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  • Open Access

    ABSTRACT

    Influences of Nano-sized Crystalline Particles on the Mechanical Properties of Metallic Glass-- A Molecular Dynamics Study

    R. Matsumoto1, N. Miyazaki1, M. Nakagaki2

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.4, pp. 223-230, 2007, DOI:10.3970/icces.2007.004.223

    Abstract The mechanical properties of amorphous metals and metallic glasses are remarkably changed by precipitated crystalline particles. In this paper, the effects of crystal particle size and volume fraction on the flow stress of the metallic glass are evaluated by molecular dynamics simulations. The investigated volume fraction ranges from 0% (metallic glass) to 100% (nanocrystalline metal), and the average particle diameter ranges from 1nm to 12nm. It is revealed that the dispersed particle effects on the flow stress are very small in the entire volume fraction range when the average particle diameter is smaller than 3 More >

  • Open Access

    ABSTRACT

    Elastic-plastic constitutive equation taking account of particle size

    S. Takashima1, N. Miyazaki2, T. Ikeda3, M. Nakagaki4

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.4, pp. 215-222, 2007, DOI:10.3970/icces.2007.004.215

    Abstract Composite materials have complicated microstructures. These structures affect macroscopic deformation. In this study, we focus on the particle size effect in composite materials. For this purpose, we derived an elastic-plastic constitutive equation considering size effect by using Eshelby's theory and the strain gradient theory of plasticity. We performed a homogenized finite element analysis using the elastic-plastic constitutive equation. The results obtained from the analysis show increase of the strength with decrease of the particle size in composite materials. More >

  • Open Access

    ABSTRACT

    Higher-Order Stress and Size Effects Due to Self Energy of Geometrically Necessary Dislocations

    N. Ohno1, D. Okumura1

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.4, pp. 207-214, 2007, DOI:10.3970/icces.2007.004.207

    Abstract The self energy of geometrically necessary dislocations (GNDs) is considered to inevitably introduce the higher-order stress work-conjugate to slip gradient in single crystals. It is pointed out that this higher-order stress stepwise changes in response to in-plane slip gradient and thus directly influences the onset of initial yielding in polycrystals. The self energy of GNDs is then incorporated into the strain gradient theory of Gurtin (2002). The resulting theory is applied to model crystal grains of size D, leading to a D-1-dependent term with a coefficient determined by grain shape and orientation. It is thus More >

  • Open Access

    ABSTRACT

    Implicit Formulation of Homogenization Method for Periodic Inelastic Solids

    T. Asada1, N. Ohno1

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.4, pp. 201-206, 2007, DOI:10.3970/icces.2007.004.201

    Abstract In this study, to determine incremental, perturbed displacement fields in periodic inelastic solids, an incremental homogenization problem is fully implicitly formulated, and an algorithm is developed to solve the homogenization problem. It is shown that the homogenization problem can be iteratively solved with quadratic convergences by successively updating strain increments in unit cells, and that the present formulation allows versatility in the initial setting of strain increments in contrast to previous studies. The homogenization algorithm developed is then examined by analyzing a holed plate, with an elastoplastic micro-structure, subjected to tensile loading. It is thus More >

  • Open Access

    ABSTRACT

    Comparison of Fabrication Cost of Composite Bipolar Plates Made by Compression Molding and by Machining

    H.S. Lee1, W.S. Chu1, Y.C. Kang1, H.J. Kang1, S.H. Ahn2

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.3, pp. 195-200, 2007, DOI:10.3970/icces.2007.004.195

    Abstract The fuel cell is one of promising environment-friendly energy sources for the next generation. The bipolar plate is a major component of the Proton Exchange Membrane (PEM) fuel cell stack, and it takes a large portion of stack volume, weight and cost. In this study, as alternative materials for bipolar plate of PEM fuel cells, graphite composites were fabricated by compression molding and by machining. Graphite particles mixed with epoxy resin were used as the main substance to provide electric conductivity. Flow channels were fabricated by compression molding applying design of experiments (DOE) in order More >

  • Open Access

    ABSTRACT

    The Out-of-Plane Strain Measurement of Composite Sandwich Plate with Fully-Potted Insert Using Digital Phase-Shifting Shearography

    Song-Jeng Huang1, Yan-Fu Liu2

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.3, pp. 187-194, 2007, DOI:10.3970/icces.2007.004.187

    Abstract A digital shearographic (DS) technique is a tool well-suited for precision strain measurement and is a nondestructive testing technology. But the fringe patterns of shearography are not so clear. A phase-shifting technique is incorporated into DS and demonstrated to yield fringe patterns with good quality. The major purpose of this study is to produce a measuring system of digital phase-shifting shearography (DPSS) to measure out-of-plan strain of sandwich plate with fully-potted insert. The system mainly includes piezoelectric transducer, servo controller, Michelson shearing mechanism, image processing system and loading system. The Macy algorithm is used for More >

  • Open Access

    ABSTRACT

    Existence of Non-propagating Micro-cracks under the Fatigue Limit

    S. Nishida1, N. Hattori1

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.3, pp. 179-186, 2007, DOI:10.3970/icces.2007.004.179

    Abstract The authors have experimentally confirmed that the non-propagating microcracks are observed in the low carbon plain specimens subjected to the stress of fatigue limit by 1×107 cycles and not observed in those of pure copper and aluminum alloys etc.. In addition, there exists clear fatigue limit in typical austenitic stainless steel SUS304 but not exist the non-propagating micro-cracks subjected to the stress of fatigue limit by 1×107 cycles. On the other hand, there exist not only clear fatigue limit but also non-propagating micro-cracks in the high manganese austenitic steel (HMA 0.20%C steel). Then, the authors More >

  • Open Access

    ABSTRACT

    Identification Problems in Metal Forming

    Iwona Pokorska1, Andrzej Sluzalec2

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.3, pp. 171-178, 2007, DOI:10.3970/icces.2007.004.171

    Abstract This work has been focused on a unified approach for parameter identification in metal forming processes of poroplastic materials. In order to solve the associated inverse problem a chosen functional is minimized by the use of gradient based methods and a sensitivity analysis. Several numerical and experimental results were presented. These are: the direct problem of simple compression, re-identification of flow stress and identification of loading functions. More >

  • Open Access

    ABSTRACT

    Behaviour of Flexible Batter

    Sastry Vankamamidi1

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.3, pp. 167-170, 2007, DOI:10.3970/icces.2007.004.167

    Abstract The behaviour of single free head model flexible batter piles buried in sand and subjected to horizontal loads is investigated. The theoretical estimates of ultimate load, location and magnitude of maximum bending moment for the piles were obtained by considering a vertical rigid pile under inclined load and using semi empirical relations. The length of the equivalent rigid pile was based on the relative stiffness factor of the pile. Model tests were carried out using instrumented flexible piles of wide ranging flexibilities. The piles were buried in loose sand at batter angles of β = ± More >

  • Open Access

    ABSTRACT

    HYBRID a powerful Boundary Element-Finite Element Method(BEM/FEM) software for analysis of seismic response of multiphase porous media

    B. Gatmiri1

    The International Conference on Computational & Experimental Engineering and Sciences, Vol.4, No.3, pp. 159-166, 2007, DOI:10.3970/icces.2007.004.159

    Abstract This document summarizes the basic concepts and steps of establishment of the set of equations of wave propoagation in far field and of the dynamic behaviour of porous media in the near field. A breif description of HYBRID software as a powerful tool for evaluation of local seismic site effect is presented. The Combination of the FEM and BEM and improvement of numerical algorithm for the time truncation are described. More >

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