assess the impact-resistance performance of talc-reinforced polypropylene copolymer, the following facts were elucidated: 1) The material's impact resistance is less dependent on the specimen's notch radius, as reflected in the relatively small loss of impact resistance even with a significantly reduced notch radius. This gives the developed copolymer great utility for use in automotive components, which have many areas of stress concentration. 2) The developed material features greater impact resistance and rigidity than conventional materials, indicating the possibility of a superior balance between impact resistance and rigidity in future formulations.
  • 竹田 英俊, 中島 美樹子, 庄子 哲雄
    2002 年 51 巻 2 号 p. 233-238
    発行日: 2002/02/15
    公開日: 2009/06/03
    ジャーナル フリー
    Creep tests were conducted using talc-reinforced Polypropylene copolymers. Then, tensile tests were conducted using the creeped samples to reveal the effect of creep damage on the impact energy-absorption. The creep damage progression mechanism was investigated due to fracture surface observation, density measurement and local elastic property. The following conclusions have been drawn from the experimental results: 1) From the density variation of damaged samples, we clarified that creep damage occurs due to an accumulation of voids in the material. 2) The residual impact resistance does not decrease significantly until a lifetime ratio becomes 0.7, and apparently increases at certain notch radius values. At a lifetime ratio of 0.9, we identified a significant decrease in residual impact resistance due to void accumulation, as reflected in the measured density data. 3) The fractured surfaces of samples after high speed tensile tests were slightly whitened, but they were otherwise very similar to those of undamaged specimens. We found that this phenomenon coincides with the phenomenon in which the retained impact resistance did not significantly decrease. 4) The local elastic property measurement revealed that the vicinity of notch bottom was hardened due to strong molecular chain orientation, in turn contributing to the retention and improvement of the residual impact resistance. 5) The creep damage involves two causative factors: hardening from the strong molecular chain orientation, and softening of the material due to void accumulation. We also clarified that these factors affected the residual impact resistance.
  • 3. 新幹線車両の構体
    公江 茂樹, 大西 登喜夫
    2002 年 51 巻 2 号 p. 239-244
    発行日: 2002/02/15
    公開日: 2009/06/03
    ジャーナル フリー
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