力学学报

NUMERICAL SIMULATION OF 3-D WATER ENTRY OF BLUNT CYLINDER WITH A VENTILATEDCAVITY

A method is developed in which the time-stepping algorithm and the boundary integral equation method are employed to calculate vertical and oblique water entry of a blunt cylinder, which is a 3-d, nonsteady, incompressible and inviscid fluid flow problem with nonlinear free surface and fluid-body interaction. The free surface is described in terms of La-grangian coordinates and the body surface is described in terms of Eulerian coordinates fixed in the body. Implicit schemes of second-order precision time-d...

1990, 22(2): 129-138. doi: 10.6052/0459-1879-1990-2-1995-923

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FISSION OF INTERFACIAL SOLITARY WAVES IN A TWO-LAYER FLUID SYSTEM

In this paper, the fission of interfacial solitary waves in a two-layer fluid system is investigated. It is found that the density ratio of the upper and lower fluids has no effect on the fission conditions of forming two solitary waves. It means that the fission may occur provided that solitary wave travels from deeper fluid to shallower fluid. But the fission conditions of forming more than two solitary waves are related to the density ratio and upstream depth ratio of the upper and lower fluids.

1990, 22(2): 139-145. doi: 10.6052/0459-1879-1990-2-1995-924

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ANALYSIS OF THE 3-D TURBULENT FLOW FIELD FOR AN OFF-AXIS CONFINED JET

Using primary variables and staggered, the 3-D turbulent flow field for an off-axis confined jet was computated by k-ε model of turbulent flow. Computing results on comparison with measurements are satisfactory. The computing results have provided much information on the flow pattern and given a basic understanding of the mechanism of stable combustion for pre-cornbustion chambers with an off-axis confined jet. A detail analysis shows that one of the major characteristics of the flow field is the large twis...

1990, 22(2): 146-153. doi: 10.6052/0459-1879-1990-2-1995-925

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INCIPIENT FRACTURE OF COAL UNDER ONE DIMENSIONAL GAS SEEPAGE

The fracture of coal under one dimensional gas seepage is investigated. The experiments show that the incipient fracture of coal takes the shape of a spherical crown; the critical gas overpressure is dependent on the unloading condition, the strength, radius, confining pressure, length of the sample, and independent of the characteristics of gas adsorption. Numerical analysis demonstrates that the fracture belongs to tensile mode; the increase of unloading rate, decrease of confining pressure and increase o...

1990, 22(2): 154-162. doi: 10.6052/0459-1879-1990-2-1995-926

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A COMPLEX VARIABLE BOUNDARY ELEMENT METHOD FOR SANDWICH PLATES

本文用全纯函数表示微分方程△f(x,y)-λ(~2)f(x,y)=0的一般解,粮据全纯函数的Bekya积分表示法,建立了复数域内的边界积分方程并针对各种边界条件下Reissner型夹层板、Hoff型夹层板进行了数值求解。

1990, 22(2): 163-170. doi: 10.6052/0459-1879-1990-2-1995-927

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THE PROBLEM OF BLOCK DIAGONALIZATION OF A COMPLEX ORTHOGONAL MATRIX AND ITS APPLICATION TO ISING MODEL PHASE TRANSITION

本文给出(2n×2n)复正交矩阵正交相似于(2×2)正交矩阵直接和的充分必要条件,作为实际例子,并讨论它对二维Ising模型相变问题的应用。

1990, 22(2): 171-175. doi: 10.6052/0459-1879-1990-2-1995-928

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SOLVING THE PROBLEMS OF SHALLOW SPHERICAL SHELLDUE TO LINELOADS AND LINE MOMENTS BYGREEN'S FUNCTION

This paper derives the solutions of shallow spherical shell due to line loads or line moments by means of construcing Green's function from the homogeneous differential equations of shallow shell whose solution is in a complex from, Integrating the results, We shall obtain the solution of shallow sphercal shell due to axisymmetrical loads distributed along the shell Following this, the solutions of circular plate and the cylindrical shell are obtained by using this paper's method and the results are suitabl...

1990, 22(2): 176-184. doi: 10.6052/0459-1879-1990-2-1995-929

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ON THE CLASSIC NONHOLONOMIC DYNAMICS

For first-order nonlinear nonholonomic systems, the present paper proves that the d-δ operations are commutative and derives the equation of motion, without making use of the additional Appell-Chetaev condition. This equation of motion ,coincides with the equation of "Vacco dynamics".

1990, 22(2): 185-190. doi: 10.6052/0459-1879-1990-2-1995-930

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RESONANT INTERACTIONS OF INSTABILITY WAVE AND EDDY-PAIRING PHENOMENA IN A TWO-DIMENSIONAL MIXING LAYER

Nonlinear growth and resonant interaction in a two-dimensional mixing layer are observed, to analyse their effects on vortex-pairings and transition

1990, 22(2): 191-194. doi: 10.6052/0459-1879-1990-2-1995-931

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BOUNDARY LAYER EQUATIONS IN NONINERTIAL REFERENCE FRAME

The first-order and second-order boundary layer equations in noninertial reference frame is derived using the technique of matched asymptotic expansion. The first-order boundary layer equation is identical to the classical boundary layer equation as the pressure term is eliminated; the noninertial effect is of second-order.

1990, 22(2): 195-199. doi: 10.6052/0459-1879-1990-2-1995-932

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FORMULATION FOR THE LARGE DEFORMATION CURVED SHELL ELEMENTS

This paper presents large deformation curved shell elements. The displacement field at a point P(ξ, η, ζ) within an element is discribed, using the vectors Ut and the Ft. The Ui is the displacement vector of node i in mid-surface of shell, the vector F4 is the displacement vector of the end of the unite normal vector at node i. The formulation of the elements is general and simpler than existing ones, and unlimited in the load or displacement increments

1990, 22(2): 200-205. doi: 10.6052/0459-1879-1990-2-1995-933

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ASYMPTOTIC METHOD OF STRONGLY NONLINEAR VIBRATION SYSTEMS

The method in [1] is generalized and applied to the solutions of a wide class of strongly nonlinear vibration systems in this paper. The easier formulas are introduced for the approximate qualitative analysis and quantitative calculation. As an example, we have studied the behavior of the revised van der Pol vibrator. At last, through displaying the results of the numerical Poincare map, the efficiency of the method presented in this paper has been evidenced from the approximate qualitative analysis and qua...

1990, 22(2): 206-212. doi: 10.6052/0459-1879-1990-2-1995-934

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SMOOTH RIDGE MODEL OF GENERALIZED TWIN SHEAR STRESS CRITERION

Based on the twin shear stress theory, a new smooth ridge corner model of generalized twin shear stress criterion is proposed in this paper. This new smooth ridge model gives a close estimate of experimental data, reflects the influence of intermediate principal stress and the required characteristics concerning smoothness, convexity, symmetry, etc. The results of researches show that the three parameter criterion of William-Warnke and some other criteria are not a smooth Mohr-Coulomb surface, but a smooth ...

1990, 22(2): 213-216. doi: 10.6052/0459-1879-1990-2-1995-935

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DYNAMIC RESPONSES OF AXISYMMETIUCAL PROBLEMS FOR A VISCOELASTIC PLATE ON A VISCOELASTICFOUNDATION

In the present paper, the dynamic problem of a thin viscoelastic circular plate under axisymmetrical load resting on a viscoelastic half-space foundation is discussed. This problem is rnduced to a Fredholm integral equation of the first kind in the Laplace transformation space and solved by numerical procedures. The results of the problem is obtained by taking the numericai Laplace transform inversion.

1990, 22(2): 217-222. doi: 10.6052/0459-1879-1990-2-1995-936

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THE TORSIONAL ANALYTIC SOLUTION OF PRISMATICCYLINDERS IN THE POWER EXPONENTIALHARDENING MODEL

A methed utilizing pseudo-stress function to solve torsional problems of prismatic cylinders in the power exponential hardening model is proposed. By the method, the torsional equations of cylinders possessed sections of arbitrary shape or circular sections of variable diameter, could be solved just like that of linear-elastic cylinders, or solved by directly using the elastic solutions which have been known. Examples of an elliptical section shaft and a circular cylinder possessed a globular cavity in the ...

1990, 22(2): 223-228. doi: 10.6052/0459-1879-1990-2-1995-937

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ELASTIC-PLASTIC FIELDS AT A CRACK TIP IN PERFECTLY PLASTIC MEDIUM

Based on the basic equations and continuity conditions, the configurations of the near-tip fields for a plane stress tensile crack in a perfectly plastic material have been studied in details in this paper. It is shown that the general solution of the near-tip fields contains, an elastic region, and the stresses are continuous. Specially, it is reduced to the solution which, is given by Hutchinson (1968) as the elastic region degenerates into an elastic kernel.

1990, 22(2): 229-235. doi: 10.6052/0459-1879-1990-2-1995-938

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LIMIT ANALYSIS OF SHALLOW SHELLS UNDER ARBITRARY NORMAL LOADS

The variational formulations for computing the limit load of shallow shellsunder arbitrary normal load by means of duality-variational principle are presented in this paper. The numerical analysis for an example is carried out by finite element method and iteration method, which shows that the variational formulations are effective for the limit analysis of shallow shells. Hence it might be widely used to estimate the ultimate capacity of structures with shallow shell form, such as side plate of ship, bulkh...

1990, 22(2): 236-240. doi: 10.6052/0459-1879-1990-2-1995-939

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样条积分方程法分析弹塑性板弯曲

In view of deformation theory and Mises criterion, we use the fictitious loads formulation to obtain the elastoplastic bending equations of Reissner's plates and Kirchhoff's plates, respectively, and solve them by the spline integral equation method just as the elasto-pro-blems. The equivalence of these two plate-models under polygonal simply-supported condition and axisymmetric bending is also studied here. The satisfactory results can be obtained even with a few of degrees of freedom.

1990, 22(2): 241-245. doi: 10.6052/0459-1879-1990-2-1995-940

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A GENERAL SOLUTION FOR ORTHOTROPIC TOROIDAL SHELLS SUBJECTED TO AXISYMMETRIC LOADS

So far the research into the problems involved in homogeneous toroidal shells has been done so well that we think the problems have been solved. The results presented in this paper are relevant to toroidal shells made of orthotropic materials. They can be used in calculations of arbitrarily shaped toroidal shells and in simplified analysis of bellows. The method presented here, which is based on the theory of thin elastic shells, is used to axisymmetrically orthotropic toroidal shells. A second-order differ...

1990, 22(2): 246-251. doi: 10.6052/0459-1879-1990-2-1995-941

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ON THE FORMULAE OF ENERGY RELEASE UNDER GENERAL BOUNDARY CONDITIONS

This paper discusses the energy release of crack and cut in propagation under general boundary conditions and points out that the use of force potential can result in an error under these conditions. Then, from the global energy integration with no additional hypothesis, formulae by Griffith and by Sih and Liebowitz are proved strictly and directly. Therefore, it is proved that Eftis in ref. [2] refuted Griffith formula and returned to Griffith former formula in 1921 wrongly. And it is shown that the not ve...

1990, 22(2): 252-256. doi: 10.6052/0459-1879-1990-2-1995-942

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1990 Vol. 22, No. 2

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