Updated on 2024/03/18

写真a

 
OKUMURA, Dai
 
Organization
Graduate School of Engineering Mechanical Systems Engineering 1 Professor
Graduate School
Graduate School of Engineering
Undergraduate School
School of Engineering Mechanical and Aerospace Engineering
Title
Professor

Degree 1

  1. Dr. of Eng. ( Nagoya University ) 

Research Interests 19

  1. and Cellular solids

  2. Buckling bifurcation

  3. Dislocations

  4. Strain gradient

  5. Crystal plasticity

  6. Homogenization theory

  7. Gels

  8. 転位

  9. 膨潤

  10. 結晶塑性

  11. 均質化理論

  12. 分岐座屈

  13. 不安定

  14. パターン変態

  15. セル状材料

  16. ゲル材料

  17. エラストマー

  18. ひずみこう配

  19. Soft materials

Research Areas 3

  1. Others / Others  / Machine Material/Material Mechanics

  2. Others / Others  / 計算材料力学

  3. Manufacturing Technology (Mechanical Engineering, Electrical and Electronic Engineering, Chemical Engineering) / Mechanics of materials and materials

Current Research Project and SDGs 1

  1. 固体力学のマルチスケール計算シミュレーション

Research History 9

  1. Nagoya University   Department of Mechanical Systems Engineering   Professor   D.ENG.

    2019.4

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    Country:Japan

  2. Nagoya University   Graduate School of Engineering Mechanical Systems Engineering   Professor

    2019.4

  3. Nagoya University   Associate professor

    2018.4 - 2019.3

  4. 大阪大学大学院   工学研究科機械工学専攻   准教授

    2016.4 - 2018.3

  5. 名古屋大学大学院工学研究科計算理工学専攻准教授

    2012.4 - 2016.3

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    Country:Japan

  6. 名古屋大学大学院工学研究科計算理工学専攻講師

    2007.10

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    Country:Japan

  7. 名古屋大学大学院工学研究科計算理工学専攻助教

    2007.4 - 2007.9

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    Country:Japan

  8. 名古屋大学大学院工学研究科計算理工学専攻助手

    2004.4 - 2007.3

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    Country:Japan

  9. 名古屋大学大学院工学研究科マイクロシステム工学専攻助手

    2003.4 - 2004.3

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    Country:Japan

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Education 2

  1. Nagoya University   Graduate School, Division of Engineering

    - 2003

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    Country: Japan

  2. Nagoya University

    - 2003

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    Country: Japan

Professional Memberships 8

  1. 日本機械学会

  2. IACM(The International Association for Computational Mechanics)

  3. JACM(The Japan Association for Computational Mechanics)

  4. ASME

  5. 日本計算数理工学会

  6. 日本計算工学会

  7. 日本材料学会

  8. 日本機械学会

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Committee Memberships 23

  1. 日本機械学会材料力学部門若手シンポジウム実行委員会   委員  

    2014.7   

  2. 日本機械学会論文集編集委員会   材料力学部門アソシエイトエディタ  

    2014.4   

  3. 日本計算工学講演会実行委員会   BPAWG委員主査  

    2015.1   

  4. 日本計算工学講演会実行委員会   BPAWG委員  

    2012.1 - 2014.12   

  5. 日本機械学会材料力学部門   運営委員  

    2011.4 - 2014.3   

  6. 日本機械学会計算力学部門   広報幹事  

    2011.4 - 2013.3   

  7. 日本材料学会塑性工学部門   庶務幹事  

    2011.4 - 2013.3   

  8. 名古屋大学工学系同窓会   会計  

    2011.4 - 2013.3   

  9. 名古屋大学機械系同窓会東山会   会計理事  

    2010.5 - 2014.4   

  10. International Journal of Solids and Structures   Editorial Advisory Board Member  

    2023.5   

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    Committee type:Academic society

  11. JSME   Fellow  

    2023.5   

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    Committee type:Academic society

  12. 日本機械学会   計算力学部門表彰委員会副委員長  

    2018.4 - 2019.3   

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    Committee type:Academic society

  13. 日本計算数理工学会   論文集編集幹事  

    2017.4   

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    Committee type:Academic society

  14. 日本機械学会   計算力学部門部門幹事  

    2017.4 - 2018.3   

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    Committee type:Academic society

  15. 日本計算数理工学会   理事  

    2016.4   

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    Committee type:Academic society

  16. 日本機械学会   計算力学部門部門副幹事  

    2016.4 - 2017.3   

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    Committee type:Academic society

  17. 日本材料学会東海支部   幹事  

    2015.4   

  18. 日本計算工学会   ベストペーパーアワード主査  

    2015.4 - 2017.3   

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    Committee type:Academic society

  19. ASME McMAT 2015   Session Organizer  

    2015.4 - 2015.7   

  20. Plasticity, Damage and Fracture 2016   MS organizer  

    2015.3 - 2016.1   

  21. Plasticity, Damage and Fracture 2016   International Organizing Committee  

    2015.3 - 2016.1   

  22. 日本計算工学会   代表会員  

    2014.4   

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    Committee type:Academic society

  23. 日本機械学会   論文集材料力学部門アソシエイトエディター  

    2014.4 - 2020.3   

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    Committee type:Academic society

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Awards 8

  1. 業績賞

    2019.9   日本機械学会計算力学部門  

  2. JACM Young Investigator Award

    2013.12   Japane Association for Computational Mechanics  

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    Country:Japan

  3. 日本材料学会学術奨励賞

    2011.5   日本材料学会  

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    Country:Japan

  4. 日本機械学会奨励賞(研究)

    2011.4   日本機械学会  

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    Country:Japan

  5. 平成19年度日本機械学会 材料力学部門 優秀講演表彰

    2007.12   日本機械学会  

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    Country:Japan

  6. 平成18年度日本機械学会 計算力学部門 優秀講演表彰

    2007.3   日本機械学会  

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    Country:Japan

  7. 日本機械学会賞(論文)

    2004  

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    Country:Japan

  8. 日本材料学会優秀講演発表賞

    2003  

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    Country:Japan

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Papers 169

  1. Bio‐Inspired Instability‐Induced Hierarchical Patterns Having Tunable Anisotropic Wetting Properties Reviewed

    So Nagashima, Ko Suzuki, Seishiro Matsubara, Dai Okumura

    Advanced Materials Interfaces   Vol. 10 ( 14 )   2023.5

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    Authorship:Last author   Publishing type:Research paper (scientific journal)  

    DOI: 10.1002/admi.202300039

    Web of Science

    Scopus

  2. Mechanical nonreciprocity in a uniform composite material Reviewed

    Xiang Wang, Zhihao Li, Shuxu Wang, Koki Sano, Zhifang Sun, Zhenhua Shao, Asuka Takeishi, Seishiro Matsubara, Dai Okumura, Nobuyuki Sakai, Takayoshi Sasaki, Takuzo Aida, Yasuhiro Ishida

    Science   Vol. 380 ( 6641 ) page: 192 - 198   2023.4

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1126/science.adf1206

    Web of Science

    Scopus

    PubMed

  3. Self-Wrinkling in Polyacrylamide Hydrogel Bilayers Reviewed

    So Nagashima, Naoki Akamatsu, Xiangfu Cheng, Seishiro Matsubara, Shohei Ida, Hiro Tanaka, Makoto Uchida, Dai Okumura

    Langmuir   Vol. 39 ( 11 ) page: 3942 - 3950   2023.3

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    Authorship:Last author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Chemical Society (ACS)  

    DOI: 10.1021/acs.langmuir.2c03264

    Web of Science

    Scopus

    PubMed

  4. Diversity of the bifurcations and deformations on films bonded to soft substrates: Robustness of the herringbone pattern and its cognate patterns Reviewed International journal

    Shotaro Kikuchi, Seishiro Matsubara, So Nagashima, Dai Okumura

    Journal of the Mechanics and Physics of Solids   Vol. 159   page: 104757 - 104757   2022.2

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    Authorship:Last author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Elsevier {BV}  

    DOI: 10.1016/j.jmps.2021.104757

    Web of Science

    Scopus

  5. Modeling of cyclic hardening and evaluation of plastic strain range in the presence of pre-loading and ratcheting Reviewed

    Nobutada Ohno, Hisashi Nakamoto, Yusuke Morimatsu, Dai Okumura

    INTERNATIONAL JOURNAL OF PLASTICITY   Vol. 145   2021.10

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    Authorship:Last author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:PERGAMON-ELSEVIER SCIENCE LTD  

    An extended evolution equation of cyclic hardening is proposed to include the effect of maximum plastic strain due to pre-loading and ratcheting. A set of extended evolution equations is also proposed for a plastic strain surface to properly evaluate the cyclic plastic strain range in the presence of pre-loading and ratcheting. These extensions are verified by performing uniaxial cyclic experiments of 316 stainless steel at 600 degrees C. The experiments are accurately simulated using a constitutive model with the extensions in addition to the resetting scheme of the plastic strain surface recently proposed by the authors. The extension for the plastic strain surface allows fairly good simulation of the experiments without recourse to the resetting scheme if the strain range does not markedly decrease with the number of cycles. The extended equations are further used to discuss the effect of maximum plastic strain considering previous experiments.

    DOI: 10.1016/j.ijplas.2021.103074

    Web of Science

    Scopus

  6. Bifurcation and deformation during the evolution of periodic patterns on a gel film bonded to a soft substrate Reviewed

    Hiroaki Miyoshi, Seishiro Matsubara, Dai Okumura

    JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS   Vol. 148   page: 104272 - 104272   2021.3

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    Authorship:Last author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:PERGAMON-ELSEVIER SCIENCE LTD  

    In this study, we investigate the bifurcation and deformation during the evolution of periodic patterns on a gel film bonded to a soft substrate. 3D finite element analysis is performed using an inhomogeneous field theory for polymeric gels. Step-by-step eigenvalue buckling analysis is conducted to explore not only the first bifurcation, but also sequential bifurcations on bifurcated paths. When the hexagonal dimple mode occurs as the first bifurcation, the second bifurcation consists of rectangular checkerboard modes in three symmetric directions. The resulting deformation patterns are in good agreement with experiments and, surprisingly, are analogous to the in-plane buckling behavior of hexagonal honeycombs. Uniaxial, biaxial, and equibiaxial (flower-like) patterns are produced by the periodic arrangements of distorted dimples. The third and fourth bifurcations cause the coalescence of the selected dimples. This reveals the occurrence of the rectangular checkerboard modes at the second bifurcation to be the missing link in the pattern evolution from hexagonal dimples to herringbone and labyrinth patterns.

    DOI: 10.1016/j.jmps.2020.104272

    Web of Science

    Scopus

  7. Experiments and modeling of the viscoelastic behavior of polymeric gels Reviewed International coauthorship

    Nikola Bosnjak, Siva Nadimpalli, Dai Okumura, Shawn A. Chester

    JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS   Vol. 137   2020.4

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:PERGAMON-ELSEVIER SCIENCE LTD  

    A polymeric gel is a cross-linked polymer network swollen with a solvent. Also, as is well known many polymeric materials exhibit viscoelastic behavior in their mechanical response, In this work, we report on our recent experimental observations and theoretical modeling involving the change in the viscoelastic response of the polymeric material VHB caused by equilibrium swelling in multiple solvents. To characterize this change, we have developed an experimental procedure that includes mechanical testing when virgin, free swelling, mechanical testing when swollen, and mechanical testing after drying. A model is used to help interpret the experimental results. The key finding of this work is that our results indicate that the viscoelastic behavior of initially dry VHB, reversibly, becomes essentially hyperelastic when swollen to equilibrium in multiple solvents. (C) 2019 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.jmps.2019.103829

    Web of Science

    Scopus

  8. Computational and physical aspects for the occurrence of crease in an elastomer under general loading conditions Reviewed International journal

    Matsubara, S; Ogino, A; Nagashima, S; Okumura, D

    INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES   Vol. 288   2024.2

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    Authorship:Last author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:International Journal of Solids and Structures  

    We study the occurrence of crease in an elastomer under three loading conditions from both computational and physical points of view. A two-dimensional finite element analysis, including a perturbation force-based approach, is performed to detect the stable creased state, where the crease formation is completed. A mesh convergence study for the energy release and crease depth in the creased state provides a guideline for the finite element mesh requisite for predicting the occurrence of crease. We also visualize the mesh convergence for the critical creasing onset by plotting the set of compressive strain and mesh resolution at the point where the energy release is zero. In addition, the present evaluation method of the surface tension using the energy release and surface area change for an elastomer with a traction-free surface yields a good prediction for the creasing onset delayed by surface tension without additional numerical implementations or adjustment parameters. This facilitates the comprehensive study of the creasing onset delayed by the surface tension under general loading conditions. The results reveal that tensile deformation in the out-of-plane direction encourages the retardation of the creasing onset via the extension of the width and the energy emission. We further demonstrate that energetically preferential crease interval can be used to evaluate the spacing between creases delayed by moderate surface tension.

    DOI: 10.1016/j.ijsolstr.2023.112610

    Web of Science

    Scopus

  9. ノンレシプロカルゲルの円筒押込み大変形解析 Reviewed

    野々垣翔真,松原成志朗,永島 壮,奥村 大

    計算数理工学論文集   Vol. 23   page: 123 - 128   2023.11

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    Authorship:Last author, Corresponding author   Language:Japanese   Publishing type:Research paper (scientific journal)  

  10. クリースの発達過程に対する影響因子の調査 Reviewed

    石田竜也,永島 壮,松原成志朗,奥村 大

    計算数理工学論文集   Vol. 23   page: 143 - 148   2023.11

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    Authorship:Last author   Language:Japanese   Publishing type:Research paper (scientific journal)  

  11. 均質化解析によるノンレシプロカルゲルの引張・圧縮非対称性評価 Reviewed

    布施卓馬,松原成志朗,永島 壮,奥村 大

    計算数理工学論文集   Vol. 23   page: 137 - 142   2023.11

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    Authorship:Last author   Language:Japanese   Publishing type:Research paper (scientific journal)  

  12. Self-Wrinkling in Polyacrylamide Hydrogel Bilayers Reviewed

    So Nagashima, Naoki Akamatsu, Xiangfu Cheng, Seishiro Matsubara, Shohei Ida, Hiro Tanaka, Makoto Uchida, Dai Okumura

    Langmuir     2023.3

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    Authorship:Last author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: https://doi.org/10.1021/acs.langmuir.2c03264

  13. Evaluation of the Effects of Cross-Link Density and Swelling Ratio on Loading-Unloading Response in Large Strain Range of Hydrogels Reviewed

    Syunpei Morita, Makoto Uchida, Yoshihisa Kaneko, Dai Okumura, Hiro Tanaka, Shohei Ida

    Advanced Experimental Mechanics   Vol. 7 ( 0 ) page: 90 - 96   2022.8

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:The Japanese Society for Experimental Mechanics  

    <p>Hydrogel contains a large amount of solvent such as water inside a three-dimensional molecular chain network structure. The content of the solvent changes during the swelling and drying processes of the hydrogel. The mechanical properties of the gel significantly change depending on the solvent content. In this study, the effects of the cross-link density and swelling ratio on the nonlinear mechanical responses of hydrogel were investigated by the cyclic tensile test. To evaluate the irreversible deformation of the hydrogel, we performed the one-time and stepwise loading-unloading tests. The stress-strain curves for the loading and unloading process obtained from the crosshead displacement were different owing to the sliding between chuck and specimen. In contrast, they were consistent for all the experimental conditions when the strain was evaluated by the digital image correlation method. Therefore, the hydrogel showed the less-rate-dependent reversible deformation from small to large strain range. Furthermore, obtained results were compared with the theoretical model based on the molecular chain network model with swelling effect. Although the model could represent the nonlinear increase in the stress during the tensile test and the decrease in the stiffness owing to the swelling, the model results were not consistent with the experimental results. Experimental and numerical results indicate that the improvement of the mechanical model is necessary based on the less-rate-dependent reversible deformation mechanisms of the hydrogel.</p>

    DOI: 10.11395/aem.7.0_90

    CiNii Research

  14. Surface Instabilities of Soft Materials Invited

    OKUMURA Dai

    Journal of the Society of Materials Science, Japan   Vol. 71 ( 6 ) page: 555   2022.6

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    Authorship:Lead author, Last author, Corresponding author   Language:Japanese   Publisher:The Society of Materials Science, Japan  

    DOI: 10.2472/jsms.71.555

    CiNii Research

  15. Finite element analysis for nucleation and propagation of crease in an elastic solid

    Matsubara Seishiro, Hoshi Ryogo, Nagashima So, Okumura Dai

    NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan   Vol. 66 ( 0 ) page: 5   2022

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    Language:Japanese   Publisher:National Committee for IUTAM  

    <p>This study investigates the nucleation and propagation of crease from a V-shaped notch in an elastic solid. Finite element analyses are conducted on an incompressible Neo-Hookean elastic solid. The first crease is induced by a V-shaped notch, whereas the subsequent sequential creases occur as the self-organization induced by previous creases. The crease propagation is regularized at the threshold compressive strain of 0.323 in the case of the global compressive strain <i>ε</i><sub>G </sub><=0.323, while an elastic solid is supercritical in the case of <i>ε</i><sub>G</sub>>0.323. The nonlinear perturbation approach reveals that the periodic distance between creases minimizing total elastic energy is larger than that predicted by self-organization and increases in response to <i>ε</i><sub>G</sub> approaching to 0.323.</p>

    DOI: 10.11345/japannctam.66.0_5

    CiNii Research

  16. リッジパターン変態のプレストレッチ依存性と分岐座屈特性 Reviewed

    松原 成志朗, 永島 壮, 奥村 大

    計算数理工学論文集   Vol. 22   page: 117 - 121   2022

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  17. Implicit rule on the elastic function of a swollen polyacrylamide hydrogel Reviewed

    Ryota Kawai, Hiro Tanaka, Seishiro Matsubara, Shohei Ida, Makoto Uchida, Dai Okumura

    SOFT MATTER   Vol. 17 ( 19 ) page: 4979 - 4988   2021.5

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    Authorship:Last author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:ROYAL SOC CHEMISTRY  

    A full understanding of the elastic properties of hydrogels under swelling is required for their practical application in the chemical and biomedical engineering fields. This is because hydrogels are expected to retain water during mechanical use in moist atmospheres. In the present study, we investigated the relationship between the elastic modulus and the swelling ratio in a specific type of hydrogel (a polyacrylamide gel). The elasticity and swelling data revealed that these two parameters are proportionally related in hydrogels comprising adequate amounts of monomers and crosslinkers. We also demonstrated that this proportional relationship inherently conforms to the linear elastic behaviour predicted by the Flory-Rehner free energy function (the F-R model). The implicit rule is established by the extended F-R model with two scaling exponents. The extended model is capable of representing the irregular elasticity of swollen gels formed from low- or high-molecular-weight polymers.

    DOI: 10.1039/d1sm00346a

    Web of Science

    Scopus

    PubMed

  18. Effects of initial imperfection and mesh resolution on wrinkle and crease analyses Reviewed

    HOSHI Ryogo, MIYOSHI Hiroaki, MATSUBARA Seishiro, OKUMURA Dai

    Transactions of the JSME (in Japanese)   Vol. 87 ( 898 ) page: 21 - 00045-21-00045   2021.5

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    Authorship:Last author   Language:Japanese   Publisher:The Japan Society of Mechanical Engineers  

    <p>This study investigates the effects of initial imperfection and mesh resolution on the wrinkling and creasing. Finite element analyses are conducted to simulate compression behaviors of an incompressible Neo-Hookean elastic plane with a V-shaped notch as initial imperfection, so that the occurrences and evolutions of wrinkle and crease are evaluated quantitatively. As a result, it is demonstrated that the origins of wrinkle and crease can be determined by the overall and local strains even for the introduction of a V-shaped notch. Further, we illustrate that the converged specific local strain with respect to the increase of mesh resolution almost coincides with the condition of the occurrence of wrinkle (i.e., <i>ε</i><sub>w</sub> = 0.456) when the depth of a V-shaped notch is sufficiently small. We also show that the sizes of wrinkle and crease do not converge due to strain localization around a V-shaped notch. In the investigation of pattern evolutions about initial imperfection, we illustrate that two kinds of pattern evolution can be comprehensively discussed by varying the depth of a V-shaped notch, so that the condition of the occurrence of crease can be organized by the sharpness of a V-shaped notch.</p>

    DOI: 10.1299/transjsme.21-00045

    CiNii Research

  19. ヘリンボン及びトリプルジャンクションパターンの発達に対する影響因子解析 Reviewed

    奥村 大

    計算数理工学論文集   Vol. 21   page: 51 - 56   2021

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  20. A general expression for linearized properties of swollen elastomers undergoing large deformations Reviewed International coauthorship

    Dai Okumura, Hironori Kawabata, Shawn A. Chester

    JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS   Vol. 135   2020.2

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:PERGAMON-ELSEVIER SCIENCE LTD  

    In this study, we develop a general expression for the linearized properties of swollen elastomers undergoing large deformations. The free energy function of swollen elastomers is assumed to obey the Frenkel-Flory-Rehner hypothesis, i.e., the elastic and mixing contributions are additive. The elastic strain energy is not assumed to have a particular form but is assumed only to be a function of a set of strain-invariants. A linearization procedure is used to obtain the general expression for the Young's modulus and Poisson's ratio under an arbitrary base state. The derived expression includes a characteristic term, which has the ability to describe a transient state between the extreme states prescribed by two distinct conditions. The verification is performed by estimating the shear modulus and considering the original Flory-Rehner framework. In addition, to show the usefulness, an extended Gent model is examined to elucidate the interactions between limiting chain extensibility and the second strain-invariant. (C) 2019 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.jmps.2019.103805

    Web of Science

    Scopus

  21. The effect of water content on viscoelastic properties of polyacrylamide hydrogels

    TAKASHIMA Akira, MATSUBARA Seishiro, IDA Shohei, TANAKA Minoru, UCHIDA Makoto, OKUMURA Dai

    The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2020 ( 0 ) page: J03127   2020

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    Language:Japanese   Publisher:The Japan Society of Mechanical Engineers  

    DOI: 10.1299/jsmemecj.2020.j03127

    CiNii Research

  22. Finite Element Implementation of Gent-Gent Hyperelastic Model for Swollen Elastomers

    KIKUCHI Shotaro, MIYOSHI Hiroaki, MATSUBARA Seishiro, OKUMURA Dai

    The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2020 ( 0 ) page: J03139   2020

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    Language:Japanese   Publisher:The Japan Society of Mechanical Engineers  

    <p>In this study, we conduct finite element implementation of a Gent-Gent hyperelastic model for swollen elastomers. To this end, an inhomogeneous field theory for swollen elastomers is extended using the Gent-Gent model, which includes the effects of limiting chain extensibility and the second strain-invariant. The extended theory is implemented into a commercial finite element package using a user-defined material subroutine. The inflation of a spherical balloon made of swollen elastomers is computed and the results are verified with an analytical prediction.</p>

    DOI: 10.1299/jsmemecj.2020.j03139

    CiNii Research

  23. Finite element implementation of Gent-Gent hyperelastic model for swollen elastomers

    KIKUCHI Shotaro, MIYOSHI Hiroaki, KAWABATA Hironori, OKUMURA Dai

    The Proceedings of Conference of Tokai Branch   Vol. 2020.69 ( 0 ) page: 120   2020

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    Language:Japanese   Publisher:The Japan Society of Mechanical Engineers  

    DOI: 10.1299/jsmetokai.2020.69.120

    CiNii Research

  24. Finite element implementation of Gent-Gent hyperelastic model for swollen elastomers Reviewed

    KIKUCHI Shotaro, MIYOSHI Hiroaki, MATSUBARA Seishiro, OKUMURA Dai

    Transactions of the JSME (in Japanese)   Vol. 86 ( 890 ) page: 20 - 00233-20-00233   2020

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    Authorship:Last author   Language:Japanese   Publisher:The Japan Society of Mechanical Engineers  

    <p>In this study, we conduct finite element implementation of a Gent-Gent hyperelastic model for swollen elastomers. To this end, an inhomogeneous field theory for swollen elastomers is extended using the Gent-Gent model, which includes the effects of limiting chain extensibility and the second strain-invariant. The extended theory is implemented into a commercial finite element package using a user-defined material subroutine. The accuracy of the implementation is verified by analyzing Young's modulus and Poisson's ratio of swollen elastomers undergoing large deformations. Further, the inflation of a spherical balloon made of swollen elastomers is computed as an example. The results are verified with an analytical prediction and demonstrate the inflation behavior of swollen elastomers.</p>

    DOI: 10.1299/transjsme.20-00233

    CiNii Research

  25. Bifurcation analysis of pattern evolution in a stiff gel film

    MIYOSHI Hiroaki, MATUBARA Seishiro, OKUMURA Dai

    The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2020 ( 0 ) page: J02103   2020

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    Language:Japanese   Publisher:The Japan Society of Mechanical Engineers  

    <p>In this study, we perform buckling and postbuckling analysis to invesigate the pattern evolution in a sttiff gel film bonded on a soft substrate. The film and substrate are modeled as the Neo-Hookean solid model. Further, the film is assumed to obey the Flory–Rehner framework for polymeric gels. Since the film swells, the in-plane compressive stresses increases in the film, which causes buckling, i.e., patterns transformation occurs. Finite element analysis is conducted by introducing the Flory–Rehner framework into a user-defined material subroutine (Hong et al., 2009). The step-by-step eigenvalue buckling analysis, which was developed by Okumura et al. (2018), is employed to investigate the onset points and modes of bifurcations. The employment allows us to sequentially trace the first, second and further bifurcations on the bifurcated paths. The obtained results are shown and discussed.</p>

    DOI: 10.1299/jsmemecj.2020.j02103

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  26. Finite element analysis of influential factors in a three dimensional structure assembled from a gel film

    HOSHI Ryogo, MIYOSHI Hiroaki, MATSUBARA Seishiro, OKUMURA Dai

    The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2020 ( 0 ) page: J03140   2020

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    <p>We perform a finite element analysis of gel membrane constrained on a grass substrate to investigate influence factors in a three dimensional structure assembled from a gel film. In-plane compressive stresses cause a three dimensional deformation due to swelling of a gel film. Such a deformation is influenced by attractive force, friction, imperfection and so on. In this study, we, particular, investigate the influence of attractive force by conducting finite element analysis for the Neo-Hookean body. The obtained results are shown to discuss deformation patterns caused in response to different attractive forces.</p>

    DOI: 10.1299/jsmemecj.2020.j03140

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  27. Mechanism analysis of morphology formation from a gel membrane to a three dimensional structure

    HOSHI Ryogo, MIYOSHI Hiroaki, OKUMURA Dai

    The Proceedings of Conference of Tokai Branch   Vol. 2020.69 ( 0 ) page: 121   2020

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    DOI: 10.1299/jsmetokai.2020.69.121

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  28. Analysis of influential factors in 3D structure formation of an anionic polyacrylamide (copolymer) gel film on a glass substrate

    KAWAI Ryota, MATSUBARA Seishiro, IDA Shohei, TANAKA Hiro, UCHIDA Makoto, OKUMURA Dai

    The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2020 ( 0 ) page: J02102   2020

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    DOI: 10.1299/jsmemecj.2020.j02102

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  29. Resetting scheme for plastic strain range evaluation in cyclic plasticity: Experimental verification Reviewed

    Nobutada Ohno, Hisashi Nakamoto, Yusuke Morimatsu, Takeshi Hamada, Dai Okumura

    INTERNATIONAL JOURNAL OF PLASTICITY   Vol. 123   page: 56 - 69   2019.12

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    It has been proposed that a plastic strain surface is reset to a point and re-evolves every cycle to correctly evaluate the plastic strain range under cyclic loading (Ohno et al., 2018b). This resetting scheme has the advantage of providing a definite value for the evolution parameter irrespective of the amounts of cyclic hardening, pre-straining, and ratcheting. In the present study, the resetting scheme was experimentally verified by performing the following three types of uniaxial cyclic tests of 316 stainless steel at 600 degrees C: constant strain range, gradual decrease, and step decrease tests. The gradual decrease tests, a new type of cyclic tests, had gradual strain range reduction with increasing number of cycles in the absence and presence of ratcheting such as found at notch roots. Thus, the effect of the strain range history on cyclic hardening was observed to be weaker than that due to stepwise decreasing the strain range. Using a constitutive model with the resetting scheme enabled good simulation of the cyclic hardening behavior in the gradual decrease tests. Cyclic softening after stepwise decreasing the strain range was also simulated well by extending the evolution equation of cyclic hardening.

    DOI: 10.1016/j.ijplas.2019.07.008

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  30. Evaluation of the effects of cross-linking and swelling on the mechanical behaviors of hydrogels using the digital image correlation method Reviewed

    Makoto Uchida, Tatsuya Sengoku, Yoshihisa Kaneko, Dai Okumura, Hiro Tanaka, Shohei Ida

    SOFT MATTER   Vol. 15 ( 16 ) page: 3389 - 3396   2019.4

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    Experimental evaluation and modeling are important steps in the investigation of the mechanical behaviors of hydrogels in the small- to large-strain range. In this study, the effects of cross-linking and swelling on the true stress-strain response of a specific type of hydrogel (polyacrylamide) were evaluated using a uniaxial tensile test. The development of true strain on the surface of the hydrogel was measured using the digital image correlation method. The specimens with higher cross-link density exhibited a higher initial elastic modulus and earlier orientation hardening. The initial elastic modulus was reduced by the swelling, whereas the orientation hardening occurred in an earlier strain range in the swollen hydrogel. The mechanical responses of the as-prepared and swollen hydrogels with different cross-linker contents were fitted using a non-Gaussian statistical model. The conventional model underestimated the decrease in the elasticity owing to the swelling effect and overestimated the increase in the stress in the large-strain range. The mechanical model was suitably modified to yield an accurate reproduction of the mechanical responses. The proposed model, which was characterized by five material parameters, was found to reproduce the characteristics of the mechanical responses of the as-prepared and swollen hydrogels with different cross-linker contents.

    DOI: 10.1039/c9sm00049f

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    PubMed

  31. Measurements and FEM Analyses of Strain Distribution in Small Sn Specimens with Few Crystal Grains Reviewed International journal

    Takumi Sasaki, Atsushi Yanase, Dai Okumura, Yoshiharu Kariya, Masaaki Koganemaru, Toru Ikeda

    MATERIALS TRANSACTIONS   Vol. 60 ( 6 ) page: 868 - 875   2019

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    Soldering is used to bond a semiconductor chip to a print circuit board (PCB). It is known that Sn, which is the base metal of Pb-free solder, shows remarkable crystal anisotropy. Clarifying the effect of Sn anisotropy on strain distribution is important for lifetime evaluation. The strain distribution in a micro specimen was measured under a tensile test by a digital image correlation method (DICM) with a microscope. Strain distributions were also analyzed by the finite element method with Hill's anisotropic yield criterion and the crystal plasticity finite element analysis (CPFEA) with considering the critical resolves shear stress (CRSS) of each slip system. The deformation of the crystal structure of beta-Sn depends on the size, number, and orientation of crystal grains. The CRSS was noticeably different for each slip system, and the yield stress varied with the orientation of crystal grains. Although the CPFEA without considering strain hardening was effective for predicting deformation within crystal grains, it is necessary to consider the strain hardening of crystals to predict the stress-strain curve of a micro specimen.

    DOI: 10.2320/matertrans.MH201808

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  32. Refinement of Flory-Rehner model and application to dimple pattern transformation analysis

    MIYOSHI Hiroaki, KAWABATA Hironori, OKUMURA Dai

    The Proceedings of Conference of Tokai Branch   Vol. 2019.68 ( 0 ) page: 616   2019

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    DOI: 10.1299/jsmetokai.2019.68.616

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  33. Effects of loading conditions on linear elastic properties of swollen elastomers

    KAWABATA Hironori, OKUMURA Dai

    The Proceedings of The Computational Mechanics Conference   Vol. 2019.32 ( 0 ) page: 237   2019

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    <p>This study investigates the effect of loading conditions on the linear elastic properties of swollen elastomers. We employ the Flory-Rehner theory with the extended Gent model as the elastic strain energy. The interactions of limiting chain extensibility, the second strain-invariant, solvent migration and the loading conditions are analyzed via the Young’s modulus and Poisson’s ratio.</p>

    DOI: 10.1299/jsmecmd.2019.32.237

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  34. Effect of second strain invariant on linear elastic properties of swollen elastomers

    KAWABATA Hironori, OKUMURA Dai

    The Proceedings of Conference of Tokai Branch   Vol. 2019.68 ( 0 ) page: 127   2019

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    DOI: 10.1299/jsmetokai.2019.68.127

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  35. Evolution from a hexagonal dimple pattern of a stiff gel membrane

    MIYOSHI Hiroaki, OKUMURA Dai

    The Proceedings of the Materials and Mechanics Conference   Vol. 2019 ( 0 ) page: OS0234   2019

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    <p>In this study, buckling and postbuckling analysis is performed to investigate the evolution of dimple patterns in a stiff gel membrane constrained on a soft substrate. The film and substrate are modeled as the Neo-Hookean solid model. The film is also assumed to obey the Flory–Rehner framework for polymeric gels. Since the film swells, the in-plane compressive stresses increase in the film, which causes buckling, i.e., pattern transformation occurs. In finite element analysis, a step-by-step eigenvalue buckling analysis is employed to analyze the onset points and modes of buckling. The employment allows us to sequentially trace the first, second and further bifurcations on the bifurcated paths. The obtained results show the pattern transformation process from hexagonal dimples to labyrinths.</p>

    DOI: 10.1299/jsmemm.2019.os0234

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  36. Bifurcation analysis of generation and evolution of dimple patterns in a stiff gel membrane

    OKUMURA Dai, MIYOSHI Hiroaki

    The Proceedings of The Computational Mechanics Conference   Vol. 2019.32 ( 0 ) page: 232   2019

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    <p>In this study, we perform the bifurcation analysis of the generation and evolution of of dimple patterns in a stiff gel membrane constrained on a soft substrate. The film and substrate are modeled as the Neo-Hookean solid model. Further, the film is assumed to obey the Flory–Rehner framework for polymeric gels. Since the film swells, the in-plane compressive stresses increase in the film, which causes buckling, i.e., pattern transformation occurs. Finite element analysis is conducted by introducing the Flory–Rehner framework into a user-defined material subroutine (Hong et al., 2009). The step-by-step eigenvalue buckling analysis, which was developed by Okumura et al. (2018), is employed to investigate the onset points and modes of bifurcation. The employment allows us to sequentially trace the first, second and further bifurcations under the bifurcated paths. The obtained results are shown and discussed.</p>

    DOI: 10.1299/jsmecmd.2019.32.232

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  37. Measurement and numerical analysis with the crystal plasticity for strain in crystal grains of small Sn specimen

    IKEDA Toru, SASAKI Takumi, KOGANEMARU Masaaki, YANASE Atsushi, OKUMURA Dai, KARIYA Yoshiharu

    The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2019 ( 0 ) page: J01102   2019

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    DOI: 10.1299/jsmemecj.2019.j01102

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  38. Analysis of linear elastic properties of gel membranes constrained on a substrate

    KAWABATA Hironori, OKUMURA Dai, OHNO Nobutada

    The Proceedings of the Materials and Mechanics Conference   Vol. 2019 ( 0 ) page: OS1904   2019

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    <p>In this study, we investigate the linear elastic properties of gel membranes constrained on a rigid substrate. To this end, the Flory–Rehner framework for polymeric gels is considered, which is extended by introducing an extended Gent model. The linear perturbation analysis demonstrates the dependence of limiting chain extensibility and the second strain invariant on the in-plane stiffness of gel membranes constrained on a rigid substrate.</p>

    DOI: 10.1299/jsmemm.2019.os1904

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  39. Swelling amount and tensile behavior of hydrogels swollen under compression

    SENGOKU Tatsuya, MORITA Syunpei, UCHIDA Makoto, KANEKO Yoshihisa, OKUMURA Dai, TANAKA Hiro, IDA Shohei

    The Proceedings of the Materials and Mechanics Conference   Vol. 2019 ( 0 ) page: OS1103   2019

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    <p>The effect of swelling on the true stress-strain response of a hydrogel was evaluated using a uniaxial tensile test, and the response was represented by the constitutive equation based on the molecular chain network theory. The experimental results clarified that the initial elastic modulus was reduced by an increase in the degree of swelling. Two different constitutive equations, where the swelling stretch was introduced in different forms, were proposed to predict the effect of swelling. The obtained results of two equations underestimated and overestimated the effect of the swelling on the true stress-strain curve. This result indicates that the mechanical response of the swollen hydrogel can accurately be predicted using the parameter related to the swelling stretch.</p>

    DOI: 10.1299/jsmemm.2019.os1103

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  40. Fundamental observation of growth-induced morphological formation using a hydrogel

    TAKAMI Gakuto, HISHIDA Yushi, OKUMURA Dai, IDA Shohei, TANAKA Hiro, UCHIDA Makoto

    The Proceedings of Conference of Tokai Branch   Vol. 2019.68 ( 0 ) page: 617   2019

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    DOI: 10.1299/jsmetokai.2019.68.617

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  41. Formulation of rate-form constitutive equation for swelling of hydrogel

    UCHIDA Makoto, SENGOKU Tatsuya, MORITA Syunpei, KANEKO Yoshihisa, OKUMURA Dai, TANAKA Hiro, IDA Syouhei

    The Proceedings of The Computational Mechanics Conference   Vol. 2019.32 ( 0 ) page: 226   2019

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    <p>Mechanical and chemical coupling behavior of hydrogel was modeled by formulating the rate-form constitutive equation in which the elastic part of the deformation was introduced into the molecular chain network theory. The time-dependent development of the swelling was represented by the simple power-law with osmotic pressure between the polymer and solvent. The material parameters employed in the proposed model were given by comparing the decrease in the tensile load applied to the hydrogel specimen in the solvent. Finally, the FEM simulation of the buckling behavior owing to the swelling of the hydrogel in the container was performed.</p>

    DOI: 10.1299/jsmecmd.2019.32.226

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  42. Evaluation of influence of crosslinking concentration and swelling time on tensile response of hydrogel

    Sengoku Tatsuya, Uchida Makoto, Kaneko Yoshihisa, Okumura Dai, Tanaka Hiro, Ida Shohei

    The Proceedings of Conference of Kansai Branch   Vol. 2019.94 ( 0 ) page: P004   2019

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    DOI: 10.1299/jsmekansai.2019.94.p004

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  43. Affector analysis in 3D structure development induced by surface instability in gel films

    HISHIDA Yushi, KAWAI Ryota, OKUMURA Dai, IDA Shohei, TANAKA Hiro, UCHIDA Makoto

    The Proceedings of The Computational Mechanics Conference   Vol. 2019.32 ( 0 ) page: 230   2019

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    <p>In this study, we observe three-dimensional (3D) structure formation induced by the surface instability of gel films generated on petri dishes. As the volume swelling ratio of the films increases, surface instability induces wrinkling and creasing, which result in causing the development of the unique 3D structure. The effective factors are discussed.</p>

    DOI: 10.1299/jsmecmd.2019.32.230

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  44. Fundamental observation of swelling-induced morphological formation in gel films on a glass substrate

    KAWAI Ryota, HISHIDA Yushi, OKUMURA Dai, IDA Shohei, TANAKA Hiro, UCHIDA Makoto

    The Proceedings of the Materials and Mechanics Conference   Vol. 2019 ( 0 ) page: OS1104   2019

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    <p>In this study, we conducted the fundamental observation of swelling-induced morphological formation in gel films on a glass substrate. As the swelling ratio increases, pattern transformation occurs in incremental steps. It was found that surface creasing caused a unique pattern transformation, which generated a 3D structure from a 2D gel film.</p>

    DOI: 10.1299/jsmemm.2019.os1104

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  45. ゲル膜のリンクル解析に及ぼす軟質基盤厚さの影響 Reviewed

    奥村 大

    計算数理工学論文集   Vol. 19   page: 31 - 36   2019

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  46. Effects of two scaling exponents on biaxial deformation and mass transport of swollen elastomers Invited Reviewed International journal

    Dai Okumura, Masahiro Mizutani, Hiro Tanaka, Makoto Uchida

    INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES   Vol. 146   page: 507 - 516   2018.10

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    In this study, we investigate the effects of two scaling exponents on the biaxial deformation and mass transport of swollen elastomers. Two scaling exponents are included in an extended version of the Flory Rehner model (Okumura et al., J. Mech. Phys. Solids, 2016); two scaling exponents are used to adjust the swelling effects on the Young's modulus and osmotic pressure of swollen elastomers, resulting in the ability to predict swelling induced strain softening under uniaxial tensile loading. It is found that when biaxial tensile loading is given under stress control, strain softening is accelerated by increasing the biaxial stress ratio, while under strain control, the responses become more complicated, which can be interpreted by considering that Poisson's ratio at equilibrium free swelling can take negative values depending on the two scaling exponents. Further, the effect of the two scaling exponents on mass transport is discussed by analyzing the swelling kinetics of a gel layer constrained on a rigid substrate. (C) 2017 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.ijmecsci.2017.08.042

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  47. Thermo-mechanical cyclic hardening behavior of 304 stainless steel at large temperature ranges: Experiments and simulations Invited Reviewed

    Nobutada Ohno, Ryohei Yamamoto, Dai Okumura

    INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES   Vol. 146   page: 517 - 526   2018.10

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    Thermo-mechanical cyclic experiments on 304 stainless steel were performed at several temperature ranges with T-min (minimum temperature) of 150 degrees C and T-max (maximum temperature) ranging from 350 degrees C to 1000 degrees C. Corresponding isothermal cyclic experiments were also performed at several temperatures. Temperature-history dependent cyclic hardening was thus observed to significantly occur under thermo-mechanical cyclic loading when T-max was around 600 degrees C. In contrast, almost no cyclic hardening occurred when T-max was 1000 degrees C. The observed, thermo-mechanical cyclic hardening behavior was then simulated using a cyclic viscoplastic constitutive model with a cyclic hardening parameter. The simulation focused on the saturated state of cyclic hardening, leading to the following findings. The saturated thermo-mechanical cyclic hysteresis loops were not predicted well by simply taking into account temperature dependence in the cyclic hardening parameter. Then, by assuming the cyclic hardening parameter to be dependent on T-max, the saturated thermo-mechanical hysteresis loops were simulated well. These mean that the cyclic hardening parameter of 304 stainless steel should not change with temperature but depend on T-max in the saturated state of cyclic hardening under thermo-mechanical cyclic loading. (C) 2017 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.ijmecsci.2017.06.018

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  48. Macroscopic out-of-plane auxetic features of a laminated open-cell structure with in-plane negative Poisson's ratios induced by bridging beam components Reviewed

    Suga, K., Tanaka, H., Okumura, D., Shibutani, Y.

    Smart Materials and Structures   Vol. 27 ( 8 )   2018.8

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    DOI: 10.1088/1361-665X/aacd31

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  49. Ultimate swelling described by limiting chain extensibility of swollen elastomers Reviewed International coauthorship

    Dai Okumura, Shawn A. Chester

    INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES   Vol. 144   page: 531 - 539   2018.8

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    In this study, we study ultimate swelling characterized by limiting chain extensibility of swollen elastomers. Limiting chain extensibility is introduced into the Flory Rehner theory using the Arruda-Boyce eight chain model and the Gent phenomenological model. The difference between these models is unified by defining a single scalar function. The inequality derived from this function allows for analysis to provide an ultimate value of swelling ratio. This ultimate value is not exceeded at equilibrium swelling regardless of the set of material constants. Under uniaxial loading at equilibrium swelling, deswelling can occur even in tension. Further, the very large swelling behavior of pH sensitive hydrogels is found to originate from the resistance generated by approaching the ultimate value of swelling ratio.

    DOI: 10.1016/j.ijmecsci.2018.06.011

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  50. Buckling and postbuckling of etching-induced wiggling in a bilayer structure with intrinsic compressive stress Reviewed

    Dai Okumura, Junya Sugiura, Hiro Tanaka, Yoji Shibutani

    INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES   Vol. 141   page: 78 - 88   2018.6

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    In this study, we investigate buckling and postbuckling of etching-induced wiggling in a bilayer structure consisting of mask and masked layers. To show effects of explicit modeling of etching process, two mask masked ridge models with and without etching (Models w/E and w/oE) are analyzed using finite element analysis. The etching process is explicitly introduced via step-by-step eigenvalue buckling analysis. Although Model w/oE predicts a constant value of the critical wavelength of wiggling regardless of the change in ridge width, Model w/E predicts a shorter wavelength depending on the decrease in ridge width and the increase in intrinsic compressive stress in the mask layer. In postbuckling analysis, Model w/oE predicts a monotonic increase in the wiggling amplitude with the constant wavelength, whereas Model w/E predicts saturation of the wiggling amplitude owing to the decreasing wavelength. In the explicit modeling of etching process, the wiggling behavior shows completely opposite tendencies. Dimensional analysis is performed to obtain empirical equations, which are compared with an experiment.

    DOI: 10.1016/j.ijmecsci.2018.03.032

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  51. EFFECT OF CYCLIC HARDENING ON STRESS RELAXATION IN SUS316HTP UNDER CREEP-FATIGUE LOADING AT 700 degrees C: EXPERIMENTS AND SIMULATIONS Invited Reviewed International journal

    Nobutada Ohno, Tatsuya Sasaki, Takehiro Shimada, Kenji Tokuda, Kimiaki Yoshida, Dai Okumura

    JOURNAL OF THEORETICAL AND APPLIED MECHANICS   Vol. 56 ( 2 ) page: 497 - 510   2018.4

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    Cyclic hardening and stress relaxation experiments of SUS3161HTP were performed under creep-fatigue loading with tensile strain holding at 700 degrees C. Experiments revealed that under strain holding, the slow stress-relaxation stage satisfying Norton's law with slight cyclic hardening followed a rapid stress-relaxation stage that was noticeably affected by cyclic hardening. This suggests that in the slow stress-relaxation stage, inelastic deformation mechanisms different from that of viscoplasticity occurred. Experiments were simulated using a cyclic viscoplastic-creep model in which the inelastic strain-rate was decomposed into viscoplastic and creep components that were affected differently by cyclic hardening. The simulation accurately reproduced the experiments.

    DOI: 10.15632/jtam-pl.56.2.497

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  52. Resetting scheme for plastic strain surface in constitutive modeling of cyclic plasticity Reviewed

    Nobutada Ohno, Ryohei Yamamoto, Tatsuya Sasaki, Dai Okumura

    ZAMM-ZEITSCHRIFT FUR ANGEWANDTE MATHEMATIK UND MECHANIK   Vol. 98 ( 4 ) page: 518 - 531   2018.4

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    A resetting scheme is proposed for correctly evaluating the plastic strain range to analyze structural components subjected to regular cyclic loading following pre-loading. In this scheme, a plastic strain surface, referred to as the plastic-strain-range surface in the present paper, is reset to a point and re-evolves every cycle, with its size at the end of the last cycle considered to be the plastic strain range of the current cycle. This resetting scheme provides a definite value for the evolution parameter of the plastic-strain-range surface irrespective of the amounts of cyclic hardening, pre-straining, and ratcheting. The resetting scheme is implemented in a cyclic viscoplastic model in finite element methods, and is applied to analyze a notched bar subjected to cyclic loading at its ends. Furthermore, the validity of the resetting scheme for non-proportional cyclic loading is examined by analyzing the cyclic behavior along elliptic and rhombic strain paths. It is shown that the resetting scheme allows the use of a definite value for the evolution parameter of the plastic-strain-range surface in the presence of any cyclic hardening and/or ratcheting. Moreover, it is shown that the resetting scheme can be valid for cyclic loading with a certain degree of non-proportionality.

    DOI: 10.1002/zamm.201700298

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  53. Mechanism of plastic deformation in a magnesium nanotwinned structure by molecular dynamics simulations Reviewed

    Dai Okumura, Masanari Otsuka, Yoji Shibutani

    Zairyo/Journal of the Society of Materials Science, Japan   Vol. 67 ( 2 ) page: 215 - 221   2018.2

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    In this study, we perform molecular dynamics simulations to investigate plastic deformation modes of a magnesium (Mg) nanotwinned structure. Periodic units including (10 11) twin boundaries (TBs) are analyzed using an embedded atom method potential. Equal spaces between the TBs are assumed at the initial state and the space is parametrized in the range between about 5 nm and 30 nm. It is found that plastic deformation is triggered by the slip along a (10 11) twinning plane near a TB, and that this event induces two different deformation modes depending on the space, i.e., the migration of the TBs and the evolution of double twinning, which leads to void nucleation and polycrystallization. The plastic deformation provided by the two different modes is quantitatively verified from geometric analysis. As the space decreases, the migration of the TBs is superior to the evolution of double twinning.

    DOI: 10.2472/jsms.67.215

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  54. The effect of cyclic hardening on stress relaxation behavior in creep-fatigue test of SUS 316 at 700°C

    SASAKI Tatsuya, OHNO Nobutada, SHIMADA Takehiro, TOKUDA Kenji, YOSHIDA Kimiaki, OKUMURA Dai

    The Proceedings of Conference of Tokai Branch   Vol. 2018.67 ( 0 ) page: 511   2018

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    DOI: 10.1299/jsmetokai.2018.67.511

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  55. Swelling dependence analysis of an extended Flory-Rehner model using linear perturbation method

    MANO Takafumi, OKUMURA Dai

    The Proceedings of Conference of Tokai Branch   Vol. 2018.67 ( 0 ) page: 202   2018

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    DOI: 10.1299/jsmetokai.2018.67.202

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  56. Analysis of wiggling buckling induced by etching process for bilayer structure under intrinsic compressive stress

    SUGIURA Junya, OKUMURA Dai, TANAKA Hiro

    The Proceedings of Conference of Tokai Branch   Vol. 2018.67 ( 0 ) page: 509   2018

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    DOI: 10.1299/jsmetokai.2018.67.509

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  57. Eigenvalue buckling analysis of long wave-length deformation in porous gel films

    KASUGAI Akishi, OKUMURA Dai

    The Proceedings of Conference of Tokai Branch   Vol. 2018.67 ( 0 ) page: 508   2018

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    DOI: 10.1299/jsmetokai.2018.67.508

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  58. Uniaxial tensile tests of polyacrylamide hydrogels and its estimation.

    The Proceedings of Conference of Tokai Branch   Vol. 2018.67 ( 0 ) page: 212   2018

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    DOI: 10.1299/jsmetokai.2018.67.212

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  59. Validation of Crush Energy Calculation Methods for Use in Accident Reconstructions by Finite Element Analysis

    Shusuke Numata, Koji Mizuno, Daisuke Ito, Dai Okumura, Hisashi Kinoshita

    SAE INTERNATIONAL JOURNAL OF TRANSPORTATION SAFETY   Vol. 6 ( 2 ) page: 133 - 145   2018

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:SAE INT  

    The crush energy is a key parameter to determine the delta-V in accident reconstructions. Since an accurate car crush profile can be obtained from 3D scanners, this research aims at validating the methods currently used in calculating crush energy from a crush profile. For this validation, a finite element (FE) car model was analyzed using various types of impact conditions to investigate the theory of energy-based accident reconstruction.Two methods exist to calculate the crush energy: the work based on the barrier force and the work based on force calculated by the vehicle acceleration times the vehicle mass. We show that the crush energy calculated from the barrier force was substantially larger than the internal energy calculated from the FE model. Whereas the crush energy calculated from the vehicle acceleration was comparable to the internal energy of the FE model.In full frontal impact simulations, the energy of approach factor (EAF) has a linear relation with the residual crush, which had been validated in previous experimental studies. In our study using FE analysis, we found that the slope of EAF versus the residual crush was comparable with that of the dynamic crush energy versus the dynamic crush for crashes at 55 km/h. Using this slope and the residual crush from a 55 km/h impact test, the slope and the intercept of the EAF vs. residual crush can be determined using only one crash test. A database of the slopes and the intercepts was made using Japan New Car Assessment Program (JNCAP) tests. In offset impact simulations, the crush energy calculated from the crush profile agreed with the internal energy of the car FE model when at least one front rail was involved. In oblique impacts, the correction factor for crush energy is not necessary within 20 degrees of principal direction of force of the car's longitudinal axis.

    DOI: 10.4271/09-06-02-0009

    Web of Science

    Scopus

  60. Effect of biaxial deformation on ulimate swelling of elastomers International coauthorship

    OKUMURA Dai, CHESTER U Shain A.

    The Proceedings of The Computational Mechanics Conference   Vol. 2018.31 ( 0 ) page: 217   2018

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    <p>In this study, ie investigate the effect of biaxial deformation on ultimate sielling characterized by limiting chain extensibility of elastomers. Limiting chain extensibility is introduced into the Flory–Rehner theory. To obtain a single unified inequality, stretches are normalized using the material constant that accounts for limiting chain extensibility. Using the derived inequality, systematic analysis provides the ultimate values of sielling ratio under biaxial loading.</p>

    DOI: 10.1299/jsmecmd.2018.31.217

    CiNii Research

  61. Derivation of closed-form solution for linear elastic properties of swollen elastomers

    KAWABATA Hironori, OKUMURA Dai, OHNO Nobutada

    The Proceedings of the Materials and Mechanics Conference   Vol. 2018 ( 0 ) page: OS0305   2018

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    <p>In this study, we derive a closed-form solution for linear elastic properties of swollen elastomers. To this end, linear perturbation analysis is applied to the Flory-Rehner theory. Instead of the Neo-Hookean solid model in the theory, the strain energy function is assumed to consist of three invariants to obtain the most general expression.</p>

    DOI: 10.1299/jsmemm.2018.os0305

    CiNii Research

  62. Relations between limiting chain extensibility and ultimate swelling of swollen elastomers

    OKUMURA Dai, A. CHESTER Shawn

    The Proceedings of the Materials and Mechanics Conference   Vol. 2018 ( 0 ) page: OS0609   2018

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    <p>In this study, we study ultimate swelling characterized by limiting chain extensibility of swollen elastomers. Limiting chain extensibility is introduced into the Flory-Rehner theory. The derived inequality allows for analysis to provide an ultimate value of swelling ratio. This ultimate value is not exceeded at equilibrium swelling regardless of the set of material constants. Under uniaxial loading at equilibrium swelling, deswelling can occur even in tension.</p>

    DOI: 10.1299/jsmemm.2018.os0609

    CiNii Research

  63. Strain distribution in small Sn specimens with few crystal grains obtained by the measurements and the crystal plasticity finite element analysis

    SASAKI Takumi, OKUMURA Dai, KARIYA Yoshiharu, KOGANEMARU Masaaki, IKEDA Toru

    The Proceedings of The Computational Mechanics Conference   Vol. 2018.31 ( 0 ) page: 084   2018

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    <p>Soldering is used for bonding a print circuit board (PCB) and a semiconductor chip. It is known that Sn, which is the base metal of Pb-free solder, shows remarkable crystal anisotropy. To clarify the effect of anisotropy of Sn on strain distribution is important for lifetime evaluation. The strain distribution in a micro specimen under a tensile test was measured by a digital image correlation method (DICM) with a microscope. The strain distribution was also analyzed by the crystal plasticity finite element analysis (CPFEA) considering the critical resolves shear stress (CRSS) of each slip system. The deformation of the crystal structure of β-Sn depends on the size, number and orientation of crystal grains. The CRSS was noticeably different for each slip system, and the yield stress varied with the orientations of crystal grains. Although the CPFEA without considering strain hardening was effective for predicting deformation within crystal grains, it is necessary to consider the strain hardening of crystals to predict the stress-strain curve of a micro-specimen.</p>

    DOI: 10.1299/jsmecmd.2018.31.084

    CiNii Research

  64. Analysis of linear elastic properties of swollen elastomers using elastic strain energies

    KAWABATA Hironori, OKUMURA Dai

    The Proceedings of The Computational Mechanics Conference   Vol. 2018.31 ( 0 ) page: 314   2018

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    <p>In this study, we perform analysis of linear elastic properties considering the influence of elastic strain energies of swollen elastomers. A closed form solution derived in the most general expression is used to introduce the Gent model in the Flory-Rehner theory. The effects of limiting chain extensibility are discussed.</p>

    DOI: 10.1299/jsmecmd.2018.31.314

    CiNii Research

  65. Modeling of the out-of-plane mechanical response of a laminated cellular structure showing negative Poisson’s ratio under uniaxial tensile deformation

    TANAKA Hiro, SUGA Kaito, OKUMURA Dai, SHIBUTANI Yoji

    The Proceedings of The Computational Mechanics Conference   Vol. 2018.31 ( 0 ) page: 250   2018

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    <p>In this study, we analyze the mechanical responses of the two types of laminated cellular structures using finite element models based on a homogenization method. In the numerical simulations, we obtain the homogenized elastic modulus tensors for the two structural units and show that the cellular structure, which is bridged by additional beams, exhibits strong auxeticity with high negative values of Poisson's ratio in the lamination direction, while retaining the in-plane negative Poisson's ratios. We then assess the sensitivity of the linear and nonlinear out-of-plane response to changes in the component geometry. According to the analytical results, we propose a simple periodic framework consisting polyhedron blocks and spherical joints, which can represent the similar auxetic behavior the cellular structure exhibits in the in-plane and out-of-plane directions.</p>

    DOI: 10.1299/jsmecmd.2018.31.250

    CiNii Research

  66. Experimental evaluation of interactions between swelling and elasticity of a hydrogel

    HISHIDA Yushi, OKUMURA Dai, IDA Syohei, UCHIDA Makoto, TANAKA Hiro

    The Proceedings of the Materials and Mechanics Conference   Vol. 2018 ( 0 ) page: OS0715   2018

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    <p>In this study, we performed the equilibrium free swelling and subsequent uniaxial tensile tests of polyacrylamide hydrogels to investigate the interactions between swelling and elasticity. The experimental data were reproduced by adjusting two scaling exponents of the extended Frory-Rehner model. We discussed the tendency of a set of the obtained material parameters.</p>

    DOI: 10.1299/jsmemm.2018.os0715

    CiNii Research

  67. エラストマーの極限膨潤に及ぼす分子鎖伸び切り限界の二軸変形依存性 Reviewed International coauthorship

    奥村 大

    計算数理工学論文集   Vol. 18   page: 7 - 18   2018

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  68. アクリルアミドハイドロゲルを用いた拡張Flory-Rehnerモデルの基礎的検証 Reviewed

    奥村大, 清水章司, 伊田翔平, 内田真, 田中展

    計算数理工学論文集   Vol. 17   page: 53 - 58   2017.12

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  69. Evaluation of Deformation Behavior of Hydrogel on Uniaxial Tensile Test using Digital Image Correlation Reviewed

    Keita Suzuki, Makoto Uchida, Yoshihisa Kaneko, Dai Okumura, Hiro Tanaka, Shohei Ida

    Proceedings of the 12th International Symposium on Advanced Science and Technology in Experimental Mechanics     page: 035   2017.11

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:日本実験力学会  

  70. Finite element analysis of swelling-induced pattern transformation in gel membranes

    TERAI Yoshihiko, OKUMURA Dai

    The Proceedings of Conference of Tokai Branch   Vol. 2017.66 ( 0 ) page: 521   2017

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:The Japan Society of Mechanical Engineers  

    DOI: 10.1299/jsmetokai.2017.66.521

    CiNii Research

  71. Study on implementation of the extended Flory-Rehner model and its incremental stability

    SHIMIZU Shoji, OKUMURA Dai

    The Proceedings of Conference of Tokai Branch   Vol. 2017.66 ( 0 ) page: 522   2017

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:The Japan Society of Mechanical Engineers  

    DOI: 10.1299/jsmetokai.2017.66.522

    CiNii Research

  72. Influence of plate thickness on out-of-plane undulating buckling analysis of microscopic patterned structure

    SUGIURA Junya, OKUMURA Dai, TANAKA Hiro

    The Proceedings of Conference of Tokai Branch   Vol. 2017.66 ( 0 ) page: 518   2017

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    DOI: 10.1299/jsmetokai.2017.66.518

    CiNii Research

  73. Influence of plate thickness and intrinsic stress on wiggling buckling of a microscopic patterned structure

    Sugiura Junya, Okumura Dai, Tanaka Hiro

    The Proceedings of The Computational Mechanics Conference   Vol. 2017.30 ( 0 ) page: 205   2017

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    DOI: 10.1299/jsmecmd.2017.30.205

    CiNii Research

  74. Microscopic plastic deformation analysis of β-Sn single crystal using molecular dynamics

    MATSUNO Natsuki, KINOSHITA Yusuke, OKUMURA Dai

    The Proceedings of Conference of Tokai Branch   Vol. 2017.66 ( 0 ) page: 523   2017

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    DOI: 10.1299/jsmetokai.2017.66.523

    CiNii Research

  75. Analysis of elastic properties of swollen elastomers under prestrain

    OKUMURA Dai, MANO Takafumi

    The Proceedings of The Computational Mechanics Conference   Vol. 2017.30 ( 0 ) page: 212   2017

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    DOI: 10.1299/jsmecmd.2017.30.212

    CiNii Research

  76. Analysis of domain wall formation mechanism in swelling-induced pattern transformation of porous gel membranes

    OKUMURA Dai, KASUGAI Akishi

    The Proceedings of Conference of Tokai Branch   Vol. 2017.66 ( 0 ) page: 520   2017

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    DOI: 10.1299/jsmetokai.2017.66.520

    CiNii Research

  77. Buckling Eigenvalue Analysis of Swelling-induced Instability on Porous Gel Films

    ISOMURA Taiji, Okumura Dai

    The Proceedings of Conference of Tokai Branch   Vol. 2017.66 ( 0 ) page: 519   2017

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    DOI: 10.1299/jsmetokai.2017.66.519

    CiNii Research

  78. Dependence of finite elements on swelling-induced instability in porous gel films

    KASUGAI Akishi, ISOMURA Taiji, OKUMURA Dai

    The Proceedings of The Computational Mechanics Conference   Vol. 2017.30 ( 0 ) page: 204   2017

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    DOI: 10.1299/jsmecmd.2017.30.204

    CiNii Research

  79. Eigenvalue buckling analysis of domain wall defect in porous gel films

    KASUGAI Akishi, OKUMURA Dai, OHNO Nobutada

    The Proceedings of the Materials and Mechanics Conference   Vol. 2017 ( 0 ) page: OS1604   2017

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    <p>In this paper, we perform eigenvalue buckling analysis to investigate a defect of domain walls (DWs) in a diamond plate pattern (DPP), which is caused by swelling-induced pattern transformation in porous gel films. It is found that DWs in a DPP can be captured as long wavelength buckling. The critical stress of DWs in a DPP is higher than that of a uniform DDP, but as periodic units increase, both are identical. This means that this defect, i.e., DW, is hardly eliminated in DPPs. Further, the pattern of DWs consists of 4 basic buckling modes, which are obtained from extending the buckling mode of the DPP using the Bloch wave.</p>

    DOI: 10.1299/jsmemm.2017.os1604

    CiNii Research

  80. Experimental verification of extended Flory-Rehner model using polyacrylamide hydrogels

    SHIMIZU Shoji, OKUMURA Dai, IDA Shohei, TANAKA Hiro, UCHIDA Makoto

    The Proceedings of the Materials and Mechanics Conference   Vol. 2017 ( 0 ) page: OS0306   2017

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    <p>An extended F-R model is experimentally verified using polyacrylamide hydrogels. Stress-stretch responses of the extended F-R model are compared with those of the original F-R model and the Ogden model. As a result, the extended F-R model is superior to the original F-R model because the extended F-R model can adjust swelling dependence of Young's modulus. Further, the extended F-R model is comparable to the Ogden model for small deformations because the extended F-R model does not include the effect of limiting chain extensibility. The results of the extended F-R model imply that polyacrylamide hydrogels can cause swelling-induced strain softening.</p>

    DOI: 10.1299/jsmemm.2017.os0306

    CiNii Research

  81. Comparative analysis of extended Flory-Rehner model and Ogden model based on uniaxial tensile tests of polyacrylamide hydrogels

    SHIMIZU Shoji, OKUMURA Dai, IDA Shohei, TANAKA Hiro, UCHIDA Makoto

    The Proceedings of The Computational Mechanics Conference   Vol. 2017.30 ( 0 ) page: 241   2017

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:The Japan Society of Mechanical Engineers  

    DOI: 10.1299/jsmecmd.2017.30.241

    CiNii Research

  82. Effects of two scaling exponents on swelling-induced softening of elastomers under equibiaxial and planar extensions

    Okumura D., Mizutani M.

    Key Engineering Materials   Vol. 725 KEM   page: 427 - 432   2017

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    We study the effects of two scaling exponents on the mechanical properties of swollen elastomers under equibiaxial and planar extensions. Two scaling exponents are introduced to extend the Flory-Rehner free energy function, and are adjusted based on the previous study. Results show that swelling-induced strain softening is apt to occur under equibiaxial extension compared to uniaxial extension. The additional tensile stress in a lateral direction enables it to occur in relatively poor solvents, and accelerates the onset point. Planar extension shows more complicated responses because the stress in the constrained direction changes dramatically depending on the combination of two scaling exponents and the Flory-Huggins interaction parameter.

    DOI: 10.4028/www.scientific.net/KEM.725.427

    Scopus

  83. Thermo-mechanical cyclic plastic behavior of 304 stainless steel at large temperature ranges

    Ohno N., Yamamoto R., Okumura D.

    Key Engineering Materials   Vol. 725 KEM   page: 275 - 280   2017

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    Thermo-mechanical cyclic experiments on 304 stainless steel were performed at several temperature ranges which had maximum temperatures ranging from 350°C to 1000°C and a minimum temperature of 150°C. Related isothermal cyclic experiments were also performed. Temperature-history dependent cyclic hardening significantly occurred under thermo-mechanical cyclic loading with maximum temperatures around 600°C, whereas almost no cyclic hardening was observed when the maximum temperature was 1000°C. The observed thermo-mechanical cyclic plastic behavior in the saturated state of cyclic hardening was then simulated using a cyclic viscoplastic constitutive model, leading to the following findings. It was difficult to predict the saturated thermo-mechanical cyclic behavior using only the isothermal cyclic experimental data. The saturated thermo-mechanical cyclic behavior was simulated well by introducing a cyclic hardening parameter depending on the maximum temperature. This means that the cyclic hardening parameter should not change with temperature but depend on the maximum temperature in the saturated state of cyclic hardening under thermo-mechanical cyclic loading.

    DOI: 10.4028/www.scientific.net/KEM.725.275

    Scopus

  84. 高分子ゲルの拡張Flory-Rehnerモデルを用いた線形摂動解析 Reviewed

    奥村 大

    計算数理工学論文集   Vol. 17   page: 47 - 52   2017

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  85. Using two scaling exponents to describe the mechanical properties of swollen elastomers Reviewed

    D Okumura, A Kondo, N Ohno

    Journal of the Mechanics and Physics of Solids   Vol. 90   page: 61 - 76   2016

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  86. Swelling-induced buckling patterns in gel films with a square lattice of holes subjected to in-plane uniaxial and biaxial pretensions Reviewed

    D. Okumura, A. Sasaki, N. Ohno

    Advanced Structured Materials   Vol. 64   page: 319-334   2015.6

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  87. Effects of prestrains on swelling induced buckling patterns of gel film with square lattice of holes Reviewed

    D. Okumura, T. Inagaki, N. Ohno

    International Journal of Solids and Structures   Vol. 58   page: 288-300   2015.4

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  88. Effect of strain hardening on monotonic and cyclic loading behavior of plate-fin structures with two pore pressures Reviewed

    S. Banno, D. Okumura, N. Ohno

    Key Engineering Materials   Vol. 626   page: 133-138   2015

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  89. チューブ-フィン構造体におけるフィン層の均質化弾性剛性(曲げ負荷に対する検証) Reviewed

    岩堀恵介,大野信忠,松下幸平,奥村大,宮川進

    日本機械学会論文集   Vol. 81   page: 0-0   2015

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  90. Elastic-viscoplastic implicit integration algorithm applicable to both plane stress and three-dimensional stress states Reviewed

    N. Ohno, M. Tsuda, H. Sugiyama, D. Okumura

    Finite Elements in Analysis and Design     page: 00-00   2015

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  91. Effect of geometrical imperfections on swelling-induced buckling patterns in gel films with a square lattice of holes Reviewed

    D. Okumura, T. Kuwayama, N. Ohno

    International Journal of Solids and Structures   Vol. 51 ( 1 ) page: 154-163   2014.1

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  92. Homogenized elastic-viscoplastic behavior of plate-fin structures with two pore pressures Reviewed

    N. Ohno, K. Narita, D. Okumura

    International Journal of Mechanical Sciences   Vol. 86   page: 18-25   2014

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  93. The large scale finite element analysis of a charge air cooler using a homogenization method Reviewed

    K. Iwahori, N. Ohno, D. Okumura, T. Muraki, S. Miyakawa

    SAE Technical Paper   Vol. 2013 ( 01 ) page: 1212   2013.8

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  94. チューブ-フィン構造体におけるフィン層の均質化弾性剛性(評価と検証) Reviewed

    岩堀 恵介, 大野 信忠, 村木 友也, 奥村 大, 宮川 進

    日本機械学会論文集A編   Vol. 79   page: 89-99   2013

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  95. Implicit iterative finite element scheme for a strain gradient crystal plasticity model based on self-energy of geometrically necessary dislocations Reviewed

    R. Kametani, K. Kodera, D. Okumura, N. Ohno

    Computational Materials Science   Vol. 53   page: 53-59   2012

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  96. Homogenizaed elastic-viscoplastic behavior of anisotropic open-porous bodies with pore pressure Reviewed

    N. Ohno, K. Ikenoya, D. Okumura, T. Matsuda

    International Journal of Solids and Structures   Vol. 49   page: 2799-2806   2012

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  97. 弾性積層ダンボールの圧縮強度に微視構造の及ぼす影響の均質化解析 Reviewed

    奥村 大,大野信忠,小野田孝行,曽我将孝

    計算数理工学論文集   Vol. 12   page: 103-108   2012

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  98. Plastic size effect analysis of lamellar composites using a discrete dislocation plasticity approach Reviewed

    D. Okumura, N. Ohno, K. Yamaguchi

      Vol. 27   page: 2040-2055   2011.12

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  99. Influence of closed faces on compressive strength of open cell metallic foams Reviewed

    Dai Okumura, Yuji Takahashi, Nobutada Ohno

    Materials Research Innovations   Vol. 15   page: S61-S64   2011

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    DOI: S61-S64

  100. 離散転位塑性法を用いたラメラ複合材料の均質化解析 Invited

    奥村 大,大野 信忠

    計算数理工学レビュー   Vol. 2011-1   page: 13-19   2011

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    DOI: 13-19

  101. 離散転位動力学解析のための均質化理論の定式化 Reviewed

    奥村 大,大野信忠,片桐慶大

    材料   Vol. 59 ( 2 ) page: 149-156   2010.2

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  102. Yield and buckling behavior of Kelvin open-cell foams subjected to uniaxial compression Reviewed

    Yuji Takahashi, Dai Okumura, Nobutada Ohno

    International Journal of Mechanical Sciences   Vol. 52 ( 2 ) page: 377-385   2010

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    DOI: 377-385

  103. 幾何学的に必要な転位の自己エネルギーを考慮したひずみこう配結晶組成理論のための陰的有限要素方程式 Reviewed

    小寺一輝,亀谷隆真,奥村 大,大野信忠

    計算数理工学論文集   Vol. 9   page: 43-48   2009

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  104. 単軸圧縮を受けるケルビンオープンセルフォームの微視的座屈挙動 Reviewed

    奥村 大,岡田篤志,大野信忠

    材料   Vol. 57 ( 2 ) page: 126-133   2008.2

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  105. Buckling behavior of Kelvin open-cell foams under [0 0 1], [0 1 1] and [1 1 1] compressive loads Reviewed

    Dai Okumura, Atsushi Okada, Nobutada Ohno

    International Journal of Solids and Structures   Vol. 45 ( 13 ) page: 3807-3820   2008

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  106. Grain-size dependent yield behavior under loading, unloading, and reverse loading Reviewed

    N. Ohno, D. Okumura, T. Shibata

    International Journal of Modern Physics B   Vol. 22   page: 5937-5942   2008

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  107. Three-dimensional microscopic interlaminar analysis of cross-ply laminates based on a homogenization theory Reviewed

    Tetsuya Matsuda, Dai Okumura, Nobutada Ohno, Masamichi Kawai

    International Journal of Solids and Structures   Vol. 44 ( 25-26 ) page: 8274-8284   2007

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  108. * A homogenization theory of strain gradient single-crystal plasticity and its finite element discretization Reviewed

    D. Okumura, Y. Higashi, K. Sumida, N. Ohno

    International Journal of Plasticity   Vol. 23   page: 1148-1166   2007

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    In this study, a homogenization theory based on the Gurtin strain gradient formulation and its finite element discretization are developed for investigating the size effects on macroscopic responses of periodic materials. To derive the homogenization equations consisting of the relation of macroscopic stress, the weak form of stress balance, and the weak form of microforce balance, the Y-periodicity is used as additional, as well as standard, boundary conditions at the boundary of a unit cell. Then, by applying a tangent modulus method, a set of finite element equations is obtained from the homogenization equations. The computational stability and efficiency of this finite element discretization are verified by analyzing a model composite. Furthermore, a model polycrystal is analyzed for investigating the grain size dependence of polycrystal plasticity. In this analysis, the micro-clamped, micro-free, and defect-free conditions are considered as the additional boundary conditions at grain boundaries, and their effects are discussed.

  109. * Higher-order stress and grain size effects due to self-energy of geometrically necessary dislocations Reviewed

    N. Ohno, D. Okumura

    Journal of the Mechanics and Physics of Solids   Vol. 55   page: 1879-1898   2007

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    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 at small strains. It is pointed out that this higher-order stress changes stepwise in response to the in-plane gradient of slip, and thus significantly influences the onset of initial yielding in polycrystals. The self energy of GNDs is then incorporated into the strain gradient plasticity theory of Gurtin (J. Mech. Phys. Solids 50 (2002) 5). The resulting theory is applied to 2D and 3D model crystal grains of size D, leading to the D-1-dependent term of grain yielding with a coefficient determined by grain shape and orientation. This size effect term, which is also derived from a simple energy equation, is discussed using published experimental data of several polycrystalline metals. It is thus shown that the self energy of GNDs quantitatively accounts for not only the grain size dependence of initial yield stress but also the dislocation cell size dependence of flow stress in the submicron to several-micron range of grain and cell sizes.

  110. Long wave-length buckling of periodic open-cell foams subjected to uniaxial compression Reviewed

    D. Okumura, A. Okada, N. Ohno

    Key Engineering Materials   Vol. 345-346   page: 81-84   2007

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  111. Microscopic interlaminar stress analysis of CFRP cross-ply laminate using a homogenization theory Reviewed

    T. Matsuda, D. Okumura, N. Ohno, M. Kawai

    Key Engineering Materials   Vol. 340-341   page: 1043-1048   2007

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  112. Higher-Order Stress Due to Self Energy of Geometrically Necessary Dislocations Reviewed

    N. Ohno, D. Okumura

    Key Engineering Materials   Vol. 340-341   page: 173-178   2007

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  113. 単軸圧縮を受ける立方体フォームの長波長座屈 Reviewed

    奥村 大,岡田篤志,大野信忠

    計算数理工学論文集   Vol. 6   page: 55-60   2006

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  114. Long-wage in-plane buckling of elastoplastic square honeycombs Reviewed

    K. Erami, N. Ohno, D. Okumura

    International Journal of Plasticity   Vol. 22   page: 1569-1585   2006

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  115. Long-wave in-plane buckling of elastic square honeycombs Reviewed

    D. Okumura, N. Ohno, T. Niikawa

    Mechanics of Advanced Materials and Structures   Vol. 12   page: 175-183   2005

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  116. 非局所結晶塑性を考慮した均質化理論による多結晶塑性解析(粒界でのすべりの境界条件の影響) Reviewed

    奥村 大,東 洋一,大野信忠

    計算数理工学論文集   Vol. 5   page: 25-30   2005

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  117. 非局所結晶塑性を考慮した均質化理論の構築と有限要素離散化 Reviewed

    奥村 大,東 洋一,大野信忠

    材料   Vol. 54   page: 909-914   2005

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    本研究では,非局所結晶塑性を考慮した均質化理論を構築し,その有限要素離散化の方法を示す.このため,周期単位境界上での付加的な境界条件にはY周期境界条件が用いられる.また,接線係数法の適用によって,応力の釣合い式と高次応力の釣合い式,巨視的応力がマトリックス連成した有限要素方程式が得られることを示す.

  118. 均質化理論による周期セル状固体の微視的分岐と巨視的不安定の解析 Invited

    奥村 大,大野信忠

    計算数理工学レビュー   Vol. 2005 ( 2 ) page: 11-18   2005

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  119. * Elastoplastic Microscopic Bifurcation and Post-Bifurcation Behavior of Periodic Cellular Solids Reviewed

    D. Okumura, N. Ohno and H. Noguchi

    Journal of the Mechanics and Physics of Solids   Vol. 52 ( 3 ) page: 641-666   2004

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    In this study, a general framework is developed to analyze microscopic bifurcation and post-bifurcation behavior of elastoplastic, periodic cellular solids. The framework is built on the basis of a two-scale theory, called a homogenization theory, of the updated Lagrangian type. We thus derive the eigenmode problem of microscopic bifurcation and the orthogonality to be satisfied by the eigenmodes. The orthogonality allows the macroscopic increments to be independent of the eigenmodes, resulting in a simple procedure of the elastoplastic post-bifurcation analysis based on the notion of comparison solids. By use of this framework, then, bifurcation and post-bifurcation analysis are performed for cell aggregates of an elastoplastic honeycomb subject to in-plane compression. Thus, demonstrating a basic, long-wave eigenmode of microscopic bifurcation under uniaxial compression, it is shown that the eigenmode has the longitudinal component dominant to the transverse component and consequently causes microscopic buckling to localize in a cell row perpendicular to the loading axis. It is further shown that under equi-biaxial compression, the flower-like buckling mode having occurred in a macroscopically stable state changes into an asymmetric, long-wave mode due to the sextuple bifurcation in a macroscopically unstable state, leading to the localization of microscopic buckling in deltaic areas.

  120. Long-wave buckling of elastic square honeycombs subject to in-plane biaxial compression Reviewed

    N. Ohno, D. Okumura, T. Niikawa

    International Journal of Mechanical Sciences   Vol. 46   page: 1697-1713   2004

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  121. 均質化理論を用いたクロスプライ積層板の層間およびその近傍における微視的3次元解析 Reviewed

    松田哲也,奥村 大,大野信忠,徳田正孝

    計算数理工学論文集   Vol. 4   2004

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  122. 非弾性周期構造材料に対するマルチスケール増分解析アルゴリズム

    浅田崇史,大野信忠,奥村 大

    第17回計算力学講演会講演論文集     page: 711-712   2004

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  123. 均質化理論に基づく正方形ハニカムの微視的分岐と巨視的不安定の解析

    新川岳史,奥村 大,大野信忠

    東海支部第53期総会講演会講演論文集     page: 25-26   2004

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  124. 均質化理論に基づく非局所結晶塑性の有限要素解析

    奥村 大,大野信忠,東 洋一

    第17回計算力学講演会講演論文集     page: 709-710   2004

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  125. Long-wave buckling of square honeycombs subject to in-plane compression

    D. Okumura, N. Ohno and T. Niikawa

    International Workshops on Advances in Computational Mechanics (IWACOM)     page: 59   2004

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  126. 均質化理論に基づく非局所結晶塑性の有限要素解析手法の構築

    奥村 大,大野信忠,東 洋一

    第48回日本学術会議材料研究連合講演会講演論文集     page: 237-238   2004

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  127. Multiscale instability analysis of corrugated fiberboard

    H. Noguchi, N. Ohno and D. Okumura

    2nd International Conference on Multiscale, Materials Modeling (MMM-II)     page: CDROM   2004

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  128. Three-Dimensional Microscopic Analysis of Inter-Laminar Area in Cross-Ply Laminate Using a Homogenization Theory

    T. Matsuda, D. Okumura, N. Ohno and M. Tokuda

    Proc. the 2004 Int. Symp. on Micro-Nano Mechatronics and Human Science & The Fourth Symp. "Micro-Nano Mechatronics for an Information-Based Society" The 21st Century COE Program     page: 81-86   2004

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  129. Multiscale buckling analyses of corrugated fiberboard

    H. Noguchi, N. Ohno and D. Okumura

    International Congress of Theoretical and Applied Mechanics (ICTAM04)     page: CDROM   2004

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  130. Elastoplastic microscopic bifurcation and post-bifurcation behavior of periodic cellular solids

    N. Ohno, D. Okumura and H. Noguchi

    International Congress of Theoretical and Applied Mechanics (ICTAM04)     page: CDROM   2004

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  131. Microscopic Bifurcation and Post-Bifurcation Behavior of Periodic Cellular Solids

    N. Ohno, D. Okumura and H. Noguchi

    Proceedings of ICES2004     page: CDROM   2004

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  132. Microscopic Bifurcation Analysis for Long-Wave In-Plane Buckling of Elastic Square Honeycombs

    D. Okumura, N. Ohno and T. Niikawa

    Proceedings of ICES2004     page: CDROM   2004

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  133. 多結晶モデルの有限要素解析における境界条件の影響

    奥村 大,大野信忠,中根和彦,川上 崇,高橋浩之

    M&M2004材料力学カンファレンス講演論文集     page: 369-370   2004

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  134. Elastoplastic microscopic buckling of periodic cellular solids

    N. Ohno, D. Okumura and H. Noguchi

    International Conference on Heterogeneous Material Mechanics     page: CDROM   2004

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  135. FCC多結晶モデルの有限要素解析における境界条件の影響

    奥村 大,大野信忠,中根和彦,川上 崇,高橋浩之

    第9回計算工学講演論文集     page: 51-52   2004

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  136. 多結晶モデルの有限要素解析における境界条件の影響

    大野信忠,奥村 大,中根和彦,川上 崇,高橋浩之

    日本材料学会第53期学術講演会講演論文集     page: 465-466   2004

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  137. 均質化理論に基づく正方形ハニカムの微視的座屈解析

    奥村 大,大野信忠,新川岳史

    日本材料学会第53期学術講演会講演論文集     page: 490-491   2004

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  138. 均質化理論による周期セル状固体の微視的分岐と巨視的不安定の弾塑性解析 Reviewed

    奥村 大,大野信忠,野口裕久

    日本機械学会論文集, A編   Vol. 69 ( 686 ) page: 1421-1428   2003

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  139. Microscopic buckling and macroscopic instability of periodic cellular solids

    N. Ohno, D. Okumura and H. Noguchi

    9th International Conference on the Mechanical Behaviour of Materials (ICM9)     page: CDROM   2003

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  140. 均質化理論によるセル状周期材料の微視的分岐解析

    奥村 大,大野信忠,野口裕久

    第52回理論応用力学講演会講演論文集     page: 485-486   2003

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  141. 均質化理論に基づく非局所結晶塑性の解析

    奥村 大,大野信忠

    第53回理論応用力学講演会講演論文集     page: 257-258   2003

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  142. 均質化理論に基づくハニカムの微視的分岐と巨視的不安定の解析

    新川岳史,奥村 大,大野信忠

    第16回計算力学講演会講演論文集     page: 607-608   2003

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  143. 均質化理論に基づく非局所結晶塑性解析

    奥村 大,大野信忠

    第16回計算力学講演会講演論文集     page: 437-438   2003

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  144. Microscopic Inter-Laminar Analysis of CFRP Cross-Ply Laminates Using a Homogenization Theory

    T. Matsuda, D. Okumura, T. Ishikawa and N. Ohno

    Proceedings of IMMM2003     page: 82-87   2003

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  145. Microscopic Buckling and Macroscopic Instability of Periodic Cellular Solids Reviewed

    D. Okumura, N. Ohno and H. Noguchi

    International Conference on ATEM 2003, Proceedings of ATEM '03     page: CDROM   2003

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  146. Elastoplastic microscopic bifurcastion in periodic cellular solids

    N. Ohno, D. Okumura and H. Noguchi

    Proceedings of PLASTICITY '03     page: CDROM   2003

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  147. 均質化理論に基づくハニカムの微視的座屈と巨視的局所化の解析

    奥村 大,大野信忠,野口裕久

    東海支部三重地区講演会     page: 198-199   2003

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  148. 均質化理論による弾塑性ハニカムの微視的座屈と巨視的局所化の解析

    奥村 大,大野信忠,野口裕久

    日本材料学会第52期学術講演会講演論文集     page: 115-116   2003

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  149. * Microscopic Symmetric Bifurcation Condition of Cellular Solids Based on a Homogenization Theory of Finite Deformation Reviewed

    N. Ohno, D. Okumura and H. Noguchi

    Journal of the Mechanics and Physics of Solids   Vol. 50 ( 5 ) page: 1125-1153   2002

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  150. * Post-Buckling Analysis of Elastic Honeycombs Subject to In-Plane Biaxial Compression Reviewed

    D. Okumura, N. Ohno and H. Noguchi

    International Journal of Solids and Structures   Vol. 39 ( 13-14 ) page: 3487-3503   2002

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  151. A homogenization framework for analysis of microscopic buckling of cellular solids

    N. Ohno, D. Okumura and H. Noguchi

    Proceedings of PLASTICITY '02     page: 147-149   2002

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  152. 均質化理論に基づく正六角形弾塑性ハニカムの面内座屈解析

    奥村 大,大野信忠,野口裕久

    第15回計算力学講演会講演論文集     page: 285-286   2002

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  153. 均質化理論に基づく周期材料の微視的分岐条件

    奥村 大,大野信忠,野口裕久

    第7回計算工学講演会講演論文集     page: 503-504   2002

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  154. 均質化理論による弾塑性ハニカムの面内座屈解析

    奥村 大,大野信忠,野口裕久

    東海支部第51期総会講演会講演論文集     page: 331-332   2002

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  155. 有限変形の均質化理論に基づくセル状固体の微視的対称分岐解析(第2報,正六角形ハニカムの面内座屈への適用) Reviewed

    奥村 大,大野信忠,野口裕久

    日本機械学会論文集, A編   Vol. 67 ( 658 ) page: 925-932   2001

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  156. 有限変形の均質化理論に基づくセル状固体の微視的対称分岐解析(第1報,理論) Reviewed

    大野信忠,奥村 大,野口裕久

    日本機械学会論文集, A編   Vol. 67 ( 656 ) page: 618-624   2001

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  157. 有限変形の均質化理論に基づくハニカムの面内座屈後解析

    奥村 大,小濱由紀,大野信忠,野口裕久

    東海支部第50期総会講演会講演論文集     page: 103-104   2001

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  158. 均質化理論によるハニカムの面内座屈後解析

    奥村 大,大野信忠,野口裕久

    第14回計算力学講演会講演論文集     page: 1-2   2001

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  159. Microscopic Bifurcation Analysis of Cellular Solids: Theory and Computation

    N. Ohno, D. Okumura and H. Noguchi

    Proceedings of ICES '01     page: CDROM   2001

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  160. 周期材料の自由表面および巨視的界面近傍における微視的解析

    大野信忠,石川琢也,松田哲也,奥村 大,野口裕久

    日本機械学会材料力学部門講演会講演論文集     page: 559-560   2001

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  161. Analysis of Microscopically Symmetric Bifurcation of Cellular Solids Based on a Homogenization Theory

    N. Ohno, D. Okumura and H. Noguchi

    INTERNATIONAL SYMPOSIA ON MATERIALS SCIENCE FOR THE 21ST CENTURY (ISMS-21)     page: 299-304   2001

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  162. Microscopic symmetric bifurcation condition of cellular solids based on a homogenization theory of finite deformation

    N. Ohno, D. Okumura and H. Noguchi

    Proceedings of IMMM2001     page: 47-54   2001

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  163. 均質化理論によるハニカムの内面座屈後解析

    奥村 大, 小濱由紀, 大野忠信, 野口裕久

    第6回計算工学講演会論文集     page: 423-424   2001

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  164. Stability of microscopic buckling modes of honeycombs subject to in-plane biaxial compression

    N. Ohno, D. Okumura and H. Noguchi

    IUTAM'01 symposium, Material Instabilities and the Effect of Microstructure     page: 29   2001

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  165. 更新ラグランジュ形式による有限変形の均質化法の定式化について

    大野信忠,奥村 大

    第49回理論応用力学講演会講演論文集     2000

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  166. 有限変形の均質化理論に基づくハニカムの面内座屈解析

    奥村 大,大野信忠,野口裕久

    第13回計算力学講演会講演論文集     page: 769-770   2000

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  167. A Homogenization Theory of Finite Deformation: Formulation and Application to Buckling Analysis of Honeycombs

    N. Ohno, D. Okumura and H. Noguchi

    Proceedings of ICES 2000     page: 1092-1097   2000

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  168. 均質化理論に基づくセル状固体の対称分岐座屈条件

    大野信忠,奥村 大,野口裕久

    日本機械学会材料力学部門講演会講演論文集     page: 171-172   2000

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  169. 有限変形の均質化理論によるハニカムの座屈解析

    大野信忠,奥村 大,野口裕久

    日本機械学会東海支部第49期総会講演会講演論文集     page: 181-182   2000

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▼display all

Books 1

  1. Time-Swelling Superposition Principle for the Linear Viscoelastic Properties of Polyacrylamide Hydrogels

    Matsubara S., Takashima A., Nagashima S., Ida S., Tanaka H., Uchida M., Okumura D.

    Advanced Structured Materials  2023 

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    We study the linear viscoelastic properties of polyacrylamide hydrogels over a wide range of swelling and deswelling states. The experimental data of dynamic moduli demonstrate that deswollen hydrogels exhibit the linear viscoelastic behaviors while swollen hydrogels behave as a purely elastic material. To capture the linear viscoelastic nature of deswollen hydrogels, we advocate the time-swelling superposition principle inspired by the swelling-dependent linear viscoelasticity model. In this principle, the Williams-Landel-Ferry type equation and the scaling law prescribe the horizontal and vertical shift factors as a function of the volume swelling ratio, making it possible to organize the dynamic moduli in the deswelling state. The resulting master curves elucidate that the dynamic moduli have a positive power-law correlation with the angular frequency. In addition, two shift factors reveal that deswelling enhances both frequency sensitivity and elastic property in dynamic moduli. The scaling exponents of the elastic moduli in the deswelling state are, in particular, larger than those in the swelling state, regardless of the contents of monomer and cross-linker. The generalized Maxwell model equipped with identified material parameters quantifies the linear viscoelastic behaviors that depend on frequency and water content.

    DOI: 10.1007/978-3-031-39070-8_12

    Scopus

MISC 9

  1. Surface Instabilities of Soft Materials

    OKUMURA Dai

    Journal of the Society of Materials Science, Japan   Vol. 71 ( 6 ) page: 555   2022.6

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    Language:Japanese   Publisher:The Society of Materials Science, Japan  

    DOI: 10.2472/jsms.71.555

    CiNii Research

  2. ヘリンボン及びトリプルジャンクションパターンの発達に対する影響因子解析 Reviewed

    奥村 大

    計算数理工学論文集   Vol. 21   page: 51 - 56   2021

  3. Measurement and numerical analysis with the crystal plasticity for strain in crystal grains of small Sn specimen

    IKEDA Toru, SASAKI Takumi, KOGANEMARU Masaaki, YANASE Atsushi, OKUMURA Dai, KARIYA Yoshiharu

    The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2019 ( 0 ) page: J01102   2019

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    Language:Japanese   Publishing type:Research paper, summary (national, other academic conference)   Publisher:The Japan Society of Mechanical Engineers  

    DOI: 10.1299/jsmemecj.2019.J01102

    CiNii Research

  4. Strain distribution in small Sn specimens with few crystal grains obtained by the measurements and the crystal plasticity finite element analysis

    SASAKI Takumi, OKUMURA Dai, KARIYA Yoshiharu, KOGANEMARU Masaaki, IKEDA Toru

    The Proceedings of The Computational Mechanics Conference   Vol. 2018 ( 0 ) page: 84 - 84   2018

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    Language:Japanese   Publisher:The Japan Society of Mechanical Engineers  

    <p>Soldering is used for bonding a print circuit board (PCB) and a semiconductor chip. It is known that Sn, which is the base metal of Pb-free solder, shows remarkable crystal anisotropy. To clarify the effect of anisotropy of Sn on strain distribution is important for lifetime evaluation. The strain distribution in a micro specimen under a tensile test was measured by a digital image correlation method (DICM) with a microscope. The strain distribution was also analyzed by the crystal plasticity finite element analysis (CPFEA) considering the critical resolves shear stress (CRSS) of each slip system. The deformation of the crystal structure of β-Sn depends on the size, number and orientation of crystal grains. The CRSS was noticeably different for each slip system, and the yield stress varied with the orientations of crystal grains. Although the CPFEA without considering strain hardening was effective for predicting deformation within crystal grains, it is necessary to consider the strain hardening of crystals to predict the stress-strain curve of a micro-specimen.</p>

    DOI: 10.1299/jsmecmd.2018.31.084

    CiNii Research

  5. Verification of Foppl-von Karman Plate Theory for Wiggling Buckling Analysis in Microscopic Patterned Structure

      Vol. 22   page: 3p   2017.5

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  6. 高分子ゲルの材料モデリングと膨潤誘起不安定変形解析

    奥村 大

    計算数理工学レビュー = JASCOME reviews : 日本計算数理工学会誌 / 日本計算数理工学会 編   Vol. 2017 ( 1 ) page: 11 - 22   2017.3

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    Language:Japanese   Publisher:日本計算数理工学会  

  7. Evaluation of the distributions of strain in small Sn specimens with few crystals

    YANASE Atsushi, IKEDA Toru, KOGANEMARU Masaki, Kariya Yoshiharu, OKUMURA Dai

    The Proceedings of Conference of Kyushu Branch   Vol. 2017 ( 0 ) page: 713 - 713   2017

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    Language:Japanese   Publisher:The Japan Society of Mechanical Engineers  

    DOI: 10.1299/jsmekyushu.2017.70.713

  8. Measurement and analysis of micro Sn specimens with few crystal grains considering crystal anisotropy

    IKEDA Toru, YANASE Atsushi, SASAKI Takumi, KOGANEMARU Masaaki, OKUMURA Dai, KARIYA Yoshiharu

    The Proceedings of Mechanical Engineering Congress, Japan   Vol. 2017 ( 0 ) page: J0330301   2017

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    Language:Japanese   Publisher:The Japan Society of Mechanical Engineers  

    DOI: 10.1299/jsmemecj.2017.J0330301

  9. Measurements and the FEM analyses of strain distribution in small Sn specimens with few crystal grains

    Sasaki Takumi, Yanase Atsushi, Ikeda Toru, masaaki Koganemaru, Okumura Dai, Kariya Yoshiharu

    The Proceedings of The Computational Mechanics Conference   Vol. 2017 ( 0 ) page: 103 - 103   2017

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    Language:Japanese   Publisher:The Japan Society of Mechanical Engineers  

    DOI: 10.1299/jsmecmd.2017.30.103

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Presentations 90

  1. Effects of two scaling exponents on swelling-induced softening of elastomers under equibiaxial and planar extensions

    Okumura D.

    Key Engineering Materials 

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    Event date: 2017

    Language:English   Presentation type:Oral presentation (general)  

    DOI: 10.4028/www.scientific.net/KEM.725.427

    Scopus

  2. Thermo-mechanical cyclic plastic behavior of 304 stainless steel at large temperature ranges

    Ohno N.

    Key Engineering Materials 

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    Event date: 2017

    Language:English   Presentation type:Oral presentation (general)  

    DOI: 10.4028/www.scientific.net/KEM.725.275

    Scopus

  3. Swelling-induced buckling analysis of gel films with a square lattice of holes subjected to uniaxial pretension International conference

    D. Okumura, A. Sasaki, N. Ohno

    7th Korea-Japan Workshop on Computational Mechanics, COSEIK-JSCES Joint Workshop 2015 KOREA 

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    Event date: 2015.4

    Language:English   Presentation type:Oral presentation (invited, special)  

    Country:Korea, Republic of  

  4. Effect of strain hardening on monotonic and cyclic loading behavior of plate-fin structures with two pore pressures International conference

    S. Banno, D. Okumura, N. Ohno

    12th Asia-Pacific Conference on Engineering Plasticity and Its Applications (AEPA2014) 

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    Event date: 2014.9

    Language:English   Presentation type:Oral presentation (general)  

    Country:Taiwan, Province of China  

  5. ゲル膜の膨潤誘起パターン変態の有限要素解析

    奥村大

    日本ゴム協会 第19回ゴムの力学研究分科会 

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    Event date: 2014.8

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

    Country:Japan  

  6. Effects of prestrains on swelling induced buckling patterns of gel film with square lattice of holes International conference

    D. Okumura, T. Inagaki, N. Ohno

    17th U.S. National Congress of Theoretical and Applied Mechanics (USNCTAM2014) 

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    Event date: 2014.6

    Language:English   Presentation type:Oral presentation (general)  

    Country:United States  

  7. Finite element analysis of swelling induced buckling of gel film with holes in square array International conference

    D. Okumura, T. Kuwayama, N. Ohno

    5th Asia Pacific Congress on Computational Mechanics (APCOM2013) & 4th International Symposium on Computational Mechanics (ISCM2013) 

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    Event date: 2013.12

    Language:English   Presentation type:Oral presentation (invited, special)  

    Country:Singapore  

  8. Effects of geometrical imperfection on swelling induced buckling patterns of gel film with square lattice of holes International conference

    D. Okumura, T. Kuwayama, N. Ohno

    SES 50th Annual Technical Meeting and ASME-AMD Annual Summer Meeting 

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    Event date: 2013.7

    Language:English   Presentation type:Oral presentation (general)  

    Country:United States  

  9. 離散転位塑性法を用いた塑性寸法効果のミクロ/マクロ解析

    奥村 大

    NIMS-iSM特別セミナー 

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    Event date: 2012.12

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

    Venue:物質・材料研究機構(NIMS)千現地区   Country:Japan  

  10. Homogenization analysis of microstructural effects on compressive strength of elastic multilayered corrugated paperboard International conference

    Dai Okumura, Nobutada Ohno, Takayuki Onoda, Masataka Soga

    ICOME2012/JASCOME symposium 2012 

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    Event date: 2012.12

    Language:English   Presentation type:Oral presentation (general)  

    Country:Japan  

  11. Homogenization Analysis of Compressive Strength of Elastic Multilayered Corrugated Paperboard International conference

    Dai Okumura, Takayuki Onoda, Masataka Soga, Nobutada Ohno

    International Computational Mechanics Symposium 2012(ICMS2012) 

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    Event date: 2012.10

    Language:English   Presentation type:Oral presentation (general)  

    Country:Japan  

  12. Homogenization analysis of plastic size effects using discrete dislocation plasticity approach International conference

    Dai Okumura and Nobutada Ohno

    KSME-JSME Joint Symposium on Computational Mechanics & CAE 2012 

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    Event date: 2012.9

    Language:English   Presentation type:Oral presentation (invited, special)  

    Country:Japan  

  13. ひずみこう配結晶塑性理論を用いた多結晶モデルの有限要素解析

    奥村 大,柴田智行,大野信忠

    M&M2007材料力学カンファレンス 

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    Event date: 2007.10

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  14. 寸法依存性結晶塑性論~結晶粒径と降伏応力~

    奥村 大,大野信忠

    日本塑性加工学会 プロセッシング計算力学分科会 第14回セミナー日本鉄鋼協会数理モデリングフォーラム特別講演会「材料のマイクロ組織とモデリングおよび東京農工大桑原研究室見学」 

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    Event date: 2007.9

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

    Country:Japan  

  15. Finite element analysis using strain gradient crystal plasticity theory based on self-energy of GNDs International conference

    9th US National Congress on Computational Mechanics (USNCCM9) 

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    Event date: 2007.7

    Language:English   Presentation type:Oral presentation (general)  

  16. ひずみこう配結晶塑性理論を用いた結晶粒モデルの有限要素解析

    奥村 大,柴田智行,住田浩一,大野信忠

    日本材料学会第56期学術講演会 

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    Event date: 2007.5

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  17. GN転位の自己エネルギーを考慮したひずみこう配理論と降伏応力の粒径依存性

    大野信忠,奥村 大,住田浩一

    第56回理論応用力学講演会 

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    Event date: 2007.3

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  18. ひずみこう配結晶塑性理論を用いた多結晶塑性解析における付加的境界条件の影響

    奥村 大,住田浩一,大野信忠

    第56回理論応用力学講演会 

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    Event date: 2007.3

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  19. 周期単位依存性を考慮した3次元周期材料の微視的分岐解析

    岡田篤志,奥村 大,大野信忠

    日本機械学会東海支部第56期総会・講演会 

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    Event date: 2007.3

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  20. ひずみこう配結晶塑性理論を用いた多結晶塑性の粒径依存性解析における粒界での高次境界条件の影響

    奥村 大,住田浩一,大野信忠

    日本機械学会東海支部第56期総会・講演会 

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    Event date: 2007.3

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  21. Higher-order stress and size effects due to self energy of geometrically necessary dislocations International conference

    Proceedings of ICES2007 

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    Event date: 2007.1

    Language:English   Presentation type:Oral presentation (general)  

  22. GN転位の自己ひずみエネルギーを考慮したひずみこう配結晶塑性理論による有限要素法解析

    奥村 大,住田浩一,大野信忠

    第19回計算力学講演会 

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    Event date: 2006.11

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  23. Long wavelength buckling of cubic open-cell foams subjected to uniaxial compression International conference

    Asian Pacific Conference for Fracture and Strength '06 (APCFS'06) 

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    Event date: 2006.9

    Language:English   Presentation type:Poster presentation  

  24. ケルビンセルフォームの微視的座屈に関する異方性の影響

    岡田篤志,大野信忠,奥村 大

    M&M2006材料力学カンファレンス 

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    Event date: 2006.8

    Language:Japanese   Presentation type:Poster presentation  

    Country:Japan  

  25. GN転移の自己ひずみエネルギーに基づくひずみこう配理論

    大野信忠,奥村 大

    M&M2006材料力学カンファレンス 

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    Event date: 2006.8

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  26. 幾何学的に必要な転移の弾性ひずみエネルギーを考慮した非局所結晶塑性解析

    奥村 大,住田浩一,大野信忠

    M&M2006材料力学カンファレンス 

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    Event date: 2006.8

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  27. GN転位の自己ひずみエネルギーを考慮した非局所結晶塑性解析

    奥村 大,住田浩一,大野信忠

    日本材料学会第55期学術講演会 

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    Event date: 2006.5

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  28. GN転位の自己ひずみエネルギーに基づくひずみこう配理論

    大野信忠,奥村 大

    日本材料学会第55期学術講演会 

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    Event date: 2006.5

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  29. 均質化法による3次元ケルビンセルフォームの微視的座屈解析

    奥村大,岡田篤志,大野信忠

    日本材料学会東海支部第1回学術講演会 

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    Event date: 2006.3

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  30. 均質化法に基づくケルビンフォームの微視的座屈解析

    岡田篤志,大野信忠,奥村大

    日本機械学会東海支部第55期総会・講演会 

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    Event date: 2006.3

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  31. 均質化法に基づく三次元セル構造体の微視的座屈解析

    岡田篤志,大野信忠,奥村大

    第55回理論応用力学講演会 

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    Event date: 2006.1

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  32. 面内圧縮負荷を受ける正方形弾塑性ハニカムの長波長座屈

    撰 幹士,奥村 大,大野信忠

    第18回計算力学講演会 

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    Event date: 2005.11

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  33. 非局所結晶塑性を考慮した均質化理論による多結晶金属の有限要素解析

    奥村 大,東 洋一,大野信忠

    2005年度日本機械学会年次大会 

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    Event date: 2005.9

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  34. 正方形弾塑性ハニカムの微視的分岐座屈解析

    撰 幹士,奥村 大,大野信忠

    第49回日本学術会議材料研究連合会 

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    Event date: 2005.9

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  35. 非弾性挙動を示す周期材料のマルチスケール増分解析アルゴリズム

    浅田崇史,大野信忠,奥村大

    第49回日本学術会議材料研究連合講演会 

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    Event date: 2005.9

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  36. 均質化理論による周期セル状固体の微視的分岐と巨視的不安定の解析

    奥村 大,大野信忠

    日本計算数理工学会 第9回計算数理工学フォーラム 

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    Event date: 2005.9

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

    Country:Japan  

  37. 多結晶塑性解析における粒界の取扱いとその影響

    奥村 大,大野信忠

    日本機会学会 2005年度年次大会 ワークショップ「マルチスケール多結晶塑性モデリングの考え方」 

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    Event date: 2005.9

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

    Country:Japan  

  38. A homogenization theory of nonlocal crystal plasticity for grain boundary in polycrystalline metals International conference

    8th US National Congress on Computational Mechanics(USNCCM8) 

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    Event date: 2005.7

    Language:English   Presentation type:Oral presentation (general)  

  39. 多結晶モデルの非局所結晶塑性解析における結晶粒界の影響

    奥村 大,東 洋一,大野信忠

    計算工学講演会 

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    Event date: 2005.5

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  40. 多結晶金属のための非局所結晶塑性を考慮した均質化理論の構築

    奥村 大,東 洋一,大野信忠

    日本材料学会第54期学術講演会 

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    Event date: 2005.5

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  41. FCC多結晶モデルの非局所結晶塑性解析における結晶粒界の影響

    奥村 大,東 洋一,大野信忠

    M&M信州スプリングシンポジウム 

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    Event date: 2005.3

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  42. 均質化理論に基づく多結晶材料の非局所結晶塑性解析

    奥村 大,東 洋一,大野信忠

    第54回理論応用力学講演会 

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    Event date: 2005.1

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  43. 陰的均質化理論の定式化および多結晶塑性解析への適用

    浅田崇史,大野信忠,奥村 大

    第54回理論応用力学講演会 

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    Event date: 2005.1

    Language:Japanese   Presentation type:Oral presentation (general)  

    Country:Japan  

  44. Influence of grain boundary condition on grain size dependence in polycrystal plasticity International conference

    Proceedings of ICES2005 

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    Event date: 2005

    Language:English   Presentation type:Oral presentation (general)  

  45. Incremental homogenization theory for inelastic periodic solids International conference

    11th International Symposium on Plasticity and Its Current Applications 

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    Event date: 2005

    Language:English   Presentation type:Oral presentation (general)  

  46. Long-wave buckling of square honeycombs subjected to in-plane biaxial compression International conference

    International Workshop on Development and Advancement of Computational Mechanics in Celebrating Professor Satya N. Atluri's 60th Birthday 

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    Event date: 2005

    Language:English   Presentation type:Oral presentation (general)  

    Country:Japan  

  47. 均質化理論に基づく非局所結晶塑性の有限要素解析

    奥村 大,大野信忠,東 洋一

    第17回計算力学講演会講演論文集 

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    Event date: 2004.11

    Language:Japanese   Presentation type:Oral presentation (general)  

  48. 非弾性周期構造材料に対するマルチスケール増分解析アルゴリズム

    浅田崇史,大野信忠,奥村 大

    第17回計算力学講演会講演論文集 

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    Event date: 2004.11

    Language:Japanese   Presentation type:Oral presentation (general)  

  49. 均質化理論に基づく非局所結晶塑性の有限要素解析手法の構築

    奥村 大,大野信忠,東 洋一

    第48回日本学術会議材料研究連合講演会講演論文集 

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    Event date: 2004.10

    Language:Japanese   Presentation type:Oral presentation (general)  

  50. 非局所結晶塑性を考慮した均質化理論の構築と有限要素解析

    奥村大,大野信忠

    日本材料学会塑性工学部門委員会塑性力学分科会 

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    Event date: 2004.8

    Language:Japanese   Presentation type:Oral presentation (invited, special)  

    Country:Japan  

  51. 多結晶モデルの有限要素解析における境界条件の影響

    奥村 大,大野信忠,中根和彦,川上 崇,高橋浩之

    M&M2004材料力学カンファレンス講演論文集 

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    Event date: 2004.7

    Language:Japanese   Presentation type:Oral presentation (general)  

  52. 均質化理論に基づく正方形ハニカムの微視的座屈解析

    奥村 大,大野信忠,新川岳史

    日本材料学会第53期学術講演会講演論文集 

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    Event date: 2004.5

    Language:Japanese   Presentation type:Oral presentation (general)  

  53. FCC多結晶モデルの有限要素解析における境界条件の影響

    奥村 大,大野信忠,中根和彦,川上 崇,高橋浩之

    第9回計算工学講演論文集 

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    Event date: 2004.5

    Language:Japanese   Presentation type:Oral presentation (general)  

  54. 多結晶モデルの有限要素解析における境界条件の影響

    大野信忠,奥村 大,中根和彦,川上 崇,高橋浩之

    日本材料学会第53期学術講演会講演論文集 

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    Event date: 2004.5

    Language:Japanese   Presentation type:Oral presentation (general)  

  55. 均質化理論に基づく正方形ハニカムの微視的分岐と巨視的不安定の解析

    新川岳史,奥村 大,大野信忠

    東海支部第53期総会講演会講演論文集 

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    Event date: 2004.3

    Language:Japanese   Presentation type:Oral presentation (general)  

  56. Elastoplastic microscopic buckling of periodic cellular solids

    International Conference on Heterogeneous Material Mechanics 

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    Event date: 2004

    Language:English   Presentation type:Oral presentation (general)  

  57. Multiscale instability analysis of corrugated fiberboard

    2nd International Conference on Multiscale, Materials Modeling (MMM-II) 

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    Event date: 2004

    Language:English   Presentation type:Oral presentation (general)  

  58. Three-Dimensional Microscopic Analysis of Inter-Laminar Area in Cross-Ply Laminate Using a Homogenization Theory

    Proc. the 2004 Int. Symp. on Micro-Nano Mechatronics and Human Science & The Fourth Symp. "Micro-Nano Mechatronics for an Information-Based Society" The 21st Century COE Program 

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    Event date: 2004

    Language:English   Presentation type:Oral presentation (general)  

  59. Multiscale buckling analyses of corrugated fiberboard

    International Congress of Theoretical and Applied Mechanics (ICTAM04) 

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    Event date: 2004

    Language:English   Presentation type:Oral presentation (general)  

  60. Elastoplastic microscopic bifurcation and post-bifurcation behavior of periodic cellular solids

    International Congress of Theoretical and Applied Mechanics (ICTAM04) 

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    Event date: 2004

    Language:English   Presentation type:Oral presentation (general)  

  61. Microscopic Bifurcation and Post-Bifurcation Behavior of Periodic Cellular Solids

    Proceedings of ICES2004 

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    Event date: 2004

    Language:English   Presentation type:Oral presentation (general)  

  62. Microscopic Bifurcation Analysis for Long-Wave In-Plane Buckling of Elastic Square Honeycombs

    Proceedings of ICES2004 

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    Event date: 2004

    Language:English   Presentation type:Oral presentation (general)  

  63. Long-wave buckling of square honeycombs subject to in-plane compression

    International Workshops on Advances in Computational Mechanics (IWACOM) 

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    Event date: 2004

    Language:English   Presentation type:Oral presentation (general)  

  64. 均質化理論によるセル状周期材料の微視的分岐解析

    奥村 大,大野信忠,野口裕久

    第52回理論応用力学講演会講演論文集 

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    Event date: 2003

    Language:Japanese   Presentation type:Oral presentation (general)  

  65. Elastoplastic microscopic bifurcastion in periodic cellular solids

    Proceedings of PLASTICITY '03 

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    Event date: 2003

    Language:English   Presentation type:Oral presentation (general)  

  66. 均質化理論に基づくハニカムの微視的座屈と巨視的局所化の解析

    奥村 大,大野信忠,野口裕久

    東海支部三重地区講演会 

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    Event date: 2003

    Language:Japanese   Presentation type:Oral presentation (general)  

  67. 均質化理論による弾塑性ハニカムの微視的座屈と巨視的局所化の解析

    奥村 大,大野信忠,野口裕久

    日本材料学会第52期学術講演会講演論文集 

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    Event date: 2003

    Language:Japanese   Presentation type:Oral presentation (general)  

  68. Microscopic Buckling and Macroscopic Instability of Periodic Cellular Solids

    International Conference on ATEM 2003, Proceedings of ATEM '03 

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    Event date: 2003

    Language:English   Presentation type:Oral presentation (general)  

  69. Microscopic buckling and macroscopic instability of periodic cellular solids

    9th International Conference on the Mechanical Behaviour of Materials (ICM9) 

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    Event date: 2003

    Language:English   Presentation type:Oral presentation (general)  

  70. 均質化理論に基づく非局所結晶塑性の解析

    奥村 大,大野信忠

    第53回理論応用力学講演会講演論文集 

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    Event date: 2003

    Language:Japanese   Presentation type:Oral presentation (general)  

  71. 均質化理論に基づくハニカムの微視的分岐と巨視的不安定の解析

    新川岳史,奥村 大,大野信忠

    第16回計算力学講演会講演論文集 

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    Event date: 2003

    Language:Japanese   Presentation type:Oral presentation (general)  

  72. 均質化理論に基づく非局所結晶塑性解析

    奥村 大,大野信忠

    第16回計算力学講演会講演論文集 

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    Event date: 2003

    Language:Japanese   Presentation type:Oral presentation (general)  

  73. Microscopic Inter-Laminar Analysis of CFRP Cross-Ply Laminates Using a Homogenization Theory

    Proceedings of IMMM2003 

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    Event date: 2003

    Language:English   Presentation type:Oral presentation (general)  

  74. A homogenization framework for analysis of microscopic buckling of cellular solids

    Proceedings of PLASTICITY '02 

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    Event date: 2002

    Language:English   Presentation type:Oral presentation (general)  

  75. 均質化理論に基づく正六角形弾塑性ハニカムの面内座屈解析

    奥村 大,大野信忠,野口裕久

    第15回計算力学講演会講演論文集 

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    Event date: 2002

    Language:Japanese   Presentation type:Oral presentation (general)  

  76. 均質化理論に基づく周期材料の微視的分岐条件

    奥村 大,大野信忠,野口裕久

    第7回計算工学講演会講演論文集 

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    Event date: 2002

    Language:Japanese   Presentation type:Oral presentation (general)  

  77. 均質化理論による弾塑性ハニカムの面内座屈解析

    奥村 大,大野信忠,野口裕久

    東海支部第51期総会講演会講演論文集 

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    Event date: 2002

    Language:Japanese   Presentation type:Oral presentation (general)  

  78. 有限変形の均質化理論に基づくハニカムの面内座屈後解析

    奥村 大,小濱由紀,大野信忠,野口裕久

    東海支部第50期総会講演会講演論文集 

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    Event date: 2001

    Language:Japanese   Presentation type:Oral presentation (general)  

  79. 均質化理論によるハニカムの面内座屈後解析

    奥村 大,大野信忠,野口裕久

    第14回計算力学講演会講演論文集 

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    Event date: 2001

    Language:Japanese   Presentation type:Oral presentation (general)  

  80. Microscopic Bifurcation Analysis of Cellular Solids: Theory and Computation

    Proceedings of ICES '01 

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    Event date: 2001

    Language:English   Presentation type:Oral presentation (general)  

  81. 周期材料の自由表面および巨視的界面近傍における微視的解析

    大野信忠,石川琢也,松田哲也,奥村 大,野口裕久

    日本機械学会材料力学部門講演会講演論文集 

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    Event date: 2001

    Language:Japanese   Presentation type:Oral presentation (general)  

  82. Analysis of Microscopically Symmetric Bifurcation of Cellular Solids Based on a Homogenization Theory

    INTERNATIONAL SYMPOSIA ON MATERIALS SCIENCE FOR THE 21ST CENTURY (ISMS-21) 

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    Event date: 2001

    Language:English   Presentation type:Oral presentation (general)  

  83. Microscopic symmetric bifurcation condition of cellular solids based on a homogenization theory of finite deformation

    Proceedings of IMMM2001 

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    Event date: 2001

    Language:English   Presentation type:Oral presentation (general)  

  84. 均質化理論によるハニカムの内面座屈後解析

    奥村 大, 小濱由紀, 大野忠信, 野口裕久

    第6回計算工学講演会論文集 

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    Event date: 2001

    Language:Japanese   Presentation type:Oral presentation (general)  

  85. Stability of microscopic buckling modes of honeycombs subject to in-plane biaxial compression

    IUTAM'01 symposium, Material Instabilities and the Effect of Microstructure 

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    Event date: 2001

    Language:English   Presentation type:Oral presentation (general)  

  86. 更新ラグランジュ形式による有限変形の均質化法の定式化について

    大野信忠,奥村 大

    第49回理論応用力学講演会講演論文集 

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    Event date: 2000

    Language:Japanese   Presentation type:Oral presentation (general)  

  87. 有限変形の均質化理論に基づくハニカムの面内座屈解析

    奥村 大,大野信忠,野口裕久

    第13回計算力学講演会講演論文集 

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    Event date: 2000

    Language:Japanese   Presentation type:Oral presentation (general)  

  88. A Homogenization Theory of Finite Deformation: Formulation and Application to Buckling Analysis of Honeycombs

    Proceedings of ICES 2000 

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    Event date: 2000

    Language:English   Presentation type:Oral presentation (general)  

  89. 均質化理論に基づくセル状固体の対称分岐座屈条件

    大野信忠,奥村 大,野口裕久

    日本機械学会材料力学部門講演会講演論文集 

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    Event date: 2000

    Language:Japanese   Presentation type:Oral presentation (general)  

  90. 有限変形の均質化理論によるハニカムの座屈解析

    大野信忠,奥村 大,野口裕久

    日本機械学会東海支部第49期総会講演会講演論文集 

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    Event date: 2000

    Language:Japanese   Presentation type:Oral presentation (general)  

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Other research activities 4

  1. Research Gate: https://www.researchgate.net/profile/Dai-Okumura

  2. Publons: https://publons.com/researcher/4421200/dai-okumura/

  3. ORCID: https://orcid.org/0000-0002-4020-8258

  4. Google Scholar: https://scholar.google.com/citations?user=uY5i9UkAAAAJ&hl=en

Research Project for Joint Research, Competitive Funding, etc. 1

  1. 鉄鋼材料の高精度弾塑性解析技術開発

    2008.4 - 2009.3

    企業からの受託研究 

KAKENHI (Grants-in-Aid for Scientific Research) 13

  1. 摂動解析の動的非線形化による凸凹パターン変態の全貌解明

    Grant number:22K18284  2022.6 - 2025.3

    日本学術振興会  科学研究費助成事業  挑戦的研究(開拓)

    奥村 大, 永島 壮, 松原 成志朗

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    Authorship:Principal investigator 

    Grant amount:\25740000 ( Direct Cost: \19800000 、 Indirect Cost:\5940000 )

    以下のように研究項目①~④を設定し研究目的を遂行する.
    研究項目① 摂動解析の動的非線形化による孤立クリースの基礎的解析
    研究項目② クリース解析におけるメッシュ依存性の制御方法の解析基盤構築
    研究項目③ プレパターンを用いた3次元凸凹パターン変態の評価・観察手法構築
    研究項目④ 凸凹パターン変態の全貌解明と検証実験
    本研究では,摂動解析の動的非線形化による凸凹パターン変態の全貌解明を目的とする研究課題に取り組んでおり,今年度の研究業績は以下のようにまとめられる.まず,摂動解析の動的非線形化による孤立クリースの基礎的解析の研究項目について,この手法を用いて,リンクル開始点からクリース開始点に繋がる不安定経路の存在を明らかにした.また,連鎖モデルを新しく構築して理論的な説明とパラメータ同定にも成功しており,論文を投稿準備中,次年度中に論文化する見込みである.続いて,クリース解析におけるメッシュ依存性の制御方法の解析基盤構築の研究項目について,上述の不安定経路の解析によって,クリースの前駆変形の特徴寸法と要素分割の関係が明らかとなっており,これらの情報に基づく基盤構築が予定されている.さらに,プレパターンを用いた3次元凸凹パターン変態の評価・観察手法構築の研究項目では,ゲル化過程のダイナミクスに基づくパターン変態観察手法の開発に成功しており(Nagashima et al., Langmuir, 2023),この手法と組み合わせて研究を進める.プレパターン作成のために,次年度,3次元プリンタを購入して取り組む.その他の実績としては,ゲルの粘弾性特性を研究した論文が掲載可(Matsubara et al., Adv. Struct. Mater., accepted)となっており,リンクルパターンからリッジと呼ばれる波長に対して振幅の大きなパターンの発生機構の解析の分岐座屈特性も明らかとなった(田中ら,計算数理工学論文集,2022).これらの成果も,今後の研究の展開に関わる材料物性や変態特性を含んでおり,相乗的な進展を期待している.
    研究業績の概要に記載したように,研究課題はおおむね順調に進んでいる.とりわけ,まだ業績としては確定していないが,摂動解析の動的非線形化による孤立クリースの基礎的解析に成功していることが重要である.これまで未解明であった分岐座屈としてのリンクルの発生と単純な分岐ではないとみなされていたクリースの発生の間の合理的な説明を可能とする計算モデルと理論の構築に成功しており,申請者らの極めて独自性の高い成果である.これに関連して,計算の研究項目も進展が期待されている.実験については,ゲル化過程のパターン変態という,申請者らの独自の手法を用いて,溶媒吸収という時間のかかる現象によらないパターン変態の再現と観察の方法を構築しており,この手法からの発展として成果の獲得に期待している.以上のことから,本研究プロジェクトは実験だけでなく,理論や計算の側面からも着実に進展しており,順調に進んでいると考えられる.
    今後の推進方策として,2年目の次年度は,摂動解析の動的非線形化による孤立クリースの基礎的解析に関する論文を注目度の高い国際雑誌に掲載させることが重要となる.クリースの発生はハーフスペースの表面で発生するスケールフリーの特徴を有するが,発達過程は膜厚などの寸法に依存する.このため,単層だけでなく二層構造体の場合の発達過程の評価も重要になる.実験では,プレパターンと呼んでいる欠陥を導入することによって,パターンの制御を試みる.パターン間のエネルギー差は小さいと予測され,欠陥の導入精度が重要となるが,超微細3次元プリンタを用いてこの問題を解決できることを期待している.

  2. Coexistence of wrinkles and folds in film&#8211;substrate systems in contact with water droplets

    Grant number:22H01360  2022.4 - 2025.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

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    Authorship:Coinvestigator(s) 

  3. The advancement of gel material modeling and the bifurcation buckling analysis frontier of growth-induced morphogenesis

    Grant number:19H00739  2019.4 - 2023.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (A)

    Okumura Dai

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    Authorship:Principal investigator  Grant type:Competitive

    Grant amount:\46670000 ( Direct Cost: \35900000 、 Indirect Cost:\10770000 )

    This research project aimed at the advancement of gel material modeling and the bifurcation buckling analysis frontier of growth-induced morphogenesis. In the gel material modeling, the Flory-Rehner free energy form is generally considered, and the theoretical solution for evaluating the state-dependent elastic properties is derived in a general form. Experimental studies were also carried out to clarify the molecular chain extensibility effect and the viscosity effect. By applying the step-by-step eigenvalue buckling analysis proposed by the representative, we succeeded in clarifying the process on the bifurcation path for the relationship between the complex deformation pattern and the bifurcation mode. Furthermore, it was demonstrated that pattern transformation can be induced by combining the mechanisms of the gelation process.

  4. Step-by-step eigenvalue buckling analysis of dimple pattern transformation in hard film on soft substrate

    Grant number:17K18826  2017.6 - 2019.3

    Grant-in-Aid for Challenging Research (Exploratory)

    Okumura Dai

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    Authorship:Principal investigator  Grant type:Competitive

    Grant amount:\6370000 ( Direct Cost: \4900000 、 Indirect Cost:\1470000 )

    In the present study, we analyzed the pattern transformation occurring in hard gel films on a soft substrate to elucidate its mechanism. To this end, we first developed the computational procedures of step-by-step eigenvalue buckling analysis, applying it to buckling and postbuckling of etching-induced wiggling in a bilayer structure with intrinsic compressive stress. The developed procedures were applied to the dimple pattern transformation analysis, and the efficiency was validated. It was successfully found that the checkerboard problem depends on the swelling effect and the bifurcation subsequent to the first bifurcation.

  5. 軟質基盤上の硬質膜に生じる凸凹パターン変態の探索的分岐不安定解析

    2017.4 - 2019.3

    科学研究費補助金  研究成果公開促進費 (研究成果公開発表)

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    Authorship:Principal investigator 

  6. Prediction and mechanism of swelling-induced instability in polymeric gels

    Grant number:16H04234  2016.4 - 2019.3

    Okumura Dai

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    Authorship:Principal investigator  Grant type:Competitive

    Grant amount:\17810000 ( Direct Cost: \13700000 、 Indirect Cost:\4110000 )

    In the present study, we developed the theories, numerical methods, and experimental approaches to predict and elucidate the mechanism of swelling-induced instability of polymeric gels. First, the characteristic of the extended Flory-Rehner model, developed by Okumura et al. (2016) using two scaling exponents, was analyzed under consideration of biaxial deformation and mass transport. In the analysis of swelling-induced instability, stable and efficient incremental approaches were investigated and proposed. Furthermore, experiments supported the validity and usefulness of the extended model. Accurate strain distribution measurement of the sample surface was achieved using a digital image correlation method.

  7. ポーラスゲル膜に生じる膨潤誘起パターン変態の発生発達分化の機構解明と設計基盤構築

    2015.4 - 2017.3

    科学研究費補助金 

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    Authorship:Principal investigator 

  8. Analysis of swelling-induced pattern transformation of porous gel films

    Grant number:15K13829  2015.4 - 2017.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Challenging Exploratory Research

    Okumura Dai

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    Authorship:Principal investigator  Grant type:Competitive

    In this study, finite element analysis of swelling-induced pattern transformation in porous gel films is analyzed. An inhomogeneous field theory for polymeric gels is implemented as a user-defined material subroutine into the finite element package Abaqus. Swelling process is analyzed by increasing the chemical potential of external solvent. To investigate the point of buckling and the buckling mode, eigenvalue buckling prediction is conducted using a quasi incremental loading pattern. This approach is verified by changing the base state. It is found that the second buckling point appears for causing transformation into S shaped patterns, when the pitch-to-diameter ratio is small, while no pattern transformation occurs when the pitch-to-diameter ratio is large.

  9. ゲル材料の膨潤分岐座屈解析のための理論構築と検証及び応用

    2012.4 - 2015.3

    科学研究費補助金  基盤研究(C)

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    Authorship:Principal investigator 

  10. 転位の長距離力を直接導入したマイクロ・ナノ塑性理論の構築と検証

    2010.4

    科学研究費補助金  若手研究(B),課題番号:22760074

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    Authorship:Principal investigator 

  11. 転位の離散的特性を考慮した非局所結晶塑性理論の構築とマルチスケール解析による検証

    2008.4 - 2010.3

    科学研究費補助金  若手研究(B),課題番号:20760069

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    Authorship:Principal investigator 

  12. 非局所結晶塑性理論に基づく多結晶塑性の大規模マルチスケール解析

    2006.4 - 2008.3

    科学研究費補助金  若手研究(B),課題番号:18760080

    奥村 大

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    Authorship:Principal investigator 

  13. 非局所結晶塑性を考慮した均質化理論に基づく大規模マルチスケール解析

    2004.4 - 2006.3

    科学研究費補助金  若手研究(B),課題番号:16760064

    奥村 大

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    Authorship:Principal investigator 

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Teaching Experience (On-campus) 10

  1. 材料科学第1

    2020

  2. 材料力学第2及び演習

    2020

  3. 固体力学特論

    2020

  4. 材料力学第2および演習

    2018

  5. 材料科学第1

    2018

  6. 固体力学特論

    2018

  7. 基礎セミナーA

    2018

  8. 応用力学大意

    2011

  9. 計算機ソフトウェア第1

    2011

  10. 材料科学第1

    2010

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Teaching Experience (Off-campus) 2

  1. ハイタレント研修専門技術「計算力学(構造解析)」演習

    2009.4 - 2010.3 デンソー技研センター)

  2. ハイタレント研修専門技術「計算力学(構造解析)」演習

    2007.4 - 2008.3 デンソー技研センター)