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10 February 2005, Volume 27 Issue 1
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    Application study
    2005, 27(1):  0-0.  doi:10.6052/1000-0992-2003-111
    Abstract ( 1277 )   PDF (541KB) ( 463 )  
    To reduce the computing time per step, a new hybrid high resolution difference scheme is constructed. The new scheme makes use of high resolution scheme or low resolution scheme through an adaptive switch function, depending on the gradient of the solution in a region. So the new scheme is adaptive and multiresolution. The results of numerical simulation show that the new scheme can effectively reduce the computing time per step.
    2005, 27(1):  0-0.  doi:10.6052/1000-0992-2003-137
    Abstract ( 1079 )   PDF (634KB) ( 488 )  
    Because of the sedimentation of soil, many foundations can be considered as transversely isotropic. In this article, based on theories of mathematics and mechanics, the constitutive model of a transversely isotropic foundation is proposed together with the methods of determining related parameters. The model is found easy to use in engineering. As far as the sedimentation of soil is concerned, the constitutive model gives more realistic stress and strain response than the isotropic model.
    2005, 27(1):  0-0.  doi:10.6052/1000-0992-2003-338
    Abstract ( 1169 )   PDF (565KB) ( 476 )  
    On the basis of the interaction of pile and soil, the software ANSYS was used to build the computational module for pile-group foundation. The computational results in uniform soil agree very well with traditional results. With foundation soil's measurement data of Liaoning Technical University's experiment building, the ratio of pile and loading board was obtained.
    2005, 27(1):  0-0.  doi:10.6052/1000-0992-2003-401
    Abstract ( 1334 )   PDF (792KB) ( 667 )  
    A theoretical approach is presented for analyzing the in-plane mechanical properties of the stitched composite laminates based on the microstructures of fibers near the stitch holes. The geometrical characteristics of the distorted fibers in the stitch unit cells are considered. The elastic constants and stiffness matrices of lamina and laminate are obtained finally. The effects of stitching parameters on the equivalent elastic modulus of the laminates are studied using the finite element analysis. The results show that the material properties of stitched composite laminates are inhomogeneous due to stitching, and the equivalent elastic modulus of the laminates decreases with the increase of the stitch density and thread diameter.
    2005, 27(1):  0-0.  doi:10.6052/1000-0879-2003-411
    Abstract ( 1099 )   PDF (992KB) ( 774 )  
    This paper presents a theoretical investigation for the form finding and the loading analyses of membrane structures by using the finite element package ANSYS. The tension structures under loading usually involve large displacements, so the non-linear theory is applied in the investigation. It is found that the results of form finding depend on the following factors: the meshing, the elastic moduli of the membrane material, the initial stress in the membrane, the stress in the boundary cables and the ridge cables and their ratio. In practical engineering, it is difficult to find out the minimal surface meeting the architecture demands and the boundary restrictions, hence, the difference in the stress distribution should be controlled in a special range. The computational results for practical examples show that the effect of the wind loading on the vertical displacement is significant. Usually the design of membrane structures is controlled by the wind suction.
    2005, 27(1):  0-0.  doi:10.6052/1000-0992-2003-472
    Abstract ( 1197 )   PDF (436KB) ( 524 )  
    In this paper an efficient iteration format of the precise symplectic integration method is proposed to reduce the computation amount. At the same time, the simplified form and its error estimation are also proposed to avoid complicated matrix inversion operation. This method is programmed to justify its validity. It is proved that this method can speed up the calculation process and has high precision and stability.
    2005, 27(1):  0-0.  doi:10.6052/1000-0992-2003-496
    Abstract ( 1038 )   PDF (513KB) ( 540 )  
    Based on the theory of multi-color dyeing, the elements of FEM were sorted with arbitrary number of elements in the neighborhood of the same node. While composing the stiffness matrix, the same set of elements can be treated by parallel computation. So the efficiency of composing the stiffness matrix was raised. The parallel algorithm was carried out on parallel platform PVM with good results.
    Education Study
    2005, 27(1):  0-0.  doi:10.6052/1000-0992-2003-500
    Abstract ( 1118 )   PDF (567KB) ( 444 )  
    Based on the structure and material property of concrete beam strengthened with carbon fiber reinforced plastics (CFRP) and looked CFRP as a series of chain poles on the strengthened beam, mechanics model is built and analyzed by using the Force Method. A coefficient K is put forward and studied in this paper.
    Application study
    2005, 27(1):  0-0.  doi:10.6052/1000-0992-2003-515
    Abstract ( 1155 )   PDF (792KB) ( 471 )  
    The main factors that influence the performance of evaporators are the high energy consumption in the forced circulation pump and the cyclic stop of equipment operation to remove the salt fouling. The self-cleaning evaporator with natural circulation can solve such problems satisfactorily. The driving force of natural circulation is obtained based on the concept of dynamic temperature and the process of nonequilibrium vaporization. The calculating model is used to effectively enlarge the driving force of natural circulation. The boiling chamber is designed with large cross-section and depth and gradually increased section at outlet in order to increase the vaporization equilibrium and reduce the kinetic energy loss at outlet. The heat transfer tubes in the heating chamber must be short, in which twisted strip inserts with oblique teeth are installed to efficiently remove salt fouling automatically and to enhance heat transfer with low flow resistance at low fluid flowing velocity, so that the dynamic temperature is raised and the overall resistance of natural circulation is lowered. The industrial experiments of such new evaporators have been successful.
    2005, 27(1):  0-0.  doi:10.6052/1000-0992-2003-517
    Abstract ( 1059 )   PDF (326KB) ( 443 )  
    The peeling failure of the concrete cover of RC beams strengthened with fiber reinforced polymer (FRP) is analyized. An approximate method to estimate the upper limit of midspan peeling stress of RC strengthened beams is proposed.
    2005, 27(1):  0-0.  doi:10.6052/1000-0992-2004-019
    Abstract ( 1393 )   PDF (632KB) ( 484 )  
    Autofrettage in outer sleeves is used to improve carrying capacities of hydraulic coupling. Linear hardening model is used for residual stresses after autofrettage pressurization and after autofrettage depressurization. It is indicated that the best ratio of external radius to inner radius relates not only to the yielding limit, elastic modulus and linear strengthening elastic modulus but also to Bauschinger effect factors. The calculated results for the sizes given by CB*3235-84 shows that compared with non-autofrettaged ones, carrying capacities of autofrettaged outer sleeves increases by nearly 50 percent.
    2005, 27(1):  0-0.  doi:10.6052/1000-0992-2004-036
    Abstract ( 1131 )   PDF (608KB) ( 500 )  
    Geometrical nonlinearity, contact nonlinearity and material nonlinearity caused by impact large deformation are considered. The finite element model is built to simulate the axial impacts of composite material tubes. The impact energy absorption behavior of glass/epoxy tubes is analyzed. The calculation results agree well with the experiments, which assures the validity of this finite element model. The effects of lay angle on energy absorption capability of composite material tubes are studied.
    2005, 27(1):  0-0.  doi:10.6052/1000-0992-2004-071
    Abstract ( 1165 )   PDF (720KB) ( 470 )  
    The flutters of cutting-tools in mechanical processes are investigated in this paper. The flutters are typically self-excited oscillations and could be described by the well-known van der Pol equations. The analytical solutions of the van der Pol equations obtained by the averaging method show the mechanism of the self-oscillations. A new strategy of linear feedback is developed to control the flutters. The control strategy could be realized by a delayed linear function. The analytical solutions of the van der Pol equations with delayed linear feedback show that the flutters could be effectively reduced. Numerical simulations confirm the theoretical predictions.
    2005, 27(1):  0-0.  doi:10.6052/1000-0879-2004-096
    Abstract ( 1574 )   PDF (584KB) ( 476 )  
    The direct differentiation method is used for design sensitivity analysis of multibody system dynamics which is described by differential/algebraic equations with holonomic constraints. The results can be used to optimization of multibody system dynamics with generic objective functions and constraints. An example of a planar manipulator with two links is analyzed to test the given methods.
    Education Study
    2005, 27(1):  0-0.  doi:10.6052/1000-0992-2004-111
    Abstract ( 1463 )   PDF (1540KB) ( 492 )  
    Damage detection in spatial lattice structures is an important research subject in the present structural engineering field. Its applications and recent research advances are reviewed in this paper. The classification and the basic idea of various methods are discussed. The flexibility methods and the model updating methods are paid a special attention. Some questions existing in the theory and applications are presented and some future research trends on damage detection of spatial lattice structures are outlined.
    Application study
    2005, 27(1):  0-0.  doi:10.6052/1000-0992-2004-148
    Abstract ( 1268 )   PDF (1038KB) ( 444 )  
    The sand particle velocity and concentration of solid-gas two phase flow are studied in the environmental test equipment with gravity applied on top. Using the wind tunnel of CAREERI of CAS and applying laser digital particle imaging technology, the particle velocity and space distribution in different sections of the sand orifice along the wind horizontal direction is determined. In this paper, it is shown that the particle velocity can approach the wind velocity and the particle can just diffuse to the whole space only in the section that is about three meters horizontally from the sand orifice. It provides a basis to develop the large-scale sand and dust experimental test equipment.
    2005, 27(1):  0-0.  doi:10.6052/1000-0992-2004-213
    Abstract ( 1674 )   PDF (607KB) ( 746 )  
    On the basis of finely measured logarithmic mean-velocity profile in the near wall region of turbulent boundary layer over a flat plate in a wind tunnel using hot-wire anemometer of model IFA-300, we calculate the skin friction velocity according to the relationship between inner-scale physical parameters of logarithmic mean-velocity profile in the near wall region of turbulent boundary layer, such as mean velocity, skin friction velocity and fluid dynamics viscosity, and the relationship between skin friction velocity and skin friction drag. The skin friction measurement in a turbulent boundary layer is achieved by non-perturbed or micro-perturbed technique using logarithmic mean-velocity profile method. The present experimental method is simple, cheap and precise and without the need to use any complex equipment, such as sensors or balance, and to damage the surface of the plate. What is more, the original flow condition in the near wall region of turbulent boundary layer is not disturbed. With its high automatic level and reliable experiment results, the mean-velocity profile method enjoys high efficiency and precision, for the measurement of skin friction drag in turbulent boundary layer.
    2005, 27(1):  0-0.  doi:10.6052/1000-0879-2004-250
    Abstract ( 1386 )   PDF (866KB) ( 599 )  
    Modern numerical simulation plays a very significant role in structural design engineering in improving the design qualities, shortening the development period and reducing cost. Applying a commercial finite element analysis system, this paper presents an integrated design process of frontal windshield of an airplane, including CAD structural design, numerical simulation and experimental validation. The paper discusses the reasonable element selection, material constitutive model, the effect of different boundary conditions and experimental arrangements. Especially a three-dimensional non-linear viscoelastic model is derived and coded. A bird impact windshield experiment is carried out, and the comparison of the experiment with the numerical simulation is performed, showing that the simulation results in this paper enjoy a high level of credibility, as shown in Figs.3 through 12.
    2005, 27(1):  0-0.  doi:10.6052/1000-0992-2004-423
    Abstract ( 1428 )   PDF (1506KB) ( 1605 )  
    The various problems in urban roadway traffic are discussed. The progress in the traffic flow models based on fluid dynamics, gas kinetics, car following and cellular automaton is summarized from the point of view of continuous, probability and discrete methods. The features of these models are described. At last, the further prospective research on traffic flow is cxamined.