THERMAL STRESSES AROUND TWO PARALLEL CRACKS IN AN INFINITE ORTHOTROPIC PLATE UNDER UNIFORM HEAT FLOW

Stress intensity factors around two parallel cracks in an infinite orthotropic plate have been determined. Uniform heat flows normally to the cracks. Thermal insulation is assumed on the surfaces of the cracks. The mixed boundary value conditions are reduced to dual integral equations using the Fourier transform technique. In order to solve the equations, the temperatures and displacements at the two cracks are expanded in a series of functions that are zero outside the cracks. The unknown coefficients in each series are solved by the Schmidt method. The stress intensity factors are calculated numerically for steel and ceramic-fiber-reinforced ceramics.     

THERMAL-ELASTO-PLASTIC ANALYSIS OF W-CU FUNCTIONALLY GRADED MATERIALS SUBJECTED TO A UNIFORM HEAT FLOW BY MICROMECHANICAL MODEL

Thermonuclear fusion process implementation has many material problems and one of them is related to the removal of impurities from plasma. In the International Thermonuclear Experimental Reactor (ITER), a divertor concept has been incorporated for this purpose. In this work, the development of a micromechanical model for functionally graded materials (FGMs) is presented and its application to thermal-elasto-plastic analysis is discussed for the case of the W-Cu FGMs for the ITER divertor plates. The model allows the prediction of basic properties of the FGM and computations of thermal stresses; and, in some limits, it may be used for pre-design evaluation of strain stress distributions and inelastic behavior. The model is found to be very useful at the first stages of graded materials design.     

THE DISTURBANCE OF A UNIFORM HEAT FLOW BY TWO LINE CRACKS IN AN INFINITE ANISOTROPIC THERMOELASTIC SOLID

Integral transform techniques are used to determine the stress intensity factors of a pair of colinear line cracks that disturb a uniform heat flow in an anisotropic thermoelastic solid that is under uniaxial tension. A solution is given for the case in which the tension is large enough to ensure that the cracks open fully.     

SOLUTION OF AN ELLIPTICAL RIGID INCLUSION WITH DEBONDINGS IN AN INFINITE PLANE UNDER THE UNIFORM HEAT FLUX

A problem of an elliptical rigid inclusion in an infinite plane subjected to uniform heat flux in an arbitrary direction and with a number of debondings on the interface of the elliptical rigid inclusion and the elastic matrix is solved. The rotation of the inclusion under the uniform heat flux is considered. The complex variable method is used, and the closed-form solution is obtained. The stress intensity of debonding at the debonding tips is calculated and the extension of debonding is investigated. Examples of stress distributions and resultant moments on the inclusion are shown for the inclusion with two debondings.     

THERMAL STRESSES DUE TO A UNIFORM HEAT FLOW PAST A CIRCULAR HOLE WITH A RADIAL EDGE CRACK

The problem solved in this paper is that of finding the stresses in a linear thermoelastic solid when a uniform heat flow is disturbed by the presence of an insulated circular hole with a radial edge crack. By using a Mellin transform technique the authors reduce the problem to a pair of singular integral equations, which are then solved numerically.     

WAVE PATTERN PRODUCED BY A HEAT SOURCE MOVING WITH CONSTANT VELOCITY ON THE TOP OF AN INFINITE PLATE

Within the framework of linear, isotropic elasticity theory the wave pattern produced by a heat source moving with constant velocity on the top of an infinite plate is computed. Both the transient effects associated with the initial conditions and the damping of the waves are neglected. If the travel speed of the heat source is smaller than the velocity of the surface waves, dispersive flexural waves will be excited. The frequency of these waves is proportional to the square of the wave number if the wavelength is much larger than the thickness of the sheet. In this limiting case it is found that the crest of the waves makes an angle of 90 degrees with the travel direction, and this result is independent of the travel speed as long as the parabolic approximation remains valid for the dispersion relation of flexural waves.     

ANALYSIS OF THERMAL STRESSES IN A FLAT PLATE SUBJECTED TO CONDUCTIVE HEAT TRANSFER WITH THERMAL BOUNDARY CONDUCTANCE

An analysis is presented of the effect of a finite boundary conductance on the magnitude of the thermal stresses in a flat plate subjected to symmetric and asymmetric conductive heat transfer from an infinite, mechanically noninteracting medium.     

REWETTING OF AN INFINITE SLAB WITH BOUNDARY HEAT FLUX

This paper deals with a numerical solution of the two-dimensional quasi-static conduction equation, governing conduction controlled rewetting of an infinitely long slab with one side flooded and the other side subjected to a constant heat flux. The solution gives the quench front temperature as a function of various model parameters such as Peclet number, Biot number, and dimensionless boundary heat flux. Also, the critical boundary heat flux is obtained by setting the Peclet number equal to zero, which gives the minimum heat flux required to prevent the hot surface being rewetted.     

THERMAL BUCKLING ANALYSIS OF INHOMOGENEOUS RECTANGULAR PLATE DUE TO UNIFORM HEAT SUPPLY

This paper is concerned with the thermal buckling analysis of an isotropic inhomogeneous rectangular plate subjected to the arbitrary thermal loads. The fundamental equations system is derived by introducing the technique of the newly defined position of the reference plane, which allows us to analyze the problem using an elementary plate theory. It is assumed that the material properties such as the coefficient of linear thermal expansion α, the thermal conductivity λ, and Young's modulus of elasticity, E, are changed in the thickness direction with the power law of the coordinate variable, whereas Poisson's ratio ν is assumed to be constant. As an illustrative example, we consider the thermal buckling problem of a simply supported inhomogeneous rectangular plate due to uniform heat supply. Numerical calculations are carried out for several cases taking into account the variations of the inhomogeneous material properties, aspect ratio, and width-to-thickness ratio.     

THERMAL STRESSES IN AN INFINITE PLATE WITH TWO ROWS OF HOLES

Abstract

A theoretical method is presented for a two-dimensional, steady thermoelastic problem of perforated plates with two rows of holes. The analysis is developed by the complex variable approach. The numerical results for stress concentration factors are given in the form of curves for a wide range of diameter/pitch. The extension of the present method to holes of arbitrary shape, number, and array is quite straightforward.     

EDGE-CRACKED PLATE WITH ONE FREE AND ONE CONSTRAINED BOUNDARY SUBJECTED TO SUDDEN CONVECTIVE COOLING

The transient thermal stress edge crack problem for an elastic strip with free and fully constrained boundaries is considered. The plate is suddenly subjected to convective cooling on the face containing the edge crack while the other face is insulated. The solution of the problem is obtained by using the superposition technique results in a singular integral equation that is solved numerically. The results of the transient temperature and thermal stress distributions in the uncracked strip are presented. Also, numerical results are obtained for the stress-intensity factor in terms of the Fourier number, crack length, and different values of the Biot number.     

THERMAL STRESSES IN A CIRCULAR CYLINDER WITH A CIRCUMFERENTIAL EDGE CRACK UNDER UNIFORM HEAT FLOW

The linear thermoelastic problem of an infinitely long circular cylinder with a circumferential edge crack is solved. The thermal stresses are caused by a uniform heat flow disturbed by the presence of the crack. The crack surfaces and the cylindrical surface are assumed to be insulated. Integral transform techniques are used to reduce the problem to that of solving two singular integral equations of the first kind. The equations are solved numerically, and the variation of the stress intensity factor with the crack depth is shown graphically.     

STRESS DISTRIBUTION IN AN ELASTIC PLASTIC DISK SUBJECTED TO A CIRCULAR HEAT SOURCE

Stress distribution in a perfectly plastic disk caused by a circular heat source of constant output is investigated. It is shown that, dependent on the ratio of the radius of the disk to the radius of the heat source, Tresca's yield condition assumes different forms. In certain cases, the plastic zone is composed of two parts associated with different branches of the yield condition. The critical time for avoiding secondary plastic flow is discussed.     

倾斜平板热面朝上自然对流换热实验研究

对不同倾斜角度的平板在空气中的自然对流换热系数进行了实验测量.采用直接电加热方法对倾斜平板进行加热,在倾斜铜板背面嵌人式布置热电偶测量平板表面平均温度,同时测量电加热时的电压及电流.实验结果表明,随着倾斜表面与空气温差的增加,实验得到的平均努谢尔特数与经典的准则关联式得到的努谢尔特数呈现不同的变化趋势;随着倾斜角度的增加自然对流换热得到了强化,而且当倾斜平板趋于水平或者竖直时实验结果与经典准则关联式的计算结果偏差逐渐增大,最大偏差达到51%.     

HYGROTHERMAL STRESS IN A PLATE SUBJECTED TO ANTISYMMETRIC TIME-DEPENDENT MOISTURE AND TEMPERATURE BOUNDARY CONDITIONS

When the temperature and/or moisture at the surfaces of a composite change suddenly, stresses will arise in the composite owing to the nonuniform diffusion of heat and moisture. Recent investigations have shown that under certain conditions the classical uncoupled theory of diffusion can significantly underestimate the coefficient of diffusion. The coupling between heat and moisture is an inherent part of the diffusion process that cannot be neglected on intuitive grounds. This investigation is an inquiry into the influence of antisymmetric boundary conditions on the magnitude of the hygrothermal stresses in a plate made of T300/5208 epoxy material, commonly used in graphite fiber-reinforced composites. Both moisture and temperature boundary conditions are considered. Because of the nonlinear character of the coupled equations, a finite-difference scheme is adopted. Numerical results involving time-dependent moisture, temperature, and stress distributions in the plate are displayed graphically; they show that the stresses derived from the coupled theory differ appreciably from the uncoupled results, both qualitatively and quantitatively. The hygrothermal stresses with coupling taken into account acquire an oscillatory character when the temperature on the plate is raised suddenly; this factor could contribute to material damage. In addition, antisymmetric boundary conditions can either raise or lower the stress levels, depending on time and the transient nature of the applied temperature.     

NUMERICAL ANALYSIS OF FLUID FLOW AND HEAT TRANSFER CHARACTERISTICS IN THREE-DIMENSIONAL PLATE FIN-AND-TUBE HEAT EXCHANGERS

This numerical study provides three-dimensional (3-D) time-dependent modeling of unsteady laminar flow and heat transfer over single- and multirow plate fin-and-tube heat exchangers. The complex nature of the flow field featuring a horseshoe vortex is investigated for both configurations. The time-dependent evolution of the horseshoe vortex mechanism on the forward part of the tube and its journey to the rear of the tube are studied to provide fundamental information on the local flow structure and the corresponding heat transfer characteristics. The effects of various governing parameters, such as fin spacing, Reynolds number, tube row number, and tube arrangement, on the heat transfer and flow characteristics are also studied for the Reynolds number range investigated. It is found that the local flow structure including formation and evolution of vortex systems and singular-point interactions correlates strongly with the heat transfer characteristics. The numerical results for the integral heat transfer parameters agree well with available experimental measurements.     

GENERALIZED THERMOELASTICITY IN AN INFINITE SOLID WITH A HOLE

This paper deals with one-dimensional generalized thermoelasticity based on the theories of Lord and Shulman and of Green and Lindsay. A formulation of generalized thermoelasticity that combines both generalized theories is derived. The generalized thermoelastic problems for an infinite solid with a cylindrical hole and an infinite solid with a spherical hole are analyzed by means of the Laplace transform technique. Numerical calculations for temperature, displacement, and stresses under the generalized formulation are carried out and compared with those of classical dynamic coupled theory.     

THERMOELASTIC VIBRATIONS OF A LAMINATED RECTANGULAR PLATE SUBJECTED TO A THERMAL SHOCK

In this work the response of a rectangular, simply supported, symmetrically laminated, cross-ply composite plate subjected to a thermal shock is developed. The analysis includes the interaction between the strain and temperature fields and investigates the effect of accounting for the orthotropic material properties in the governing elastic and thermal equations. The resulting solution for the vibration of the plate is compared to a previous analysis of a homogeneous, isotropic, rectangular plate. Comparison indicates that while the solutions have similar forms, there are two key quantitative differences between them.     

TRANSIENT THERMOELASTIC PROBLEM FOR AN INFINITE PLATE CONTAINING A PENNY-SHAPED CRACK AT AN ARBITRARY POSITION

This article deals with the transient thermoelastic problem for an infinite plate containing a penny-shaped crack that is parallel to the surfaces of the plate but at an arbitrary position of the plate. The transient thermal stresses are set up by the heat generation on the surfaces and the sudden heat exchange on the surfaces. By using the finite difference method for the time variable, the analytical solution for spatial variables can be obtained. The numerical results for the temperature and stress intensity factor are obtained, and results are shown in graphs.