論文 - 高野　直樹

Two-Dimensional Quantitative Analysis of Preferential Alignment of BAp c-axis for Isolated Human Trabecular Bone using Microbeam X-ray Diffractometer with Transmission Optical System

高野 直樹

Materials Transactions 48 （ 3 ） 343-347 2007年

研究論文（学術雑誌）, 共著, 査読有り

HMS採血ポンプ用新型バイモルフ圧電アクチュエータの提案

上辻靖智・長倉秀幸・川原慎太郎・黄輝心・槌谷和義・山本英毅・高野直樹・仲町英治

材料 56 （ 5 ） 477-482 2007年

研究論文（学術雑誌）, 共著, 査読有り

An Iterative Solver Applied to Strongly Coupled Piezoelectric Problems of Porous Pb(Zr,Ti)O3 with Nondestructive Modelling of Microstructure

高野 直樹

Modelling and Simulation in Materials Science and Engineering 15 （ 6 ） 597-617 2007年

研究論文（学術雑誌）, 共著, 査読有り

Multi-scale stress analysis of trabecular bone considering trabeculae morphology and biological apatite crystallite orientation

Kawagai M., Takano N., Nakano T., Asai M.

Zairyo/Journal of the Society of Materials Science, Japan （Zairyo/Journal of the Society of Materials Science, Japan）  55 （ 9 ） 874 - 880 2006年09月

ISSN  05145163

　概要を見る

This paper presents the multi-scale stress analysis of trabecular bone by the homogenization method bridging nano-micro-macro scales. Three-dimensional microstructure of trabeculae is obtained by the X-ray CT and the image-based modeling technique. Biological apatite (BAp) crystallite orientation is considered in the microstructure model by means of the anisotropic mechanical properties. The c-axis of BAp is set up as the maximum principal stress direction under the long term macroscopic stress condition. These properties are automatically assigned to each voxel element. To determine appropriately the microstructure model, the trabeculae morphology is analyzed and quantified as the trabecular density distribution. The proposed method is applied to pig's femur. It was revealed by the morphology analysis and homogenized macroscopic properties that the trabecular bone has plate-like characteristics. The predicted anisotropic level of the macroscopic properties was quantitatively coincident with the measured value by the X-ray diffraction analysis.

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Image-based multi-scale modelling strategy for complex and heterogeneous porous microstructures by mesh superposition method

高野 直樹

Modelling and Simulation in Materials Science and Engineering （Modelling and Simulation in Materials Science and Engineering）  14 （ 1 ） 53-69 - 69 2006年

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  09650393

　概要を見る

This study is focused on the multi-scale modelling strategy for complex and heterogeneous microstructures of real materials by automatic image-based modelling and finite element mesh superposition method. The synergetic application of the conventional asymptotic homogenization method and the authors' mesh superposition method has been proposed to obtain the microscopic responses under high gradient of macroscopic fields at the macroscopic crack tip and/or interface, for instance. For complex and random microstructures, automatic image-based voxel meshing by means of x-ray CT is commonly required; however, it cannot always adapt to the mathematical theory of microscopic modelling in the mesh superposition method. Therefore, a modelling technique for mesh refinement is proposed in this paper using additional elements for insulation in consideration of the theoretical background of the mesh superposition method. In this paper, we provide the modelling procedure and its theoretical consideration of mesh refinement for flexible modelling of real materials. To demonstrate the technique, a numerical example of a porous ceramic component with random microstructure and macroscopic crack is illustrated. © 2006 IOP Publishing Ltd.

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生体硬組織の高分解能イメージベース・マルチスケールモデリング

高野 直樹

日本計算工学会論文集 Paper No.20060017 2006年

研究論文（学術雑誌）, 共著, 査読有り

海綿骨の骨梁モルフォロジーと生体アパタイト結晶配向性を考慮したマルチスケール応力解析

高野 直樹

材料 55 （ 9 ） 874-880 2006年

研究論文（学術雑誌）, 単著, 査読有り

均質化法による多孔質圧電材料のイメージベース・マルチスケール解析

高野 直樹

材料 55 （ 12 ） 1111-1116 2006年

研究論文（学術雑誌）, 共著, 査読有り

Finite element analysis of fiber-reinforced fixed partial dentures

高野 直樹

Dental Materials Journal （Dental Materials Journal）  24 （ 2 ） 275-279 - 279 2005年

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  02874547

　概要を見る

Two-dimensional finite element models were created for a three-unit posterior fixed partial denture. An experimental resin-impregnated glass fiber was used as the fiber-reinforced composite (FRC) for the framework. The FRC was evaluated using varying combinations of position and thickness, alongside with two types of veneering composite. A load of 50 N simulating bite force was applied at the pontic in a vertical direction. Tensile stress was examined using a finite element analysis program. Model without FRC showed tensile stress concentrations within the veneering composite on the cervical side of the pontic - from the connector area to the bottom of the pontic. Model with FRC at the top of the pontic had almost the same stress distribution as the model without FRC. Models with 0.4-0.8 mm thick FRC positioned at the bottom of the pontic showed maximum tensile stresses reduced by 4-19% within the veneering composite.

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Stress analysis of endodontically treated anterior teeth restored with different types of post material

高野 直樹

Dental Materials Journal （Dental Materials Journal）  25 （ 1 ） 145-150 - 150 2005年

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  02874547

　概要を見る

Finite element analysis was performed to evaluate stress distribution in maxillary central incisors treated endodontically and restored with a post and an all-ceramic crown. Tensile stress at tooth root was analyzed using two-dimensional finite element models with different post diameters and lengths. One post length was 1/3 of the root (short), while the other was 2/3 of the root (long); one post diameter was 1/3 of the root (narrow), while the other was 2/3 of the root (wide). The following combinations were used for posts and cores: gold alloy cast post and core, commercial stainless steel post and resin core, and fiber post and resin core. Results showed that the fiber post produced less stress on the root dentin around the post tip than did the metal posts. This finding thus suggested that to reduce the stresses that cause root fracture, a long, thin fiber post should be used.

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Macro-micro stress analysis of porous ceramics by homogenization method

Ikeda Y., Nagano Y., Kawamoto H., Takano N.

Ceramic Engineering and Science Proceedings （Ceramic Engineering and Science Proceedings）  25 （ 3 ） 177 - 182 2004年12月

ISSN  01966219

　概要を見る

The 3-D image modeling of the porous alumina was obtained by X-ray CT, and microscopic volume elements were obtained from it. Porous alumina including spherical pores 60μm and 20μm in diameter with porosities 7.05% and 1.76% were studied by homogenization method, which calculated homogenized elastic constants for the microscopic volumes. These constants were applied to simulate 4-point bending tests and to analyze macroscopic stress distributions coupled with FEM calculation. Microscopic stress distributions were analyzed using the FEM result. The maximum microscopic stress concentration near a spherical pore were about 2 times higher than the average stress one.

3D modeling of porous ceramics by high-resolution X-ray CT for stress analyses

Ikeda Y., Nagano Y., Kawamoto H., Takano N.

Key Engineering Materials （Key Engineering Materials）  270-273 （ I ） 28 - 34 2004年11月

ISSN  10139826

　概要を見る

Porous ceramic materials are in widespread use and continue to be developed as the key materials for many industrial fields. The mechanical properties of these porous materials are very sensitive to their 3-dimensional structures. It is very important to analyze such materials taking into account their 3-dimensional morphology of the pore structure. An image-based modeling method using high resolution 3-dimensional computed tomography (CT) was developed, which makes it possible to reconstruct the complicated porous structures of porous ceramics nondestructively. From the 3-dimensional CT data, binary-processed images can be obtained and a voxel mesh computational analysis was carried out with a homogenization method, from which macroscopic and microscopic stress distribution for porous ceramics were possible to be calculated and visualized. From the 3-D CT image, a local microscopic model of the porous alumina was analyzed using voxel mesh method of mathematical homogenization method. Using the data the microscopic local stress distribution of the model was obtained.

Digital image-based analysis of morphology for porous materials

Takano N., Tsujimura K.

Nippon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A （Nippon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A）  70 （ 6 ） 787 - 793 2004年06月

ISSN  03875008

　概要を見る

The porous material is one of the promising functional materials, and its macroscopic properties are strongly dependent on the microscopic morphology. To study the correlation between the microscopic heterogeneity and the macroscopic properties, a novel digital image-based analysis methodology is proposed in this paper, which consists of high resolution X-ray CT, digital image-based modeling, multi-scale stress analysis and geometrical morphology analysis. The proposed morphology analysis enables us to predict the microscopic stress concentration for spherical porous ceramics considering the heterogeneous dispersion of spherical pores and the macroscopic loading condition. The heterogeneity can be analyzed geometrically for very huge data with approximately 58 million voxel elements quickly. The morphology analysis is helpful for the multi-scale modeling and microscopic stress evaluation. The microscopic stress distribution is also discussed in association with the random heterogeneity for ceramics with open pores and with high porosity ratios.

Microscopic stress analysis at crack tip in heterogeneous media by multi-scale method

Takano N., Okuno Y.

Nippon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A （Nippon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A）  70 （ 4 ） 525 - 531 2004年04月

ISSN  03875008

　概要を見る

In the development of various advanced materials by controlling their heterogeneous microstructures, there is a growing need for the multi-scale analysis. There have been many studies on the correlation between the heterogeneous microstructure and the macroscopic properties mainly using the asymptotic homogenization method with the help of the finite element method. Although the consideration of fracture origin in components such as interface crack is important in the multi-scale stress analysis, it was impossible to calculate the microscopic stress under high gradient of macroscopic strain/stress field at the crack tip. Furthermore, the representative dimension of the fracture origin lies between the microscopic scale and the macroscopic one. Hence, this paper proposes a novel three-scale computational method that employs both the homogenization method and the enhanced mesh superposition method to study the correlation among microstructure, component and fracture origin simultaneously. An equation solver for large-scale 3 D analysis by the mesh superposition method is also presented. A demonstrative 3 D example of porous thin film with interface crack, whose finite element model has approximately 78 thousand solid elements, is shown.

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

日本機械学会論文集A編 70 （ 692 ） 525-531 2004年

研究論文（学術雑誌）, 共著, 査読有り

多孔体モルフォロジーのディジタルイメージベース・アナリシス

高野 直樹

日本機械学会論文集A編 70 （ 694 ） 787-793 2004年

研究論文（学術雑誌）, 共著, 査読有り

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

高野 直樹

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

研究論文（学術雑誌）, 共著, 査読有り,  ISSN  00207683

　概要を見る

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

高野 直樹

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

共著, 査読有り,  ISSN  02663538

　概要を見る

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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Multi-Scale Finite Element Analysis for Joint Members of Heterogeneous Dissimilar Materials with Interface Crack

Takano N., Zako M., Okuno Y.

Zairyo/Journal of the Society of Materials Science, Japan （Zairyo/Journal of the Society of Materials Science, Japan）  52 （ 8 ） 952 - 957 2003年08月

ISSN  05145163

　概要を見る

In the last decade, a multi-scale computational method using the asymptotic homogenization method with the help of the finite element method has been intensively studied and applied to various advanced materials such as fiber reinforced composite materials and porous materials. It enables us to analyze the overall behaviors of structures considering the microscopic heterogeneity, where there is a large gap between the macro-scale and the micro-scale within the framework of continuum mechanics. However, no literature can be found that studied the joint or laminated members of heterogeneous dissimilar materials with interface crack. Due to the non-periodic condition at the interface and the existence of crack, the homogenized material modeling is of no use. Hence, an enhanced finite element mesh superposition method is employed to solve the two-scale problem. Two independent meshes, i. e., the global mesh and the local mesh, are used. The global mesh represents the joint or laminated members from the macroscopic viewpoint using the homogenized model. The local mesh is used to consider the heterogeneous microstructure of the material as well as the crack and superimposed onto the global mesh. The formulation, numerical accuracy and effectiveness of the proposed multi-scale method are presented in this paper.

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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

日本複合材料学会誌 29 （ 1 ） 17-23 2003年

研究論文（学術雑誌）, 共著, 査読有り