• Journal of the Korean Society of Safety
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• v.28 no.1
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• pp.74-80
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• 2013

This study describes structural reliability analysis of actively-controlled structure for which random vibration analysis is incorporated into the first-order reliability method (FORM) framework. The existing approaches perform the reliability analysis based on the RMS response, whereas the proposed study uses the peak response for the reliability analysis. Therefore, the proposed approach provides us a meaningful performance measure of the active control system, i.e., realistic failure probability. In addition, it can deal with the uncertainties in the system parameters as well as the excitations in single-loop reliability analysis, whereas the conventional random vibration analysis requires double-loop reliability analysis; one is for the system parameters and the other is for stochastic excitations. The effectiveness of the proposed approach is demonstrated through a numerical example where the proposed approach shows fast and accurate reliability (or inversely failure probability) assessment results of the dynamical active control system against random seismic excitations in the presence of parametric uncertainties of the dynamical structural system.

• Journal of the Korean Society for Railway
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• v.7 no.4
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• pp.356-359
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• 2004

In this paper, as the first step to assess and enhance the reliability of Korea High Speed Train, auxiliary power system is selected and reliability analysis is carried out. The auxiliary power system is classified into subsystems and functional analysis is conducted. Reliability block diagrams are drawn and reliability parametric analysis is performed. Analysis results show that the reliability of auxiliary power system depends on critical items. To grow the system reliability, activities should be concentrated on improvement of critical items.

• IE interfaces
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• v.10 no.2
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• pp.41-50
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• 1997

This paper considers the reliability computation of the network with dependent components and a software system is developed for supporting the reliability analysis and improvement of the system reliability. At first, We propose the common cause failure and load sharing models as the typical models considering the dynamic behaviors of networks with dependent components. Secondly, the algorithm is proposed to obtain the network reliability and reliability importance of component. The software, Delphi, is used to develop the our reliability analysis system.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.17 no.1
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• pp.24-28
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• 2009

The reliability assessment is performed for Pressure Control Regulator of Aircraft Fuel System using reliability procedure which consists of the reliability analysis and the Failure Modes and Effects Analysis(FMEA). The target reliability as MTBF(Mean Time Between Failure) is set to 5000hr. During the reliability analysis process, the system is categorized by Work Breakdown Structure(WBS) up to level 3, and a reliability structure is defined by schematics of the system. Since the components and parts that have been collected through EPRD/NPRD. The predicted reliability to meet mission requirements and operating conditions is estimated as 4375.9hr. To accomplish the target reliability, the components and parts with high RPN have been identified and changed by analyzing the potential failure modes and effects. By changing the configuration design of components and parts with high-risk, the design is satisfied target reliability.

• Journal of the Korean Society of Safety
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• v.29 no.4
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• pp.116-122
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• 2014

This study proposes a system reliability analysis of rack storage facilities subjected to forklift colliding events. The proposed system reliability analysis consists of two steps: the first step is to identify dominant failure modes that most contribute to the failure of the whole rack facilities, and the second step is to evaluate the system failure probability. In the first step, dominant failure modes are identified by using a simulation-based selective searching technique where the contribution of a failure mode to the system failure is roughly estimated based on the distance from the origin in the space of the random variables. In the second step, the multi-scale system reliability method is used to compute the system reliability where the first-order reliability method (FORM) is initially used to evaluate the component failure probability (failure probability of one member), and then the probabilities of the identified failure modes and their statistical dependence are evaluated, which is called as the lower-scale reliability analysis. Since the system failure probability is comprised of the probabilities of the failure modes, a higher-scale reliability analysis is performed again based on the results of the lower-scale analyses, and the system failure probability is finally evaluated. The illustrative example demonstrates the results of the system reliability analysis of the rack storage facilities subjected to forklift impact loadings. The numerical efficiency and accuracy of the approach are compared with the Monte Carlo simulations. The results show that the proposed two-step approach is able to provide accurate reliability assessment as well as significant saving of computational time. The results of the identified failure modes additionally let us know the most-critical members and their failure sequence under the complicated configuration of the member connections.

• Journal of the Korean Society of Systems Engineering
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• v.12 no.1
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• pp.105-112
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• 2016

An aircraft must be designed to minimize system failure rate for obtaining the aircraft safety, because the aircraft system failure causes a fatal accident. The safety of the aircraft system can be predicted by analyzing availability, reliability, and maintainability of the system. In this study, the reliability and the maintainability of the hydraulic system are analysed except the availability, and therefore the reliability and the maintainability analysis process and the results are presented for a helicopter hydraulic system. For prediction of the system reliability, the failure rate model presented in MIL-HDBK-217F is used, and MTBF is calculated by using the Part Stress Analysis Prediction and quality/temperature/environmental factors described in NPRD-95 and MIL-HDBK-338B. The maintainability is predicted by FMECA(Failure Mode, Effect & Criticality Analysis) based on MIL-STD-1629A.

• International Journal of Reliability and Applications
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• v.16 no.2
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• pp.99-111
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• 2015

In this paper, we study the reliability analysis of a repairable system with two types of failure in which switching failures and reboot delay are considered. Let units in this system be cold standby, and failure rate and repair rate of [type1, type2] components be exponentially distributed. The expressions of reliability characteristics - such as the system reliability and the mean time to system failure MTTF - are derived. We use several cases to graphically analyze the effect of various system parameters on the system reliability and MTTF. We also perform a sensitivity analysis of the reliability characteristics with changes in specific values of the system's parameters.

• Korean Journal of Computational Design and Engineering
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• v.18 no.2
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• pp.138-147
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• 2013

The liquefaction process system is regarded as primary among all topside systems in LNG FPSO. This liquefaction process system is composed of many types of equipment. LNG equipment on offshore plants has quite different demands on the equipment compared to traditional onshore LNG plants, so the reliability analysis of this process system needs to be performed. This study investigates how DEVS formalism for discrete event simulation can be used to reliability analysis of the liquefaction cycle for LNG FPSO. The reliability analysis method based on DEVS formalism could be better model for reflecting the system configuration than the conventional reliability analysis methods, such as fault tree analysis and event tree analysis.

• Journal of Power Electronics
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• v.6 no.2
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• pp.104-113
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• 2006

Satellites have provided the impetus for the orderly development of reliability engineering research and analysis because they tend to have complex systems and hence acute problems. They were instrumental in developing mathematical models for reliability, as well as design techniques to permit quantitative specification, prediction and measurement of reliability. Reliability engineering is based on implementing measures which insure an item will perform its mission successfully. The discipline of reliability engineering consists of two fundamental aspects; $(1^{st})$ paying attention to details, and $(2^{nd})$ handling uncertainties. This paper uses some of the basic concepts, formulas and examples of reliability theory in application. This paper emphasizes the practical reliability analysis of a Low Earth Orbit (LEO) Micro-satellite power subsystem. Approaches for specifying and allocating the reliability of each element of the power system so as to meet the overall power system reliability requirements, as well as to give detailed modeling and predicting of equipment/system reliability are introduced. The results are handled and analyzed to form the final reliability results for the satellite power system. The results show that the Electric Power Subsystem (EPS) reliability meets the requirements with quad microcontrollers (MC), two boards working as main and cold redundant while each board contains two MCs in a hot redundant.

• IE interfaces
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• v.6 no.2
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• pp.67-78
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• 1993

In this paper, we deal with the application of the fuzzy sets theory to evaluate and estimate the system reliability under the fault tree analysis. We formulate the uncertainty of component reliability to fuzzy sets, and propose a procedure for obtaining the system reliability in case the system structure is described by fault tree. An importance measure of each component is proposed. Computer program for fuzzy fault tree analysis(FFTA) is developed using C language to obtain the system reliability and the component‘s fuzzy importance.