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박치용,김진원,김양석,Park, Chi-Yong,Kim, Jin-Weon,Kim, Yang-Seok 한국유체기계학회 2000 한국유체기계학회 논문집 Vol.3 No.4
This paper provides integrity evaluation and root cause analysis for defects observed at volute tongue, or cutwater, of the operating centrifugal pump in power plant. The cause of the cracks are analyzed and reviewed from the viewpoint of the operation and maintenance of the pumps, and the sample obtained from the cracked volute tongue of the pump are examined. At first, in-situ hardness test and microstructure examination were performed to understand the cause of cracking at volute tongue. The evaluation of structural integrity and the possibility of the crack propagation is also evaluated. Cracks were typical intergranular cracking and propagated along with prior austenite grain boundary. At easing volute tongue, the hardness was higher than ASTM requirement and a large amount of intergranular Cr carbide was precipitated. These were due to high C content in material. P content was also higher than ASTM requirement. Therefore, Cr carbide precipitation and P segregation at grain boundary, caused by higher C and P content in material, resulted in intergranular cracking of casing volute tongue. This procedure for integrity evaluation and root cause analysis is used to guide, and support the pump designer and manufacturer's material selection and process design to avoid a costly, unplanned outage of plant.
박치용(Chi-yong Park),김대웅(Dae-woong Kim),김양석(Yang-seok Kim),김형균(Hyoung-kyun Kim),이병오(Byoung-oh Lee) 대한기계학회 2015 대한기계학회 춘추학술대회 Vol.2015 No.11
On-line monitoring system is utilized for improving the plant operation reliability in the plant fleet such as fossil power plants, aircraft industry and nuclear power plants. A development project of online monitoring system has been recently carried out for updating component and system’s reliability in domestic nuclear power plant. In this paper, the development status of a centralized online monitoring system, its named CMD(Centralized Monitoring and Diagnosis) center, was introduced shortly. Lesson learned from development and application process also was shown. We would like to communicate with researchers and engineers concerning to online monitoring studies through the lessons learned from our development and application study. The stakeholder in online monitoring research would go forward to the advanced engineering goal when all parts may communicate with each others based on the appropriate role of industrial-educational relationship, the mutual comprehension of application barrier and the co-ownership for technical basis. Through all members such as researchers, application engineers and operator for online monitoring system have to get mutual comprehension and active communication, the developed and applied techniques of online monitoring would be improved and advanced to the high level with reliability of components and systems in nuclear power plants.
직선 Slot 용접의 유한요소해석 및 용접잔류응력 분포특성
박치용(Chi-Yong Park),김만원(Maan-Won Kim),이경수(Kyoung-Soo Lee),송기오(Ki-Oh Song) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.5
본 연구에서는 316L 스테인리스강 테스트 시편으로 직선 슬롯(slot) 용집을 수행하고 X-선 회절법을 이용하여 용접 잔류응력을 측정하였다. 또한 3 차원 유한요소해석을 통하여 슬롯용접을 모사하고 시편의 용접잔류응력 분포를 구하였다. 슬롯용접은 용접잔류응력 특성을 고찰하는데 있어 맞대기 용접에 비하여 고려할 변수가 적으며, 용접 시작부터 종료까지 용접잔류응력 분포 특성을 쉽게 파악할 수 있는 장점이 있다. 테스트 시편의 표면에서 용접잔류응력을 용접 시작부와 중간부분, 종료부의 세 위치에서 측정값과 해석값을 비교하였고 용접잔류응력 분포특성을 고찰하였다. 유한요소해석 결과로부터 시편 내부의 용접잔류응력 분포특성을 살펴보았다. In this study a straight slot welding was performed with a 316L stainless steel test block and a numerical welding simulation was conducted with the finite element analysis for the slot welding process. The residual stress data were measured at equally spaced points along the lines parallel and perpendicular to welding direction on the top surface of the test plate. The X-ray diffraction method after electrolytic polishing was used for stress measurement. The calculated weld residual stresses were compared with measured data and they displayed good agreement. The weld residual stress distribution inside the plate was extracted from the finite element analysis results and its characteristics were discussed in detail.
직선 Slot 용접의 유한요소해석 및 용접잔류응력 분포특성
박치용(Chi-Yong Park),이경수(Kyoung-Soo Lee),김만원(Maan-Won Kim),송기오(Ki-Oh Song) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.9
본 연구에서는 316L 스테인리스강 테스트 시편으로 직선 슬롯(slot) 용접을 수행하고 X-선 회절법을 이용하여 용접 잔류응력을 측정하였다. 또한 3차원 유한요소해석을 통하여 슬롯용접을 모사하고 시편의 용접잔류응력 분포를 구하였다. 슬롯용접은 용접잔류응력 특성을 고찰하는데 있어 맞대기 용접에 비하여 고려할 변수가 적으며, 용접 시작부터 종료까지 용접잔류응력 분포 특성을 쉽게 파악할 수 있는 장점이 있다. 테스트 시편의 표면에서 용접잔류응력을 용접 시작부와 중간부분, 종료부의 세 위치에서 측정값과 해석값을 비교하였고 용접잔류응력 분포특성을 고찰하였다. 유한요소해석 결과로부터 시편 내부의 용접잔류응력 분포특성을 살펴보았다. In this study, straight slot welding was carried out using a 316L stainless steel test block, and numerical simulation of the slot weld process was performed using finite element analysis. Data on the residual stress were obtained at equally spaced points on the top surface of the test block along directions parallel and perpendicular to the welding direction. After electrolytic polishing of the top surface of the block, the residual stress was measured by the X-ray diffraction method. The calculated weld residual stresses were compared with the measured data, and they were in good agreement with the data. The weld residual stress distribution inside the plate was determined from the results of finite element analysis, and the characteristics of the distribution were discussed in detail in this paper.
볼트 체결길이 미흡에 따른 배관 플랜지의 구조 신뢰성 평가
박치용(Chi-Yong Park),신인환(In-Whan Shin),김만원(Maan-Won Kim) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.11
The flange connecting method is widely used in the industrial field because of using the advantages of simple installation and maintenance. The connection between flanges is fixed with bolts. If the length of the bolts in the connection part is not sufficient, a bolt has to be replaced with a new bolt. When the pipe is operating in fluid system, it may be necessary to evaluate the soundness of the flange connection for the insufficient bolt length. And then, based on the evaluation results, a faulted bolt has to be selected one of them such as immediate replacement, replacement after one cycle or continue to use. In this paper, the structural reliability for pipe flange fastening was evaluated when the bolt fastening length was in sufficient. The structural reliability was checked whether the maximum applied stress on the bolt thread surface was within the allowable stress range of the ASME code.