Estimation of Thermal Shock Resistance of Ceramics. (2nd Reprt. Heat Transfer Coefficient and Thermal Stress at Quenching in Liquid Sodium).

Abstract In present the study, sudden cooling, in other words thermal shock, is applied to a plate that is originally a functionally graded material (FGM). The flat plate is assumed to have an edge crack on it. Hence a numerical couple-field analysis is performed on the plate. The FGM is a combination of Ni and Al2O3. The thermal and mechanical properties of the FGM are assumed to depend on temperature variation. The mixing percentages of the Ni and Al2O3 throughout the plate are considered to vary (i) linearly, (ii) quadratically and (iii) in half-order. In order to solve the problem, a new subroutine depending on temperature is written using APDL (ANSYS Parametric Design Language) codes. Three values of the heat transfer coefficient are applied to the initially heated plate. As a result, the transient temperature variation and stress intensity factor are presented to show the thermo-mechanical relation of the plate. The material properties changing with temperature results in more reliable temperature values. Increasing the heat transfer coefficient results in better cooling and in a lesser amount of time to reach ambient air temperature.

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Thermal Stress and Heat Transfer Coefficient for Ceramics Stalk Having Protuberance Dipping into Molten Metal

Journal of Solid Mechanics and Materials Engineering ◽

10.1299/jmmp.4.1198 ◽

2010 ◽

Vol 4 (8) ◽

pp. 1198-1213 ◽

Cited By ~ 1

Author(s):

Nao-Aki NODA ◽

Hendra ◽

Wenbin LI ◽

Yasushi TAKASE ◽

Hiroki OGURA ◽

...

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Thermal Stress ◽

Transfer Coefficient ◽

Molten Metal

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Improvement on Thermal Shock Resistance of Ceramic Components by Using Self-Healing

ASME 2010 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, Volume 2 ◽

10.1115/smasis2010-3643 ◽

2010 ◽

Author(s):

Wataru Nakao

Keyword(s):

Thermal Stress ◽

High Temperature ◽

Thermal Shock ◽

Stress Fracture ◽

Thermal Shock Resistance ◽

Self Healing ◽

Quenching Rate ◽

Ceramic Components ◽

Shock Resistance ◽

Quenching Method

Availability of self-healing on the thermal shock resistance of ceramic components was investigated. Using gas quenching method, the crack-healed alumina-18 vol% SiC composite, which has excellent self-healing ability, was applied to thermal shock of the arbitrary quenching rate. The procedure could give rise to the thermal stress fracture at high temperature. The critical quenching rate at thermal stress fracture of the healed specimen was found to be 6.47 K/s, corresponding to the thermal stress of 452.3 MPa. Alternatively, that of the cracked specimen was found to be 5.02 K/s, corresponding to the thermal stress of 350 MPa. From the obtained results, usage of self-healing was confirmed to improve extremely thermal shock resistance. The present result suggests that usage of self-healing gives a large advantage to design the high temperature ceramic components, because the mechanically reliable design and thermal shock resistance cannot coexist due to low thermal conductivity.

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EFFECTS OF THERMAL ENVIRONMENTS ON THE THERMAL SHOCK RESISTANCE OF ULTRA-HIGH TEMPERATURE CERAMICS

Modern Physics Letters B ◽

10.1142/s021798490801608x ◽

2008 ◽

Vol 22 (14) ◽

pp. 1375-1380 ◽

Cited By ~ 6

Author(s):

WEIGUO LI ◽

DAINING FANG

Keyword(s):

Heat Transfer ◽

High Temperature ◽

Thermal Shock ◽

Thermal Shock Resistance ◽

Thermal Environment ◽

Transfer Condition ◽

Ultra High Temperature Ceramics ◽

Thermal Environments ◽

Shock Resistance ◽

Ultra High Temperature

In the present study, the temperature-dependent thermal shock resistance parameter of Ultra-High Temperature Ceramics (UHTCs) was measured based on the current evaluation theories of thermal shock resistance parameters, since the material parameters of UHTCs are very sensitive to the changes of temperature. The influence of some important thermal environment parameters on the thermal shock resistance and critical temperature difference of rupture of UHTCs were studied. By establishing the relation between the temperature and the thermal or mechanical properties of the UHTCs, we found that thermal shock behavior of UHTCs is strongly affected by the surface heat transfer coefficient, heat transfer condition and initial temperature of the thermal shock.

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Online Fatigue-Monitoring Models with Consideration of Temperature Dependent Properties and Varying Heat Transfer Coefficients

Science and Technology of Nuclear Installations ◽

10.1155/2013/763175 ◽

2013 ◽

Vol 2013 ◽

pp. 1-9 ◽

Cited By ~ 2

Author(s):

HengLiang Zhang ◽

Shi Liu ◽

Danmei Xie ◽

Yangheng Xiong ◽

Yanzhi Yu ◽

...

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Thermal Stress ◽

Transfer Coefficient ◽

Green’S Function ◽

Green's Function ◽

Fluid Temperature ◽

Transfer Coefficients ◽

Temperature Dependent ◽

Heat Transfer Coefficients

Thermal stress failure caused by alternating operational loads is the one of important damage mechanisms in the nuclear power plants. To evaluate the thermal stress responses, the Green’s function approach has been generally used. In this paper, a method to consider varying heat transfer coefficients when using the Green’s function method is proposed by using artificial parameter method and superposition principle. Time dependent heat transfer coefficient has been treated by using a modified fluid temperature and a constant heat transfer coefficient. Three-dimensional temperature and stress analyses reflecting entire geometry and heat transfer properties are required to obtain accurate results. An efficient and accurate method is confirmed by comparing its result with corresponding 3D finite element analysis results for a reactor pressure vessel (RPV). From the results, it is found that the temperature dependent material properties and varying heat transfer coefficients can significantly affect the peak stresses and the proposed method can reduce computational efforts with satisfactory accuracy.

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