• Title/Summary/Keyword: Internal thinning defect

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Burst Test and Finite Element Analysis for Failure Pressure Evaluation of Nuclear Power Plant Pipes (원전 배관 손상압력 평가를 위한 파열시험 및 유한요소해석)

  • Yoon, Min Soo;Kim, Sung Hwan;Kim, Taesoon
    • Journal of the Korean Society of Safety
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    • v.30 no.1
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    • pp.144-149
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    • 2015
  • This study aims to quantitatively evaluate failure pressure of wall-thinned elbow under combined load along with internal pressure, by conducting real-scale burst test and finite element analysis together. For quantitative evaluation, failure pressure data was extracted from the real-scale burst test first, and then finite element analysis was carried out to compare with the test result. For the test, the wall-thinning defect of the extrados or intrados inside the center of 90-degree elbow was considered and the loading modes to open or close the specimen maintaining a certain load or displacement were applied. Internal pressure was applied until failure occurred. As a result, when the bending load was applied under the load control condition, the intrados of the defect was more affected by failure pressure than the extrados, and the opening mode was more vulnerable to failure pressure than the closing mode. When the bending load was applied under the displacement control, it was hardly affected by failure pressure though it was slightly different from the defect position. The result of the finite element analysis showed a similar aspect with the test. Moreover, when major factors such as material properties and pipeline thickness were calibrated to accurate values, the analytical results was more similar to the test results.

Structural Integrity Evaluation of SG Tube with Surface Wear-type Defects (표면 마모결함을 고려한 증기발생기 세관의 구조건전성 평가)

  • Kim, Jong-Min;Huh, Nam-Su;Chang, Yoon-Suk;Hwang, Seong-Sik;Kim, Joung-Soo;Kim, Young-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.12 s.255
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    • pp.1618-1625
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    • 2006
  • During the last two decades, several guidelines have been developed and used for assessing the integrity of a defective steam generator (SG) tube that is generally caused by stress corrosion cracking or wall-thinning phenomenon. However, as some of SG tubes are also failed due to fretting and so on, alternative failure estimation schemes are required for relevant defects. In this paper, parametric three-dimensional finite element (FE) analyses are carried out under internal pressure condition to simulate the failure behavior of SG tubes with different defect configurations; elliptical wear, tapered and flat wear type defects. Maximum pressures based on material strengths are obtained from more than a hundred FE results to predict the failure of SG tube. After investigating the effect of key parameters such as defect depth, defect length and wrap angle, simplified failure estimation equations are proposed in relation to the equivalent stress at the deepest point in wear region. Comparison of failure pressures predicted by the proposed estimation scheme with corresponding burst test data showed a good agreement.

Measurement of Inner Defects and out of Plane Deformation of Pressure Vessel in Piping of Circulation System Using Shearography (전단간섭법을 이용한 배관 순환 시스템에서의 압력용기 내부결함 및 면외변형 측정)

  • Kang, Chan-Geun;Kim, Hyun-Ho;Jung, Hyun-Il;Choi, Tae-Ho;Jung, Hyun-Chul;Kim, Kyeong-Suk
    • Journal of the Korean Society for Nondestructive Testing
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    • v.34 no.5
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    • pp.349-355
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    • 2014
  • Wall thinning defects can occur in the pressure vessels used in a variety of industries. Such defects are related to the flow velocity. Considering the fact that such vessels constitute up to 70 or 80% of the plant structures in a power plant, it is important to measure internal defects as part of a safety evaluation. In this study, optical measurement were applied in a non-destructive evaluation using shearography to ensure the safety and improve the reliability of a power plant through the non-contact, non-destructive evaluation of pressure vessels. In order to verify whether the pressure vessels contained faults, experimental and analytical investigation were conducted to measure any internal defects and out-of-plane deformation from inner temperature changes and pressure changes in the piping of the circulation system. The most important factors in this research were the thickness, width, and length of a defect. An increase in these could confirm an increase in the deformation. Thus, internal defects in a pressure vessel were measured using shearography, which made it possible to ensure the reliability and integrity of the pipe.