材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
64 巻 , 3 号
選択された号の論文の21件中1~21を表示しています
特集 金属ガラス
総説
  • 春山 修身, 澤田 裕幸, 辻村 浩太郎
    2015 年 64 巻 3 号 p. 149-155
    発行日: 2015/03/15
    公開日: 2015/03/20
    ジャーナル フリー
    Low temperature structural relaxation in Zr55Cu30Ni5Al10 bulk metallic glass (BMG) that evolved at about 100~150 K under glass transition temperature was investigated by electrical resistance relaxation and volume relaxation. The reversible isochronal change in resistance and the kinetics of relaxation was in agreement with low temperature relaxation behavior previously reported in many amorphous metals. It was checked whether or not the kinetic of relaxation examined obeys kinematical criterions deduced from dynamic mechanical analysis for non-organic glass, polymer glass as well as metallic glass. At least, with regard to a limited glass as pre-annealed Zr55Cu30Ni5Al10 BMG, the equivalency of low temperature relaxation to β-relaxation (Johari-Goldstein relaxation) was not verified.
論文
  • 譯田 真人, 渋谷 陽二, 尾方 成信
    2015 年 64 巻 3 号 p. 156-162
    発行日: 2015/03/15
    公開日: 2015/03/20
    ジャーナル フリー
    Amorphous metals have excellent properties, such as large elastic elongation, high fracture toughness and high corrosion resistance. These properties may arise from their disordered atomic structures, which are totally different from the crystalline structures with long-range periodic order. However, detailed structure of amorphous metals is still a controversial issue, because the experimental diffraction methods have a difficulty to reveal detailed structural features of amorphous metals. Using molecular dynamics methods with binary Lennard-Jones Cu-Zr interatomic potentials, we in this study investigated topological feature of amorphous metals focusing on a medium-range order (MRO). We conducted melt-quenching simulations and constructed amorphous alloy models with three different Cu concentrations. MRO clustering of icosahedra structures which consist of interpenetrating icosahedra links were found in a constructed amorphous structure. In the amorphous model, there are many small and a few large MRO clusters, and the number of MRO clusters monotonically decreases with increasing its size. During the melt-quenching process, the size of MRO cluster rapidly increases with increasing the number of icosahedra at around the glass transition temperature Tg. It is implied that the rapid increase of the size of MRO cluster is caused by a clustering between MRO clusters as well as a growth of each MRO cluster. An amorphous model with more icosahedral clusters tends to have larger, denser and more MRO clusters, and a maximum size of the icosahedral MRO cluster is ~4nm. Based on both the radius of gyration and the density correlation function analyses, we found that the size of icosahedral MRO cluster has fractal feature, of which fractal dimension are 1.46~1.80.
  • 垂水 竜一, 譯田 真人, 渋谷 陽二
    2015 年 64 巻 3 号 p. 163-168
    発行日: 2015/03/15
    公開日: 2015/03/20
    ジャーナル フリー
    We conducted molecular dynamics (MD) simulation on simple shear deformation of Cu-Zr metallic glass. A metallic glass model is prepared by rapid quench from an equilibrium melting state. Shear deformation process is simulated by applying stepwise affine-displacement which is followed by structural relaxation for a certain time interval. Present MD simulation demonstrated typical deformation behavior of metallic glasses including elastic response, yielding and nucleation and growth of shear bands in the atomistic scale. To obtain a course-grained picture of the deformation, we transformed the atomistic relative displacements into a continuously differentiable field using the Gauss-type radial basis function (RBF). This analysis revealed that local structural relaxation and their percolation play a dominant role on the formation of shear band. We also revealed that source and sink of divergence of the displacement velocity have a side-by-side configuration due to accommodative motion for relaxation. These results indicate that the continuous field transformation by RBF is effective to understand the plastic deformation mechanism of metallic glasses.
  • 渋谷 陽二, 岡崎 貴弘, 吉川 高正, 垂水 竜一
    2015 年 64 巻 3 号 p. 169-174
    発行日: 2015/03/15
    公開日: 2015/03/20
    ジャーナル フリー
    Viscous flow property of bulk metallic glasses (BMGes) at the supercooled liquid temperature range has already been applied to the practical net shape forming. At the higher temperature over 0.9Tg (Tg is the glass transition temperature of BMG), the Young’s modulus and yield stress of BMG drastically decrease, meanwhile the elongation reaches 40~50%. Thus, the hot working at this temperature range is much possible to be used for the plastic molding with the higher precision. The tensile tests of BMGes at such a high temperature report that the stress overshoots after the elastic limit and gradually decreases until the saturated plastic flowing, which is sensitive to the temperature and strain rate. The present study aims to investigate the plastic deformation behaviors of the initial yielding condition and the cyclic plastic hardening property related to the subsequent yielding condition at the high temperature using elastic-plastic Finite Element Method with the mean stress dependence and the defects density evolution law. The initial yielding can be well predicted by using Drucker-Prager yield criterion with the mean stress dependence parameter of κ=0.09 and the elastic limit as the yield stress of Zr-base BMG. The kinematic hardening by Prager-type back stress under cyclic uniaxial compressive and tensile loadings changes the stress overshoot behaviors. The defects density is accumulated at the reversed strain and is diminished at the zero strain. The plastic flow under the cyclic uniaxial compression is represented by the zero balance between the defects density nucleation and annihilation rates.
  • 永瀬 丈嗣, 鈴木 賢紀, 田中 敏宏
    2015 年 64 巻 3 号 p. 175-182
    発行日: 2015/03/15
    公開日: 2015/03/20
    ジャーナル フリー
    Microstructure of rapidly solidified melt-spun ribbons in Fe-M-Si-B (M=Cu, Ag, Sn) immiscible alloys were investigated focusing on an amorphous phase formation and the difference in microstructure between Fe-Cu-based and Fe-Ag-based alloys. Amorphous phase was formed in melt-spun ribbon of Fe-Cu-Si-B and Fe-Ag-Si-B alloys, while a Fe-Sn-Si-B alloy shows low glass forming ability resulting in the formation of a crystalline melt-spun ribbon.
特集 信頼性工学
巻頭言
論文
  • 兼清 泰明
    2015 年 64 巻 3 号 p. 184-189
    発行日: 2015/03/15
    公開日: 2015/03/20
    ジャーナル フリー
    A fast Monte Carlo simulation scheme is newly developed for reliability analyses based upon a probabilistic model describing random fatigue crack growth driven by a noise of Poisson type. The proposed simulation scheme is based upon a probability measure transformation available for Lévy processes, which realizes an importance sampling principle so that very small probability of failure can be accurately estimated with small size of generated samples. First, a random differential equation is formulated for describing random fatigue crack growth by introducing a temporally inhomogeneous compound Poisson process as a driving noise. Next, a probability measure transformation for temporally homogeneous compound Poisson processes is applied to the random fatigue crack growth model by the use of a transformation technique of a time variable, which leads to a Monte Carlo simulation scheme realizing the importance sampling principle. Finally, through some numerical examples, it is clarified that the proposed simulation scheme can give accurate estimations for probability of fatigue failure with quite small sample size.
  • 石橋 健, 古田 均, 野村 泰稔, 中津 功一朗, 高橋 亨輔
    2015 年 64 巻 3 号 p. 190-195
    発行日: 2015/03/15
    公開日: 2015/03/20
    ジャーナル フリー
    The purpose of this paper is to propose a method effective for the structural reliability assessment based on the multimodal analysis. A structure should be evaluated from various perspectives in order to improve the safety against unpredictable crises. Factors related to failure modes and elements contributing to the capability are estimated based on each criterion. Thus, by considering these criteria as modes, the multimodal analysis can extract information effective to the improvement of reliability and the rational preparedness. However, because this analysis requires enormous samples in practical problems, it is difficult to apply sampling methods like Monte Carlo simulation. In this paper, an attempt is made to propose a search method of samples feasible to the multimodal analysis by using Cellular Automaton Particle Swarm Optimization. A numerical example with a single-bay and single-story rigid frame structure is presented to demonstrate the applicability of the proposed method.
  • 原田 泰男, 倉敷 哲生
    2015 年 64 巻 3 号 p. 196-202
    発行日: 2015/03/15
    公開日: 2015/03/20
    ジャーナル フリー
    In this paper, we focus the failure rate of components which compose of products and are the dominant cause of unsafe incidents of the product. We analyzed data base of NITE reports to figure out component failure rate through electric fan incident cases. The failure rate resides in accidental failure mode and wear-out failure mode. We propose a method to derive an equivalent distribution of probability of failure rate by using the limited number of incident case samples. Failure rates at a certain time is shifted to an observation time, we derive the distribution of probability of failure rate data using shifted data to the observation time where we defined the distribution as equivalent distribution of probability of at the observation time. Assuming that the probability distribution can be identical at the crossing point of accidental mode and wear-out mode, we compare the failure rate distributions at the crossing point between accidental failure mode and wear-out failure mode and choose the crossing point based on its correlation. After setting crossing point, we estimate the all equivalent failure rate data from both failure modes comparing its distribution to Normal, Weibull, and Log-normal, and decide the Weibull distribution as the equivalent failure rate distribution with the highest correlation coefficient. Furthermore, we apply the probability distribution to the failure rate calculated by the definition of IEC/TR62380 and find that the probability of failure rate for a standard environment is 50% and severer environment failure rate becomes 69.5% of probability. As we apply the distribution function of failure rate given by the field data to IEC/TR62380 mathematical model, we can set standard criteria of the failure rate using IEC/TR62380 and adjust criteria according to the environment of product usage at setting the risk level for a manufacturing management system.
  • 高橋 利恵, 堤 洋樹, 中島 正夫, 三田村 輝章
    2015 年 64 巻 3 号 p. 203-208
    発行日: 2015/03/15
    公開日: 2015/03/20
    ジャーナル フリー
    For minimizing the effects of housing deterioration, it must be established a simple and precise inspection to examine the house condition. In this study, the behavior of humidity in wooden sheathed wall of housing outer wall was considered. The humidity, which was observed in the walls, was compared with non-destructive inspection data, the temperature and the humidity observed inside and outside of the wall. Non-destructive inspection data was classified and inspected according to their observed position, their specification and environment. As a result, the boundary of the humidity in the wall, which has effect on the housing deterioration, was estimated from 64% to 67%. The reliability of non-destructive inspection method was indicated by Bayes method, therefore the humidity inspection with electrical resistance devices is more reliable than the inspection with high frequency devices. With the electrical resistance devices, the non-destructive inspection on lower position mortar wall is useful on the humidity inspection in wooden sheathed walls. The humidity in the wall is affected by the environment, specification and the observed position.
  • 稲積 真哉, 眞鍋 磨弥, 境田 彰芳
    2015 年 64 巻 3 号 p. 209-214
    発行日: 2015/03/15
    公開日: 2015/03/20
    ジャーナル フリー
    In Japan, the government reinforces the environmental regulation and people worry about the environmental stability of waste landfill, so the site of landfill is diversified from inland to coast near urban areas. However, as the standard of the environmental stability and the monitoring procedure are not established, the coastal landfills have been built and used without a long-term evaluation of the performance. Therefore this study shows the methods of evaluations for the impervious walls that prevent leakage of the waste exudation water. This study uses Weibull distribution such as statistical method. Furthermore, this study assumes that the environmental damages occur by the leakage through the defects.
  • 山﨑 恵理, 桜田 翔平, 中村 理恵, 合田 公一
    2015 年 64 巻 3 号 p. 215-222
    発行日: 2015/03/15
    公開日: 2015/03/20
    ジャーナル フリー
    Natural fibers are often used as a form of continuous twisted yarn, which are suitable for reinforcement of fibrous composites. In the twisted yarn, we often encounter phenomenon called ‘migration’, such that single yarns (spun yarns) shift from outer layer to inner and vice versa. Thus, we first observed migration structure of ramie twisted yarn through an X-ray CT scanner. Results show that migration occurred irregularly in the yarn, so this phenomenon was simulated by Markov chain model. In addition, the effect of migration on tensile properties was clarified. Although Markov chain model is not necessarily enough in predicting the migration occurrence probability, this model can predict well the state probabilities which single yarns exist in each zone after twisting. Finally, we found two structural parameters of twisted yarns which can be correlated with tensile strength. First parameter, i.e. the number of migration existing in a twisted yarn, had a weak correlation, whereas second parameter, i.e. the number of single yarns causing migration, showed a stronger correlation.
  • 藤山 一成, 飯田 雄大, 齊藤 和宏
    2015 年 64 巻 3 号 p. 223-228
    発行日: 2015/03/15
    公開日: 2015/03/20
    ジャーナル フリー
    Bivariate log-normal distribution analyses were conducted on the specific output class of steam turbine components such as rotors, moving blades, nozzles, casings. The damage phenomena were erosion, creep deformation, fatigue cracking, wear, fouling, scoring and so on excluding the repeated events after repairs. Using the statistical parameters such as mean and variance, the events were plotted against operation time and start up cycles. The order of event occurrence was determined by the time-cycle based statistical data manipulation. The prescribed risk values for individual events could be easily transformed to the equi-risk ellipse contours of chi-square distribution of parameter Q as the quadratic function of operation and start-up cycles derived from the bivariate log-normal distribution on the cycle-time diagram. The expected values of total maintenance costs for repairing the individual damage were obtained by the sum of ellipse contours of respective damage modes in the subject components. This diagram could be a useful measure of expecting maintenance period to minimize the total cost by controlling operation patterns both considering start-up cycles and operation hours.
論文
  • 酒井 幸文, 吉田 加代子, 新居 敦史, 高井 智雄
    2015 年 64 巻 3 号 p. 229-234
    発行日: 2015/03/15
    公開日: 2015/03/20
    ジャーナル フリー
    We have developed a heat-transfer tube for use as a heat exchanger in waste gasification and melting systems. This heat-transfer tube, which is made of a pressureless-sintered silicon carbide material, is a single end-type with cantilever support. Ceramic heat-transfer tubes fixed both ends to a metallic heat exchanger body are easily broken, due to differences in thermal expansion at high temperatures, but silicon carbide tubes on a cantilever support do not have this problem. We measure basic properties of the heat-transfer tube such as the coefficient of heat transfer and corrosion resistance, and discuss ash removal. We conduct a low-temperature heat transfer experiment, using saturated steam at 0.4 MPa pressure as a heating medium, and actual exhaust gas from a waste gasification and melting system at about 1150 K as a high-temperature range. Air of 290 K, 79.2 m3[normal]/h reaches 820 K after two heat exchanger passes. Near the dew point, silicon carbide shows high corrosion resistance to the exhaust gas. Regarding ash removal, sandblasting effectively cleans the tube surface, because of hardness of a pressureless-sintered silicon carbide material. We simulate application of a large heat transfer tube, about φ200 × φ179 × 1800 mm, in a furnace. Results indicate that a heat transfer tube made of pressureless-sintered silicon carbide is suited to waste gasification and melting systems.
講座
国内外トピックス
会員便り
新技術・新製品トピックス
書評
feedback
Top