力学学报

EXPERIMENTAL INVESTIGATION OF TWO TURBULENT WING BODY JUNCTIONS AND WAKES FLOW

The experimental studies on two wing body junctions and wakes were carried out in a low turbulence level wind tunnel. Intensive measurements of various flow parameters in the flow field around the wing body junction,such as the distribution of the pressure along the airfoil and plate wall,the mean and fluctuation velocity, as well as the turbulence energy, u′v′ and u′w′ etc., are presented. Through comparation of two junction flow fields, some features are analysed.

1996, 28(4): 385-391. doi: 10.6052/0459-1879-1996-4-1995-346

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STUDY ON HIGH ACCURACY BOUNDARY ALGORITHMS

Based on the Ringleb Flow, for which there exists analytical solution, a numerical tool named Ringleb Machine is developed to test the accuracy of algorithms of CFD. The affection that boundary procession exerts on the solution of the field is discussed. Result of our calculation shows that:1) Accompanying with a 2nd order field algorithm, a 2nd order boundary algorithm can lead to much more accurate solution than a 1st order one.2) To raise the accuracy of the solution,it's not enough to simply use a highe...

1996, 28(4): 392-399. doi: 10.6052/0459-1879-1996-4-1995-347

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THE MAXIMUM PACKING FRACTION AND YIELD STRESS OF CONCENTRATED SUSPENSIONS

A mathematic model is proposed to discribe the shear dependence of maximum packing fraction and the relationship between volume fraction and yield stress. The experimental data for cocoa/fat suspension and silica/glycerine water suspensionverified the model.

1996, 28(4): 400-405. doi: 10.6052/0459-1879-1996-4-1995-348

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LOCALIZATION BAND OF POST BIFURCATION IN PLANE SHEET

In order to simulate the subsequent effect caused by the flaw which is initiated at shear band bifurcation, a large strain finite element analysis is employed with an empty element technique designed to automatically release the residual stresses in the damaged elements. The damage relaxation can have either isotropic or anisotropic property. It is demonstrated that inclined localization band does radiate from the flaw in plane sheet loaded uniaxially. Thickness necking and plane shearing can be obvious...

1996, 28(4): 406-411. doi: 10.6052/0459-1879-1996-4-1995-349

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AN ELASTO PLASTIC CONSTITUTIVE EQUATIONS FOR THE STAINLESS STEEL UNDER COMBINED AXIAL AND TORSIONAL LOADS PART I. EXPERIMENTS

In the present paper, a series of experiments were performed on the plastic deformation of a thin walled tubular specimen of 1Cr18Ni9Ti S.S. along trilinear, circular and elliptical strain paths under combined loads of axial force and torque. The effects of intrinsic geometry of loading path on the magnitude and the direction of stress vector were investigated in plastic strain vectoral space. Experimental results show that the delay,the instantaneous softening and the recovery of hardening of stress respo...

1996, 28(4): 411-420. doi: 10.6052/0459-1879-1996-4-1995-350

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INVERSE ANALYSIS OF PSEUDO STATIC DISPLACEMENT FOR INHOMOGENEOUS VISCOELASTIC MEDIA

Based on the finite element and optimization methods, this paper develops the formulae of inverse analysis for inhomogeneous viscoelastic media. A preliminary discussion about identification of viscoelastic constitutive models is made, the effect of information error is considered, and some numerical examples are exhibited.

1996, 28(4): 421-428. doi: 10.6052/0459-1879-1996-4-1995-351

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1996, 28(4): 429-440. doi: 10.6052/0459-1879-1996-4-1995-352

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1996, 28(4): 441-448. doi: 10.6052/0459-1879-1996-4-1995-353

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GREEN'S FUNCTIONS OF UNSYMMETRIC LAMINATED PLATE WITH ELLIPTIC HOLE

According to the method for the bending analysis of composite laminates developed by the authors, Green's functions of an infinite unsymmetric laminate with elliptic hole or crack are obtained. These results can be used for stress analyses of laminated plates with holes or cracks acted by concentrated forces, and establishing corresponding numerical method for complex laminated structures by combining with Boundary Element Method.

1996, 28(4): 449-458. doi: 10.6052/0459-1879-1996-4-1995-354

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AN ORIENTED-ELEMENT THEORY FOR ANISOTROPIC VISCOPLASTICITY OF POLYCRYSTALLINE METALS

An Oriented-Element Theory (OET) originating with one of the present authors, Liang , is developed for studying viscoplastic behaviors of polycrystalline metals subjected to complex loading paths. Application of the work-conjugate principle and the field-average method leads to a concept of “oriented-element”, i.e. a representative or an averaged slip system for those practical slip systems that have the same orientations, from which a concise viscoplastic constitutive equation is derived. A numbe...

1996, 28(4): 459-467. doi: 10.6052/0459-1879-1996-4-1995-355

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THE ANALYTICAL APPROACH FOR LARGE SCALE NON CLASSICALLY DAMPED DYNAMIC SYSTEM

This paper gives a dynamic decoupling approach for the analysis of large scale non classically damped system, in which the complex number computations were completely avoided not only in solving for the eigenvalue problem but also in the calculation of the dynamic response.The analytical approach for undamped gyroscopic system, non classicaly damped system, including the damped gyroscopic system were unified. Very interesting and useful theoretical results, practical algorithms were obtained which is appl...

1996, 28(4): 468-474. doi: 10.6052/0459-1879-1996-4-1995-356

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NUMERICAL STUDY OF EFFECTIVE PROPERTIES OF PARTICULATE REINFORCED COMPOSITE MATERIALS

The method of cells and micromechanics in conjunction with the computational method is employed in this investigation to determine the local and average stress strain fields within the composite. Effective elastic properties of spherical and non spheridal particulate reinforced composite materials are analyzed by the finite element simulation. The effect of the particle array and distribution,particle orientation and shape on the effective moduli is examined in order to be able to design the better micro...

1996, 28(4): 475-482. doi: 10.6052/0459-1879-1996-4-1995-357

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NONSMOOTH ANALYSIS OF DYNAMICS OF A PIECEWISE LINEAR SYSTEM

Begins with analyzing the effect of nonsmooth vector field of a piecewise-linear system on the differentiability of the Poincare mapping, then, presents the dynamics complexity of the system through numerical simulations. The study shows that the system differs greatly in dynamics from a system with smooth vector field, when its periodic motion approaches a bifurcation of saddle-node(or relevant degenerated)type or penetrates a switching plane between two linear regions at very low velocity.

1996, 28(4): 483-488. doi: 10.6052/0459-1879-1996-4-1995-358

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RELATIONSHIP BETWEEN PENETRATION AND SHAPE OF FALLING DROP

Photos of falling drops in proccess of periodical deformation are presented. The penetration (it means the falling drop becomes a ring after colliding with surface of water and then it penetrates into water until the bottom is reached) happens after the drop with the shape of flat ellipse or its resemblance collides with the surface of water. Surface tension of drop water acts to deform the shape of falling drop.

1996, 28(4): 489-492. doi: 10.6052/0459-1879-1996-4-1995-359

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A STUDY OF MEASURING OUT OFF PLANE DISPLACEMENT USING DSPI UNDER IMPACT LOADING

The dynamic digital speckle pattern interferometry(DSPI) has been achieved by using the instantaneous image capturing technique. The measurement of out of plane displacement field of circular restrained plate with a cross point impact loading is completed. The results of dynamic finite element method show good agreement with those of experiments.

1996, 28(4): 493-497. doi: 10.6052/0459-1879-1996-4-1995-360

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A REVOLVING ONE HOLE PROBE IN 2 D GAS FLOW FIELD

According to the velocity measurement principle of the three hole probe,a revolving one hole probe is proposed in this paper to realize the gas velocity amplitude and direction measurement simulaneously, and the corresponding measurement system is built up. The characteristics of this system is studied by experimental investigation, and find its use in various recirculating flows and swirling flows. The correct measurement principal, good repectability and high accuracy of this system are verified by the ...

1996, 28(4): 498-502. doi: 10.6052/0459-1879-1996-4-1995-361

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SIMULTANEOUS FLUID VELOCITY AND TEMPERATURE MEASUREMENTS BY USING ENCAPSULATED LIQUID CRYSTAL PARTICLES

Chrolestic liquid crystal shows different color under different temperature, and this property has been used to measure the temperature on a solid surface or in a fluid. Encapsulated chrolestic liquid crystals has particlate shape and temperature color reactive property which can be used to measure velocity field and temperature field simultaneously. In this paper the particle image processing method was improved and the higher velocity accuracy was obtained in the large velocity gradient area. The hue t...

1996, 28(4): 503-506. doi: 10.6052/0459-1879-1996-4-1995-362

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1996, 28(4): 507-512. doi: 10.6052/0459-1879-1996-4-1995-363

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1996 Vol. 28, No. 4

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