• Journal of the Korean Society of Safety
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• v.14 no.1
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• pp.19-24
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• 1999

A two dimensional thermo elasto-plastic finite clement stress analysis was performed to study stress distributions in functionally gradient material. The upper $ZrO_2$ surface is heated at 1200K until a steady state is established and cooled at 300K. The influences on the thermal stress distributions due to the difference of compositional gradient exponent p were investigated. In this study, we obtained the thermal stresses are low for p=1.

• Journal of Welding and Joining
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• v.19 no.2
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• pp.221-227
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• 2001

Based on the principle of complementary energy, an analytical method is developed which focuses on the end effects for determining thermal stress distributions in a three-layered beam. This method gives the stress distributions which completely satisfy the stress-free boundary conditions. A numerical example is given in order to verify this method. The results show that the present analytical solutions have the values of stress in excellent agreement with the solutions derived by other investigators. Using this method, the effects of the thickness of bond coat on the thermal stresses of a typical sprayed thermal barrier coating, which consists of IN738LC substrate, MCrAIY bond coat and ZrO$_2$-8wt%Y$_2$O$_3$top coat, were investigated.

• Journal of Welding and Joining
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• v.23 no.1
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• pp.61-68
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• 2005

An analytical method for determining the thermal stress distributions in a 3-layered beam is developed, which is focused on the end effects. This method gives the stress distributions which satisfy the stress-free boundary condition at the end completely. For verification of the method, a numerical example which was introduced by other researchers is treated. The stress distributions agree with the results of other researchers. The results show that the show and peeling stresses at the interfaces are significant near the edge and become negligible in the interior region.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.842-846
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• 2005

A brake disk and a pad are important parts that affect the braking stability of a railway vehicle. Especially, because a brake disk stops the vehicle using conversion of the kinetic energy to frictional energy, thermal fatigue cracks are generated by the cyclic thermal load, as frictional heat, on a frictional surface and these cracks cause the fracture of a brake disk. Therefore, many researches for the thermal stress must be performed to improve the efficiency of brake disk and ensure the braking stability. In this study, we performed the thermal stress analysis for a ventilated brake disk with 3-D analysis model. For that, we simplified the shape of a ventilated hole to minimize problems that could be occurred in analysis process. Thermal stress analysis was performed in case that pressure distributions on a frictional surface is constant and is not. To determine pressure distributions of irregular case, pressure distribution analysis for a frictional surface was carried out. Finally using the results that were obtained through pressure distribution analysis, we carried out thermal stress analysis of each case and investigated the results of thermal stress analysis.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.68 no.1
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• pp.52-60
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• 2019

In this paper, four types of insulation coils were fabricated by adding various kinds of glycols to improve the flexibility and adhesion of insulating coils in varnish dispersed with PAI / Nano Silica_15wt%. The applied voltage and frequency were 1.5 kV / 20 kHz for accelerated life evaluation. Through the 6th temperature stress level, the cause of the insulation breakdown of the coil was ignored and only the breakdown time was measured. The Arrhenius model was chosen based on the theoretical relationship between chemical reaction rate and temperature for estimating the insulation life of the coil due to accelerated thermal stress. Three types of distributions (Weibull, Lognormal, Exponential) were selected as the relationship between thermal stress model and distribution. The average insulation lifetime was estimated under the temperature stress of four types of insulation coils through the relationship between one kind of model and three kinds of distributions.

• Bulletin of the Society of Naval Architects of Korea
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• v.9 no.2
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• pp.21-32
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• 1972

The problems of thermal stress and residual stress in resistance spot welding are studied from two standpoint namely, effect of temperature distributions and effect of the radius of free boundary. The radius of the region where the temperature distributions are occured is taken as a function of time after welding and as a finite size, 6 times of heated zone. The region of the radial stress distribution is treated as a function of time under Saint-Venant's principle and 6 or 12 times of originally heated zone. Thermal stresses and strains are obtained by analytic solution under constant mechanical properties and by the finite difference method for varing properties under temperature variation. From the computed results following conclusions are derived (1) For the engineering purpose, the region of temperature distribution and stress distribution can be treated as a finite region, $R=r_o=6r_e$ (2) If the maximum temperature of the aluminum alloy plate is less than $500^{\circ}F$, thermal stresses and strains can be obtained with constant mechanical properties. (3) The residual stresses and strains will be remained in welds and its vicinity.

• Journal of Welding and Joining
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• v.18 no.1
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• pp.104-109
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• 2000

Based on the principle of complementary energy, an analytical method is developed which focused on the end effects for determining thermal stress distributions in the clad beam. This method gives the stress distributions which completely satisfy the stress-free boundary condition at the edge. Numerical results shows that shear and peeling stress at the interface between the substrate and clad are significant near the edge and become negligible in the interior region. Even thought the relative location where the maximum or minimum stresses take place moves to interior as the length of the beam becomes smaller, the absolute location from the free end and the value of these stresses are the same in spite of the variation of the length of beam.

• Structural Engineering and Mechanics
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• v.57 no.5
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• pp.823-835
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• 2016

Using the Complementary Functions Method (CFM), a general solution for the one-dimensional steady-state thermal and mechanical stresses in a hollow thick sphere made of functionally graded material (FGM) is presented. The mechanical properties are assumed to obey the exponential variations in the radial direction, and the Poisson's ratio is assumed to be constant, with general thermal and mechanical boundary conditions on the inside and outside surfaces of the sphere. In the present paper, a semi-analytical iterative technique, one of the most efficient unified method, is employed to solve the heat conduction equation and the Navier equation. For different values of inhomogeneity constant, distributions of radial displacement, radial stress, circumferential stress, and effective stress, as a function of radial direction, are obtained. Various material models from the literature are used and corresponding temperature distributions and stress distributions are computed. Verification of the proposed method is done using benchmark solutions available in the literature for some special cases and virtually exact results are obtained.

• Proceedings of the KWS Conference
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• 2000.04a
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• pp.228-231
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• 2000

Based on the principle of complementary energy an analytical method is developed for determining thermal stress distribution in an thermal barrier coating. This method gives the stress distributions which satisfy the stress-free boundary conditions at the edge. Numerical examples are given in order to verify the method and to investigate the thickness effects of the ZrO$_2$-8wt％Y$_2$O$_3$ top coat on the integrity of thermal barrier coating consisted of IN738LC substrate and MCrAlY bond coat.

• Proceedings of the KWS Conference
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• 2004.05a
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• pp.223-225
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• 2004

Based on the principle of complementary energy an analytical method is developed for determining thermal stress distribution in an thermal barrier coating. This method gives the stress distributions which satisfy the stress-free boundary conditions at the edge. Numerical examples are given in order to verify the method and to investigate the thickness effects of the ZrO$_2$-8wt%Y$_2$O$_3$ top coat on the integrity of thermal barrier coating consisted of IN738LC substrate and MCrAlY bond coat.