ON A THEORY OF THERMOELASTICITY WITH MICROTEMPERATURES

The article is concerned with a linear theory for elastic materials with inner structure whose particles, in addition to the classical displacement and temperature fields, possess microtemperatures. In the first part of the article we derive an existence result for the dynamical theory and establish the continuous dependence of solutions on the initial data and body loads. Then we consider the equilibrium theory and present a uniqueness result and a solution for the field equations. The theory is illustrated with the solution of the problem of thermal stresses in an elastic space with a spherical cavity.     

ON A THEORY OF MICROMORPHIC ELASTIC SOLIDS WITH MICROTEMPERATURES

The article is concerned with a linear theory for elastic materials with inner structure whose particles, in addition to the classical displacement and temperature, possess microtemperatures and can stretch and contract independently of their translations. Microrotational effects are not present. A uniqueness result in the dynamical theory of anisotropic materials is established. The existence of a generalized solution is also studied.     

ON THE PROPAGATION OF THE THERMAL WAVES IN MATERIALS WITH MEMORY

The propagation of one-dimensional acceleration waves in linear thermoelastic materials with thermal memory is analyzed. It is shown that two types of waves may exist, and the properties of velocities and attenuation of these waves are examined. The obtained results are compared with the data of the previous works     

A NOTE ON THE THEORY OF THERMOELASTIC DAMPING

This paper consists of three parts. In the first part, the problem of the conversion of mechanical energy into heat is treated, while in the second a general theory of thermoelastic friction in three-dimensional finite bodies is developed. In the third part, explicit results are obtained for thermoelastic damping in vibrating elastic beams. All investigations are based on the linear theory of thermoelasticity.     

A THEORY OF THERMOELASTIC MATERIALS WITH VOIDS WITHOUT ENERGY DISSIPATION

This article is concerned with the theory of thermoelastic materials with voids based on the concept of volume fraction [Goodman and Cowin, Arch. Rational Mech. Anal., vol. 44, pp. 249-266, 1972; Nunziato and Cowin, Arch. Rational Mech. Anal., vol. 72, pp. 175-201, 1979]. We use the results of Green and Naghdi [Proc. Roy Soc. London A, vol. 432, pp. 171-194, 1991; J. Elasticity, vol. 31, pp. 189-209, 1993] on thermomechanics of continua to derive a linear theory of thermoelastic materials with voids that does not sustain energy dissipation and permits the transmission of heat as thermal waves at finite speed. Then we establish a uniqueness result and the continuous dependence of solutions upon the initial data and body loads.     

FUNDAMENTAL SOLUTIONS OF THE EQUATIONS OF THE THEORY OF THERMOELASTICITY WITH MICROTEMPERATURES

By means of elementary functions, the fundamental solutions of the equations of the equlibrium and steady oscillations of the theory of thermoelasticity with microtemperatures are constructed, and basic properties are established.     

DYNAMIC STABILITY OF ROTATING COMPOSITE SHELLS WITH THERMOACTTVE SHAPE MEMORY ALLOY FIBERS

In this article the technique of the dynamic stability analysis proposed for the conventional laminated shells is extended to the activated shape memory alloy hybrid cylindrical shells. The thin symmetrically balanced laminated shell contains both the conventional (e.g., graphite or glass) fibers oriented at +? and ? ? to the shell axis and the activated shape memory alloy fibers axially oriented. Rotary and coupling inertias are neglected. The rotating with a constant angular velocity shell is simply supported at the edge hoops. The effect of returning to the original geometry after a large inelastic deformation is called the shape memory effect. Changing the temperature of the layer we modify the basic mechanical properties such as Young's modulus and the damping coefficient. The purpose of this article is to solve the dynamic stability problem and to answer the question, how does the temperature activation change dynamic stability domains of the shell. Using the standard stability technique leads to the effective sufficient criterion of the dynamic stability. The stability regions as Junctions of angular velocity, the damping coefficient, and properties of shell material are given. The results indicate that the global activation increases the admissible angular velocity both for the glass-epoxy /NiTi-epoxy and graphite-epoxy /NiTi-epoxy hybrid shells     

ON THE DYNAMIC THEORY OF MIXTURES OF THERMOELASTIC SOLIDS

This article addresses the linear dynamic theory of binary mixtures of thermoelastic bodies. In the first part of this article we establish the continuous dependence of solutions upon initial data and body loads. Then we derive a spatial decay estimate of an energetic measure associated to a dynamical process.     

THERMOELASTICITY AND HEAT CONDUCTION WITH MEMORY EFFECTS

The thermodynamical foundations of generalized thermoelasticity formulated by Lord and Shulman are reviewed and memory effects on the heat flux are generalized. An existence and uniqueness theorem for the evolution integro-differential equations is obtained using semi-group theory.     

ON THE GRADE CONSISTENT THEORY OF MICROPOLAR THERMOELASTICITY

Abstract

A grade consistent micropolar theory of thermoeluslicily is considered. First some results concerning reciprocity, variational characterization of the solution, existence, and uniqueness are established. Then, the theory of homogeneous and isotropic solids is studied. A solution of Cauchy-Kovalevski-Somigliana type and the fundamental solutions in the case of steady vibrations are established. We also study the asymptotic behavior for the homogeneous problem.     

A THEORY OF THERMOVISCOELASTIC DIELECTRICS

We study finite deformations of heat conducting viscous dielectric solids and derive constitutive relations that satisfy an entropy inequality. These are simplified for orthotopic, transversely isotropic, and isotropic materials. For each class of materials, linear constitutive relations valid for infinitesimal deformations are derived.     

A TEMPERATURE-RATE-DEPENDENT THEORY OF THERMOPIEZOELECTRICITY

Governing equations of a temperature-rate-dependent thermopiezoelectricity theory which predicts a finite speed of propagation of thermal signals are obtained. A uniqueness theorem for solutions, a variational principle of Hamilton-type, and a reciprocal theorem are deduced in the context of the linearized theory.     

ON THE NONLINEAR THEORY OF NONSIMPLE THERMOELASTIC BODIES

A nonlinear theory of nonsimple thermoelastic materials is considered. The continuous dependence upon initial-state and supply terms of smooth thermodynamic processes is studied     

FORCED CONVECTION HEAT TRANSFER OF INTERACTING SPHERES

A basic understanding of the highly nonlinear interaction effects of closely spaced spheres on fluid mechanics and heat transfer parameters is important for improving the design of a variety of thermal fluid-particle systems. Fluid flow patterns, isotherms, as well as Nusselt number distributions and extended correlations are presented for steady laminar axisym-metric flow past a linear array of three spheres. A finite-element method is used to solve the complete Navier-Stokes and heat transfer equations for the system parameter ranges 1 Re_d  200 (Reynolds number) 2 d_ij10 ( particle spacings)and 0. 1  prRe_d 2000 (Piclet number). The verified computer simulation results indicate that convection heat transfer parameters of interacting spherical particles deviate significantly from solitary spheres for all Reynolds and Piclet numbers.     

FUNDAMENTAL SOLUTIONS IN THE THEORY OF MICROMORPHIC ELASTIC SOLIDS WITH MICROTEMPERATURES

By means of elementary functions, the fundamental solutions of equations of equilibrium and steady oscillations of the theory of micromorphic elastic solids with microtemperatures are constructed, and basic properties are established.     

基于有效介质理论的积灰组件透射特性研究

该文对青海大学50 kW多功能光伏电站进行板面积灰采样,并利用X射线荧光分析技术对积灰进行元素分析,并依此求解积灰试样在0.3~0.7 μm波长范围内的等效折射率与吸收系数。根据有效介质理论将光伏组件表面的积灰等效为连续均匀的介质层,通过分析太阳光束在积灰组件各结构层的传输,确定了积灰对入射光的吸收、反射及透射情况。研究表明:积灰对入射光的吸收作用远大于反射作用,组件透射性能降低主要是积灰对光的吸收导致的。在积灰玻璃透射率试验中,测量值与计算值的绝对误差在0.002~0.087之间,表明模型对积灰组件有较好的实用价值。     

A CONSTITUTIVE THEORY FOR ANISOTROPIC HYGROTHERMOELASTICITY WITH FINITE ELEMENT APPLICATIONS

A constitutive theory for hygrothermoelasticity in anisotropic media is developed. The first and second laws of thermodynamics are extended to include moisture diffusion. The resulting equations are capable of fully coupling the deformation field with hygroscopic phenomena and temperature distributions. It is shown that, upon decoupling, the present theory reduces to the well-known equations of diffusion, heat conduction, and elasticity. With appropriate numerical schemes, the coupled equations can be applied to matrix-fiber composite structures subject to hygrothermal environments. As a step toward major numerical applications to aerospace and other structures, the present paper demonstrates one-dimensional finite element solutions. The results predicted by the theory appear to be quite satisfactory.     

A THERMOMECHANICAL MODEL OF SOLIDIFICATION ON A MOLD MOVING WITH CONSTANT VELOCITY

A thermomechanical model of pure metal solidification on a moving mold plate is considered. The goal of the model is to obtain a formula for the contact pressure at the shell/mold interface as the mold moves into the molten liquid. From the contact pressure it is possible to infer the effects of the mold velocity and the mold microgeometry on the time and location of gap nucleation which results from irregular distortion of the shell as it grows from the melt. The mold, which moves at a constant velocity into the molten liquid, has a sinusoidal surface with a low aspect ratio: this means that its wavelength greatly exceeds its amplitude. The mold is of infinite area and is assumed to be perfectly conducting and thermomechanically rigid. We therefore neglect the complexities associated with the physics of edge constraints and/or free boundaries of the solidifying shell and the interacting distortions between deformable mold and shell materials along their interface. The ratio of the velocity of the solid/liquid interface to the mold velocity is identified as another dimensionless parameter in the analysis. In order to arrive at an analytical solution for the contact pressure along the shell/mold interface, we assume that this parameter is small. This makes the velocity ratio a convenient perturbation parameter for the analysis of thermomechanical distortion of the thin shell material as it grows from the melt. This necessarily limits the analysis to situations where the mold moves at faster rather than slower speeds. It is assumed that there is zero tangential shear stress between the fluid and the solidifying shell. As the molten liquid flows over the mold, it perfectly wets the surface. This precludes wetting effects due to surface tension. A hypoelastic constitutive law, which is a rate formulation of thermoelasticity, is assumed to govern deformation of the shell as it grows from the molten liquid. Latent heat liberated at the freezing front is extracted across a constant contact resistance at the shell/mold interface. Peculiar fluid motion at the tip is neglected. A solution for the contact pressure that is valid near the liquid surface (i.e., the meniscus) is derived from the main theoretical developments. Beyond the time of gap nucleation at the shell/mold interface, the model is no longer valid since it cannot account for gross distortion of the shell (i.e., distortions that greatly exceed the spatial perturbations considered in the model).     

A THERMOMECHANICAL MODEL OF SOLIDIFICATION ON A PLANE WALL WITH A SINGLE ASPERITY OF ARBITRARY SHAPE

A thermomechanical model of solidification on a plane wall with a single asperity of arbitrary shape f(x), where x is measured along the wall, is presented. We shall assume that f(x