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Preface: mechanical perturbations induced quench: a challenge of superconductor mechanics

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National Science Review 2023年第3期10卷 7-8页

作者： xiaojing zheng Research Center for Applied Mechanics Xidian University

Superconducting materials have been gradually applied in many areas including energy,transportation,medical imaging and *** them,superconducting magnets that can generate a strong magnetic field above 10 Tesla with absolute advantages of higher quality,lower energy loss,and smaller volume,have become key to the performance improvement of cutting-edge science and large-scale engineering devices such as high-energy accelerators,thermonuclear fusion reactors,

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Probability of rebound and eject of sand particles in wind-blown sand movement

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Acta Mechanica Sinica 2007年第5期23卷 471-475页

作者： Li Xie xiaojing zheng Key Laboratory of Mechanics on Western Disaster and Environment Lanzhou University Lanzhou 730000 China

When incident particles impact into a sand bed in wind-blown sand movement, rebound of the incident particles and eject of the sand particles by the incident particles affect directly the development of wind sand flux. In order to obtain rebound and eject lift-off probability of the sand particles, we apply the particle-bed stochastic collision model presented in our pervious works to derive analytic solutions of velocities of the incident and impacted particles in the postcollision bed. In order to describe randomness inherent in the real particle-bed collision, we take the incident angle, the impact position and the direction of resultant action of sand particles in sand bed on the impacted sand particle as ran- dom variables, and calculate the rebound and eject velocities, angles and coefficients （ratio of rebound and eject velocity to incident velocity）. Numerical results are found in accordance with current experimental results. The rebound and eject liftoff probabilities versus the incident and creeping velocities are predicted.

关键词： Wind-blown sand movement Rebound andeject coefficient Rebound and eject lift-off probability

ELECTRIC FIELD EFFECTS ON YOUNG'S MOLULUS OF NANOWIRES

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Acta Mechanica Solida Sinica 2009年第6期22卷 511-523页

作者： xiaojing zheng Li Qiao Key Laboratory of Mechanics on Western Disaster and Environment Ministry of Education PRC Department of Mechanics and Engineering Science College of civil Engineering and Mechanics Lanzhou University Lanzhou Gansu 730000 China

As an important component of nanodevices and nanomachine constructions, the mechanical performance of nanowires （NWs） has been a subject of intense research efforts due to gaining relevance in controlling functionality of nanoelectromechanical systems （NEMS）; meanwhile, one of the characteristics of the NEMS is the dependence of the functionality of the systems upon the applied electric field. The study of the electric effects on the Young＇s modulus of nanostructures is of certain usefulness in the design of NEMS and the precise measurement of mechanical properties of one-dimensional nanostructures. This paper reviews the origin of the size-dependence of the elastic property of NWs and the factors influencing the discrepancies and inconsistencies in the measured values of the Young＇s modulus for the NW, besides the surface effects, nonlinear effects, the electromechanical coupling effects as a possible effect responsible for the differences in quantitative and qualitative performance of the measured Young＇s modulus for the NWs versus the diameter are clarified.

关键词： nanowires Young's modulus molecular dynamics simulations continuum mechanics theory electric effects

ANALYSES ON NONLINEAR COUPLING OF MAGNETO-THERMO-ELASTICITY OF FERROMAGNETIC THIN SHELL—II:FINITE ELEMENT MODELING AND APPLICATION

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Acta Mechanica Solida Sinica 2009年第3期22卷 197-205页

作者： Xingzhe Wang xiaojing zheng Key Laboratory of Mechanics on Western Disasters and Environment Ministry of Education of China College of Civil Engineering and Mechanics Lanzhou University Lanzhou 730000 China

Based on the generalized vaxiational principle of magneto-thermo-elasticity of a ferromagnetic thin shell established （see, Analyses on nonlinear coupling of magneto-thermo- elasticity of ferromagnetic thin shell--I）, the present paper developed a finite element modeling for the mechanical-magneto-thermal multi-field coupling of a ferromagnetic thin shell. The numerical modeling composes of finite element equations for three sub-systems of magnetic, thermal and deformation fields, as well as iterative methods for nonlinearities of the geometrical large-deflection and the multi-field coupling of the ferromagnetic shell. As examples, the numerical simulations on magneto-elastic behaviors of a ferromagnetic cylindrical shell in an applied magnetic field, and magneto-thermo-elastic behaviors of the shell in applied magnetic and thermal fields are carried out. The results are in good agreement with the experimental ones.

关键词： ferromagnetic thin shell magneto-thermo-elasticity nonlinear coupling finite element method

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HEAT TRANSFER CHARACTERISTICS OF CONDUCTIVE MATERIAL UNDER INNER NON-UNIFORM ELECTROMAGNETIC FIELDS

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Acta Mechanica Solida Sinica 2011年第2期24卷 117-124页

作者： Huijuan Bai xiaojing zheng Key Laboratory of Mechanics on Western Disaster and Environment Ministry of Education PRC Department of Mechanics and Engineering Science College of Civil Engineering and Mechanics Lanzhou University Lanzhou 730000 China

Electronic transport properties can be influenced by the applied electromagnetic fields in conductive materials. The change of the electron distribution function evoked by outfields obeys the Boltzmann equation. In this paper, a general law of heat conduction considering the non-uniform electromagnetic effect is developed from the Boltzmann equation. An analysis of the equation leads to the result that the electric field gradient and the magnetic gradient in the conductive material are responsible for the influences of electromagnetic fields on the heat conduction process. A physical model is established and finite element numerical simulation reveals that heat conduction can be increased or delayed by the different directions of the electric field gradient, and the existence of the magnetic gradient always hinders heat conduction.

关键词： heat conduction non-uniform electromagnetic field Boltzmann equation

EXPERIMENTAL RESEARCHES ON MAGNETO-THERMO-MECHANICAL CHARACTERIZATION OF TERFENOL-D

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Acta Mechanica Solida Sinica 2007年第4期20卷 283-288页

作者： Yirui Liang xiaojing zheng Department of Mechanics Lanzhou University Lanzhou 730000 China

The coupling effects of axial pre-stress, temperature and magnetic field on magne- tostrictive strain and magnetization as well as Young＇s modulus ofa Terfenol-D （***.93） rod are tested to give a good understanding of magneto-thermal-mecha- nical characteristics of giant magnetostrictive materials. Results show that magneto-thermo-mechanical coupling of giant magnetostrictive materials is very strong; and the influences of pre-stress and temperature on magnetostrictive strain and Young＇s modulus vary with the intensity of magnetic field.

关键词： gaint magnetostrictive material Young's modulus magneto-thermo-mechanicalcharacterization magnetostrictive strain magnetization

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Extreme mechanics

Theoretical & Applied Mechanics Letters 2020年第1期10卷 1-7页

作者： xiaojing zheng School of Mechano-Electronic Engineering Xidian UniversityXi'an 710071 China

With the development of cutting-edge sciences and new technologies,we have to consider the size,the density,the hardness,the stiffness and other properties of engineering materials and structures beyond the conventional ranges,as well as their mechanical behavior in extreme environments,such as ultra-conventional temperature,speed,physical and chemical fields,and severe weather,and more effective theories and methods of mechanics are *** paper first gives the fundamental definition and the scientific connotation of extreme mechanics,then reviews the studies of extreme mechanics from three aspects:the extreme properties,the extreme loads,and the discipline development,as well as major engineering and scientific *** characteristics of extreme mechanics and major challenges in the aspects of mechanical theory,computational methods and experimental techniques are *** developments of extreme mechanics are suggested.

关键词： Extreme mechanics Extreme properties Extreme loads Discipline development

Experimental analysis of sand particles' lift-off and incident velocities in wind-blown sand flux

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Acta Mechanica Sinica 2005年第6期21卷 564-573页

作者： Li Xie Zhibao Dong xiaojing zheng Key Laboratory of Mechanics on Western Disaster and Environment Ministry of EducationDepartment of Mechanics Lanzhou UniversityLanzhou Gansu 730000 China Laboratory of Blown Sand Physics and Desert Environments Cold and Arid Regions Environment and EngineeringResearch Institute Chinese Academy of SciencesLanzhou Gansu 730000 China

The probability distributions of sand particles＇ lift-off and incident velocities in a wind-blown sand flux play very important roles in the simulation of the wind-blown sand movement. In this paper, the vertical and the horizontal speeds of sand particles located at 1.0 mm above a sand-bed in a wind-blown sand flux are observed with the aid of Phase Doppler Anemometry （PDA） in a wind tunnel. Based on the experimental data, the probability distributions of not only the vertical lift-off speed but also the lift-off velocity as well as its horizontal component and the incident velocity as well as its vertical and horizontal components can be obtained by the equal distance histogram method. It is found, according to the results of the X^2-test for these probability distributions, that the probability density functions （pdf＇s） of the sand particles＇ lift-off and incident velocities as well as their vertical com- ponents are described by the Gamma density function with different peak values and shapes and the downwind incident and lift-off horizontal speeds, respectively, can be described by the lognormal and the Gamma density functions, These pdf＇s depend on not only the sand particle diameter but also the wind speed.

关键词： Wind-blown sand movement - Tunnel experiment- Incident velocity. Lift-off velocity Probability density

Characteristics of near-surface turbulence during a dust storm passing Minqin on March 19,2010

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Chinese Science Bulletin 2010年第27期55卷 3107-3112页

作者： zheng xiaojing ZHANG JingHong Key Laboratory of Mechanics on Western Disaster and Environment School of Civil Engineering and Mechanics Lanzhou University Lanzhou730000 China

Twelve-hour real-time and synchronous measurements of the three-dimensional components of the near-surface turbulence at four heights(8,16,32 and 47 m)during a dust storm are obtained by sonic anemometers for the first *** experimental results show that(1)the mean vertical velocities at all four heights have considerably positive values during the dust storm,illustrating a strong upward flow near the surface;(2)during the dust storm,the mean vertical velocity is higher at 8 m than at 16 and 32 m,implying that the convection is stronger at 8 m than at the other two heights;and(3)when the longitudinal velocity is a maximum,the mean of the vertical components of wind velocities at 8 m is a minimum and the standard deviation is a maximum,which reveals weaker vertical convection during the period of greatest dust storm intensity,while the turbulence intensity contrarily increases,which may result in more entrainment of surface *** analysis results also show that the standard deviations of the longitudinal and vertical velocities increase as the mean inflow velocity increases,but the standard deviation of the lateral velocity is hardly affected by the mean inflow *** on the calculated skewness and kurtosis of the longitudinal,vertical and lateral velocities every 20 min at different heights,it is seen that all three components obviously fluctuate with height,which further indicates the importance of performing real-time and synchronous measurements at different heights near the surface during a dust storm so as to reveal the three-dimensional turbulence structure accurately.

关键词：湍流特性近地表垂直速度风暴民勤传递尘埃同步测量