• 한국데이터정보과학회:학술대회논문집
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• 2002.06a
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• pp.89-95
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• 2002

This paper considers the problem of estimating paramaters of the bivariate exponential distribution with a loaction parameter for a two-component shared parallel system using component data from system-level life test terminated at the time of the prespecified number of system failure. In the system-level life testing, there are three patterns of failure types; 1) both component failed 2) both component censored 3) one is failed and the other is censored. In the third case, we assume that the failure time might be known or unknown. The maximum likelihood estimators are obtained for the case of known/unknown failure time when the other component is censored.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.2
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• pp.161-169
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• 2017

Recently, ship owners have been requiring the assessment of the maneuverability of twin-screw ships under mechanical failures. Because this kind of assessment has not yet been conducted, it is necessary to study the types of machinery failures that can significantly affect the maneuverability of a ship, and to construct a procedure to simulate the maneuvering behavior under such failures. In this paper, the sole focus is the steering system failure from among the variety of failure types, and the maneuvering behavior of the ship under the single rudder failure is simulated for an investigation of the unique characteristics. First, the mathematical model for the twin-screw container ship is verified by comparing the simulated results for the $35^{\circ}$ turning test, $10^{\circ}/10^{\circ}$ zigzag test, and $20^{\circ}/20^{\circ}$ zigzag test under the normal operating condition with those obtained from free running model tests. After the IMO maneuvering tests are additionally simulated under the single rudder failure, the results are reviewed to investigate the maneuvering characteristics that are due to the failure. Further, the $35^{\circ}/35^{\circ}$ zigzag test and the $35^{\circ}$ turning test are simulated to additionally investigate the effects of the single rudder failure on the steering and turning abilities.

• Journal of Korean Society for Quality Management
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• v.26 no.1
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• pp.99-107
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• 1998

This paper presents a software reliability model that is based on a nonhomogeneous poisson process. The major contribution of this model is combining multiple failure types with imperfect debugging by use of S-shaped mean value function. The software reliability model allows for three different types of errors: Critical errors are the most difficult to detect and the most expensive to remove. Major errors are moderately difficult to detect and fairly expensive to remove. Minor errors are easy to detect and inexpensive to remove. The model also allows for the introduction of any of these types of errors during the removal of an error. A numerical example is provided to illustrate the above techniques.

• Computers and Concrete
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• v.32 no.5
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• pp.499-511
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• 2023

Anchor channels are commonly used for façade, tunnel, and structural connections. These connections encounter various types of loadings during their service life, including high rate or impact loading. For anchor channels that are placed close and parallel to an edge and loaded in shear perpendicular to and towards the edge, the failure is often governed by concrete edge breakout. This study investigates the transverse shear behavior of the anchor channels under quasi-static and high rate loadings using a numerical approach (3D finite element analysis) utilizing a rate-sensitive microplane model for concrete as constitutive law. Following the validation of the numerical model against a test performed under quasi-static loading, the rate-sensitive static, and rate-sensitive dynamic analyses are performed for various displacement loading rates varying from moderately high to impact. The increment in resistance due to the high loading rate is evaluated using the dynamic increase factor (DIF). Furthermore, it is shown that the failure mode of the anchor channel changes from global concrete edge failure to local concrete crushing due to the activation of structural inertia at high displacement loading rates. The research outcomes could be valuable for application in various types of connection systems where a high rate of loading is expected.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.6 no.1
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• pp.43-49
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• 2010

The piping failure probability of the reactor coolant system in Kori unit 1 was evaluated considering stress corrosion cracking. The P-PIE program (Probabilistic Piping Integrity Evaluation Program) developed in this study was used in the analysis. The effect of some variables such as oxygen concentration during start up and steady state operation, and operating temperature, which are related with stress corrosion cracking, on the piping failure probabilities was investigated. The effects of leak detection capability, the size of big leak, piping loops, and reactor types on the piping failure probability were also investigated. The results show that (1) LOCA (loss of coolant accident) probability of Kori unit 1 is extremely low, (2) leak probability is sensitive to oxygen concentration during steady state operation and operating temperature, while not sensitive to the oxygen concentration during start up, and (3) the piping thickness and operating temperature play important roles in the leak probabilities of the cold leg in 4 reactor types having same inner diameter.

• Structural Engineering and Mechanics
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• v.49 no.2
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• pp.237-259
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• 2014

Wind-induced failure around screwed connections has been documented in roof and wall cladding systems made with steel sheet cold-formed panels during high wind events. Previous research has found that low cycle fatigue caused by stress concentration and fluctuating wind loads is responsible for most such failures. A dynamic load protocol was employed in this work to represent fatigue under wind effects. A finite element model and fatigue criteria were implemented and compared with laboratory experiments in order to predict the fatigue failure associated with fluctuating wind loads. Results are used to develop an analytical model which can be employed for the fatigue analysis of steel cold-formed cladding systems. Existing three dimensional fatigue criteria are implemented and correlated with fatigue damage observed on steel claddings. Parametric studies are used to formulate suitable yet simple fatigue criteria. Fatigue failure is predicted in different configurations of loads, types of connections, and thicknesses of steel folded plate cladding. The analytical model, which correlated with experimental results reported in a companion paper, was validated for the fatigue life prediction and failure mechanism of different connection types and thicknesses of cold-formed steel cladding.

• Computational Structural Engineering : An International Journal
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• v.3 no.1
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• pp.9-17
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• 2003

This paper aims at investigating the damage process of steel members leading to the failure under strong repeated loading, proposing the damage index using various factors related to the damage, and developing the analysis method for evaluating the damage state. Cantilever-type steel members were analyzed under uniaxial load and combined with a constant axial load, considering a horizontal displacement history. In analyzing the models, loading patterns and steel types (SS400, SM570, Posten80) were considered as main parameters. From the analysis results, the effects of parameter on the failures mode, the deformation capacity, the damage process are also discussed. Each failure process was compared as steel types. Consequently, the failure of steel members under strong repeated loading was determined by loading. Especially it was seen that the state of the failure is closely related to the local strain.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.7
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• pp.643-651
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• 2011

An experimental study on the failure of aluminum sandwich joints under shear loading was conducted. A total of 60 specimens including three different insert types and two different potting types were fabricated and tested. The test results showed that the through-clearance type of joint fails at the highest load among insert type joints. The failure load of the potted joints with the dimple washer increased by 10% compared to the simple potted joints. As expected, the shear failure load became higher in accordance with the face thickness increase. It was also found that the upper face in contact with the loading tool is more dominant over the failure load.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.04a
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• pp.59-63
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• 2005

Compression tests were performed for six types of hat stiffened composite panels with different bonding methods and stiffener section shapes. Six panels showed similar behaviors in buckling and post-buckling region before a skin-stiffener separation failure occurred. The skin-stiffener separation failures occurred in the panels with closed type stiffeners regardless of bonding methods, but not in the panels with open type stiffeners. The separation failures not only reduced the postbuckling strength but also changed buckling mode and postbuckling stiffness. All the separation failures were initiated at the stiffener flange edges closest to skin buckling crests. The co-cured or secondary bonded panels with open type stiffeners had the largest structural performance. Because the post-buckling strength and performance of the composite stiffened panels are reduced by the separation failure, it is important to find bonding methods, stiffener types and manufacturing parameters for preventing of the separation failure.

• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.607-612
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• 2005

Check valves playa vital role in the operation and protection of nuclear power plants. Check valves failure in nuclear power plants often lead to a plant transient or trip. An overview of the failure history of check valves needs to identify key area where resources can be best applied to further improve their reliability, and provide cost effective means for failure reduction. The analysis of historical failure data gives information on the populations of various types of check valves, the systems they are installed in, failure modes, effects, methods of detection, and the mechanisms of the failures. The results presented are based on information derived from operating records, nuclear industry reports, manufacturer supplied information. A majority of check valve failures are caused by improper application. Failure modes are identified for swing and lift check valves. Failures involving improper seating and valve disc stuck comprised the largest percentage of failures.