材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
43 巻 , 486 号
選択された号の論文の19件中1~19を表示しています
  • 倉鋪 憲, 岩本 正治, 荒木 栄敏, 安 偉
    1994 年 43 巻 486 号 p. 248-253
    発行日: 1994/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    The purpose of the present work is to reveal the behavior of two kinds of different matrix resins in composite materials through the experimental results of mechanical and fracture properties and observation of macro and micro fracture surfaces. The composite specimens are made of ductile or brittle resin and continuous glass fiber mats with various fiber contents. The elastic modulus and the tensile strength of these two resins are nearly of the same values, while the elongation is different.
    The results obtained are as follows:
    (1) The tensile strength of the ductile matrix resin composites is higher by 20-30% than that of the brittle matrix resin composites. The values of both composites with fiber content 20wt%, however, are lower than those of the matrix resins. These results can be understood based on the observations of macro fracture processes and fracture surfaces.
    (2) The fracture toughness Kin at crack growth initiation increases with increasing fiber content for both composites. The values of Kin for the ductile matrix resin composites with fiber contents 0wt% and 20wt% are higher than those of the brittle ones. For the composites with fiber contents 40wt% and 60wt%, the values of Kin for both composites scatter randomly.
  • 根本 圭一, 粕谷 平和
    1994 年 43 巻 486 号 p. 254-258
    発行日: 1994/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Advanced fiber-reinforced composite materials are being used for structural members, because of their high specific strength and stiffness. This paper deals with the problem of dynamic stability of angle-ply laminated cylindrical shells subjected to static and periodic external pressure. First, the axially symmetric motion of the shell under the loading is determined. Subsequently, certain perturbations are superimposed on this motion, and their behavior in time is investigated. The symmetric state of motion of the shell is called stable if the perturbations remain bounded. The solutions for the prebuckling motion and the perturbated motion are obtained by the use of Galerkin's method. Stability regions are examined by utilizing Mathieu equation. The inevitability of dynamically unstable behavior is proved analytically and the effects of various factors, such as lamination angle, fundamental natural frequency, vibrated amplitude, dynamic unstable mode and dimension of cylinder, are clarified.
  • 三木 光範, 杉山 吉彦, 坂本 慎介
    1994 年 43 巻 486 号 p. 259-264
    発行日: 1994/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    In this paper, an optimum design method of laminated composites for load with deterministic variations is proposed. A deterministically variable load has a given variation represented by a domain of variation. The optimum configuration is obtained such that the laminate thickness is minimized under the constraint where the first ply failure does not occur with respect to the given loading region.The method used for the minimization is a nonlinear mathematical programming method. From the results, the optimum laminate construction approaches to that of quasi-isotropic laminates for load with variations. It is found that the most dangerous loading condition for laminated composites, which is called the control point of failure, is different depending on the characteristics of variations and the anisotropy of materials, and that it is not always the maximum loading point with respect to each component.
  • 座古 勝, 辻上 哲也, 津村 卓也
    1994 年 43 巻 486 号 p. 265-270
    発行日: 1994/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    A computer program of two-dimensional Finite Element Method (FEM) with a new concept based on damage mechanics has been developed to analyze the mechanical behavior during the progression of fracture in composite materials. The fracture patterns of composite materials are very confusing, since many kinds of damage like resin cracks, fiber breaking and delamination etc. take place.Two characteristics have to be considered in order to describe the damage of anisotropic body like composite materials. One is its progression rate the other is its direction. A numerical procedure for the stiffness matrix of FEM with damaged elements has been introduced in this paper. As the example, the fracture mode of hybrid composites under four-point bending test was analyzed by the developed computer program. In addition, the mechanical behavior under tensile load after bending load was analyzed. The computational results concerning fracture mode and mechanical behaviors agreed well with the experimental results. Consequently, it can be recognized that the developed computer program considering damage is very useful for the analysis of mechanical behavior for composites which have anisotropic properties.
  • 藤井 善通, 久保田 智子, 前川 善一郎, 濱田 泰以, 村上 惇, 吉識 忠継
    1994 年 43 巻 486 号 p. 271-277
    発行日: 1994/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    It is well known that an acid corrosion phenomenon, called environmental stress cracking, appears on E-glass fibers in GFRP. Acid diffusion into a matrix resin, however, does not occur without loading. In this study, the initial damage was observed during pre-stressing by a microscope. The relationship between the initial damage and the generation of AE in the tensile tests under air and acidic environments was examined by using test specimens with or without pre-stressing. SEM observation on the fractured surface of these specimens was also performed. The matrix resins used in the test had different toughness. The observation confirms that the existence of initial damage such as cracks governs the acid corrosion behavior of GFRP. It is found that the cracks, developed as the initial damage, allow acid to transport rapidly in the resin. Eventually, GFRP is easily fractured at a lower stress than the fracture strength of the original GFRP.
  • 大平 晃聡, 日和 千秋, 猪飼 靖, 中川 隆夫
    1994 年 43 巻 486 号 p. 278-282
    発行日: 1994/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    At the present, there are many kinds of methods to evaluate the interfacial strength of composites, for example, fragmentation test of a single fiber, single fiber pull-out test, torsion test and shear test. But there are few non-destructive methods. Therefore, as a new method for evaluation of the interfacial strength of composites, the interfacial strength was studied from viewpoint of balance stress. The balance stress of the composites occurs by viscoelastic properties of the material, and it reflects strongly the stress redistribution between fibers and resin. The balance stress depends on the degree of the stress transition from resin to fibers, and so it is obtainable from a viscoelastic model consisting of three elements. The theoretical values of the balance stress agreed with the experimental results. Two types of composites made of the same epoxy resin were prepared. One was a coupling treated on the fiber and the other was untreated. The balance stress of the treated composite was large due to strong adhesion at the interface. It is clear that the relative interfacial strength of composites can be estimated by the balance stress.
  • 北出 真太郎, 福田 武人, 逢坂 勝彦
    1994 年 43 巻 486 号 p. 283-289
    発行日: 1994/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    An optical fiber was embedded between two central laminates of the specimen, and the influence of the embedded optical fiber on interlaminar shear strength was investigated. First, the interlaminar shear strength (ILSS) was measured by a short beam three point bending method. The Optical fiber was embedded parallel to the reinforced direction (specimen type A), or perpendicular to the reinforced direction (specimen type B). The result of interlaminar shear test showed that in the specimens of type A, there was no noticeable deterioration on ILSS. In the specimens of type B, as the distance between the loading point and the optical fiber increases, ILSS decreased slightly, and the position of fracture surface shifted toward the embedded optical fiber. Secondly, the distribution of the volume fraction of reinforced fibers along the thickness direction was measured by thresholding technique of image processing. In the specimen in which the optical fiber was embedded perpendicular to the reinforced direction, the volume fraction of fibers increased significantly near the embedded optical fiber. It was considered that this increase in volume fraction of fibers influenced the deterioration of ILSS. Thirdly, to discuss the shift of fracture surface, the stress distribution was analyzed by using finite element analysis. At the position of the specimen where the optical fiber was embedded, two shear stress peaks can be seen inside of the composite. This result shows that the embedded optical fiber changes the stress distribution around the optical fiber and causes the shift of fracture surface.
  • 小林 佑規, 田中 義久
    1994 年 43 巻 486 号 p. 290-296
    発行日: 1994/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    This paper reports the results of impact tension of laminated plates reinforced with five harness satin of aramid roving cloth, glass roving cloth, glass chopped strand mat, glass mat and aramid cloth, and glass mat and glass roving cloth. Impact tensile tests of the matrix resin were also performed. The strain rare was within the range of 40sec-1. The stress-strain diagrams were prepared from the strain and load responses under impact. The results are summarized as follows:
    The strong strain rate dependence on strength, elastic modulus, and absorbed energy was observed in the FRP laminates and matrix resin. The elongation to crack initiation was constant in GFRP when the strain rate was more than 5sec-1, but decreased with an increase of strain rate in AFRP. The breaking and crack initiation strength increased up to the critical strain rate, that is a strain rate of the maximum strength. The critical strain rate becomes a characteristic value by a kind of reinforcement, textile weave, laminate constitution, or matrix resin. The value is useful in evaluating impact resistance of different laminates. The impact fracture is caused by the embrittlement of the matrix resin, and notch sensitivity increases at the crossing points of roving cloth in impact tension.
  • 石原 茂久
    1994 年 43 巻 486 号 p. 297-303
    発行日: 1994/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Fire-retardant plywood panels of lauan (Shorea negrosensis Fox) were pressure treated with a phosphoric acid containing melamine-formaldehyde condensate as a leach-resistant fire retardant and with diammonium hydrogen phosphate, guanidine phosphate, minalith and pyresote as non-leach resistant fire retardants. Their fire retarding efficiency and bending strength were measured after 1, 2, 3, 7 and 15-year outdoor exposure at the experimental field of the Wood Research Institute, Kyoto University, Uji, Kyoto.
    The fire retarding efficiency and burning behaviors of the fire retardant plywood in comparison with those of the non-treated ones were evaluated while being subjected to a fire test under a high radiation furnace. The burning behaviors such as: the ignition time and time-temperature of the fire-exposed surface; the time at which the unexposed surface reached the critical temperature of 260°C; the afterflame; and the afterglow of the specimens, as indications of fire retarding efficiency, were measured. The relationships between the modulus of rupture and/or modulus of elasticity of the specimen plywood and the exposure period were also discussed.
    The fire retarding efficiency of the fire retardant plywood decreased proportionately with longer exposure time. The fire retardant effectiveness of the plywood treated with inorganic fire retardants, such as diammonium hydrogen phosphate, guanidine phosphate, pyresote and minalith, was almost negligible after a year of exposure. However, the fire retardant effectiveness of those treated with phosphoric acid containing melamine-formaldehyde condensate was slightly remarkable even after seven years of outdoor exposure.
    The durability of the fire retardants was in the order of pyresote, diammonium hydrogen phosphate, guanidine phosphate, minalith and phosphoric acid containing melamine-formaldehyde condensate. The percentage loss in the bending strength were 10-20%, 40-65% and 50-70% after 1, 7 and 15-year exposure period, respectively.
  • 小川 欽也, 小林 秀敏, 吉田 邦裕, 杉山 文子
    1994 年 43 巻 486 号 p. 304-309
    発行日: 1994/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Compressive strength of β-Titanium alloy (Ti-15V-3Cr-3Sn-3Al) has been investigated in the wide temperature range of 77 to 673K and at strain rates from 10-4 to 2×103S-1. The stress-strain relations are influenced by the change of temperature arizing from the heat conversion of plastic work, while almost independent of the temperature and the strain rate histories. The thermal component of the stress can be uniquely determined by the Larson-Millar parameter, and the athermal component is a function of strain only. The thermally activated process concept gives a whole understanding of the present experimental results by taking account of the adiabatic heating effect at high strain rates of more than 102S-1.
  • 長谷部 忠司, 坂根 政男, 大南 正瑛
    1994 年 43 巻 486 号 p. 310-316
    発行日: 1994/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    This paper studies yield surface and stress amplitude ellipse for Nickel-base single crystal (SC) superalloy CMSX-2 and directionally solidified (DS) superalloy Mar-M247LC under multiaxial cyclic loadings. Mises' strain controlled tension/torsion cyclic loading tests were carried out at 1173K in air and the stress-strain relations were obtained experimentally. The inelastic constitutive equation based on slip theory, taking account of {111} ‹110› octahedral and {100} ‹110› cube slip systems, was developed. The yield surface and stress amplitude ellipse obtained from the slip theory were compared with the experimental results. The theory well explained the plastic deformation behavior for SC and DS superalloys, where somewhat different plastic deformation behavior was found between the two superalloys, caused by the different contribution of the two slip systems. Coaxiality between the Mises' stress and strain was extensively discussed based on the slip theory.
  • 鄭 教〓, 市川 康明
    1994 年 43 巻 486 号 p. 317-323
    発行日: 1994/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Microcracks during complex loading could result from the tensile stress concentration around such flaws as grain boundary microcracks, intracrystalline microcracks and microcavities. Therefore, detailed knowledge about microcracks substantially contributes to the interpretation of damaging process, microcrack-induced dilatancy and failure in intact rock.
    In the present study, a direct observation of actual damage propagation in intact granite specimens which are cut from a block of coarse grained granite was carried out by a newly developed experimental system. Microscopic observation shows that an incipient micro-damage is generated at two grain contact portion due to elastic mismatch of the two grains, and their morphologies are parallel or subparallel to the axial stress direction. The detailed observation of an incipient shear fracture in a granite specimen suggests that the fracture is formed by the coalescence through the inclined grain boundaries of links between echelon intracrystalline microcracks.
  • 西田 新一, 服部 信祐, 島田 鉄也
    1994 年 43 巻 486 号 p. 324-328
    発行日: 1994/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Fatigue behavior of high manganese non-magnetic austenitic steel (HM steel) was studied through the rotating bending fatigue tests using plain specimens with a partial shallow notch by means of the successive-taken replica method. This behavior was compared with that of an austenitic stainless steel (SUS304). The experimental results showed that the fatigue limit of HM steel was the same as that of SUS304, and distinct knee point was observed in S-N curve of both materials. It was found that the fatigue cracks of these materials initiated at grain boundaries or in its neighborhood.
    It was apparently observed that some non-propagating micro-cracks existed in the specimen surface of HM steel subjected to the stress cycling of fatigue limit by 107 cycles, while no micro-crack existed in the specimen of SUS304 subjected to the same stress condition.
  • 駒井 謙治郎, 箕島 弘二, 伊藤 雅彦
    1994 年 43 巻 486 号 p. 329-335
    発行日: 1994/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    This investigation demonstrates that scanning tunneling microscopy (STM) and atomic force microscopy (AFM) (scanning probe microscopy) are capable of performing in-situ nanoscopic visualization of initiation and growth processes of localized corrosion in aqueous solutions. We discuss advantage and disadvantage of STM and AFM for in-situ visualization in aqueous solutions: an AFM is more suitable compared with an STM for in-situ visualization of localized corrosion damage, from the standpoints of scanning speed, stability and capability of imaging non-conducting surface of corrosion products. The nanoscopic initiation and growth mechanisms of localized corrosion of pitting corrosion and intergranular corrosion of a sensitized austenitic stainless steel and 7XXX series aluminum alloys are discussed based upon nanoscopic in-situ visualization by using STM/AFM.
  • 駒井 謙治郎, 箕島 弘二, 伊藤 雅彦
    1994 年 43 巻 486 号 p. 336-342
    発行日: 1994/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Most damage issues in machines and structures are caused by environmentally induced material degradation in an operating environment, including stress corrosion (SC) cracking. In order to clarify the fracture and damage mechanisms of these environmentally induced material degradation, serial high-magnification obsearvation of damage initiation and growth stages is necessary. In this investigation, the authors demonstrate that atomic force microscopy (AFM) is very much capable of performing in-situ nanoscopic visualization of growth processes of SC cracking in an aqueous solution and in a laboratory air. The nanoscopic growth mechanisms of SC crack growth of a high-strength aluminum alloy and an austenitic stainless steel are discussed based upon nanoscopic in-situ visualization by AFM and scanning tunneling microscope (STM).
  • 北條 浩, 猿木 勝司, 山田 明
    1994 年 43 巻 486 号 p. 343-347
    発行日: 1994/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    A new method of predicting the fatigue lifetime of ceramics with various sizes of defects has been developed. In this method, first, specimens each of which has an artificial crack of constant size are used to estimate fatigue crack propagation parameters. In the vicinity of the tip of an artificial crack induced by Knoop indentation, a tensile stress field is generated. Then, the stress intensity factor acting as the driving force of fatigue crack growth was considered the sum of two terms associated with the applied stress and residual stress field. By numerical computation inserting the stress intensity factor into the power law of crack propagation, crack propagation parameters are estimated. Subsequently, using the obtained parameters, the fatigue lifetimes of the smooth specimens with fracture originating from a small defect, are predicted.
    This method was applied to three types of silicon nitride ceramics. As a result, the cyclic fatigue lifetimes of precracked specimens, which were set free from residual stress field by surface removal, were precisely predicted using the obtained parameters. Thus, the values of these parameters were proved to be adequate. Furthermore, the predicted fatigue lifetimes of the smooth specimens were in good agreement with the experimental results, considering the scatter of static strength.
  • 園家 啓嗣, 北川 正樹, 村田 正治, 田中 秀雄, 八木 晃一
    1994 年 43 巻 486 号 p. 348-353
    発行日: 1994/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Temperature-accelerated creep rupture tests were performed by using miniature specimens of 2.25Cr-1Mo steel and 18Cr-8Ni steel, and an iso-stress method was examined to predict the long term creep rupture time by extrapolation from short time data. The results obtained are as follows.
    (1) For 2.25Cr-1Mo steel, the accuracy of remaining life prediction in the long duration side becomes better by correcting it on the basis of rupture ductility.
    (2) For 18Cr-8Ni steel, the remaining life in the long duration side can be predicted accurately, when the change of microstructure does not influence creep rupture life.
    (3) When the above method was applied to an actual boiler, an accurate life assessment was possible. This method is confirmed to be effective.
  • 八尾 滋, 曽根 将則, 亀井 衛一
    1994 年 43 巻 486 号 p. 354-359
    発行日: 1994/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    There has been a widespread interest in polymer alloys for the development of new polymeric materials. These materials have heterogeneous disperse multiphase structures (particles) and the practical properties such as impact strength depend mainly on these disperse structures. So, for the research and development in this area, it is important to know the most favorable disperse structure, and the method to get it. If we could predict the mixing condition which leads to the most favorable disperse structure of the polymer blends, then we could conduct an efficient research and development. It is well known that the disperse structures from the mixing of polymer melts depend mainly on the interfacial tension and the viscoelastic properties of each component.
    Recently, we developed a new theory which quite accurately predicts the interfacial tension between polymer melts from their chemical structures.
    Depending on this development, we also constructed an expert system that predicts the kinds of disperse structure, sizes of the dispersed particles, and the interfacial distance between the dispersed particles.
  • 小沢 一雅, 関 博
    1994 年 43 巻 486 号 p. 360-366
    発行日: 1994/03/15
    公開日: 2009/06/03
    ジャーナル フリー
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