Papers - Takano, Naoki

マルチスケール法による不均質体中のき裂先端におけるミクロ応力解析

高野直樹, 奥野義紘

日本機械学会論文集(A編) 70 ( 692 ) 525 - 531 2004.04

Research paper (scientific journal), Joint Work, Accepted

Three-scale finite element analysis of heterogeneous media by asymptotic homogenization and mesh superposition methods

Naoki Takano, Yoshihiro Okuno

International Journal of Solids and Structure (International Journal of Solids and Structures)  41 ( 15 ) 4121 - 4135 2004

Research paper (scientific journal), Joint Work, Lead author, Accepted,  ISSN  00207683

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This paper studies a three-scale computational method that simultaneously considers the microstructure of heterogeneous materials, the macroscopic component, and the fracture origin such as interface or crack. The synergetic application of the asymptotic homogenization and mesh superposition methods to problems with strong scale mixing is emphasized. The scale gap between the microstructure and the component is very large, but the fracture origin is at the middle scale between them. The overall behavior is analyzed by means of the homogenization of the heterogeneity expressed by the unit cell model, while the fracture origin is modeled directly with the microscopic heterogeneity by another microscopic mesh. The microscopic mesh is superposed onto the macroscopic mesh. This mesh superposition method can analyze the non-periodic microscopic stress at the crack tip under a non-uniform macroscopic strain field with high gradient. Hence, the present three-scale method can accurately focus on the behaviors at arbitrary scale differently from the conventional hierarchical model. A demonstrative example of porous thin film on a substrate with an interface crack was solved and the microscopic stress was analyzed at the crack tip considering the random dispersion of pores and the high gradient of macroscopic strain field. To solve the large-scale 3D problem with approximately 80,000 solid elements, a renumbering technique and the out-of-core skyline solver was employed. © 2004 Elsevier Ltd. All rights reserved.

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Study on large deformation characteristics of knitted fabric reinforced thermoplastic composites at forming temperature by digital image-based strain measurement technique

Naoki Takano, Masaru Zako, Reiko Fujitsu and Kazuaki Nishiyabu

Composites Science and Technology (Composites Science and Technology)  64 ( 13-14 ) 2153 - 2163 2004

Research paper (scientific journal), Joint Work, Lead author, Accepted,  ISSN  02663538

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The continuous fiber reinforced thermoplastic composites, such as textile composites, have many attractive properties and functions and they are used widely nowadays in industrial applications. The important point in the design and manufacturing is that the composites as well as the reinforcing textiles undergo large deformation during thermoforming, which is much influential on the overall properties. Hence, the large deformation characteristics must be investigated at thermoforming temperature. For this sake, the digital image-based measurement technique of large strain distribution is developed. It is applicable to arbitrary complex shaped components with the help of 3D-CAD. As the large strain definition, Biot's strain is adopted that is calculated by the polar decomposition of the deformation gradient tensor based on continuum mechanics. The developed strain measurement technique is applied to the deep-drawing of aramid rib-knitted fabric reinforced polypropylene composites. The comparison between rib and plain-knitted fabrics reinforced composites is studied and many differences are found. The large deformation characteristics are also investigated from microscopic point of view under uniaxial tension at thermoforming temperature. © 2004 Elsevier Ltd. All rights reserved.

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界面き裂を有する不均質接合体のマルチスケール有限要素解析

高野直樹, 座古勝, 奥野義紘

材料 52 ( 8 ) 952 - 957 2003.08

Research paper (scientific journal), Joint Work, Lead author, Accepted

テキスタイル複合材料成形品における大ひずみ分布のデジタルイメージベース計測

高野直樹, 座古勝, 藤津麗子, 西藪和明

日本複合材料学会誌 29 ( 1 ) 17 - 23 2003.01

Research paper (scientific journal), Joint Work, Lead author, Accepted

Microstructure-based stress analysis and evaluation for porous ceramics by homogenization method with digital image-based modeling

Naoki Takano, Masaru Zako, Futoshi Kubo, Keiichi Kimura

International Journal of Solids and Structures (International Journal of Solids and Structures)  40 ( 5 ) 1225 - 1242 2003

Research paper (scientific journal), Joint Work, Lead author, Accepted,  ISSN  00207683

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Multi-scale analysis using the asymptotic homogenization method is becoming a matter of concern for microstructural design and analysis of advanced heterogeneous materials. One of the problems is the lack of the experimental verification of the multi-scale analysis. Hence, it is applied to the porous alumina with needle-like pores to compare the predicted homogenized properties with the experimental result. The complex and random microstructure was modeled three-dimensionally with the help of the digital image-based modeling technique. An appropriate size of the unit microstructure model was investigated. The predicted elastic properties agreed quite well with the measured values. Next, a four-point bending test was simulated and finally the microscopic stress distribution was predicted. However, it was very hard to evaluate the calculated microscopic stress quantitatively. Therefore, a numerical algorithm to help understanding the three-dimensional and complex stress distribution in the random porous microstructure is proposed. An original histogram display of the stress distribution is shown to be effective to evaluate the stress concentration in the porous materials. © 2002 Elsevier Science Ltd. All rights reserved.

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Multi-scale finite element analysis of porous materials and components by asymptotic homogenization theory and enhanced mesh superposition method

Naoki Takano, Masaru Zako, Yoshihiro Okuno

Modelling and Simulation in Materials Science and Engineering (Modelling and Simulation in Materials Science and Engineering)  11 ( 2 ) 137 - 156 2003

Research paper (scientific journal), Joint Work, Lead author, Accepted,  ISSN  09650393

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To analyse the macroscopic and microscopic behaviours of heterogeneous materials and components, a multi-scale computational method is studied. Although asymptotic homogenization theory has been the main tool during the last decade to solve various multi-scale problems, the assumption of the periodicity of the microscopic unit cell and the incapability of considering the scale effect have resulted in the limitations to this theory's applications. These problems should be overcome because advanced materials are often used as joint or laminated components and the interface crack problem must be analysed. For this sake, a novel multi-scale finite element method is proposed that uses the enhanced mesh superposition method together with the asymptotic homogenization theory. The finite element mesh superposition method uses the global mesh and the local mesh that is superimposed arbitrarily onto the global mesh. The enhanced method allows the adoption of different constitutive laws for the two meshes. The advantage of the homogenization theory to predict the homogenized material model accurately based on the complex microstructure is still utilized. The homogenized material model is used for the global mesh, whilst the microscopic heterogeneity and the crack are considered in the local mesh with the material properties of the constituents. The formulation, modeling strategy, implementation and numerical accuracy of the proposed method is described. A porous ceramic is studied in the numerical example.

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針状気孔を有するアルミナ多孔体の３次元ミクロ構造モデリングと均質化

高野直樹, 木村圭一, 座古勝, 久保太

日本機械学会論文集(A編) 68 ( 672 ) 1163 - 1169 2002.08

Research paper (scientific journal), Joint Work, Lead author, Accepted

セラミックスのランダムなミクロ構造を考慮したマルチスケール解析とミクロ応力評価

高野直樹, 木村圭一, 座古勝, 久保太

日本機械学会論文集(A編) 68 ( 671 ) 1046 - 1053 2002.07

Research paper (scientific journal), Joint Work, Lead author, Accepted

せん断変形した織布の樹脂透過テンソルの数値解析

高野直樹, 座古勝, 岡崎亨

日本機械学会論文集(A編) 68 ( 668 ) 529 - 536 2002.04

Research paper (scientific journal), Joint Work, Lead author, Accepted

Microstructure-based evaluation of the influence of woven architecture on permeability by asymptotic homogenization theory

Naoki Takano, Masaru Zako, Toru Okazaki, Kenjiro Terada

Composites Science and Technology (Composites Science and Technology)  62 ( 10-11 ) 1347 - 1356 2002

Research paper (scientific journal), Joint Work, Accepted,  ISSN  02663538

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A microstructure-based computational approach is taken to predict the permeability tensor of woven fabric composites, which is a key parameter in resin transfer moulding (RTM) simulation of polymer-matrix composites. An asymptotic homogenization theory is employed to evaluate the permeability from both macro- and microscopic standpoints with the help of the finite-element method (FEM). This theory allows us to study the relation between microscopic woven architecture and macroscopic permeability based on the method of two-scale asymptotic expansions. While the fluid velocity is introduced for Stokes flow microscopically, the macroscopic one is for seepage flow with the Darcy's law. The latter can be characterized for arbitrary configurations of unit microstructures that are analyzed for the former under the assumption of the periodicity. After discussing the validity of this approach, we present a typical numerical example to discuss the permeability characteristics of plain weave fabrics undergoing shear deformation in the preforming in comparison with the underformed one. Another notable feature of the proposed method is that the correlation between the macroscopic behaviors and the microscopic ones can be analyzed, which is important to analyze and/or design the RTM process. Hence, it is also demonstrated that the microscopic velocity field evaluated with macroscopic pressure gradient provides important information about the flow in RTM processes. © 2002 Elsevier Science Ltd. All rights reserved.

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セラミックス多孔体のイメージベースモデリングと均質化法による弾性解析

木村圭一, 高野直樹, 久保太, 小川秋水, 河本洋, 座古勝

Journal of the Ceramic Society of Japan 110 ( 1282 ) 567 - 575 2002

Research paper (scientific journal), Joint Work, Accepted

Microstructure-based deep-drawing simulation of knitted fabric reinforced thermoplastic by homogenization theory

Naoki Takano, Yoshihiko Onishi, Masaru Zako, Kazuaki Nishiyabu

International Journal of Solids and Structures 38 ( 36-37 ) 6333 - 6356 2001.08

Lead author, Accepted,  ISSN  00207683

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Process simulation of fiber reinforced composite materials is an important research theme for the development of low-cost and advanced functional composite materials. This paper aims at the simulation of deep-drawing process of knitted fiber reinforced thermoplastics and its verification. The feature of the simulation is that the large deformation of the knitted microstructures can be traced everywhere in the deep-drawn product. The homogenization theory is applied to analyze the micro-macro coupled behaviors of the knitted fabric composite material. By employing a simplified nonlinear computational algorithm, the deep-drawing simulation was carried out on a personal computer. The predicted largely deformed microstructures were compared with the experimental results. The numerical results and experimental ones agreed quite well. This deep-drawing simulation requires us to prepare only the mechanical properties of the constituents, while it provides us all the necessary quantities such as the deformation, strain, stress and stiffness from both microscopic and macroscopic standpoints. © 2001 Elsevier Science Ltd. All rights reserved.

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Finite element mesh superposition method applied to local stress analysis of interphase of composite joints

Naoki Takano, Masaru Zako, Toru Okazaki, Futoshi Kubo

Materials Science Research International 2   219 - 224 2001.05

Research paper (scientific journal), Joint Work, Accepted

均質化法による編物強化熱可塑性プラスチックの深絞り成形解析とその検証

高野 直樹, 大西慶弘, 西藪和明, 座古勝

材料 50 ( 5 ) 461 - 467 2001.05

Research paper (scientific journal), Joint Work, Lead author, Accepted

繊維強化複合材料のミクロ構造に基づく樹脂透過性の３次元評価

高野直樹, 寺田賢二郎, 座古勝

材料 50 ( 5 ) 488 - 494 2001.05

Research paper (scientific journal), Joint Work, Accepted

Computational method for homogenization of heterogeneous materials with voxel element modeling of their microstructures

Naoki Takano, Masaru Zako, Futoshi Kubo, Keiichi Kimura

Materials Science Research International 2   66 - 71 2001.05

Research paper (scientific journal), Joint Work, Lead author, Accepted

重合メッシュ法による不均質体のミクロ応力解析

高野 直樹, 座古勝

日本機械学会論文集(A編) 67 ( 656 ) 603 - 610 2001.04

Research paper (scientific journal), Joint Work, Lead author, Accepted

Efficient modeling of microscopic heterogeneity and local crack in composite materials by finite element mesh superposition method

Naoki Takano, Masaru Zako, Toru Okazaki

JSME International Journal, Series A 44 ( 4 ) 602 - 609 2001

Research paper (scientific journal), Joint Work, Lead author, Accepted,  ISSN  13447912

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The finite element mesh superposition method is applied to the two-dimensional crack problem of composite materials. The microscopic heterogeneity involved in the composite materials is modeled by the fixed grid model. On this global mesh, a local mesh that considers the local crack is superimposed without taking care of the matching of nodes and elements of both meshes. The use of the fixed grid model for the global mesh can reduce the time and efforts for the mesh generation to express the complex heterogeneous microstructures. Also it makes the computation and the implementation of the finite element mesh superposition method very easy. The accuracy was verified by comparing with the theory and the calculation by the conventional fine mesh.

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均質化法によるテキスタイル複合材料の樹脂浸透係数の評価

高野直樹, 寺田賢二郎, 座古勝, 吉岡智美

日本複合材料学会誌 26 ( 5 ) 171 - 178 2000.05

Research paper (scientific journal), Joint Work, Lead author, Accepted