• Korean Journal of Metals and Materials
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• v.46 no.5
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• pp.276-282
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• 2008

Material degradation of Cr steels in boiler tubes was accompanied by the microstructural changes including carbide behavior and crack formation. The microstructural change and the mechanical behavior of hardness and creep properties in accelerated heat-treatments were studied in order to identify the material degradation of the X20 Cr steel. The degradation behavior was occurred in the hardness increasing followed by decreasing due to carbide dissolution and precipitation.

• Proceedings of the KIEE Conference
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• 1987.11a
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• pp.207-209
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• 1987

This paper reports the effect of additive elements such as Bi, Sb on degradation and hole formation of the Te-Se thin films. Changes in light transmission were used to monitor the degradation rate of thin Te films in an accelerated temperature-humidity environment. In thin accelerated temperature-humidity environment, $(Te_{86}Se_{14})_{70}Bi_{30}$ thin film was stable and $(Te_{86}Se_{14})_{50}Sb_{50}$ thin film was unstable in comparison with the other films that used in this experiment. The hole formation was carried out in the Te-based thin films.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.199-202
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• 1998

In examining application of polymer as electrical insulators, it is very important to perform accelerated aging test substituted the process which polymer insulator is degraded for long-time by the process of short-time. The purpose of this paper is to examine the properties of water degradation which affect on the efficiency of epoxy insulator. To do this, the surface properties on epoxy insulating material have been investigated after long-time accelerated degradation in boiling water condition. The experimental results showed the contact angle and surface resistivity after treatment to decrease the sample of water treatment. In dielectric properties, dielectric constant was increased by the aging development with water treatments.

• Journal of Korean Society for Quality Management
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• v.26 no.1
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• pp.74-87
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• 1998

This study considers optimal design of accelerated life tests under constant stress using that the first passage time to cross a critical boundary through amount of accumulated degradation has an inverse Gaussian distribution when the degradation process follows to a Brownian motion with positive drift of log linear function of stress. Optimum plans for Type I censoring are derived by minimizing the asymptotic variance of estimated quantiles at the use stress. Sensitivity analyses are also conducted to see how sensitive the optimality criterion is with respect to the uncertainties involved in the guessed values.

• Journal of Applied Reliability
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• v.12 no.2
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• pp.67-78
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• 2012

An electric double-layer capacitor(EDLC) is an electrochemical capacitor with relatively high energy density, typically hundreds of times greater than conventional electrolytic capacitors. EDLCs are widely used for energy storage rather than as general-purpose circuit components. They have a variety of commercial applications, notably in energy smoothing and momentary-load devices, and energy-storage and kinetic energy recovery system devices used in vehicles, etc. This paper presents an accelerated degradation test of an EDLC with rated voltage 2.7V, capacitance 100F, and usage temperature $-40^{\circ}C{\sim}65^{\circ}C$. The EDLCs are tested at $50^{\circ}C$, $60^{\circ}C$, and $70^{\circ}C$, respectively for 1,750hours, and their capacitances are measured at predetermined times by constant current discharge method. The failure times are predicted from their capacitance deterioration patterns, where the failure is defined as 30% capacitance decrease from the initial one. It is assumed that the lifetime distribution of EDLC follows Weibull and Arrhenius life-stress relationship holds. The life-stress relationship, acceleration factor, and $B_{10}$ life at design condition are estimated by analyzing the accelerated life test data.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.05a
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• pp.456-458
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• 2022

Due to the environmental regulations of the International Maritime Organization, shipyards are conducting various researches to improve the efficiency of ships, and efforts are being made to reduce the weight of ships. Recently, composite materials including CNT materials have the advantage of being able to reduce weight by 40% or more compared to general steel plate materials, and have the advantage of being able to be used as a substitute for ship clamps or door skins. Therefore, in this study, to predict the life of composite materials including CNT materials, the results were compared through the accelerated deterioration test method and the life prediction using machine learning techniques. The accelerated degradation test used the Arrhenius model equation, and the machine learning method predicted the life using a regression analysis algorithm.

• Nuclear Engineering and Technology
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• v.30 no.2
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• pp.148-163
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• 1998

Flow Induced Material Degradation (FIMD) is reviewed focusing on Flow Accelerated Corrosion (FAC) models. Several examples of FAC related incidents are described, which include nuclear and fossile power plants. Lastly, mitigation techniques such as inspection, material selection, water chemistry, temperature, and hydrodynamic factor are discussed.

• Fire Science and Engineering
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• v.32 no.2
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• pp.48-56
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• 2018

This paper reports the results of a study on the over-current characteristics of IV insulated wire sheath according to accelerated degradation. In order to examine the degradation of a IV insulated wire sheath through insulation, acceleration degradation experiments were performed using the Arrhenius equation of acceleration life test models; test samples with equivalent lives of 0, 10, 20, 30 and 40 years were prepared. Then allowed currents with over-current of 100%~500% were introduced to measure the times of first generation of smokes and carbonization in the wire sheath, and it was found that the times of first generation of smokes and carbonization in the wire sheath decreased as the equivalent life increased. In more detail, when 270% over-current is applied, the electrical fire risk of equivalent life of 40 years increased by approximately 3.2 times based on equivalent life of 0 years. Also, when the over-current was 255% and 260%, carbonization occurred only in the equivalent life of 40 years, and the fire risk according to the accelerated degradation was increased dramatically. In addition, FT-IR and SEM analyzes were used to confirm the characteristics and surface changes of IV insulated wire sheath according to the equivalent life.

• Tribology and Lubricants
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• v.27 no.3
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• pp.134-139
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• 2011

The mechanical equipments which are exposed to impure environment undergo significant reductions in their own lifetimes. Several environmental test procedures have been developed to analyze these phenomena. Moreover in the industry to require shorter development duration, accelerated life testers artificially add test containments into machines. In this research JIS Z 8901 test powder was added into internal gear pumps which are used as oil pumps in vehicles and thus the effects of the addition on the degradation of the pumps were examined. Three kinds of contaminants were selected. Two of the contaminants are identical in particle size but different in the composition of the ingredients. The other pair have identical ingredients and composition but different particle size. The quantity of contaminants was also an interesting factor in this study. The results show that each JIS contaminant caused notable degradation in the discharge flow characteristic of pumps while friction torque degradation did not have any tendency. Finally leakage rates were deduced and equivalent wear volume ratios were calculated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.3 s.258
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• pp.295-303
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• 2007

Degradation behaviors of filament-winded composites have been evaluated under the accelerated environmental test of high temperature, water immersion and thermal impact conditions. Two kinds of laminated composites coated by an urethane resin have been used: carbon-fiber reinforced epoxy(T700/Epon-826, CFRP) and glass-fiber reinforced phenolic (E-glass/phenolic, GFRP). For tensile strength of $0^{\circ}$ composites, CFRP showed little degradation while GFRP did high reduction by 25% under the influence of high temperature and water However for water-immersed $90^{\circ}$ composites tensile strength of both CFRP and GFRP showed high reduction. Bending strength and modulus of $90^{\circ}$ composites were largely reduced in water-immersion as well as high temperature environment. Urethane coating on the composite surface improved the bending properties by 20%, however hardly showed such improvement for water-immersed $90^{\circ}$ composites. In case of shear strength and modulus, both CFRP and GFRP showed high reduction by water-Immersion test but did a slight increase by high temperature and thermal impact conditions.