• Steel and Composite Structures
• /
• v.27 no.5
• /
• pp.633-646
• /
• 2018

This study investigated the seismic performance of a hybrid damper composed of a steel slit plate and friction pads, and an optimum retrofit scheme was developed based on life cycle cost. A sample hybrid damper was tested under cyclic loading to confirm its validity as a damping device and to construct its nonlinear analysis model. The effectiveness of the optimum damper distribution schemes was investigated by comparing the seismic fragility and the life cycle costs of the model structure before and after the retrofit. The test results showed that the damper behaved stably throughout the loading history. Numerical analysis results showed that the slit-friction hybrid dampers optimally distributed based on life cycle cost proved to be effective in minimizing the failure probability and the repair cost after earthquakes.

• International Journal of Reliability and Applications
• /
• v.7 no.1
• /
• pp.1-11
• /
• 2006

The better mean residual life at $t_0\;(BMRL-t_0)$ class of life distribution is introduced by Kulasekara and Park (1987). They proved that the $BMRL-t_0$ class contains the DMRL class, but it is a proper subclass of the NBUE class. In this paper we develop a new family of tests for testing exponentiality against the $BMRL-t_0\;(WMRL-t_0)$ alternatives based on the goodness of fit approach. It is shown that the suggested test is better than the one introduced by Kulasekara and Park (1987) in the sense of Pitman asymptotic efficiency values.

• Journal of the Korean Society for Precision Engineering
• /
• v.26 no.9
• /
• pp.96-102
• /
• 2009

In this study, performs analysis of the life of parallel opening type pneumatic chucks that are usually applied in the factory automation line. Pneumatic chucks have complicated failure cause because they are organized as a complex of various elements. Therefore, we analyzed the main failure mode of pneumatic chuck, and then performed life test and performance test according to the international standards. On the basis of these processes, shape parameter of pneumatic chuk is proposed that is the main factor for the calculation of zero failure test time for the reliability of pneumatic chuck and their data analysis of life distribution.

• 한국신재생에너지학회:학술대회논문집
• /
• 2005.11a
• /
• pp.693-697
• /
• 2005

This study was performed to develop accelerated life test method of the wind-turbine gearbox using accumulated damage theory that used to model the fatigue of parts that receive variable load. The accumulated damage theory was introduced, and the estimation of life and calculation of accelerated life test time was illustrated. As the actual application example, accelerated life test method of the gearbox was described. Life distribution of the wind-turbine gearbox was supposed to follow Weibull distribution and life test time was calculated under the conditions of average life (MTBF) 140,600 hours and 99% reliability for one test sample According to the accumulated damage theory, because test time can shorten in case increase test load, test time could be reduced by 1.2 years when we put the load 1.2 times of rated load than 0.93 times of rated load that is equivalent load calculated by load spectrum of the wind turbine. This time, acceleration coefficient was 21.3. This accelerated test method was used to develop accelerated test method of gear reducer, gear and bearing as well as the industrial gearbox and it is considered to be applied comprehensively to mechanical parts the fatigue of which is happened by load or pressure etc.

• International Journal of Reliability and Applications
• /
• v.1 no.1
• /
• pp.89-104
• /
• 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.

• The Journal of Industrial Distribution & Business
• /
• v.11 no.3
• /
• pp.29-38
• /
• 2020

Purpose: Geographical relocation has been conducted to alleviate overcrowding and to support balanced regional development in many countries. Previous studies have seldom examined the effectiveness of relocation on job and life dissatisfaction, particularly in the public sector. The purpose of this study is to investigate the determinants of relocation on job and life dissatisfaction. Proposed research questions include the following: i) do working conditions in the new workplace and interactivity affect job dissatisfaction? ii) do social infrastructure and social activity in the new location affect life dissatisfaction? and iii) is there a relationship between job and life dissatisfaction? Research Design, data, and methodology: The study collected data via an online survey and applied statistical analyses such as factor analysis, regression, and ANOVA. Results: The results of this study found that proposed determinants excluding mobility inefficiency and decision-making affect job and life dissatisfaction. The results also showed that there are relationships between job and life dissatisfaction. Conclusions: The results of this study provide both managerial and policy implications of relocation for the public sector. The results of this study implied that better policy should be designed to increase job and life satisfaction that also accounts for the realities of relocation.

• 연구논문집
• /
• s.32
• /
• pp.35-43
• /
• 2002

This study was performed to develop accelerated life test method of machanical parts using cumulative damage theory that used to model the fatigue of parts that receive variable load. The cumulative damage theory was introduced, and the estimation of life and calculation of accelerated life test time was illustrated. As the actual application example, accelerated life test method of agricultural tractor transmission was described. Life distribution of agricultural tractor transmission was supposed to follow Weibull distribution and life test time was calculated under the conditions of average life (MTBF) 3,000 hours and 90% reliability for one test sample. According to the cumulative damage theory, because test time can shorten in case increase test load, test time could be reduced by 482 hours when we put the load 1.1 times of rated load than 0.73 times of rated load that is equivalent load calculated by load spectrum of the agricultural tractor. This time, acceleration coefficient was 11.7. This accelerated test method was used to develop accelerated test method of gear reducer, hydraulic hose and bearing as well as agricultural tractor transmission and it is considered to be applied comprehensively to machanical parts the fatigue of which is happened by load or pressure etc.

• The Journal of Industrial Distribution & Business
• /
• v.9 no.4
• /
• pp.27-35
• /
• 2018

Purpose - The purpose of this research is to verify mediation effects of finance stress within relation structure between income inequality recognized by the elderly and life satisfaction. Research design, data, and methodology - In order to achieve the purpose of this research, we investigated recognition of income inequality of the elderly, finance stress and life satisfaction by using examination data aimed at 541 elderly people whose age is over 65 living in Chungcheongbuk-do. We conducted reliability, correlation, regression analysis_(tolerance limit and variance inflation factor) by using SPSS ver. 18.0. Results - From the result of analysis, it was proved that there are mediation effects of finance stress within the relation between income inequality recognized by the elderly and satisfaction with life. Based on this result, we suggest practical and political proposals to increase life satisfaction of the elderly. Conclusions - The purpose of this research is to verify mediation effects of finance stress in the relationship between income inequality and life satisfaction recognized by the elderly. From the result of research, first, a direct effect was discovered that as income inequality becomes high, life satisfaction will be decreased. Second, partial mediation effect of finance stress was confirmed in the relationship between income inequality and life satisfaction.

• Journal of Korean Society for Quality Management
• /
• v.11 no.1
• /
• pp.10-17
• /
• 1983

This paper studies item-life test plans with the specified item mean life $T_1$ (MTBF) - Producer's risk ${\alpha}$ and item mean life $T_2$ (MTBF, $T_2$ < $T_1$) - Consumer's risk ${\beta}$ when the probability of item survival follows the Weibull distribution (known shape parameter) as a expansion of [1]. And Operating Characteristic Curves and Average Life-testing Times of item-life test plans are computed for this paper and [1]. Cost analysis procedures are same as [1]. These results are computed by using computer program written in Level II Basic for Apple II Plus Micro-computer. Both this paper and [6] reduce the life-testing time for Weibull distribution in comparision with Exponential distribution, but results of [6] were computed for different criterions from this paper.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2002.05a
• /
• pp.104-109
• /
• 2002

In this paper, a statistical analysis of fatigue crack growth behavior under constant amplitude loads has been carried out. Fatigue crack growth tests were conducted on sixteen pre-cracked compact tension (CT) specimens of the pressure vessel (SPV50) steel in controlled identical load and environmental conditions. The assessment of the statistical distribution of fatigue crack growth experimental data obtained from SPV50 steel was studied and also the correlation of the parameter C and m in the Paris-Erdogan law was discussed. The probability distribution function of fatigue crack growth life seems to follow the 3-parameter Weibull. The fatigue crack growth rate seems to follow the 3-parameter Weibull and the log-normal distribution. The coefficient of variation (COV) of fatigue crack growth life was observed to decrease as the crack grows. A strong negative linear correlation exists between the coefficient C and the exponent m in Paris model. Fatigue crack growth rate data shows a normal distribution for both m and logC.