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FREE VIBRATIONS OF ATHIN COMPLETE SPHERICAL SHELL SUBMERGED IN A COMPRESSIBLE FLUID MEDIUM

By the introduction of two displacement functions,the non-axisymmetric free vibrations of a complete thin isotropic spherical shell submerged in a compressible fluid medium are successfully investigated.It is found that there are two classes of free vibrations:the first class is not affected by the ambient fluid while the second is.It is further proved that the frequency equations can be expressed in terms of polynomial.For the second class of vibration of submerged spherical shell,it is also demonstrated t...

1995, 27(4): 385-397. doi: 10.6052/0459-1879-1995-4-1995-446

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THE DIGITAL FILTER METHOD OF EXTRACTING THE COHERENT STRUCTUREIN WALL TURBULENCE

The data obtained from the turbulent boundary layer on a flat plate using 3-component hot wire probe are analysed.A method is proposed,which used a digital fiiter to decompose turbulent signal into two parts.One is small scale eddies that is nearly isotropic,the other is large scale eddies that is anisotropic.Then,the conditional sampling is used to extract the coherent structure.

1995, 27(4): 398-405. doi: 10.6052/0459-1879-1995-4-1995-447

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A GENERAL FORMULATION OF DRILL STEM MECHANICS AND ITS APPLICAIIONS

This paper provides a general formulation of drill stem dynamics under ge-ometrically non- linear conditions.As applications,three important mathematical modelsin directional drilling steerable down hole motor assembly under small deflection,steerabledown hole motor assembly under large deflection and mathematical model of tension andtorque in drill stem under steady condition have been estabished.

1995, 27(4): 406-414. doi: 10.6052/0459-1879-1995-4-1995-448

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A INCOMPRESSIBLE RUBBER CONE UNDER THE TENSION OF CONCENTRATED FORCE

This paper andyses the stress distribution and the deformation pattern near theapex of a incompressible rubber cone that is under the tension of a concentrated force.Theasymptotic mathematical solution to the stress field near the apex of the cone is presented,when the cone angle is 180°,it turned out to be the non-linear Boussinesq’s problem.

1995, 27(4): 415-423. doi: 10.6052/0459-1879-1995-4-1995-449

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TWO-DIMENSIONAL PROBLEMS OF THE ANISOTROPIC ELASTIC SOLID WITH AN ELLIPTIC INCLUSION

The two-dimensional problem of an anisotropic elastic solid with an elliptic in-clusion subjected to polynomial loading at infinity is examined.The elastic fields throughout the material are determined throiigh Stroh’s formalism and the integral equation method. Based upon the above results two special examples,with leadings applied at infinity in the form of polynomials of degree 2 in x_1 and x_2,are studied and the hoop stress distribution around the elliptic boundary is obtained.

1995, 27(4): 424-433. doi: 10.6052/0459-1879-1995-4-1995-450

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ELASTIC/VISCOPLASTIC SOLUTION OF TWISTY COLUMNS BY MEANS OF LAPLACE FUNCTIONAL TRANSFORMAIIONS

By means of Laplace transformation,the whole process of the twisting ofelastic/viscoplastic columns are solved in this paper.In considering the distribution of thestresses in the column,we construct a stress function and a displacement function and thenuse Laplace transformation.The solutions cylinder and a cylinder with a hole are obtained.

1995, 27(4): 434-439. doi: 10.6052/0459-1879-1995-4-1995-451

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ANALYSIS AND COMPUTATION OF STRESS DECAY RATE OF SELF-EQUILIBRATED END LOAD PROBLEM

This paper presents a method for stress decay rate analysis of the self-equilibrated end load problem.Using the boundary element method,the minimum stress decay rate of elastic cylinder with elliptical or rectangular section,subjected to the self-equilibrated end load is obtained.The numerical results show that the variation of the minimum decay rate is small when the ratio of the longer axis to the shorter one ofthe ellip-tic section or the ratio of the length to the width of the rectangular section of the...

1995, 27(4): 440-450. doi: 10.6052/0459-1879-1995-4-1995-452

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ALL PARIICULAR SOLUTION METHOD IN BOUNDARY ELEMENT TECHNIQUES

In this paper,the all particular solution field is formed by utilization of corre-spondent fundamental solutions,so that all elements in the coefficient matrix of boundaryelement equations for problems to be solved will be determined.In the process of solution,interpolation and numerical integration are not needed and numerical treatment for singu-lar integration is avoided,and the calculation of physical characteristics(e.g.stress,soundintensity,nd etc.)of any point does not depend on boundary unknowns to ...

1995, 27(4): 451-458. doi: 10.6052/0459-1879-1995-4-1995-453

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THE GENERALIZED HYBRID METHOD FOR NONLINEAR FINITE ELEMENT ANALYSIS

Based on a rational choice of the admissible functious,which are the displace-ments,the displacement-gradients and the first Piola st resses,as the independent variables,the new variational principles with relaxed inte relement continuity requirements have beendeveloped for nonlinear finite element method,and the generalized hybrid methods for non-linear analysis by use of the nonconforming models are established.

1995, 27(4): 459-469. doi: 10.6052/0459-1879-1995-4-1995-454

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STUDY ON PSEUDOELASTICITY OF Cu-Zn-Al POLYCRYSTALLINE SHAPE MEMORY ALLOY BY MOIRE INTERFEROMETRY

An experimental study on the constitutive behavior of Cu-Zn- Al polycrystallineshape memory alloy is reported.By means of moire interferometry, both the displacementfields and t he corresponding pseudoelasticity stress strain curves are obtained.The experi-ment reveals some important features of the deformation process,and a brief discussfon ismade for the obtained results.

1995, 27(4): 470-476. doi: 10.6052/0459-1879-1995-4-1995-455

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NUMERICAL SIMULATION OF FLOW OVER A THREE DIMENSI0NAL BLUNTBODY WITH OSCILLATION

Flow field characteristics over an oscillating blunt body(Capsule-type vehicle)was investigated by numerical method.In this study,two second order implicit TVD(total variation diminishing scheme)scheme was used to solve full Navier-Stokes equations.The results have shown some very important information about flow over an oscillating blunt body,such as unsteady separation,shock and pressure distributions on the surface

1995, 27(4): 477-481. doi: 10.6052/0459-1879-1995-4-1995-456

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THE THIN SHELL THEORETICAL SOLUTION FOR CYLINDRICAL SHELLS WITH LARGE OPENINGS

The analytical solution for cylindracal shells with ρ0≤0.7,r_0,R radii of hole and shell,respectively; T thickness of shell)are presented inthis paper by solving the modified Morley’s equation. The accurate boundary conditions atthe hole edge are asymptoticly expanded in powers of ρ0 and T/R.

1995, 27(4): 482-488. doi: 10.6052/0459-1879-1995-4-1995-457

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A NEW LIMIT-LOAD FORMULA FOR THE LIGAMENT OF A SURFACE CRACK

During Leak-Before-Break assessment,it is of great importance to predict thelimit-load of the ligament at a surface crack.The current limit-load formulas are mostlyoverconservative.By using them in LBB assessment,the actual transient length of throughcrack at penetration will be underestimated with unsafe assessment results.In this paper,anew collapse model of the ligament at a surface crack is propsed.The derivation of relevantnew limit-load formula of ligament is briefly presented.Finally,in terms of diag...

1995, 27(4): 489-494. doi: 10.6052/0459-1879-1995-4-1995-458

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STUDY OF POWERFLOW FOR PLATE ASSEMBLIES WITH BBD

Bean bag damping is a new technique for vibration and noise control.Based on its characteristics,mechanical mobility and structural dynamics,some analytical formulae for three different plate assemblies with BBD are derived.There is a good agreement among those results of computation using these formulae and those obtained by measuring the power flow in the structures.Finally,a discussion about the effect BBD on the power flow in the structurps is given in this paper.

1995, 27(4): 495-500. doi: 10.6052/0459-1879-1995-4-1995-459

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MECHANICS MODELS FOR PREDICTION AND CONTROL OF THE WELLBORE TRAJECTORY

This paper presents the governing equation for the dynamic behavior ofabottomhole assembly in 3-D space.Then,a vector model of rock-bit interaction is deveiopedby taking account of the anisotropic drilling characteristics of both the formation and the bit.Finally,this paper discusses the basic principles and methods of predicting and controllingthe wellbore trajectory.

1995, 27(4): 501-505. doi: 10.6052/0459-1879-1995-4-1995-460

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AN EXPERIMENTAL ANALYSIS FOR SINGULAR STAIE NEAR EDGE OF INTERFACE IN BIMAIERIAL

The stress state and its singularity at the edge of the interface in a bondedbimaterial beam is investigated experimentally by moire interferometry and localized bybridmethod.The bimaterial beam is made of CR-39 and epoxy resin, which glued byan epoxyadhesive.The sensitivity of moire interferometry experiment is 0.41 7μm.The localizedhybrid method,which combine the moire inferometry and finite element method,is usedto evaluate the experimental results from displacements to stresses.For comparing theexperime...

1995, 27(4): 506-512. doi: 10.6052/0459-1879-1995-4-1995-461

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1995 Vol. 27, No. 4

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