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    VIRTUAL PARTICLE TIME DERIVATIVE AND LOCAL VARIATIONAL——BASIC CONCEPTS IN TENSOR VARIATIONAL THEORY 1)
    YIN Yajun
    Mechanics in Engineering    2020, 42 (6): 681-688.   DOI: 10.6052/1000-0879-20-390
    Abstract115)   HTML29)    PDF(pc) (585KB)(160)       Save

    In the tensor analysis, symmetry breakages exist in concepts——there is differential of tensor, but there is no variational of tensor; in theories——there is differential theory of tensor, but there is no variational theory of tensor. However, the symmetry breakages can be compensated, as shown in this paper. The developing history of the concept of the virtual particle time derivative will be reviewed, as well as the process of abstracting the concept of the local variational of tensor and the procedure of constructing the variational theory of tensor. The symmetry between the variational theory and the differential theory for tensor will thus be revealed.

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    RESEARCH PROGRESS OF FRACTURE TOUGHNESS TEST METHOD FOR LOW CONSTRAINT SPECIMENS 1)
    WU Xu, SHUAI Jian, XU Kui
    Mechanics in Engineering    2020, 42 (5): 535-542.   DOI: 10.6052/1000-0879-20-105
    Abstract127)   HTML40)    PDF(pc) (769KB)(117)       Save

    The fracture toughness test of low constraint specimens is of great significance for the safe operation of oil and gas pipelines. In this paper, the existing fracture toughness testing methods and the development process of low constraint specimens are reviewed, and the common fracture toughness characterization parameters such as crack tip opening displacement (CTOD) and J-integral are introduced. The key problems such as the stress intensity factor, the J-integral plasticity factor, the J-integral and CTOD conversion factor, the crack size measurement method, and the digital image correlation method, in the fracture toughness test, are analyzed, and the problems that need to be further studied are summarized, to provide a necessary basis for the development of fracture toughness test of low constraint specimens.

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    SUPERSONIC BIPLANE —— A POSSIBLE BOOMLESS CONFIGURATION
    LIU Rongjian, BAI Peng
    Mechanics in Engineering    2020, 42 (4): 397-404.   DOI: 10.6052/1000-0879-19-482
    Abstract132)   HTML10)    PDF(pc) (14106KB)(102)       Save

    The concept of the supersonic biplane was proposed by Adolf Busemann, a German aerodynamist, in 1935. In recent years, the supersonic biplane has re-attracted the aeronautical scientist's interest in order to meet the needs of supersonic transport's low sonic boom and low supersonic cruise drag. In this paper, the working mechanism of the typical supersonic biplane is summarized. The basic problems faced by the application of the supersonic biplane, such as non-design point characteristics and three-dimensional problems, are introduced. Finally, the key problems and the application prospects of the supersonic biplane in the future are prospected.

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    A REVIEW ON THE APPLICATIONS OF DEEP LEARNING IN AIRCRAFT DYNAMICS AND CONTROL
    CHENG Lin, JIANG Fanghua, LI Junfeng
    Mechanics in Engineering    2020, 42 (3): 267-276.   DOI: 10.6052/1000-0879-20-077
    Abstract559)   HTML40)    PDF(pc) (406KB)(443)       Save

    The aircraft dynamics and control has achieved a significant progress, but also faces a series of problems that need to be dealt with. Deep learning provides a new solution for these problems, and it is good in many aspects, such as the working model of the experience storage, the intelligent accumulation and the off-line training. In this study, around the subject of the autonomy and the intelligence enhancement for the flight control, the applications of the deep learning in aircraft dynamics and control are reviewed in three aspects: (1) applications of deep learning in dynamic modeling to improve the computational efficiency and accuracy of modeling, or to solve the problem of inverse dynamics; (2) applications of deep learning in optimal control to improve the speed of trajectory planning or the real-time performance and autonomy of flight control; (3) applications of deep learning in mission design to improve optimization speed and decision-making intelligence. Furthermore, the advantages and the disadvantages are analyzed and representative papers are introduced. Finally, four suggestions to apply the deep learning in aircraft dynamics and control are given.

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    A QUASI-STATIC EQUIVALENT MECHANICAL MODEL FOR ROLL STABILITY OF PARTIALLY-FILLED TANKER TRUCKS
    HE Lieyun, LIU Qiang
    Mechanics in Engineering    2020, 42 (3): 294-299.   DOI: 10.6052/1000-0879-19-320
    Abstract158)      PDF(pc) (375KB)(110)       Save
    When a partially-filled tanker truck is turning, the center of gravity of the liquid shifts, which negatively influences the roll stability of the tanker truck. An elliptical-shaped tanker truck with partially-filled liquid is taken as an example and its rollover mechanism in the course of turning is analyzed. With the liquid level change being approximately represented by a quasi-static process, the pressure on the internal wall of the tank is calculated to locate the pressure center and a quasi-static equivalent mechanical model for the roll stability of partially-filled tanker trucks under turning conditions is established. This model provides a theoretical basis for developing the rollover-warning system of tanker trucks. It is shown that the roll stability of the tank car is related to the cross-sectional shape of the tank body and the filling rate of the liquid, and the results can be used for improving the roll stability of the tank car.
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    ANALYSIS OF ACCUMULATION CHARACTERISTICS OF ELASTIC DEFORMATION ENERGY OF SURROUNDING ROCK IN RECTANGULAR ROADWAY 1)
    YANG Dan, LIU Yang
    Mechanics in Engineering    2020, 42 (3): 300-305.   DOI: 10.6052/1000-0879-19-367
    Abstract122)      PDF(pc) (375KB)(84)       Save
    The coal mine impact ground pressure mainly occurs in the roadway. One of the main reasons is that a large amount of elastic energy is accumulated in the surrounding rock of the roadway. In order to obtain the characteristics of the elastic deformation energy accumulation of the surrounding rock of the rectangular roadway and to reduce the cost of the roadway support, the energy criterion of the roadway impact failure is established, and the calculation model of the surrounding rock energy accumulation of the rectangular roadway is built. The influence of the mining depth, the section size of the roadway and the thickness of the coal seam on the energy accumulation of the surrounding rock in the rectangular roadway is analyzed. It is concluded that for the rectangular roadway, the elastic energy increases with the increase of the depth of mining; the deeper the depth of the mining, the faster the growth rate of the elastic energy accumulated in the roadway; the energy accumulated in the surrounding rock of the roadway increases with the increase of the section size of the roadway; and when the thickness of the coal seam is less than the influence range of the roadway, the accumulation energy of the roadway increases as the thickness of the coal seam increases. In the actual project, the section size of the roadway should be reduced as much as possible, and the roadway is better arranged along the top and the bottom as far as possible. The research results provide a theoretical basis for the layout of the rockburst roadways and the reduction of the roadway support costs.
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    A CONSOLIDATION MODEL OF GROUP WELLS ON COMPOSITE FOUNDATION 1)
    ZHANG Yuguo, YANG Hanyue, DUAN Mengmeng, SHI Xiaojie, ZHANG Weijie
    Mechanics in Engineering    2020, 42 (3): 306-313.   DOI: 10.6052/1000-0879-19-461
    Abstract100)      PDF(pc) (524KB)(70)       Save
    For the consolidation problem on the composite foundation, with consideration of the influence of the well resistance and the vertical seepage in the soil radial direction, a calculation model of composite foundation group wells with pile-soil-pile as a unit is established. By using the analytical method, the analytical solution of the composite foundation group well consolidation under an instantaneous load is derived, as well as the consolidation characteristics and the pore pressure variation of the composite foundation. The study shows that the consolidation model of the composite foundation group wells provides a new idea for the theoretical study of the consolidation of the composite foundation. When the borehole diameter ratio is greater than 5, based on the assumption that the flow rates in the central pile and the side pile are equal, the difference between the consolidation degree calculated by the group well consolidation theory of the composite foundation and that calculated by the traditional consolidation theory is very small and negligible. The consolidation rate of the composite foundation increases with the increase of the pile permeability coefficient, the radial permeability coefficient of the soil in the disturbed zone and the vertical permeability coefficient of the soil. The larger the load is, the larger the settlement and the vertical strain will be. The pore pressure dissipation rate and the vertical strain rate of the surface soil are higher than those of the underneath soil.
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    ANALYSIS OF MECHANICAL PROPERTIES OF CEMENT CLINKER UNDER DIFFERENT TEMPERATURES BASED ON HERTZIAN INDENTATION METHOD 1)
    WANG Xiufang, BAO Yiwang, LIU Xiaogen, QIU Yan
    Mechanics in Engineering    2020, 42 (3): 314-320.   DOI: 10.6052/1000-0879-19-399
    Abstract122)      PDF(pc) (4855KB)(74)       Save
    In this paper, the relationship between stress and strain on the surface of brittle or quasi brittle materials is obtained by the high temperature Hertzian indentation method. According to the analysis of the indentation stress strain curve, the indentation modulus, the shear modulus and the hardness of the material can be determined and the deformation properties of the cement clinker are compared. Under the high temperature heat treatment of different temperatures (25 ${^\circ}\!$C$\sim $1400 ${^\circ}\!$C), the stress relaxation of the Hertzian indentation is observed. When the load peak value is 100 N, the load relaxation of the cement clinker is more obvious with the increase of the temperature. With the temperature increasing from 500 ${^\circ}\!$C to 1400 ${^\circ}\!$C, the load relaxation is very significant, especially at 1200 ${^\circ}\!$C. For the cement clinker samples within the C3S decomposition and the partial liquid phase, the stress relaxation is observed, most obviously at 1275 ${^\circ}\!$C, the clinker softened, and the relaxation load is 0 N. So 1275 ${^\circ}\!$C is the brittle ductile transition temperature of the clinker. The brittle plastic transition temperature of the cement clinker during the two heating processes can be determined by the high temperature Hertzian indentation relaxation test for the cement clinker. The temperature range for the sharp change of the elastic modulus and the compressive strength of the clinker can be determined. To study the mechanical behavior and the mechanical properties of the cement clinker at different temperatures, new ways to improve the grinding efficiency should be explored.
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    ANALYSIS OF GROUNDING CHARACTERISTICS AND STRAIN ENERGY OF RADIAL TIRES WITH RADIAL STIFFNESS 1)
    WANG Ningning, ZHOU Shuiting, SUN Pengfei
    Mechanics in Engineering    2020, 42 (3): 321-330.   DOI: 10.6052/1000-0879-19-459
    Abstract124)      PDF(pc) (4476KB)(86)       Save
    A general tire testing machine is used for the performance tests of the radial tires with radial stiffness. Orthogonal tests are used to analyze the grounding characteristics of the tires under different tire pressures and vertical loads. The simulation software ABAQUS is used for a simulation to compare with the tests. The results show that the Mooney-Rivli model for the rubber material can be applied in certain cases. The radial stiffness is linearly related with the tire pressure. As the area increases, the area of the tread marks decreases significantly. The pressure on the contact surface is mainly concentrated on the shoulders and that on the tread crown is also increased. When the tire pressure is constant and the vertical load is increased gradually, the stress on the entire footprint is in a symmetrical. distribution, and the distribution of the stress on the imprint surface changes gradually from high on the inner part and low on the outer part to high on the outer part and low on the inner part. A mathematical model is built and the finite element software is used to analyze the strain energy of the tire at the same time. It is found that the tire is prone to a slight lateral displacement and deformation at the same time when the tire is loaded at a low tire pressure of 150KPa. At this time, it is easy to cause a hysteresis loss and cause a sharp increase in the strain energy.
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    NUMERICAL ANALYSIS OF ARC MOTION IN RAILGUN MUZZLE UNDER THE EFFECT OF BACKFLOW
    GAO Yuan, WANG Zhaoxin, XIAO Hongcheng, NI Yanjie, XU Yingtao, LI Baoming
    Mechanics in Engineering    2020, 42 (3): 331-336.   DOI: 10.6052/1000-0879-19-378
    Abstract141)      PDF(pc) (771KB)(76)       Save
    During the launching process of the railgun, the high temperature air mass outside the muzzle moves to the interior at a speed far higher than the sound speed, which will change the arc shape of the muzzle and cause the arc displacement. This paper makes a numerical calculation of the movement process of the muzzle arc, based on the theory of magneto hydro dynamical (MHD), with a treatment method of potential boundary condition closely related to the electric conductivity of the arc plasma itself, and a three dimensional simulation model of the muzzle position arc is established. The arc motion under the backflow effect is analyzed, and the influence of the arc on the temperature distribution of the railgun inner bore flow field is studied. The simulation results show that the movement of the muzzle arc intensifies the temperature rise in the bore.
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    A MECHANICAL MODEL OF CELL DURING INDENTATION BASED ON MEMBRANE THEORY
    WANG Yue, XU Xianzhong, LIU Ming, LIU Mengyun
    Mechanics in Engineering    2020, 42 (3): 337-343.   DOI: 10.6052/1000-0879-19-479
    Abstract143)      PDF(pc) (19927KB)(77)       Save
    This paper proposes a mechanical model that can be used to analyze the deformation of the cell during indentation experiments based on the membrane theory. The mechanical model of the cell is validated through the macro-indentation tests on latex balls and PVC balls, the theoretical analysis and the comparison of the indentation testing curves of the different cells. At the same time, a specific mechanical analysis of the single chondrocytes is carried out by using the new model, and the mechanical parameters of the cell and the stress distribution on the surface of the cell membrane are obtained. A new idea is thus provided for the study of the mechanical properties of single cells.
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    A REVIEW OF STUDIES OF MECHANICAL PROPERTIES OF TURTLE CARAPACE 1)
    JIN Hongbo, ZHANG Zhiqiang, SONG Liang
    Mechanics in Engineering    2020, 42 (2): 143-150.   DOI: 10.6052/1000-0879-20-010
    Abstract328)   HTML35)    PDF(pc) (3870KB)(205)       Save

    After the evolution of hundreds of millions of years, most turtles have developed excellent shells with high specific stiffness and toughness. Obviously, the multi-scale structural characteristics and the biological material mechanical behavior of these turtle shells can be used for promoting the bio-inspired design of safety protection structures. This paper reviews the research progress of the turtle shell relevant to its protective functions, including the macro and micro features of the carapace and the corresponding mechanical properties. In addition, some carapace-inspired designs that could be adopted in protection structures are summarized. Finally, the existing problems and the focus of the future research are discussed, to provide some food for thought in the bio-inspired design of safety protection systems in future.

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    THE MEAN MOTION RESONANCE OF THE KUIPER BELT OBJECTS
    LAN Lei, LI Junfeng
    Mechanics in Engineering    2019, 41 (6): 643-648.   DOI: 10.6052/1000-0879-19-167
    Abstract188)   HTML13)    PDF(pc) (793KB)(259)       Save

    The movements of the asteroids in the Kuiper belt are important for us to understand the origin and the evolution of the solar system. Since the Kuiper belt objects (KBO) are a short distance to the Neptune of a great mass, the KBOs are significantly perturbed by Neptune's gravity. In this paper, we focus on two main families: the resonant and the scattered KBOs. The mean motion resonance can prevent the resonant KBOs from a close encounter with the Neptune. Thus most resonant KBOs are stable on their orbits. Here we mainly investigate the resonance width and strength of different resonant ratios with a high eccentricity. As for the scattered KBOs, their evolution is affected jointly by the resonance sticking and the resonance scattering. Here we are mainly concerned with the problem why there are a high number of KBOs in the scattered disc.

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    REVIEW ON OPTIMIZATION OF ASTEROID CAPTURE ORBITS
    BAOYIN Hexi, BAO Changchun
    Mechanics in Engineering    2019, 41 (5): 511-519.   DOI: 10.6052/1000-0879-19-106
    Abstract266)   HTML30)    PDF(pc) (283KB)(307)       Save

    The asteroid is of great significance for studying the formation of planets, the origin of life on the Earth, the defense against the collision of asteroids to the Earth and the mining on asteroids. Due to the insufficient capacity of the existing propulsion technology, the velocity increment needed to optimize the asteroid capture is the key for a successful capture mission. This paper reviews the capture orbit optimization method for asteroid and the extended capture period with the impulse thrust and lowthrust propulsions, including the strategy to capture asteroids by the gravity assisted and resonant orbital techniques, the continuous low thrust and temporary asteroid capture, and the scheme of extending the capture period.

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    APPLICATIONS AND CHALLENGES OF STRUCTURAL OPTIMIZATION IN HIGH-SPEED AEROCRAFT 1)
    QUAN Dongliang, SHI Guanghui, GUAN Chengqi, WANG Jian1, LUO Junhang, SONG Feng, WANG Bo, GAO Tong, ZHU Jihong, ZHANG Weihong
    Mechanics in Engineering    2019, 41 (4): 373-381.   DOI: 10.6052/1000-0879-18-448
    Abstract481)   HTML18)    PDF(pc) (2880KB)(329)       Save

    With its great national strategic importance and socio-economic benefits, the high-speed vehicle always plays a specific role in the field of aerospace. In this paper, the structural optimization technique and its application in the aircraft design are reviewed firstly. Then, the specific applications of structural optimization techniques in the high-speed vehicle design are then discussed in the context of the typical service environment and the design requirement. We show typical cases subsequently with applications in the concept design of the high-speed vehicle and in the innovative and improved design of their parts over the last years. In view of the solid theoretical foundations as well as the numerous successful engineering practices of the structural optimization, it not only provides an effective tool, but also brings about revolutionary changes for the design of high-speed vehicle structures. It is anticipated that the structural optimization supplemented by the empirical design will surely be a standard procedure for the aircraft design, and the practice-oriented research will undoubtedly enhance the core competitiveness of the aerospace industry in China

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    THE COVARAINT DERIVATIVES OF NATURAL BASE VECTORS AND THE ADVANCES IN GENERALIZED COVARAIBILITIES 1)
    YIN Yajun
    Mechanics in Engineering    2019, 41 (3): 255-264.   DOI: 10.6052/1000-0879-18-226
    Abstract609)   HTML41)    PDF(pc) (2779KB)(579)       Save

    This is the question asked in class: is it possible to obtain the covariant derivative of natural base vectors? To answer this question, the idea of axiomazitaion is introduced, the concepts of the generalized component and the generalized covariant derivative are defined. Based on these new concepts, the classical covariance is developed into the generalized covariance, and the classical covariant differentiation is developed into the generalized covariant differentiation. This paper summarizes the main difficulties and the important points of the above explorations, and shows the abstractions of the generalized covariant derivatives and the advances of the generalized covaraibilities.

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    DYNAMICS AND CONTROL OF SPACECRAFT FORMATION FLYING IN EARTH ORBIT 1)
    SUN Jun, HUANG Jing, ZHANG Xianliang, HUANG Tingxuan
    Mechanics in Engineering    2019, 41 (2): 117-136.   DOI: 10.6052/1000-0879-18-409
    Abstract335)      PDF(pc) (520KB)(238)       Save
    The spacecraft formation flying is defined as the tracking or the maintenance of a desired relative separation, orientation or position between or among several spacecraft. This paper reviews the dynamics and the control of the spacecraft formation flying in Earth orbit, including the modelling methods and the control design techniques of the conventional propulsion system and the novel propellant-less system. The conventional propulsion system, where the spacecraft is actuated by thrusters using chemical fuels or plasma, can achieve a high accuracy and variable formation constellations with a relatively large power consumption. By contrast, the novel propellant-less system, where the spacecraft is actuated by novel means of actuation such as the atmospheric drag effect, the non-contacting internal forces, the geomagnetic Lorentz force, the momentum exchange, would greatly extend the lifetime of the formation and effectively avoid the plume contamination with new control characteristics. This paper summarizes the research methods and achievements in the dynamics and the control of these fields, and puts forward some issues worthy of further study in related fields and the direction of future development.
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    RESEARCH PROGRESS OF LOCKED-IN STRESS IN ROCKS 1)
    GENG Hansheng, XU Hongfa, CHEN Xiao, BAI Zhun
    Mechanics in Engineering    2018, 40 (6): 613-624.   DOI: 10.6052/1000-0879-18-195
    Abstract438)      PDF(pc) (1949KB)(554)       Save

    The influence of the locked-in stress on the rock mechanical properties cannot be ignored. Since Chen Zongji proposed the definition of the locked-in stress in rocks, there were very few related studies. Starting from the definition, combined with the current development of the rock mechanics, this paper expands the concept of the locked-in stress,in a new definition of the locked-in stress in rocks. The forms of the stress in accordance with the new definition of the locked-in stress in the rock mechanics research are classified. The variation law of various kinds of locked-in stress and its empirical formula are summarized. The correlation between the locked-in stress and the excavation of the underground engineering and its influence are discussed. This paper provides a new way to explain the special phenomenon of deep rock mechanics.

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    PROGRESS IN STUDIES OF FLEXIBLE STRESS SENSITIVE CONDUCTIVE POLYMER COMPOSITES 1)
    LIU Hu, LIU Yongzhi, DAI Kun, GUO Zhanhu, LIU Chuntai
    Mechanics in Engineering    2018, 40 (5): 481-494.   DOI: 10.6052/1000-0879-18-250
    Abstract343)   HTML17)    PDF(pc) (47164KB)(307)       Save

    The flexible stress sensitive conductive polymer composites (CPCs) have a wide application prospect in the fields of the wearable human machine interaction, the medical monitoring, the portable sports equipment and the bionic robot, and others. The conductive percolation theory, the response mechanisms and the sensitivity of the stress sensitive CPCs are discussed in this paper. The response characteristics of different types of stress sensitive CPCs are reviewed, including the numerical predications. Finally, the future development is commented.

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    INTERFERENCE OF SHOCK AND BOUNDARY LAYER IN SUPERSONIC FLOW
    LIU Peiqing, GUO Zhifei
    Mechanics in Engineering    2018, 40 (4): 357-361.   DOI: 10.6052/1000-0879-17-363
    Abstract487)   HTML14)    PDF(pc) (12452KB)(390)       Save

    The compression boundary layer transition and separation caused by the interference of the shock and the boundary layer directly affect the drag, surface thermal protection and the flight performance of flying vehicles. This paper first reviews the past work on the interference between the shock wave and the boundary layer. And then, the effects of the forward shock, the oblique shock and the head shock on the laminar flow and the turbulent boundary layer of supersonic and transonic flows are studied and compared. The shock waves of different intensities have different effects on the boundary layer.A strong interference is more likely to cause the separation and the airfoil stall.

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    SOME FUNDAMENTAL CONCEPTS AND RESEARCH METHOD OF STRUCTURAL TOPOLOGY OPTIMIZATION
    ZHOU Kemin
    Mechanics in Engineering    2018, 40 (3): 245-252.   DOI: 10.6052/1000-0879-18-054
    Abstract521)   HTML21)    PDF(pc) (1757KB)(499)       Save

    Some fundamental concepts and problems in the research field of the structural topology optimization are introduced briefly. The essential characteristics of the truss-like and its discretization are analyzed. The classical analytical solutions as the benchmarks are listed in the references. The optimization strategies and the characteristics of various numerical methods for the structural topology optimization are reviewed. The numerical instabilities, such as the mesh-dependencies, the singular optima, the checkerboards and the local constraints, commonly in the structural topology optimization, are explained. The fundamental principles of the optimality criteria, the sequential programming and the heuristic methods are discussed.

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    DRAG REDUCTION TECHNIQUE FOR LARGE TRANSPORT AIRCRAFT
    LIU Peiqing, ZHANG Wen, GUO Hao
    Mechanics in Engineering    2018, 40 (2): 129-139.   DOI: 10.6052/1000-0879-17-295
    Abstract305)   HTML5)    PDF(pc) (19858KB)(456)       Save

    The techniques for the drag reduction of large transport aircraft are reviewed in this paper. The techniques intended to reduce the friction drag, the induced drag and the wave drag are reviewed specifically. Techniques like the suction control for delay boundary layer transition, the riblets for reducing turbulent friction drag, and the winglet are relatively mature for practical application. Distributed roughness, plasma actuators and the contour bump are most like to be used in the newly designed large transport aircraft. These newly developed techniques might be useful in further improving the drag characteristic of the next generation aircraft.

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    ADVANCE OF EXPERIMENTAL TECHNOLOGIES FOR STRUCTURAL MODAL TEST IN HIGH TEMPERATURE ENVIRONMENTS
    YU Kaiping, BAI Yunhe, ZHAO Rui, ZHOU Haotian
    Mechanics in Engineering    2018, 40 (1): 1-12.   DOI: 10.6052/1000-0879-17-288
    Abstract369)   HTML7)    PDF(pc) (28136KB)(1687)       Save

    Since the hypersonic vehicle is acted by a serious aerodynamic thermal load caused by the flight through the atmosphere, it is necessary to consider the effect of the high temperature in the ground test of the vehicle structures. But the structural modal experiment in a high temperature environment is far more complex than the normal modal experiment with many technical difficulties to be solved. In this paper, the advance of the thermal modal test technology is reviewed. The characteristics and the applicability of the excitation and measurement techniques to be used in the high temperature environment are discussed in detail. The development direction and the research focus of the structural modal test technology in the high temperature environment are suggested.

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    THERMAL VIBRATION OF TYPICAL NANO-STRUCTURE
    LIU Rumeng, WANG Lifeng
    Mechanics in Engineering    2017, 39 (2): 109-119.   DOI: 10.6052/1000-0879-16-429
    Abstract632)      PDF(pc) (13573KB)(1077)       Save

    The thermal vibration is the inherent vibration of nanostructures, which plays an important role in the dynamics of nanostructures. The quantum effects, the boundary effects and the van der Waals interaction have a significant influence on the thermal vibration of nanostructures. The carbon nanotubes and the graphene were extensively studied for their novel electronic properties and superior mechanical strength. This paper reviews some research methods for the thermal vibration of nanostructures, the thermal vibration of the carbon nanotube and the graphene in low temperatures and the nonlinear thermal vibration of the carbon nanotube.

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    OVERVIEW OF RING TEST TO ASSESS CRACKING RESISTANCE OF EARLY-AGE CONCRETE
    WANG Fulu, DONG Wei, YUAN Wenyan
    Mechanics in Engineering    2017, 39 (2): 120-129,151.   DOI: 10.6052/1000-0879-16-352
    Abstract405)      PDF(pc) (1237KB)(759)       Save

    The early-age concrete under the condition of restrained shrinkage is easy to crack, which would affect safety and durability of the structure, as well as the applicability. So it is very important to provide a simple and effective method to assess the crack resistance of the early-age concrete. In view of providing certain rigidity and the convenience of laboratory constraints, the restrained shrinkage ring test is widely used to evaluate the crack resistance of the concrete under restrained shrinkage conditions. This paper discusses the development of the restrained shrinkage ring test, the failure mechanism and the impact of three factors. The restrained shrinkage ring test is recommended as a standard test method by the American Association of State Highway and Transportation Officials (AASHTO) and the American Society for Testing and Materials (ASTM), and the test is conducted for different purposes, including the failure mechanism based on the maximum tensile stress fracture mechanics theory and the fracture energy to predict the concrete cracking. The annular test specimen geometry, the boundary conditions, the performance of the concrete materials and the pre-crack are considered as influencing factors. A test method of elliptical ring is adopted, which can effectively assess the crack resistance of the concrete under conditions of high degree of restraint.

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    TRANSFER ORBIT DEVIATION PROPAGATION ANALYSIS AND MID-COURSE CORRECTION FOR HUMAN LUNAR MISSION
    LI Haiyang, HE Boyong, CAO Pengfei
    Mechanics in Engineering    2017, 39 (1): 1-6.   DOI: 10.6052/1000-0879-16-291
    Abstract627)      PDF(pc) (1477KB)(656)       Save

    The transfer orbit for the human lunar mission means that between the trans-lunar orbit and the trans-earth orbit, and it has the characteristics of long flight time, complex dynamics model, and strong nonlinear and variable coe-cients. The controllability of the inevitable deviation afiects the result of the task execution, even the success or the failure of the engineering task directly. This paper reviews the studies of the transfer orbit of human lunar mission, the analysis method of the deviation propagation, the mid-course correction optimal strategy and the mid-course correction aiming algorithm. At last, some suggestions are made or the mid-course correction of the Chinese human lunar mission in the future.

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    A STATE-OF-THE-ART REVIEW OF FAILURE OF WOOD UNDER I/Ⅱ MIXED MODE FRACTURE
    ZHAO Yanhua, LI Zheng, CHANG Jianmei
    Mechanics in Engineering    2017, 39 (1): 7-17.   DOI: 10.6052/1000-0879-15-238
    Abstract411)      PDF(pc) (1707KB)(958)       Save

    For the design and the safety assessment of wood structures, an adequate knowledge of wood fracture behavior is important. Due to the complexity in its structure, wood is naturally anisotropic in the macroscopic scale, which makes it more di-cult to study wood failure based on fracture mechanics than to study isotropic materials. Therefore, only fractures of pure mode I and pure mode Ⅱ were given a considerable attention. Wood structural members are, however, often subject to the mixed mode fracture in reality, and the mixed mode fracture is now one of hot topics in the fracture studies. This paper gives a literature review on the wood mixed fracture from two aspects:the fracture criterion and the testing method. After an introduction of some empirical and physical models to predict the mixed mode fracture failure of wood, a comparison is made among these models using the test data in the literature. Various test methods are reviewed, with focus on fractures of mode I and mode Ⅱ combined. Some issues for future studies are highlighted.

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    PROGRESS IN STUDIES ON DISCRETE BOLTZMANN MODELING OF PHASE SEPARATION PROCESS
    XU Aiguo, ZHANG Guangcai, GAN Yanbiao
    Mechanics in Engineering    2016, 38 (4): 361-374.   DOI: 10.6052/1000-0879-16-006
    Abstract572)      PDF(pc) (33914KB)(446)       Save

    The studies on discrete Boltzmann modeling and simulation of phase separation are reviewed. According to the system component, the studies cover the single-component two-phase separation and the multi-component phase separation. According to the physical modeling, the studies cover the LBM (lattice Boltzmann method) simulations based on traditional hydrodynamic modeling and discrete kinetic modeling of the phase separation system. According to the main focus, the topic covers method/model studies and physical behavior investigations. The discrete kinetic modeling has brought some deeper insights into the phase separation process. The features of non-equilibriums obtained from discrete Boltzmann simulations can serve as some simple and effective physical criteria for dividing the two stages of phase separation, and can be used to discriminate and track various interfaces.

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    Cited: Baidu(17)
    THE ENERGY FINITE ELEMENT ANALYSIS FOR PREDICTION OF HIGH FREQUENCY DYNAMIC RESPONSE OF COMPOSITE MATERIAL STRUCTURES
    XIE Miaoxia, GUO Ruifeng, LI Lixia, ZHANG Linjie
    Mechanics in Engineering    2016, 38 (4): 375-381.   DOI: 10.6052/1000-0879-15-174
    Abstract439)      PDF(pc) (357KB)(715)       Save

    The prediction of high-frequency dynamic response of composite structures is one of key steps in the structural design of the aircraft and other vehicles. In order to make an accurate prediction, three methods are discussed. The energy finite element method is found to be suitable to obtain accurately the dynamic response of composite structures. In this paper, the energy finite element analysis and its applications for composite structures are reviewed. Some important issues for the further applications are suggested.

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    RESEARCH PROGRESS OF LIQUID SLOSHING IN MICROGRAVITY
    MIAO Nan, WANG Tianshu, LI Junfeng
    Mechanics in Engineering    2016, 38 (3): 229-236.   DOI: 10.6052/1000-0879-15-185
    Abstract497)      PDF(pc) (1379KB)(611)       Save

    Sloshing of liquid propellant in microgravity and its influence on the attitude control system have been studied for several decades. Accurate modeling is necessary, especially, for modern spacecrafts carrying large amounts of liquid propellant. Research progress on this issue is reviewed, including a summary of analytical methods for both linear and nonlinear sloshing, an introduction of numerical techniques such as modal analysis and CFD (computational fluid dynamics) methods, and also a description of experimental approaches and advances. Finally, some critical problems concerning liquid sloshing in microgravity are proposed and discussed.

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    Cited: Baidu(4)