力学学报

ON THE EFFECTS OF HYDRODYNAMIC INTERACTION UPON THE WAVE FORCE ON VERTICAL PILE ARRAY OF SINGLE ROW 1)

A systematic study has been carried out on the effects of three-dimensional wave forces of vertical pile array, applying method of wave source distribution on arbitrary sectional contour of the piles The piles involved in computation reach up to 100 Some new properties of hydrodynamic interaction among piles are obtained It should be emphasized that the forces on piles shows continuous dependence when the piles number increases over a certain number When the number is very large, forces on the mi...

1998, 30(5): 513-520. doi: 10.6052/0459-1879-1998-5-1995-157

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CROSSFLOW INSTABILITY OF HIGH SPEED THREE DIMENSIONAL BOUNDARY LAYER 1)

There exist variety of instability in three dimensional boundary layer on swept wing, the cross-flow instability is dominant The flow over rotating cone is typical three dimensional boundary layer It has been shown that the experimental and theoretical results of rotating cone can be used to model cross flow instability of swept wing At high speeds, where even the basic flow calculations of swept wing are a problem, owe to it′s simple geometry, rotating cone become a suitable and valuable model to ...

1998, 30(5): 521-530. doi: 10.6052/0459-1879-1998-5-1995-158

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BOUSSINESQ TYPE EQUATIONS WITH FIRST ORDER OF NONLINEARITY AND FOURTH ORDER OF DISPERSION

In this paper, the Boussinesq-type equations with first-order O(α) of nonlinearity and fourth-order O(β 8) of dispersion is derived, in which, α=A/h 0 , β=h 0/L , A, L and h 0 is typical value of wave amplitude, wavelength and water depth By using the transforming velcity, the linear dispersion relation of our equations is consistent with fourth order pade approximation of the exact linear dispersion relation for Airy waves, this make the equations applicable to a wider rang...

1998, 30(5): 531-539. doi: 10.6052/0459-1879-1998-5-1995-159

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A MACROSCOPIC-MICROSCOPIC CONSTITUTIVE MODEL FOR FERROELECTRIC CERAMICS 1)

Ferroelectric ceramics are an important class of modern engineering materials and have received increasing attention for their distinctive properties and applications For example, they are used as modulators, deflectors, optical memories imaging devices and so on With the wider use of the materials and harsher requirement of their performances, the study of coupling electric and mechanical behavior has attracted great interests The main effort of this paper is to obtain the constitutive relation of fe...

1998, 30(5): 540-551. doi: 10.6052/0459-1879-1998-5-1995-160

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MICROSCOPIC ANALYSIS AND INVARIANT DESCRIPTION OF THE EFFECTIVE ELASTIC PROPERTIES OF DAMAGED SOLIDS ——A GENERAL THEORETIC MODEL ACCOUNTING FOR INTERACTION OF MICRO-DEFECTS

To estimate the effective elastic properties of damaged solids accounting for the interaction of micro-defects, quite a few schemes have been proposed, such as the self-consistent scheme (SCS) , differential scheme , generalised self-consistent scheme (GSCS) and Mori-Tanaka scheme (see also the review articles ) Although these schemes are quite covenient in application, they all are based on non-interacting scheme and some assumptions in accounting the effect of interaction of m...

1998, 30(5): 552-563. doi: 10.6052/0459-1879-1998-5-1995-161

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A STOCHASTIC MODEL FOR EVOLUTION OF COLLECTIVE SHORT-FATIGUE-CRACKS BASED ON LOCAL FIELD ANALYSIS 1)

It has been observed that, the evolution process of short fatigue cracks in some metallic materials presents collective damage characteristics The cumulation of the damage is produced by a number of short fatigue cracks The extent of damage is not dependent on a single crack, but on the whole response of total short cracks For this situation, we adopted the method of the balance of crack number density to describe such an evolutionary process The basic consideration of the model is that, at a certai...

1998, 30(5): 564-571. doi: 10.6052/0459-1879-1998-5-1995-162

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A METHOD FOR DETERMINING THE PERIODIC SOLUTION AND ITS STABILITY OF A DYNAMIC SYSTEM WITH LOCAL NONLINEARITIES 1)

The analysis of dynamic system with many degrees of freedom can be highly complex in the presence of strong nonlinearities, but it is important to understand the mechanisms of some phenomena The fundamental response of a nonlinear nonautonomous system is periodic, other motions, such as quasi-periodic, jump, period-doubling and chaotic motion, can bifurcate from periodic motion when a system parameter is changed Therefore, determining the periodic solution and its stability are required in such case ...

1998, 30(5): 572-579. doi: 10.6052/0459-1879-1998-5-1995-163

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WEAK FORMULATION OF MIXED STATE EQUATION AND BOUNDARY VALUE PROBLEM OF THEORY OF ELASTICITY 1)

Prof Tang clarified importance of mixed state equation of elasticity, and first gave Hamilton canonical equation by modifying Hellinger-Reissner variational principle At the same time author pointed out that the study of solution of mixed state equation has still not been well developed though it has a wide spread application prospect.This is because Hamilton equation must satisfy comples boundary condition in continuous medium mechanics which is its difficult point, Fan and Ding applied the mixed sta...

1998, 30(5): 580-586. doi: 10.6052/0459-1879-1998-5-1995-164

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DYNAMIC STRESS CONCENTRATIONS IN THIN PLATES WITH TWO CIRCULAR CUTOUTS 1)

The problem of elastic wave motion and dynamic stress concentration in infinite plates, because of its technical importance, has been the subject of many investigators A number of analytic methods were established for the investigation of stress concentrations, among which, the method developed by N I Muskhelishvili is prominent The problem of static stress concentrations on the edge of an arbitrary cutout can be solved by Muskhelishvili’s method Scattering of flexural waves and dynamic stress conc...

1998, 30(5): 587-596. doi: 10.6052/0459-1879-1998-5-1995-165

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SCATTERING AND DYNAMIC STRESS CONCENTRATION OF SH-WAVE BY INTERFACE CIRCULAR HOLE 1)

The present paper investigates the problem of SH-wave scattering and dynamic stress concentration by bi-material structure possessing cylindrical interface hole Green’s Function method is used here, which means a special essential solution suitable to the present problem must be constructed In terms of wave functions expansion method and Graf formula, we give the construction course for the special Green's function, and deduce it strictly from the essential solution for a perfect half space impacted by ...

1998, 30(5): 597-604. doi: 10.6052/0459-1879-1998-5-1995-166

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THEORETICAL AND EXPERIMENTAL ANALYSES OF THERMAL BUCKLING PROBLEMS OF LINER SHELLS ——THEORETICAL PART 1)

The buckling problem of liner shells is a major problem in reactor containment's design Because of the unilateral constraint and complex boundary condition, it is difficult to investigate post-buckling behavior of liner shells In this paper, the local liner shells are considered as the liner plates with the special initial imperfection forms Three liner shell models: four-point-supported liner shell, clamped liner shell and five-point-supported liner shell are proposed and investigated, respectively...

1998, 30(5): 605-614. doi: 10.6052/0459-1879-1998-5-1995-167

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INVESTIGATION OF THE GROUND VORTEX PHENOMENON DUE TO THE INTERACTION BETWEEN ROTOR'S WAKE AND THE GROUND 1)

The 3D incompressible Navier-Stokes equation was solved numerically to simulate the wake development and the ground vortex formation caused by a rotor in forward flight near the ground The characteristics of the ground vortex and the distribution of the induced velocity at rotor disc were studied and their influences by advance ratio were investigated To avoid directly simulate rotor blades with non-orthogonal curvilinear coordinates, momentum sources were added to the Navier-Stokes equation to imitat...

1998, 30(5): 615-620. doi: 10.6052/0459-1879-1998-5-1995-168

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AN EXACT SOLUTION FOR UNSTEADY SEEPAGE FLOW THROUGH FRACTAL RESERVOIR

There exists a amount of fractal structure in real geologic bodies, but classical pressure transient model are described by using homogeneous means and pseudo-homogeneous method In order to depict reservoir with fractal structure, fractal geometry has introduced the mechanics of fluids flow through porous media in some recent studies to build the pressure transient model of fluids flow in fractal Fracture network in the fractured rock system is described by using fractal For these models, however, th...

1998, 30(5): 621-627. doi: 10.6052/0459-1879-1998-5-1995-169

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THE INHERENT VIBRATION CHARACTERISTICS OF COMPOSITE LAMINATED BEAMS AND ELASTIC BEAMS 1)

In this Paper,according to Euler beam theory,Timoshenko beam theory and higher order beam theory,the inherent vibration characteristics of elastic beams are compared with that of composite laminated beams.The patterns of mode shapes are divided into two types,in one of the two types,the bending gradients are relatively more than the shear,in the other one,the shear gradients are more,and the latter type consists of several pure shear mode shapes.It is founded that many order frequencies and mode shapes rela...

1998, 30(5): 628-634. doi: 10.6052/0459-1879-1998-5-1995-170

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BOUNDARY ELEMENT ANALYSIS OF CRACK PROBLEMS IN FINITE 2-D MULTILAYERED COMPOSITE 1)

On the basis of Stiffness Matrix Method (SMM), a boundary element method to 2-D layered media (BEMLM) is developed in this paper to the crack analysis problems in layered elastic media By way of introducing additional interfaces together with its dislocation connecting conditions, SMM can be modified to include unit concentrated dislocations in its basic stiffness relations, which can be served as fundamental solutions to the layered media These fundamental solutions are given either in explicit form as...

1998, 30(5): 635-640. doi: 10.6052/0459-1879-1998-5-1995-171

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1998 Vol. 30, No. 5

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