Faculty Profiles - OKUMURA, Dai

Papers - OKUMURA, Dai

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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

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

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

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

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

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

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

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

<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

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

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

<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

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

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

Language：Japanese Publisher：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 Vol. 725 KEM page： 275 - 280 2017

Language：Japanese Publisher：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 Reviewed

奥村大

計算数理工学論文集 Vol. 17 page： 47 - 52 2017

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

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

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

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

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

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

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

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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Papers - OKUMURA, Dai