• 한국신뢰성학회지:신뢰성응용연구
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• 제4권2호
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• pp.73-90
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• 2004

We performed the heat aging test to predict the useful lifetime of Elastomeric Bearing Chloroprene Rubber (CR) used for supporting bridge. During the test, we measured elongation that are influenced by temperature and aging time. The failure of a test piece is defined as the point at which the elongation reaches to 75% of the initial value. This failure criterion is based on KS F 4420: 1998 (Elastomeric Bearing for bridge). Through the accelerated heat aging test, we found that the Arrhenius relationship and the Weibull lifetime distribution are appropriate as the life-temperature relationship and lifetime distribution of the CR, respectively. Using the Arrhenius -Weibull model, the parameters of the model are estimated and the lifetime of the CR at use condition is predicted.

• International Journal of Reliability and Applications
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• 제1권1호
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• pp.89-104
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• 2000

Accelerated testing consists of a variety of test methods for shortening the life of products or hastening the degradation of their performance. This paper presents practical, modern statistical methods for evaluating the reliability of Nickel-Cadmium batteries at their design temperature of 2$0^{\circ}C$ by accelerated life test. Batteries have been life tested at three high temperature conditions, 50, 60, 7$0^{\circ}C$, respectively to yield failures quickly. The failures have been observed and judged by means of charge and discharge current integration. Analyses of life data from those conditions resulted in the Weibull distribution, which has been verified on the ground of the Kolmogorov-smirnov test and the pairwise t-test. Life data are modeled according to the Arrhenius life-temperature relationship. The mean life of tested batteries is assessed at about 590 cycles, and the activation energy of this chemical reaction is concluded to be 0.39eV as results. This study provides procedures for estimating the reliability of batteries in a short period, which has little been possible in domestic industries. The results can be applied in many fields such as proof testing, acceptance testing, and estimating assurance periods.

• 한국전기전자재료학회논문지
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• 제29권1호
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• pp.17-22
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• 2016

The activation energy of a material is an important factor that significantly affects the lifetime and can be used to develop a degradation model. In this study, a thermal analysis was carried out to evaluate and collect quantitative data on the degradation of insulation materials like EPR and CSP used for nuclear power plant cables. The activation energy was determined from the relationship between log ${\beta}$ and 1/T based on the Flynn.Wall.Ozawa method, by a TGA test. The activation energy was also derived from the relationship between ln(t) and 1/T based on isothermal analysis, by an OIT test. The activation energy of EPR derived from thermal analysis was used to calculate the accelerated aging time corresponding to the number of years of use, employing the Arrhenius equation, and determine the elongation corresponding to the accelerated aging time.

• 한국연초학회지
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• 제4권2호
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• pp.57-61
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• 1982

For evaluating kinetic parameters of various reactions and materials a straight- forward method has been studied by the variable heating rate method in DSC analysis. Based on the linear relationship between the logarithm of the heating rate and reciprocal Peak temperature, this method allows calculation of activation energy and the Arrhenius frequency factor by only one observation of the peak temperature versus the heating rate. According to tile D function, D=-In P(x)/dx, to x(=$\frac{E}{RT}$) we can calculate reasonably accurate activation energy, tile Arrhenius factor and the rate constant, and predict half-life times of various materials from the kinetic calculation.

• 한국신뢰성학회지:신뢰성응용연구
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• 제11권2호
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• pp.127-140
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• 2011

This paper presents an accelerated life test of aviation taxiway lights installed in the airport to help safe navigation of airplanes at night or in bad weather. Recently halogen lamps of taxiway lights are replaced by LED ones and their reliability needs yet to be verified. Thus, effective test conditions are designed reflecting the failure modes and mechanisms from the previous studies on LED, which include the accelerated degradation process. The test is performed under the temperature $70^{\circ}C$ and $90^{\circ}C$ for two types of LED lights, taxiway center line lights(TCLL) and taxiway edge lights (TEDL). The failure time data were analyzed using lognormal distribution and Arrhenius model to find the life-stress relationship, acceleration factor and life characteristics under the normal condition temperature $30^{\circ}C$.

• International Journal of Railway
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• 제6권1호
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• pp.13-25
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• 2013

Railpad prevents damage of the tie and ballast by reducing the impact and high frequency vibration, which occurs when a vehicle load transfers to a tie. But elasticity of the railpad can decrease under vehicle load and over usable period. If that happens, railpad will become stiffer. Increase in stiffness of the railpad also translates into a rise in track maintenance cost because it accelerates the damage of the track. In this study, accelerated heat ageing test was performed to predict an expectable lifetime of the railpad. As a result, it was predicted to be about sixteen years at $25^{\circ}C$ that life time of railpad using NR rubber from Arrhenius relationship. Also, it was predicted to be about thirty-two days at $100^{\circ}C$. At this time, a standard rate of thickness change is approximately within 12%.

• 동력기계공학회지
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• 제16권2호
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• pp.43-48
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• 2012

Generally accelerated life test is well known as one method to reduce reliability qualification test period. This test is conducted under the higher stress condition than normal condition. So it can save the test time by calculating the acceleration factor from the relationship between the worst stress condition and normal condition. This paper investigates the worst stress condition for the accelerated life test to increase the acceleration factor. Especially, we focused on the method to obtain effective acceleration factors under the worst stress condition. Moreover, we considered how to decide the worst stress condition by looking for the operating limit of this system. The acceleration factor can be estimated from the ratio of the kinematic viscosity in the normal condition and the worst stress condition, the lowest temperature, by using Arrhenius relationship. Through some experiments for a refrigerator's compressor, we were able to confirm how to increase acceleration factors and how to reduce the reliability qualification test period with minimum samples.

• Computers and Concrete
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• 제20권6호
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• pp.635-643
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• 2017

The rehabilitation and strengthening of concrete structures using Fiber-Reinforced Polymer (FRP) materials have been widely investigated. As a priority issue, however, the effect of curing conditions on the bonding behavior between FRP and concrete structures is still elusive. This study aims at developing a prediction model to accurately capture the mode-II interfacial debonding between FRP strips and concrete under different curing conditions. Single shear debonding experiments were conducted on FRP-concrete samples with respect to different curing time t and temperatures T. The J-integral formulation and constrained least square minimization are carried out to calibrate the parameters, i.e., the maximum slip $\bar{s}$ and stretch factor n. The prediction model is developed based on the cohesive model and Arrhenius relationship. The experimental data are then analyzed using the proposed model to predict the debonding between FRP and concrete, i.e., the interfacial shear stress-slip relationship. A Finite Element (FE) model is developed to validate the theoretical predictions. Satisfactory agreements are obtained. The prediction model can be used to accurately capture the bonding performance of FRP-concrete structures.

• 대한기계학회논문집A
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• 제38권5호
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• pp.505-511
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• 2014

내연기관의 냉각기 고무호스에 사용되는 EPDM 고무는 열과 기계적 하중을 받는 동시에 국부적으로 형성된 전기적 스트레스를 받아 복합적인 노화가 발생한다. 본 연구에서는 EPDM 고무의 전기화학적 복합노화 시험을 하고, 아레니우스 관계식을 이용하여 노화온도($60^{\circ}C$, $80^{\circ}C$, $100^{\circ}C$)에 따른 가속수명 예측식을 구하였다. 수명에 영향을 미치는 인장변형률(5%, 10%)을 반영하여 예측식의 기울기($E_a/R$) 및 아레니우스 상수(C)를 고려한 수정된 수명예측 식을 제안하였다. 이를 통해 노화온도와 인장변형률에 영향을 받은 EPDM 고무의 수명을 예측하였고, 수정된 수명예측 시간이 실제 실험결과의 편차 범위 이내에서 일치함을 확인하였다.

• 한국물환경학회지
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• 제31권2호
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• pp.142-150
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• 2015

The relationship between the number of benthic macroinvertebrate species and the accumulated survey area were investigated in a clean stream and an impaired stream of Korea. Five models to characterize species-area functions were compared, and the Weibull model fitted species-area data well. The other models (Arrhenius, Romell-Gleason, Kylin, Lognormal model) had small or notable bias. The maximum number of species and half-saturation area derived from the Weibull model may be used as the indicators of the carrying capacity and the habitat complexity respectively.