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10 August 2006, Volume 28 Issue 4
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    Education Study
    2006, 28(4):  0-0.  doi:10.6052/1000-0879-2005-134
    Abstract ( 1013 )   PDF (958KB) ( 520 )  
    This paper gives a 3D-entity model of the main part of the underwater vehicle by use of Pro/E software. Based on the 3D Navier-Stokes equations for viscous steady imcompressible flow and two-equation $\kappa$-$\varepsilon$ turbulent model, the flow field and hydrodynamic load of underwater vehicle during empennage-expanding is numerically simulated with the finite volume method. The empennage-expanding is analyzed by the use of the simulation results. Comparing with the experimental results, the numerical analysis method is justified, which may be useful for analyzing engineering problems.
    2006, 28(4):  0-0.  doi:10.6052/1000-0992-2005-222
    Abstract ( 1014 )   PDF (738KB) ( 467 )  
    In the present paper, based on the experimental data, the lateral dispersion coefficients of five kinds of solid waste particles are calculated in the ICFB and the bubbling bed. The results indicate that the following factors influence dispersion coefficients: the distortion extent, the density and the size of the particles; the shape of the air distributor and the mode of air distribution. The movements of light particles follow the law of diffusion; on the other hand, the movements of heavy particles do not. The particles' lateral dispersion characteristics are described and explained briefly by the interaction of gas-particle flows and waste particles with various matter properties.
    2006, 28(4):  0-0.  doi:10.6052/1000-0992-2005-225
    Abstract ( 1375 )   PDF (1156KB) ( 653 )  
    With the test model of bionic underwater vehicle based on undulatory propulsion of long flexible fin as the background, the paper studies the undulatory propulsion dynamics of the long flexible fin of Gymnarchus Niloticus. Assuming that the fin bone vibrates according to a sine law, this paper establishes the mathematical model of undulatory curved surface of the long flexible fin. Then using the resistive theory and a modified hypothesis about fluid, the propulsion force generated by undulation of the long flexible fin is analyzed, and the dynamic model is obtained. Finally, with the aid of numerical simulation, the paper obtains the formula for hydrodynamic force and moment of the bionic long flexible fin of the test model caused by the fin undulatory movement. This formula provides a theoretical basis for dynamic analysis and control system design of bionic underwater vehicle.
    2006, 28(4):  0-0.  doi:10.6052/1000-0992-2005-239
    Abstract ( 2765 )   PDF (903KB) ( 908 )  
    In recent years, elastic-viscoelastic composite structures are widely utilized in vibration reduction of engineering structure. But existing FE software packages are not designed to deal with the frequency-dependent mechanical properties of viscoelastic materials. Therefore, in this work new integral finite elements are developed and integrate into the ANSYS element bank, and an iteration algorithm is hooked up to the ANSYS. It is shown that this strategy is pragmatical and convenient. The model updating of the integral finite element based on the experimental modal parameters is also carried out.
    2006, 28(4):  0-0.  doi:10.6052/1000-0992-2005-253
    Abstract ( 1114 )   PDF (598KB) ( 523 )  
    In this paper, the principle of the least action with mixed variables is used for forced vibrations of the rectangular bending plates with two adjacent sides clamped and the others free under the action of a uniform load, and the steady solution is obtained. A comparison with results from literature shows the validity of the present method.
    2006, 28(4):  0-0.  doi:10.6052/1000-0992-2005-258
    Abstract ( 1208 )   PDF (1286KB) ( 888 )  
    Cement is an important kind of structural materials for civil and industrial engineering. The mechanical properties of the cement depend on its hydration process. The present article gives a critical review on evolution of the microstructures and properties in the hydration of cements. The emphasis is placed on the experimental, theoretical and numerical methods, including the simulation of the microstructure, analysis of mechanical properties as well as the relations between microstructure and properties. The research directions in the future are briefly discussed.
    2006, 28(4):  0-0.  doi:10.6052/1000-0992-2005-269
    Abstract ( 1131 )   PDF (1186KB) ( 882 )  
    An element splitting technique is introduced into the discontinuous finite element method which admits discontinuity between elements by using joint elements. The method can be applied to simulate the fracture of materials not only at the interfaces but also in the material mass based on a given criteria. The validation of this method is shown by comparing the numerical calculation with the 3-point bending experiment.
    2006, 28(4):  0-0.  doi:10.6052/1000-0992-2005-282
    Abstract ( 1275 )   PDF (721KB) ( 575 )  
    The governing equations for deflections of elastic thin-plates induced by non-uniform surface stresses together with the boundary conditions are presented. By a physical analogue, the solution of the problem is equivalent to that for deflections of elastic plate induced by thermal stresses. Utilizing this method, the phenomena of local bending observed in experiments can theoretically be explained.
    2006, 28(4):  0-0.  doi:10.6052/1000-0879-2005-297
    Abstract ( 1323 )   PDF (694KB) ( 824 )  
    The stiffness of microstructures is an important parameter for microsensor. This parameter is usually obtained by FEM approach, and it is difficult to obtain an analytical expression. In this paper, a kind of microaccelerometer with a complex microstructure is designed and its main-axial stiffness is obtained by force method and energy method. The theoretical results are compared with those of FEM approach with good agreement. This methodology is extended to the stiffness analysis of microaccelerometer with symmetric and statically indeterminate microstructures.
    2006, 28(4):  0-0.  doi:10.6052/1000-0992-2005-301
    Abstract ( 1511 )   PDF (397KB) ( 732 )  
    The steel truss without diagonals is applied widely in all kinds of public buildings. As a kind of small structure with high redundant number, a simple calculation method is hard to find for reasonable results. An approximate method to calculate this steel truss is found by use of the principle of structural mechanics and symmetries. Accurate analysis and calculation of examples indicate that the results of this method are reasonable and the method is also convenient for applications.
    2006, 28(4):  0-0.  doi:10.6052/1000-0879-2005-307
    Abstract ( 1225 )   PDF (702KB) ( 723 )  
    The commercial software ANSYS is used to analyze the stress and linear stability of the highest natural draft cooling tower with flue gas inlets integrated, which will be built in Zhejiang province. The phenomena of local instability around the hole is found and the critical wind speed decreases dramatically when the natural draft cooling tower is acted by a 72 degree wind load. This phenomena will disappear when the natural draft cooling tower is thickened around the hole.
    2006, 28(4):  0-0.  doi:10.6052/1000-0992-2005-339
    Abstract ( 1458 )   PDF (3324KB) ( 803 )  
    Digital image processing technique is introduced into Rock Failure Process Analysis code and a new micromechanical analysis method of rock failure is established. By extracting the information of microstructure of rock in meso-scale, image data are fed into RFPA analysis. This method enjoys the advantage of failure process analysis of RFPA 2D. Using a granite rock as an example, this paper illustrates the process of micromechanical analysis of rock failure. The results show that the digital image processing based RFPA 2D method is an effective method to study micromechanical behavior of rock in meso-scale.
    2006, 28(4):  0-0.  doi:10.6052/1000-0992-2005-428
    Abstract ( 1158 )   PDF (754KB) ( 685 )  
    Reticulated shells as structural members have found wide applications in large span structures. In this paper, the governing equations for nonlinear forced vibrations of a double deck reticulated shallow spherical shell structure is established. Then, the nonlinear dynamic buckling is considered for a double deck reticulated shallow spherical shell under immovable clamped boundary conditions. At the same time, the model of catastrophe of nonlinear vibration bucking for the double deck reticulated shallow spherical shell is built by using catastrophe theory. The critical equation about the model of catastrophe is obtained. Finally, the effects of shell parameters on the nonlinear vibration buckling are considered.
    2006, 28(4):  0-0.  doi:10.6052/1000-0992-2006-053
    Abstract ( 1117 )   PDF (690KB) ( 763 )  
    In this paper, Level Set method is introduced and adopted to capture moving interfaces of two concentric circles in constant velocity fields, these of circle and rectangle in shear velocity flow fields, and those of hemicycle and Zaleska in revolving velocity flow fields. First Level Set equation is treated with fifth-order WENO scheme and integral-averaging scheme, and then it is re-initialized and calculated again with modified Godunov method. By analyzing the results, the influence of discrete accuracy of time derivative and that of re-initialization of Level Set function on tracking effect are studied. It is shown that not only Level Set method can be used to exactly track interfaces and get a sharp geography, but also it can be easily programmed.
    2006, 28(4):  0-0.  doi:10.6052/1000-0992-2006-178
    Abstract ( 1614 )   PDF (1728KB) ( 1385 )  
    The fundamental concepts of micropolar fluid, couple stress fluid, fractional Maxwell fluid and smart fluid are described. The basic differences between these non-Newtonian fluids and Newtonian fluids are elaborated by simple examples. Advances in the fields of these non-Newtonian fluids are discussed.