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Acta Mechanica Solida Sinica 2017年第1期30卷 11-19页

作者： Q.F.Lü M.L.Deng W.Q.Zhu Department of Mechanics State Key Laboratory of Fluid Power and Mechatronic SystemsKey Laboratory of Soft Machines and Smart Devices of Zhejiang ProvinceZhejiang University

A stochastic averaging method of quasi integrable and resonant Hamiltonian systems under excitation of fractional Gaussian noise （fGn） with the Hurst index 1/2 〈 H 〈 1 is proposed. First, the definition and the basic property of fGn and related fractional Brownian motion （iBm） are briefly introduced. Then, the averaged fractional stochastic differential equations （SDEs） for the first integrals and combinations of angle variables of the associated Hamiltonian systems are derived. The stationary probability density and statistics of the original systems are then obtained approximately by simulating the averaged SDEs numerically. An example is worked out to illustrate the proposed stochastic averaging method. It is shown that the results obtained by using the proposed stochastic averaging method and those from digital simulation of original system agree well.

关键词： Quasi integrable and resonant Hamiltonian system Fractional Brownian motion Fractional Gaussian noise Stochastic averaging method Internal resonant

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Robustness of structural superlubricity beyond rigid models

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Friction 2022年第9期10卷 1382-1392页

作者： Shizhe FENG Zhiping XU Applied mechanics Laboratory Department of Engineering Mechanics and Center for Nano and Micro MechanicsTsinghua UniversityBeijing 100084China

Structural superlubricity is a theoretical concept stating that the friction force is absent between two rigid,incommensurate crystalline surfaces.However,elasticity of the contact pairs could modify the lattice registry at interfaces by nucleating local slips,favoring commeasure.The validity of structural superlubricity is thus concerned for large-scale systems where the energy cost of elastic distortion to break the lattice registry is low.In this work,we study the size dependence of superlubricity between single-crystal graphite flakes.Molecular dynamics simulations show that with nucleation and propagation of out-of-plane dislocations and strained solitons at Bernal interfaces,the friction force is reduced by one order of magnitude.Elastic distortion is much weaker for non-Bernal or incommensurate ones,remaining notable only at the ends of contact.Lattice self-organization at small twist angles perturbs the state of structural superlubricity through a reconstructed potential energy surface.Theoretical models are developed to illustrate and predict the interfacial elastoplastic behaviors at length scales beyond those in the simulations.These results validate the rigid assumption for graphitic superlubricity systems at microscale,and reveal the intrinsic channels of mechanical energy dissipation.The understandings lay the ground for the design of structural superlubricity applications.

关键词： structural superlubricity lattice registry elastic deformation strained solitons crystal plasticity molecular dynamics simulations

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高压热处理调节FeP金属玻璃空化行为

Acta Mechanica Sinica 2023年第3期39卷 198-207页

作者：唐垚周昊飞 Center for X-mechanics Department of Engineering MechanicsZhejiang UniversityHangzhou 310027China

脆性金属玻璃的空化现象可追溯其本征的高原子密度涨落.有目的地调节金属玻璃内部结构以抑制其空化行为一直是被关注的问题.本文通过分子动力学模拟研究了高压热处理对脆性Fe_(80)P_(20)金属玻璃空化行为的影响.高压热处理可诱导Fe_(80)... 详细信息

脆性金属玻璃的空化现象可追溯其本征的高原子密度涨落.有目的地调节金属玻璃内部结构以抑制其空化行为一直是被关注的问题.本文通过分子动力学模拟研究了高压热处理对脆性Fe_(80)P_(20)金属玻璃空化行为的影响.高压热处理可诱导Fe_(80)P_(20)金属玻璃发生年轻化,有效抑制空化的发生.伴随压力和温度的增加,Fe_(80)P_(20)金属玻璃的空间异质性逐渐减小,同时磷原子的分布变得相对均匀.分析表明,高压热处理可诱导Fe_(80)P_(20)金属玻璃局部原子结构从“类液态”转变为“类固态”,致使空化需要更大的外加应力诱发.上述结果为理解金属玻璃的空间异质性和空化行为之间的关联规律提供了新的思路.

关键词： Metallic glass Cavitation High pressure heat treatment Molecular dynamics simulation Spatial heterogeneity

A design and manufacturing methodology for encoded soft-textile robots

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Science China(Physics,mechanics & Astronomy) 2024年第5期67卷 212-213页

作者： Yihui Zhang Applied mechanics Laboratory Department of Engineering MechanicsTsinghua UniversityBeijing 100084China

The development of programmable soft robots with bioinspired morphing capabilities has attracted considerable interest.The mode and complexity of morphing capabilities are essential to the manipulation and movement ab... 详细信息

关键词： environments robots manipulation

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硬/软复合材料结构防爆性能的实验及数值评估

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Acta Mechanica Sinica 2022年第1期38卷 27-36页

作者：杨丰源栗志杰庄茁柳占立 Applied mechanics Laboratory Department of Engineering MechanicsSchool of AerospaceTsinghua UniversityBeijing 100084China

现实防护工程中,硬1软复合结构在人员装甲(如头盔的外壳/衬里系统)中的应用可以有效减轻爆炸伤害.由于缺乏有效可靠的实验方法评估防护结构的防爆性能,直接接触型防护结构的发展受到限制,本文针对硬/软复合材料结构的防爆性能测试提出... 详细信息

现实防护工程中,硬1软复合结构在人员装甲(如头盔的外壳/衬里系统)中的应用可以有效减轻爆炸伤害.由于缺乏有效可靠的实验方法评估防护结构的防爆性能,直接接触型防护结构的发展受到限制,本文针对硬/软复合材料结构的防爆性能测试提出一种新的实验及数值评估方法,并对其防爆机理进行了分析.受测的硬/软结构由超高分子量聚乙烯(UHMWPE)复合材料和膨胀聚乙烯(EPE)泡沫组成.现场爆炸试验通过7.0 kg TNT球形炸药在3.8 m处产生的爆炸波来完成.设计了一种压力测试装置用于支撑被测结构并测量穿透防护结构的爆炸压力脉冲.实验结果表明,通过使脉冲波形更平坦、减小压力幅度和延迟脉冲到达时间,硬/软结构可以将爆炸压力脉冲减弱为三角形压力脉冲.7mmUHMWPE复合材料和20mmEPE泡沫的组合防护结构可将爆炸压力振幅降低40%.通过有限元模拟分析爆炸缓解机制.数值结果表明,爆炸压力脉冲的衰减主要发生在硬/软界面上,通过界面反射压力波和软材料层变形吸收动能来完成.在此基础上提出的理论模型可以很好地解释实验和数值结果,对评价和设计高性能的防爆结构具有重要意义.

关键词：防爆结构防爆性能接触型压力脉冲复合材料结构脉冲到达时间爆炸试验复合结构

Molecular Dynamics Simulations of Displacement Cascade in Ni-Based Concentrated Solid Solution Alloys

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Acta Mechanica Solida Sinica 2024年第1期37卷 82-89页

作者： Chaoquan Zhao Rongxuan Xie Chuanlong Xu Xiaobao Tian Qingyuan Wang Wentao Jiang Haidong Fan Department of Mechanics Sichuan UniversityChengdu 610065China

Single-phase concentrated solid solution alloys(SP-CSAs),including high-entropy alloys,have received extensive attention due to their excellent irradiation resistance.In this work,displacement cascade simulations are conducted using the molecular dynamics method to study the evolution of defects in Ni-based SP-CSAs.Compared with pure Ni,the NiCr,NiCo,and NiCu alloys exhibit a larger number of Frankel pairs(FPs)in the thermal peak stage,but a smaller number of surviving FPs.However,the NiFe alloy displays the opposite phenomenon.To explain these different observations for NiFe and other alloys,the formation energy and migration energy of interstitials/vacancies are calculated.In the NiFe alloy,both the formation energy and migration energy barrier are higher.On the other hand,in NiCr and other alloys,the formation energy of interstitials/vacancies is lower,as is the migration energy barrier of interstitials.The energy analysis agrees well with previous observations.The present work provides new insights into the mechanism behind the irradiation resistance of binary Ni-based SP-CSAs.

关键词： Molecular dynamics simulation Displacement cascade Point defect Ni-based concentrated solid solution alloys

Mechanical effects: challenges for high-field superconducting magnets

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National Science Review 2023年第3期10卷 51-53页

作者： Xingyi Zhang Jinggang Qin the Department of Mechanics and Engineering Sciences College of Civil Engineering and Mechanics Lanzhou University the Institute of Plasma Physics Chinese Academy of Sciences

Due to its clean products and sufficient raw materials, fusion energy is expected to become one of the main solutions of the energy crisis and ensuring the sustainable development of human society,which is a long-term strategicfrontier field.The promise offusion energy is to constrain the motion of high-temperature plasma by the high magnetic field generated by superconducting magnets, and then achieve controllable thermonuclearfusion.Fusion power is proportional to the fourth power of the magnetic field strength.Thus,future commercial fusion reactors need a higher magnetic field as the basis for sustainable development [1].

关键词： Superconducting magnets

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管状上皮组织的三维形态发生

Acta Mechanica Sinica 2024年第2期40卷 237-243页

作者：于鹏宇李博 Institute of Biomechanics and Medical Engineering Applied Mechanics LaboratoryDepartment of Engineering MechanicsTsinghua UniversityBeijing100084China

管状上皮组织是组成多种器官的基本结构,其形态发生涉及到细胞变形、生化信号转导,以及细胞之间和细胞与细胞外基质之间的相互作用.目前尚未完全清楚力学和生化信号之间的相互作用如何调节该形态学过程.本文构建了耦合生化信号通路的三... 详细信息

管状上皮组织是组成多种器官的基本结构,其形态发生涉及到细胞变形、生化信号转导,以及细胞之间和细胞与细胞外基质之间的相互作用.目前尚未完全清楚力学和生化信号之间的相互作用如何调节该形态学过程.本文构建了耦合生化信号通路的三维细胞顶点模型,用于探究管状组织的形态发生.数值计算结果表明管腔尺寸受到细胞和细胞外基质的力学性质的影响,且细胞的力学-化学耦合的变形可以激发斑点状和条带状的超细胞肌动球蛋白斑图,进而介导组织形成波浪形和竹节形的管腔结构,该过程会受到化学扩散强度的调节.本研究突显了力学-化学相互作用在生物组织形态动力学中的重要作用,并且提供了一个三维计算框架以深入理解生命系统中复杂的斑图形成过程.

关键词：化学相互作用细胞变形肌动球蛋白形态发生管状组织细胞外基质三维形态波浪形

Analysis and design for the comprehensive ballistic and blast resistance of polyurea-coated steel plate

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Defence Technology（防务技术） 2023年第1期19卷 35-51页

作者： Dongyang Chu Yigang Wang Shanglin Yang Zhijie Li Zhuo Zhuang Zhanli Liu Applied mechanics Laboratory Department of Engineering MechanicsSchool of Aerospace EngineeringTsinghua UniversityBeijing100084China

Fragments and blast waves generated by explosions pose a serious threat to protective structures.In this paper,the impact resistance of polyurea-coated steel plate under complex dynamic loading is analyzed and designed for improving comprehensive ballistic and blast resistance using the newly established computational evaluating model.Firstly,according to the thickness and placement effects of the coating on the impact resistance,the steel-core sandwich plates are designed,which are proved to own outstanding comprehensive ballistic and blast resistance.Besides,the distribution diagram of ballistic and blast resistance for different polyurea-coated steel plates is given to guide the design of protective structures applying in different explosion scenarios.Furthermore,the dynamic response of designed plates under two scenarios with combined fragments and blast loading is studied.The results show that the synergistic effect of the combined loading reduces both the ballistic and blast resistance of the polyurea-coated steel plate.Besides,the acting sequence of the fragments and blast affects the structural protective performance heavily.It is found that the first loading inducing structural large deformation or damage is dominant.When fragments impact first,the excellent unit-thickness ballistic performance of the structural front part is strongly needed for improving the comprehensive ballistic and blast resistance.

关键词： Polyurea Ballistic and blast resistance Combined fragments and blast loading

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手性失配细长丝的拉伸行为

Acta Mechanica Sinica 2022年第11期38卷 115-127页

作者：张迎宾赵辉川于红军秦庆华王建山 Department of Mechanics Tianjin UniversityTianjin300054China department of Astronautic Science and mechanics Harbin Institute of TechnologyHarbin150001China

手性细长丝在人工和生物材料中普遍存在.由于具有手性微结构,手性丝通常表现出优异的弹性和拉伸-扭转耦合变形等性能.然而,手性微结构如何影响细长丝的弹性行为尚不清楚.本文提出了一种考虑手性微结构和手性失配的精细弹性细杆模型.基... 详细信息

手性细长丝在人工和生物材料中普遍存在.由于具有手性微结构,手性丝通常表现出优异的弹性和拉伸-扭转耦合变形等性能.然而,手性微结构如何影响细长丝的弹性行为尚不清楚.本文提出了一种考虑手性微结构和手性失配的精细弹性细杆模型.基于此模型,研究了单股螺旋和双股螺旋等手性丝组装结构在拉伸过程中的力-位移关系和结构手性变化.结果表明,手性失配会导致明显的弯曲-扭转耦合变形,使杆在拉伸时柔性更大.手性长丝在拉伸时还表现出类似DNA的反常扭转行为,可用结构手性的非线性变化来解释.该研究表明手性失配可用于调控手性丝的性能,有助于柔性执行器和软机器等柔性器件的设计.

关键词：弹性细杆失配拉伸行为非线性变化位移关系柔性器件拉伸过程组装结构