研究者詳細 - 奥村　大

<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

ポリアクリルアミドハイドロゲルを用いた拡張Flory-Rehnerモデルの実験的検証

清水章司, 奥村大, 伊田翔平, 田中展, 内田真

M&M材料力学カンファレンス 2017 巻 ( 0 ) 頁： OS0306 2017年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：一般社団法人日本機械学会

<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

ポリアクリルアミドハイドロゲルの単軸引張試験に基づく拡張 Flory-Rehner モデルと Ogden モデルの比較解析

清水章司, 奥村大, 伊田翔平, 田中展, 内田真

計算力学講演会講演論文集 2017.30 巻 ( 0 ) 頁： 241 2017年

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

Okumura D., Mizutani M.

Key Engineering Materials 725 KEM 巻頁： 427 - 432 2017年

記述言語：日本語出版者・発行元：Key Engineering Materials

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

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

Ohno N., Yamamoto R., Okumura D.

Key Engineering Materials 725 KEM 巻頁： 275 - 280 2017年

記述言語：日本語出版者・発行元：Key Engineering Materials

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

高分子ゲルの拡張Flory-Rehnerモデルを用いた線形摂動解析査読有り

奥村大

計算数理工学論文集 17 巻頁： 47 - 52 2017年

Using two scaling exponents to describe the mechanical properties of swollen elastomers 査読有り

D Okumura, A Kondo, N Ohno

Journal of the Mechanics and Physics of Solids 90 巻頁： 61 - 76 2016年

Swelling-induced buckling patterns in gel films with a square lattice of holes subjected to in-plane uniaxial and biaxial pretensions 査読有り

D. Okumura, A. Sasaki, N. Ohno

Advanced Structured Materials 64 巻頁： 319-334 2015年6月

Effects of prestrains on swelling induced buckling patterns of gel film with square lattice of holes 査読有り

D. Okumura, T. Inagaki, N. Ohno

International Journal of Solids and Structures 58 巻頁： 288-300 2015年4月

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）査読有り

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 81 巻頁： 0-0 2015年

Effect of strain hardening on monotonic and cyclic loading behavior of plate-fin structures with two pore pressures 査読有り

S. Banno, D. Okumura, N. Ohno

Key Engineering Materials 626 巻頁： 133-138 2015年

Elastic-viscoplastic implicit integration algorithm applicable to both plane stress and three-dimensional stress states 査読有り

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

Finite Elements in Analysis and Design 頁： 00-00 2015年

Effect of geometrical imperfections on swelling-induced buckling patterns in gel films with a square lattice of holes 査読有り

D. Okumura, T. Kuwayama, N. Ohno

International Journal of Solids and Structures 51 巻 ( 1 ) 頁： 154-163 2014年1月

Homogenized elastic-viscoplastic behavior of plate-fin structures with two pore pressures 査読有り

N. Ohno, K. Narita, D. Okumura

International Journal of Mechanical Sciences 86 巻頁： 18-25 2014年

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