著者

益田 快理 Le Van Lich 嶋田 隆広 北村 隆行

出版者

一般社団法人 日本機械学会

雑誌

日本機械学会論文集 (ISSN:21879761)

巻号頁・発行日

vol.85, no.876, pp.19-00175, 2019 (Released:2019-08-25)

参考文献数

26

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Ferroelectric behavior in mechanically strained SrTiO3 nanoporous is investigated using phase-field models. We find, in the paraelectric nanoporous, periodically arrayed ferroelectric nano-region is formed due to strain concentration, namely, polarization vortices emerge around each pore. Each ferroelectric region expands and connects each other with increasing strain, and ferroelectric network is finally formed. Since these ferroelectric regions can be regarded as a periodically arrayed ferroelectric nanomaterial embedded in a paraelectric material, this result means that periodically arrayed ferroelectric nanostructure, which may lead to novel functionalities, can be tailored through mechanical load. In addition, we find that the variation of load changes the geometrical characteristics of the ferroelectric structure such as shape and direction. Our finding provides a new concept to engineer future ferroelectric nanodevices by giving a new role to mechanical load.

著者

北村 隆行 澄川 貴志 平方 寛之 高橋 可昌 嶋田 隆広

出版者

京都大学

雑誌

特別推進研究

巻号頁・発行日

2013

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single digit ナノスケール(1nm ~ 10nm)の応力特異場を有する材料に対するその場観察破壊実験方法を開発し、シリコン単結晶の実験より特異場寸法4nmであっても破壊靭性値は不変であることを明らかにした。また、第一原理解析と実験が一致することを示すとともに、応力特異場が2nm以下の場合に従来の破壊力学基準が破綻する(連続体破壊力学の適用下限)ことを明らかにした。

著者

北村 隆行

出版者

社団法人日本鉄鋼協会

雑誌

鐵と鋼 : 日本鐡鋼協會々誌 (ISSN:00211575)

巻号頁・発行日

vol.76, no.8, pp.1400-1401, 1990-08-01

著者

北村 隆行 屋代 如月 大谷 隆一

出版者

一般社団法人日本機械学会

雑誌

日本機械学會論文集. A編 (ISSN:03875008)

巻号頁・発行日

vol.62, no.600, pp.1813-1819, 1996-08-25

被引用文献数

5

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In order to elucidate the mechanism of deformation and fracture of microcomponents, numerical simulations are conducted for nanoscopic wire and film of nickel without lattice defects using molecular dynamics on the basis of the EAM (embedded atom method) potential. Applying a periodic boundary, large as well as small materials are subjected to a tensile strain along the [001] direction of the FCC (face-centered cubic) lattice. Here, the traverse stresses, σ_<xx> and σ_<yy>, in the former are kept at zero during the tension. The yield is brought about by the crystallographic slips on the (111) planes and there is little difference in the yield stresses among the wire, film and bulk. The slips continue to take place on multiple (111) planes and the plastic deformation leads to ductile fracture. Then, the displacement in the traverse direction on the cell boundaries of bulk is fixed in order to investigate the effect of constraint. It shows brittle fracture due to cleavage cracking. this implies that the constraint, which may be introduced by local inhomogeneity of the material, brings about early crack nucleation and reduces the ductility of matcrials without lattice imperfection.