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10 February 2006, Volume 28 Issue 1
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    Education Study
    2006, 28(1):  0-0.  doi:10.6052/1000-0992-2004-341
    Abstract ( 1470 )   PDF (572KB) ( 843 )  
    In view of the fact that for the cold upset mold of the whole-mold structure, the fatigue life is rather short, a new design method is proposed to replace the whole mold with the mold structure of a three-layer cylinder and thus to change the loading on the mold and to achieve a longer life. According to the testing results of cold upset bolt and the results of stress analysis, empirical formulas are obtained.
    2006, 28(1):  0-0.  doi:10.6052/1000-0879-2005-005
    Abstract ( 1324 )   PDF (636KB) ( 586 )  
    Based on a bi-directional approach, the paper discusses the motion planning of free-flying space manipulators with prismatic joint. Considering its nonholonomic nature, the vehicle orientation can be controlled in addition to the joint variables of the manipulators, by actuating only the joint variables. As the result, the fuel consumption for controlling the vehicle orientation is reduced and the life-span of space manipulator system is prolonged. A planar space manipulator with prismatic joint is simulated to verify the proposed approach.
    2006, 28(1):  0-0.  doi:10.6052/1000-0879-2005-006
    Abstract ( 1334 )   PDF (784KB) ( 762 )  
    In this paper, in order to annlysis the influence of multi-layer component on microhardness testing, the pressing process of the indenter is simulated by FEPG (Finite Element Program Generator) software. The effects on multi-layers system including of different material soft layers, different thickness proportion between soft layer and hard layer and different layer number in the multilayer are analyzed. A conclusion that multilayer construct according to gradient layer can enhance film performance is drew. It is helpful to provide the reference data for microhardness testing.
    2006, 28(1):  0-0.  doi:10.6052/1000-0879-2005-020
    Abstract ( 1460 )   PDF (1280KB) ( 729 )  
    The resonant frequencies and corresponding mode shapes of steel thin-wall cylinder shell samples each containing an oblique crack are obtained by a laser holographic interferometry method. It is shown that the oblique cracks have a great effect upon the vibration characteristics of the shells, with the mode shapes of the shell being changed very much and looking very complicated. A kind of vibration appeared only in the local area round the crack which is called the partial vibration by this paper is discovered. The partial vibration, which is responsible for the complicated mode shapes, has resonant frequencies and modes of vibration of its own. The vibration appeared in the entire shell is called the original whole vibration. In a similar way, the original whole vibration has the resonant frequencies and modes of vibration of its own. When the resonant frequencies of the partial vibration close to that of the original whole vibration, the two kinds of vibrations will come together. So there are three kinds of vibration mode shapes: pure partial vibration mode shapes, pure original whole vibration mode shapes and the intercoupling vibration mode shapes in which partial vibration and original vibration interact with each other. The longer the crack is, the lower the resonant frequencies of the pure partial vibration and pure original whole vibration are, but the resonant frequencies of the intercoupling vibration occasionally shows an inverse tendency, which is a phenomenon which may be confused with two kinds of the resonant frequencies.
    2006, 28(1):  0-0.  doi:10.6052/1000-0992-2005-031
    Abstract ( 1487 )   PDF (741KB) ( 636 )  
    A great number of frozen clay specimens are used for the long-term creep tests under single-axial stress states. The results of experiment show that the transient deformation of the soil can be neglected and a simple yielding function can be used to replace the linear Newton element, to improve the Nishihara model for the triaxial nonlinear creep of frozen clay. By means of that improved model, a formula is derived to calculate the stress and displacement field of frozen wall. Calculation results are close to actual situations.
    2006, 28(1):  0-0.  doi:10.6052/1000-0992-2005-045
    Abstract ( 1229 )   PDF (1955KB) ( 1013 )  
    It is difficult to use a theoretical method to analyse the radiated sound field caused by the vibration of pipes. In this paper, an analysis of the radiated sound field caused by the vibration of pipes is made using the finite element method. The pattern of the pressure distribution of the sound field was obtained from the calculation, which provides a basis for vibration noise control.
    2006, 28(1):  0-0.  doi:10.6052/1000-0992-2005-047
    Abstract ( 1079 )   PDF (789KB) ( 680 )  
    With the theory of iterative mapping and stability analysis, the harmonic excitation response and periodic response stability of a vertical impact damper system is studied. First, the equation of parameter boundary of stable response is set up. General rules of transformation from stability to chaos are analyzed. Finally, numerical results with a better damper effect are obtained by analyzing a typical quadratic periodic response vibration system. The vibration reduction effects for stable state periodic response around the region are discussed.
    2006, 28(1):  0-0.  doi:10.6052/1000-0992-2005-063
    Abstract ( 1216 )   PDF (1109KB) ( 867 )  
    The optimization of building-complex arrangement and the design of structural wind resistance require an exact prediction of wind environment around the building complex. In view of the importance of wind environment, a numerical simulation (CFD) is introduced for the prediction of wind effect around the building complex. The wind velocity and pressure in various building arrangements are simulated and analyzed. A reasonable pneumatic layout for given buildings is obtained. The wind tunnel test can be carried out based on the prediction of the numerical simulation. At the same time, the numerical simulation can provide a scientific basis for the optimization of the building-complex arrangement and the design of structural wind resistance.
    2006, 28(1):  0-0.  doi:10.6052/1000-0992-2005-081
    Abstract ( 1345 )   PDF (827KB) ( 774 )  
    Elastic finite element analyses are conducted to investigate the factors influencing the membrane behavior of steel-concrete composite floor slabs. Parameters include concrete slab thickness, lateral stiffness of frames and the arrangement of the lateral stiffness system. The results show that the membrane behavior of composite floor slabs is influenced not also by the length-width ratio but also its in-plane stiffness and the lateral system. A new method of evaluating the membrane behavior of composite floor slabs is established based on the parameter studies. The method is proved to be valid by comparison with the test results. The method mentioned in this paper provides a useful tool in composite floor slab design.
    2006, 28(1):  0-0.  doi:10.6052/1000-0992-2005-085
    Abstract ( 1343 )   PDF (902KB) ( 759 )  
    The calculation of internal force's envelope diagram for a bridge under moving loads is a typical problem which can be solved by the computer simulation. In this paper, a computer simulation is made for the vehicle load moving on a highway's bridge with a small step length. For each step, the internal force diagram is plotted. When the vehicle load moves through the bridge, these internal force diagrams will fill in a region. The up-lower boundary of the region is just the internal force envelope diagram. The algorithm in this paper does not depend upon the concept of the influence line, hence the calculation is simple.
    2006, 28(1):  0-0.  doi:10.6052/1000-0992-2005-112
    Abstract ( 1290 )   PDF (956KB) ( 860 )  
    The dynamic behaviors of the artillery recoiling parts have an important effect on the measurement accuracy of the artillery launch test and the evaluation of the artillery performance. In this paper, we determine the optimum response points and driving points of the structure on the basis of the FEA model, then obtain the natural frequencies and modes of the structure with the optimized model of the experimental modal analysis. The test results show that the FEA analysis can improve the efficiency of the experimental modal analysis and the dynamic performance of the structure could be obtained with good accuracy.
    2006, 28(1):  0-0.  doi:10.6052/1000-0879-2005-125
    Abstract ( 1453 )   PDF (763KB) ( 613 )  
    The velocity time sequence at different vertical locations in a turbulent pipe flow with different surface coating was carefully measured by IFA300 constant-temperature anemometer with a resolution higher than the frequency with respect to Kolmogorov dissipative scale. A method is put forward to calculate the skin friction velocity by means of nonlinear iteration, in order to achieve a non-perturbed or micro-perturbed measurement of wall shear stress. The relationship among some inner-scale physical parameters, e.g., the mean-velocity profile, skin friction velocity and fluid dynamics viscosity, and the relationship between skin friction velocity and skin friction shear stress were used in accurately calculating the skin friction drag based on the precise measurement of logarithmic mean-velocity profile in the near wall region of turbulent boundary layer. The velocity signals were decomposed into multi-scale eddy structures by wavelet transform. A conditional sampling technique for the multi-scale coherent eddy structure detection from the simultaneous turbulent field was introduced using the multi-scale instantaneous intensity factor and multi-scale flatness factor of wavelet coefficients. Coherent eddy structures for different scales were extracted by this technique and the mechanism of surface coating drag reduction is investigated for gas transportation of turbulent pipe flow.
    2006, 28(1):  0-0.  doi:10.6052/1000-0992-2005-304
    Abstract ( 1235 )   PDF (659KB) ( 620 )  
    The ultimate bearing capacity of curved beams is related with the bending- torsion strength and the stability. With elastic-plastic deformation, the bending stress and the torsion stress are not linear with respect to the strain, so the problem will be more complicated. In this paper, using different formulae of the ultimate capacity of curved beams, a regression model is obtained. Through the nonlinear regression calculation for a lot of computational results obtained by using the finite element method, a simplified and useful calculation formula is proposed, which can be used in the practical design of the curved beams.
    2006, 28(1):  0-0.  doi:10.6052/1000-0992-2005-319
    Abstract ( 1142 )   PDF (971KB) ( 652 )  
    In view of the complex environment of demolision project of Zhangze power plant workshops in Shanxi province and the workshop's actual structure, we divide the workshop into three explosion areas and determine the overall directional demolition plan with one explosive initiation point, 12 sound elemental difference delays, and a non-electrically strengthened dual-loop demolition network. The demolition vibration is calculated and verified. Effective measures are taken to reduce the cave in distance. Good blasting results are obtained.
    Around the mechanics
    2006, 28(1):  0-0.  doi:10.6052/1000-0992-2005-320
    Abstract ( 1529 )   PDF (1267KB) ( 546 )  
    Numerical simulation is an important method to study the pollution problem due to the wastewater discharge. The features of water flow and wastewater distribution and related difficulties in numerical simulation are discussed in the present paper. Both advantages and disadvantages of the depth-averaged model and varied multi-layer models are analyzed when they are applied to investigate the wastewater discharging into Three Gorges Reservoir (TGR). The present study may be helpful to the further development of wastewater effluent model for TGR as well.
    Education Study
    2006, 28(1):  0-0.  doi:10.6052/1000-0879-2005-408
    Abstract ( 1157 )   PDF (1628KB) ( 728 )  
    Based on the concept of intelligent structures, self-coupled dampers composed of electrorheological (ER) fluids and piezoelectric ceramics are proposed in this paper. Unlike the conventional ER dampers, the self-coupled dampers employ piezoelectric ceramics to respond the external vibration and to provide the electric field for solidification of ER fluids. With a change in the external vibration, the electric field changes accordingly due to the piezoelectric ceramics, resulting in an adaptive control process. The self-coupled dampers have a simple and compact structure since the high voltage supply and the control system are not involved. Two generation products of the self-coupled dampers have been manufactured. Several modifications have been included in the second generation self-coupled damper and both the stability and the reliability of the damper are improved.