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10 October 2004, Volume 26 Issue 5
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    Mechanics in engigeering
    2004, 26(5):  0-0.  doi:10.6052/1000-0992-2003-178
    Abstract ( 1437 )   PDF (125KB) ( 538 )  
    The constitutive equation of thixotropic fluid was of the Moore's model in this paper. The mechanical behaviors under oscillatory loading were discussed. The finite difference method was used. The results show that: 1) In the steady state, the parameter which described the internal structural state in the fluid was the periodic function of time; 2) The relation between the stress and the strain was a closed hysteretic cycle. These properties show that the thixotropic fluid is much more complex than the other non-Newtonian fluids.
    2004, 26(5):  0-0.  doi:10.6052/1000-0992-2003-210
    Abstract ( 1448 )   PDF (462KB) ( 634 )  
    The shear strength developed in a landslide is usually anisotropic and nonlinear. The anisotropy is primarily due to the process of sedimentation predominantly followed by one-dimensional consolidations. The nonlinearity could be attributed to ``interlocking'' or ``dilatancy'' of the material, which is generally dependent upon the stress level. In the paper, a new anisotropci function was been developed. An analytical method considering both anisotropy and nonlinearity of the failure envelopes is presented in the paper. The nonlinear failure envelopes can be obtained from routine triaxial tests. In a SPREADSHEET setup, the authors developed an approach that uses the Janbu's Generalized Procedure of Slice and incorporates anisotropic and nonlinear failure envelopes. In the analysis, an equivalent Mohr-Coulomb linear relation is obtained by drawing a tangent to the anisotropic and nonlinear envelope. An illustrative example is given to show the feasibility and numerical efficiency of the method.
    2004, 26(5):  0-0.  doi:10.6052/1000-0992-2003-213
    Abstract ( 1488 )   PDF (227KB) ( 652 )  
    By analyzing the property of frost heave in the aeolian soil, this paper proposes a fractal interpolation method to study the one-dimensional problem of frost heave in frozen soil. It is found that the frost heave curve has a good self-similarity, and the fractal theory can be used to describe the frost heave curve. The fractal dimension can represent the complexity and the non-linear property of frost heave curve, which is important for understanding the process of frost heave on the aeolian soil.
    2004, 26(5):  0-0.  doi:10.6052/1000-0992-2003-253
    Abstract ( 1584 )   PDF (368KB) ( 616 )  
    In this paper, a simple mathematical model of platform is established based on the principle of vibration reduction by using damping layers. The first vibration mode's damping ratio is obtained by a forced decoupling to two freedom degree mode. Also the relations between damping layer parameters and the structural damping ratio including the relative displacement control effect of structure and damping layers are studied. And the numerical simulation under wave force or earthquake force is carried out. The results show that using damping layers to reduce vibration is an effective measure. When the rigidity of damping layers is great, the structural vibration can be controlled effectively.
    2004, 26(5):  0-0.  doi:10.6052/1000-0992-2003-258
    Abstract ( 1054 )   PDF (182KB) ( 583 )  
    In this paper, a simple method of searching for feasible directions is put forward. This method has a clear geometric meaning, is easy to understand, solve the problem that and can the Nonlinear Constrained Optimization with Zoutendijk Method of Feasible Directions may sometimes fail.
    Interesting mechanics story
    2004, 26(5):  0-0.  doi:10.6052/1000-0992-2003-261
    Abstract ( 1577 )   PDF (329KB) ( 459 )  
    A mathematical model of shot throw process is put forward. The shot throw process is optimized by means of Genetic Algorithm. Various optimal parameters and the maximum throw distance are obtained. Moreover, the influential factors in the shot throw process are analyzed and compared. Thus, a scientific training plan can be worked out based on present study.
    Mechanics in engigeering
    2004, 26(5):  0-0.  doi:10.6052/1000-0992-2003-262
    Abstract ( 1286 )   PDF (400KB) ( 458 )  
    In this paper a non-conforming finite element eigen-analysis method based on displacement is developed to study the singular stress and displacement fields surrounding a wedge tip. The formula is different from the existing finite element eigen-analysis methods for asymptotic fields near the crack tip. The element is non-conforming one, and the singular transformation technique is not used in the assumption of displacement fields surrounding the wedge tip. This paper presents some illustrative evaluating examples of asymptotic singular fields surrounding arbitrary wedges and junction tips. All calculations show that the present method needs fewer elements, yields more accurate results, and can be applied more extensively.
    2004, 26(5):  0-0.  doi:10.6052/1000-0879-2003-263
    Abstract ( 1347 )   PDF (310KB) ( 649 )  
    This paper presents an equivalent load method for estimation of fatigue crack initiation life under spectrum loading. A weight factor and a coefficient of correction are added to the formula of root mean square of variable-amplitude-loading, respectively, to reflect influence of different loading range and mean stress upon variable-amplitude-fatigue life, and then the corresponding constant-amplitude-loading instead of the variable-amplitude-loading is used to estimate fatigue crack initiation life under spectrum loading. The method is easy to use as it only depends on constant-amplitude $S$-$N$ curve and uniaxial mechanical property of the material and it does not contain any undetermined parameters. The results of fifteen sets of random fatigue test data under three spectrum types for two materials are compared with three parallel methods. Miner rule, modified Miner rule and Root-Mean-Square method, and the average life-prediction accuracy of the method is improved, respectively, by 99.1, 24.6 and 50.0 per cent.
    2004, 26(5):  0-0.  doi:10.6052/1000-0992-2003-294
    Abstract ( 1210 )   PDF (307KB) ( 516 )  
    A telescopic penetrator composed of long rod and long tube is designed to solve the problems caused by slender projectile (large length / diameter ratio). By means of experiments and numerical simulations, the performances of long tube and long rod with the same mass and length in the same material normally against semi-infinite RHA(rolled homogeneous armor) are compared. The penetration patterns of the long tube and long rod are described. The relationships of velocity vs. time and mass vs. time for two kinds of penetrators are also obtained. Both the experimental and the numerical results indicate that the decreasing rates of long tubular velocity and mass are greater than that of long rod in the penetration course. Therefore, the penetration performance of the long tube is inferior to that of the long rod.
    2004, 26(5):  0-0.  doi:10.6052/1000-0992-2003-299
    Abstract ( 1270 )   PDF (311KB) ( 568 )  
    Large-scale amplitude liquid sloshing in a rectangular open tank under a pitching excitation is studied in this paper. Firstly, the kinematics of the ALE (arbitrary Lagrange-Euler) description is introduced and the Navier-Stokes equations of fluid are revised in the ALE form. The numerical discreted equations of fractional step finite element method are developed by using Galerkin weighted residual method. The numerical simulation of large amplitude sloshing of the liquid in a rectangular tank is carried out. The computed water elevation history is obtained. Through comparing the numerical results with experiments, the efficiency of fractional step ALE finite element method is confirmed.
    2004, 26(5):  0-0.  doi:10.6052/1000-0992-2003-328
    Abstract ( 1000 )   PDF (234KB) ( 516 )  
    The existing engineering materials for civil protection are challenged with the appearance of new penetrating projectiles, and the further development is an important factor in a possible war under high technology. This paper deals with the compressive, bending and tensile characteristics of samples made of a new type of steel-wire-net reinforced concrete. Comparing them with several conventional compound engineering materials of civil protection, it is found that the steel-wire-net reinforced concrete is better than the others and it has a good prospective applications.
    2004, 26(5):  0-0.  doi:10.6052/1000-0992-2003-395
    Abstract ( 2023 )   PDF (223KB) ( 601 )  
    With Airy stress function, a plane elasticity problem can be simplified to solve a biharmonic function equation. In this paper, we introduce a lemma concerning the biharmonic function. In order to prove the lemma, we present two different methods from two different angles in the first section. On the basis of the lemma, a direct method for constructing Airy stress functions in polar coordinates is derived. Finally, some examples are provided to illustrate how the direct method works in some classic plane cases and what we can benefit from this direct method for the stress function construction. These application examples indicate that the direct method derived in this paper simplifies the process of constructing the Airy function in specific plane problems.
    2004, 26(5):  0-0.  doi:10.6052/1000-0992-2003-447
    Abstract ( 1378 )   PDF (335KB) ( 572 )  
    The correlation between of the effective modulus and the effective electrical conductivity for planar materials with microcracks are investigated by numerical and Mori-Tanaka's theoretical methods. The relations derived from analytical Mori-Tanaka's method for both randomly oriented and parallel microcracks are found to be in excellent agreement with the numerical results.
    2004, 26(5):  0-0.  doi:10.6052/1000-0992-2003-482
    Abstract ( 1113 )   PDF (353KB) ( 656 )  
    The crack in concrete block wall is a new problem for the new wall materials. At First, based on engineering investigations, causes and positions of cracks in concrete block wall are studied, and temperature crack and dry shrink crack are two main kinds of cracks. Secondly, the temperature crack stress is calculated by temperature difference in an existing building. Thirdly, the mechanism of dry shrink crack is expounded by Kelvin-equation and the dry shrink crack stress are also analyzed. In the end, causes of cracks in concrete block wall are explained.