• Journal of the Korean Society for Precision Engineering
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• v.21 no.2
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• pp.122-129
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• 2004

There is an increasing need for large flat panel display devices. PDP (Plasma Display Panel) is one of the most promising candidates for this need. Thermal shock failure of PDP glass during manufacturing process is a critical issue in PDP industry since it is closely related to the product yield and the production speed. In this study, thermal shock resistance of PDP glass is measured by water quenching test and an analysis scheme is described for estimating transient temperature and stress distributions during thermal shock. Based on the experimental data and the analysis results, a simple procedure for predicting the thermal shock failure of PDP glass is proposed. The fast cooling process for heated glass plates can accelerate the speed of PDP production, but often leads to thermal shock failure of the glass plates. Therefore, a design guideline for preventing the failure is presented from a viewpoint of high speed PDP manufacturing process. This design guideline can be used for PDP process design and thermal -shock failure prevention.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.164-167
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• 2003

Thermal shock is a physical phenomenon that occurs upon a rapid, large temperature and pressure change or in the quenching condition of materials. In this study, thermal shock fracture resistance and thermal shock fracture toughness were evaluated by using laser irradiation. The temperature distribution of a specimen was detected using type K and C thermocouples. The irradiated surfaces were observed by SEM. It is concluded that the critical laser power necessary to fracture can be the major factor of thermal shock resistance and thermal shock fracture toughness of materials.

• Nuclear Engineering and Technology
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• v.53 no.9
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• pp.3112-3121
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• 2021

One of the major factors affecting the life span of a Reactor Pressure Vessel (RPV) is the Pressurised Thermal Shock (PTS). PTS is a thermo-mechanical load on the RPV wall due to steep temperature gradients and structural load created by internal pressure of the fluid within the RPV. Safe operating life of a nuclear power plant is ensured by carrying out fracture analysis of the RPV against thermal shock. Carrying out fracture tests on RPV/large scale components is not always feasible. Hence, studies on laboratory level specimens are necessary to validate and supplement the prototype results. This paper aims to study the fracture behaviour of standard Compact Tension [C(T)] specimens, made of RPV steel 20MnMoNi55, subjected to thermal shock through experimental and numerical investigations. Fracture tests have been carried out on the C(T) specimens subjected to thermal transient load and tensile load to quantify the effect of thermal shock. Crack resistance curves are obtained from the fracture tests as per ASTM E1820 and compared with those obtained numerically using XFEM and a good agreement was found. A quantitative study on the crack tip plastic zone, computed using cohesive segment approach, from the numerical analyses justified the experimental crack initiation toughness.

• The Korean Journal of Ceramics
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• v.4 no.4
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• pp.345-351
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• 1998

Thermal shock resistance of $Al_2O_3$- and Fe-$Al_2TiO_5$-based Castable Refractories was studied using a central heating technique. Ring type specimens, 10mm thick and 20 and 100mm inner and outer diameters, respectively, were rapidly heated on the internal surface of the centre hole using a high power electrical heating element. The temperature field was measured experimentally and modelled using finite element analysis (FEA). The thermal stress field was also modelled using FEA. A radial notch was introduced to the ring specimens to enable calculation of the thermal stress intensity factors (SIF). A special LVDT device was incorporated in the thermal shock tester to monitor crack mouth opening displacement (COD). The thermal shock fracture initiation and crack propagation behaviour of the castable refractories were ascertained using the COD measurements and the fracture mechanics analysis data.

• Journal of the Korean Ceramic Society
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• v.54 no.4
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• pp.314-322
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• 2017

This study investigates changes in the mechanical behavior, such as changes in indentation load-displacement curve, wear resistance and contact fatigue resistance of thermal barrier coatings (TBCs) by thermal cycling test and thermal shock test. Relatively dense and porous TBCs on nickel-based bondcoat/superalloy are prepared; the highest temperature applied during thermal durability test is $1350^{\circ}C$. The results indicate that the porous TBCs have relatively longer lifetime during thermal cycling and thermal shock tests, while denser TBCs have relatively higher wear and contact fatigue resistance. The mechanical behavior is influenced by sintering of the TBCs by exposure to high temperature during tests.

• Journal of Sensor Science and Technology
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• v.18 no.6
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• pp.441-448
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• 2009

Magnesia partially stabilized zirconia(Mg-PSZ) solid electrolytes for an improvement of thermal shock resistance, which is suitable for the measurement of oxygen activity in a molten steel, were prepared by post-thermal aging treatment. The steelmaking oxygen sensor elements were formed by an injection molding method, sintered at $1650^{\circ}C$, and then thermal aged ranged from 1250 to $1400^{\circ}C$. Sintered density and porosity were decreased as increasing the magnesia content in a zirconia-magnesia solid solution. Fractions of cubic phase to the synthesized Mg-PSZ solid electrolytes were ranged from 13.13 to 79.54.% after post-thermal aging treatment. Very dense microstructure without voids in the grains was obtained by the post-thermal aging process. Fine tetragonal phase crystallites precipitated on the cubic surface during post-thermal aging up to $1300^{\circ}C$ improve a thermal shock resistance and reappearance of electro motive force(EMF) curve.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 2000.06a
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• pp.179-193
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• 2000

Aluminium titanate (Al₂TiO5) with an excellent thermal shock resistant and a low the expansion coefficient was obtained by solid solution with MgO, SiO₂, and ZrO₂ in the Al₂TiO5 lattice or in the grain boundary solution through electrofusion in an arc furnace. However, these materials have low mechanical strength due to the presence of microcracks developed by a large difference in thermal expansion coefficients along crystallographic axes. Pure Al₂TiO5 tends to decompose into α-Al₂O₃ and TiO₂-rutile in the temperature range of 750-1300℃ that rendered it apparently useless for industrial applications. Several thermal shock tests were performed: Long therm thermal annealing test at 1100℃ for 100h; and water quenching from 950 to room temperature (RT). Cyclic thermal expansion coefficients up to 1500℃ before and after decomposition tests was also measured using a dilatometer, changes in the microstructure, thermal expansion coefficients, Young's modulus and strengths were determined. The role of microcracks in relation to thermal shock resistance and thermal expansion coefficient is discussed.

• Journal of the Korean Ceramic Society
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• v.50 no.2
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• pp.127-133
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• 2013

Porcelain with high thermal shock resistance was successfully fabricated by a lithium solution infiltration method with a lithium hydroxide solution. Lithium hydroxide solutions having various lithium concentrations were infiltrated into pre-sintered porcelain bodies. The porcelain sample infiltrated by the 9 wt% lithium solution and heat treated at $1250^{\circ}C$ for 1 h showed a low thermal expansion coefficient of $1.0{\times}10^{-6}/^{\circ}C$ with excellent thermal shock resistance. The highly thermally resistant porcelain had a well-developed ${\beta}$-spodumene phase with the general phases observed in porcelain. Furthermore, the porcelain showed a denser structure of $2.41g/cm^3$ sintering density and excellent whiteness in comparison with commercial thermally resistible porcelains. The lithium hydroxide in the samples readily reacted with moisture, and liquid phase reactants were formed during the fabrication process. In the case of an excess amount of lithium in the sample body, the lithium reactants were forced to the surface and re-crystallized at the surface, leaving large pores beneath the surface. These phenomena resulted in an irregular structure in the surface area and led to cracking in samples subjected to a thermal shock test.

• Journal of Applied Reliability
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• v.13 no.3
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• pp.207-216
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• 2013

This paper, we classified LED failure mechanisms that occur due to the delamination and analyzed each of the mechanism that gives the LED PKGs the effect. Usually, the LED is composed of several materials which are LED chips, gold wire, phosphor, epoxy resin, adhesive, reflector and lead frame. These different materials are usually delaminated in trouble conditions which are huge temperature difference, hot and humid or mechanical shocked. When the components are delaminated, a luminance will be lost and moisture be absorbed easily, a thermal resistance be increased attendantly. In this paper, we experimented to investigate failure mechanism of the thermal resistance and failure mechanism of the decrease of luminance that occur due to the delamination. A thermal shock test was performed to reproduce this phenomena by subjecting samples to a cold-hot cyclling process between $-30^{\circ}C$(15min) and $110^{\circ}C$(15min). The samples were inspected at 200, 600 and 1,000 cycles. We measured feature of LED using the spatial analyzer, optical microscope, thermal resistance, photometer, scanning electron microscope (SEM). As a result, the progression of the crack and the thermal resistance and decrease in luminance are proportional to number of thermal shock.

• Journal of the Korean Ceramic Society
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• v.37 no.3
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• pp.201-204
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• 2000

Thermal shock resistance of 80Al2O3-20Al composite and monolithic alumina ceramics was compared. Fracture strength was measured by using a 4-pont bending test after quenching. Thermal stresses of the ceramics and ceramic-metal composites were calculated using a finite element analysis. The bending strength of the Al2O3 ceramics decreased catastropically after quenching from 20$0^{\circ}C$ to $0^{\circ}C$. The bending strength of the composite also decreased after quenching from 200~2$25^{\circ}C$, but the strength reduction was much smaller than for Al2O3. The maximum thermal stress occured in the monolithic alumina ceramics when exposed to a temperature difference of 20$0^{\circ}C$ was 0.758 GPa. The same amount of stress occured in the Al2O3-Al composite when the temperature difference of 205$^{\circ}C$ used.