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08 August 2010, Volume 32 Issue 4
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    Education Study
    2010, 32(4):  104-106.  doi:10.6052/1000-0879-lxysj2009-388
    Abstract ( 1514 )   PDF (428KB) ( 647 )  
    Microsoft Excel is an ordinary office software which has powerful data processing and chart functions. The internal forces for every section of three-hinged arches are computed by setting Excel formula and internal functions. And the internal force curves of three-hinged arches are drawn by use of the Excel charts. It is useful for three-hinged arches teaching and increasing students’ interests to learn three-hinged arches to implement the complex three-hinged arch internal force computations, and draw the internal force curves accurately and quickly by use of Excel.
    Application study
    2010, 32(4):  35-39.  doi:10.6052/1000-0879-lxysj2009-395
    Abstract ( 1566 )   PDF (1303KB) ( 509 )  
    With the displacement function expressed in single trigonometric series, the circumferential bending problem of the cylindrical shell under arbitrary normal distributed load and simply supported in the opposite edges, is solved. Approximately taking the distributed load as a linear load in the infinitesimal rectangle region, the circumferential bending deformation formula of the cylindrical shell under the linear load is deduced. The special formula is obtained when the linear load is uniformly-distributed and linearly varying. The results show that, under given boundary constraints, the displacement distribution of the cylindrical shell circumferential bending deformation calculated by the theoretical method is consistent with that calculated by FEA.
    Education Study
    2010, 32(4):  90-93.  doi:10.6052/1000-0879-lxysj2009-396
    Abstract ( 1481 )   PDF (1092KB) ( 674 )  
    Theory of beam is very important in engineering field. According to shear effect, it can be divided into Euler beam, Timoshenko beam and high order shear beam. Most engineering problems can be analyzed by using Euler’s or Timoshenko’s beam theories according the slenderness ratio of the engineering component is large or small. In this investigation both Euler’s and Timoshenko’s beam theories have been used to analyze the clamp-clamp uniform slender beam acted on uniform distributed applied couple. Abaqus finite element software has been used to resolve one example to validate the theoretical results. As to this load and boundary condition, analysis of slender beam must take into the shear effect account.
    Application study
    2010, 32(4):  12-17.  doi:10.6052/1000-0879-lxysj2009-404
    Abstract ( 1660 )   PDF (4207KB) ( 512 )  
    The relationship between hydraulic conductivity of a porous material and its number-size is simulated by using the finite element method. The solid matrix and the pore space are generated randomly according to the material porosity, and the material parameters and the element properties are assigned by the ANSYS parameter design language. The equivalent hydraulic conductivity is computed according to the flow flux through some section computed by FEM and Darcy law, and the relationship between the equivalent hydraulic conductivity and the porosity number-size of porous materials is obtained. The numerical simulation shows that the equivalent hydraulic conductivity is directly proportional to the square of the porosity size while the porosity is constant, for which the proposed conclusion agrees well with empirical expressions. The equivalent hydraulic conductivity is directly proportional to the porosity while the porosity size is constant.
    2010, 32(4):  58-61.  doi:10.6052/1000-0879-lxysj2009-407
    Abstract ( 1137 )   PDF (834KB) ( 494 )  
    The lumped mass at the centroid will gives more accurate results for dynamic problems, and also make it possible to optimize the element inertia effect and improve the matching between the element inertia and deformation effects. The detailed analyses of the frequency-dispersion effect for a one-dimensional problem shows the validity of the method.
    Education Study
    2010, 32(4):  79-80.  doi:10.6052/1000-0879-lxysj2009-423
    Abstract ( 1196 )   PDF (564KB) ( 557 )  
    Application study
    2010, 32(4):  30-34.  doi:10.6052/1000-0879-lxysj2009-457
    Abstract ( 1024 )   PDF (1120KB) ( 418 )  
    The leakage after CO_2 sequestration is critical in the evaluation of CO_2 storage period and the stability of the cap-rock. In this paper, the commercial FEM software ABAQUS is used with a secondary development to analyze the key factors of CO_2 seepage. Meanwhile the gas Vander-Walls equation is applied to the supercritical CO_2 compared to the ideal gas equation. A simple theoretical result is obtained and verified in a good agreement with that of simulation. The results show that at least 150 000 years are needed until CO_2 escapes completely from a homogeneous cap-rock with a low permeability; the number storage duration is decreaseds to 10 000 years when there is a high permeability leaky well or fractures, hence, fractures or leaky wells should be consolidated before sequestration or kept away from project areas.
    2010, 32(4):  40-46.  doi:10.6052/1000-0879-lxysj2009-463
    Abstract ( 1255 )   PDF (2312KB) ( 442 )  
    The timber structure with high-platform foundation is the main form of historic buildings in China, such as bell tower and drum tower. Taking Xi'an Bell Tower as an example, a three-dimensional finite element model of the bell tower-soil-tunnel structure interaction is built, and the dynamic response of the bell tower under simulated metro-induced loading is obtained by means of dynamic finite element analysis. The vibration response of the bell tower under ground traffic loads were obtained through all-weather field monitoring. These two results are combined by using the SRSS method to obtain the response of the timber structure of the bell tower under combined action of ground and underground traffic loadings. The structure may be evaluated according to the technical specifications, the results may serve as a reference for dynamic response analysis and assessment of similar historic buildings under traffic loads.
    2010, 32(4):  47-50.  doi:10.6052/1000-0879-lxysj2009-479
    Abstract ( 1232 )   PDF (692KB) ( 456 )  
    Transient response analysis of structures under seismic load is important in a seismic design. Most earthquake effect studies use time domain numerical integration methods. The method of reverberation ray matrix is a novel frequency domain matrix method for transient analysis of trusses and frames. Based on Bernoulli beam theory, the present work extends the reverberation ray matrix method to the case of ground acceleration loads. The calculation of a piece of steel frame subjected to the ground El Centro acceleration wave demonstrates that the method can be used to analyze the earthquake effect of structure accurately and effectively.
    2010, 32(4):  27-29.  doi:10.6052/1000-0879-lxysj2009-506
    Abstract ( 1170 )   PDF (530KB) ( 401 )  
    Using basic assumptions and solutions of spatial axisymmetric problems of elasticity and the shear displacement method, an analysis model is proposed and the basic equations, are deduced with analytical solutions, which illustrate the attenuation curve with an example, together with the load transfer coefficient $k$ and its influence on the load transfer law.
    2010, 32(4):  51-57.  doi:10.6052/1000-0879-lxysj2010-006
    Abstract ( 1159 )   PDF (905KB) ( 523 )  
    The mode function is the key for obtaining the critical load of a stayed steel column. Based on two basic modes, symmetric and anti-symmetric, the basic buckling mode functions are obtained, and three examples are considered for the performance of simulation curves by varying their key parameters. At last, the buckling mode function for asymmetric buckling is obtained. The results indicate that the engineering requirements can be met when the number of simulation curves is equal to the total section number of the stayed steel column.
    2010, 32(4):  22-26.  doi:10.6052/1000-0879-lxysj2010-011
    Abstract ( 1256 )   PDF (3042KB) ( 416 )  
    In order to study the control of the combustion stability of the bulk-loaded liquid propellant gun (BLPG), a simulating equipment of ignition and injection of the BLPG and four kinds of stepped-wall chambers were designed. A high speed digital video system was used to observe the expansion process of the energetic gas jet in a liquid simulating medium. The congestion phenomenon in the experiment was analyzed. Results show that the jet expansion process in the stepped-wall chamber is stable and the injection pressure, the nozzle diameter and the stepped-wall geometry have a remarkable influence on the jet expansion and the mixing process of gas and liquid, so the jet expansion process can be controlled effectively by adjusting these parameters. The congestion of the nozzle causes dissymmetric jet expansion and affects the mixing process, so that it is unfavorable for controlling the jet stability.
    Interesting mechanics story
    2010, 32(4):  112-114.  doi:10.6052/1000-0879-lxysj2010-225
    Abstract ( 1172 )   PDF (2328KB) ( 531 )  
    Education Study
    2010, 32(4):  77-78.  doi:10.6052/1000-0879-lxysj2008-593
    Abstract ( 1249 )   PDF (666KB) ( 630 )  
    Interesting mechanics story
    2010, 32(4):  117-118.  doi:10.6052/1000-0879-lxysj2008-600
    Abstract ( 1401 )   PDF (516KB) ( 770 )  
    The motion is related to the threshold of some parameters such as friction and space size. Therefore periodical disturbance may be resulted in unilateral motion. The mechanical principle in several examples is discussed.
    Application study
    2010, 32(4):  62-65.  doi:10.6052/1000-0879-lxysj2009-025
    Abstract ( 1196 )   PDF (1019KB) ( 584 )  
    The vibratory stress relief (VSR) process works in a cyclic creep mechanism. To deal with the distortion in the welding of the HT-7U vacuum room, the residual stresses are eliminated in the welding place by a VSR process, to improve the size precision of the vacuum room. With an an analysis of dynamic stresses and the measurements of residual stresses before and after the VSR process, the reduction and redistribution of residual stresses can be evaluated. The experimental results show that the VSR process is effective.
    Education Study
    2010, 32(4):  93-96.  doi:10.6052/1000-0879-lxysj2009-131
    Abstract ( 1610 )   PDF (676KB) ( 433 )  
    An object-oriented program of the finite element method was designed by utilising FORTRAN90 program language and conjugating with the AutoCAD Drawing Exchang file-DXF. Runing availabe program at present. We are implementing preprocessor and post-processing function, including mesh generation automatically, element-node informatiom,equivalent node forces,constrained condition and deformation, stress diagram etc. It overcome shortcomings of necessary of input a mass of date and treat output results date in past the FEM teaching. Meanwhile we attain aim of visibility about preprocessor and post-processing.Let students primary learn the FEM technical of Object-Oriented Programming.
    2010, 32(4):  109-111.  doi:10.6052/1000-0879-lxysj2009-246
    Abstract ( 1754 )   PDF (608KB) ( 513 )  
    Firstly ,the degree of freedom of mechanics of university physcis from different degrees and angles are analysed in this paper. The studying methods are:(1)The characters of degree of freedom are introduced of mechanics .(2)The degree of freedom in the field of mechanics of university physcis are as following:1)The connection between the degree of freedom and coordinate is pointed out.The relation of free and restriction is listed.2) The number of degree of freedom of the same body changes along with its space changes by taking for examples. 3)The adding rules of degree of freedom are showed.4) The total number of mass point group is talked .5) The methods of calcilation of degree of freedom of mechanics are showed.Finally,the studying significance of the degree of freedom of mechanics of university physics is showed .
    Application study
    2010, 32(4):  18-21.  doi:10.6052/1000-0879-lxysj2009-248
    Abstract ( 1095 )   PDF (718KB) ( 464 )  
    The aerodynamic interference between cylinders is a topic of great theoretical and practical significance. Though some wind tunnel tests related to wind pressure distribution on cylinders complex have been carried out at home and abroad, only cylinders of equal-diameter and Reynolds number below 10$^{5}$ are considered. However, actual engineering structures are often immersed in wind flows of high Reynolds number. This paper studies the time-averaged flow at high Reynolds number ($Re=4.5\times 10^{5})$ around two cylinders of unequal-diameter, combined in tandem, side-by-side and in staggered styles, which is simulated by numerical methods, for various spacings and wind directions. The time-averaged drag, lift and resultant wind forces on two cylinders are obtained and analyzed. Which may serve as a reference for wind-resistant design for similar structures.
    2010, 32(4):  71-73.  doi:10.6052/1000-0879-lxysj2009-267
    Abstract ( 1210 )   PDF (467KB) ( 533 )  
    The wavelet-DQ method combines the classic differential quadrature (DQ) method, the multi-resolution analysis theory, and a constructor of scaling function-based interpolation base functions. This is a new method for solving boundary value problems of differential equations. This method is applied to analyze the longitudinal vibration of an elastic straight rod with variable cross-section, to obtain the frequency equation. With different parameters, the natural frequencies of clamped-clamped, free-free wedge-shaped straight rod and cone-shaped straight rod are obtained. Numerical results show that the method is simple and enjoys high-precision. This method can be applied to other mechanical problems in numerical analysis.
    Education Study
    2010, 32(4):  83-86.  doi:10.6052/1000-0879-lxysj2009-286
    Abstract ( 929 )   PDF (1474KB) ( 500 )  
    In this paper, the practical necessary of improving the calculation of force method is described. By carrying out a theoretical analysis, the traditional computational process of Force Method was improved. The improved computational process of Force Method has been implemented into Excel spreadsheets using VBA,and its effectiveness has been verified by an example.
    Interesting mechanics story
    2010, 32(4):  118-119.  doi:10.6052/1000-0879-lxysj2009-321
    Abstract ( 1845 )   PDF (623KB) ( 625 )  
    The analyzes of the principle to one kind of marvelous rotation from mechanics angle.
    Application study
    2010, 32(4):  66-70.  doi:10.6052/1000-0879-lxysj2009-348
    Abstract ( 1234 )   PDF (764KB) ( 454 )  
    The direct time integration methods for nonlinear dynamic equations are based on a relationship of state variables between the time of $t$ and $t+\Delta t$, and the nonlinear dynamic equations can be converted into a set of nonlinear algebraic equations, to be solved with Newton-Raphson or BFGS iterations during each time increment. The composite implicit time integration method proposed by K. J. Bathe is deduced for dynamic equations including nonlinear damping, in which the velocity is taken as the basic variable in this paper. Sdof system with fluid viscous dampers is taken as an example, and Fortran programs are developed according to above iteration procedure and Newmar $k$-$\beta $ algorithm based on BFGS iteration for the Sdof system. Results are compared with that of Adina, and the accuracy is valieated.