Three-dimensional Thermal Stress Analysis Research Articles

Thermal–mechanical–electrical co-simulation of electron gun using finite element method

As the central component of the traveling wave tube (TWT), the thermal deformation of the electron gun is a critical concern. This paper presents a method for analyzing the electromagnetic characteristics of electron gun after thermal deformation. The method adopts multiple grid acceleration technology. Based on this method, a three-dimensional thermal stress analysis tool called the Thermal Stress Simulator (TSS) is developed. In addition, the TSS can be seamlessly coupled with the Thermal Simulator (TS) and the Electron Optical Simulator (EOS) previously developed by our team to realize the analysis of electromagnetic characteristics changes after thermal deformation and provide support for the reliable design of TWT.

Three-dimensional thermal-stress analysis of transversely isotropic double-layer plate based on Green's function

Using the potential theory and the mirror-image method, the three-dimensional (3D) Green's function solutions for a double-layer transversely isotropic thermoelastic plate with varying thickness were obtained for the first time. The exact 3D explicit closed analytical forms of the temperature and thermal-stress fields were expressed by simple functions. These forms can be used to accurately calculate the full-field distribution under heat source, which is suitable for plates with a wide range for thickness—particularly for ultrathin coating plates. Results for numerical examples indicated that the coating thermal parameters, coating stiffness, and coating thickness ratio significantly affect the temperature increment and stress field. The influence rules of key parameters obtained in this study can guide the design of double-layer plates in thermal environments.

Comparison of approximation schemes for three-dimensional thermal stress analysis and applications to cracks with fluid flowing

In this paper, we first present an approximate scheme for thermal problem with heat sources varying with time (time-varying). It is different from one that the authors used previously. Both schemes use series of stepwise constant heat sources to approximate the continuously varying heat source. But the constant sources of the two schemes are different. The previous scheme divides the time period from the initial time to the solution time, at which the solutions are sought, into some time-steps and assumes that each of the series of constant sources is applied at the start time of the time-steps and all the constant sources last to the solution time. The new scheme assumes that each of the constant sources starts at the start time of a time-step but lasts only for one step of time. When solutions for temperature, displacement and stress are sought at multiple time instants or the boundary conditions are obtained step by step from other problems, it is easier and computing efficient to use the new scheme. If the solution is required at just one time instant, then computations of the two schemes are basically the same. The schemes are compared for the thermal effects caused by time-varying temperature on surface of a spherical cavity in an infinite body and the results of the two schemes agree very well. Comparison of the two schemes is also done for the temperature change in rock due to fluid flowing through a fracture inside the rock.

Experimental and numerical investigation on gas turbine blade with the application of thermal barrier coatings

The engine parts material used in gas turbines (GTs) should be resistant to high-temperature variations. Thermal barrier coatings (TBCs) for gas turbine blades are found to have a significant effect on prolonging the life cycle of turbine blades by providing additional heat resistance. This work is to study the performance of TBCs on the high-temperature environment of the turbine blades. It is understood that this coating will increase the lifecycles of blade parts and decrease maintenance and repair costs. Experiments were performed on the gas turbine blade to see the effect of TBCs in different combinations of materials through the air plasma method. Three-layered coatings using materials INCONEL 718 as base coating, NiCoCrAIY as middle coating, and La2Ce2O7 as the top coating was applied. Finite element analysis was performed using a two-dimensional method to optimize the suitable formulation of coatings on the blade. Temperature distributions for different combinations of coatings layers with different materials and thickness were studied. Additionally, three-dimensional thermal stress analysis was performed on the blade with a commercial code. Results on the effect of TBCs shows a significant improvement in thermal resistance compared to the uncoated gas turbine blade.

Development of Three-dimensional Thermal Stress Analyses Software using XFEM

Development of Three-dimensional Thermal Stress Analyses Software using XFEM

Three-dimensional thermal stress analysis of the re-oxidized Ni-YSZ anode functional layer in solid oxide fuel cells

Nickel-yttria-stabilized zirconia (Ni-YSZ) cermet is widely used as an anode material in solid oxide fuel cells (SOFCs); however, Ni re-oxidation causes critical problems due to volume expansion, which causes high thermal stress. We fabricated a Ni-YSZ anode functional layer (AFL), which is an essential component in high-performance SOFCs, and re-oxidized it to investigate the related three-dimensional (3D) microstructural and thermo-mechanical effects. A 3D model of the re-oxidized AFL was generated using focused ion beam-scanning electron microscope (FIB-SEM) tomography. Re-oxidation of the Ni phase caused significant volumetric expansion, which was confirmed via image analysis and calculation of the volume fraction, connectivity, and two-phase boundary density. Finite element analysis (FEA) with simulated heating to 500–900 °C confirmed that the thermal stress in re-oxidized Ni-YSZ is concentrated at the boundaries between YSZ and re-oxidized NiO (nickel oxide). NiO is subjected to more stress than YSZ. Stress exceeding the fracture stress of 8 mol% YSZ appears primarily at 800 °C or higher. The stress is also more severe near the electrolyte-anode boundary than in the Ni-YSZ cermet and the YSZ regions. This may be responsible for the electrolyte membrane delamination and fracture that are observed during high-temperature operation.

Three-dimensional thermal stress analysis using the indirect BEM in conjunction with the radial integration method

Thermal stress analysis is one of key aspects in mechanical design. Based on the indirect boundary integral equation (BIE) and the radial integration method (RIM), this paper develops a boundary-only element method for the boundary stress analysis of three-dimensional (3D) static thermoelastic problems. A transformation system constructed with the normal and two special tangential vectors is used to regularize the singularity in the indirect BIE. The RIM is then employed to transform the domain integrals arising in both displacement and its derivative integral equations into the equivalent boundary integrals, which results in a pure boundary discretized algorithm. Several numerical experiments are provided to verify the accuracy and convergence of the present approach.

Three-dimensional thermal stress analysis of laminated composite plates with general layups by a sampling surfaces method

Abstract A paper focuses on the application of the method of sampling surfaces (SaS) to three-dimensional (3D) steady-state thermoelasticity problems for orthotropic and anisotropic laminated plates subjected to thermal loading. This method is based on selecting inside the n th layer I n not equally spaced SaS parallel to the middle surface of the plate in order to choose temperatures and displacements of these surfaces as basic plate variables. Such an idea permits the presentation of the proposed thermoelastic laminated plate formulation in a very compact form. It is worth noting that the SaS are located inside each layer at Chebyshev polynomial nodes that leads to a uniform convergence of the SaS method. As a result, the SaS method can be applied efficiently to the 3D stress analysis of cross-ply and angle-ply composite plates with a specified accuracy utilizing the sufficient number of SaS.

Thermal stress analysis on laser cross scribe of glass

In CO2 laser scribe processing of glass, an initial crack on the start edge of the glass is indispensable. When carrying out laser cross scribe, there is no initial crack on the edge of the first scribed line. However, the second scribing progresses across the first scribed line. In this research, in order to clarify the phenomena of laser cross scribe, the laser irradiation experiments were carried out at various velocities of the second scribing. Using the same conditions as the experiments, three-dimensional thermal stress analyses were conducted by a finite element method. As a result, two kinds of forms were found in the progresses of the second scribing. One is a form that the first scribed crack surfaces are bonded by strong compression at high temperature in the heating area during the second scribing. The other is a form that the tensile stress in the cooling area which makes the second scribing progress is transmitted by the frictional force generated in the first scribed crack surface. Consequently the second scribing progresses across the first scribed line although there is no initial crack on the edge of the first scribed line.

Three-dimensional thermal stress analysis of the mould during high-speed casting of steel

On the basis of the calculated mould temperature, a three-dimensional thermal stress model of the mould is established. A corresponding finite element method program is developed with six-face and eight-node isoparameter elements. The Newton method is used to solve the stress equations. Making using of the stress model, the thermal distortion and stress distribution of the mould are obtained when the thickness of the mould wall is different. Experimental data have been used to validate the model. From the result, it is proved that the mould stress is less than its yield strength and does not result does in residual deformation.

Thermal Stress Analysis on Laser Cross Scribe of Glass

In CO2 laser scribe processing of glass, an initial crack on the start edge of the glass is indispensable. When carrying out laser cross scribe, there is no initial crack on the edge of the first scribed line. However, the second scribe progresses across the first scribed line. In this research, in order to clarify the phenomena of laser cross scribe, the laser irradiation experiments were carried out at various velocities of the second scribing. Using the same conditions as the experiments, three-dimensional thermal stress analyses were conducted by a finite element method. As a result, two kinds of forms were found in the progresses of the second scribe. One is a form that the first scribed crack surfaces are bonded by strong compression at high temperature in the heating area during the second scribing. The other is a form that the tensile stress in the cooling area which makes the second scribe progress is transmitted by the frictional force generated in the first scribed crack surface. Consequently the second scribe progresses across the first scribed line although there is no initial crack on the edge of the first scribed line.

Three-dimensional thermal stress analysis on laser scribing of glass

In the laser scribing of glass a thermal stress is introduced into a glass plate by means of CO2 laser irradiation. The glass plate is rapidly cooled down by water jet immediately after the irradiation. For the purpose of theoretical clarification of the factors ruling the scribable condition and the crack depth, scribable conditions were acquired in laser irradiation experiments using a soda-lime glass plate having a thickness of 0.7 mm. Furthermore, the crack depth and the crack profile were observed for various values of the distance between the heating area and the cooling area. On the basis of the scribable conditions obtained from the experiments, a three-dimensional thermal stress analysis was conducted by a finite element method, allowing the following findings to be obtained. The scribable condition can be estimated from the maximum surface tensile stress in the cooling area and the maximum surface temperature. The crack depth in laser scribing depends on the surface tensile stress in the cooling area and the compressive stress field immediately under that area.

Three Dimensional Thermal Stress Analysis on Laser Scribing of Glass

Abstract In the laser scribing of glass a thermal stress is introduced into a glass plate by means of CO 2 laser irradiation. The glass plate is rapidly cooled down by water jet immediately after the irradiation. For the purpose of theoretical clarification of the factors ruling the scribable condition and the crack depth, scribable conditions were acquired in laser irradiation experiments using a soda-lime glass plate having a thickness of 0.7 mm. Furthermore, the crack depth and the crack profile were observed for various values of the distance between the heating area and the cooling area. On the basis of the scribable conditions obtained from the experiments, a three-dimensional thermal stress analysis was conducted by a finite element method, allowing the following findings to be obtained. The scribable condition can be estimated from the maximum surface tensile stress in the cooling area and the maximum surface temperature. The crack depth in laser scribing depends on the surface tensile stress in the cooling area and the compressive stress field immediately under that area.

909 一般化された熱弾性理論による部分加熱を受ける平板の熱応力解析(OS-5 非定常熱弾性,非弾性,相変態,研究発表講演)

The classical thermoelastic theory is the theory that the propagation speed of a heat wave is infinite and that its wave reach an infinite distance instantly. On the other hand, the generalized thermoelastic theory is the theory that its speed is finite and that are considered the relaxation time introduced into classical thermoelastic theory. This paper deals with the three-dimensional thermal stress analysis in the plate subjected to partial heating based on the generalized thermoelastic theory, Lord-Shulman and Green-Lindsay theory. When the solutions of the differential equations are searched, Laplace transform is carried out about time variable and Fourier transform is carried out about space variable. And the temperature and thermal stresses are asked by using a state space approach.

Thermal stress analysis and homogenization for catalytic combustor monoliths

We present a simple and rigorous mathematical model and efficient numerical algorithm for the three-dimensional thermal stress analysis of composite structures used in high-temperature catalytic combustors. Numerical experiments are carried out for three types of cell geometries. A homogenization algorithm is implemented, and asymptotic formulae are derived for the effective elastic moduli of the periodic structures.

Three-Dimensional Thermal Stress Analysis under Steady State with Heat Generation by Boundary Element Method

The boundary element method (BEM) does not require a domain integral in steady-state thermoelastic problems without heat generation. However, with heat generation, the domain integral is necessary. This paper shows that the three-dimensional problem of steady-state thermoelasticity with nonuniform heat generation can be easily solved without a domain integral by means of the boundary element method. This method can also be applied to steady-state thermal stress problems under generally complicated heat generation. However, in this case, the domain must be divided into small areas, where distributions of heat generation satisfy the Laplace equation.

複合材料の三次元熱応力解析

A computer program for three-dimensional thermal stress analysis of anisotropic materials such as composites has been developed. As an example, the deformations of bi-metal and angle- ply laminates under thermal conditions were analyzed. From the computational results, the torsional phenomenon, which is caused by the coupling and the effect of free edge on stress, was recognised. When the residual stress is taken into consideration, the tensile strength of angle-ply laminates was also analyzed. The effect of property of matrix on the tensile strength of angle-ply laminate was investigated. As a results, it was shown that the fracture pattern can be changed by property of matrix.

Three-Dimensional Thermal Stress Analysis under Steady State with Heat Generation in the Region by Boundary Element Method.

The boundary element method (BEM) does not require a domain integral for steady thermoelastic problems without heat generation. However, with heat generation, the domain integral is necessary. This paper shows that the three-dimensional problem of steady thermoelasticity with nonuniform heat generation over the region can be easily solved without a domain integral by means of the boundary element method. This method can also be applied to steady thermal stress problems under general complicated heat generation. However, for general heat generation the domain must be divided into small areas, where distributions of heat generation satisfy the Laplace equation.

Elastic constant matrix required for thermal stress analysis of bulk single crystals during Czochralski growth

The elastic constant matrix of cubic single crystals such as GaAs and InP which are used in electronic and optical devices is required in the thermal stress analysis of their bulk single crystals during the Czochralski growth. In this paper, the components of this matrix are expressed in terms of an arbitrary Cartesian coordinate system and a cylindrical coordinate system. They depend on the azimuthal component of the cylindrical coordinate system and the terms containing the azimuthal coordinate cannot be neglected even in approximate sense. Strictly speaking, a three-dimensional thermal stress analysis may be required for those single crystals instead of an axisymmetric analysis.

Three Dimensional, Thermal Stress Analysis of a Welded Plate by the FEM

A general numerical model for simulating three-dimensional thermal stress analysis has been developed which uses the Finite Element Method (FEM). The analysis can be uncoupled to solve either the heat transfer problem or the stress problem independently and it can accommodate nonlinear material behaviour, initial states of stress and strain, and moving boundary conditions. A unique feature of the model is that it properly accounts for the latent heat effect during phase changes. Applying the moving heat flux boundary condition to simulate arc welding, the model has been used to predict the transient thermal mechanical response of a welded plate.