材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
40 巻 , 452 号
選択された号の論文の21件中1~21を表示しています
  • 松宮 徹
    1991 年 40 巻 452 号 p. 509-518
    発行日: 1991/05/15
    公開日: 2009/06/03
    ジャーナル フリー
  • 水野 衛, 村上 澄男, 橋本 貴全
    1991 年 40 巻 452 号 p. 519-525
    発行日: 1991/05/15
    公開日: 2009/06/03
    ジャーナル フリー
    Simplified analysis of creep crack growth under neutron irradiation was performed by using Double Cantilever Shear Beam (DCB) model in order to discuss the effect of neutron irradiation on the integrity of nuclear structure components. The model was assumed to consist of a creep damage zone of a strip of finite width including the plane of crack and a shear dominant elastic zone outside the creep damage zone. It was further assumed that the creep damage zone is in the state of uniaxial stress, and the creep crack growth was described in the framework of the Continuum Damage Mechanics. Then, by incorporating the constitutive equations of irradiation creep proposed by the present authors, the steady creep crack growth under un-irradiated, post-irradiation and under-irradiation conditions were analyzed. The effects of neutron irradiation and material non-linearity on creep crack velocity, the distribution of stress, strain and damage parameter in front of the crack tip were elucidated.
  • 中西 秀明, 阿部 武治, 納所 孝至
    1991 年 40 巻 452 号 p. 526-532
    発行日: 1991/05/15
    公開日: 2009/06/03
    ジャーナル フリー
    Uniaxial tension tests were carried out using Nylon 6 which is a typical thermoplastic resin. The surface roughening during plastic deformation was investigated with a stylus instrument and the change in the microscopic surface profile was observed by a scanning electron microscope. The surface roughness increased in proportion to the applied plastic strain until the beginning of the necking of the specimen. After that the rate of increase of the surface roughness with increasing strain gradually slowed down. It was found that the degree of crystallinity was an important factor for the surface roughening during plastic deformation. The initial surface roughness of specimen also affected the surface roughness. The specimen thickness from 2mm to 6mm had little effect on surface roughening. The surface roughness in the loading direction was smaller and had larger wavelength than that in the transverse direction. Macro-fibrils, that is, fibrous structures were observed on the plastically deformed surface. The measured surface roughness was considered to consist of the irregularity between neighbouring macro-fibrils and the irregularity caused by the motion of group of macro-fibrils.
  • 伊藤 和幸, 伊藤 哲
    1991 年 40 巻 452 号 p. 533-539
    発行日: 1991/05/15
    公開日: 2009/06/03
    ジャーナル フリー
    It is desirable to design a structure and its members with a reasonable reliability. Here, a reduction factor for obtaining the design strength of a reinforced concrete member subjected to shear and flexture with a required reliability is proposed for the JSCE Code by using the probabilistic method of estimating the reliability, considering the variations in strengths of both reinforcing bars and concrete, because the reliability of the strength provided in the JSCE Code has been found to be considerably higher than that specified in all cases. The validity of the factor is examined by comparing the obtained reliability with that of the strength provided in the ACI Code which was determined on the safer side, based on a large number of test data.
  • 田中 拓, 田中 啓介, 秋庭 義明, 北條 正樹
    1991 年 40 巻 452 号 p. 540-546
    発行日: 1991/05/15
    公開日: 2009/06/03
    ジャーナル フリー
    Tensile failure of unidirectional carbon/epoxy laminate, Toray T300/#2500, was studied using the center-notched specimens having various notch sizes and fiber orientations relative to the loading axis. The failure features of the notched unidirectional laminates can be classified into two types. For the case of the 0° specimens (the fiber orientation was parallel to the loading axis), gitudinal split grew along fibers in a stable manner. The fracture surface of these specimens was characterized by many hackles and fiber/matrix interfacial debonding. On the other hand, the specimens with fiber orientations between 30° and 90° fractured catastrophically at the maximum load. The fracture surface was covered with epoxy resin.
    A predictive method for the macrocrack initiation from notches was proposed from the modified average stress model combined with the maximum stress criterion. The average of the transverse normal stress (perpendicular to the fiber direction) over a characteristic length was critical for tensile failure, and that of the shear stress for shear failure. The predicted strength of the notched unidirectional laminates showed good agreement with the experimental results.
  • 芳我 攻, 秋山 浩司
    1991 年 40 巻 452 号 p. 547-553
    発行日: 1991/05/15
    公開日: 2009/06/03
    ジャーナル フリー
    In this paper, failure mechanisms and material assessing of thermoplastic matrix composite (glass cloth reinforced nylon-6, GFRN6) and thermoset matrix composite (glass cloth reinforced unsaturated polyester resin, GFRUP) were studied by using acoustic emission (AE) monitoring. GFRN6 was made under two different pressures of matrix impregnation. The effect of pressure on AE characteristics was also studied. The uniaxial tensile, unloading-reloading, loading-2 minutes holding and loading-30 minutes holding tests were carried out on those materials. During each test the load and AE parameters were recorded. Several AE parameters obtained during the uniaxial tensile tests indicated that the failure process of GFRUP consisted of (1) debonding between fiber and matrix, (2) matrix cracking, and (3) fiber breaking, while that of GFRN6 consisted of (1) debonding between fiber and matrix or the delamination of weft and warp and (2) fiber breaking. This means that no matrix cracking occurred in GFRN6. It became clear that the quality of impregnation of the thermoplastic matrix could be evaluated by the analyses of AE parameters. It was also shown that the Felicity ratio was a good indicator of the quality of impregnation. The ratio of the cumulative AE event counts over each holding interval to the total AE event counts during loading-holding testing was shown to be an indicator to evaluate the quality of adhesion between fiber and matrix. The AE events occuring during the load holding tests of GFRN6 and GFRUP were due to the debonding between fiber and matrix.
  • 矢口 昭弘, 西村 朝雄, 河合 末男
    1991 年 40 巻 452 号 p. 554-560
    発行日: 1991/05/15
    公開日: 2009/06/03
    ジャーナル フリー
    In plastic packaged integrated circuit (IC) devices, silicon chips are molded with epoxide resins in which silica particles occupy about 60 to 70% of the volume. Recently, the size of chips mounted in a package has increased rapidly with advances in large-scale integration technology. This trend creates a problem of increased mechanical stress in the package, which sometimes causes cracking in the encapsulation resin under temperature cycling and other conditions. Hence, evaluation of the fracture mechanics properties of these materials has become an important issue in package design.
    In this study, fracture toughness of highly silica particulate filled epoxide resins for IC encapsulation was studied using the double torsion (DT) test. The effects of loading condition and specimen geometry on the measurement results were studied to determine a proper test condition. The fracture toughness obtained agreed well with the results of the 3-point bending test. Measurements were also made on the materials with different volume fractions, shapes and size of particles to study the fracture properties of highly filled materials. The fracture toughness increased with increasing volume fraction and with irregularly-shaped particles.
  • 松田 憲昭, 中村 重義
    1991 年 40 巻 452 号 p. 561-567
    発行日: 1991/05/15
    公開日: 2009/06/03
    ジャーナル フリー
    A Frequency modified total strain energy parameter for evaluating failure and crack initiation lives for Ni and Co base superalloys under strain controlled fatigue-creep interaction conditions was proposed in the author's previous paper. The parameter, obtained from the total tensile strain energy and loading time under tensile stress, effectively explained surface crack propagation behavior.
    This paper examines the applicability of this parameter to predict the cyclic creep life and to evaluate the correlation between fatigue-creep interaction life and creep rupture strength. It was found that the strain controlled fatigue-creep interaction life, in addition to the cyclic creep life of René80 could be estimated by this parameter. Additionally, the creep rupture strength data were along the line of the best fit curve of strain controlled fatigue-creep interaction life data.
  • 石井 明, 越智 保雄, 佐々木 茂美, 中村 宏之
    1991 年 40 巻 452 号 p. 568-574
    発行日: 1991/05/15
    公開日: 2009/06/03
    ジャーナル フリー
    In order to clarify the cause for statistical scatter of the surface fatigue crack initiation lives and the growth lives in NiCrMoV cast steel, which is used as a large-size turbine rotor shaft, the initial crack growth behavior and the crack initiation sites have been investigated in detail. The rotating bending fatigue tests were carried out for four kinds of stress amplitude including the one just above the fatigue limit in room temperature and in air. The fatigue process was divided to several ranges by its crack length. By analyzing the distribution of the number of cycles required for cracks to propagate in each range, the corresponding crack length range which would strongly affect the scatter of the fatigue lives was examined. From the SEM observation of crack initiation sites, most of the cracks were found to initiate from inclusions, and their size, shape and depth were measured. The relationship between these values and the initiation lives were examined. Moreover, the crack length range which is sensitive to the microstructure was investigated by considering the correlation between the crack propagation rate and the stress intensity factor on the log-log relation.
  • 荻山 博之, 白石 哲郎, 佃 等, 曽山 義朗
    1991 年 40 巻 452 号 p. 575-580
    発行日: 1991/05/15
    公開日: 2009/06/03
    ジャーナル フリー
    Fatigue crack growth behaviors such as the crack growth rate and closure in the range of intermediate crack growth rate were studied using 2017-T3 Al alloy and SUS 304 steel under various combinations of the negative stress ratio, R and the maximum stress relative to the yield strength, σmaxy. The main results obtained are as follows;
    (1) The fatigue crack growth rate, da/dN increased with a decrease of R and an increase of σmaxy for both 2017-T3 Al alloy and SUS 304 steel. In this case, it becomes clear quantitatively that the compression stress in the load cycle relative to the yield strength, Scy is a very important factor which dominates the crack opening level and consequently da/dN in the both materials. The results are the same as those for S45C and SUS 329J1 which we reported previously.
    (2) Martensitic transformation taking place as the fatigue crack propagates complicates the effect of R on da/dN for SUS 304 steel, that is, the crack opening stress intensity factor relative to the maximum stress intensity factor, Kop/Kmax increased and consequently da/dN decelerated with Kmax particularly under the condition that σmaxy is small. These results are very different from those of other materials and it becomes clear that these fatigue crack growth behaviors correspond to the state of the formation of martensite at the vicinity of fatigue crack surfaces.
  • 荻山 博之, 佃 等, 曽山 義朗
    1991 年 40 巻 452 号 p. 581-587
    発行日: 1991/05/15
    公開日: 2009/06/03
    ジャーナル フリー
    The effect of ageing at 475°C on fatigue crack growth behavior was studied using (α+γ) twophase stainless steel with two different grain sizes, which is expected to be used widely in industrial fields.
    The main results obtained are as follows;
    (1) In the low ΔK range, the fatigue crack growth rate (da/dN) decreased with ageing at 475°C for the coarse grained specimens. This is caused by the enhancement of the roughness induced crack closure due to the change of the deformation mode in α phase with ageing. However, da/dN was not affected very much by ageing for the fine grained specimens.
    (2) In the low ΔK range, da/dN became to be fluctuated very much with ΔK by the ageing. This is closely related to the fact that the fatigue crack growth mechanism changes from slip plane fracture to that of cleavage in every α grain with ageing.
    (3) In the high ΔK range, da/dN increased with ageing particularly for the coarse grained specimens, since the cleavage fatigue crack growth mechanism becomes to be more dominant as ΔK increases.
  • 高橋 学, 武藤 睦治, 岡本 寛巳, 老川 恒夫
    1991 年 40 巻 452 号 p. 588-594
    発行日: 1991/05/15
    公開日: 2009/06/03
    ジャーナル フリー
    Fatigue crack growth tests of silicon nitride specimens with long cracks were carried out to investigate the effects of wave form of loading, stress ratio and frequency. The crack growth rate was independent of the wave form of loading and frequency. The effective stress intensity factor range afforded a unique crack growth curve regardless of stress ratio in the range of low growth rate. The fatigue crack growth rate in cyclic fatigue was higher than that in static fatigue.
    Fatigue tests of smooth specimens with small surface cracks induced by grinding were also carried out in the high frequency range. The S-N curve was predicted by using the both cyclic and static crack growth curves, where the initial surface crack size was defined on the basis of the strength of the specimen and the fracture toughness value. The S-N curve predicted using the cyclic crack growth curve was not in agreement with the experimental results. On the other hand, the predicted S-N curve using the static crack growth curve was in good agreement with the experimental results. Therefore, it is clear that a small crack tends to grow in a static fatigue manner even in the range of high frequency and low crack growth rate, where the cyclic crack growth is dominant for long cracks.
  • 江藤 元大, 船見 国男, 山本 恭永, 清水 秀治, 杉田 平次, 菊地 進
    1991 年 40 巻 452 号 p. 595-600
    発行日: 1991/05/15
    公開日: 2009/06/03
    ジャーナル フリー
    Crack nucleation sometimes occurs at the underhead fillet of a bolt when it is galvanized. The phenomenon is generally known as liquid zinc embrittlement, but the effect of the pretreatment such as the acid pickling on liquid zinc embrittlement is not well known.
    In the present study, to investigate the effect of the pretreatment on liquid zinc embrittlement, the observations of the crack on the longitudinal section and the fracture surface at the underhead fillet of bolts which were subjected to various pretreatments were performed by using an EPMA and an optical microscope. The main results are as follows:
    (1) The acid pickling accelerated crack nucleation.
    (2) The value of pH in fluxing affected the crack nucleation.
    (3) The shot blasting had the effect of preventing crack nucleation.
  • 中島 正貴, 加藤 容三, 清水 利弘
    1991 年 40 巻 452 号 p. 601-607
    発行日: 1991/05/15
    公開日: 2009/06/03
    ジャーナル フリー
    Small crack growth characteristics under variable loading were investigated on high strength steel SNCM439 in room air and distilled water. Under repeated two-step variable loading in room air, the crack growth rates of small cracks at lower stress and higher stress levels decreased and increased respectively, as compared with those at constant stress amplitude. In distilled water, on the other hand, the decrease in crack growth rate at lower stress level was not observed below a crack length of 0.5mm, while the crack growth rate at higher stress level decreased as compared with those at constant stress amplitude, which was attributed to crack branching. In order to clarify the effect of crack length on retardation behavior, tests were conducted under Hi-Lo two-step loading at constant stress intensity factor range (ΔK=11MPa√m→7MPa√m). It was found that the retardation cycles in both environments increased markedly with increasing crack length until they reached a constant value corresponding to long crack data, but it was smaller in distilled water than in room air.
  • 服部 修次, 井 暁天, 岡田 庸敬
    1991 年 40 巻 452 号 p. 608-612
    発行日: 1991/05/15
    公開日: 2009/06/03
    ジャーナル フリー
    The influence of corrosive environment on the fatigue-strength distribution was studied for a carbon steel. A standard deviation of the fatigue strength at 107 cycles increased to three halves in mild aqueous environments such as ion-exchanged water, as compared with that in laboratory air, and it decreased to a half in severe environments such as synthetic seawater. In laboratory air, the fatigue life varied mainly due to the scatter of crack initiation. In mild aqueous environments, many cracks initiated uniformly on the specimen surface in an early stage and grew at a similar rate, and the difference in time to the coalescence of cracks caused the dispersion of fatigue life. However, in severe aqueous environments, localized crack-initiation occurred in the corroded region, and the fatigue life or the fatigue strength scattered less because of the easiness of the coalescence of growing cracks.
  • 中佐 啓治郎, 中塚 純一
    1991 年 40 巻 452 号 p. 613-618
    発行日: 1991/05/15
    公開日: 2009/06/03
    ジャーナル フリー
    In order to quantify the crack branching morphology of brittle materials under axisymmetric tension, the “branching dimension” was defined in the present paper, and the relation between the branching dimension and fracture mechanics parameters was introduced.
    The branching dimension Db is defined as: Db=d(logLi)/d(logai), where Li is the total crack length after i-th crack branching has occurred and ai is the crack length which corresponds to the distance from crack nucleation point to crack tip. When the nominal stress σi varies with increasing crack length ai according to the relation, σi0=(ai/a0)m, the branching dimension Db can be expressed by:
    Db=2+2m=2+2·d{log(σi)}/d{log(ai)}
    where σ0 and a0 are the stress and the crack length at crack initiation. Moreover, Db can be expressed by the change of the number of cracks, n, with increasing crack length, ai:
    Db=1+d{log(n)}/d{log(ai)}
    The branching dimension can well characterize the branching patterns obtained from the flexural test of Pyrex glass, ceramic and high strength steel specimens.
  • 青木 繁, 浦井 芳洋
    1991 年 40 巻 452 号 p. 619-624
    発行日: 1991/05/15
    公開日: 2009/06/03
    ジャーナル フリー
    The method for estimating the galvanic corrosion rate was discussed. In case where the electrochemical polarization curves of metal in the electrolyte considered are available, the galvanic corrosion rate can be estimated by solving the Laplace equation with boundary conditions based on the polarrization curves. The polarization curves, however, are not always available. In this case, it is necessary to estimate the density of current across the metal surfaces from the measured potential values at some points away from the metal surface.
    This inverse problem was formulated by employing the boundary element method. Since the system of linear equations obtained was ill-conditioned, some regularization methods, including singular value decomposition, smoothing method and spline method, were applied and the accuracies of these estimation methods were compared. In order to improve the accuracy, a new method using fuzzy clustering techniques was developed. An example problem was solved by the new method in order to demonstrate the accuracy.
  • 浦上 良樹, 中尾 敏隆, 高島 昭次郎, 石井 邦男
    1991 年 40 巻 452 号 p. 625-629
    発行日: 1991/05/15
    公開日: 2009/06/03
    ジャーナル フリー
    In our previous report, it was pointed out that the conventional adhesion test was not an apropriate method to monitor the adhesion strength of resin lined to concrete when comparing with the real cases in the field where the resin lining was peeled off from concrete.
    In this report, the peeling phenomenon of the resin lining was observed and its mechanism was examined on the basis that the peeling of resin was initiated and promoted by the permeating pressure of water from concrete. Finally two test methods, flexural test (center point loading) and peeling test (90°) were studied as the candidates for a new test method to monitor the adhesion strength of resin lining.
    Although one case of resin peeling which was not detected by the conventional adhesion test was detected by the flexural test, it appeared to be not so accurate. In case of the peeling test, it was assured that the resin which had the conventional adhesion force of ten to several tens of kgf/cm2 was peeled off by the force of less than several kgf/cm, and the peeling strength was fairly affected by W/C of mortar. Therefore, this peeling test (90°) might be a good new test method for the purpose.
  • 谷本 親伯, 吉岡 尚也
    1991 年 40 巻 452 号 p. 630-636
    発行日: 1991/05/15
    公開日: 2009/06/03
    ジャーナル フリー
    Convergence monitoring is a simple measurement. It can be easily carried out during construction, and provides serial information on the deformation of tunnel wall. When the ground behaves as an elastic body with no time dependency, the curve of convergence reaches a constant level within the range of a double distance of the tunnel diameter in the driving direction. On the other hand, when the ground is subject to the inelastic behaviour, deformation converges in the distance of 3 to 10 times longer than the tunnel diameter.
    The authors analyzed in detail the results of convergence measurements obtained from 60 tunnelling sites, and clarified the relationship between deformation and support load.
  • 岸本 哲, 江頭 満, 新谷 紀雄
    1991 年 40 巻 452 号 p. 637-641
    発行日: 1991/05/15
    公開日: 2009/06/03
    ジャーナル フリー
    A new Moiré method using a scanning electron microscope has been developed for the measurements of micro-deformation. In this method, the model grid is fine parallel lines of metal deposited on a specimen, and as a master grid, the electron beam of a SEM is used. The scanning of electron beam on the specimen with the model grid constructs a Moiré fringe. This fine Moiré fringe in a small area makes it possible to determine the distribution of strain around a small notch, the deformation within a grain and grain boundary sliding.
    For demonstrative experiments, tensile and creep tests of polyimide resin and pure copper specimens were carried out. In the tensile test of a polyimide resin specimen with a small hole, an observation of the electron beam Moiré fringe was performed in-situ in a SEM during loading. The Moiré fringes for copper specimens were observed after high temperature tensile test (673K) and interrupted creep test (723K and 30MPa). It is found that electron beam Moiré fringes are fine and clear enough to measure the strain distribution in a small area (about 500μm square) around a hole in a polyimide resin specimen. The strain distribution around a small hole was calculated from an analysis of the fringes and a strain contour map was constructed.
    The Moiré fringe in the copper specimens shows complicated patterns due to some metallurgical behaviours. The pattern was analysed. Grain boundary sliding could be measured with high accuracy from the displacement of Moiré fringe at grain boundary, and deformation in a grain and coarse slip bands could be observed from change in the Moiré fringe patterns in relation to micro-deformation modes. Also inhomogenious deformations at triple points and rotation caused by grain boundary slidings in a crept specimen were observed using this method.
  • 2. 材料の高速変形挙動の特徴
    谷村 眞治
    1991 年 40 巻 452 号 p. 642-648
    発行日: 1991/05/15
    公開日: 2009/06/03
    ジャーナル フリー
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