Journal of Computational Science and Technology
Online ISSN : 1881-6894
2 巻 , 4 号
選択された号の論文の24件中1~24を表示しています
Papers
  • Luis A. DIAGO, Tetsuko KITAOKA, Ichiro HAGIWARA
    2008 年 2 巻 4 号 p. 401-412
    発行日: 2008年
    公開日: 2008/08/01
    ジャーナル フリー
    Automatic recognition of facial expressions can be an important component of natural human-machine interactions. While a lot of samples are desirable for estimating more accurately the feelings of a person (e.g. likeness) about a machine interface, in real world situation, only a small number of samples must be obtained because the high cost in collecting emotions from observed person. This paper proposes a system that solves this problem conforming to individual differences. A new method is developed for facial expression classification based on the combination of Holographic Neural Networks (HNN) and Type-2 Fuzzy Logic. For the recognition of emotions induced by facial expressions, compared with former HNN and Support Vector Machines (SVM) classifiers, proposed method achieved the best generalization performance using less learning time than SVM classifiers.
  • Tetsuko KITAOKA, Luis A. DIAGO, Ichiro HAGIWARA, Satoshi KITAZAKI, Shi ...
    2008 年 2 巻 4 号 p. 413-422
    発行日: 2008年
    公開日: 2008/08/12
    ジャーナル フリー
    This paper concerns the engineering analysis of “Iyashi”, a peculiar concept to the Japanese, which affect person's heart and may change their expression and behavior. We have integrated the advocator's view of “Iyashi”, analyzed the social background of “Iyashi” and have defined Iyashi and also the Iyashi expression. As the facial expression is the special and important stimulus for both observers and people who show expressions, we want to prove the existence of expressions that change the observer's emotion with Iyashi. We have developed the system to clarify the combination of facial features important for Iyashi through the psychological experiments and the analysis by Holographic Neural Networks (HNN). HNN analysis gave the structure of the Iyashi expression, that is the important combination of the physical facial parameters contributing to the high degree of Iyashi. Based on the structure of Iyashi we are able to generate the Iyashi expression appropriate for each person.
  • Hiroshi NAKASHIMA, Yuzuru TAKATSU
    2008 年 2 巻 4 号 p. 423-434
    発行日: 2008年
    公開日: 2008/08/12
    ジャーナル フリー
    The goal of this study is to develop a practical and fast simulation tool for soil-tire interaction analysis, where finite element method (FEM) and discrete element method (DEM) are coupled together, and which can be realized on a desktop PC. We have extended our formerly proposed dynamic FE-DE method (FE-DEM) to include practical soil-tire system interaction, where not only the vertical sinkage of a tire, but also the travel of a driven tire was considered. Numerical simulation by FE-DEM is stable, and the relationships between variables, such as load-sinkage and sinkage-travel distance, and the gross tractive effort and running resistance characteristics, are obtained. Moreover, the simulation result is accurate enough to predict the maximum drawbar pull for a given tire, once the appropriate parameter values are provided. Therefore, the developed FE-DEM program can be applied with sufficient accuracy to interaction problems in soil-tire systems.
  • Takashi ISHIDA, Shun TAKAHASHI, Kazuhiro NAKAHASHI
    2008 年 2 巻 4 号 p. 435-446
    発行日: 2008年
    公開日: 2008/08/21
    ジャーナル フリー
    In this study, an efficient and robust Cartesian mesh generation method for Building-Cube Method (BCM) is proposed. It can handle “dirty” geometry data whose surface has cracks, overlaps, and reverse of triangle. BCM mesh generation is implemented by two procedures; cube generation and cell generation in each cube. The cell generation procedure in this study is managed in each cube individually, and parallelized by OpenMP. Efficiency of the parallelized BCM mesh generation is demonstrated for several three-dimensional test cases using a multi-core PC.
  • Stephane NDONG-MEFANE, Hiroshi KANAYAMA, Masao OGINO, M. F. EL-AMIN
    2008 年 2 巻 4 号 p. 447-458
    発行日: 2008年
    公開日: 2008/09/09
    ジャーナル フリー
    In this paper, we highlight the existence of some instability in finite element method appearing for high values of the Peclet number in the model of hydrogen diffusion in materials. A stabilization technique is used to overcome the instability problem and therefore improve this scheme. We manage to improve the scheme and decrease the instability, and we highlight the strong influence of the stabilization parameter in this particular case.
  • Tomohito TSURU, Yoji SHIBUTANI
    2008 年 2 巻 4 号 p. 459-467
    発行日: 2008年
    公開日: 2008/10/23
    ジャーナル フリー
    Recent advances in miniaturization and highly-accurate measurement techniques have allowed mechanical properties to be measured at the nanometer scale. Nanoindentation has been widely used because of its applicability in ambient conditions. Unstable displacement burst or the abrupt growth of indent displacement after homogeneous elastic deformation observed in crystalline materials is a unique plastic deformation characteristic (nanoplasticity). In the present paper, a series of atomistic simulations of nanoindentation in single crystalline aluminum and copper are performed in analyzing the critical state for dislocation nucleation and interaction between dislocations beneath the indenter. With reference to the Hertzian solution based on isotropic linear elastic theory, both the anisotropic effect and nonlinear behavior of nanoindentation are discussed in detail. The discovery was made that the incipient yield process is strongly related to the triaxial stress state created beneath the indenter, and that energetically unfavorable interactions accompanied with cross slip induce the formation of prismatic dislocations.
  • Hideo KOGUCHI, Shinya NAKAMURA
    2008 年 2 巻 4 号 p. 468-477
    発行日: 2008年
    公開日: 2008/10/29
    ジャーナル フリー
    A mismatch in material properties may cause a stress singularity, which leads to the failure of bonding in joints. It is important to analyze the stress singularity field for evaluating the strength of the interface in three-dimensional joints. Thermal residual stresses occur in a cooling process after bonding the joints at a high temperature, and the stress singularity for thermal stresses also occurs at an interface corner in the joints. In the present paper, a boundary element method and an eigenvalue analysis formulated using a finite element method are used for evaluating the intensity of singularity of the residual thermal stresses at a vertex in a joint. A three-dimensional boundary element program based on the fundamental solution for a two-phase isotropic body is used. The singular stress field for residual thermal stresses at the vertex in three-dimensional bonded structures with an interlayer is analyzed while varying the material properties of the interlayer. In addition, the relationship between Dundurs' parameter for three-dimensional stress states and the intensity of singularity is derived. In the present study, the stress singularity field is estimated for an arbitrary material combination investigated using this relationship under thermal loadings.
  • Koji SUEOKA, Yanbo WANG, Seiji SHIBA, Seishiro FUKUTANI
    2008 年 2 巻 4 号 p. 478-487
    発行日: 2008年
    公開日: 2008/10/30
    ジャーナル フリー
    The effect of compressive or tensile plane-stress on formation energies and electronic properties of point defects in Si single crystal was studied by first principles approach for in-plane strain up to 5.0 %. It was found that the formation energy of interstitial Si (I) decreased under tensile in-plane strain. On the other hand, the formation energy of vacancy (V) decreased under compressive in-plane strain. The most stable states of I and V in intrinsic Si were I+2 at T site and V0 respectively, independent of type and value of the in-plane strain.
  • Miki YAMAZAKI, Naoto SAITO, Masaki TSURUKI, Takashi MACHIDA
    2008 年 2 巻 4 号 p. 488-498
    発行日: 2008年
    公開日: 2008/11/10
    ジャーナル フリー
    This paper describes a newly developed optimization system based on a new Finite Element Sensitivity Analysis (FESA) of mechanical structures with coupled problems concerning heat conduction and stress analysis. In this system, variation in a material property, for example heat conductivity, is considered as a structural change because changing a material property locally or partially is difficult. Like FESA, this system requires just one calculation and then offers efficient designing products. The effectiveness of the system was verified by results showing that optimizations of structural design were given efficiently when the system was applied to the design of actual industry products: a turbine blade and a cooling jacket of computer modules.
  • Hiroshi KANAYAMA, Masao OGINO, Reza MIRESMAEILI, Takuya NAKAGAWA, Taka ...
    2008 年 2 巻 4 号 p. 499-510
    発行日: 2008年
    公開日: 2008/11/10
    ジャーナル フリー
    The role of hydrogen in hydrogen embrittlement, stress corrosion cracking and hydrogen induced cracking has been largely determined. The hydrogen cracking problem in metallurgical fields has been studied for many years. In spite of that, it is still not possible to explain exactly how the presence of hydrogen within the metal structure leads to hydrogen embrittlement and crack formation. Hydrogen-enhanced localized plasticity (HELP) is an acceptable mechanism of hydrogen embrittlement and hydrogen-induced cracking in materials. In the present work, a finite element analysis is implemented to estimate the large deformation elasto-plastic behavior of the material in conjunction with the hydrogen diffusion analysis results. Hydrogen is highly mobile and can diffuse through the crystal lattice dissolving into its interstitial sites. It is necessary to assume the model which can describe the hydrogen diffusivity near the blunting crack tip as well as the large deformation phenomena. Finite element analysis is here employed to solve the coupled boundary-value problem of large strain elasto-plasticity and equilibrium hydrogen distributions ahead of a blunting crack tip by taking into consideration the effect of hydrogen on local flow stress.
  • Yutaka TOI, Daegon CHOI
    2008 年 2 巻 4 号 p. 511-522
    発行日: 2008年
    公開日: 2008/11/18
    ジャーナル フリー
    The existing one-dimensional constitutive model for shape memory alloys is extended to take account of the porosity and the strain rate effect by using the internal state variables representing the porosity and the martensite volume fraction. The proposed constitutive equation is applied to the simulations for the quasi-static and the dynamic behaviors of dense and porous shape memory alloys at various temperatures and strain rates. The calculated results are compared with the uniaxial test results for dense and porous NiTi alloys to illustrate the validity of the present constitutive modeling. It is expected that the finite element program implementing the proposed constitutive equation will be a powerful tool to predict the mechanical behaviors of various porous shape memory alloy devices.
  • Yutaka TOI, Woosang JUNG
    2008 年 2 巻 4 号 p. 523-534
    発行日: 2008年
    公開日: 2008/11/18
    ジャーナル フリー
    The electrochemical-poroelastic bending behavior of conducting polymer actuators has an attractive feature, considering their potential applications such as artificial muscles or MEMS. In the present study, a computational modeling is presented for the bending behavior of polypyrrole-based actuators. The one-dimensional governing equation for the ionic transportation in electrolytes given by Tadokoro et al. is combined with the finite element modeling for the poroelastic behavior of polypyrroles considering the effect of finite deformation. The validity of the proposed model has been illustrated by comparing the computed results with the experimental results in the literatures.
  • Yutaka TOI, Daegon CHOI
    2008 年 2 巻 4 号 p. 535-546
    発行日: 2008年
    公開日: 2008/11/18
    ジャーナル フリー
    The three-dimensional incremental finite element formulation for the multiaxial behavior of shape memory alloy devices is proposed in the present study by considering the coupling effect of the axial and torsional behaviors of shape memory alloys. The previously proposed one-dimensional constitutive model for shape memory alloy devices is extended to take account of the multiaxial stress state introducing some new material constants. The calculated results are compared with the uniaxial, purely torsional and multiaxial test results for NiTi tubes to illustrate the validity of the proposed computational modeling.
  • Ichiro FURUHASHI, Nobuchika KAWASAKI, Naoto KASAHARA
    2008 年 2 巻 4 号 p. 547-558
    発行日: 2008年
    公開日: 2008/11/26
    ジャーナル フリー
    Temperature and thermal stress in cylindrical vessels were analysed for the thermal stratification of contained fluid. Two kinds of temperature analysis results were obtained such as the exact temperature solution of eigenfunction series and the simple approximate one by the temperature profile method. Furthermore, thermal stress shell solutions were obtained for the simple approximate temperatures. Through comparison with FEM analyses, these solutions were proved to be adequate. The simple temperature solution is described by one parameter that is the temperature decay coefficient. The thermal stress shell solutions are described by two parameters. One is the ratio between the temperature decay coefficient and the load decay coefficient. Another is the nondimensional width of stratification. These solutions are so described by few parameters that those are suitable for the simplified thermal stress evaluation charts. These charts enable quick and accurate thermal stress evaluations of cylindrical vessel of this problem compared with conventional methods.
  • Tomohito TSURU, Yoji SHIBUTANI
    2008 年 2 巻 4 号 p. 559-567
    発行日: 2008年
    公開日: 2008/11/26
    ジャーナル フリー
    Abrupt growth of displacement observed in the relationship between indent load and indent depth in nanoindentation of crystalline materials, so-called displacement burst, has been recognized as one of the representative examples of nanoscale plastic behavior (nanoplasticity). This phenomenon corresponds to the early stage of plastic deformation and is greatly influenced by the collective dislocation emission. In the present paper a simplified model is constructed for the first displacement burst with use of the elastic theory based on both the Hertzian contact theory and the classical dislocation theory to evaluate the displacement burst in nanoindentation. The result of the analytical model for the energy equilibrium revealed that there is a strong correlation between burst width and critical indent depth that corresponds to the dislocation emission. Finally, it is shown that more than one hundred high-density dislocations are generated simultaneously and surface step corresponding to the Burgers vector of dislocation dipole of each emitted dislocation causes significant displacement burst.
  • Yasutomo UETSUJI, Yu SATOU, Hideyuki NAGAKURA, Hisanao NISHIOKA, Hiroy ...
    2008 年 2 巻 4 号 p. 568-577
    発行日: 2008年
    公開日: 2008/11/26
    ジャーナル フリー
    Microstructural crystal morphology, which affects strongly on macroscopic electromechanical behaviors of polycrystalline piezoelectric ceramics, was analyzed using electron backscatter diffraction method. We coated piezoelectric ceramics with amorphous osmium to defend against electrification caused by electron beam, and measured crystal orientations of 140×120 μm2 over region at 0.32 μm scanning interval. Then the obtained crystal orientations were applied to a multiscale finite element analysis to evaluate the relation with macroscopic mechanical and electrical properties. Especially, we investigated on finite element modeling conditions to sample crystal orientations, and presented a representative volume element of microstructure to compute the macroscopic homogenized properties and the microscopic localized responses.
  • Toshimichi FUKUOKA, Masataka NOMURA, Yuyong ZHAO
    2008 年 2 巻 4 号 p. 578-586
    発行日: 2008年
    公開日: 2008/12/08
    ジャーナル フリー
    When analyzing the strength of large structures, the stiffness of the foundation, on which the structure is placed, might significantly affect the numerical results. In this paper, a finite element approach to estimate the foundation stiffness as an inverse problem is proposed, where the target large structure is placed on the elastic foundation that are modeled as groups of one-dimensional spring elements in parallel. The magnitude of the spring constant that represents the foundation stiffness can exactly be calculated algebraically by use of the same number of measured surface deflections. In the numerical analyses, unknowns are the diagonal components in the global stiffness matrix that include the aforementioned spring constants. The validity and the accuracy of the proposed numerical method are verified by comparing the numerical results to the exact solutions for bending problems of a cantilever supported by a single spring element.
  • Satoshi ISHIKAWA, Akihiko TOKUDA, Hidetoshi KOTERA
    2008 年 2 巻 4 号 p. 587-596
    発行日: 2008年
    公開日: 2008/12/17
    ジャーナル フリー
    On the basis of hyperelastic material behavior various forms of the strain energy density function, depending either on the invariants of the right Cauchy-Green deformation tensor or on the principal stretches, have been proposed under the isotropy assumption. If a material behaves transversely isotropic behavior with respect to the reference configuration, then the strain energy function can depend on five principal invariants. Five principal invariants are ordinary three invariants and additional fourth and fifth invariants. In the area of automotive belt designing technique, the most material of belt is composed of fiber reinforced hyperelastic. In this paper, we propose the polynomial strain energy function and determinate its material constants for the fiber reinforced material.
  • Dai-heng CHEN, Takeshi MATSUMOTO, Shingo OZAKI
    2008 年 2 巻 4 号 p. 597-608
    発行日: 2008年
    公開日: 2008/12/17
    ジャーナル フリー
    In this paper, in-plane equivalent elastic modulus Ey of a hexagonal honeycomb sandwich, which includes the effect of face sheet interference, is studied by using numerical results of FEM. It is shown by comparing with deformation of practical honeycomb sandwich that there are two error factors to apply the rule of mixture to honeycomb sandwich. One of error factors is that the deformation of honeycomb core does not coincide with the face sheet since an inclined cell wall deforms much larger than a vertical cell wall. Another one is that the non-uniformity deformation of core along the height direction is induced by the interference effect with face sheet. Then, a method to calculate elastic modulus based on the compatibility condition of core and face sheet is proposed, and its validity is verified by using numerical results of FEM.
  • Shinobu SAKAI, Juhachi ODA, Shigeru YONEMURA, Jiro SAKAMOTO
    2008 年 2 巻 4 号 p. 609-619
    発行日: 2008年
    公開日: 2008/12/17
    ジャーナル フリー
    In the United States and Japan, baseball is a very popular sport played by many people. However, the ball used is hard and moves fast. A professional baseball pitcher in good form can throw a ball at speeds upwards of 41.7m/s (150km/hr). If a ball at this speed hits the batter, serious injury can occur. In this paper we will describe our investigations on the impact of a baseball with living tissues by finite element analysis. Baseballs were projected at a load cell plate using a specialized pitching machine. The dynamic properties of the baseball were determined by comparing the wall-ball collision experimentally measuring the time history of the force and the displacement using dynamic finite element analysis software (ANSYS/ LS-DYNA). The finite element model representing a human humerus and its surrounding tissue was simulated for balls pitched at variable speeds and pitch types (knuckle and fastball). In so doing, the stress distribution and stress wave in the bone and soft tissue were obtained. From the results, the peak stress of the bone nearly yielded to the stress caused by a high fast ball. If the collision position or direction is moved from the center of the upper arm, it is assumed that the stress exuded on the humerus will be reduced. Some methods to reduce the severity of the injury which can be applied in actual baseball games are also discussed.
  • Hiroyuki KAGAWA, Akira MORITA, Takuji MATSUDA, Shiro KUBO
    2008 年 2 巻 4 号 p. 620-631
    発行日: 2008年
    公開日: 2008/12/25
    ジャーナル フリー
    In the authors' previous study, fatigue crack propagation tests were performed using four-point bending specimens with multiple parallel edge notches at regular intervals of 10mm. In this study, similar tests were carried out using the specimens with crack intervals of 5mm or 2.5mm. It was found that multiple crack propagation behavior was affected by the crack interval. A small number of cracks grew selectively in the specimen with narrow crack intervals while many cracks grew to long lengths in the specimens with broad crack intervals. Experimental results were first simulated by a previously proposed method using stress intensity factor solution for multiple cracks with alternately different lengths. Simulation results showed a good agreement with experimental results in case of specimens with broad crack intervals but showed different tendency from test results in case of specimens with narrow crack intervals. To simulate the experimental results a new method was proposed, in which the stress intensity factor solution was modified to include an effect of cracks outside the neighboring two cracks. The method gave a good simulation result for the specimens with narrow crack intervals but gave higher propagation rate than experiment for the specimens with broad crack intervals, resulting in a conservative evaluation.
  • Dai-Heng CHEN, Shingo OZAKI
    2008 年 2 巻 4 号 p. 632-642
    発行日: 2008年
    公開日: 2008/12/25
    ジャーナル フリー
    In this study, the circumferential strain concentrations in cylindrical and square tubes with corrugated surfaces subjected to axial compression are studied using the finite element method. In cylindrical tubes, the yield strength σy, the hardening coefficient Eh of the material and the thickness t of the tube wall exert only a small influence on the strain concentration, so that the maximum circumferential strain can be approximately evaluated as a function of the wavelength 2λ and the amplitude a of the corrugations, and the cylinder radius R. For square tubes, however, the effect of the corner radius r, the thickness t, the yield strength σy, and the hardening coefficient Eh on the strain concentration is comparable to that of the wavelength 2λ and the amplitude a of the corrugations. The maximum circumferential strain increases with a decrease in the corner radius r/D, with a decrease in the thickness t, and with an increase in the ratio σy/Eh.
  • Hiroshi KANAYAMA, Hisayoshi TSUKIKAWA, Stephane Boris NDONG-MEFANE, Os ...
    2008 年 2 巻 4 号 p. 643-654
    発行日: 2008年
    公開日: 2008/12/25
    ジャーナル フリー
    Hydrogen is expected as new fuel instead of fossil fuel. It will be used as fuel of a fuel cell for which development is performed actively. But it is difficult to experiment the hydrogen dispersion in case of hydrogen leaks. Therefore clarifying the hydrogen dispersion with numerical analysis becomes important. Furthermore, hydrogen dispersion under various conditions can be clarified with numerical analysis, which is useful to use hydrogen safely. This paper deals with computer simulation of the hydrogen dispersion by a finite element method. The mathematical model of hydrogen dispersion is governed by the momentum equations, the continuity equation and the hydrogen mass conservation equation. The model presented here is a three-dimensional, incompressible, non-stationary model. This paper describes a finite element method with the stabilization technique for solving Navier-Stokes equations and the advection diffusion equation for hydrogen concentration like the Boussinesq approximation of thermal convection problems. Improved numerical results are also shown.
  • Daisuke YAMAZAKI, Vladimir SAVCHENKO
    2008 年 2 巻 4 号 p. 655-668
    発行日: 2008年
    公開日: 2008/12/25
    ジャーナル フリー
    3D meshes generated by acquisition devices such as laser range scanners often contain holes due to occlusion, etc. In practice, these holes are extremely geometrically and topologically complex. We propose a heuristic hole filling technique using particle systems to fill complex holes with arbitrary topology in 3D meshes. Our approach includes the following steps: hole identification, base surface creation, particle distribution, triangulation, and mesh refinement. We demonstrate the functionality of the proposed surface retouching system on synthetic and real data.
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