Journal of Computational Science and Technology
Online ISSN : 1881-6894
ISSN-L : 1881-6894
3 巻, 2 号
選択された号の論文の9件中1~9を表示しています
Papers
  • Tomotsugu SHIMOKAWA, Toshiyasu KINARI, Sukenori SHINTAKU
    2009 年 3 巻 2 号 p. 408-416
    発行日: 2009年
    公開日: 2009/07/24
    ジャーナル フリー
    Adaptivemesh refinement and local/non-local transition in our quasicontinuum method (Phys. Rev. B, Vol. 69, No. 21(2004), pp.214104(1-10)) are studied in this paper. Although deformation gradients have been used to determine the mechanical state of an element in the original quasicontinuum method, we adopt elastic stiffness coefficients, which govern stress-strain relationships at finite deformation. Because elastic stiffness coefficients are calculated using the interatomic potential function, we do not need to prepare reference node (atomic) positions. To confirm its applicability, we performed nano-indentation simulations in two dimensions, and found that the criterion values estimated using deformation gradients and elastic stiffness coefficients show a positive correlation.
  • Takuya KINOSHITA, Makoto OHSAKI
    2009 年 3 巻 2 号 p. 417-425
    発行日: 2009年
    公開日: 2009/08/27
    ジャーナル フリー
    A sequential optimization approach is presented for topology synthesis of bistable compliant frame mechanisms. The truss-element-based approach for design of bistable compliant mechanisms enables us to overcome the difficulties due to local buckling in the optimization process considering geometrical nonlinearity. However, the truss mechanisms has a drawback in practical fabrication; it is impossible to make a singlepiece mechanism because of the existence of pin joints. In this paper, we propose an optimization method for converting a compliant truss mechanism to an equivalent frame mechanism. In our conversion process, some thin elements are placed at the connections as pseudo-joints to adjust the flexibility of the structure. The geometrically nonlinear behavior and the stability of a converted frame mechanism are also investigated. Numerical example demonstrates the effectiveness of our conversion method.
  • Dai-Heng CHEN, Hiroshi YOSHIDA, Shingo OZAKI
    2009 年 3 巻 2 号 p. 426-436
    発行日: 2009年
    公開日: 2009/10/16
    ジャーナル フリー
    In this paper, the crushing behavior of a honeycomb structure subjected to axial compression is studied by the finite element method. Deformation mechanisms are clarified to understand the energy absorption in axial compression of a honeycomb structure with a three-fold point corner. It is found that, in the crushing process of a model with cell walls of equal thickness (t-t-t model), the folds generated along the full length of the plates crush simultaneously. In contrast, during the crushing process of the model with one wall twice as thick (the t-t-2t model), the folds are concentrated in the middle part of the plates, and the deformation mode becomes progressive. Based on the assumption that strain energies due to traveling hinges are equivalent, the conventional theoretical expression for the average load is applied to the present t-t-2t model, which ignores the occurrence of separation of the glued part. In addition, a theoretical prediction model for the average load of the simultaneous mode is proposed. The validity of the proposed model is then verified by comparing the results with the numerical results from the finite element method.
  • Dai-Heng CHEN, Kazuyuki HATTORI, Shingo OZAKI
    2009 年 3 巻 2 号 p. 437-448
    発行日: 2009年
    公開日: 2009/10/16
    ジャーナル フリー
    In this paper, the effect of radial corrugation on the crushing behaviors of circular tubes is studied by using the finite element method. The numerical analysis is carried out on two geometrically different types of corrugations, ”radial corrugated tube” (RCT) and ”radial corrugated tube with corners” (RCTC). To compare crushing behaviors of those of corrugated circular tubes, a non-corrugated circular tube (CT) is also analyzed. It is revealed that, in the crushing process, the crushing mode of RCT becomes more unstable than that of CT since the wavelength of the fold becomes long and the fold concentrates to the center of the wavelength. However, when the length and the diameter of the tubes are set to the same levels, RCT demonstrates good energy absorption characteristics. Further, it is shown that the compressive load and load efficiency of RCTC increases due to the corner part.
  • Koji WATANABE, Kenichi MATSUNO
    2009 年 3 巻 2 号 p. 449-459
    発行日: 2009年
    公開日: 2009/10/21
    ジャーナル フリー
    This paper presents a new method for simulating flows driven by a body traveling with neither restriction on motion nor a limit of a region size. In the present method named 'Moving Computational Domain Method', the whole of the computational domain including bodies inside moves in the physical space without the limit of region size. Since the whole of the grid of the computational domain moves according to the movement of the body, a flow solver of the method has to be constructed on the moving grid system and it is important for the flow solver to satisfy physical and geometric conservation laws simultaneously on moving grid. For this issue, the Moving-Grid Finite-Volume Method is employed as the flow solver. The present Moving Computational Domain Method makes it possible to simulate flow driven by any kind of motion of the body in any size of the region with satisfying physical and geometric conservation laws simultaneously. In this paper, the method is applied to the flow around a high-speed car passing through a hairpin curve. The distinctive flow field driven by the car at the hairpin curve has been demonstrated in detail. The results show the promising feature of the method.
  • Masae MURAOKA, Hiroshi OKUDA
    2009 年 3 巻 2 号 p. 460-475
    発行日: 2009年
    公開日: 2009/10/26
    ジャーナル フリー
    With the rapid growth of WAN infrastructures and development of Grid middleware, the cluster-of-clusters has become a realistic methodology for executing computationdemanding applications. While distributed computing or loosely connected applications have been successfully ported to the Grid environment, few tightly connected applications such as parallel finite element analysis (FEA) have been attempted. In this paper we focus on an iterative solver which is often used in FEA: the conjugate gradient (CG) method. By using both predictions and numerical experiments we evaluate the performance of the CG method parallelized via domain decomposition. From numerical experiments we measure the inter-cluster execution time and find it to be close to that obtained by the slowest cluster. At the level of performance currently found in most WAN systems, as long as the number of processes is kept adequately small, the increase in communication cost due to WAN is small relative to the computation cost. For a very large test model which realistically requires the utilization of remote resources, the work ratio stays above 86% even for 64 processes. Especially for very large models, using the distributed environment is expected to be a practical methodology even for parallel computations with communication as frequent as the one found in FEA. To evaluate the feasibility of parallel FEA on the C-of-C, we have proposed methods for a priori finding the optimal number of processes.
  • Masahiro TSUJI, Hiroyuki TOKUMASU, Shiro KUBO
    2009 年 3 巻 2 号 p. 476-487
    発行日: 2009年
    公開日: 2009/10/29
    ジャーナル フリー
    In residual stress fields, the so-called partial elastic contact of crack surfaces sometimes occurs, where a fatigue crack is closed at the crack mouth while it is open at the crack tip. The partial elastic contact has a significant effect on the lives of fatigue cracks. However, there are few studies on the partial elastic contact of crack surfaces for three-dimensional cracks. In this paper, the propagation paths and lives of semi-elliptical slant surface fatigue cracks are predicted. The finite element method was employed for these simulations. The residual stress was introduced by applying an equivalent nodal force in correspondence with initial strains. The results of the propagation paths and lives considering the partial elastic contact of crack surfaces differed from those without consideration of the elastic contact. In particular the estimated results of the crack propagation rate sometimes brought one-order difference. These results demonstrate the necessity of simulation considering the partial elastic contact of crack surfaces.
  • Yuya TACHIKAWA, Hiroshi KANAYAMA, Chiaki ISHII, Hiroshi HASEGAWA
    2009 年 3 巻 2 号 p. 488-498
    発行日: 2009年
    公開日: 2009/12/02
    ジャーナル フリー
    In this paper, numerical modeling methods for a fuel cell are explained. The aim of this study is to make an analysis system to perform investigation on the whole behavior of a fuel cell with higher precision. Through numerical analysis, the effects of changing the structure and the control can be made clear. Liquid water distribution and temperature distribution inside the fuel cell are analyzed and evaluated in general under various situations. This paper describes through a two-phase two-dimensional analysis effects of pressure and temperature for liquid water distribution in fuel cells.
  • Hwisim HWANG, Yasutomo UETSUJI, Sei-ichiro SAKATA, Kazuyoshi TSUCHIYA, ...
    2009 年 3 巻 2 号 p. 499-508
    発行日: 2009年
    公開日: 2009/12/28
    ジャーナル フリー
    A process crystallography algorithm based on the first-principles aided triple-scale analysis is newly developed to design biocompatible piezoelectric thin films fabricated on a substrate. The pseudo-potential method within the density functional theory was used to predict the crystal morphology of thin film, such as preferred orientations and their fractions as well as the structural stability of possible conformations of crystal clusters on substrates. A crystal morphology at the micro scale was selected and macro homogenized properties of piezoelectric thin film were obtained through a double-scale finite element analysis based on the crystallographic homogenization theory. Further, our analysis was applied to the existent biocompatible piezoelectric BaTiO3 thin films, fabricated on SrTiO3(110), SrTiO3(001) and MgO(100) substrates. Numerical results of the preferred orientations of the micro structure and the homogenized dielectric constants of the macro structure showed good agreements with experimental results. Additionally, the proposed process crystallography algorithm was applied to the new biocompatible piezoelectric MgSiO3 thin film generation, which has been found by the first-principles calculation in the previous study. As a result, the computational result indicates that the Cr(110) substrate is most suitable for stable crystal growth of [101] oriented MgSiO3 and shows high piezoelectric stress constants, such as e33= 5.39 C/m2 and e31= -3.64 C/m2.
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