• 한국압력기기공학회 논문집
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• 제11권2호
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• pp.68-74
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• 2015

Time domain response analysis for vibro-impact nonlinear behavior of multi-span tube with loose supports was performed using commercial FEA code and user subroutine. Support geometry of multi-span tube with a finite gap is realistically modeled by analytical rigid surface. Model of hydrodynamic force is based on the Qusai-steady model which accounts for the inclined angle of relative flow velocity and time delay between flow force and resulting tube motion. During tube vibration from flow loading, impact and friction at the support location is simulated using commercial FEA code with master slave contact algorithm. Analysis results has reasonable agreement with those of references and test experience. Plan of further refinement of analysis model and future test verification is briefly introduced.

• Geomechanics and Engineering
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• 제18권5호
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• pp.493-502
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• 2019

Internal stability is an important safety issue for levees, embankments, and other earthen structures. Since a large part of the world's population lives near oceans, lakes and rivers, floods resulting from breaching of dams can lead to devastating disasters with tremendous loss of life and property, especially in densely populated areas. There are some main factors that affect the internal stability of dams, levees and other earthen structures, such as the erodibility of the soil, the water velocity inside the soil mass and the geometry of the earthen structure, etc. Thus, the mechanism of internal erosion and stability of soils is very complicated and it is vital to investigate the assessment methods of internal stability of soils in embankment dams and their foundations. This paper presents an improved support vector machine (SVM) model to predict the internal stability of soils. The grid search algorithm (GSA) is employed to find the optimal parameters of SVM firstly, and then the cross - validation (CV) method is employed to estimate the classification accuracy of the GSA-SVM model. Two examples of internal stability of soils are presented to validate the predictive capability of the proposed GSA-SVM model. In addition to verify the effectiveness of the proposed GSA-SVM model, the predictions from the proposed GSA-SVM model were compared with those from the traditional back propagation neural network (BPNN) model. The results showed that the proposed GSA-SVM model is a feasible and efficient tool for assessing the internal stability of soils with high accuracy.

• 한국압력기기공학회 논문집
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• 제19권2호
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• pp.146-154
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• 2023

In nuclear power plants, ultrasonic test for pipe wall thickness measurement is used during periodic inspections to prevent pipe rupture due to pipe wall thinning. However, when measuring pipe wall thickness using ultrasonic test, a significant amount of measurement error occurs due to the on-site conditions of the nuclear power plant. If the maximum pipe wall thinning rate is decided by the measured pipe wall thickness containing a significant error, the pipe wall thinning rate data have significant uncertainty and systematic overestimation. This study proposes preprocessing of pipe wall thinning measurement data using support vector machine regression algorithm. By using support vector machine, pipe wall thinning measurement data can be smoothened and accordingly uncertainty and systematic overestimation of the estimated pipe wall thinning rate data can be reduced.

• 플랜트 저널
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• 제15권4호
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• pp.43-51
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• 2019

배관계를 지지하는 목적으로 자주 사용되는 일체형 용접부착물은 응력집중효과로 인한 국부응력을 유발시켜 종종배관의 파손을 일으키기 때문에 사용에 각별한 주의를 요구하고 있다. 국내 원자력 발전소 배관 곡관부에 부착된 원형관의 국부응력 평가는 EPRI TR-107453에 따라 평가하고 있지만, 이의 적용에는 배관과 부착물의 크기에 관한 특정 매개변수 범위의 제한사항이 있다. 이 논문에서는 유한요소해석을 활용하여 모델들의 치수를 기반으로 한 매개변수 연구를 수행하여 기술적 근거를 확립하고 연구 결과에 대한 회귀분석을 통해 확장된 매개변수 범위를 갖는 곡관부에 부착된 원형관 이음부의 이차응력지수 산출 상관관계식을 도출하였다. 본 연구를 통해 개발된 새로운 상관관계식에 대한 검증을 통해 현재 평가기준의 대체 기준으로써 적용할 것을 제안한다.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1999년도 추계학술발표회요약집
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• pp.349.2-349
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• 1999

• 한국음향학회지
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• 제41권6호
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• pp.680-690
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• 2022

일반적으로 배관에서 발생하는 진동은 배관을 파손시키는 문제를 넘어 배관 파손으로 유발되는 다른 위험한 문제의 원인이 된다. 배관 진동의 원인 분석과 이를 줄이기 위한 수많은 연구들이 존재하는데, 그 중 마찰 지지대를 이용한 배관 진동저감에 대한 연구가 소수 진행되고 있다. 하지만 마찰 지지대에 관한 연구들은 마찰 지지대 성능 예측과 평가에만 집중하였고, 지지대 설치 위치에 따라 달라지는 마찰 지지대의 효과는 고려하지 않았다. 따라서, 본 연구에서는 마찰 지지대의 설치 위치에 따른 배관 진동 저감 효과를 입증하고 전체 시스템의 진동을 줄이기 위한 마찰 지지대 위치 선정 방법을 제시한다. 설계단계에서 최적화 방법을 효과적으로 적용하기 위해 선형 해석으로만 마찰 지지대의 최적 위치를 예측하고, 설계된 마찰 지지대를 시간 영역 해석을 통해 방법론의 타당성을 입증하였다. 또한, 배관 시스템에서 마찰 지지대의 우수한 진동 저감 효과를 정량적으로 해석하여, 지지대 설치 위치를 예측하는 방법의 효용성을 증명하였다.

• 대한조선학회논문집
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• 제48권4호
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• pp.325-329
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• 2011

Floating, production, storage and offloading (FPSO) is a production facility that refines and saves the drilled crude oil from a drilling facility in the ocean. The flare system in the FPSO is a major part of the pressure relieving system for hydrocarbon processing plants. The flare system consists of a number of pipes and complicated connection systems. Decision of pipe support types is important since the load on the support and the stress in the pipe are influenced by the pipe support type. In this study, we optimally determined the pipe support types that minimized the support cost while satisfying the design constraints on maximum support load, maximum nozzle load and maximum pipe stress ratio. Performance indices included in the design constraints for a specified design were evaluated by pipe structural analysis using CAESAR II. Since pipe support types were all discrete design variables, an evolutionary algorithm (EA) was used as an optimizer. We successfully obtained the optimal solution that reduced the support cost by 27.2% compared to the initial support cost while all the design requirements were satisfied.

• 한국압력기기공학회 논문집
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• 제6권1호
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• pp.83-88
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• 2010

Domestic nuclear steam generators with Alloy 600 HTMA tubes have experienced axial cracking at eggcrate tube support plates(TSPs). The axial stress corrosion cracks were observed at the crevice between outside of tubes and eggcrate TSPs. The root cause of axial cracking was investigated by thermal hydraulic analysis and sludge distribution diagnosis. It is suggested that deposition of sludge at eggcrate TSPs could increase the outside surface temperature of tube and promote the enrichment of impurities at crevice, and thus accelerate cracking. Additionally strategy for reducing the sludge ingress to steam generators is discussed.

• Nuclear Engineering and Technology
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• 제28권4호
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• pp.390-396
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• 1996

Piping Systems are usually designed for thermal expansion loads based on uniform temperatures at each cross section. However, in lines with low flow rates such as surge lines and spray lines, large transverse temperature gradients have been observed, resulting in too types of additional thermal stresses : (1) local thermal gradient stresses which are independent of routing and supports and (2) gross bending stresses due to induced pipe curvature which are routing and support system dependent. This paper presents a simplified method for analyzing a PER surge line for stratified flow.

• 동력기계공학회지
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• 제5권1호
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• pp.57-63
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• 2001

In the present study, an interactive mode of the computing system has been developed for the hydraulic analysis of the circulating waters in the industrial pipings. The system consists of three separated modules, which are linked together with common graphical user interfaces. Application to the design of the cooling sea-water system for the ships was demonstrated to be very reliable and practical in support of design activities.