A MOVING CRACK IN A NONHOMOGENEOUS MATERIAL STRIP

This paper considers an anti-plane moving crack in a nonhomogeneous material strip of finite thickness. The shear modulus and the mass density of the strip are considered for a class of functional forms for which the equilibrium equation has analytical solutions. The problem is solved by means of the singular integral equation technique. The stress field near the crack tip is obtained. The results are plotted to show the effect of the material non-homogeneity and crack moving velocity on the crack tip field. Crack bifurcation behaviour is also discussed. The paper points out that use of an appropriate fracture criterion is essential for studying the stability of a moving crack in nonhomogeneous materials. The prediction whether the unstable crack growth will be enhanced or retarded is strongly dependent on the type of the fracture criterion used. Based on the analysis, it seems that the maximum 'anti-plane shear' stress around the crack tip is a suitable failure criterion for moving cracks in nonhomogeneous materials.     

BENDING OF A CIRCULAR CYLINDER CONTAINING A CRACK

The sludy of bending of cracked circular cylinders is of more significance.The bendingof cylinders containing radical crack or cracks was discussed by refs.[1]-[4]and that ofconcentrically craked circular cylinders was studied by[5].Continuing[6]and usingcomplex variable methods in elasticity,this paper deals with the bending problems of acircular cylinder,containing an internal linear crack at any position under an acting forceperopendicular to the crack.The general forms of displacements stresses,and stress-intensity factors,expressed in terms of series,are obtained and to this bending problemswith small Ah are presented good approximate formulas for the stress-intebsity factorswhose variations with the center of the crack are analysed.Finally,the twist angle per unitlength and the center of bending for the radically cracked circular cylinder,one of whosecrack-tips is located at the origin,have been computed and the results are almost the sameas that calculated in[1].     

A MODE Ⅱ CRACK IN A TWO-DIMENSIONAL OCTAGONAL QUASICRYSTALS

The present study develops the fracture theory for a two-dimensional octagonal quasicrystals. The exact analytic solution of a Mode Ⅱ Griffith crack in the material was obtained by using the Fourier transform and dual integral equations theory, then the displacement and stress fields, stress intensity factor and strain energy release rate were determined, the physical sense of the results relative to phason and the difference between mechanical behaviors of the crack problem in crystal and quasicrystal were figured out. These provide important information for studying the deformation and fracture of the new solid phase.     

A MODE Ⅱ CRACK IN A TWO-DIMENSIONAL OCTAGONAL QUASICRYSTALS

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LUBRICATION ANALYSIS OF A CELL SLIDING INTO A CIRCULAR PORE

The resistance to the blood cells at the entrance to capillaries and membrane porescontributes considerably to the peripheral resistance in the blood circulation.This paperproposes,for the first time,a simplified mechanical model in an attempt to treat theaxisymmetric motion of a cell sliding into a circular pore.In this model,the shape of the cellis taken as given according to the microvideograph and the cell membrane is assumed toslide over its surface.The lubrication theory is applied to the thin layers of plasma betweenthe membrane and the pore wall,yielding the pressure and shear stress distributions over themembrane as well as the resultant drag exerted on the cell.Our computations havesimulated the process of the cell entering the pore,which is in qualitative agreement with themicrovideographic observations.     

NUMERICAL SIMULATION FOR A PROCESS ANALYSIS OF A COKE OVEN

A computational fluid dynamic model is established for a coking process analysis of a coke oven using PHOENICS CFD package. The model simultaneously calculates the transient composition, temperatures of the gas and the solid phases, velocity of the gas phase and porosity and density of the semi-coke phase. Numerical simulation is illustrated in predicting the evolution of volatile gases, gas flow paths, profiles of density, porosity of the coke oven charge, profiles of temperatures of the coke oven gas and the semi-coke bed. On the basis of above modeling, the flow of coke oven gas （COG） blown from the bottom of the coke oven into the porous semi-coke bed is simulated to reveal whether or not and when the blown COG can uniformly flow through the porous semi-coke bed for the purpose of desulfurizing the semi-coke by recycling the COG. The simulation results show that the blown COG can uniformly flow through the semi-coke bed only after the temDerature at the center of the semi-coke bed has risen to above 900℃.     

SHEARING FLOW NEAR A BYPASS WITH A BALL IN IT

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A CLASS OF VARIATIONAL DIFFERENCE SCHEMES FOR A SINGULAR PERTURBATION PROBLEM

In this paper,a singularly perturbed boundary value problem for second order self-adjoint ordinary differential equation is discussed.A class of variational difference schemesis constructed by the finite element method.Uniform convergence about small parameter isproved under a weaker smooth condition with respect to the coefficients of the equation.The schemes studied in refs.[1],[3],[4]and[5]belong to the class.     

AN ANALYSIS OF A CYLINDRICAL THIN SHELL AS A PIEZOELECTRIC TRANSFORMER

The vibration of a circular cylindrical piezoelectric ceramic shell with tangential poling is investigated for transformer application and an analytical solution is obtained.Numer- ical calculations of the output voltage,input admittance and the efficiency of the transformer are presented.The results indicate that the structure analyzed can be used as a piezoelectric transformer with a certain harmonic driving frequency and matching load impedance.     

AN ANALYSIS OF A RADIAL CRACK IN A REINFORCED HOLLOW CYLINDER

Using the Michell solution and the crack solution, the integral equation of a radialcrack in a hollow cylinder reinforced on its outer boundary is derived. The effects of thereinforced membrane on the crack are analysed and several numerical results are presentedherein.     

INTERACTION OF A DISLOCATION DIPOLE WITH A MODE III INTERFACE CRACK

Interaction between a screw dislocation dipole and a mode III interface crack is investigated. By using the complex variable method, the closed form solutions for complex potentials are obtained when a screw dislocation dipole lies inside a medium. The stress fields and the stress intensity factors at the tip of the interface crack produced by the screw dislocation dipole are given. The influence of the orientation, the dipole arm and the location of the screw dislocation dipole as well as the material mismatch on the stress intensity factors is discussed. The image force and the image torque acting on the screw dislocation dipole center are also calculated. The mechanical equilibrium position of the screw dislocation dipole is examined for various material property combinations and crack geometries. The results indicate that the shielding or anti-shielding effect on the stress intensity factor increases abruptly when the dislocation dipole approaches the tip of the crack. Additionally, the disturbation of the interface crack on the motion of the dislocation dipole is also significant.     

ANALYSIS OF DAMAGE NEAR A CONDUCTING CRACK IN A PIEZOELECTRIC CERAMIC

The finite element formulation for analyzing static damage near a conducting crack in a thin piezoelectric plate is established from the virtual work principle of piezoelectricity. The damage fields under various mechanical and electrical loads are calculated carefully by using an effective iterative procedure. The numerical results show that all the damage fields around a crack tip are fan-shaped and the electric field applied has great influence on the mechanical damage,which is related to the piezoelectric properties.     

A HYBRID FEM ALGORTHM FOR FLUID FLOW IN A VISCO-ELASTIC PIPE

A variational principle of hybrid FEM is proposed to solve the flow in a visco-elasticpipe.As an example,the influence of an axisymmetrical stenosis on an artery vibrating flowwith a single frequency is calculated.     

PROPERTIES OF A HALF SPACE INCLUDING A TWISTED SHAFT OF REVOLUTION

The properties of an elastic half space including a partly embedded twisting shaft of revolution are studied. Without knowing the exact solution of the torsion problem of agiven embedded shaft, these properties can indicate some features of thc displacement or stress field of the half space and can sometimes be used for checking a numerical sohttion. An example for checking the correct stress distribution on surfaces of twisted rigid cylindrical shaft embedded in a half space is given.     

MID-FACETS OF A SIMPLEX

The mid-facet of a simplex in n-dimensional Euclidean space which was introduced quite recently is an important geometric element. An analytic expression for the mid-facet area of a simplex is firstly given. In order to obtain the expression, the exterior differential method was presented. Furthermore, the properties of the mid-facets of a simplex analogous to median lines of a triangle ( such us for all mid-facets of a simplex,there exists another simplex such that its edge-lengths equal to these mid-facets area respectively, and all of the mid-facets of a simplex have a common point) were proved.Finally, by applying the analytic expression, a number of inequalities which combine edge-lengths, circumradius , median line, bisection area and facet area with the mid-facet area for a simplex were established.     

FLOW OF A TRAIN OF DEFORMABLE FLUID PARTICLES IN A TUBE

I.IntroductionWangandSkalakll]studiedforsolidspheresintubes.HymanandSkalak12--31studiedthemovementofacompactfluidspheres(non-deformable)intubes.Theyonlystudiedcompactdropswhoseradiusesarenotbiggerthan0.7.Pozrikidisl4]studiedthenlotiollofdeformabletluidparticlesintubes.Inthispaper,westudiedtwo-phasenowregime,consistingofaperiodictrainofequallyspacedliquidslugsmovingaxisymmetricallyinacontinuousliquidphasewhichisimmisciblewiththeslugphase(Fig.l(a)).Wereportnumericalsolutionsforthehydrodynamic…     

NORMAL PERFORATION OF A THIN INFINITE PLATE BY A FLAT-HEADED CYLINDRICAL PROJECTILE

Analytical formulae for calculating the stress acting on the contact surface between projectile and target and for calculating the moving velocity of this contact surface under impact are both suggested in this paper. These formulae can be thought of as a generalization of the well-known Hopkins and Kolsky's theory in plastic domain. And then, an analytical formula for calculating ballistic limit is also suggested. It is also proved in this paper that the shear stress acting on the cylindrical surface of the plug is distributed uniformly.     

STABILITY AND LOCAL BIFURCATION IN A SIMPLY-SUPPORTED BEAM CARRYING A MOVING MASS

The stability and local bifurcation of a simply-supported flexible beam(Bernoulli- Euler type)carrying a moving mass and subjected to harmonic axial excitation are investigated. In the theoretical analysis,the partial differential equation of motion with the fifth-order nonlinear term is solved using the method of multiple scales(a perturbation technique).The stability and local bifurcation of the beam are analyzed for 1/2 sub harmonic resonance.The results show that some of the parameters,especially the velocity of moving mass and external excitation,affect the local bifurcation significantly.Therefore,these parameters play important roles in the system stability.     

A NEW ENGINEERING CALCULATING MODEL FOR A LINEAR INCLUSION AND ITS APPLICATIONS

By using the hypothesis of the deformation of the straight bar and beamin mechanics of materials,a new engineering calculating model for a linear inclusion inplane is presented.Through the Kelvin's solution of a concentrated force,the inclusionproblem is reduced to solving a set of uncoupled singular integral equations which canbe solved by the numerical method of singular integral equation.Based on theseresults,several applicable examples including an inclusion-crack problem are calculatedand the results are quite satisfactory.     

A PENNY-SHAPED CRACK IN A MAGNETOELECTROELASTIC LAYER UNDER RADIAL SHEAR IMPACT LOADING

This paper analyzes the dynamic magnetoelectroelastic behavior induced by a penny- shaped crack in a magnetoelectroelastic layer.The crack surfaces are subjected to only radial shear impact loading.The Laplace and Hankel transform techniques are employed to reduce the prob- lem to solving a Fredholm integral equation.The dynamic stress intensity factor is obtained and numerically calculated for different layer heights.And the corresponding static solution is given by simple analysis.It is seen that the dynamic stress intensity factor for cracks in a magnetoelec- troelastic layer has the same expression as that in a purely elastic material.And the influences of layer height on both the dynamic and static stress intensity factors are insignificant as h/a>2.