材料
Online ISSN : 1880-7488
Print ISSN : 0514-5163
ISSN-L : 0514-5163
52 巻 , 3 号
選択された号の論文の19件中1~19を表示しています
  • 2003 年 52 巻 3 号 p. 1
    発行日: 2003年
    公開日: 2009/06/03
    ジャーナル フリー
  • 梅野 宜崇, 北村 隆行, 松井 英史
    2003 年 52 巻 3 号 p. 219-224
    発行日: 2003/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Carbon nanotubes (CNT) are attracting attention by their prominent properties in terms of mechanics, electronics, and so on, and their application as new device materials are being attempted. In this study, in order to elucidate mechanical property of CNT from atomic level, tight-binding molecular dynamics simulations on tension of straight single wall CNT (Armchair and Zigzag types) are conducted. Both types have almost the same tensile stiffness under no load. While Zigzag type fractures at the tensile strain of 0.198, the fracture strain of Armchair type is 0.316, which means Armchair type is more ductile. The difference in mechanical properties is based on the deformation mechanism of six-membered rings in the CNTs.
  • 泉 聡志, 佐藤 裕輔, 原 祥太郎, 酒井 信介
    2003 年 52 巻 3 号 p. 225-230
    発行日: 2003/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    In order to investigate the reaction probability of silane dissociative adsorption, we developed a new Si-H potential which reproduces the energy and vibration wave number of silicon clusters as well as the activation energy of silane dissociative adsorption. By using molecular dynamics with our potential, the dependence of the reaction probability on the molecular and substrate temperatures was investigated and was compared with the translationally activated process.
    Reaction probability increases almost linearly with increased translation energy. The dependence on vibration energy can be approximated by the quadratic curve, that is, the gradient increases with the increase in energy. The effect of the rotational energy is small. The dependence on the substrate temperature qualitatively agreed with the experiment, however, our calculations showed linearity for the dependence on the translation energy, while the experiment showed an exponential function. This is attributed to the dependence on impact angle and differences in the potential surface shape.
  • 泉 聡志, 原 祥太郎, 酒井 信介
    2003 年 52 巻 3 号 p. 231-234
    発行日: 2003/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Surface energy and surface stress is a key parameter for predicting of the intrinsic stress of thin film. We have evaluated the statistical properties of the surface energy and the surface stress of amorphous silicon by using molecular dynamics, and obtained values of 1.44±0.03J/m2 and -0.48±0.06N/m respectively for 67nm2 surface area. Since it has been determined that dispersion shows a normal distribution, that of an area of any size can be predicted by the central limit theory. The coefficients of variation in an area of 1nm2 are 20.1% and 108.3%, respectively. It is found that the dispersion of surface stress is significantly large. For applications in the continuum mechanics, the surface stress can be treated as the initial stress generated in a surface region with a thickness of about 0.4nm. Though the elastic constants are decreased due to the surface effect, the difference of the strain is only about 7% for a film with 3.8nm thickness. The surface stress is strongly dependent on the reconstruction of the surface atoms. The contribution of surface reconstruction of amorphous silicon is larger than that of Si (100) 1×1 surface.
  • 松本 龍介, 北川 浩, 中谷 彰宏
    2003 年 52 巻 3 号 p. 235-240
    発行日: 2003/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    A large-scale molecular dynamics simulation is performed to obtain fundamental knowledge of deformation-induced nanocrystallization in an amorphous metal. The Finnis-Sinclair potential is adopted to represent α-iron. The model amorphous metal is created by a heating-rapid quenching simulation. Tensile deformation is applied to the amorphous block with 512 026 atoms. The initial temperature is 300K. As it is deformed severely, a lot of nucleationsites of crystal-clusters are observed around the shear bands which develop in the direction of about 45 degrees from tensile direction. The nucleation temperature of crystal is about 1200K which is about a half of glass transition temperature. The average distance between any two nucleation sites is about 6nm. Those clusters grow up rapidly until they strike each other. In the process, deformation is localized at the remaining amorphous phase, because the grains are rarely deformed. Some large grains grow bigger by absorbing small grains, therefore the total number of grains decreases. After the nanocrystallization, deformation twins are observed in some grains. At the final stage of deformation, a void is nucleated at a grain boundary. The crystalphase develops by latent heat of crystallization even after a break. Dislocations which are packed in the grain are moved out to the grain boundary or amorphous phase immediately. Grains whose (111) directions turn on the tensile direction are rarely nucleated. Some grains have long shape, because they nucleate beside the shear bands and grow toward low temperature regions.
  • 屋代 如月, 大穂 正史, 山上 勝也, 冨田 佳宏
    2003 年 52 巻 3 号 p. 241-246
    発行日: 2003/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Recent rapid progress in computers has made it possible to elucidate not only static atomic structure but also mechanical properties such as theoretical strength by using the ab-initio molecular dynamics. The theoretical strength, however, is evaluated on the assumption that crystals deform in a definite deformation path because of computational limitation, so that it is necessary to clarify the relationship between the theoretical strength and bifurcation criteria to the other deformation path. The lattice instability analysis based on the classical interatomic potentials has suggested that the bifurcation to the anisotropic transverse contraction becomes more important than the theoretical tensile strength in the uniaxial [001] tension. In this study, the bifurcation point under tension is investigated by means of ab-initio molecular dynamics. Si and Al single crystals are subjected to the uniaxial [001] tension under isotropic and anisotropic transverse contractions. The difference in energy shows that the deformation path of isotropic Poisson's contraction would bifurcate to anisotropic contraction at εzz=0.093 and εzz=0.051 for Si and Al, respectively, while the theoretical strengths under isotropic contractions reach εzz=0.25(Si) and εzz=0.18 (Al). Then the lattice instability at these bifurcation points is investigated on the basis of the positive definiteness of the elastic stiffness coefficients. It is shown that the positiveness is violated after the bifurcation point and the instability is caused by the negativeness of the minor determinants of the stiffness matrix, which represents the compliance against the anisotropic transverse contractions.
  • 荻原 律, 濱島 良吉, 元島 三明
    2003 年 52 巻 3 号 p. 247-252
    発行日: 2003/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Monitoring internal deformation and fracture of three-dimensional crystal structures under three-dimensional stress is very important. However, observing these phenomena solely by laboratory experiment is difficult. Several experimental results are available, but they are insufficient, since only the surfaces of the crystal structures could be observed. In an effort to obtain data beyond the limitations of laboratory experiment, we have been pursuing the development of computational simulation. This system enables us to analyze internal deformation and fracture of three-dimensional crystal structures with flaking and slipping on crystal grain boundaries. During this process we discovered the lack of useful visualization software, which is vital in evaluating the computational simulation results. In the present study we succeeded in developing visualization software which enables us to display and analyze internal deformation and fracture with flaking and slipping on crystal grain boundaries in an arbitrary cross section of three-dimensional crystal structures. The software development environment that we used is Direct3D “Retained Mode” in Microsoft DirectX7.
  • 西村 憲治, 宮崎 則幸
    2003 年 52 巻 3 号 p. 253-259
    発行日: 2003/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    The mechanical behaviors around a crack tip for a system including both a crack and two tilt grain boundaries under cyclic loading are examined using a molecular dynamics simulation. The grain boundary, whose direction of the axis of misorientation angle is ‹110› and whose plane is {112}, is considered in this simulation. This grain boundary has the lowest grain boundary energy among all tilt grain boundaries. The Johnson potential for α-Fe is used in the analysis to describe interaction between atoms. Not only a structural transition from bcc to hcp but also ductile deformation occurs around the crack tip during the first loading in order to relax stress concentration. Edge dislocations emitted from the crack tip are observed and they move to the ‹111› direction on the {112} plane, which is a slip system of α-Fe. Then, two dislocation pile-ups near the grain boundaries are formed after the edge dislocations reach the grain boundaries, because they cannot move beyond the grain boundaries. Alternating slipping-off occurs at the crack tip because of the emission of the edge dislocations. During the first unloading, the edge dislocations emitted from the crack tip return to the crack tip and disappear in the system. Then, twin deformation occurs from the crack tip and expands along the slip direction until it reaches the grain boundary. We observe that not only the crack does not propagate in the cleavage plane of α-Fe but also several vacancies are generated along the slip direction from the crack tip during cyclic loading. Conclusively, we suggest the fatigue crack growth mechanism for the initial phase of the fatigue fracture. That is, the fatigue crack propagates along the slip direction due to coalescence between the crack and vacancies which are caused by the emission and absorption of the dislocations and the twin deformation around the crack tip.
  • 香山 正憲, 田中 真悟, 岡崎 一行
    2003 年 52 巻 3 号 p. 260-265
    発行日: 2003/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    In the first-principles molecular-dynamics method using the ab initio pseudopotential method based on the density-functional theory, algorithms such as Car-Parrinello or conjugate-gradient schemes to obtain efficiently the electronic ground state are of primary importance. We have examined one of such algorithms, the RMM-DIIS (residual minimization/direct inversion in the iterative subspace) method, originally proposed by Pulay and recently implemented by Kresse and Furthmüller. This method is more suitable for parallel computations with respect to each wave function. We have developed the program using the RMM-DIIS method, and found that the RMM-DIIS method is quite effective especially for transition-metal large systems where the other schemes suffer very slow convergence.
  • 2003 年 52 巻 3 号 p. 267-272
    発行日: 2003/03/15
    公開日: 2009/06/03
    ジャーナル フリー
  • 中崎 一之, 井上 達雄
    2003 年 52 巻 3 号 p. 273-280
    発行日: 2003/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    The numerical simulation of the pulsed YAG laser-hardening process of three kinds of Cr-Mo steel containing different carbon by use of the heat treatment simulation code “HEARTS” is implemented based on metallo-thermo-mechanics developed by the authors. The effects of carbon content on the characteristics of laser-hardened material are investigated. As the obtained results, more severe heating and cooling rates are need for the steel with higher carbon content, and the position near the laser irradiated surface on optical axis is heated up to the highest temperature. The austenite transformation in this case is accomplished in remarkably short time, and progresses from the heated surface. The martensite transformation is observed at lower temperature for carbon rich steel and is produced from inside of solid by self-cooling effect. Induced stresses during and after hardening process increase with higher carbon content.
  • 水野 衛, 肥田 政彦
    2003 年 52 巻 3 号 p. 281-287
    発行日: 2003/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Experiments on inelastic deformation of epoxy were performed under fundamental loading conditions systematically from the viewpoint of the formulation of an inelastic constitutive equation. In experiments under monotonic loading conditions, stress-strain relations depending on the loading rate and loading direction defined in stress space were elucidated. Moreover, creep curves and transient behaviors in tension with change in stress rate were obtained. In the case of loading conditions including unloading, on the other hand, strain recovery during unloading depending on the loading history was elucidated since the strain recovery is significant in epoxy. Then, the inelastic constitutive equation that has been developed for CFRP (epoxy reinforced by carbon fibers) so far was applied to the experimental results. In order to take into account the effect of hydrostatic pressure on the inelastic deformation of epoxy, the first invariant of stress tensor was introduced into the constitutive equation. The experimental results were simulated by the modified constitutive equation, and the describability of the inelastic deformation of epoxy by the modified constitutive equation was discussed.
  • 北川 正義, 都竹 卓也
    2003 年 52 巻 3 号 p. 288-293
    発行日: 2003/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Despite of much research on the effects of factors such as temperature and strain rate on yield stress in amorphous glassy polymers, the yield phenomenon, including stress drop starting just after yielding, has not been understood qualitatively. Furthermore, the importance of this constitutive law can improve the processes of forming and injection molding. In order to investigate yielding and formation process of shear bands followed by slip lines in amorphous glassy polymers, simple shear tests were executed under constant speed and creep at room temperature using quenched and annealed specimens of polycarbonate and polyvinyl chloride. The deformation process was observed through a polarizing microscope during the test. It is shown that for as-received and annealed materials, yielding occurs after the initiation of slip lines, and the formation and extension of shear bands, while for quenched materials, yielding begins at the formation of shear bands without slip lines. These results may be able to predict whether there are two types of the plastic deformation in amorphous glassy polymers.
  • 加藤 弘義, 宮川 豊章, 中村 明則, 土井 宏行
    2003 年 52 巻 3 号 p. 294-300
    発行日: 2003/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    We discussed the influence of additives, ground granulated blast-furnace slag and limestone powder, on the fluidity of cement paste with polycarboxylate-based superplasticizers (PC) by considering solid volume of powder in packed state, early hydration of paste, adsorption characteristics of PC and steric hindrance effects. The fluidity of cement paste increased with increasing the addition of additive. The solid volume of powder in packed state and the amount of adsorbed PC did not correlate with the fluidity. The loss on ignition decreased with the addition of additive. It is suggested that the decrease of combined water relates to the increase of fluidity. The fluidity increased linearly with decreasing sulfate ion concentration by the addition of additive. We had showed that sulfate ion reduced the thickness of adsorbed PC and steric hindrance effects. The results of present study suggest that the change in fluidity due to the addition of additive is caused by the change in the dispersion of particles by sulfate ions.
  • 石川 朝之, 堀内 清史, 柴田 博幸, 戸谷 和光, 武田 邦彦
    2003 年 52 巻 3 号 p. 301-308
    発行日: 2003/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Effect of pit destruction and boric compounds on flame retardancy of woods was studied using “Obi” Japanese cedar which grew in Miyazaki prefecture. As woods has a lot of cells which are independent and isolated each other by blockade of the pit at the end of the life, woods was pretreated and destroy the pit under several conditions so as to be blended with flame retardants. The rate of the destruction depended on the pretreated temperature and about 70% to the whole pit could be destroyed at 120°C. After boronic compounds were impregnated, combustion tests and thermal degradation experiments have been achieved. The heat release rate observed by a cone calorimeter decreased with increasing boron contents in wood. Namely, the peak value of no-treated cedar was 200kW/m2 and the total amount of the heat release was twice as much as that of treated cedar. The difference was recognized between heartwoods and sapwood. It was caused by the location of both woods. Thermal degradation and elemental analysis of residue at higher temperature were also measured and discussed on relation to flame retardancy and structural changes in wood during combustion and degradation. In particular, the decomposition rate of untreated woods at 350-550°C was twice as much as that of the treated woods. It means the total heat releases were proportional to the decomposition rate because fuels by which materials can continue to burn was supplied by the decomposition.
  • 野村 宗吾, 瀧川 敏算, 升田 利史郎, 田村 暢成, 中村 達雄, 清水 慶彦
    2003 年 52 巻 3 号 p. 309-313
    発行日: 2003/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    To develop small-diameter vascular grafts with high anti-thrombogenicity and the ability to grow, we prepared heparinized acellular matrices (HEPARINs) made from detergent-treated porcine carotid arteries. In this study, the mechanical properties of HEPARIN as well as the acellular matrix before heparinization (ACM) were investigated under uniaxial and biaxial deformation. The values of the initial Young's Modulus (E0) and tangent Modulus (Et) obtained by uniaxial elongation for the ACM were almost identical to those for a fresh porcine carotid artery (FRESH), but HEPARIN showed higher values than FRESH for the two mechanical parameters. The pressure at burst for ACM estimated by biaxial deformation was lower than the other samples, but was still much higher than the normal blood pressure. It was shown that HEPARIN is one of the promising materials as a scaffold for regeneration of blood vessels as long as mechanical properties are concerned.
  • 井上 正志, 尾崎 邦宏, 森下 浩延, 田村 裕之, 坂元 秀治
    2003 年 52 巻 3 号 p. 314-318
    発行日: 2003/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    The complex Young's modulus and the complex strain-optical coefficient of two series of polycarbonate derivatives were measured around the glass transition zone to investigate the molecular structure-property relationships. The data were analyzed with the modified stress-optical rule: The complex Young's modulus was separated into two component function, R and G. Main chain flexibility and the intrinsic birefringence were estimated from the R component. It was found that the main flexibility was insensitive to the substitution on phenylene groups or propylene groups while the intrinsic birefringence could be significantly reduced.
  • 白石 浩平, 松田 尚, 大橋 俊彦, 好満 芳邦, 杉山 一男
    2003 年 52 巻 3 号 p. 319-324
    発行日: 2003/03/15
    公開日: 2009/06/03
    ジャーナル フリー
    Two series of copolymers, Poly (RAAm-co-ST) and Poly (BMAAm-co-R'MA), as the novel primers in adhesive bonding polypropylene (PP) were prepared by radical copolymerization of alkoxymethyl acrylamide (RAAm) and styrene (ST) or alkyl methacrylate (R'MA). Alkoxy groups (OR) in the RAAm moieties used were methoxy, ethoxy, isobutoxy and butoxy, whereas alkyl groups (R') in the R'MA moieties were methyl, ethyl, isopropyl, isobutyl, n-butyl and n-hexyl. Homopolymer of RAAm, Poly (RAAm), was also prepared and characterized: the glass transition temperature of Poly (RAAm) was Tg=76.8-70.0°C and Poly (RAAm) was thermally decomposed through a two step degradation with the evolution of corresponding alcohol. The bonding properties of PP, using two series of copolymers as primers, were studied by measuring the shear strength (τ) of single-lap joints between PP and PP or other substrates such as polyethyleneterephthalate (PET), nylon 66 (66N), alminium, steel and glass. The primers tested were effective when used with polyurethane adhesive. Mixed substrate bonds prepared between PP and others gave substantial bond strength (τ=48.4-51.3MPa) in comparison to bond strength for unprimered controls (τ=8.9-16.7MPa). Maximum bond strength was obtained when Poly (BMAAm-co-HMA) was chosen as a primer. The mechanism for the adhesive bonding of PP was discussed.
  • 中井 善一, 菅田 淳
    2003 年 52 巻 3 号 p. 325-331
    発行日: 2003/03/15
    公開日: 2009/06/03
    ジャーナル フリー
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