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15 December 2014, Volume 36 Issue 6
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    2014, 36(6):  783-785.  doi:10.6052/1000-0879-13-502
    Abstract ( 8223 )   PDF (231KB) ( 2154 )  
    For teaching purposes, practical calculation formulas for principal stresses are proposed, which are obtained by directly solving the characteristic equation of the stress state with the theory of one-variable cubic equation.
    2014, 36(6):  742-746.  doi:10.6052/1000-0879-14-057
    Abstract ( 302 )   PDF (1607KB) ( 864 )  

    Experiments show that the drilling deformation of rock is partly in the deformation stage of steady-state creep when the temperature is below 500 ℃ and the hydrostatic stress is below 150 MPa. In this paper, the generalized Kelvin model is selected to reflect its characteristics. By using the Laplace transform and the inverse Laplace transform, the analytical solution of the drilling's radial displacement is obtained, and the relationship between the model parameters, the temperature and the stress are obtained by taking the temperature-stress coupling effect into consideration. After applying the relation to a fitting calculation, it is shown that the model is rational and reliable and can represent the creep deformation characteristics of the granite in steady state and be used to obtain the creep parameters of the granite under high temperature and high pressure. The results can be used in the drilling construction and maintenance, the drilling deformation prediction, and the drilling shaft lining stability analysis during the development of hot dry rock geothermal energy resources.

    Applied Research
    2014, 36(6):  774-778.  doi:10.6052/1000-0879-14-075
    Abstract ( 344 )   PDF (1119KB) ( 798 )  

    Based on the linear elastic plate theory, the rigidity of a concave template of a right angle trapezoid cross section made of homogeneous, continuous and isotropic material with a circular hole is calculated. At first, a mechanical and mathematical calculation model is built. Secondly, the third order variable coefficient differential equation expressed in deflection is obtained with boundary conditions. And then, the deflection is obtained, as well as the rigidity. Finally, an application example is given.

    Review
    PROGRESS IN MECHANICS OF THE COCHLEA
    MA Fuyin, WU Jiuhui
    2014, 36(6):  685-715.  doi:10.6052/1000-0879-13-477
    Abstract ( 601 )   PDF (8023KB) ( 1528 )  

    The mechanics of cochlea is the core of hearing sciences and physiological acoustics, as well as a representative biomechanics topic. The study of cochlear mechanical properties could promote the related studies of psychoacoustics. This paper reviews the mechanics of the cochlea in two parts, the macro and micro mechanics, focusing on the development trend of the cochlear mechanics and application prospects. It is suggested that the cochlea is a part of the inner ear and its mechanical response provides us with many aspects of our amazing sensitive and selective hearing, with an accurate frequency response from 20~20 000 Hz and with the stimulus signal being able to be amplified more than 4 000 times.

    STRUCTURE AND THERMODYNAMICS OF GRANULAR MATERIALS
    LIU Chuanqi, SUN Qicheng, WANG Guangqian
    2014, 36(6):  716-721.  doi:10.6052/1000-0879-14-123
    Abstract ( 502 )   PDF (2007KB) ( 2313 )  
    The granular materials are composed of a collection of discrete and solid particles, such as coarse sands and debris accumulation. Using data from experiments or based on engineering experiences, numerous models are developed to describe certain mechanical phenomena of granular materials. However, our under-standings of the mechanical properties of granular materials and their physical nature remain limited. The specific mechanical properties of granular materials come from complicated processes of the energy transporta-tion, the disordered structure in the long-range and the ordered structure in the short-range. In this paper, some developments in measuring the inherent structural characteristics, the thermodynamics, and the transformation between solid and fluid states of granular materials are discussed. A new research approach is proposed to unify the thermodynamics and the structural analysis to have a better understanding of granular materials.
    Applied Research
    NORMAL GRID RULE FOR HYPERSONIC HEAT FLUX NUMERICAL SIMULATION
    ZHANG Liang, CHENG Xiaoli, AI Bangcheng
    2014, 36(6):  722-727,741.  doi:10.6052/1000-0879-14-046
    Abstract ( 415 )   PDF (3774KB) ( 945 )  
    Numerical simulations for blunt models in hypersonic flows are carried out by solving the Reynolds averaged Navier-Stokes equation in this paper. The performances of the grid scale in the heat flux calculation are studied, and a criterion for the grid generation suitable for the heat flux calculation is proposed. It is shown that it is difficult to obtain reasonable results by using a grid either extremely fine or coarse for the heat flux calculation in practice. The grid scale adopted based on the local temperature gradient can achieve both enough space accuracy and satisfactory convergence velocity.
    2014, 36(6):  728-732.  doi:10.6052/1000-0879-14-151
    Abstract ( 328 )   PDF (1739KB) ( 952 )  
    The transverse vibration of microfluid-conveying microtubes embedded in elastic mediums under temperature environments is investigated. The governing equation of the transverse vibration of the tube is established based on the Hamilton's principle and the nonlinear thermoelastic theory, and then solved by using the complex mode method. The natural frequency and the critical flow velocity for buckling instability are obtained and the influences of the surrounding temperature and some major system parameters on the vibration characteristics are discussed. It is shown that the temperature variation, the micro-size effects of both tube and fluid, the outer diameter and the elastic medium rigidity have a significant influence on the natural frequency and the critical flow velocity of fluid-conveying microtubes.
    2014, 36(6):  733-737.  doi:10.6052/1000-0879-14-007
    Abstract ( 321 )   PDF (1336KB) ( 440 )  
    This paper studies the control of a dual-arm space robot system with bounded input torques to track a desired trajectory in the joint space, when the location of the base and the attitude are uncontrolled. Based on the Second Lagrange approach and the momentum conservation, a dynamics model of the dual-arm space robot system is built. Then, the saturated hyperbolic tangent function is adopted to design a new kind of control algorithms to control the driving torques of joints. Finally, the closed-loop error system is decomposed into a reduced-order model and a boundary-layer model based on the singular perturbation theory. The exponential stability of the state origin is proved by using the Lyapunov function. The numerical simulation results show the effectiveness and the superiority of the control algorithm.
    GENERAL METHOD FOR ANALYZING GEOMETRIC COMPONENTS OF A PLANE SYSTEM
    ZHANG Linnan, XU Chunhui, QIN Taiyan
    2014, 36(6):  738-741.  doi:10.6052/1000-0879-13-473
    Abstract ( 500 )   PDF (1156KB) ( 970 )  
    Analysis of geometric components for a plane system is one of the basic and difficult parts of structural mechanics. A general method for analyzing geometric components of a plane system is proposed based on the consideration of various types of problems. The method might help to understand related topics.
    INFLUENCE OF DISPLACEMENT OF SATURATED SAND STRATUM ON PRE-STRESSED ANCHORS
    LIU Bo, ZHANG Gong, LIU Qingnan, HUANG Mian, JIANG Yonghua, ZHOU Haoliang
    2014, 36(6):  747-752.  doi:10.6052/1000-0879-14-134
    Abstract ( 377 )   PDF (2884KB) ( 1026 )  
    Soil displacement is an important cause of stress fluctuation or invalidation of pre-stressed anchors. Using the load-displacement transfer function and based on the elastic theory, a force model of the pre-stressed anchor in saturated sand stratum is established, to study the variation law of stresses in the anchor in construc-tion processes and the mechanical characteristics of the anchor body with soil deformation for a real project. It is shown that the interface shear stiffness, the inclination angle and the anchor body diameter all have significant influences on the axial force in the anchor body and the interface shear stress.
    FRACTAL DESCRIPTION OF ROCK FRACTURE BEHAVIOR
    SUI Lili, YANG Yongming, JU Yang, LIU Haisheng, ZHANG Shoucheng, HAN Yuanliang
    2014, 36(6):  753-756,746.  doi:10.6052/1000-0879-14-025
    Abstract ( 447 )   PDF (948KB) ( 769 )  
    The quantitative evaluation of the rock fracture behavior is an important and complicated problem in the unconventional oil and gas resource exploitation. Based on the existing core experiment data, considering the lithology and the rock fracture fractal characteristics, a quantitative relationship between the fracture fractal dimension, the compressive strength and the surface density is established. The fractal dimensions of three fracturing cores are calculayed using the developed software, and it is shown that the more complex the fracture, the larger the fractal dimension. So the fractal dimension can be used as a factor to evaluate the fracture behavior. This method is simple, intuitive, and convenient for engineering applications.
    MODELING OF NONLINEAR BEHAVIORS OF IMMERSION JOINT
    XIAO Wenhao, CHAI Rui, YU Haitao, YUAN Yong
    2014, 36(6):  757-763.  doi:10.6052/1000-0879-14-033
    Abstract ( 464 )   PDF (4176KB) ( 1086 )  
    A criterion for seismic safety for immersed tunnels is important for their design. The nonlinear analyses of the materials and the contact are important for simulation of the nonlinear behaviors of joints using the finite element method. To simplify the calculation, an adjustment factor is introduced to modify the judgment condition in the contact algorithm, with consideration of the nonlinear contact between boundaries. The nonlinear behaviors of Gina gasket are also taken into account. By modeling, the axial stiffness, the flexural stiffness and the coupled shear stiffness of the immersion joint are obtained. A quasi-static analysis based on the numerical simulation is presented, in which different water pressures are considered due to the significant variations of the water depth, and the stiffness of the immersion joint under multi-level loads is also studied.
    2014, 36(6):  764-769.  doi:10.6052/1000-0879-14-071
    Abstract ( 343 )   PDF (3190KB) ( 1352 )  
    In order to study the influence of the chute on the particle size segregation during the discharging process of a bell-less top blast furnace, this paper uses the discrete element method (DEM) to simulate the discharging process, and obtain the velocity field of particles on the chute and the particle size distribution in both radial and circumferential directions. In addition, the influences of the key slots on the inner surface of the chute, the section area shape and the tilting angle of the chute on the particle size segregation are analyzed. It is shown that (1) the keyslots on the inner surface of the chute cause a circumferential particle size segregation; (2) a square section area is better than a circle one for it facilitates an accurate radial particle distribution; (3) the tilting angle of the chute influences the radial particle size segregation. This study provides a theoretical basis for the design of blast furnace discharging process and the control of the burden distribution.
    2014, 36(6):  770-773.  doi:10.6052/1000-0879-14-059
    Abstract ( 285 )   PDF (720KB) ( 689 )  
    This paper focuses on the bending analysis of functionally graded beams using a meshless global thin plate spline radial basis function collocation method. The shape parameter of the radial basis function plays an important role in the numerical accuracy. The determination of the shape parameter in the thin plate spline radial basis function is easier than that in other radial basis functions. The governing differential equations are derived based on the higher order shear deformation theory. The present results are compared with available published results which demonstrates the accuracy of the present method.
    2014, 36(6):  779-782,785.  doi:10.6052/1000-0879-14-195
    Abstract ( 333 )   PDF (442KB) ( 618 )  
    When the generalized coordinates are used to describe the motion of a system, a higher computational efficiency will be achieved in using the Gauss principle of least constraint, as compared with in the form of mass points. Based on the Gauss principle in the form of variation, the Gauss principle of least constraint in generalized coordinates is derived. The principle is generalized to cases of non-ideal constraints, unilateral constraints and the collision of rigid body systems. For the collision problem of rigid body systems, it is shown that the collision law cannot be replaced by the Gauss principle of least constraint and it should be used in the form of constraint equations for generalized velocities after collision.