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15 October 2018, Volume 40 Issue 5
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    Review
    PROGRESS IN STUDIES OF FLEXIBLE STRESS SENSITIVE CONDUCTIVE POLYMER COMPOSITES1)
    LIU Hu, LIU Yongzhi, DAI Kun, GUO Zhanhu, LIU Chuntai
    2018, 40(5):  481-494.  doi:10.6052/1000-0879-18-250
    Abstract ( 278 )   HTML( 275 )   PDF (47164KB) ( 275 )  

    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.

    Applied Research
    MOVING MODEL ANALYSIS OF THE INITIAL COMPRESSION WAVE IN TUNNEL FOR HIGH-SPEED TRAINS1)
    GUO Yi, SHAN Dongri, GUO Dilong, YANG Guowei, DU Jian
    2018, 40(5):  495-502.  doi:10.6052/1000-0879-18-120
    Abstract ( 352 )   PDF (13096KB) ( 278 )  

    The influence of the cross section on the initial compression wave is studied by using the moving model experiment in this paper. The results show that the initial compression wave variation is the combined result of the average cross-sectional area and the cross-sectional area distribution of a high-speed train streamlined nose when the train's max cross section and the streamlined nose length are the same. The average cross-sectional area affects the magnitude of the initial compression wave, and the cross-sectional area distribution affects the pressure gradient of the initial compression wave, therefore, affects the pressure dissipation of the initial compression wave propagating in the tunnel.

    DYNAMIC RESPONSE OF HIGH SPEED TRAIN MEETING IN OPEN AIR, MEETING IN TUNNEL AND PASSING TUNNEL1)
    ZHANG Min, WU Han, LAI Jiang, ZENG Xiaohui, SUN Zhenxu
    2018, 40(5):  503-509.  doi:10.6052/1000-0879-18-196
    Abstract ( 419 )   PDF (9316KB) ( 216 )  
    The pressure wave owing to meeting in open air, meeting in tunnel and passing tunnel will generate effect on dynamic response and operation safety of high speed train. A high speed model including three vehicles is presented. Aerodynamic loads are obtained by CFD simulation. Dynamic response and derailment coefficient under the three aerodynamic condition are obtained by Runga-$\!$-Kutta method. Comparison and analysis show that the trains mutually repulsing when meeting in the open air and mutually repulsing attracting when meeting in tunnel. The aerodynamic load owing to meeting in open air and passing tunnel has little effect on derailment coefficient. Nevertheless, the aerodynamic load owing to meeting in tunnel will clearly affect derailment coefficient and safety performance.
    2018, 40(5):  510-513.  doi:10.6052/1000-0879-17-430
    Abstract ( 246 )   PDF (846KB) ( 262 )  
    Based on the characteristic of mechanism mode in large deformation, this paper proposes a method for determining whether a geometrically unstable system of a single degree of freedom is constantly unstable or instantaneously unstable, and in the former case the paper further proposes a bi-element construction method to build the mechanism mode in large deformation. The method is nearly as simple as solving a quadratic equation without the need for solving transcendental equations and moreover the method can give complete solutions for modes, solution paths, limit points and bifurcation points. The method is found to be intuitive in theory, simple in formulation and complete in solutions. The method can be used as a supplement or extension to analysis of geometrical stability in structural mechanics course.
    STUDY OF THE PORE STRUCTURE OF SHALE BASED ON GAS ADSORPTION METHOD AND MERCURY INTRUSION METHOD1)
    LIU Pengzhi, GUO Hekun, SHEN Rui, LI Haibo, REN Huichen, ZHANG Chunqiu
    2018, 40(5):  514-519.  doi:10.6052/1000-0879-18-173
    Abstract ( 237 )   PDF (7483KB) ( 259 )  
    The Silurian Longmaxi Formation Shale is extensively developed in the Weiyuan and West Chongqing areas of the Sichuan Basin. The characteristics of the shale pore structure in the areas are quantitatively studied. With the shale samples in the Weiyuan and West Chongqing areas as examples, the characteristics of the pore structure and the pore size distribution of the reservoir are determined by using experimental techniques such as the carbon dioxide adsorption, the low-temperature nitrogen adsorption, and the high-pressure mercury injection. The results show that the development of micropores concerns mainly ones between 0.45 and 0.65 nm, the mesopores development concerns mainly ones between 2 and 5 nm, the macropores are relatively poorly developed and unevenly distributed, and the specific surface area is positively correlated with the micropores; the main pore type is the amorphous hole, such as an ink bottle hole with a wide neck, with a certain amount of parallel plate holes that are open to surrounding directions.
    2018, 40(5):  520-525.  doi:10.6052/1000-0879-18-115
    Abstract ( 233 )   PDF (11867KB) ( 203 )  
    The mode I fracture toughness is a main mechanical parameter of rocks, and it is influenced by many factors. The rock's mesoscopic bedding angle is one of the factors, which is not well studied in China. The three-point bending beam (CB) method is used for the metamorphic sandy slate rock obtained in the tunnel excavation, for the mode I rock fracture toughness and the compressional wave velocities of rocks, lateral, longitudinal and without mesoscopic bedding, respectively. It is shown that there is a close correlation between the $K_{\rm IC} $, the fracture damage deflection, the mesoscopic bedding, and the compressional wave velocity. Meanwhile, the concept of anisotropic coefficient Y based on the test results has been proposed, the $K'_{\rm IC}$ calculated by the anisotropic coefficient Y is in good agreement with the $K_{\rm IC} $ measured in the actual test.
    2018, 40(5):  526-532.  doi:10.6052/1000-0879-18-129
    Abstract ( 277 )   PDF (4245KB) ( 249 )  

    The influence of the surrounding rock weight on the rock stress around a shallow buried pipe can not be neglected. Based on the solution method proposed by Verruijt, with both the deadweight and the internal pressure considered, the surrounding rock stress in a semi-infinite region with a circular cavity is studied. The analytical solution of this problem by using complex functions, conformal mapping and Fourier transforms is obtained. The influence of the internal pressure and the radius and the ratio of the radius to the depth on the stress of the surrounding rock with consideration of the internal pressure and the deadweight is analyzed, which provides a theoretical basis for the pipeline design and the construction safety.

    2018, 40(5):  533-537.  doi:10.6052/1000-0879-18-099
    Abstract ( 403 )   PDF (1283KB) ( 267 )  
    Based on the considerations of reducing the safety hazard of wheel difference in trucks, this paper proposes an improvement direction of the inner wheel difference problem of semi-trailer based on the existing research results. Based on the principle of rigid body kinematics, it proposes a specific measure to derive the trajectory equation of semi-trailer movement during turning, and verified it theoretically using Matlab.
    2018, 40(5):  538-542.  doi:10.6052/1000-0879-18-097
    Abstract ( 351 )   PDF (5358KB) ( 320 )  
    This paper studies the tension and bending properties of the artificial trachea and the biologic trachea. According to the tensile test, a nonlinear constitutive model is established with a power function and based on a linear constitutive model of the artificial trachea obtained by fitting test data, with the maximum fitting error of 18.8%. According to the nonlinear bending theory, the large deformation bending deformation equation for the trachea is established, and the analytical solution is obtained. The maximum error between the theoretical bending load and the experimental result is 8.7%. Based on the explicit finite element method, a finite element simulation method is proposed for the bending deformation of the trachea. The error for the bending angle of the dog trachea between the finite element analysis result and the experimental result is 3%.