• Title/Summary/Keyword: Failure Analysis and Modeling

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FTA Modeling of Water Supply System for Hydro-power Plant (수력발전소 물 공급 설비에 대한 FTA 모형)

  • Jeon, Tae-Bo;Kwon, Chang-Seob
    • Journal of Industrial Technology
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    • v.26 no.B
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    • pp.145-155
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    • 2006
  • High level of reliability in facility operation is specifically required these days. The goal of this study is to secure a methodology for reliability analysis of hydro-power plant so that an appropriate decision for operation and investment can be made. Fault tree analysis of water supply system within hydro-power plant has been performed in this study. We briefly examined the electric power generation facility and water supply system. We then developed fault tree for the water supply system based on failure modes and effects analysis. We conclude this study and provided future research areas.

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Reliability Analysis of Repairable Systems Considering Failure Detection Equipments (고장감지장치를 고려한 수리가능 시스템의 신뢰도 분석)

  • Na, Seong-Ryong
    • The Korean Journal of Applied Statistics
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    • v.24 no.3
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    • pp.515-521
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    • 2011
  • In this paper we consider failure detection equipment that which find failures in repairable systems and enable repair operations. In practical situations, failure detection equipment may come across troubles that can cause the omissions in detecting system failures and have a serious effect on system reliability. We analyze this effect through the appropriate modeling of Markov processes.

The effects of different FRP/concrete bond-slip laws on the 3D nonlinear FE modeling of retrofitted RC beams - A sensitivity analysis

  • Lezgy-Nazargah, M.;Dezhangah, M.;Sepehrinia, M.
    • Steel and Composite Structures
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    • v.26 no.3
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    • pp.347-360
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    • 2018
  • The aim of this paper is to evaluate the accuracy and reliability of the available bond-slip laws which are being used for the numerical modeling of Fiber Reinforced Polymer (FRP)/concrete interfaces. For this purpose, a set of Reinforced Concrete (RC) beams retrofitted with external FRP were modeled using the 3D nonlinear Finite Element (FE) approach. All considered RC beams have been previously tested and the corresponding experimental data are available in the literature. The failure modes of these beams are concrete crushing, steel yielding and FRP debonding. Through comparison of the numerical and experimental results, the effectiveness of each FRP/concrete bond-slip model for the prediction of the structural behavior of externally retrofitted RC beams is assessed. The sensitivity of the numerical results against different modeling considerations of the concrete constitutive behavior and bond-slip laws has also been evaluated. The results show that the maximum allowable stress of FRP/concrete interface has an important role in the accurate prediction of the FRP debonding failure.

Modeling and Simulation of Loss of Excitation of Hydro Generator Control System (수력 발전기 제어시스템의 계자상실 모델링과 시뮬레이션)

  • Park, Chul-Won
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.63 no.2
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    • pp.74-80
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    • 2014
  • Generator protection device has to detects an internal fault conditions in generator and abnormal operating conditions must be due to the hazards. Loss of excitation may cause generator itself failure as well as serious operating problem in power system, and then requires an appropriate response of generator protection device. Details modeling of generator control system and analysis of transient states in generator are important for optimal operation in power plants. In addition, the fault simulation data are also used for testing the characteristics of IED. In this paper, the hydro generator control system using PSCAD/EMTDC, visual simulation for power systems, was modeled. The generator control system which is composed of generator, turbine, exciter, governor was implemented. The parameters of generator control system model were obtained from field power plant. Loss of excitation simulations were performed while varying the fixed load. Several signals analysis were also performed so as to analyze transients phenomena.

A GA-based Rule Extraction for Bankruptcy Prediction Modeling (유전자 알고리즘을 활용한 부실예측모형의 구축)

  • Shin, Kyung-shik
    • Journal of Intelligence and Information Systems
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    • v.7 no.2
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    • pp.83-93
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    • 2001
  • Prediction of corporate failure using past financial data is well-documented topic. Early studies of bankruptcy prediction used statistical techniques such as multiple discriminant analysis, logit and probit. Recently, however, numerous studies have demonstrated that artificial intelligence such as neural networks (NNs) can be an alternative methodology for classification problems to which traditional statistical methods have long been applied. Although numerous theoretical and experimental studies reported the usefulness or neural networks in classification studies, there exists a major drawback in building and using the model. That is, the user can not readily comprehend the final rules that the neural network models acquire. We propose a genetic algorithms (GAs) approach in this study and illustrate how GAs can be applied to corporate failure prediction modeling. An advantage of GAs approach offers is that it is capable of extracting rules that are easy to understand for users like expert systems. The preliminary results show that rule extraction approach using GAs for bankruptcy prediction modeling is promising.

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The Modeling Aging Analysis due to Finite Eliment Method on Epoxy-Mica Composites (에폭시-마이카 복합재료의 FEM에 의한 MODELING 열화 해석)

  • Kim, Hee-Gon;Hyun, Jung-Seob;Kim, Hee-Dong;Jo, Han-Gu
    • Proceedings of the KIEE Conference
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    • 1996.07c
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    • pp.1710-1712
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    • 1996
  • This paper was practiced insulation failure test forcing to accelerate on frequency of 420 HZ. There was manufactured generator stator windings for 500MVA thermal plants and selected accelerating deterioration voltage of 5.5kV/mm for electrical aging. Moreover, so as to verification of this experiments, we carried out modeling analysis due to finite element method using to ANSYS5.0 program for common package and imitated multi-stress aging for analyzing electrical and mechanical stress distribution.

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A Study on the Failure Effect Analysis of Overhead Transformer Considering Weather (기상요인에 따른 가공변압기의 고장영향 분석에 관한 연구)

  • Oh, Do-Eun;Jang, Seung-Min
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.66 no.5
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    • pp.857-862
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    • 2017
  • The management of the electric power facilities became important in accordance with the industrial development and electric power facilities were influenced by weather. Even if the same kind of electric power facilities is estimated for extracting the time-varying failure rate, the failure rate could be different depending on external effect such as climate. This research will show the data mining modeling of the weather-related outage and influence of weather on the electric power facility with recent data.

A Study on the Ultimate Strength Behavior according to Modeling Range at the Stiffened Plate (선체보강판의 모델링범위에 따른 최종강도거동에 관한 연구)

  • Park Jo-Shin;Ko Jae-Yong
    • Proceedings of KOSOMES biannual meeting
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    • 2004.11a
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    • pp.137-141
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    • 2004
  • Ship structures are basically an assembly of plate elements and the load-carrying capacity or the ultimate strength is one of the most important criteria for safety assessment and economic design. Also, Structural elements making up ship plated structures do not work separately, resulting in high degree of redundancy and complexity, in contrast to those of steel framed structures. To enable the behavior of such structures to be analyzed, simplifications or idealizations must essentially be made considering the accuracy needed and the degree of complexity of the analysis to be used. On this study, to investigate effect of modeling range, the finite element method are used and their results are compared varying the analysis ranges. The model has been selected from bottom panels of large merchant ship structures. For FEA, three types of structural modeling are adopted in terms of the extent of the analysis. The purpose of the present study is to numerically calculate the characteristics of ultimate strength behavior according to the analysis ranges of stiffened panels subject to uniaxial compressive loads.

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Comments on a Case Study on Engineering Failure Analysis of Link Chain

  • Yu, George Y.H.
    • Safety and Health at Work
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    • v.12 no.4
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    • pp.544-545
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    • 2021
  • The article by Tae-Gu Kim et al. conducted elastic FE modeling, which was inappropriate for fracture of elastic-plastic chain material (11.3% of elongation). FE analysis results and the findings in the fracto-graphic analysis did not tally but contradicted each other. The article identified "incorrect installation"/bending forces as the root cause while FE results of the chain under bending forces showed very low stresses at fracture locations but the highest stress in the middle of shank of the chain. The article's "step-like topographies indicating the fracture due to bending moment rather than uniaxial tension" lacked scientific support. The load value carried by each chain section under bending/incorrect installation was only half of that under tension, thus the article using same load value in FE simulation comparison for bending and tension was incorrect. The real cause of the chain fracture was likely improper checking the lifted load or/and using the wrong chain with much lower safety working load.

Finite element modeling methodologies for FRP strengthened RC members

  • Park, Sangdon;Aboutaha, Riyad
    • Computers and Concrete
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    • v.2 no.5
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    • pp.389-409
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    • 2005
  • The Finite Element Analysis (FEA) is evidently a powerful tool for the analysis of structural concrete having nonlinearity and brittle failure properties. However, the result of FEA of structural concrete is sensitive to two modeling factors: the shear transfer coefficient (STC) for an open concrete crack and force convergence tolerance value (CONVTOL). Very limited work has been done to find the optimal FE Modeling (FEM) methodologies for structural concrete members strengthened with externally bonded FRP sheets. A total of 22 experimental deep beams with or without FRP flexure or/and shear strengthening systems are analyzed by nonlinear FEA using ANAYS program. For each experimental beams, an FE model with a total of 16 cases of modeling factor combinations are developed and analyzed to find the optimal FEM methodology. Two elements the SHELL63 and SOLID46 representing the material properties of FRP laminate are investigated and compared. The results of this research suggest that the optimal combination of modeling factor is STC of 0.25 and CONVTOL of 0.2. A SOLID 46 element representing the FRP strengthening system leads to better results than a SHELL 63 element does.