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Selective excitation of two-wave structure depending on crystal orientation under shock compression

Science China(Physics,Mechanics & Astronomy) 2020年第11期63卷 59-71页

作者： QiLin Xiong Takahiro Shimada takayuki kitamura ZhenHuan Li Department of Mechanics Huazhong University of Science&TechnologyWuhan 430074China Hubei Key Laboratory of Engineering Structural Analysis and Safety Assessment Wuhan 430074China Department of Mechanical Engineering and Science Kyoto UniversityKyoto 615-8540Japan

Single crystals subjected to shock compression exhibit responses with distinct two-wave structures for certain crystal ***,little is known to date regarding how the shock response depends on crystal orientation,and especially why the two-wave structure depends on the crystal *** this work,molecular dynamics simulations of shock compressions in copper single crystals are performed to investigate the orientation dependence of shock responses and the corresponding deformation *** copper single crystals with[001],[011],[012],and[123]crystal orientations along the depth direction are ***[011],[012],and[123]crystal orientations of copper single crystals show distinct two-wave structures in their shock responses,while such a two-wave structure in the shock response is not seen for those orientations having a[001]crystal *** potential causes are analyzed by considering the propagation velocities of both elastic and plastic *** develop a technique for identifying twin structures in face-centered cubic crystals and this technique can effectively identify the twin *** morphology of shock-induced defects(e.g.,dislocations and twins)shows the significant dependence of crystal orientation and the mechanisms behind these are discussed in ***,the Johnson-Cook constitutive model describing dynamic deformations at high temperatures and high strain rates is used to analyze the relationships between the shock responses and microscopic *** predictions of the Johnson-Cook constitutive model are consistent with the results of the molecular dynamics simulations.

关键词： orientation-dependent two-wave structure shock compression copper molecular dynamics

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A Nano-Cantilever Method for Crack Initiation at the Free Edge of the Cu/Si Interface in Nanoscale Components

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Acta Mechanica Solida Sinica 2016年第4期29卷 416-428页

作者： Xiaoyuan Wang Yabin Yan Qiang Wan Takashi Sumigawa takayuki kitamura Institute of Systems Engineering China Academy of Engineering Physics Department of Mechanical Engineering and Science Kyoto University

Straight and Bent nano-cantilever specimens are respectively proposed to investigate the single-mode and mixed-mode crack initiation at the Cu/Si interface edge in nanoscale components. With a minute loading apparatus, all nanoscale samples are in situ loaded and observed. Numerical analysis is employed to acquire the critical interfacial stress distributions during crack initiation. The stress concentration regions near the edge of Cu/Si interface in all specimens are within the scale of 100 nm, and the critical normal and shear stresses have a circular relation in nanoscale components, which represents the fracture criterion of the interface in nanoscale components.

关键词： nanoscale cantilever interface crack initiation mixed mode thin film

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Self-shaping of bioinspired chiral composites

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Acta Mechanica Sinica 2014年第4期30卷 533-539页

作者： Qing-Qing Rong Yu-Hong Cui Takahiro Shimada Jian-Shan Wang takayuki kitamura Tianjin Key Laboratory of Modern Engineering Mechanics Department of MechanicsTianjin University Department of Mechanical Engineering and Science Kyoto University

Self-shaping materials such as shape memory polymers have recently drawn considerable attention owing to their high shape-changing ability in response to changes in ambient conditions, and thereby have promising applications in the biomedical, biosensing, soft robotics and aerospace fields. Their design is a crucial issue of both theoretical and technological interest. Motivated by the shape-changing ability of Towel Gourd tendril helices during swelling/deswelling, we present a strategy for realizing self-shaping function through the deformation of micro/nanohelices. To guide the design and fabrication of selfshaping materials, the shape equations of bent configurations, twisted belts, and helices of slender chiral composite are developed using the variation method. Furthermore, it is numerically shown that the shape changes of a chiral composite can be tuned by the deformation of micro/nanohelices and the fabricated fiber directions. This work paves a new way to create self-shaping composites.

关键词： Self-shaping · Bioinspired chiral composites ·Micro/nanohelices · Tendrils

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Linear-superelastic Ti-Nb nanocomposite alloys with ultralow modulus via high-throughput phase-field design and machine learning

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npj Computational Materials 2021年第1期7卷 1897-1906页

作者： Yuquan Zhu Tao Xu Qinghua Wei Jiawei Mai Hongxin Yang Huiran Zhang Takahiro Shimada takayuki kitamura Tong-Yi Zhang Materials Genome Institute Shanghai UniversityShanghai 200444China Ningbo Institute of Materials Technology and Engineering Chinese Academy of SciencesNingbo 315201China School of Computer Engineering and Science Shanghai UniversityShanghai 200444China Department of Mechanical Engineering and Science Kyoto UniversityNishikyo-kuKyoto 615-8540Japan

The optimal design of shape memory alloys(SMAs)with specific properties is crucial for the innovative application in advanced ***,inspired by the recently proposed design concept of concentration modulation,we explore martensitic transformation(MT)in and design the mechanical properties of Ti-Nb nanocomposites by combining high-throughput phase-field simulations and machine learning(ML)*** phase-field simulations generate data of the mechanical properties for various nanocomposites constructed by four macroscopic degrees of *** ML-assisted strategy is adopted to perform multiobjective optimization of the mechanical properties,through which promising nanocomposite configurations are prescreened for the next set of phase-field *** ML-guided simulations discover an optimized nanocomposite,composed of Nb-rich matrix and Nb-lean nanofillers,that exhibits a combination of mechanical properties,including ultralow modulus,linear superelasticity,and near-hysteresis-free in a loading-unloading *** exceptional mechanical properties in the nanocomposite originate from optimized continuous MT rather than a sharp first-order transition,which is common in typical *** work demonstrates the great potential of ML-guided phase-field simulations in the design of advanced materials with extraordinary properties.

关键词： alloys modulus phase

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Electron engineering of metallic multiferroic polarons in epitaxial BaTiO_(3)

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npj Computational Materials 2019年第1期5卷 940-946页

作者： Tao Xu Takahiro Shimada Yasumitsu Araki Masataka Mori Gen Fujimoto Jie Wang Tong-Yi Zhang takayuki kitamura Materials Genome Institute Shanghai UniversityShanghai Materials Genome InstituteShanghai 200444China Department of Mechanical Engineering and Science Kyoto UniversityNishikyo-kuKyoto 615-8540Japan Department of Engineering Mechanics School of Aeronautics and AstronauticsZhejiang UniversityHangzhou 310027China

The coexistence of ferroelectricity,conductivity,and magnetism in a single-phase material has attracted considerable attention due to fundamental interest and tremendous technological ***,their mutually exclusive mechanisms hinder the discovery of multifunctional conducting ***,we propose a new material design approach for electron engineering to enable these conflicting properties to *** use first principles calculations to demonstrate that appropriate mechanical strain can turn the excess electrons in doped BaTiO_(3) from a free-carrier configuration to a localized polaronic state by modulating the electron–phonon *** resulting localized spin-polarized electron survives the host ferroelectricity and consequently manifests as a multiferroic *** multiferroic properties coexist with the electronic conductivity arising from the highhopping mobility of the polaron,which enables the doped epitaxial BaTiO_(3) to act as a multiferroic conducting *** mechanical control over the electron configuration is a potential path toward unusual coexisting properties.

关键词： properties polaron ferroelectric

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Low Frequency Ultrasonication Induced Antitumor Effect in 5-Aminolevulinic Acid Treated Malignant Glioma

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Journal of Cancer Therapy 2013年第1期4卷 170-175页

作者： Fumio Yamaguchi takayuki Asakura Hiroshi Takahashi takayuki kitamura Akira Teramoto Department of Neurosurgery Nippon Medical School Tokyo Japan

We investigated the feasibility of sonodynamic therapy for glioma by low frequency ultrasoundwith5-aminolevulinic acid (5-ALA), a precursor of protoporphyrin IX (PpIX) in heme synthetic process. In vivo tumor model was made by inoculating human glioma cell line U87-MG subcutaneously in nude mice. The tumor was sonicated by 25-kHz ultrasound 4 hours following administration of 5-ALA. The tumor size decreased in 5-ALA administered (ALA(+)US(+)) mice, while increased in non-5-ALA administrated (ALA(-)US(+)) mice and non-sonicated mice (ALA(+)US(-)). The immunohistochemical analysis revealed an apoptotic change in tumor tissue of ALA(+)US(+) mice. The results showed the therapeutic effect of 25 kHz ultrasound for the glioma in 5-ALA administered tumor-bearing mice by inducing apoptotic change of tumor cells. This is a first report to elucidate the feasibility of therapeutic use of 25 kHz, relatively low frequency, ultrasound in sonodynamic therapy using 5-ALA as a sonosensitizer precursor. The utilization of this frequency will contribute to the development of sonodynamic therapy for gliomas and the spread of this technique in many hospitals that possess ultrasonic aspirators.

关键词： Glioma Sonodynamic Therapy 5-Aminolevulinic Acid Protoporphyrin IX Ultrasonication

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界面裂纹萌生与扩展的分子动力学模拟

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力学学报 2007年第4期39卷 571-576页

作者：尚福林北村隆行西安交通大学航天航空学院工程力学系/强度与振动教育部重点实验室西安710049 京都大学大学院工学研究科机械理工学专攻

运用分子动力学模拟方法研究了裂纹在界面端处萌生与沿界面扩展的临界条件．模拟考虑了一双相材料的3种模型,即构成90°/90°和90°/°夹角的两个界面端和一个界面裂纹．模拟采用了包含原子区域与连续区域的并发型多尺度模型,即在界面... 详细信息

运用分子动力学模拟方法研究了裂纹在界面端处萌生与沿界面扩展的临界条件．模拟考虑了一双相材料的3种模型,即构成90°/90°和90°/°夹角的两个界面端和一个界面裂纹．模拟采用了包含原子区域与连续区域的并发型多尺度模型,即在界面端尖端和裂纹尖端附近采用分子动力学(MD)方法,MD区域之外则按照线弹性有限元方法分析．结果表明,在断裂启动时刻,3个模型沿界面的最大应力均达到界面理想强度;而且,其界面能恰好足以克服界面材料的本征内聚能．因此,界面端裂纹萌生与沿界面扩展的断裂条件可以通过界面理想强度和内聚能联系起来．并基于模拟计算结果提出了界面断裂启动的统一准则．

关键词：断裂界面裂纹界面端分子动力学模拟

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Disappearance of ferroelectric critical thickness in epitaxial ultrathin BaZrO3 films

Disappearance of ferroelectric critical thickness in epitaxi...

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中国力学大会-2015

作者：张亚君王杰 Shimada Takahiro kitamura takayuki 浙江大学航空航天学院应用力学研究所京都大学机械科学与工程系

The intrinsic critical ferroelectric thickness of epitaxial ultrathin capacitors of incipient ferroelectric BaZrO(BZO)filmswith realistic SrRuO(SRO)electrodes is investigated by firstprinciples calculations based on d...

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Injury/ischemia-induced stem cells: up-to-date knowledge and future perspectives for neural regeneration

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Neural Regeneration Research 2025年第3期20卷 797-798页

作者： takayuki Nakagomi Institute for Advanced Medical Sciences Hyogo Medical UniversityNishinomiyaJapan Department of Therapeutic Progress in Brain Diseases Hyogo Medical UniversityNishinomiyaJapan

Brain injuries like ischemic stroke induce endogenous stem cell production. Although the precise traits of stem cells in pathological brains remain unclear, we previously demonstrated that injury/ischemia-induced stem... 详细信息

关键词： ischemia injuries

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基于FIB和TEM的纳米材料中界面分层破坏的实验方法研究与应用

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中国科学：物理学、力学、天文学 2014年第6期44卷 593-598页

作者：闫亚宾北村隆行澄川贵志中国工程物理研究院总体工程研究所绵阳621900 日本京都大学机械工程与科学系

本文针对三维尺寸均处于纳米量级的材料与结构中常见的界面分层破坏问题,利用聚焦离子束技术(FIB)和透射电子显微镜(TEM)开发设计了一套研究纳米材料中界面端部裂纹启裂行为的实验方法.采用FIB成功从宏观多层薄膜材料(硅/铜/氮化硅,Si/C... 详细信息

本文针对三维尺寸均处于纳米量级的材料与结构中常见的界面分层破坏问题,利用聚焦离子束技术(FIB)和透射电子显微镜(TEM)开发设计了一套研究纳米材料中界面端部裂纹启裂行为的实验方法.采用FIB成功从宏观多层薄膜材料(硅/铜/氮化硅,Si/Cu/SiN)中切割制备出了由硅基体(Si)和200 nm厚铜薄膜(Cu)及1000 nm厚氮化硅层(SiN)构成的纳米悬臂梁试样.利用高精度微小材料加载装置,在TEM中对该试样进行加载实验,并原位观测了不同试样中Cu/Si界面端部裂纹启裂的行为.通过对启裂瞬时Cu/Si界面上临界应力分布的有限元分析发现,不同尺寸试样中的界面上法向应力与剪切应力均集中在距界面端部100 nm的范围内,且临界法向应力远大于剪切应力.对应力分布的进一步分析则发现,距界面端部5 nm区域内的法向应力场控制着Cu/Si界面的分层破坏过程,可用于表征界面分层破坏的局部控制准则.

关键词：纳米尺度聚焦离子束系统透射电子显微镜界面裂纹启裂薄膜

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