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10 December 2004, Volume 26 Issue 6
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    Education Study
    2004, 26(6):  0-0.  doi:10.6052/1000-0879-2003-318
    Abstract ( 1258 )   PDF (272KB) ( 622 )  
    From the structural stability condition, we use a box with cells as the simple model to simulate the wing structure, as the key part transferring force, so that we can keep the essential feature and make the problem to be expressed less complicated. It can be seen that the object function of the simple model is both non-convex, non-continuous, and has many local optima. The computational results show that the optimal structure layout would depend on the type of material, the value of loads, and the geometric parameters of the model.
    2004, 26(6):  0-0.  doi:10.6052/1000-0992-2003-327
    Abstract ( 1004 )   PDF (641KB) ( 654 )  
    The structural model and classification of the magnetic fluid (MF) were briefly introduced at first in this paper. And then the principles and applications of the MF seal, MF lubrication, MF polishing, thermal conduction with MF, transducer technique using MF, magnetic separation, MF printing, MF damper, MF micropump, MF film and applications in the medical field were reviewed. In the end, some prospective research work for the magnetic fluid technique was put forward .
    2004, 26(6):  0-0.  doi:10.6052/1000-0992-2003-341
    Abstract ( 910 )   PDF (287KB) ( 536 )  
    The dynamic model of a hybrid composite beam vibration control using shape memory alloy(SMA) is analyzed. This model is developed based on the one-dimensional SMA constitutive equation and multicell model, and considers the influence of transverse shear deformation of the hybrid composite beam. Semi-active control can reduce the response of the construction by changing its parameter. According to the switch control theory, the control law can be determined and then the semi-active control simulation is carried out. The numerical results show that the semi-active control is an effective way for SMA fiber composites.
    2004, 26(6):  0-0.  doi:10.6052/1000-0992-2003-354
    Abstract ( 1045 )   PDF (357KB) ( 428 )  
    The variation of viscosity of electrorheological suspensions (ERSs) with shear rates is investigated under different temperatures and without electrical fields by microstructural and rheological experiment. The results show that the values of viscosity under zero electrical field agree well with Krieger-Dougherty model and the values of percolation threshold depend mainly on the characteristics of particles and decrease with working temperatures. The variations are different in three stages of linear startup, non-linear power law mode and Bingham mode flowing when electrorhrological suspensions are exposed to an electrical field.
    2004, 26(6):  0-0.  doi:10.6052/1000-0992-2003-366
    Abstract ( 1091 )   PDF (305KB) ( 441 )  
    The classical problem of a round metal tube subjected to axial compressive loading was reexamined with the straight plastic hinge model including an eccentricity factor. Based on the energy equilibrium, the instantaneous load-displacement history was obtained. The influence of eccentricity on the configuration of load-displacement and mean crush load was discussed. The model reproduces enough experimental information.
    Application study
    2004, 26(6):  0-0.  doi:10.6052/1000-0992-2003-372
    Abstract ( 1030 )   PDF (296KB) ( 488 )  
    Based on the beam theory of two generalized displacements, the trial function is used to construct the displacement functions. Further the generalized thick/thin beam is established. Appling the method, the generalized thick/thin plate element is constructed based on the finite strips. Numerical analysis is carried out to test the theory in this paper. Results show that this element is excellent with high precision and free from shear locking.
    Education Study
    2004, 26(6):  0-0.  doi:10.6052/1000-0992-2003-374
    Abstract ( 1174 )   PDF (344KB) ( 397 )  
    The research on the injury during head-and-hood collision is important in determining the safety factors during the collision of pedestrians and cars. The problem is simplified in this paper to the collision of a flexible ball and an elastic plate with large deflection. With FEM, the dynamic response during head-and-hood collision is analyzed, based on which the influences of different factors on collision response are obtained. Finally, some guidance is put forward for designing the hood, which may have the function of protecting pedestrians.
    2004, 26(6):  0-0.  doi:10.6052/1000-0992-2003-375
    Abstract ( 1045 )   PDF (236KB) ( 453 )  
    Homotopy methods were used for computing model parameters of Cd + + ion transport through unsaturated soils. Numerical results demonstrate the feature of stability and global convergence of the homotopy methods. Calculated BTCs agree well with experimental BTCs. %Computational results could be referenced by practical problems.
    2004, 26(6):  0-0.  doi:10.6052/1000-0992-2003-381
    Abstract ( 919 )   PDF (250KB) ( 461 )  
    In this paper, the motion of the shell in the bore and the variation of physical and kinematical parameters in the explosive are investigated. From two different angles, the influence of pushing on shell's initial velocity and final precision is studied. The methods of improving its precision are proposed.
    2004, 26(6):  0-0.  doi:10.6052/1000-0992-2003-397
    Abstract ( 1310 )   PDF (220KB) ( 455 )  
    The canonical Hamiltonian equations for elastic rectangular thick or thin plate, also including plate on the elastic foundation, are derived. In the deriving procedures, only the basic equations of rectangular plate are used. From the Canonical Hamiltonian equations of elastic rectangular thick or thin plate, the analytical solutions with arbitrary boundary conditions could be obtained by the method of symplectic geometry.
    2004, 26(6):  0-0.  doi:10.6052/1000-0992-2003-420
    Abstract ( 1228 )   PDF (386KB) ( 445 )  
    In order to increase the explosion power of multi-component fuel mixture, a field experimental study is carried out on single ignition of a few dosage of ternary solid fuel mixture with unconfined volume dispersion, with optical and electrical testing methods. An optimized fuel mixture ratio is obtained for the test bomb. Experimental results show that the cloud dispersion effect of multi-component solid fuel mixture is better than trinitrotoluene's of the same mass. Overpressure within the explosion field of solid fuel mixture firstly decreases, then increases, and then decreases again with increase of distance, and the distribution of the overpressure field is similar. Explosion power of solid fuel mixture can be enhanced with a suitable increase of bomb density.
    2004, 26(6):  0-0.  doi:10.6052/1000-0992-2003-424
    Abstract ( 1409 )   PDF (243KB) ( 531 )  
    In this paper, the interface of the pipe/soil interaction is analyzed by ABAQUS software. The pipe-soil contact pair is formed by the master-slave method of the ABAQUS software, and the finite element model is established. The constitutive models of soil, including nonlinear elastic, porous elastic and Ramberg-Osgood models are adopted. The relationship between the pipe's weight and sinking is obtained, and the soil lateral mounding is also obtained in the computation, which can improve the pipe's stability. The computation results show that they agree with some test results and the pipe/soil interaction analysis can be made by ABAQUS software.
    2004, 26(6):  0-0.  doi:10.6052/1000-0992-2003-448
    Abstract ( 1104 )   PDF (307KB) ( 543 )  
    This paper gives the solution of a rectangular thin plate constrained with beam under any local uniform force. With the boundary compatible analysis of beam and rectangular thin plate, the analytic solution is obtained and the solution of rectangular thin plate with different boundary conditions could be obtained through altering the value of $EI$ and GIt.
    Application study
    2004, 26(6):  0-0.  doi:10.6052/1000-0992-2003-449
    Abstract ( 1409 )   PDF (361KB) ( 443 )  
    No matter what method one uses to the unsteady temperature field calculation of massive concrete forward difference method, central difference method or backward difference method, the error of temperature is inevitable. Based on Lagrange mean-value theorem and the uncoupling assumption of temperature difference and temperature change rate among all nodal points, an iterative algorithm is put forward, which proves to be an effective method for temperature field calculation of massive concrete. By this method, the calculation cost is decreased and at the same time, the solution precision can be under control when the time step is properly increased. On the other hand, if the time step is kept in a conventional level, the calculation cost is increased slightly, yet the solution precision can be greatly increased, and the numerical calculated results may approach the theoretical results.
    Education Study
    2004, 26(6):  0-0.  doi:10.6052/1000-0992-2003-458
    Abstract ( 1083 )   PDF (245KB) ( 514 )  
    The fundamental problems in applying DEM for investigation of nonlinear dynamical behavior of multispan rotator system are discussed, including the determination and calculation of effective stiffness and effective force.
    2004, 26(6):  0-0.  doi:10.6052/1000-0992-2003-470
    Abstract ( 1318 )   PDF (187KB) ( 462 )  
    The difference formula of the bi-harmonic equation is derived in the polar coordinate system. The finite difference solution to the elastic plane problem of a disk is carried out by successive overrelaxation. By comparing with the theoretical solution of the problem, the validity of the difference formula is verified. The result provides a new and convenient way to solve the plane problem of disk and other similar shapes.
    2004, 26(6):  0-0.  doi:10.6052/1000-0992-2003-520
    Abstract ( 1262 )   PDF (469KB) ( 550 )  
    Ultrasonic fatigue testing is an accelerated testing method with a frequency far beyond that of conventional fatigue experiment. The experimental results show that the fatigue strength at 20\,kHz of 50# axle steel and 40Cr steel will diminish continuously as far as 10 10 cycles. It is shown that 50# axle steel and 40Cr steel have no ``fatigue limit'' as in the conventional fatigue curve. So the design of fatigue strength based on fatigue testing at 10 7 cycles is not adequate. The SEM shows that the fatigue crack propagation initiates at the subsurface inclusions in the regime of N>10 7. Testing system of ultrasonic fatigue, operating principle and design of fatigue specimens are described in this paper.
    2004, 26(6):  0-0.  doi:10.6052/1000-0992-2004-055
    Abstract ( 1255 )   PDF (232KB) ( 502 )  
    The homogeneous torsional vibration as a special case of the vibration of a helical thin elastic rod is discussed in this paper. A rod with noncircular cross section and a rod with circular cross section and intrinsic curvature are under investigation. In the process of homogeneous torsional vibration all cross sections of the rod have a same torsional angle, and the configuration of centerline of the rod is not affected by the vibration. It is shown that the torsional vibration is caused by the asymmetry of the cross section and the intrinsic curvature of the rod. The torsional vibration of the rod is analogous to the motion of a simple pendulum, and there exists an exact solution for the dynamical equation. The similar vibration of an annular rod is a special case when the pitch angle of the helix is equal to zero.
    2004, 26(6):  0-0.  doi:10.6052/1000-0992-2004-072
    Abstract ( 1393 )   PDF (319KB) ( 413 )  
    The Buckingham equation expresses the relationship between laminar flow velocity and resistance of the Bingham fluid. The Soviet scholar proposed an approximate formula for calculating flow resistance, based on which the maximum deviation relative to the exact solution was 6.7%. In this paper, with the mathematical analysis and three-dimensions optimization, and the change of the parameter of the approximate formula, the deviation is decreased to a great extent. The deviation is the function of the parameter and the core-flow relative radius r0. By means of the limiting value, the continuous points and interrupted points in the $\bar r0 closed region are determined, which provides a basis for reducing the deviation in the whole region. In the three-dimensional figure of the deviations, the problem to seek the max-value on multi-peak curved surface can be resolved by the use of the cutting plane. Finally, with the optimized parameter, the maximum deviation of the approximate equation becomes 2.6%, a reduction of 4.1% comparing to 6.7%.
    Application study
    2004, 26(6):  0-0.  doi:10.6052/1000-0992-2004-355
    Abstract ( 1330 )   PDF (659KB) ( 454 )  
    From the viewpoint of mechanics, the essence of seismogenic process is the damage evolution of the focal media, so it is mainly a mechanical process. But the earthquake prediction is different from other mechanics problems in engineering. The constitutive law, boundary condition, initial condition and the history of some mechanics quantities (such as rheology) must be known in a resolvable mechanics problem in engineering. But in earthquake generation they are unknown or almost unknown, and only the variation of some physical quantities in the earth crust can be measured. From this consideration, the concept of load/unload response ratio (LURR) was proposed as a new approach to earthquake prediction. In this paper the basic concepts, case-examination and some new results of LURR are introduced.