• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.04a
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• pp.9-12
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• 2004

In this study, we investigated about electrooptics characteristic of three kind of TN cell on the polyimide surface. Monodomain alignments of thermal stressed TN cell over temperature of liquid crystal isotropic phase were almost same that of no thermal stressed TN cells. However, the thermal stressed TN cell have many defects. Also, threshold voltage and response time of thermal stressed TN cells show same performances of no thermal stressed TN cells. There were little changes of value in these TN cells. However, transmittances of TN cells on the polyimide surface decrease with increasing thermal stress time. Finally, the residual DC voltage of the thermal stressed TN cell on the polyimide surface show decrease of characteristics as increasing thermal stress time. Therefore, thermal stability of TN cell was decreased by high thermal stress for the long times.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05a
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• pp.177-180
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• 2005

We have investigated electro-optical characteristics in three kinds of TN cells on the polyimide surface. Transmittance of no thermal stressed TN cells were better than that of thermal stressed TN cells. Also. the threshold voltage and the response time of thermal stressed TN cells were same that of no thermal stressed TN cells. There were little change of value in these TN cells. On the other hand. transmittances of TN cells on the polyimide surface decreased by increasing thermal stress time. Moreover. the residual DC of the thermal stressed TN cells on the polyimide surface showed the characteristics of thermal stressed TN cells were weakened as increasing thermal stress temperature and time. Therefore. thermal stability of TN cells were decreased gradually by giving high thermal stress for a long time.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.2
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• pp.92-98
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• 2001

We determined the transfer coefficient through the analysis of three dimensional temperature distribution in comparison with the measured temperature on the piston in the turbocharged diesel engine. And we analyzed the thermal stress and the thermal deformation with that heat transfer coefficient by using finite element method. According to this results, we found that maximum tempetature range of the piston appeared at the upper part of the piston crown and that the heat transfer coefficient of the upper part of the piston is smaller than that of the lower one. It showed that the maximum thermal deformation is shown at the edge of the upper part of piston and that the maximum thermal stress was shown on the lower part of the piston crown. Finally, we defined the method of determination of a piston heat transfer analysis by using measured temperature on the piston and analyzed temperature with finite element method.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10b
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• pp.1181-1186
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• 2000

The crack of concrete induced by the heat of hydration is a serious problem, particularly in concrete structures such as biers, thick walls, box type walls, mat-slab of nuclear reactor buildings, dams or foundations of high rise buildings, etc.. As a result of the temperature rise and restriction condition of foundation, the thermal stress which may induce the cracks can occur. Therefore the various techniques of the thermal stress control in massive concrete have been widely used. One of them is prediction of the thermal stress, besides low-heat cement which mitigates the temperature rise, design change which considers steel bar reinforcement, operation control and so on. In this study, firstly it introduce the thermal cracks control technique by employing low-heat cement concrete, thermal stress analysis considering season. Secondly it shows the application of the cracks control technique like block placement.

• 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.

• Journal of the Korean Society for Precision Engineering
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• v.30 no.8
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• pp.802-808
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• 2013

Thermal barrier coating (TBC) is used to protect substrates and extend the operating life of gas turbines in power plant and aeronautical applications. The major causes of failure of such coatings is spallation, which results from thermal stress due to a thermal expansion coefficient mismatch between the top coating and the bond coating layers. In this paper, the effects of the material properties and the thickness of the top coating layer on thermal stresses were evaluated using the finite element method and the equation for the thermal expansion coefficient mismatch stress. In addition, we investigated a design technique for the top coating whereby thermal resistance is exploited.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.287-288
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• 2005

In this study, we have investigated electro-optical characteristics of thermal and UV stressed TN cells on the rubbed polyimide surface. Mono-domain alignments of thermal stressed TN cells over temperature of liquid crystal isotropic phase were almost same that of no thermal stressed TN cells. Also, threshold voltage and response time of thermal stressed TN cells were same that of no thermal stressed TN cells. Finally, the residual DC voltage of the thermal stressed TN cell on the polyimide surface show decrease of characteristics as increasing thermal stress time. Therefore, thermal stability of TN cell was decreased by high thermal stress for the long times.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.498-501
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• 2004

In this study, the threshold voltage and the response time of thermal stressed TN-LCDs showed the same performances on no thermal stressed TN-LCDs. There was little change of value in TN cells. Also, the transmittances of TN-LCDs on the rubbed PI surface were almost same while increasing thermal stress time. However, the thermal stability of TN cell was decreased by the high thermal stress for the long duration. Residual DC was decreased as the thermal stress increases. Especially, when TN cell was stressed more and more by heating, residual DC was changed a lot. As a result, the residual DC property of LCD in projection TV is affected very much by heating.

• Journal of the korean Society of Automotive Engineers
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• v.12 no.3
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• pp.41-52
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• 1990

In this study are determined the unsteady temperature and thermal stress fields for a domestic 4-cylinder, 4-cycle gasoline engine cylinder head by the three-dimensional finite element method. A representative part of the cylinder head is modelled as a combination of hexahedron isoparametric elements, and the time-dependent temperature and the heat transfer coefficient of the gas are imposed as the thermal boundary conditions for the engine speeds of 500 rpm and 2000 rpm. The obtained results, which are represented graphically, indicate that the amplitudes of temperature fluctuation during a cycle are about 10.deg. C and 3.deg. C respectively on the surface of combustion chamber, and the maximum temperature fields occur at 30.deg. , 10.deg. respectively before the initiation of the exhaust stroke. Thermal stress fields due to non-uniform temperature distributions show that compressive stress is much larger than tensile stress throughout a cycle. It is also found that the compressive stress varies with substantial amplitude between the exhaust port and ignition plug hole, and the high tensile stress with small fluctuation occurs between exhaust port and the adjacent head bolt hole.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.3
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• pp.15-22
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• 2008

Applications of bonded dissimilar materials such as integrated circuit(IC) packages, ceramics/metal and resin/metal bonded joints, are very increasing in various industry fields. It is very important to analyze the thermal stress and stress singularity at interface edge in bonded joints of dissimilar materials. In order to investigate the IC package crack propagating from the edge of die pad and resin, the fracture parameters of bonded dissimilar materials and material properties are obtained. In this paper, the thermal stress and its singularity index for the IC package were analyzed using 2-dimensional elastic boundary element method(BEM). From these results, crack propagation direction and path by thermal stress in the IC package were numerically simulated with boundary element method.