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10 August 2003, Volume 25 Issue 4
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    Application study
    2003, 25(4):  0-0.  doi:10.6052/1000-0879-2002-245
    Abstract ( 1450 )   PDF (232KB) ( 1047 )  
    The paper presents a linearization method of governing equations for oil-water flow in porous media, discretized to locally perpendicular grids. By using an approximate vector, the same stability is obtained as the semi-implicit solution with IMPES through solving the N×N matrices twice. The operation procedure is presented. The modified IMPES also enjoys much higher computation efficiency. The simulation example shows the effectiveness. The method can be generalized for the numerical solution for other types of non-linear diffusion equations.
    2003, 25(4):  0-0.  doi:10.6052/1000-0992-2002-248
    Abstract ( 1360 )   PDF (202KB) ( 661 )  
    In order to describe the nonlinear contact between drillstring and hole wall, the multi-directional contact gap element (MCGE) is constructed and its formulas are derived. Through the MCGE connection with the beam element, the contact and geometric nonlinear finite element of drillstring is obtained in this paper. The application of this method to the GP1 well in the Daqing oil field shows that the contact friction force of the drillstring at any well depth can be obtained and the calculating error of the hole top load is below 10\%. The results may provide a theoretical basis for the design and operation of drillstring.
    2003, 25(4):  0-0.  doi:10.6052/1000-0992-2002-261
    Abstract ( 984 )   PDF (286KB) ( 511 )  
    In order to clarify the effect of the atmospheric pressure on the heat and moisture transfer within hygroscopic fabrics, based on the improved sorption rate equation and the Darcy's law, an analytical model is proposed. From the fit between the theoretically calculated temperature changes and those measured from experiments, it is shown that the models can predict the simultaneous heat transfer that is coupled in the moisture-diffusion process during humidity transients. Furthermore, the temperature and moisture concentration distribution in the inter-fiber void space at different atmospheric pressure conditions are numerically computed and compared. It shows that at the low atmospheric pressure, the temperature peak and the density of vapor are higher than those at the high atmospheric pressure.
    2003, 25(4):  0-0.  doi:10.6052/1000-0992-2002-291
    Abstract ( 1183 )   PDF (272KB) ( 555 )  
    The catenary finite element deduced by H.B. Jayaraman in the 1980's has a high precision compared to other finite cable element. However, when the initial unstressed length of the cable is near the length of the chord, iteration may be unsuccessful. In this paper, an improved algorithm is presented. The results show that the new method is effective and can be used in design.
    2003, 25(4):  0-0.  doi:10.6052/1000-0992-2002-328
    Abstract ( 1246 )   PDF (328KB) ( 842 )  
    Hydraulic shock absorber is a key device of sled impact test for automobile components. This paper proposes a mechanical model of hydraulic shock absorber for sled impact test based on the law of orifice flow, and discusses the factors influencing the model. After the optimization of these factors, simulation curves can be made, which agree with the test curves very well. The simulating process provides a reliable basis of setting up a model for this kind of absorber and adjusting the absorber to simulate the real car crash process.
    2003, 25(4):  0-0.  doi:10.6052/1000-0992-2002-361
    Abstract ( 1056 )   PDF (178KB) ( 739 )  
    In this paper, a laser speckle interferometry method using standard specimens is used to measure the coefficient of thermal expansion (CTE). It can avoid the precise measurement of temperature and it only uses the testing data of thermal deformations on the specimens. With relatively simple experimental equipments CTE of materials can be obtained with high precision.
    2003, 25(4):  0-0.  doi:10.6052/1000-0992-2002-396
    Abstract ( 894 )   PDF (254KB) ( 524 )  
    The change of the detonation intensity and the behavior of the wave are studied by a numerical simulation. It is shown that the detonation wave is weakened to deflagration partly in the initial stage of propagating into the large section channels, and the detonation is re-ignited by the high pressure and high temperature zone generated by Mach reflection created by the interaction of the shock wave and the well.
    2003, 25(4):  0-0.  doi:10.6052/1000-0992-2002-411
    Abstract ( 1013 )   PDF (544KB) ( 619 )  
    In this paper the feature of the dual tones of the Chinese Music Bells is discussed by the vibration theory and FEM.
    2003, 25(4):  0-0.  doi:10.6052/1000-0992-2003-043
    Abstract ( 1191 )   PDF (154KB) ( 558 )  
    In this paper, catastrophe theory is applied to investigate of the static buckling of elastic arches. The influences of the deflection change and axial deformation are considered. A cusp catastrophic model and the critical condition for static buckling of arches are obtained.
    2003, 25(4):  0-0.  doi:10.6052/1000-0992-2003-077
    Abstract ( 1152 )   PDF (738KB) ( 499 )  
    A contactless optical technique, Fourier transform grid method with integration of a digital image processing technique is applied to measure vibration amplitudes of the water surface wave generated in a vertical oscillating apparatus. It can obtain the wave height information corresponding to each pixel point with a high precision. The method offers a means for measuring the micro vibration amplitudes of water surface waves.
    2003, 25(4):  0-0.  doi:10.6052/1000-0992-2001-123
    Abstract ( 1051 )   PDF (327KB) ( 1004 )  
    It is an important phenomenon that in constructing the interchange tunnels in soft soil by shield, the surface will rise up when a tunnel is advanced over another nearby built tunnel, even if there is no under-excavation or over-injection of slurry in the course. A formula for the surface rise is presented based on the theory of elasticity to explain the phenomenon, and a mathematical model to evaluate the entire movement of the surface in construction of the interchange tunnels is established by combining the present formula with Peck's formula for the surface settlement. The case of Huangpu River Sightseeing Tunnel advanced over Shanghai Metro Line No.2 is studied, and the model gives results in a good agreement with the in-situ data.
    2003, 25(4):  0-0.  doi:10.6052/1000-0992-2001-525
    Abstract ( 1042 )   PDF (184KB) ( 548 )  
    In this paper the anti-plane moving crack in non-homogeneous elastic materials is studied by an analytical method. First the governing equations for homogeneous materials are solved by use of Fourier Cosine integral transform. Then the dual integral equation for moving crack is established according to the mixed boundary value conditions. It is shown that the dual integral equation can be reduced to the Fredholm integral equation of the second kind. Numerical results presented in the paper indicate that the non-homogeneity of materials has an important influence on the dynamic stress intensity factor.
    2003, 25(4):  0-0.  doi:10.6052/1000-0992-2002-011
    Abstract ( 922 )   PDF (724KB) ( 578 )  
    The advances of research on structural damage diagnosis is presented in this paper. The application of artificial neural networks to str- uctural damage identification is discussed. The structural damage detection and some expert systems based on artificial neural networks are introduced. Tendencies of structural damage diagnosis are pointed out.
    2003, 25(4):  0-0.  doi:10.6052/1000-0992-2002-013
    Abstract ( 1088 )   PDF (148KB) ( 475 )  
    By means of the transfer matrix method and a program of the computer algebraic system, the paper obtains the equation with the joint stiffness as the unknown. With the second natural frequency of the beams, the joint stiffness can be identified. The validity of this method has been proved by experiment.
    2003, 25(4):  0-0.  doi:10.6052/1000-0992-2002-052
    Abstract ( 1365 )  
    Fiber Bragg grating(FBG) strain sensors are calibrated and embedded into the reinforced concrete beams. Operating techniques and protective methods suitable for civil engineering structures are presented. With FBG sensors, internal strains of the reinforced concrete are determined in lab and on construction site. FBG sensors are ad- vantageous with respect to the absolute value measurement and long service life over the conventional electrical strain gauge in experiments. The results indicate that it is possible to build a structural health monitoring system based on fiber optic sensors.
    2003, 25(4):  0-0.  doi:10.6052/1000-0992-2002-117
    Abstract ( 1150 )  
    This paper provides a viscoelastic oscillatory equation for belt conveyors with different take-up assembly, and studies the equation's displacement solutions and the calculation method of the dynamic tension. It gives a dynamic design method of the take-up assembly, drive assembly and brake assembly, and a design method of reducing the conveyor belt's elastic vibration .
    2003, 25(4):  0-0.  doi:10.6052/1000-0879-2002-138
    Abstract ( 1237 )   PDF (447KB) ( 533 )  
    A solution to the low gas drainage efficiency for lower-permeability gas-filled coal in China is suggested based on the theoretical analysis and model investigation of the stress-relief moving rules for the roof stratum during working. With this method, the gas is drained from the roof stratum with a strike long-distance drill according to the developing characteristics of the cracks resulting from the stress relief of the mining roof stratum. The contribution of the roof stratum structure and the horizon of the key seam to the displacing rules of the roof stratum is analyzed, and the proper zone for the strike long-distance drainage is provided. Judged from the practical experience, the strike long-distance drainage in the roof stratum, with a drainage percentage of 20\% for working face, is an ideal method for the coal seam with lower permeability.
    2003, 25(4):  0-0.  doi:10.6052/1000-0992-2002-187
    Abstract ( 1054 )   PDF (591KB) ( 813 )  
    This paper introduces and compares the most widely used techniques in the non-destructive evaluation of residual stress. The emphasis is on magnetic methods. This paper also introduces a new residual stress measuring kit, MAPS, which is compared with other conventional devices. Since researchers in the mainland are also making a similar device, this paper will be of value to them. This paper also compares the results obtained from MAPS, neutron diffraction, and X-ray.
    2003, 25(4):  0-0.  doi:10.6052/1000-0992-2002-191
    Abstract ( 1101 )   PDF (174KB) ( 552 )  
    A method of Fourier series is proposed to calculate the critical flow velocity of pipes conveying fluid. The comparison of the results using this method and the finite element analysis indicates that the method is simple and valid.