• Journal of Conservation Science
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• v.31 no.4
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• pp.373-386
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• 2015

This study identified degradation properties by temperature stress with Araldite$^{(R)}$ AY103-1/HY956 used for ceramics. Tensile and compressive strength of durability increased for 6,480 hours at temperature of $34{\sim}45^{\circ}C$. In stability of external stress and temperature, compressive strength is superior to tensile strength, it requires conservation plans considering strength properties and stress of restoration materials. The tensile shear strength of adhesion properties decreased for 4,320 hours at temperature of $40{\sim}60^{\circ}C$. In ceramics with porosity, environments under isothermal-isohumidity are important because interfacial properties of adherend are concerned with performance variation. Glossiness decreased for 6,480 hours at temperature of $34{\sim}45^{\circ}C$ and color difference increased. Gloss stability was superior and color stability was weak, which requires improvement of optical properties. In artifacts on display in museums, there is concern about temperature rise on restoration materials by lighting therefore, it needs to minimize change in physical properties by exposure environments.

• International Journal of Highway Engineering
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• v.20 no.3
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• pp.1-9
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• 2018

PURPOSES : In order to evaluate a crack resistance at cold joint, sealing tape was adopted to apply at cold joint instead of typical tack coat material(RSC-4). The sealing tape was made by hot sealing material. The crack resistance as function of environmental and traffic loading was measured with visual observation. METHODS : In this study, the crack resistance was evaluated as function of environmental and traffic loading. The freeze-thaw method was adopted for environmental loading of asphalt pavement. condition. The damage of cold joint under freeze-thaw action is initiated by ice expansion load and accelerated by the interfacial damage between new and old asphalt pavement. The traffic loading was applied with wheel tracking machine on the cold joint area of the asphalt pavement for 3 hours at $25^{\circ}C$. The evaluation of crack resistance was measured with visual observation. The freeze-thaw results shows that the sealing tape was significantly increased the crack resistance based on. RESULTS : To estimate the crack resistance at cold joint area due to the environmental loading, the Freeze-thaw test was conducted by exposing the product to freezing temperature(approximately $-18^{\circ}C$) for 24 hours, and then allowing it to thaw at $60^{\circ}C$ for 24 hours. The tack coat material(RSC-4) was debonded after 21 cycles of the Freeze-thaw test. The first crack was observed after 14 freeze-thaw cycle with RSC-4 material. But, the sealing tape was not debonded after 24 cycle test. Also, the sealing tape shows the better performance of the crack resistance under the traffic loading with wheel track test. The crack was generated the under traffic loading with RSC-4(tack coating), however, the crack was not shown with sealing tape. It indicates that the sealing tape has a strong resistance of tensile stress due to traffic loading. CONCLUSIONS :Based on limited laboratory test result, a performance of crack resistance using the sealing tape is better than that of general tack coat material(RSC-4). It means that the sealing tape is possible to extend a pavement service life because the crack, one of the main pavement distresses, will be delayed.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2004.09a
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• pp.233-241
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• 2004

A new alloy definition will be presented concerning increasing demands for the board level reliability of miniaturized interconnections. The damage mechanism for LFBGA components on different board finishes is not quite understood. Further demands from mobile phones are the drop test, characterizing interface performance of different package constructions in relation to decreased pad constructions and therefore interfaces. The paper discusses the characterization of interfaces based on SnPb, SnPbXYZ, SnAgCu and SnAgCuInNd ball materials and SnAgCuInNd as solder paste, the stability after accelerated tests and the description of modified interfaces strictly related to the assembly conditions, dissolution behavior of finishes on board side and the influence of intermetallic formation. The type of intermetallic as well as the quantity of intermetallics are observed, primaliry the hardness, E modules describing the ability of strain/stress compensation. First results of board level reliability are presented after TCT-40/+150. Improvement steps from the ball formulation will be discussed in conjunction to the implementation of lead free materials In order to optimize ball materials for area array devices accelareted aging conditions like TCTs were used to analyze the board level reliability of different ball materials for BGA, LFBGA, CSP, Flip Chip. The paper outlines lead-free ball analysis in comparison to conventional solder balls for BGA and chip size packages. The important points of interest are the description of processability related to existing ball attach procedures, requirements of interconnection properties and the knowledge gained the board level reliability. Both are the primary acceptance criteria for implementation. Knowledge about melting characteristic, surface tension depend on temperature and organic vehicles, wetting behavior, electrical conductivity, thermal conductivity, specific heat, mechanical strength, creep and relaxation properties, interactions to preferred finishes (minor impurities), intermetallic growth, content of IMC, brittleness depend on solved elements/IMC, fatigue resistance, damage mechanism, affinity against oxygen, reduction potential, decontamination efforts, endo-/exothermic reactions, diffusion properties related to finishes or bare materials, isothermal fatigue, thermo-cyclic fatigue, corrosion properties, lifetime prediction based on board level results, compatibility with rework/repair solders, rework temperatures of modified solders (Impurities, change in the melting point or range), compatibility to components and laminates.

• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2004.09a
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• pp.211-219
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• 2004

A new alloy definition will be presented concerning increasing demands for the board level reliability of miniaturized interconnections. The damage mechanism for LFBGA components on different board finishes is not quite understood. Further demands from mobile phones are the drop test, characterizing interface performance of different package constructions in relation to decreased pad constructions and therefore interfaces. The paper discusses the characterization of interfaces based on SnPb, SnPbXYZ, SnAgCu and SnAgCuInNd ball materials and SnAgCuInNd as solder paste, the stability after accelerated tests and the description of modified interfaces stric시y related to the assembly conditions, dissolution behavior of finishes on board side and the influence of intermetallic formation. The type of intermetallic as well as the quantity of intermetallics are observed, primaliry the hardness, E modules describing the ability of strain/stress compensation. First results of board level reliability are presented after TCT-40/+150. Improvement steps from the ball formulation will be discussed in conjunction to the implementation of lead free materials. In order to optimize ball materials for area array devices accelareted aging conditions like TCTs were used to analyze the board level reliability of different ball materials for BGA, LFBGA, CSP, Flip Chip. The paper outlines lead-free ball analysis in comparison to conventional solder balls for BGA and chip size packages. The important points of interest are the description of processability related to existing ball attach procedures, requirements of interconnection properties and the knowledge gained the board level reliability. Both are the primary acceptance criteria for implementation. Knowledge about melting characteristic, surface tension depend on temperature and organic vehicles, wetting behavior, electrical conductivity, thermal conductivity, specific heat, mechanical strength, creep and relaxation properties, interactions to preferred finishes (minor impurities), intermetallic growth, content of IMC, brittleness depend on solved elements/IMC, fatigue resistance, damage mechanism, affinity against oxygen, reduction potential, decontamination efforts, endo-/exothermic reactions, diffusion properties related to finishes or bare materials, isothermal fatigue, thermo-cyclic fatigue, corrosion properties, lifetime prediction based on board level results, compatibility with rework/repair solders, rework temperatures of modified solders (Impurities, change in the melting point or range), compatibility to components and laminates.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.8
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• pp.1398-1408
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• 2003

Tensile and LCF(low cycle fatigue) tests were carried out in air at wide temperature range 20$^{\circ}C$-750$^{\circ}C$ and strain rates of 1${\times}$10$\^$-4//s-1${\times}$10$\^$-2/ to ascertain the influence of strain rate on tensile and LCF properties of prior cold worked 316L stainless steel, especially focused on the DSA(dynamic strain aging) regime. Dynamic strain aging induced the change of tensile properties such as strength and ductility in the temperature region 250$^{\circ}C$-600$^{\circ}C$ and this temperature region well coincided with the negative strain rate sensitivity regime. Cyclic stress response at all test conditions was characterized by the initial hardening during a few cycles, followed by gradual softening until final failure. Temperature and strain rate dependence on cyclic softening behavior appears to result from the change of the cyclic plastic deformation mechanism and DSA effect. The DSA regimes between tensile and LCF loading conditions in terms of the negative strain rate sensitivity were well consistent with each other. The drastic reduction in fatigue resistance at elevated temperature was observed, and it was attributed to the effects of oxidation, creep and dynamic strain aging or interactions among them. Especially, in the DSA regime, dynamic strain aging accelerated the reduction of fatigue resistance by enhancing crack initiation and propagation.

• Geomechanics and Engineering
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• v.8 no.2
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• pp.187-220
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• 2015

Soil disturbance induced by installation of mandrel driven vertical drains decreases the in situ horizontal hydraulic conductivity of the soil in the vicinity of the drains, decelerating the consolidation rate. According to available literature, several different profiles for the hydraulic conductivity variation with the radial distance from the vertical drain, influencing the excess pore water pressure dissipation rate, have been identified. In addition, it is well known that the visco-plastic properties of the soil also influence the excess pore water pressure dissipation rate and consequently the settlement rate. In this study, a numerical solution adopting an elastic visco-plastic model with nonlinear creep function incorporated in the consolidation equations has been developed to investigate the effects of disturbed zone properties on the time dependent behaviour of soft soil deposits improved with vertical drains and preloading. The employed elastic visco-plastic model is based on the framework of the modified Cam-Clay model capturing soil creep during excess pore water pressure dissipation. Besides, nonlinear variations of creep coefficient with stress and time and permeability variations during the consolidation process are considered. The predicted results have been compared with V$\ddot{a}$sby test fill measurements. According to the results, different variations of the hydraulic conductivity profile in the disturbed zone result in varying excess pore water pressure dissipation rate and consequently varying the effective vertical stresses in the soil profile. Thus, the creep coefficient and the creep strain limit are notably influenced resulting in significant changes in the predicted settlement rate.

• Journal of Pharmaceutical Investigation
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• v.32 no.1
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• pp.13-19
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• 2002

Water-lipid soluble multivitamin formulations were widely used to reduce the disease and stress of animals as husbandry has made a remarkable progress in recent. But the efficiency of these formulations is far from satisfactory. So, this study was attempted to develop the physically and chemically stable and useful multivitamin o/w emulsion. Multivitamin o/w emulsion composed of water, soybean oil (10%, v/v), vitamin A, D, E, K, $B_2,\;B_6,\;B_{12}$ and panthenol. To make a stable o/w emulsion, the egg lecithin (2%, w/v) and glycerin (2.5%, w/v) were used for emulsifier and thickening agent, respectively. The oil in water emulsion system was manufactured by microfluidizer and the physicochemical stability of this emulsion was evaluated. The average particle size and interfacial tension were measured. From the result of interfacial tension tested, critical micelle concentration of the egg lecithin was 0.5% (w/v) and optimal concentration for the preparation of emulsion was 2% (w/v). The mean particle size was about $0.6\;{\mu}m$ which was suitable for injections. Short-term accelerated stability as physical stability study was tested by centrifuging and freeze-thawing the emulsion samples. The additions of vitamins resulted in the increment of particle size and reduction of physical stability of emulsion. But it is not an enormous problem for the stability of emulsion. Also, we have performed the long-period preservation stability test for the vitamins. All vitamins were analysed by HPLC. The result of storage under $4^{\circ}C$ and dark conditions demonstrated that all vitamins were maintained stable at least 16 weeks, except for vitamin $B_{12}$.

• Journal of the Korean Institute of Gas
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• v.28 no.1
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• pp.65-72
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• 2024

Green Hydrogen demonstration complex is under conduction in Jeju island which is rich in renewable energy resources and will produces green hydrogen using a water electrolysis systems. In order to check durability of long-term operation, AST(accelerated stress test) was applied and the power pattern based on Jeju Island's wind power was applied. After 800 hours of repeated application of low current and high current, the performance of the PEM water electrolysis cell was reduced by up to 10% and by about 5.5% in operating conditions. As the result of impedance analysis, it can be seen that the electrode polarization resistance greatly increased than ohmic polarization resistance. In addition, when the durability evaluation was conducted by applying the wind power pattern of Jeju Island, the performance of the PEM water electrolysis cell showed up to 1.6% and a decrease of less than 1% in operating conditions. As a result of the impedance, it can be seen that the change of ohmic resistance and electrode polarization resistance is small.

• Economic and Environmental Geology
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• v.52 no.6
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• pp.587-593
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• 2019

This study were subjected to accelerated weathering test under freeze-thaw and pressure conditions to observe initiation and propagation of cracks using CLSM. Applied stress was set at 50 MPa, 55 MPa, 70 MPa for 3 samples each by using compressor and freeze-thaw experiment was conducted while samples maintained that condition. In freeze-thaw experiments, a temperature range was set to -20~40℃ which was 1 cycle for 6 hours. The freeze-thaw cycle was composed of time which reached to set temperature for 1 hour and holding time for 2 hours. On the basis of this cycle, surface of samples was observed by CLSM after each 20 freeze-thaw cycle. From this research, according to increase freeze-thaw cycle, there were 7, 10, 19 each cracks and High pressured sample's accumulate length was longer than low pressured sample's. High pressured sample's crack velocities were also faster than low pressured sample's which were calculated by accumulate length and freeze-thaw cycle.

• Korean Journal of Materials Research
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• v.10 no.2
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• pp.111-116
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• 2000

Fracture mode and carbide reactions of cast alloy 738LC during thermal exposure and creep at 816$^{\circ}C$/440MPa and 982$^{\circ}C$/152MPa were investigated. Crystallographic transgranular failure was observed in the specimen crept at 816$^{\circ}C$ due to shearing on the slip plane. Because selective oxidation at the grainboundaries which was exposed at the surface leads reduction in surface energy, however, early initiation of crack at the grainboundaries and intergranular failure were observed in the specimen crept at 982$^{\circ}C$/152MPa. As a result of decomposition of MC carbide at the tested temperatures, M(sub)23C(sub)6 carbide precipitated either on the grainboundaries or on the deformation band. The applied stress enhanced decomposition of MC. $\sigma$phase nucleated from Cr(sub)23C(sub)6 then grew to the ${\gamma}$+${\gamma}$\\` matrix. Precipitation of $\sigma$was accelerated by increasing temperature and applied stress.