• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.8
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• pp.1457-1465
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• 2016

A RCM approach to maintenance of the catenary system of electric railway is proposed. The proposed RCM approach provides a maintenance-oriented FMECA procedure to derive critical failure modes by analyzing failure effects and a RCM decision logic tree to suggest optimal maintenance works for the derived failure modes. By applying the proposed RCM procedures to the catenary system of high speed railway, it is suggested that strand breaks of dropper and voltage equalizing wire, and trolly wire wear-out are the critical failure modes for whom maintenance works based on condition monitoring should be applied instead of conventional time-based preventive maintenance. It is also proposed by reliability analysis that replacement time of dropper can be reduced from 18 years to 10 years. These results show that the proposed RCM approach can optimize the maintenance procedures of catenary system.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.89-92
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• 2002

Traditionally unidirectional laminated composite which are characterized by high specific stiffness and strength were used for structural application. But theses composites are highly susceptible to impact damage because of lower transverse tensile strength. The main failure modes of laminated composite are fiber breakage, matrix cracking and delamination for low velocity impact. The modified failure criterions are implemented to predict these failure modes with finite element analysis. Failure behavior of the woven fabric laminated composite which is used in forehead part of subway to lighten weigh has been studied. The new failure criterions are in good agreement with experimental results and can predict the failure behavior of the woven fabric composite plate subjected to low velocity impact more accurately.

• 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.

• Journal of the Korean Geotechnical Society
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• v.15 no.6
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• pp.3-16
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• 1999

This paper presents the results of sensitivity analysis based on an example study to verify a newly developed reliability-based model for rock slopes considering uncertainties of discontinuities and failure modes-plane, wedge, and toppling. The parameters that are needed for sensitivity analysis are the variability of discontinuity properties (orientation and strength of discontinuities), the loading conditions, and the rock slope geometry. The variability in orientation and friction angle of discontinuities, which can not be considered in the deterministic analysis, has a great influence on the rock slope stability, The stability of rock slopes including failure modes is more influenced by the selection of dip direction of cutting rock face than any other design variables, The example study shows that the developed reliability-based analysis model can reasonably assess the stability of rock slope.

• Structural Engineering and Mechanics
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• v.32 no.4
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• pp.531-547
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• 2009

This paper presents the experimental results on the strength behavior and failure modes of box beam-to-circular column connections in steel piers. Previous research introduced parameters such as joint central angles, extension of horizontal stiffeners, and use of equivalent web depth, which ignored strength behavior and failure modes of box beam-to-circular column connections. The use of equivalent web depth $d_2$ is not reasonable when central angle ${\alpha}$ is closer to $90^{\circ}$; therefore, a monotonic loading test has been performed for eight connection specimens. From the test, it is identified that the connection with the circular column is stronger than the connection with the box-sectioned substitution column. Also, the strength of the beam-to-column connections with horizontal stiffeners is higher than the one of the no column stiffeners. The concrete-filled effect of box beam-to-circular column connection is also investigated, and the experimental yield strength of the connection is compared with the theoretical one. Also, more a reasonable equivalent web depth is suggested. The failure modes of connection are clearly defined.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.8
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• pp.870-879
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• 2007

In this study, various damage modes in bending unimorph piezoelectric composite actuators with a thin sandwiched PZT plate during bending fracture tests have been evaluated by monitoring acoustic emission (AE) signals in terms of waveform and peak frequency as well as AE parameters. Three kinds of actuator specimens consisting of woven fabric fiber skin layers and a PZT ceramic core layer are loaded with a roller and an AE activity from the specimen is monitored during the entire loading using an AE transducer mounted on the specimen. AE characteristics from a monolithic PZT ceramic with a thickness of $250{\mu}m$ are examined first in order to distinguish different AE signals from various possible damage modes in piezoelectric composite actuators. Post-failure observations and stress analyses in the respective layers of the specimens are conducted to identify particular features in the acoustic emission signal that correspond to specific types of damage modes. As a result, the signal classification based on waveform and peak frequency analyses successfully describes the failure process of the bending piezoelectric composite actuator exhibiting diverse failure mechanisms. Furthermore, it is elucidated that when the PZT ceramic embedded actuators are loaded mechanical bending loads, the failure process of actuator specimens with different lay-up configurations is almost same irrespective of their lay-up configurations.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.4
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• pp.565-578
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• 2016

A probabilistic based systems approach is addressed in this study for the reliability prediction of solid rocket motors (SRM). To achieve this goal, quantitative Failure Modes, Effects and Criticality Analysis (FMECA) approach is employed to determine the reliability of components, which are integrated into the Fault Tree Analysis (FTA) to obtain the system reliability. The quantitative FMECA is implemented by burden and capability approach when they are available. Otherwise, the semi-quantitative FMECA is taken using the failure rate handbook. Among the many failure modes in the SRM, four most important problems are chosen to illustrate the burden and capability approach, which are the rupture, fracture of the case, and leak due to the jointed bolt and O-ring seal failure. Four algorithms are employed to determine the failure probability of these problems, and compared with those by the Monte Carlo Simulation as well as the commercial code NESSUS for verification. Overall, the study offers a comprehensive treatment of the reliability practice for the SRM development, and may be useful across the wide range of propulsion systems in the aerospace community.

• Nuclear Engineering and Technology
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• v.35 no.2
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• pp.154-164
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• 2003

The explicit consideration of different pressurization rates in estimating the probabilities of containment failure modes has a profound effect on the confidence of containment performance evaluation that is so critical for risk assessment of nuclear power plants. Except for the sophisticated NUREG-1150 study, many of the recent containment performance analyses (through Level 2 PSAs or IPE back-end analyses) did not take into account an explicit distinction between slow and fast pressurization in their analyses. A careful investigation of both approaches shows that many of the approaches adopted in the recent containment performance analyses exactly correspond to the NUREG-1150 approach for the prediction of containment failure mode probabilities in the presence of fast pressurization. As a result, it was expected that the existing containment performance analysis results would be subjected to greater or less conservatism in light of the ultimate failure mode of the containment. The main purpose of this paper is to assess potential conservatism of a plant-specific containment performance analysis result in light of containment failure mode probabilities.

• Structural Engineering and Mechanics
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• v.8 no.5
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• pp.491-504
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• 1999

The initiation of toppling is explored for a uniform stack of blocks that rotates slowly about its mid-base. As the stack passes through its vertical position ($\theta$=0), it is in free-fall rotation, and a critical inclination angle ${\theta}_c$ is reached at which the toppling stack "fails" or begins to crack or separate. For tall stacks (high aspect ratios), two modes of failure are hypothesized, for which the dynamic failure analyses are shown to correlate with experimental results. These block failure modes are similar to those observed for tall, toppling masonry structures with weak binding material between their brick or stone blocks.

• Journal of the Korean Geotechnical Society
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• v.28 no.7
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• pp.5-16
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• 2012

Soil-nailing is the most popular method of reinforcing for slope stability. In general, two factors are considered as failure modes during the soil-nailing design stages: pullout failure mode and shear failure mode that will occur on the most probable failure plane. In many cases, however, shallow failure can also occur when the ground near the slope face is swept away by the horizontal stress release during the staged top-down excavation. In this paper, an optimized soil-nailing design methodology is proposed by considering the three failure modes mentioned above: pullout failure; shear failure; and shallow failure. The variables to be optimized include the bonded length and number of soil-nailings, and the confining pressure that should be applied at the slope face. The procedure to obtain the optimized design variables is as follows: at first, optimization of soil-nailings, i.e. bonded length and number, against pullout and shear failure modes; and then, optimization of confining pressure at each excavation stage that is needed to prevent shallow failure. Since the two processes are linked with each other, they are repeated until the optimized design variables can be obtained satisfying all the constrained design requirements in both of the two processes.