材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
47 巻 , 12 号
選択された号の論文の18件中1~18を表示しています
  • 米澤 政昭, 奥田 昇也, 朴 永太
    1998 年 47 巻 12 号 p. 1204-1209
    発行日: 1998/12/15
    公開日: 2009/06/03
    ジャーナル フリー
    This paper describes a new numerical integration method for evaluating structural failure probability. The proposed method utilizes the centerline directional vectors, which are related to the specified numbers of finite element meshes divided on the surface of the unit hypersphere. The failure probability is evaluated numerically by using the values of hyperareas of the finite element meshes and conditional failure probabilities on the centerline directions of the meshes. To save computational efforts, the calculation of the conditional failure probabilities is restricted in the effective directional regions, where all the distances from the origin to limit state surfaces are short enough and within the limit of the effective distance range. The effective distance range is determined in the preliminary search procedure to get the information about the limit state surfaces situation.
    Numerical examples are presented to illustrate the validity of the proposed method to evaluate the structural failure probabilities.
  • 酒井 達雄, 伊藤 敬
    1998 年 47 巻 12 号 p. 1210-1215
    発行日: 1998/12/15
    公開日: 2009/06/03
    ジャーナル フリー
    Amorphous alloys have superior electro-magnetic properties such as low core loss, high magnetostriction and high saturation induction, so that they have been used as the electro-magnetic materials in a wide variety of magnetic reading heads, magnetic sensors, power transformer cores and so on. Another advantageous property of amorphous alloys is the excellent mechanical property as well as the high registance in the corrosive environments. In order to obtain fundamental data for the mechanical uses, tensile strength of the amorphous alloy ribbons was experimentally examined together with its distribution pattern. Based on the results at some different temperatures, temperature dependence of the tensile strength distribution was analysed by means of Weibull statistics in the present study.Thus we have the following aspects; The strength distribution is independent on the temperature in T≤300°C, but the scatter of the strength becomes distinct at T=400°C in relation to the crystallization. The strength tends to decrease and the scatter becomes small again at T=500°C due to the complete crystallization for all specimens. It was found that the distribution characteristics at T=400°C were well explained by the mixed-mode Weibull distribution consisting of component distributions for amorphous and crystalline specimens.
  • 金子 真, 中村 孝, 野口 徹
    1998 年 47 巻 12 号 p. 1216-1220
    発行日: 1998/12/15
    公開日: 2009/06/03
    ジャーナル フリー
    Many high strength materials, including high strength steels and high strength titanium alloys, show the complex characteristics of fatigue life distribution in the high cycle region. It is caused by the two competing fracture modes, fractures from surface and from interior of the specimen. A method to describe such a complex fatigue life data was proposed based on the competing-risk model. The characteristics of fatigue life distributions and S-N relations of each mode were successfully separated and extracted from whole data. These separated data was analyzed and the complex fatigue life distributions was well described by the competing-risk model. The method is helpful to understand the fatigue mechanisms because the fatigue life distribution of different two modes results from and reflects the fatigue mechanism of each mode.
  • 高橋 学, 岡部 永年, 小林 英男
    1998 年 47 巻 12 号 p. 1221-1226
    発行日: 1998/12/15
    公開日: 2009/06/03
    ジャーナル フリー
    Room and high temperature four point bend tests for Si3N4/SUS304 joints were carried out at constant loading.Fracture surfaces of the interlayer of joints were observed using SEM to discuss the fracture mechanism at high temperature. Furthermore, the fracture strength distribution was estimated on the basis of the unified estimation method considering the fracture mechanism.
    (1) Failure of brazed Si3N4/metal joints in high stress level was occurred at a flaw in ceramics near bonding interface. On the other hand, failure of the interlayer in low stress level was occurred due to creep rupture. Creep rupture of joints was dominated on steady-state creep of the interlayer. Then, creep rupture life also could be predicted from minimum creep strain rate in interlayer by using both equation of Monkman-Grant and Norton's law.
    (2) The fracture strength of the joints could be evaluated considering the temperature dependence of strength as follows:
    σf·teff1/njfexp[(-Qi/k)(1/T+273-1/Tθ+273)]mi√ln(1-Pf)-1
    (3) Reliability structural design of joints had better determine the stress level and proof life considering failure of the interlayer with small scatter of rupture lives.
  • 理論解析とシミュレーションの推定精度が異なる要因
    松村 隆, 市川 昌弘
    1998 年 47 巻 12 号 p. 1227-1232
    発行日: 1998/12/15
    公開日: 2009/06/03
    ジャーナル フリー
    In recent years, attempts have been made to apply the statistics of extremes to the estimation of maximum crack length in a structural component. However, a guide for determining the sample area S and the number of divisions m that influence the estimation accuracy of maximum crack length have not been obtained. In a previous paper, the authors showed that √V(Xmax)/σ by the theoretical analysis is not equal to √V(Xmax)/σ by Monte Carlo simulation for the case when crack lengths follow exponential and Weibull distributions, where √V(Xmax) is the root mean squared error of the estimated value, and σ is the variance of the double exponential distribution which the largest crack length in each elemental area follows. It was also shown that this difference was due to √V(Xmax). In the present paper, it is shown that the difference in values is due to the fact that the theoretical analysis differs from Monte Carlo simulation in the definition of the true maximum crack length, Xmax, for the case when crack lengths follow an exponential distribution. It is also shown that the difference in values is due to the fact that the theoretical analysis differs from Monte Carlo simulation in the definition of Xmax and that the largest crack length in each elemental area by Monte Carlo simulation does not strictly follow the double exponential distribution for the case when crack lengths follow a Weibull distribution.
  • 大倉 一郎, 石川 敏之, 渡辺 洋
    1998 年 47 巻 12 号 p. 1233-1238
    発行日: 1998/12/15
    公開日: 2009/06/03
    ジャーナル フリー
    Recently there have been many reports on the stress measurement of highway bridges. However, a generalized method is not still provided on how to introduce the results of stress measurement into the fatigue reliability assessment. In this paper, two new parameters, called “fatigue resistance c” and “fatigue-damage-accumulation q”, are proposed to make it easy to introduce the results of stress measurement of a monitored bridge into the fatigue reliability assessment of highway bridges. Using a fatigue test database, the probability distribution of c is determined for various structural details. It is shown that for fatigue failure, the assumption of q=c is equivalent to the Miner's linear damage rule. The characteristics of the fatigue-damage-accumulation q of highway bridges are discussed. The application of the advanced first-order second-moment method to the state function of g=c-q gives the fatigue reliability assessment of highway bridges. It is expressed in terms of the design equivalent stress range and the allowable fatigue stress range with partial safety factors. The relation between the safety index and the lapse of time from opening to traffic is formulated. The safety index is shown to decrease with the time in logarithm scale.
  • 中山 隆弘, 川谷 充郎, 車谷 真吾, 古岩 功三
    1998 年 47 巻 12 号 p. 1239-1244
    発行日: 1998/12/15
    公開日: 2009/06/03
    ジャーナル フリー
    The effect of the scatter of fatigue life data and the effect of traffic-induced vibration of highway bridges on evaluations of their fatigue failure probability have been investigated through a reliability approach with the dynamic response analysis.
    Highway bridges are subjected to a large number of repeated load cycles which have random variable amplitudes during their service lives. Therefore, the prediction of their fatigue damage is popularly obtained by Miner's rule under which the damage accumulates linearly. In such a case, a cumulative damage D=Σ(ni/Ni) must be treated as a random variable with such a kind of probability function as Weibull distribution because of the scatter of the fatigue life Ni under the constant amplitude stress Δσi, in which ni is the number of stress reversals at a level Δσi.
    This paper describes a simple method for obtaining the probability density function of the cumulative damage given by the sum of (ni/Ni) by the use of the mathematical theorem that the probability density of the sum of two independent random variables equals the convolution of their densities. Following this procedure, the fatigue failure probability can be obtained by calculating the probability P{D>1}. Furthermore, the fatigue failure probability of a highway bridge subjected to a moving vehicle is evaluated by the proposed method based on the dynamic response analysis of the bridge.
  • 古田 均, 金森 敦司, 堂垣 正博
    1998 年 47 巻 12 号 p. 1245-1250
    発行日: 1998/12/15
    公開日: 2009/06/03
    ジャーナル フリー
    In this paper, an attempt is made to develop a decision supporting system for the maintenance program of Reinforced Concrete (RC) decks of highway bridges. Emphasis is placed on how to obtain an appropriate order of repair for the existing RC decks by considering the characteristics of highway network and the concept of life cycle cost. Namely, in order to account for the importance of each bridge and the adequate resource allocation, the influence of repair works on the surrounding areas and various practical technical and economical conditions for their repair are considered. Genetic Algorithm (GA) is employed here to find a practical and rational solution for the maintenance problem, because GA has such an advantage that it can provide us with useful solutions for large and complex combinatorial and scheduling problems with discontinuous or vague objective functions. Moreover, fuzzy reasoning is applied to express the objective functions in a flexible manner such as “If-Then” rules. Several numerical examples are presented to demonstrate the efficiency of the system developed here.
  • 岡部 永年, 阿部 豊, 市川 昌弘, 高松 徹, 菅 則雄
    1998 年 47 巻 12 号 p. 1251-1257
    発行日: 1998/12/15
    公開日: 2009/06/03
    ジャーナル フリー
    Ceramics of typical brittle material can not relieve even the extremely concentrated stress such as Hertz contact stress though local plastic deformation. And so the ceramic fracture is occurred from even comparative small microscopic defect. Using ceramics for structure combined with some components, extremely high contact stress is used to generate in the ceramics contacted locally with other components. Hertz contact stress of ceramics subjected to contact load have extremely concentrated stress distribution but is very higher in fracture strength bending or tensile fracture strength by the method of standard tests. Due to occurrence of high contact stress, ring crack is generated at contact boundary. On considering the ring crack stress to evaluate the ceramic allowable strength against contact load, the ceramic strength must not be judged from the strength gotten by bending or tensile test. This ring crack initiation strengths are governed only by extremely small defects exiting within the extremely narrow contact stress field in ceramics. Therefore, stress intensity factor KI must be used for evaluating the fracture criteria of ceramics because of requiring to consider not only stress distribution but also defect size within contact stress field.The ceramic fracture occurs under condition of KIKIC. On the other hand, the distribution of KI indicates maximum value at the radius direction position of about r/a=1.2 outside of contact boundary: r=a. Both of defect sizes and ring crack initiating positions disperse generally and so ring crack initiating strengths estimated from KIKIC, also, disperse inevitably. However the dispersions are very small owing to extremely narrow extent of defect sizes relating to ring crack initiation and indicate Weibull distribution with extremely large shape parameter m and scale parameter σ0 compared with usual strength by standard bending or tensile tests. This study could make clear of ring crack initiation mechanism and ring crack strength properties by probabilistic simulation analysis against the contact model combined a ceramic ball and a ceramic plate.
  • 西岡 俊久, 加藤 哲二
    1998 年 47 巻 12 号 p. 1258-1263
    発行日: 1998/12/15
    公開日: 2009/06/03
    ジャーナル フリー
    The materials containing damages and defects cause the reduction of stiffness of mechanical components. In this paper, a damaged material is regarded as the assembly of periodically distributed unit cells containing one or more elliptical microcracks. An alternating method based on the VNA (Vijayakumar-Nishioka-Atluri) solution is used to solve the problems of periodically distributed elliptical microcracks. The information on the deformation of the central cell (called representative cell) is used to evaluate the effective elastic moduli. Interaction effects of periodically distributed elliptical microcracks are completely included in the present solutions. The effective elastic moduli for various types of damaged materials are estimated. To clarify the mechanism of interaction behavior of microcracks, the stress distributions in the damaged materials are visualized. The presently developed analysis method made it possible to simultaneously estimate microscopic as well as macroscopic material properties such as the stress intensity factor distribution of each microcrack and the effective elastic moduli.
  • 粉砕マトリックスの応用
    尾崎 都司正, 金井 浩志, 三輪 茂雄, 原 敬, 小沼 栄一
    1998 年 47 巻 12 号 p. 1264-1269
    発行日: 1998/12/15
    公開日: 2009/06/03
    ジャーナル フリー
    The grading technology with crushing and grinding is necessary to produce materials like natural river sands and to obtain sub-micron powders for the materials for electronic devices and surface lining. It is known that grinding operation is the representative method, and it may be possible to grade particles. But in the field of grading particles, it is not common to study the grading phenomena in the process of grinding by the time, especially to study the particle size distribution of coarse powder in the closed circuit grinding system. Based on the analogy of sieving model by the Information theory, this paper led to the result by the time dependence equation in the grinding process, and it showed that the obtained equation has similarity to that of grinding Matrix. Moreover, the grading mechanism of the sands was figured out by verifying the equation of the closed circuit grinding system, using Onuma's data and graded sands or booming sands. And also, the paper suggests that applying another technology is very effective to save energy at the point that the transfer from volume grinding to surface grinding had occurred. And the examination of the materials could be useful in making a plan to produce the range of the particle size.
  • PBT/PEブレンドのモルフォロジー
    北川 和男, 仙波 健, 濱田 泰以
    1998 年 47 巻 12 号 p. 1270-1275
    発行日: 1998/12/15
    公開日: 2009/06/03
    ジャーナル フリー
    In a poly (buthylene terephthalate) (PBT) and polyethylene (PE) immiscible blend, we found that a PBT component could form fibro-reinforcements in PE matrix during compounding and injection molding. Extruded strands were subjected to drawing at cooling processes during compounding. Injection moldings were fabricated with the compounded pellets at various processing conditions in which cylinder temperatures were 190, 210, 215 and 220°C. Tensile tests and scanning electron microscopic observations were performed using drawing and non-drawing strands and injection moldings. The fibro-reinforcements of PBT were formed in skin layer of the extruded strand, while the PBT component was sphere shape in core layer. The ratio of PBT fibro-reinforcement in the drawing strand was higher than that in the non-drawing strand, so that tensile modulus and strength of the drawing strand increased. At 190°C of cylinder temperature, which was lower than the melting point of PBT, the fibro-reinforcements could be hardly formed and the tensile fracture aspect indicated quite brittle behavior. At 215°C which was between the first and the second melting point (Tm2), the ratio of fibro-reinforcement in the injection molding was the highest among all moldings. At 220°C, which was almost the same as Tm2, the PBT component was completely dissolved and next formed much more spherical shape in the core layer than the 215°C molding during injection processing.
  • 水野 渡, 泊 清隆, 濱田 泰以
    1998 年 47 巻 12 号 p. 1276-1281
    発行日: 1998/12/15
    公開日: 2009/06/03
    ジャーナル フリー
    Polyacetal was combined with polyacetal, fiber reinforced polyacetal and fiber reinforced polycabonate by a simultaneous composite injection molding (SCI. Molding) in which two different melts can be injected into one mold cavity simultaneously through two individually controlled channels. The structure and properties of polyacetal sandwich moldings were investigated as a function of molding conditions. Impact strength and mold shrinkage were strongly affected by the crystalline morphology of polyacetal. Bending properties and dimensional stability of the polyacetal composite moldings were improved by sandwich molding.
  • 馬場 文明, 藤田 章洋, 濱田 泰以
    1998 年 47 巻 12 号 p. 1282-1286
    発行日: 1998/12/15
    公開日: 2009/06/03
    ジャーナル フリー
    Liquid crystalline polymer (LCP) shows a unique structure and mechanical properties of injection molded thin strips. In this study, three kinds of thin strip, 5mm width and 0.3mm, 0.5mm and 1.0mm thickness were made by injection molding. The effects of injection speed and thickness of mold cavity on the structure and mechanical properties of carbon fiber reinforced LCP injection molds were investigated.
    Both the storage modulus and tan delta of the specimens with the thinnest thickness had the highest value. The storage modulus in both tensile and flexural modes decreased with increasing of the thickness in each specimen. Multi layer structure were observed in all specimens. The number of layers were different by the thickness and the injection speed of specimen. The fiber orientation of each layer also changed by the thickness and the injection speed of specimen.
  • 谷本 安浩, 西脇 剛史, 丹下 章男, 藤田 章洋, 前川 善一郎
    1998 年 47 巻 12 号 p. 1287-1291
    発行日: 1998/12/15
    公開日: 2009/06/03
    ジャーナル フリー
    The purpose of this study is to propose a new numerical modeling of sandwich injection moldings, in which two kinds of materials are sequentially injected from one gate with a time lag. Using this molding method, the skin and core layers can be set in same injection, respectively. The materials of excellent mechanical properties can be produced by this method in comparison with the uniform plastic. The numerical proposed model in this study consists of shell and beam elements, corresponding to skin and core layers, respectively. The validity of the new numerical model for the eigenvibration analysis of sandwich injection moldings is checked through comparisons with experimental results. Using this model, influences of skin layer properties and core area ratios upon eigenfrequency are discussed. The results indicate that the validity of the new numerical model was verified through comparisons with experimental results.
  • 笹尾 茂広, 島田 雅之, 泊 清隆, 喜多 泰夫, 上田 明, 原田 敏彦, 福田 明徳
    1998 年 47 巻 12 号 p. 1292-1295
    発行日: 1998/12/15
    公開日: 2009/06/03
    ジャーナル フリー
    We have synthesized a new block copolymer with poly (ethylene terephthalate) as the hard segment and poly olefine as the soft segment by the condensation of terephthaloyl chloride, hydrogenated α, ω-dihydroxy polybutadiene and ethylene glycol. This block copolymer was characterized by 1H and 13C NMR and FT-IR. Quantitative estimations of the contents of block segments have been carried out by 1H NMR. The effect of the addition of this block copolymer in PET/HDPE polymer blends was investigated.
  • 西岡 昭博, 高木 康行, 高橋 辰宏, 増渕 雄一, 滝本 淳一, 小山 清人
    1998 年 47 巻 12 号 p. 1296-1300
    発行日: 1998/12/15
    公開日: 2009/06/03
    ジャーナル フリー
    Biaxial elongational rheometer using lubricated squeezing method has been installed. To start up the rheometer and to obtain reproducible and reliable data, the effects of experimental conditions on biaxial elongational viscosity data were investigated. Constant area method was preferable rather than constant volume method. It was concluded that the effects of the viscosity of silicone oil and the shape were neglisible when method of constant area was employed.
  • 2. ミクロ応力とマクロ応力
    田中 啓介, 秋庭 義明
    1998 年 47 巻 12 号 p. 1301-1307
    発行日: 1998/12/15
    公開日: 2009/06/03
    ジャーナル フリー
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