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ATOMISTIC CALCULATIONS OF SURFACE ENERGY OF SPHERICAL COPPER SURFACES

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Acta Mechanica Solida Sinica 2012年第6期25卷 557-561页

作者： Jianjun Bian Gangfeng Wang Xiqiao Feng SVL Department of Engineering Mechanics Xi’an Jiaotong University department of engineering {2. Tsinghua University

Surface plays an important role in the physical and mechanical behavior of nanos- tructured materials and elements, however surface energy of curved solid surfaces has not been fully understood. In the present letter, surface energy of spherical particles and cavities in FCC copper is calculated by embedded atom method. The numerical simulations reveal that the dis- tribution of atom energy is non-uniform on the curved surfaces. However, when the radius of spherical cavity or particle is larger than 4 nm, the average surface energy density keeps almost constant irrespective of its location and radius.

关键词： surface energy nanoparticle nanocavity

Mechanical Properties and Deformation Mechanisms of Metallic Glasses Under Hydrostatic Pressure

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Acta Mechanica Solida Sinica 2023年第3期36卷 390-404页

作者： Haiming Lu Yao Tang Fanheng Jiang Panpan Wan Haofei Zhou Center for X-mechanics Department of Engineering MechanicsZhejiang UniversityHangzhou 310027China

Metallic glasses(MGs)are promising structural materials with high strength,large elastic strain limit and enhanced wear *** the way to tune the mechanical performance of MGs,numerous efforts have been devoted to investigating the effect of hydrostatic pressure(σh)on the mechanical properties and deformation mechanisms of *** application of sufficiently large magnitudes ofσh to MGs has been considered a feasible way to improve strength and delocalize plastic deformation in *** this paper,we review recent studies on pressure-dependent thermodynamic properties,mechanical strength and hardness,as well as elevated ductility of MGs due to the pressure-induced change of deformation and failure *** of intriguing mechanical behaviors of MGs,and the corresponding theoretical modeling and atomistic understanding of plastic deformation in MGs under pure hydrostatic pressure and more general stress states are *** findings not only deepen the understanding of pressure-dependent mechanical behaviors of MGs,but also point out the potential of tuning mechanical behaviors of MGs through stress engineering.

关键词： Metallic glass Hydrostatic pressure Mechanical property Deformation mechanism Microstructure

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 *** 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 ***,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 ***,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 ***,the dynamic response of designed plates under two scenarios with combined fragments and blast loading is *** results show that the synergistic effect of the combined loading reduces both the ballistic and blast resistance of the polyurea-coated steel ***,the acting sequence of the fragments and blast affects the structural protective performance *** is found that the first loading inducing structural large deformation or damage is *** 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

Unsteady transverse injection of kerosene into a supersonic flow

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Science China(Technological Sciences) 2000年第2期43卷 206-214页

作者：徐胜利 R.D.Archer B.E.Milton 岳朋涛 1. department of Modern mechanics University of Science and Technology of China 230026 Hefei China 2. The University of New South Wales 2052 Sydney Australia

A shadowgraph and a new fuel injection system were used to study kerosene transversely injected into a supersonic flow. High pressure and velocity of injection can be attained. The pressure time histories were detected in oil-line and the shadowgraphs of the flow field were obtained at different time-delays. The inflow stagnation pressure was varied to change the local flow speed in test section. The results indicate that kerosene jet exhibits deep penetration and four regimes appear clearly during the fuel jet atomization in a high-speed flow. The jet disintegration is caused by surface waves propagating along the jet surface, and the breakup point is located at the wave trough. The surface waves are dominantly generated by aerodynamic force. The jet shock is close to windward surface of the jet. The shock reflects on and transmits in duct boundary layers. In the case of unsteady injection, the shock structure is very complicated and different from that of hydrogen injection. The results of kerosene injected into a quiescent gas and a subsonic flow are also provided for comparison.

关键词： supersonic flow fuel injection atomization supersonic combustion.

Bond-associated non-ordinary state-based peridynamic model for multiple spalling simulation of concrete

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Acta Mechanica Sinica 2021年第7期37卷 1104-1135,I0002页

作者： Siyang Yang Xin Gu Qing Zhang Xiaozhou Xia department of engineering {2. College of Mechanics and MaterialsHohai UniversityNanjing 211100China

The non-ordinary state-based peridynamic(NOSB PD)model has the capability of incorporating existing constitutive relationships in the classical continuum *** the present work,we first develop an NOSB PD model corresponding to the Johnson–Holmquist II(JH-2.constitutive damage model,which can describe the severe damage of concrete under intense impact ***,the numerical oscillation problem of the NOSB PD caused by zero-energy mode is analyzed and hence a bond-associated non-ordinary state-based peridynamic(BA-NOSB PD)model is adopted to remove the ***,the elastic deformation of a three-dimensional bar is analyzed to verify the capability of BA-NOSB PD in eliminating the numerical ***,concrete spalling caused by the interaction of incident compression wave and reflected tension wave is *** dynamic tensile fracture process of concrete multiple spalling is accurately reproduced for several examples according to the spalling number and spalling thickness analysis,illustrating the approach can well simulate and analyze the concrete spalling discontinuities.

关键词： Non-ordinary state-based peridynamics Bond-associated horizon-Johnson-HolmquistⅡ(JH-2.model Wave propagation Multiple spalling

FIRST-PASSAGE FAILURE OF PREISACH HYSTERETIC SYSTEMS

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Acta Mechanica Solida Sinica 2014年第5期27卷 477-485页

作者： Ming Xu Xiaoling Jin Yong Wang Zhilong Huang Institute of Fluid mechanics China Jiliang University department of engineering {2. Zhejiang University

The first-passage failure of a single-degree-of-freedom hysteretic system with non- local memory is investigated. The hysteretic behavior is described through a Preisach model with excitation selected as Gaussian white noise. First, the equivalent nonlinear non-hysteretic sys- tem with amplitude-dependent damping and stiffness coefficients is derived through generalized harmonic balance technique. Then, equivalent damping and stiffness coefficients are expressed as functions of system energy by using the relation of amplitude to system energy. The stochastic aver- aging of energy envelope is adopted to accept the averaged It5 stochastic differential equation with respect to system energy. The establishing and solving of the associated backward Kolmogorov equation yields the reliability function and probability density of first-passage time. The effects of system parameters on first-passage failure are investigated concisely and validated through Monte Carlo simulation.

关键词： first-passage failure Preisach hysteretic systems stochastic averaging of energyenvelope generalized harmonic balance technique

Dynamics of a multiplex neural network with delayed couplings

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Applied Mathematics and mechanics(English Edition) 2021年第3期42卷 441-456页

作者： Xiaochen MAO Xingyong LI Weijie DING Song WANG Xiangyu ZHOU Lei QIAO department of engineering {2. College of Mechanics and MaterialsHohai UniversityNanjing 211100China

Multiplex networks have drawn much attention since they have been observed in many systems,e.g.,brain,transport,and social *** this paper,the nonlinear dynamics of a multiplex network with three neural groups and delayed interactions is *** stability and bifurcation of the network equilibrium are discussed,and interesting neural activities of the network are *** on the neuron circuit,transfer function circuit,and time delay circuit,a circuit platform of the network is *** is shown that delayed couplings play crucial roles in the network dynamics,e.g.,the enhancement and suppression of the stability,the patterns of the synchronization between networks,and the generation of complicated attractors and multi-stability coexistence.

关键词： neural network time delay synchronization coexisting attractor

Theoretical analysis of the velocity field, stress field and vortex sheet of generalized second order fluid with fractional anomalous diffusion

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Science China Mathematics 2001年第11期44卷 1387-1399页

作者：徐明瑜谭文长 1. Institute of Mathematics and Systematical Science Research Center for Biomedical Engineering Shandong University 250100 Jinan China 2. department of mechanics and {2. Science State Key Laboratory for Turbulence Research Peking University 100871 Beijing China

The velocity field of generalized second order fluid with fractional anomalous diiusion caused by a plate moving impulsively in its own plane is investigated and the anomalous diffusion problems of the stress field and vortex sheet caused by this process are studied. Many previous and classical results can be considered as particular cases of this paper, such as the solutions of the fractional diffusion equations obtained by Wyss; the classical Rayleigh’s time-space similarity solution; the relationship between stress field and velocity field obtained by Bagley and co-worker and Podlubny’s results on the fractional motion equation of a plate. In addition, a lot of significant results also are obtained. For example, the necessary condition for causing the vortex sheet is that the time fractional diffusion index β must be greater than that of generalized second order fluid α; the establiihment of the vorticity distribution function depends on the time history of the velocity profile at a given point, and the time history can be described by the fractional calculus.

关键词： generalized second order fluid fractional calculus anomalous diffusion stress field vortex sheet generalized Mittag-Leffler function

Theory on single molecule-photon cryocooler——Conception and quantum transition processes

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Science China Mathematics 2001年第1期44卷 113-119页

作者：秦伟平杜国同许武陈宝玖秦冠仕黄世华 1. Changchun Institute of Optical Fine Mechanics and Physics Chinese Academy of Sciences China 1. Laboratory of Excited State Processes Chinese Academy of Sciences 130021 Ghangchun China 2. Electronic engineering department Jilin University China 2. National Integrated Optoelectronics Laboratory Jilin University 130023 Changchun China

The micro mechanism of anti-Stokes fluorescent cooling was investigated on molecular or ionic scale. A new conception of single molecule-photon cryocooler (SMPC) was given, and the smallest cryocooler in the world was predicted. We described SMPC and its running principle in detail. The quantum transition processes of SMPC and the largest cooling coefficient that SMPC can get in an optical transition were given. Also we studied the random property of SMPC in cooling processes. The thermodynamic behavior of single Yb3+ ion as a photon cryocooler was imitated.

关键词： single molecule ion cryocooler laser cooling anti-Stokes fluorescent cooling.