• IEMEK Journal of Embedded Systems and Applications
• /
• v.13 no.4
• /
• pp.205-214
• /
• 2018

The reliability test is a crucial step for ensuring robustness of high-cost and complex weapon systems. In this paper, we present a set of quantitative criteria to select critical parts or components in weapon systems for the reliability test, and implement a fuzzy inference system by applying developed criteria to fuzzy theory. We classify the selection criteria of critical parts or components into four fuzzy sets and membership functions. A fuzzy inference rule is proposed based on the AHP (Analytic Hierarchy Process) analysis technique so as to derive a convincing reliability test. The credibility of the fuzzy inference system is confirmed through a case study using actual equipment data exacted from an existent weapon system.

• Earthquakes and Structures
• /
• v.7 no.6
• /
• pp.1061-1070
• /
• 2014

An iterative hybrid structural dynamic reliability prediction model has been developed under multiple-time interval loads with and without consideration of stochastic structural strength degradation. Firstly, multiple-time interval loads have been substituted by the equivalent interval load. The equivalent interval load and structural strength are assumed as random variables. For structural reliability problem with random and interval variables, the interval variables can be converted to uniformly distributed random variables. Secondly, structural reliability with interval and stochastic variables is computed iteratively using the first order second moment method according to the stress-strength interference theory. Finally, the proposed method is verified by three examples which show that the method is practicable, rational and gives accurate prediction.

• Smart Structures and Systems
• /
• v.14 no.4
• /
• pp.559-567
• /
• 2014

The model of unit dynamic reliability of repairable k/n (G) system with unit strength degradation under repeated random shocks has been developed according to the stress-strength interference theory. The unit failure number is obtained based on the unit failure probability which can be computed from the unit dynamic reliability. Then, the transfer probability function of the repairable k/n (G) system is given by its Markov property. Once the transfer probability function has been obtained, the probability density matrix and the steady-state probabilities of the system can be retrieved. Finally, the dynamic reliability of the repairable k/n (G) system is obtained by solving the differential equations. It is illustrated that the proposed method is practicable, feasible and gives reasonable prediction which conforms to the engineering practice.

• Proceedings of the KSR Conference
• /
• 2005.05a
• /
• pp.187-192
• /
• 2005

Under development program for a complex system, the total system or major subsystems are tested to failure, system failure modes are analyzed, and design and engineering changes are made to eliminate these failure modes. If this TAAF(test-analyze-and-fix) process is continued, and modifications are made in a competent manner, then the system reliability increase. This paper presents the reliability growth theory and applies it to some subsystems during their development and initial production testing. The application of these techniques is a part of the product assurance function that plays an important role in product reliability improvement. In addition, the EN 50126 requires essentially reliability growth for RAM growth monitoring.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.20 no.2
• /
• pp.1-7
• /
• 2012

A Failure data from operating condition includes various failures. Reliability evaluation by operating condition is more correct than test condition. Additional, the evaluation result by operating condition is widely used for quality assurance, forecasting amount of manufacturing at EOL. To discover valuable things from the failure data, arrangement of the failure data and information technique to handle data is needed among many failure data. This paper introduces a reliability prediction program to solve this problem based on the failure. And new technologies for parameters estimation with method of Graphic-Wizard-Parameters-Estimation and Genetic Algorithm are introduced.

• Journal of the Korean Society of Safety
• /
• v.21 no.2 s.74
• /
• pp.1-6
• /
• 2006

It is well known that pipelines have the highest capacity and are the safest and least environmentally disruptive form of transporting oil and gas. However, pipeline damage caused by both internal and external corrosion is a major concern threatening the reliability of oil and gas transportation and the soundness of the pipeline structure. In this study, we estimate the allowable damage by comparing the ASTM B31G code to a modified theory considering diverse detailed corrosive forms. The ASTM B31 G code has been developed as the evaluation method for reliability and incident prevention of damaged pipelines based on the amount of loss due to corrosion and the yield strength of materials. Furthermore, we suggest a method for estimating the expected life span of used pipelines by utilizing the reliability method based on major variables such as the depth and length of damage and the corrosion rate affecting the life expectancy of the pipelines.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1990.10a
• /
• pp.85-90
• /
• 1990

Current steel pile foundation design is bared an WSD, but the reliability based design method is more rational than the WSD. For this reason, this study proposes a reliability Index of the pile foundation by LFD which is most common type of pile foundation, and also proposes the theoretical bases of nominal safety factors of stability analysis by introducing the reliability theory. The measured bearing capacity data are analyzed to the descriptive statistics and classified into the four models of uncorrelated -normal(UNNO), uncorrelated -nonnormal(UNNN), correlated -normal(CONO), and correlated nonnormal (CONN). This study presents the comparisons of reliability index and check points using the AFSOM with respect to the four models as well as BASIC program.

• Journal of the Korea Society for Simulation
• /
• v.10 no.2
• /
• pp.61-74
• /
• 2001

The reliability evaluation of the large scale network becomes very complicate according to the growing size of network. Moreover if the reliability is not constant but follows probability distribution function, it is almost impossible to compute them in theory. This paper studies the network evaluation methods in order to overcome such difficulties. For this an efficient path set algorithm which seeks the path set connecting the start and terminal nodes efficiently is developed. Also, various variance reduction techniques are applied to compute the system reliability to enhance the simulation performance. As a numerical example, a large scale network is given. The comparisons of the path set algorithm and the variance reduction techniques are discussed.

• Structural Engineering and Mechanics
• /
• v.45 no.2
• /
• pp.201-209
• /
• 2013

A new dynamic reliability analysis of structure under repeated random loads is proposed in this paper. The proposed method is developed based on the idea that the probability density of several times random loads can be derived from the probability density of single-time random load. The reliability prediction models of structure based on time responses under several times random loads with and without strength degradation are obtained by using the stress-strength interference theory and probability density evolution method. The resulting differential equations in the prediction models can be solved by using the forward finite difference method. Then, the probability density functions of strength redundancy of the structures can be obtained. Finally, the structural dynamic reliability can be calculated using integral method. The efficiency of the proposed method is demonstrated numerically through a speed reducer. The results have shown that the proposed method is practicable, feasible and gives reasonably accurate prediction.

• Proceedings of the KIEE Conference
• /
• summer
• /
• pp.195-198
• /
• 2004

In recent, the Importance and necessity of some studies on reliability evaluation of grid comes from the recent black-out accidents occurred in the world. The quantity evaluation of transmission system reliability is very important under competitive electricity environment. Accurate probabilistic reliability evaluation depends on assessment of forced outage rate of elements, generators, transmission lines. This paper describes basic theory of relationship between outage rates and reliability evaluation for assessing FOR(forced outage rate) of elements of power system. In case study, FORs assessed and supplied from Canada Electricity Association is introduced and FORs assessed from using actual historical data from 1997 to 2002 for transmission lines of KEPCO system.