• International journal of steel structures
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• v.18 no.4
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• pp.1384-1396
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• 2018

One of the failure modes observed in steel yield energy dissipating devices (SYEDs) excited by a strong earthquake would be the low-cycle fatigue failure. Fatigue cracks of a SYED are prone to initiate at the notch areas where stress concentration is usually occurred, which is demonstrated by the cyclic tests and analyses carried out for this study. Since the fatigue failure of SYEDs dramatically deteriorates their structural capacities, the thorough investigation on their fatigue life is usually required. To do this, sophisticated modeling with considering a time-consuming and complicate fracture mechanism is generally needed. This study makes an effort to investigate the low-cycle fatigue life of SYEDs predicted by a simplified method utilizing damage indices and fatigue prediction equations that are based on the plastic strain amplitudes obtained from typical finite element analyses. This study shows that the low-cycle fatigue failure of SYEDs predicted by the simplified method can be conservatively in good agreement with the test results of SYED specimens prepared for experimental validation.

• Journal of Information Technology Applications and Management
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• v.28 no.4
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• pp.13-20
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• 2021

In this paper, I was applied the life distribution following linear failure rate distribution, Lindley distribution and Burr-Hatke exponential distribution extensively used in the arena of software reliability and were associated the reliability possessions of the software using the nonhomogeneous Poisson process with finite failure. Furthermore, the average value functions of the life distribution are non-increasing form. Case of the linear failure rate distribution (exponential distribution) than other models, the smaller the estimated value estimation error in comparison with the true value. In terms of accuracy, since Burr-Hatke exponential distribution and exponential distribution model in the linear failure rate distribution have small mean square error values, Burr-Hatke exponential distribution and exponential distribution models were stared as the well-organized model. Also, the linear failure rate distribution (exponential distribution) and Burr-Hatke exponential distribution model, which can be viewed as an effectual model in terms of goodness-of-fit because the larger assessed value of the coefficient of determination than other models. Through this study, software workers can use the design of mean square error, mean value function as a elementary recommendation for discovering software failures.

• Journal of the Korea Safety Management & Science
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• v.3 no.2
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• pp.123-131
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• 2001

Reliability calculation of a system is frequently required in industrial, military, and everyday life situations. For such a calculation, it is necessary to specify the configuration of components and subsystems, the failure mode of each component, and the states in which the system is classified as failed. In this paper, we are primary interested in the time to the first failure of a system. And we discuss failure probability of coherent system under various condition, especially focus on probability calculation of subsystem failure before system failure used by Bayes formula. Problem statement and general applications illustrated by several examples.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.9
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• pp.1169-1174
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• 2013

Most products are indeed governed by multiple failure modes. However, there are few cases in which reliability analysis applies to only one failure mode at a time. Furthermore, reliability data do not include information about failure modes, or the reliability analysis is performed using a representative failure mode. The Weibull shape parameter for failure modes is more important than one for products in the reliability qualification test. This paper presents reliability analysis methods for a mechanical component with multiple failure modes. These methods include the competing failure modes (CFM) method and the mixed Weibull method. Pneumatic cylinder test data with three failure modes are presented to estimate the shape parameter for each separate failure mode. In addition, reliability measures (B10 life, characteristic life) of the pneumatic cylinder considering three failure modes were compared with those assuming a single failure mode.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.372-378
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• 2018

Life management technology is required as the failure risk of aged power transformers increases. Asset management technology is developed to evaluate the remaining life, establish the replacement strategies, and decide the optimal investment based on the reliability and economy of power transformers. The remaining life assessment uses data such as installation, operation, maintenance, refurbishment, and failure of power transformers. The optimal investment also uses data such as maintenance, outage, and social costs. To develop the asset management system for power transformers, determining the degradation parameters related to the aging of power transformers and evaluating the condition of power transformers using these parameters are important. In this study, since 1983, 110,000 Dissolved Gas Analysis (DGA) data have been analyzed to determine the degradation parameters related to the aging of power transformers. The alarm rates of combustible gases ($H_2$, $C_2H_2$, $C_2H_4$, $CH_4$, and $C_2H_6$), TCG, CO, and $CO_2$ were analyzed. The end of life and failure rate (bathtub curve) of power transformers were also calculated based on the failure data from 1981 to 2014. The DGA gases related to discharge, overheating, and insulation degradation were determined based on alarm and failure rates. $C_2H_2$, $C_2H_6$, and $CO_2$ were discharge, oxidation, and insulation degradation parameters related to the aging of power transformers.

• Polymer(Korea)
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• v.32 no.5
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• pp.440-445
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• 2008

The failure mechanism and failure morphology of linear low density polyethylene (LLDPE) tubing under hydrostatic pressure were investigated. Microscopic observations using video microscope and scanning electron microscope indicate that the failure mode is a brittle fracture including cracks propagated from inner wall to outer wall. In addition, oxidation induction time and Fourier transform infrared spectroscopy results show the presence of exothermic peak and the increase in carbonyl index on the surface of fractured LLDPE tubing, due to thermal-degradation. An accelerated life test methodology and testing system for LLDPE tubing are developed using the relationship between stresses and life characteristics by means of thermal acceleration. Statistical approaches using the Arrhenius model and Weibull distribution are implemented to estimate the long-term life time of LLDPE tubing under hydrostatic pressure. Consequently, the long-term life time of LLDPE tubing at the operating temperature of $25^{\circ}C$ could be predicted and also be analyzed.

• Journal of Mechanical Science and Technology
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• v.20 no.4
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• pp.473-481
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• 2006

Predicting fatigue life by numerical methods was almost impossible in the field of rubber materials. One of the reasons is that there is not obvious fracture criteria caused by nonstandardization of material and excessively various way of mixing process. But, tearing energy as fracture factor can be applied to a rubber-like material regardless of different types of fillers, relative to other fracture factors and the crack growth process of rubber could be considered as the whole fatigue failure process by the existence of potential defects in industrial rubber components. This characteristic of fatigue failure could make it possible to predict the fatigue life of rubber components in theoretical way. FESEM photographs of the surface of industrial rubber components were analyzed for verifying the existence and distribution of potential defects. For the prediction of fatigue life, theoretical way of evaluating tearing energy for the general shape of test-piece was proposed. Also, algebraic expression for the prediction of fatigue life was derived from the rough cut growth rate equation and verified by comparing with experimental fatigue lives of dumbbell fatigue specimen in various loading condition.

• Journal of the Korea Institute of Military Science and Technology
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• v.21 no.5
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• pp.607-613
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• 2018

Hydraulic systems are widely used in the field of defense, construction machinery, agricultural machinery, and general industries, due to various advantages such as quick response speed and precision control. The defense equipments such as light rescue vehicle is operated in very harsh environments, so hydraulic components used in defense equipment are required to have very high reliability. In particular, hydraulic piston pump is very important component in a hydraulic systems, so life prediction of pump is essential. Therefore, in this study, we analyze the potential failure and the main failure mode of the hydraulic piston pump for the light rescue vehicle through the FMEA analysis, and predict the life of the pump by the accelerated life test considering the usage conditions.

• Journal of the Korean Statistical Society
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• v.25 no.1
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• pp.133-144
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• 1996

We, in this paper, propose a nonparametric estimator of bivariate mean residual life function based on Lin and Ying's (1993) bivariate survival function estimator of paired failure times under univariate censoring and prove the uniform consistency and the weak convergence result of this estimator. Through Monte Carlo simulation, the performances of the proposed estimator are tabulated and are illustrated with the skin grafts data.

• Journal of Applied Reliability
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• v.9 no.1
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• pp.47-58
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• 2009

In this paper, an accelerated life test procedure for a vacuum cleaner motor is proposed. We investigate the failure mechanism of the motor and select some accelerating factors and determine the orifice size as a key accelerating factor. Three stress levels of orifice size are tested and the failure data with censored data are analyzed. The modified accelerating test will reduce the test time in design phase by using the accelerating factor.