경량모델 기반 용접변형 해석을 위한 요소망 생성 방법

박중구(Jung Goo Park),최두진(Doo Jin Choi),권기연(Ki Youn Kwon) 대한기계학회 2022 大韓機械學會論文集A Vol.46 No.5

선박 및 플랜트 건조 과정에서 경량모델은 설계, 물류 및 생산을 비롯하여 모든 공정에서 널리 활용되고 있다. 경량모델은 3차원 형상을 가시화하는 용도로 이용되며, 주로 삼각형 요소로 구성되어 있다. 따라서 가시화 성능을 높이기 위해 삼각형 개수를 줄이고, 파일크기를 줄이는 것이 경량모델 관점에서 중요하다. 선박 및 플랜트 건조 과정에서 용접 공정은 시간과 비용이 많이 소요되는 공정이다. 또한, 용접은 수축 및 굽힘 변형을 유발하여 많은 치수품질 문제를 일으킨다. 용접변형으로 인한 치수품질 문제를 방지하기 위해서 유한요소해석법이 주로 사용되고 있다. 본 연구에서는 경량모델 기반으로 용접변형 해석이 가능한 요소망 생성법을 제안한다. 경량모델은 가시화 용도여서 형상에 대한 위상정보를 포함하고 있지 않다. 삼각형 요소로부터 윤곽선을 추출한 후에 이 윤곽선이 다른 면과 인접해 있으면 용접선이 될 수 있다. 용접선을 내부 루프로 포함하는 트림 곡면을 구성한 후에 영역분할법을 이용해서 사각형 요소를 생성한다. 몇 가지 적용 사례를 통해 제안된 알고리즘을 검증했다. In ships and offshore plants, lightweight models are widely used for all processes, including design, procurement, construction, and operation. These models are mainly composed of triangular elements, thus minimizing the file size and increasing the visibility. The welding process is the most time-consuming and expensive process in the ship and plant construction. During this process, welding deformation causes dimensional quality problems. A finite element analysis (FEA) is widely used to prevent these problems. In this paper, we propose a mesh generation method to estimate welding deformation based on a lightweight model. The lightweight model has no information about the welding line because this model is only used for visualization purposes. Boundary curves are restored from the triangle elements. If a boundary curve lies on another face, it is classified as a welding line. Then, a trimmed polygon surface is created including welding lines, and a quadrilateral mesh is generated using the domain decomposition method. This proposed method was tested on several models to demonstrate the feasibility.

선박 건조를 위한 샤프트와 프로펠러 가상 조립 시뮬레이션 방법

박중구(Jung Goo Park),최두진(Doo Jin Choi),원석희(Seok Hee Won),윤여운(Yeo Un Yoon),권기연(Ki-Youn Kwon) (사)한국CDE학회 2021 한국CDE학회 논문집 Vol.26 No.4

The shaft transmits the power of the engine to the propeller in ships, and dimensional accuracy for this is very important. In order to assemble the shaft and propeller, assembling, confirming the contact part, and manual machining are repeatedly performed. In this study, a virtual simulation method for shaft and propeller assembly is proposed. A precise 3D scanner for short-distance measurement is used to measure the shape, and this data is used to determine the contact area for manual machining. Shafts and propellers are precision-machined products and should be able to be discriminated down to tens of micrometers. Therefore, the measured shape consists of a very large number of triangular elements, and is converted into a simple form to reduce the simulation time. The ICP (iterative closest point) method is applied to find the position where the shaft can be fastened to the propeller as much as possible. Weights are given to find the optimal location where penetration does not occur. This proposed method has been tested on several models to demonstrate the feasibility.

후판 필렛 용접 및 선상 가열 시 강재 구속에 따른 변형에 관한 연구

박동희(Dong-Hee Park),박중구(Jung-Goo Park),박창우(Chang-Woo Park),양진혁(Jin-Hyuk Yang),박준석(Jun-Seok Park),노지선(Ji-Sun Roh),이명수(Myung-Su Yi),김도균(Do-Kyun Kim),이제명(Jae-Myung Lee) 대한용접·접합학회 2023 대한용접·접합학회지 Vol.41 No.6

고유변형률 기반 LNG 연료 추진 컨테이너선의 축계부 선체 열변형 예측 정확도 향상

박준석(Jun-Seok Park),박중구(Jung-Goo Park),서정관(Jung-Kwan Seo) 대한용접·접합학회 2024 대한용접·접합학회지 Vol.42 No.1

A ship’s hull, made of steel, is welded together from individual plates. Welding can cause deformation, a common defect. Predicting this deformation is crucial for shipyard design and management. Numerical analysis using finite elements is widely used for this prediction, with extensive research on the inherent strain-based analysis method. However, determining inherent strain requires synchronizing all strain items over time and considering uncertainties like the welder’s posture and skill. This study derives an integrated inherent strain over the welding process, considering the welding position and cooling method. The derived strain has been implemented and reviewed through numerical analysis of the LNG-powered container ship’s hull assembly process. This integrated inherent strain can serve as a basis for further research on welded structures, materials, welding parameters, and inherent strain-based analysis methods.

FLNG 탑사이드 베어링 노드 후판 맞대기 용접 및 선상 가열 시 강재 구속에 따른 변형에 관한 연구

박동희(Dong-Hee Park),박중구(Jung-Goo Park),이제명(Jae-Myung Lee) 대한용접·접합학회 2024 대한용접·접합학회지 Vol.42 No.1

Products manufactured in shipyards are predominantly steel structures, primarily fabricated through welding. There are various welding methods, all of which commonly use very high heat. Therefore, during the fabrication of steel structures, thermal deformation caused by welding occurs, resulting in dimensional deviations from the initial design. Methods to ensure dimensional accuracy include optimizing the welding sequence, predicting thermal deformation before welding and applying reverse-setting, and suppressing thermal deformation through constraints. However, the most commonly used method in the field is heat straightening. This study proposes a method to control thermal deformation caused by welding by using steel constraints during welding and line heating. Analytical verification confirmed both the effect of heat straightening and the variance in effects when steel constraints were applied. As a result, it was confirmed that line heating is effective in correcting thermal deformation, and steel constraints can maximize the effect of line heating.

해양플랜트 의장품 조달관리를 위한 배관 공정 리드타임 예측 모델에 관한 연구

함동균(Dong Kyun Ham),백명기(Myung Gi Back),박중구(Jung Goo Park),우종훈(Jong Hun Woo) 대한조선학회 2016 大韓造船學會 論文集 Vol.53 No.1

용접배관 절단 및 원주용접을 고려한 잔류응력 재분포 특성 연구

노지선(Ji-Sun Roh),이명수(Myung-Su Yi),박중구(Jung-Goo Park),김명현(Myung-Hyun Kim) 대한용접·접합학회 2024 대한용접·접합학회지 Vol.42 No.1

Seam pipes are easier to manufacture and cheaper than seamless pipes, and are widely used in the manufacture of pipe spools for marine plant facilities. The manufacturing and assembly of seam pipes involve welding and cutting. The localized heating and cooling that occur during these processes may change the existing residual stress and cause deformation. Uncontrolled deformation can accumulate as assembly errors at the next step, potentially delaying the entire process and causing economic losses. Therefore, characteristics of residual stress redistribution caused by cutting and girth welding of seam pipes need to be studied further. In this study, we performed thermo-mechanical analysis of the manufacturing, cutting, and girth welding processes of seam pipes using the commercial finite element analysis (FEA) software MSC Marc and analyzed the characteristics of residual stress. Furthermore, we measured the residual stress in each process using the hole drilling method, analyzed the characteristics of redistributed residual stress, and ensured reliability. Based on the results of FEA and measured residual stress redistribution, we can provide a basis for reasonable mitigation when performing structural integrity evaluation if there is a defect in the weld of the pipe.

변동성 기반 대기행렬 이론을 이용한 조선 생산계획 및 조달계획 데이터 분석

곽동훈(Dong Hoon Kwak),유상현(Sang Hyeon Yu),우종훈(Jong Hun Woo),박중구(Jung Goo Park) 대한산업공학회 2020 대한산업공학회지 Vol.46 No.6

In order to establish an accurate production plan, the net working time must be determined in consideration of unit working time and production volume, then the production time must be determined in consideration of the appropriate allowance time with the net working time. However, since the unit working time of shipbuilding is inaccurate and there are many difficulties in calculating the production volume, most shipyards are following the top-down procedure based on the past ship’s production records. In addition, shipyards have very large variability affecting production time, such as delay and waiting, because human factors dominate. Nevertheless, there has been little scientific analysis of this variability. Variability is a kind of statistical variable. When applied to a production system in combination with the queuing theory, it is possible to analyze the production process through scientific analysis and draw productivity improvement because it is possible to analyze the variability considering production time and process capability. Researches on variability have been applied to mass production industries such as automobile production. The target of most researches of variability in the mass production industry is to reduce the variability of production time to secure higher productivity with the given production resources. However, in the case of the shipbuilding industry, the variability in production time is very high and difficult to control compared to the mass production industry. So, queuing analysis with high variability never has been studied in shipbuilding. In this study, the quantitative variability level of the shipbuilding of Korea is investigated through the queuing analysis with variability with respect to the schedule and procurement plan of the shipyard, and the scientific analysis is conducted for the analysis of the relationship between the productivity and the composition of shipyard production resources.