力学学报

SIMULATION OF SWIRLING GAS PARTICLE FLOWS USING THE UNIFIED SECOND ORDER MOMENT MODEL 1)

Numerical simulation of swirling gas particle flows are carried out for the development of innovative cyclone separators, hydrocyclones, cyclone furnaces and swirl burners in our laboratory, using two fluid models. The key problem in two fluid models is the two phase turbulence model. The two phase turbulence in swirling flows is obviously anisotropic. The isotropic k ε k p model proposed by us can give reasonable two phase velocity fields in case of swirl number s =0 47, but cannot predict ...

1998, 30(4): 385-390. doi: 10.6052/0459-1879-1998-4-1995-141

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RESEARCH ON NON OSCILLATION, PARAMETER FREE FINITE ELEMENT SCHEME 1)

A finite element modified equation is estabished by using the finite element Taylor weak statement for hyperbolic conservation laws and various finite element numerical schemes are obtained by means of reasonably choosing the coefficient of the expansional expression. The relations between the coefficients of the differential terms of the finite element modified equation and stability, dissipation error and dispersion error of finite element schemes are investigated by means of stability analysis. These...

1998, 30(4): 391-403. doi: 10.6052/0459-1879-1998-4-1995-142

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THE CORRELATIVE REFERENCE MODEL AND THE MOLECULAR DYNAMICS SIMULATION OF THE DISLOCATION EMISSION

A correlative reference model for the computer simulation of the molecular dynamics is proposed in this paper. Supposing that there is an infinite elastic continuum with a single edge crack, its elastic constants, such as E, G,v , are the same as those of the simulated crystal. There is a correlation between the realistic sample and the reference model. Two requirements must be satisfied in the simulation, see Figs. 1a and 1b. (1) The atomic displacement in the region 2 in Fig.1a is determined by that o...

1998, 30(4): 404-413. doi: 10.6052/0459-1879-1998-4-1995-143

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AbstractBIFURCATION CAUSED BY THE STRESS WAVE IN COLUMNS 1)

The elastic or plastic dynamic buckling of columns under different kinds of axial impact loading has been studied for a long time. When studying this problem, most researchers usually assume that the column has some imperfections and analyze the developing course of this imperfection under impact load by the amplification function method. Although the method is very practical in engineering, it has some defects. On the one hand, the bifurcation problem is analyzed like a strength or stiffness one, so its e...

1998, 30(4): 414-422. doi: 10.6052/0459-1879-1998-4-1995-144

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CALCULATING NORMAL FORMS FOR NONSEMI SIMPLE BIFURCATIONS

This paper presents a new scheme of calculating the Normal forms of a set of nonlinear ordinary differential equations when a nonsemi simple bifurcation occurs, with only the eigenvalues of zero real parts of the linearized differential equations given. It is well known that the classical matrix method enables one to establish the algebraic equations that govern the coefficients in the Normal form of a set of ordinary differential equations. However, it offers neither general technique of reducing the max...

1998, 30(4): 423-433. doi: 10.6052/0459-1879-1998-4-1995-145

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A PRINCIPAL TYPED TRACTION BIEM FOR 3D CRACK PROBLEMS 1)

This paper presents a principal typed traction boundary integral equation method for three dimensional static and dynamic crack problems. Based on a set of traction boundary integral equations for elasto statics/dynamics derived from conservation laws of elasticity, which contain no hyper singular integral, corresponding equations for crack(s) embedded in an infinite medium and in a free surfaced finite body are formulated. Because no hyper singular integral encountered, there are no distinct difficul...

1998, 30(4): 434-441. doi: 10.6052/0459-1879-1998-4-1995-146

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THE DEFORMATION BEHAVIOR AND MICROSTRUCTURE EFFECT OF 2124 Al/SiC p UNDER IMPACT LOADING 1)

An investigation has been carried out on the deformation and microstructure effect of 2124 Al/SiC p composites under dynamic compression. The experimental materials are 2124 Al alloy and its composites, reinforced with SiC particles of 3μm, 13μm and 37μm, the volume fractions of SiC particles is about 17%. One of the experimental results is that, in these composites, their flow stress varies with the SiC particle size under same loading condition, =21001/s. The further analysis show that the flow stres...

1998, 30(4): 442-448. doi: 10.6052/0459-1879-1998-4-1995-147

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THE DESIGN AND OPTIMIZATION OF SHAPE MEMORY ALLOY ACTUATOR 1)

In this paper , the constitutive equations of SMA material proposed by Brision is adopted to investigate the dynamic response of shape memory alloy actuator under three types of heat transferring models: resistive heating with free convection cooling , resistive heating with forced convection cooling and the semiconductor “heat pump” modules. Meanwhile, the loading influences on the period of completing transformation are analyzed. The results indicate that heat transferring types will yield larger influen...

1998, 30(4): 449-460. doi: 10.6052/0459-1879-1998-4-1995-148

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A LOCAL ADAPTIVE GRID REFINEMENT METHOD OF TETRAHEDRON ELEMENT AND ITS APPLICATION TO THE FINITE ELEMENT METHOD

A local refinement method of three dimensional tetrahedron elements is presented in this paper. It is the extension of Lo ¨hner's mesh enrichment method for two dimensional triangular grid. Three steps are included in the whole process. First, a certain number of elements which need enrichment is defined according to the remeshing parameters. Those elements are called initial enrichment elements, which will be subdivided into eight small tetrahedra by introducing the midpoints of each side as new verte...

1998, 30(4): 461-467. doi: 10.6052/0459-1879-1998-4-1995-149

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LIE SYMMETRIES AND CONSERVED QUANTITIES OF NONHOLONOMIC SYSTEMS OF NON CHETAEV'S TYPE 1)

There are two kinds of modern methods in finding conservation laws. One is the Noether method which is based on the invariance of the Hamilton's action under the infinitesimal transformations, the other one is the Lie method which is based on the invariance of the differential equations under infinitesimal transformations. In mathematics, the symmetry methods in the theory of differential equations have made great progress in recent years. In mechanics, the research on Lie symmetries and conservation l...

1998, 30(4): 468-474. doi: 10.6052/0459-1879-1998-4-1995-150

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MODELING ON TURBULENCE IN MOLD FILLING USING ALGEBRAIC STRESS MODEL

The mold filling is one of key processes in material forming engineering. Many defects, such as air and inclusions entrapment, splash and so on, may occur if unsuitable mold filling is designed. The numerical simulation can simulate the real mold filling, and can provide insight into the flow patterns. The calculated results are important basis of the control of mold filling. Generally speaking, the mold filling with relatively high speed is turbulent fluid flow in most of cases, and anisotropic turbulen...

1998, 30(4): 475-481. doi: 10.6052/0459-1879-1998-4-1995-151

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AN EXPERIMENTAL INVESTIGATION ON INTERACTION OF A COMPRESSIBLE STREAMWISE VORTEX WITH A MOVING SHOCK WAVE 1)

An experiment on the interaction of a compressible streamwise vortex with a moving shock wave has been conducted in a shock tube with 94 mm×94 mm square cross section. A finite span wing was mounted in upstream of the test section. When a shock wave passed through the wing, a streamwise vortex was induced from the tip of the wing by the supersonic flow behind the shock wave. After the incident shock wave reflected from the end of the shock tube, the interaction of the reflected shock wave with the strea...

1998, 30(4): 482-487. doi: 10.6052/0459-1879-1998-4-1995-152

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VOLUME INTEGRAL EQUATION METHOD FOR SCATTERING PROBLEMS OF INHOMOGENEOUS MEDIA

It is an effective technique to treat inhomogeneous media as perturbations on the back ground of homogeneous media and to treat the perturbations as equivalent source. Two forms of corresponding integral equations are: 1) boundary integral equation with both boundary integral items for boundary displacement and volume integral items for displacement in wavefield; 2) volume integral equation including integral only for inhomogeneous bounded region. Much work has been done in this field. Interpreting inhom...

1998, 30(4): 488-494. doi: 10.6052/0459-1879-1998-4-1995-153

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ON THE RELATION BETWEEN THE M INTEGRAL AND THE BUECKNER WORK CONJUGATE INTEGRAL

The path independent integrals in the field of fracture mechanics have received considerable attention in recent years since Rice proposed the well known J integral in 1968. On the one hand, Herrmann and Herrmann (1981) pointed out that the integrals L and M provide a more natural description of energy release rate associated with plane cracks than the integrals J 1(≡J) and J 2 . On the other hand, Chen (1985), Chen and Hasebe (1994,1995) found that there is a simple and inherent relati...

1998, 30(4): 495-502. doi: 10.6052/0459-1879-1998-4-1995-154

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PERTURBATION METHOD OF NEAR DEFECTIVE SYSTEMS

The matrix perturbation theory for the distinct eigenvalues of the real symmetric matrix was well developed. If some of eigenvalues are multiple, the nature of the problem changes and difficulties arise. To avoid such difficulties, it is usually assumed that the system has a set of complete eigenvectors to span the space, i.e. the system is non defective. However, in actual engineering problems, such as general damping systems, flutter analysis of aero elasticity, and so on, the defective system, that do no...

1998, 30(4): 503-507. doi: 10.6052/0459-1879-1998-4-1995-155

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1998, 30(4): 508-512. doi: 10.6052/0459-1879-1998-4-1995-156

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1998 Vol. 30, No. 4

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