热冲击载荷作用下的含球形空腔的广义热弹性功能梯度球形各向同性体

This paper is concerned with the determination of thermoelastic displacement, stress and temperature in a functionally graded spherically isotropic infinite elastic medium having a spherical cavity, in the context of the linear theory of generalized thermoelasticity with two relaxation time parameters （Green and Lindsay theory）. The surface of cavity is stress-free and is subjected to a time-dependent thermal shock. The basic equations have been written in the form of a vector-matrix differential equation in the Laplace transform domain, which is then solved by an eigenvalue approach. Numerical inversion of the transforms is carried out using the Bellman method. Displacement, stress and temperature are computed and presented graphically. It is found that variation in the thermo-physical properties of a material strongly influences the response to loading. A comparative study with a corresponding homogeneous material is also made.     

Transient responses of a multilayered spherically isotropic piezoelectric hollow sphere

The dynamic solution of a multilayered spherically isotropic piezoelectric hollow sphere subjected to radial dynamic loads is obtained. By the method of superposition, the solution is divided into two parts: one is quasi-static and the other is dynamic. The quasi-static part is derived by the state-space method, and the dynamic part is obtained by the method of separation of variables coupled with the initial parameter method as well as the orthogonal expansion technique. By using the quasi-static and dynamic parts, the electric boundary conditions as well as the electric continuity conditions, a Volterra integral equation of the second kind with respect to a function of time is derived, which can be solved successfully by means of the interpolation method. The displacements, stresses and electric potentials are finally obtained. The present method is suitable for a multilayered spherically isotropic piezoelectric hollow sphere consisting of arbitrary layers and subjected to arbitrary spherically symmetric dynamic loads. Finally, numerical results are presented and discussed.     

Transient thermal stresses and thermal deformations in a solid cylinder with a moving boundary

Summary This paper is concerned with transient thermal stresses and thermal deformations of the axisymmetric problem of a solid cylinder on consideration of a moving boundary. Assuming that a heated edge of the cylinder which is kept at a constant temperature moves with a constant velocity, the temperature distribution of the cylinder is analyzed using a moving coordinate system. Thereafter, the associated thermal stress distributions and thermal displacements are determined with aid of the method of the thermoelastic potential function and Love's displacement function. As an illustration, numerical calculations are carried out for several values of the velocity of the moving boundary, and the influence of the velocity on the temperature distribution and the stress distribution are examined precisely.

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Wärmespannungen und Verformungen in einem Zylinder mit bewegter Wärmequelle

Übersicht Es werden die Wärmespannungen und Verformungen in einem Zylinder untersucht, bei dem sich eine Wärmequelle mit konstanter Geschwindigkeit in axialer Richtung bewegt. Zunächst wird dabei die Temperaturverteilung im Zylinder mit Hilfe eines bewegten Koordinatensystems ermittelt. Dann werden die Wärmespannungen und die Verformungen mit der thermoelastischen Potentialfunktion und mit der Loveschen Verschiebungsfunktion bestimmt. Numerische Beispiele zeigen den Einfluß der Geschwindigkeit der Wärmequelle auf die Temperatur- und die Spannungsverteilung.

     

Transient thermal stresses in two-dimensional functionally graded thick hollow cylinder with finite length

In this paper transient thermal stresses in a thick hollow cylinder with finite length made of two-dimensional functionally graded material (2D-FGM) based on classical theory of thermoelasticity are considered. The volume fraction distribution of materials, geometry and thermal load are assumed to be axisymmetric but not uniform along the axial direction. The finite element method with graded material properties within each element is used to model the structure. Temperature, displacements and stress distributions through the cylinder at different times are investigated. Also the effects of variation of material distribution in two radial and axial directions on the thermal stress distribution and time responses are studied. The achieved results show that using 2D-FGM leads to a more flexible design so that time responses of structure, maximum amplitude of stresses and uniformity of stress distributions can be modified to a required manner by selecting suitable material distribution profiles in two directions.     

Transient thermal stresses in an orthotropic hollow cylinder for axisymmetric problems

For the thermoelastic dynamic axisymmetric problem of a finite orthotropic hollow cylinder, one comes closer to reality to involve the effect of axial strain than to consider the plane strain case only. However, additional mathematical difficulties should be encountered and a different solution procedure should be developed. By the separation of variables, the thermoelastic axisymmetric dynamic problem of an orthotropic hollow cylinder taking account of the axial strain is transformed to a Volterra integral equation of the second kind for a function of time, which can be solved efficiently and quickly by the interpolation method. The solutions of displacements and stresses are obtained. It is noted that the present method is suitable for an orthotropic hollow cylinder with an arbitrary thickness subjected to arbitrary axisymmetric thermal loads. Numerical comparison is made to show the effect of the axial strain on the displacements and stresses. The project supported by the National Natural Science Foundation of China (10172075) and China Postdoctoral Science Foundation (20040350712)     

Size-dependent effective thermoelastic properties of nanocomposites with spherically anisotropic phases

Composites made of semi-crystalline polymers and nanoparticles have a spherulitic microstructure which can be reasonably represented by a spherically anisotropic volume element. Due to the high surface-to-volume ratio of a nanoparticle, the particle-matrix interface stress, usually neglected in determining the effective elastic moduli of particle-reinforced composites, may have a non-negligible effect. To account for the latter in estimating the effective thermoelastic properties of a composite consisting of nanoparticles embedded in a semi-crystalline polymeric matrix, this work adopts a coherent interface model for the nanoparticle-matrix interface and proposes an extended version of the classical generalized-self consistent method. In particular, Eshelby's formulae widely used to calculate the elastic energy change of a homogeneous medium due to the introduction of an inhomogeneity are extended to the thermoelastic case. The nanoparticle size effect on the effective thermoelastic moduli of the composite are theoretically shown and numerically illustrated.     

层合球面各向同性热释电空心球的瞬态响应

运用叠加原理，将层合球面各向同性热释电空心球的球对称动力学问题的解分成准静态和动 态两部分，准静态部分首先运用状态空间法给出了显式表达式，然后运用分离变量法、初参 数法和特征函数展开技术，给出了动态部分的表示式，再结合内外表面上的电学边界条件和 界面上的电学连续条件，导出一个关于时间函数的第二类Volterra积分方程，运用插值法 可成功地给出此积分方程的高精度数值解，最终可求得原问题的位移、应力、电位移以及电 势的响应. 此方法适用任意层数且各层是任意厚度的层合热释电空心球作用随时间以任意形 式变化的球对称温度场. 文中还给出了数值结果.     

Transient thermoelastic contact problem of a transversely isotropic cylinder

Summary This paper concerns a transient thermoelastic contact problem in a transversely isotropic infinite cylinder inserted into a heated rigid ring. It is assumed that the heat transfer coefficient at the bonded surface is different from the coefficient at the traction-free boundary surface. A finite difference formulation with respect only to time is used to solve the three-dimensional transient heat conduction equation for the temperature field. The thermal stress field is analyzed by means of the transversely isotropic potential function method. The radial, hoop and axial stresses have singularities at the end of the contact surface. The concentration factors that may be used to evaluate the strength of the stress singularities are introduced.

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Ein transientes thermoelastisches Kontaktproblem eines transversal-isotropen Zylinders

Übersicht Behandelt wird ein transientes thermoelastisches Kontaktproblem eines transversal-isotropen unendlichen Zylinders, der in einen geheizten starren Ring eingesetzt wird. Der Wärmeübergang in der Kontaktfläche und der freien Oberfläche seien verschieden. Bei der Lösung der instationären dreidimensionalen Wärmeleitungsgleichung wird bezüglich der Zeit eine Finite-Differenzen-Formulierung benutzt. Die Wärmespannungen werden nach der Potentialfunktionen-Methode im transversalisotropen Fall ermittelt. Radial-, Umfangs- und Axialspannung weisen am Ende der Kontaktzone Singularitäten auf, die durch eingeführte Spannungskonzentrationsfaktoren beschrieben werden.

     

Transient thermal stresses in anisotropic bodies with spherical symmetry

Summary The quasi-static thermo-elastic equations are solved for material which is transversely isotropic about the radius vector. The Laplace transform is used to obtain a general solution of the equations in which all quantities are assumed to depend on the radial co-ordinate and the time only. The particular problems of constant temperature suddenly applied to the surfaces of a solid sphere and a spherical cavity in an infinite solid are considered. Numerical results are presented for the second of these problems.     

Analytical solution for the electroelastic dynamics of a nonhomogeneous spherically isotropic piezoelectric hollow sphere

Summary By introduction of a special dependent variable and separation of variables technique, the electroelastic dynamic problem of a nonhomogeneous, spherically isotropic hollow sphere is transformed to a Volterra integral equation of the second kind about a function of time. The equation can be solved by means of the interpolation method, and the solutions for displacements, stresses, electric displacements and electric potential are obtained. The present method is suitable for a piezoelectric hollow sphere with an arbitrary thickness subjected to arbitrary mechanical and electrical loads. Numerical results are presented at the end.The work was supported by the National Natural Science Foundation of China (No. 10172075 and No. 10002016).     

A note on thermal stresses in hollow cylinders

Conclusions The extensions of Trostel's solutions derived in this paper may be employed tor general over wide conditions with a resulting error less than 3%, the stress values being too small in magnitude by this amount. The error decreases as the variation of physical properties of the media decreases or as 1/2. M. M. Stanii, Lectures in Mathematical Elasticity during summer semester 1958, Purdue University.     

Generalized thermoelastic functionally graded orthotropic hollow sphere under thermal shock with three-phase-lag effect

This problem deals with the determination of thermo-elastic interaction due to step input of temperature on the boundaries of a functionally graded orthotropic hollow sphere in the context of linear theories of generalized thermo-elasticity. Using the Laplace transformation the fundamental equations have been expressed in the form of vector–matrix differential equation which is then solved by eigenvalue approach. The inverse of the transformed solution is carried out by applying a method of Bellman et al. Stresses, displacement and temperature distributions have been computed numerically and presented graphically in a number of figures. A comparison of the results for different theories (TEWOED(GN-II), TEWED(GN-III) and three-phase-lag model) is presented. When the material is homogeneous, isotropic and outer radius of the hollow sphere tends to infinity, the corresponding results agree with that of existing literature for GN-III model.     

Transient thermoelastic waves in an anisotropic hollow cylinder due to localized heating

This paper presents a theoretical study of transient ultrasonic guided waves generated by concentrated heating of the outer surface of an infinite anisotropic hollow circular cylinder. Generalized thermoelastic theory proposed by Lord and Shulman is adopted to model the dynamic thermoelastic behavior of the cylinder. The concentrated heat source model used is to represent heating due to a pulsed laser beam, which is focused on the outer surface of the cylinder. A semi-analytical finite element (SAFE) method is employed to evaluate guided wave modes in the cylinder. Using integral transform techniques, the modal wave forms are obtained in frequency and wave number domains. Time histories of the propagating modes are then calculated by applying inverse Fourier transformation in the time domain. Numerical results showing the dispersion curves for the group velocities of the propagating modes and transient radial displacements are presented. For this purpose it is assumed that the cylinder is made of transversely isotropic silicon nitride (Si₃N₄). Attention is focused on the propagation characteristics of longitudinal and flexural modes separately.     

Transient thermal stresses in a strip with an eccentric hole

A procedure is presented for dealing with the constraint associated with the direction of the thickness of a thin model and for obtaining transient thermal stresses under plane-stress conditions; the stresses are induced by severe thermal loads. Thermal-stress-concentration factor in an unrestrained strip with an eccentric circular hole placed near the thermally loaded edge is obtained. One straight edge of the strip is cooled and the others are insulated. Consequently, two cases for which the hole acts remarkably as a stress raiser are found.     

Transient responses of a magneto-electro-elastic hollow sphere for fully coupled spherically symmetric problem

By introducing a dependent variable and a special function satisfying the inhomogeneous mechanical boundary conditions, the governing equation for a new variable with homogeneous mechanical boundary conditions is derived. Then by means of the separation of variables technique and the electric and magnetic boundary conditions, the dynamic problem of a magneto-electro-elastic hollow sphere under spherically symmetric deformation is transformed to two Volterra integral equations of the second kind about two functions of time. Cubic Hermite polynomials are adopted to approximate the two undetermined functions at each time subinterval and the recursive formula is obtained to solve the integral equations successfully. The transient responses of displacements, stresses, electric and magnetic potentials are completely determined at the end. Numerical results are presented.     

Some exact results concerning thermoelastic properties of hollow sphere composites

1.IntroductionAsakindofwidelyusedlowdensitymaterials,compositeconsistingofamatrixanddistributedhollowsphereshaveattractedIncreasingresearchinterest.Relatedworkswhicharefocusedonthetheoreticalpredictionof.theeffectiveelasticmoduliofsuchcompositescanbefoundinLeeandWestmannl'1,QiuandWengl=],HuangandGibsonl31aswellasChercauoietal.HI.HuangandGibson13]havealsocarriedoutanexperimentalinvestigationonmechanicalbehavioursofthecomposites.Thepresentpapercontinuestheseinvestigationsandisfocusedonfindi…     

Equilibrium problems of spherically isotropic bodies

In this paper the displacements and body-forces are resolved,respectively,and the3-dimensional equilibrium problems of spherically isotropic bodies with body-forces aretransferred into a two-order differential equation and a four-order differential equation.Based on the series expansion technique and properties of spherical functions,the seriessolutions are obtained for the corresponding homogeneous equations,which can be adaptedto solve equilibrium problems of whole spheres or spherical shells.The special solution for arevolving sphere is also given.     

Steady state thermal and mechanical stresses of a poro-piezo-FGM hollow sphere

In this study, an analytical method is developed to obtain mechanical and thermal stress and electrical potential functions, electrical and mechanical displacement in two dimensional steady (r,θ) stat a functionally graded piezo electric porous material hollow sphere (FGPPM). It is assumed that properties of poro, piezoelectric and FGM material is changed through thickness according to power law functions, Heat conduction equation is obtained for obtaining temperature distribution and Navier equations analytically using Legendre polynomials and Euler differential equations system for investigating displacements changes and stress and potential functions for different power indices law and is drawn on a graph. These results are confirmed with the obtained in formations in the paper.     

Transient thermal stresses in fully and partly cooled circular rings

The constraint associated with the direction of the thickness of a thin photoelastic circular-ring model is experimentally proved to occur and it is compared with the theoretical result; the constraint is induced by thermal loads. The method for dealing with the constraint and for obtaining a transient thermal stress under plane-stress conditions is applied to study the thermal stress of the circular ring partly cooled from the inside cylindrical surface. It is found that the thermal stress of the fully cooled circular ring is not always greater than the partly cooled one.