• Title/Summary/Keyword: Fatigue Integrity

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A Study on the Evaluation Technology of Welds Integrity in Nuclear Power Plants

  • Chang, Hyun-Young;Kim, Jong-Sung;Jin, Tae-Eun
    • Corrosion Science and Technology
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    • v.6 no.1
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    • pp.29-32
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    • 2007
  • The final goal of this study is to develop the core technologies applicable to the design, operation and maintenance of welds in nuclear structures. This study includes predicting microstructure changes and residual stress for welded parts of nuclear power plant components. Furthermore, researches are performed on evaluating fatigue, corrosion, and hydrogen induced cracking and finally constructs systematically integrated evaluation system for structural integrity of nuclear welded structures. In this study, metallurgical and mechanical approaches have been effectively coordinated considering real welding phenomena in the fields of welds properties such as microstructure, composition and residual stress, and in the fields of damage evaluations such as fatigue, corrosion, fatigue crack propagation, and stress corrosion cracking. Evaluation techniques tried in this study can be much economical and effective in that it uses theoretical/semi-empirical but includes many additional parameters that can be introduced in real phenomena such as phase transformation, strength mismatch and residual stress. It is clear that residual stress makes great contribution to fatigue and stress corrosion cracking. Therefore the mitigation techniques have been approached by reducing the residual stress of selected parts resulting in successful conclusions.

The Fatigue life evaluation and load history measurement for Bogie frame of locomotive (디젤기관차 대차프레임의 하중이력 측정 및 피로수명평가)

  • Seo, Jung-Won;Kwon, Suck-Jin;Ham, Young-Sam;Kwon, Sung-Tae
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.378-383
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    • 2008
  • Bogie frame of the locomotive is an important structural member for the support of vehicle loading. A lot of study has been carried out for the prediction of the structural integrity of the bogie frame in experimental and theoretical domains. The objective of this paper is to estimate the structural integrity of the bogie frame. Strength analysis has been performed by finite element analysis. From these analysis, stress concentration areas were investigated. For evaluation of the loading conditions, dynamic stress were measured by using strain gage. It has been found that the stress and strain due to the applied loads were multi-axial condition according to the location of strain gage. The fatigue strength evaluations of the bogie frame are performed to investigate the effect of the multi-axial load through the employment of the critical plane approach.

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Assessment of Internal Leak on RCS Pressure Boundary Valves (원자로냉각재계통 압력경계밸브 내부누설 평가)

  • Park, Jun-Hyun;Moonn, Ho-Rim;Jeong, Ill-Seok
    • Proceedings of the KSME Conference
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    • 2001.06a
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    • pp.322-327
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    • 2001
  • The internal leaks of RCS pressure boundary valves may cause thermal fatigue crack because of the TASCS in RCS branch line. After experienced unisolable piping failures in several PWR plants, many studies have peformed to understand these phenomena and various methods were applied to ensure the structural integrity of piping. In this paper, the cause of unisolable piping failures and the alternatives to prevent recurrence of failure were reviewed. Also, the severity of piping failure including susceptibility of valve leaks was evaluated for the Westinghouse 2-loop plant. The length of turbulent penetration on RHR inlet piping was measured and, thermal fluid analysis and fatigue analysis was performed for this piping. As a means of ensuring the structural integrity, temperature monitoring and specialized UT and other alternatives were compared for the further application.

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Development of Assessment System for Pipeline Integrity (매설배관의 건전성 평가 시스템 개발)

  • 이억섭;윤해룡
    • Journal of the Korean Society for Precision Engineering
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    • v.20 no.8
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    • pp.158-165
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    • 2003
  • The object of this work is to develop an assessment system for pipeline integrity. The internal algorithm and the database of the system are described in this paper. The system consists of four module applications; the effect of corrosion in pipeline, crack, SCC (stress corrosion cracking) and fatigue module. The database of the system is separated to mainly four parts; geometry of pipeline, material properties, boundary condition and general properties. This system may give a guideline for maintenance and modifications.

Effect of Stringers in Stiffened Panel under Varying Fatigue Load (일정진폭 및 변동하중을 받는 보강판에서 보강재가 피로균열전파에 미치는 영향)

  • 이억섭;이윤표
    • Journal of the Korean Society for Precision Engineering
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    • v.20 no.2
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    • pp.136-145
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    • 2003
  • The integrity of stiffened panels with stringers in airplane structure is generally enhanced by investigating the fatigue crack propagation behavior in detail and providing the technical methodology to deal with the propagating crack. This paper attempts to clarify the effect of load-ratio on the fatigue crack propagation rate and the fatigue life for the thin aluminum 2024-T3. Both the variable and the constant fatigue loading conditions are considered for the fatigue crack propagation behavior in stiffened panels with stringers.

Development of Fitness for Service Evaluation Programs (기간설비 사용적합성 평가 프로그램 개발)

  • Park, Young-Jae;Yun, Kang-Ok;Chang, Yoon-Suk;Kim, Young-Jin;Cho, Kyung-Shik
    • Proceedings of the KSME Conference
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    • 2004.11a
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    • pp.160-165
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    • 2004
  • An effective integrity evaluation system is essential to manage the fitness for service issues on infra-structure because the evaluation processes usually take long times and are detrimental for productivity point of view. In this paper, the key structures and procedures of four integrity evaluation programs which have been developed based on currently available codes and standards are described. The proposed programs are not only flexible to adopt advances in fitness for purpose type assessment methodologies but also convenient for field engineers. The developed programs which will be unified as an integrity evaluation system are expected to play a prominent role for integrity evaluation of major infra-structure.

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Probabilistic Fatigue Life Evaluation of Rolling Stock Structures (철도차량 구조물의 확률론적 피로수명 평가)

  • 구병춘;서정원
    • Transactions of the Korean Society of Automotive Engineers
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    • v.11 no.5
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    • pp.89-94
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    • 2003
  • Rolling stock structures such as bogie frame and car body play an important role for the support of vehicle leading. In general, more than 25 years' durability is needed for them. A lot of study has been carried out for the prediction of the fatigue life of the bogie frame and car body in experimental and theoretical domains. One of the new methods is a probabilistic fatigue lift evaluation. The objective of this paper is to estimate the fatigue lift of the bogie frame of an electric car, which was developed by the Korea Railroad Research Institute (KRRI). We used two approaches. In the first approach probabilistic distribution of S-N curve and limit state function of the equivalent stress of the measured stress spectra are used. In the second approach, limit state function is also used. And load spectra measured by strain gauges are approximated by the two-parameter Weibull distribution. Other probabilistic variables are represented by log-normal and normal distributions. Finally, reliability index and structural integrity of the bogie frame are estimated.

A Study on the Fatigue Crack Propagation of Partly Heat Treated Medium Carbon Steel (부분 열처리한 기계 구조용 탄소강의 피로균열 전파에 관한 연구)

  • 김상철;김선용
    • Journal of the Korean Society of Safety
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    • v.8 no.1
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    • pp.13-20
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    • 1993
  • It is well known that mechanisms of fracture and fatigue crack propagation depend upon various characteristics such as environmental condition. crack geometry. heat treatment and mechanical properties. It seems to be important for the detailed evaluation of structural integrity to investigate the effects of the above factors on the behavior of structural components which contain flaws. In this paper. it is studied that the fatigue crack propagation of partly heat treated medium carbon steel (SM45C) by high frequency heat treatment.

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Fatigue crack propagation life evaluation of an autofrettaged thick-walled cylinder (자긴가공된 두꺼운 실린더의 피로균열 전파수명평가)

  • Lee, Song-In;Kim, Jin-Yong;Jeong, Se-Hui;Go, Seung-Gi
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.22 no.2
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    • pp.321-329
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    • 1998
  • To ensure the structural integrity of the autofrettaged thick-walled cylinder subjected to cyclic internal pressure loading, the fatigue crack propagation life of the cylinder was evaluated. Stress intensity factors of the external cracked cylinder due to internal pressure and autofrettage loadings were calculated using the finite element method. The fatigue crack propagation lives of the cylinder based on the fracture mechanics concepts were predicted and compared to the experimental fatigue lives evaluated from the C-shaped simulation specimens. There were good correlations between the predicted and experimental fatigue lives within a factor of 3 for the single and double grooved C-shaped simulation specimens. Predicted fatigue crack propagation lives of the double grooved cylinders were about 1.5-5 times longer than those of the single grooved cylinders depending on the levels of autofrettage.