材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
63 巻 , 2 号
選択された号の論文の23件中1~23を表示しています
特集 信頼性工学
巻頭言
論文
  • 兼清 泰明
    2014 年 63 巻 2 号 p. 92-97
    発行日: 2014/02/15
    公開日: 2014/02/20
    ジャーナル フリー
    A probabilistic model describing random fatigue crack growth is newly proposed, in which a stochastic differential equation driven by a temporally inhomogeneous compound Poisson process is applied. The new model has several outstanding features such as (i) we can perfectly remove the probability that a crack length decreases in the process of fatigue failure and (ii) an analytical approach is possible for obtaining probabilistic properties associated with the crack growth process. The former feature gives a quite effective solution over a critical disadvantage point inherent in the so-called diffusive model which has been widely used for describing the random fatigue crack growth.
    First, the well-known Paris-Erdogan law is extended to a stochastic differential equation by introducing a temporally inhomogeneous compound Poisson process expressing the random behavior of crack propagation resistance. Next, its solution process is analytically derived by the use of the generalized Ito formula and probabilistic properties associated with the random fatigue crack growth process are also clarified. Finally, some numerical examples are given so that we can quantitatively clarify sample behavior of the crack growth and temporal variation of a probability distribution of a crack length.
  • 中川 雅央, 中易 秀敏, 三好 哲也
    2014 年 63 巻 2 号 p. 98-103
    発行日: 2014/02/15
    公開日: 2014/02/20
    ジャーナル フリー
    A skill is important factor integrate technology of machine and technique of human. These determine the quality level of the defect inspection process. Panels with advanced skills, have an ability to perform the actions that meet state and powers of observation to work on, the state of the work object. An important sense is concerned with a perceptual and cognitive ability. It should hurry to develop a method to quantitatively assess the characteristics of human perception. In this paper, in defect detection experimental evaluation of panels based on the inspection image for fracture surface of metallic materials, we focus on the relationship of non-defective rejection probability and defect detection probability from the probabilistic model based on signal detection theory, for the characterization of panels Experiments were carried out to calculate the metrics according to the skill level of panels that conform to the flow of international standardization in recent years. Perception of the panel, is represented by ROC curve, skill levels showed that the degree of knowledge and experience can be categorized quantitatively.
  • 白木 渡, 井面 仁志, 松島 学, 福本 直也
    2014 年 63 巻 2 号 p. 104-109
    発行日: 2014/02/15
    公開日: 2014/02/20
    ジャーナル フリー
    The maintenance of structures must be carried out periodically according to the performance degradation. The change of performance of structural system happens with multiple states including partial failures according to the passage of time. Such a system is known as a MSS (Multi-state system). Taking account of the appropriate maintenance of a MSS structural system with performance degradation, the reliability evaluation approach considering the time series MSS should be used.
    In this study, an optimization approach of repair plan of RC slab of piled pier is proposed by the reliability evaluation method of time series MSS. Specifically, the performance degradation due to salt damage is considered and modeled by a time series MSS, and some optimal maintenance approaches proposed. Simultaneously, under the limit condition of a reliability evaluation index or the total repair expense, the safety and life cycle cost of the repair plan were compared using repair expense and a reliability assessment result. The costs of repairs are calculated and repair plans can be optimized.
  • 高橋 和也, 藤井 久矢, 古田 均, 堂垣 正博
    2014 年 63 巻 2 号 p. 110-116
    発行日: 2014/02/15
    公開日: 2014/02/20
    ジャーナル フリー
    In this paper, the maintenance management is described for the existing and aging RC bridge piers. The maintenance scenarios of aging and deteriorating RC bridge piers are considered based on various repairing methods. The life-cycle cost analysis is carried out, including the seismic risk under unexpected large earthquake. If the aging and deteriorating RC bridge piers are not maintained effectively, their seismic performance decreases, and the seismic risk increases. The life-cycle cost analysis with the seismic risk leads to the efficient maintenance plan of RC bridge piers.
  • 木野村 宏昭, 堂垣 正博
    2014 年 63 巻 2 号 p. 117-124
    発行日: 2014/02/15
    公開日: 2014/02/20
    ジャーナル フリー
    The present paper describes the damage state and redundancy of steel piers sustaining highway bridges under specified design or unexpected earthquake strength, in which the redundancy is the index measuring the safety level introduced to clear their seismic performance. This is given by the ratio of the standard lateral seismic coefficient corresponding to the earthquake load coinciding with the horizontal capacity to that coded by the Japanese Specifications for Highway Bridges. The damage state and redundancy of steel bridge piers are determined by using their characteristics obtained by the elastic-plastic finite displacement analysis. This analysis is carried out by the general purpose finite element program MARC2012.10. As a result, it is defined what damage state a bridge pier would fall if the unexpected earthquake hits, by the equal-energy approach. The evaluation index is used, given by a combination of the horizontal capacity and horizontal displacement.
  • 池田 健人, 倉敷 哲生
    2014 年 63 巻 2 号 p. 125-130
    発行日: 2014/02/15
    公開日: 2014/02/20
    ジャーナル フリー
    Recently, Risk-Based Maintenance (RBM) methodology has been used for managing the overall risk of fixed equipment in the petrochemical and chemical process plants. The risk is obtained by multiplying the probability of failure and the consequence of failure. In this paper, the simulation technique of gas diffusion was proposed due to evaluate the consequence with considering the effect of water curtain. Firstly, we calculated the coefficient of wash-out by water curtain, and estimated the gas diffusion with considering the virtual sources due to the wet deposition. The relation between the diffused area and the number of nozzles of water curtains can be estimated by the proposed method. Furthermore, the estimation method of gas diffusion considering the effects of aspirate and dry deposition was proposed. From the numerical results, the proposed technique is useful for an evaluation of consequence of failure in petrochemical plants considering mitigation.
  • 山中 稔, 豊田 尚也, 野々村 敦子, 長谷川 修一
    2014 年 63 巻 2 号 p. 131-136
    発行日: 2014/02/15
    公開日: 2014/02/20
    ジャーナル フリー
    The 2011 off the Pacific coast of Tohoku Earthquake caused widespread serious damage. Particularly a huge amount of disaster wastes was generated along coastline areas of the Tohoku region by tsunami during the Tohoku Earthquake. It is very important to estimate amount of tsunami disaster wastes as for quick recover and revival of damaged areas in advance. Since a tsunami height in Shikoku region during next Tounankai-Nankai Earthquake will be larger than a height of the Tohoku Earthquake, it can be anticipated easily that an amount of disaster wastes in Shikoku districts will very large also.
    In this paper, it was described some factors of Tsunami disaster wastes generated by 2011 off the Pacific coast of Tohoku Earthquake. And it can be cleared that there is good relationship between a damage level of household and a tsunami depth at that point, and it was calculated per unit generation of tsunami disaster wastes in accuracy. And more it was estimated the amount of tsunami disaster wastes and the number of submerged households in Shikoku districts by supposed tsunami during Tounankai-Nankai Earthquake using GIS.
  • 井面 仁志, 白木 渡, 松原 雄三, 長谷川 修一, 野々村 敦子
    2014 年 63 巻 2 号 p. 137-142
    発行日: 2014/02/15
    公開日: 2014/02/20
    ジャーナル フリー
    People's awareness of disaster prevention has risen, after the Great East Japan Earthquake. In local communities, the decision of the disaster prevention plan is pushed forward. In the first step, the evacuation plan is considered, however there are various limitations on-the-job training with a lot of residents' participation. Especially, it is impossible to take account of disaster conditions such as the collapses of the liquefaction, the collapses of the block wall and the collapses of the wooden house etc. in normal circumstances.
    In this study, an evacuation simulation system with tsunami and high tide disaster prediction is developed, and using this developed simulation system damage situations in a local community are estimated. The data base system based on the simulation results is developed in order to make effective use for evacuation for a variety of disaster situations. A costal area in Takamatsu City is selected, and some evacuation plans reflecting the disasters situations obtained by the simulation data base are made and examined.
  • 石橋 健, 古田 均, 野村 泰稔, 中津 功一朗, 高橋 亨輔
    2014 年 63 巻 2 号 p. 143-148
    発行日: 2014/02/15
    公開日: 2014/02/20
    ジャーナル フリー
    The reliability analysis is necessary to maintain the safety of structure. In order to evaluate the soundness of structure quantitatively, the calculation of failure probability is one of useful measures. In the reliability analysis for large-scale structures, the enhancement of calculation accuracy and the estimation of factors for the failure require the failure probability calculated by considering the various failure modes. However, the sampling method like Monte Carlo simulation is difficult to calculate the failure probability and estimate multiple failure modes efficiently. This is because the search of various failure modes increases the calculation cost significantly. Therefore, in order to overcome the trade-off, this paper attempts to propose an efficient method by applying Metaheuristic methods. Metaheuristic methods are characterized by the high search ability with keeping the diversity among solution candidates. Firstly, the search of failure modes is formulated as the combinatorial optimization. In this optimization, the metaheuristic method searches failure modes in consideration of the occurrence probability of minimal cut set. In this way, various failure modes that have high occurrence probability are obtained efficiently. Secondly, Probabilistic Network Evaluation Techniques (PNET) is applied to calculate the failure probability of network in consideration of the correlation among obtained failure modes. Through these processes, the proposed method can calculate the accurate failure probability efficiently. Several numerical experiments are presented to demonstrate the applicability of the proposed method for the reliability analysis of large-scale networks.
  • 堀田 源治, 兼竹 望, 西村 太志, 大渕 慶史, 坂本 英俊
    2014 年 63 巻 2 号 p. 149-153
    発行日: 2014/02/15
    公開日: 2014/02/20
    ジャーナル フリー
    It is an important matter to decrease the mean time to repair (MTTR) for the improvement in the reliability of machinery. When factory workers repair as infrequent operations, they usually don't have a service manual. Therefore, the quality of repair is dependence on the skills of maintenance engineers or machine operators. In maintenance planning, repairs as infrequent operations have a tendency to depend on skilled workers. However, in the case of infrequent operations, there is not always correlation between the experience of maintenance engineers and the decrease of MTTR or repair time. This is an important problem in the optimum maintenance planning. And the industrial world desires the analysis of the human factor which affects the reliability of machinery. In this research, we turn into a model the actions for coping with the failures of maintenance engineers, and analyze the human factor which affects the reliability of machinery. In addition, we consider the improvement in the reliability of machinery by the reduction of MTTR or the repair time. However, in infrequent operations, there is not always a correlation between the experience of maintenance engineers and the reduction of MTTR or repair time.
特集 分子動力学
論文
  • 屋代 如月, 西村 英晃
    2014 年 63 巻 2 号 p. 155-162
    発行日: 2014/02/15
    公開日: 2014/02/20
    ジャーナル フリー
    For a new insight on solid lubricant of fullerenes and onion-like carbons (OLCs), we have performed scratch simulations on isolated fullerenes/OLCs and monolayer film of their array. Here, molecular dynamics simulation may overestimate bond-forming between the scratch surface and target carbons, so that we consider only the van der Waals interaction between the rigid diamond and fullerenes/OLCs. On this condition, both the isolated/layered fullerenes/OLCs doesn't show rotation but slip on the perfect (001) diamond surface, showing frictional coefficient lower than μ=0.05. On the other hand, the fullerenes/OLCs show rotation and higher frictional coefficients of μ=0.1∼0.3, if we set surface roughness on both scratch walls. In this rotational friction, larger fullerenes/OLCs show smaller frictional coefficients, and the fullerenes shows higher frictional coefficient than OLCs of same size.
  • 西村 憲治
    2014 年 63 巻 2 号 p. 163-167
    発行日: 2014/02/15
    公開日: 2014/02/20
    ジャーナル フリー
    The characteristics of hydrogen diffusion in palladium such as the influences of temperature, hydrostatic pressure, pure shear, and lattice defect are investigated using molecular dynamics simulation. The simulations predict Arrhenius-type temperature dependence of the hydrogen diffusion in palladium. The diffusion activation energy is found to be 0.16 eV, in excellent agreement with value obtained by means of the first principle calculation. The calculated activation energy with zero-point energy corrections is consistent with reported experimental data. Furthermore, we find that the hydrogen diffusivity in palladium decreases with increasing the hydrostatic pressure in a system, especially this pressure dependence is larger in case of low temperature, and the pure shear applied to the system has little influence on the hydrogen diffusivity. In addition, the hydrogen diffusivity dramatically decreases with increasing defect density because the lattice defect acts as trap sites.
  • 有末 紘, 嶋田 隆広, 北村 隆行
    2014 年 63 巻 2 号 p. 168-173
    発行日: 2014/02/15
    公開日: 2014/02/20
    ジャーナル フリー
    The intrinsic coupling between ferroelectricity and ferromagnetism in multiferroic BiFeO3 is studied using first-principles density-functional theory calculations. The spontaneous polarization in multiferroic BiFeO3 is found to be smaller than that in a pure ferroelectric phase which can be obtained by eliminating ferromagnetism artificially, while the total magnetic moment in multiferroic BiFeO3 is lower than that in a pure ferromagnetic phase in which ferroelectric distortions are artificially frozen out. These results clearly show the competing interaction between ferroelectricity and ferromagnetism in BiFeO3. We further demonstrate that this competing nature in BiFeO3 plays an important role under external loads: The polarization increases and the total magnetic moment conversely decreases with respect to uniaxial tensile strain along the [111] direction. The polarization and the total magnetic moment change in the opposite way under compressive strain. These results indicate that ferroelectricity and ferromagnetism show opposite strain response with each other. This arises from the mutual charge transfer between the [101]-and [101]-directed Bi-O bonds.
  • 福田 忠生, 小武内 清貴, 尾崎 公一, 北浦 宏将, 田辺 晃弘
    2014 年 63 巻 2 号 p. 174-181
    発行日: 2014/02/15
    公開日: 2014/02/20
    ジャーナル フリー
    In this study, two types of first-principles calculation models were prepared to investigate the H-atom behavior in an Al-Mg-Zn series alloy and its hydrogen embrittlement characteristics. The first calculation model, which represented a perfect crystal, was used to evaluate the Mg- and Zn-atom behavior in Al crystals. To determine the H-atom behavior in Al crystals, the formation energy and diffusion barrier of H atoms in Al crystals were also calculated. The calculation results showed that Mg and Zn atoms might have formed compounds and dissolved in Al crystals. The diffusion barrier of H atom near Zn and Mg atoms was higher than that in an ideal Al crystal. These results suggested that the H-atom absorption ability of the Al-Mg-Zn series alloy was higher than that of pure Al. The second calculation model, which consisted of two crystals, was prepared to determine the effect of H atoms near the Σ3{111} grain boundary on the embrittlement characteristics of the Al-Mg-Zn series alloy. The total energy change was investigated to evaluate the stress required to separate the grain boundary. The calculation results showed that the maximum stress required to separate the grain boundary was significantly decreased when H atoms existed near a Mg-Zn compound formed at the grain boundary. In addition, decrease ratio of grain boundary cohesive energy was about 10% when H atoms existed near a Mg-Zn compound formed at the grain boundary. These results revealed that the Al-Mg-Zn series alloy showed lower hydrogen embrittlement properties than that shown by pure Al.
  • 松本 龍介, 西口 直, 武富 紳也, 宮崎 則幸
    2014 年 63 巻 2 号 p. 182-187
    発行日: 2014/02/15
    公開日: 2014/02/20
    ジャーナル フリー
    Hydrogen embrittlement is a well-known phenomenon in which hydrogen lowers the strength of materials. Despite extensive investigations, the role of hydrogen in materials remains unclear. Recently, Nagumo proposed the hydrogen-enhanced strain-induced vacancy model, which explains the reduction in the ductility of metals due to a significant increase in the vacancy concentration resulting from plastic deformation in a hydrogen environment. In the present study, we first estimated the interaction energy between hydrogen atoms and an atomic vacancy in alpha iron by applying density functional theory. We then estimated the mobility of an atomic vacancy in a hydrogen environment by calculating the activation energy for diffusion using the climbing image nudged elastic band method. These analyses showed that two hydrogen atoms are trapped by an atomic vacancy under a practical hydrogen gaseous environment (T = 300 K and p = 70 MPa). A reduction in the vacancy formation energy from 2.14 to 1.68 eV and an increase in the activation energy for vacancy diffusion from 0.62 to 1.07 eV by the hydrogen atoms were also observed. Jog dragging by a screw dislocation under shear stress was believed to be the mechanism for vacancy multiplication due to plastic deformation. Using the hydrogen-affected physical properties, we determined the vacancy distribution behind a jog moving at a constant velocity. This analysis suggested that supersaturated vacancies locally accumulate during plastic deformation in hydrogen environments.
  • 松原 和輝, 君塚 肇, 尾方 成信
    2014 年 63 巻 2 号 p. 188-193
    発行日: 2014/02/15
    公開日: 2014/02/20
    ジャーナル フリー
    The temperature dependence of thermal expansion of hexagonal close-packed Mg was analyzed based on the quasi-harmonic approximation (QHA) using first-principles density functional theory calculations. To consider the structural anisotropy of a Mg single crystal, we introduced two individual structural parameters into the QHA scheme so that static total energy and lattice vibration frequencies of the system were numerically described by the approximate polynomials as a function of the lattice parameters a and c. We found that our approach can successfully reproduce the thermal expansion behavior of Mg over the wide temperature range by adopting the second- and higher-order polynomial to describe the lattice vibration, in a manner consistent with the experimental measurements. The nonlinear dependence of the lattice vibration frequencies on the axial strain was suggested to play an important role in understanding the thermal expansion anisotropy due to the anharmonicity in the interatomic interactions.
  • 浦長瀬 正幸, 神垣 沙奈, 松本 龍介
    2014 年 63 巻 2 号 p. 194-199
    発行日: 2014/02/15
    公開日: 2014/02/20
    ジャーナル フリー
    We performed atomistic simulations to demonstrate the nucleation of a dislocation loop for the basal and prismatic slips of a magnesium single crystal. The dislocation loop was successfully simulated by employing the constrained molecular dynamics method, which involves constraining the atomic motion above and below the activation site, keeping the distance between the domain centers constant in the slip direction. Then, the activation free energy for nucleation of a dislocation loop was evaluated using the thermodynamic integration method and the dependence of this nucleation on the ambient temperature and applied shear stress was studied. Moreover, we compared the activation free energy of nucleation from a free surface to that of homogeneous nucleation in order to investigate the effect of inhomogeneity on the activation free energy.
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