Thermal Stress Problem Research Articles

Transient Response of Thermoelastic Hollow Sphere Under Thermal Shocks

The thermoelastotransient response in a hollow sphere under different thermal shocks is analyzed. Coupled thermal stress and non-Fourier heat conduction are considered in the mathematic model. The systems of heat and motion equations are successfully uncoupled before Laplace transformation, and an analytic solution is given. By means of numerical Laplace inversion, the temperature and stress distributions are presented. From the numerical results from different thermal shocks, the influence of the impact speed to the coupled thermal stress problems can be observed. A comparison of temperature and stress distribution is given between the coupled thermal stress problems and static thermoelastic problems.

Icosahedral quasicrystals solids with an elliptic hole under uniform heat flow

The complex variable method for solving the two-dimensional thermal stress problem of icosahedral quasicrystals is stated. The closed-form solutions for icosahedral quasicrystals containing an elliptical hole subjected to a remote uniform heat flow are obtained. When the hole degenerates into a crack, the explicit solutions for the stress intensity factors is presented.

Improving the reliability of eutectic bonding vertical power light-emitting diodes by a Mo buffer layer

As a major step in the conduction of heat dissipation, wafer bonding significantly contributes to device reliability. This work presents the Cu–Sn eutectic bonding with a Mo buffer layer for light emitting diodes to increase its reliability. The conventional Ag-paste bonding and Cu–Sn bonding (without Mo top layer) are also studied for comparison. Their reliability is measured using thermal shock treatments ranging from − 40 to 120 °C (200 cycles). Experimental results indicate that the eutectic bonding with a Mo buffer layer demonstrates a better device performance than the other two counterparts. Following thermal shock treatment, the light droops for the Ag-paste, Cu–Sn, and Mo/Cu–Sn bonding samples are 15, 11 and 7%, respectively. Additionally, the increasing ratios of thermal resistance are 26, 33 and 19%, respectively. Moreover, adding the Mo buffer layer can relieve the thermal stress problem, owing to the thermal expansion mismatch in Gallium–Nitride/Cu–Sn/submount wafer bonding structures. • Eutectic bonding with a Mo buffer layer is investigated in Cu–Sn eutectic bonding. • Thermal shock treatments (− 40–120 °C, 200 cycles) were used to test reliability. • Light droop for the Ag-paste, Cu–Sn, and Mo/Cu–Sn bonding was ~ 15, 11 and 7%. • A Mo buffer layer can effectively relieve thermal stress.

Thermal Stress Analysis for Octagonal Quasicrystals

The complex variable method for solving the two-dimensional thermal stress problem of octagonal quasicrystals is stated. The closed-form solutions for octagonal quasicrystals containing an elliptical hole subjected to a remote uniform heat flow are obtained. When the hole degenerates into a crack, the explicit solutions for the stress intensity factors and energy release rate are presented.

Fundamental solution of thermal stress field in porous infinite media subjected to gas infiltration and heat transfer

When a porous solid is subjected to both gas infiltration and heat transfer, thermal stresses are generated in such a solid. In the previous reports, fundamental theory for a porous solid under such a complex situation was developed, and then a thermal stress problem for a porous solid with a flat boundary surface subjected to a concentrated loading was solved completely. In this study, thermal stress problem for a porous infinite solid subjected to a point loading is investigated. A method of solution based upon displacement potential and Fourier integral transform techniques is applied to solve the problem as well as the way used in the previous report. Complete closed form of gas pressure, solid temperature, displacement and thermal stress field in the infinite porous media are presented. It was found that the asymptotic behavior around a point load is strongly affected by gas permeability and pressure of gas phase.

A comparative study of the morphology and wetting characteristics of micro/nanostructured Cu surfaces for phase change heat transfer applications

A comparative study of oxidation methods to create Cu surfaces with controlled wettability is reported. Micro/nanostructures of Cu oxides are formed on Cu substrates using different chemical and thermal oxidation methods. The morphology and wetting characteristics of the resulting surfaces are characterized using atomic force microscopy, scanning electron microscopy, X-ray diffraction, and contact angle measurements. Chemical oxidation in alkali solutions can form uniform copper oxide layers with high roughness factors without causing thermal stress problems that often hamper thermal oxidation. By combining chemical oxidation with a hydrophobic coating, a wide range of wettability control is demonstrated from superhydrophilic ( < 10°) to superhydrophobic ( > 170°). Superhydrophilic CuO layers uniformly formed on Cu powder and Cu micropost wick surfaces lead to significant improvement in the capillary and heat transfer performance compared with comparable unoxidized Cu wicks. The present work motivates further studies to exploit the benefits of nanostructured Cu surfaces in various phase change heat transfer applications.

Three-Dimensional Temperature and Thermal Stress Analysis of an Inhomogeneous Layer

In this article we present a technique for analytical solution of three-dimensional heat-conduction and thermal-stress problems for an elastic layer whose thermophysical and mechanical properties are arbitrary functions of the transversal coordinate. This technique is based on direct integration of the original heat-transport and thermoelasticity equations and allows for reducing the original problems to solution of the governing Volterra integral equations of second kind. The obtained governing equations are solved by making use of the resolvent kernel.

Finite Elements Prediction of Temperature Field and Thermal Stresses in Thermal Roll of Calendering Process

A simplified numerical approach based on the Finite Element Method (FEM) to compute the steady state temperature field and thermal stresses in a thermal roll of a calender machine is proposed. The temperature distributions of the working roll and thermal oil were investigated by fluid dynamics theory. With the acquired roll body temperature, the deformation and stress were calculated. This approach is suitable for fluid-structural and thermal stress problems and hence helpful for the design and improvement of such equipment.

Some Results on Thermal Stress of Layered Plates and Shells by Using Unified Formulation

This work presents some results on two-dimensional modelling of thermal stress problems in multilayered structures. The governing equations are written by referring to the Unified Formulation (UF) introduced by the first author. These equations are obtained in a compact form, that doesn't depend on the order of expansion of variables in the thickness direction or the variable description (layer-wise models and equivalent single layers models). Classical and refined theories based on the Principle of Virtual Displacements (PVD) and advanced mixed theories based on the Reissner Mixed Variational Theorem (RMVT) are both considered. As a result, a large variety of theories are derived and compared. The temperature profile along the thickness of the plate/shell is calculated by solving the Fourier's heat conduction equation. Alternatively, thermo-mechanical coupling problems can be considered, in which the thermal variation is influenced by mechanical loading. Exact closed-form solutions are provided for plates and shells, but also the applications of the Ritz method and the Finite Element Method (FEM) are presented.

Non-axisymmetric thermal stress of a functionally graded coated circular inclusion in an infinite matrix

Abstract This paper is to study the non-axisymmetric two-dimensional problem of thermal stresses in an infinite matrix with a functionally graded coated circular inclusion based on complex variable method. With using the method of piece-wise homogeneous layers, the general solution for the functionally graded coating having radial arbitrary elastic properties is derived when the matrix is subjected to uniform heat flux at infinity, and then numerical results are presented for several special examples. It is found that the existence of the functionally graded coating can change interfacial thermal stresses, and choosing proper change ways of the radial elastic properties in the coating can obviously reduce the thermal stresses.

Thermal stresses of semi infinite Rectangular slab with internal heat source

The main purpose of this paper to solve three dimensional thermoelastic problem of thermal stresses of semi infinite rectangular slab with internal heat source to determine temperature distribution, thermal displacements stress functions, at any point of the rectangular slab with given boundary conditions by applying the finite Marchi-Fasulo integral transform and infinite Fourier cosine transform technique.

OS0801 中空円錐台の熱応力解析に関する一考察

OS0801 中空円錐台の熱応力解析に関する一考察

J042034 気体浸透と熱伝導を受ける多孔質体の基本解([J042-03]工業材料の変形と強度・解析)

When a porous solid is subjected to both gas infiltration and heat transfer, thermal stresses are generated in such a solid. In the previous reports, fundamental theory for a porous solid under such a complex situation was developed, and then a thermal stress problem for a porous solid with a flat boundary surface subjected to a concentrated point loading was solved completely. In this study, thermal stress problem for a porous infinite solid subjected to a point loading is investigated. A method of solution based upon displacement potential and Fourier integral transform techniques is applied to solve the problem as well as the way used in the previous report. Complete closed forms of gas pressure, solid temperature, displacement and thermal stress fields in the infinite porous media are presented.

Three-dimensional unsteady thermal stress analysis by triple-reciprocity boundary element method

Abstract The conventional boundary element method (BEM) requires a domain integral in unsteady thermal stress analysis with heat generation and/or an initial temperature distribution. In this paper, it is shown that the three-dimensional unsteady thermal stress problem can be solved effectively using the triple-reciprocity boundary element method without internal cells. In this method, the distributions of heat generation and initial temperature are interpolated using integral equations and higher order time-dependent fundamental solutions. A new computer program was developed and applied for solving several test problems.

Thermal stresses in an infinite circular cylinder

In the present paper, the problem of dynamic thermal stresses in an infinite elastic cylinder of radius a, with its axis along the z-axis, subject to certain boundary conditions, is studied. This type of situation can arise due to melting at constant rate of an insulating material at zero temperature deposited on the positive half of the infinite cylinder. A solution and numerical results are obtained for the stress components, displacement components, and temperature. Numerical results are given and illustrated graphically for each case considered.

Interfacial Thermal Stresses in Fiber Reinforced Composites

This article presents an analytic solution for the two-dimensional thermoelastic problem of interfacial thermal stresses in fiber reinforced composites. The solution is derived by superposing the solution for single fiber embedded in matrix successively. Study examples demonstrate the elegance and robustness of the present approach. Analysis results show that the effect of a single fiber is localized and there is an optimal elastic mismatch of fiber and matrix where the interfacial hoop stress is insensitive to the fiber packing arrangement and the fiber volume fraction.

Transient Thermal Stress Problem of a Functionally Graded Magneto-Electro-Thermoelastic Hollow Cylinder Due to a Uniform Surface Heating

This article is concerned with the theoretical analysis of the functionally graded magneto-electro-thermoelastic hollow cylinder due to uniform surface heating. We analyze the transient thermal stress problem for a functionally graded hollow cylinder constructed of the anisotropic and linear magneto-electro-thermoelastic materials using a laminated composite model as one of theoretical approximation under a plane strain state. As an illustration, we carry out numerical calculations for a functionally graded hollow cylinder constructed of piezoelectric and magnetostrictive materials and examined the behaviors in the transient state. We investigate the effects of the nonhomogeneity of material on the stresses, electric potential, and magnetic potential, and the effect of the applied electric potential on the thermal stress σθθ.

OS1718 スマート多層複合円板における非定常熱応力の制御

This paper discusses a control problem of a transient thermal stress in a smart multi-layer composite disk consisting of a transversely isotropic structural layer onto which piezoelectric layers of crystal 6mm are perfectly bonded. The first piezoelectric layer serves as a sensor and the other piezoelectric layers serve as an actuator. It is assumed that a number of electrodes are arranged concentrically on the upper surface of each actuator layer. When an unknown heating temperature distribution acts on the bottom surface of the composite disk, a transient electric potential distribution is considered to be measured on the upper surface of the sensor layer. The unknown heating temperature can be inferred from the measured electric potential. Then, voltages applied to all electrodes can be determined by optimization so that the maximum transient thermal stress in the structural layer is minimized subject to constrains on the stresses in the piezoelectric layers. Finally, numerical results are shown in a table.

OS1703 集光太陽放射を受ける組合せ平板の非定常熱伝導・熱応力問題

OS1703 集光太陽放射を受ける組合せ平板の非定常熱伝導・熱応力問題

On Thermal Stresses in Porous Solid under Gas Infiltration and Heat Transfer

When a porous solid is subjected to both gas infiltration and heat transfer, thermal stresses are generated in such a solid. This paper presents fundamental theory for a porous solid under such a complex situation. The governing equations for gas and solid phases are used to identify the gas pressure in pores and the solid temperature. The constitutive equation for a porous solid is formulated in terms of the unit cell model in which a pore exists periodically in the matrix. Using the constitutive equation, equilibrium equation of stress tensor and strain tensor obtained by differentiating displacement vector, the partial differential equation of displacement components for obtaining the deformation and stresses occurred in a porous elastic solid is introduced consequentially. As a simple example, the thermal stress problem for an infinite porous solid with a spherical cavity into which coolant gas is injected is considered.