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2001年 第22卷 第8期    刊出日期：2001-08-18

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论文

ORIENTATION DISTRIBUTION FUNCTIONS FOR MICROSTRUCTURES OF HETEROGENEOUS MATERIALS (Ⅰ) ─ DIRECTIONAL DISTRIBUTION FUNCTIONS AND IRREDUCIBLE TENSORS

郑泉水;邹文楠

2001, 22(8):  865-884. 

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In this two-part paper, a thorough investigation is made on Fourier expansions with irreducible tensorial coefficients for orientation distribution functions (ODFs) and crystal orientation distribution functions (CODFs), which are scalar functions defined on the unit sphere and the rotation group, respectively. Recently it has been becoming clearer and clearer that concepts of ODF and CODF play a dominant role in various micromechanically-based approaches to mechanical and physical properties of heterogeneous materials. The theory of group representations shows that a square integrable ODF can be expanded as an absolutely convergent Fourier series of spherical harmonics and these spherical harmonics can further be expressed in terms of irreducible tensors. The fundamental importance of such irreducible tensorial coefficients is that they characterize the macroscopic or overall effect of the orientation distribution of the size, shape, phase, position of the material constitutions and defects. In Part (Ⅰ), the investigation about the irreducible tensorial Fourier expansions of ODFs defined on the N-dimensional (N-D) unit sphere is carried out. Attention is particularly paid to constructing simple expressions for 2- and 3-D irreducible tensors of any orders in accordance with the convenience of arriving at their restricted forms imposed by various point-group (the synonym of subgroup of the full orthogonal group) symmetries. In the continued work -Part (Ⅱ), the explicit expression for the irreducible tensorial expansions of CODFs is established. The restricted forms of irreducible tensors and irreducible tensorial Fourier expansions of ODFs and CODFs imposed by various point-group symmetries are derived.

ORIENTATION DISTRIBUTION FUNCTIONS FOR MICROSTRUCTURES OF HETEROGENEOUS MATERIALS (Ⅱ)──CRYSTAL DISTRIBUTION FUNCTIONS AND IRREDUCIBLE TENSORS RESTRICTED BY VARIOUS MATERIAL SYMMETRIES

郑泉水;傅依斌

2001, 22(8):  885-903. 

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The explicit representations for tensorial Fourier expansion of 3-D crystal orientation distribution functions (CODFs) are established. In comparison with that the coefficients in the mth term of the Fourier expansion of a 3-D ODF make up just a single irreducible mth-order tensor, the coefficients in the mth term of the Fourier expansion of a 3-D CODF constitute generally so many as 2m+1 irreducible mth-order tensors. Therefore, the restricted forms of tensorial Fourier expansions of 3-D CODFs imposed by various micro- and macro-scopic symmetries are further established, and it is shown that in most cases of symmetry the restricted forms of tensorial Fourier expansions of 3-D CODFs contain remarkably reduced numbers of mth-order irreducible tensors than the number 2m+1 . These results are based on the restricted forms of irreducible tensors imposed by various point-group symmetries, which are also thoroughly investigated in the present part in both 2- and 3-D spaces.

EFFECTS OF SURFACE WAVES AND MARINE SOIL PARAMETERS ON SEABED STABILITY

林缅;李家春

2001, 22(8):  904-916. 

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Based on the Yamamoto’s soil model by considering the Coulomb friction effects, the wave-induced seabed instability has been investigated. An analytical solution is derived for soil response of a finite depth seabed under surface water wave. The effects of wave parameters and soil characteristics on the seabed instability are addressed for three types of soil. Finally, the roles of Coulomb friction stability are then analyzed as well.

1:2 INTERNAL RESONANCE OF COUPLED DYNAMIC SYSTEM WITH QUADRATIC AND CUBIC NONLINEARITIES

陈予恕;杨彩霞;吴志强;陈芳启

2001, 22(8):  917-924. 

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The 1:2 internal resonance of coupled dynamic system with quadratic and cubic nonlinearities is studied. The normal forms of this system in 1:2 internal resonance were derived by using the direct method of normal form. In the normal forms, quadratic and cubic nonlinearities were remained. Based on a new convenient transformation technique, the 4-dimension bifurcation equations were reduced to 3-dimension. A bifurcation equation with one-dimension was obtained. Then the bifurcation behaviors of a universal unfolding were studied by using the singularity theory. The method of this paper can be applied to analyze the bifurcation behavior in strong internal resonance on 4-dimension center manifolds.

STUDY ON EXACT ANALYTICAL SOLUTIONS FOR TWO SYSTEMS OF NONLINEAR EVOLUTION EQUATIONS

闫振亚;张鸿庆

2001, 22(8):  925-934. 

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The homogeneous balance method was improved and applied to two systems of nonlinear evolution equations. As a result, several families of exact analytic solutions are derived by some new ansatzs. These solutions contain Wang’s and Zhang’s results and other new types of analytical solutions, such as rational fraction solutions and periodic solutions. The way can also be applied to solve more nonlinear partial differential equations.

AN ACCURATE SOLUTION OF THE POISSON EQUATION BY THE FINITE DIFFERENCE-CHEBYSHEV-TAU METHOD

Hani I. Siyyam

2001, 22(8):  935-939. 

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A new finite difference-Chebyshev-Tau method for the solution of the two-dimensional Poisson equation is presented. Some of the numerical results are also presented which indicate that the method is satisfactory and compatible to other methods.

STRETCH AND ROTATION OF A SUSPENDED CABLE SUBJECT TO TRANSVERSE FLUID EXCITATION

金栋平;胡海岩

2001, 22(8):  940-946. 

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On the basis of analysis of the fluid drag acting on a suspended cable subjected to transverse fluid excitation, an expression is established for the fluid forces applied on the cable. By using a coordinate transform, the equations of motion of the cable are simplified into those in terms of the stretch and rotation coordinates. In the case of small ratio of sag-to-span, a study is made on the fluid-induced vibration behavior of the cable, including the critical fluid flow speed, the stability of equilibrium position, as well as the influences of gravitational parameter on the cable dynamics.

EQUIVALENT LINEARIZATION METHOD BASED ON ENERGY-TO-cTH-POWER DIFFERENCE CRITERION IN NON- LINEAR STOCHASTIC VIBRATION ANALYSIS OF MULTI-DEGREE-OF-FREEDOM SYSTEMS

王国砚;戴民

2001, 22(8):  947-955. 

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Basic equations of energy-to-cth-power difference criterion were derived for multi-degree-of-freedom(MDOF) systems subjected to stationary Gaussian excitations with non-zero mean. Modal transform technique was used in order to reduce unknowns. Main computational formulae were presented and suggested values of c were given. Numerical results show that the method of this paper prevails over equation difference criterion both in accuracy and in simplicity.

THE DISCRETE MODELS ON A FRICTIONAL SINGLE DEGREE OF FREEDOM SYSTEM

冯奇;张相庭

2001, 22(8):  956-964. 

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Two stochastic models on simple random system with friction were developed. One of them was a discrete model by a two-dimensional mean map applied to describe random stick-slip motion. The numerical examples show that external noise can reduce the complexity of the system behavior. Secondly, a probability model described was established with coexistence of stick-slip and slip motions. The numerical results point out that this model possesses pure stochastic behavior.

RESEARCH ON EQUIVALENT PROCESSES OF ROCK MASS PARAMETERS WITH ANCHOR PILES

陈洪凯;唐红梅;王蓉;唐芬;王凯;袁建议

2001, 22(8):  965-971. 

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Using normal and shear rigid coefficients of intact rock and fracture plane, rigidly normal, shear equivalent rigid coefficients of fissure rock mass are conducted. On the basis of hypotheses of small displacement of rock mass, principle of superposition, irrelevance of strength parameters C and φ and Coulomb theory, formulas to calculate equivalent strength parameters C and φ of equivalent continuous mass from fissured rock mass with anchor piles are given. The achievement is extremely valuable in integral stability analysis of the rock mass slope and important in promoting the research of the rock mass’s constitutive relation.

SINGULAR CHARACTERISTICS OF NONLINEAR NORMAL MODES IN A TWO DEGREES OF FREEDOM ASYMMETRIC SYSTEMS WITH CUBIC NONLINEARITIES

徐鉴;陆启韶;黄克累

2001, 22(8):  972-982. 

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Nonlinear normal modes in a two degrees of freedom asymmetric system with cubic nonlinearities as singularity occurs in the system are studied, based on the invariant space in nonlinear normal modes and perturbation technique. Emphasis is placed on singular characteristics as the linear coupling between subsystems degenerated. For non-resonances, it is analytically presented that a single-mode motion and localization of vibrations occur in the system, and the degree of localization relates not only to the coupling stiffness between oscillators, but also to the asymmetric parameter. The parametric threshold value of localization is analytically given. For 1:1 resonance, there exist bifurcations of normal modes with nonlinearly coupling stiffness and asymmetric parameter varying. The bifurcating set on the parameter and bifurcating curves of normal modes are obtained.

THE DECAY OF SWIRLING FLOWS IN A TYPE OF CROSS-SECTION-VARYING PIPES

熊鳌魁;魏庆鼎

2001, 22(8):  983-988. 

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The decay of weakly swirling flows in a type of cross-section-varying pipes was discussed analytically. For laminar swirling flow, the feature of exponential decay was demonstrated. For turbulent swirling flow, in spite of the decay of circulation flux, a necessary condition for local circulation to amplify along downstream was obtained under the Boussinesq’s hypothesis.