• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.2
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• pp.952-962
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• 2015

In this study, multilayered rings with a large outer diameter have been developed using a hot ring rolling process. The ring rolling process has been analyzed by rigid plastic finite element analyses (FEA) using the AFDEX2D and AFDEX3D/HEXA/RING simulators, where the finite element meshes received severe plastic deformation are remeshed into a fine mesh-size using a dual-mesh system. According to the simulated results, the design variables of the multilayered rings were determined and real tests were conducted to check the validity of the simulation results. By adopting the hot ring rolling process, the input weight of raw materials was reduced by 40% against the conventional hot forging process and that the recovery rate was increased by 24%. The measurement of the averaged roundness was satisfied within 0.5 mm for both the inner and outer diameters. Moreover, the hot ring rolling processes yielded 1.49 Cpk for the outer-diameter and 0.84 Cpk 0.84 for the inner-diameter.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.1
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• pp.65-70
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• 2014

This paper introduces a preform design method for a ring rolling process with an outer step. Underfilling is one of the general defects of the profile ring rolling process. It occurs when the deformation amount is small or step depth of the profiled region is large. To prevent underfilling, increasing the deformation amount or using a preform of size similar to that of the final product are required. Furthermore, the filling limit equation is suggested based on the shape factor and deformation ratio for preventing defects in the products. The filling limit equation has been derived through finite element analyses and production tests for four different cases. For verifying the suggested method, realsized profile rolling tests were performed, and test results were compared with the predictions of the equation.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.8
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• pp.22-27
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• 2020

Ring rolling is a type of forging for manufacturing large-diameter rings. Products manufactured by ring rolling are useful in the aerospace industry because of their excellent mechanical properties and high dimensional accuracy. The major components of the ring rolling process are a mandrel and main roll that shape the inside and outside of the ring, an axial roll that shapes the top and bottom of the ring, and a side rolls to position the ring. In this study, a simulation of ring rolling using finite element method (FEM) was performed. DEFORM, a commercial machining analysis program, was used. Based on the simulations, the mandrel feed force required for machining and the drive torque of the main roll were predicted. It was also possible to identify the metal flow caused by machining.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.7
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• pp.721-727
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• 2015

The mechanical components for wind turbines are mainly manufactured using open-die forging. This research introduces an advanced forging method to produce the door frame of the tubular wind turbine tower. The advantages of this new forging method are an increase in the raw material utilization ratio and a reduction in energy cost. In the conventional method, the door frame is hot forged with a hydraulic press and amounts of material are machined out because of the shape difference between the forged and final machine products. The proposed forging method is composed of hot forging and ring rolling processes to increase the material utilization ratio. The effectiveness of this new forging method is deeply related to the ring rolled blank dimension before the final forging. To get the optimal ring rolled blank, forged shape prediction using the finite element analysis method was applied. The forged dimensions produced by the new forging method were verified through the first article production.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.398-398
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• 2022

최근 수돗물 공급과정에 있어 적수, 유충 발생 등 지역 단위의 수질문제로 국민의 직간접적인 피해가 발생된 바 있다. 수질문제 발생 시, 소셜네트워크서비스(SNS)에 게시되는 피해 관련 의견은 시공간적으로 빠르게 확산되며, 궁극적으로는 물공급과정 전체의 부정적 인식증가와 신뢰도 저하를 초래한다. 따라서, 물공급시스템에서의 수질사고 발생을 빠르게 인지하는 다양한 방법론의 적용을 통한 피해 최소화를 위한 노력이 반드시 필요하다. 일반적으로 수질사고는 다양한 항목의 실시간 계측기에서 획득되는 시계열자료의 변화양상을 통해 판단할 수 있으나, 이와 같은 방법론의 효율적 적용을 위해서는 선진계측인프라의 도입이 선행되어야 한다. 본 연구에서는 국내의 발달된 정보통신기술환경을 활용하여, 물공급네트워크 내 수질사고인지를 위한 SNS 별 웹크롤링 방법론을 제안하고, 적용결과를 분석하였다. 방법론의 구현에 앞서, 각종 SNS 별(트위터, 인스타그램, 블로그, 네이버 카페 등) 프로그래밍을 통한 웹크롤링 가능여부, 정보획득 기간 등을 확인하였으며, 과거 유사 수질사고 발생 시 영향력과 관련 게시글이 크게 나타난 네이버 카페와 트위터를 중심으로 웹 크롤링 절차를 제시하였다. 네이버 카페의 경우 대상급수구역 내의 시민들이 다수 참여하는 카페를 목록화하고, 지자체명과 핵심 키워드(수돗물, 유충, 적수) 조합을 활용한 웹크롤링을 수행하여, 관련 게시물 건수와 의미를 실시간으로 분석하는 절차를 마련하였다. 개발된 SNS 별 웹크롤링 방법론에 따라 과거 수질사고가 발생된 바 있는 2개 이상의 지자체에 대한 분석을 실시하였으며, SNS 별 결과에 있어 차이점을 확인하여 제시하였다. 향후 제안된 방법을 적용하여 시공간적 수질사고 정보의 전파 및 확산양상을 추가적으로 분석할수 있을 것으로 기대된다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2009.10a
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• pp.271-272
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• 2009

• Proceedings of the Korean Society of Computer Information Conference
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• 2018.07a
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• pp.175-176
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• 2018

기존 신문이나 티브이가 아닌 온라인과 모바일로 뉴스를 보는 사람이 더 많아지면서, 포털 사이트 뉴스난에 다른 언론사의 기사보다 더 많이 노출되기 위한 경쟁의 심화로 뉴스 어뷰징은 심각한 사회 문제로까지 대두되었다. 본 논문은 온라인상에서 생성, 유통되는 많은 뉴스 중에서 이용자의 시간을 낭비하고 양질의 정보를 찾기 힘들게 하는 뉴스 어뷰징을 판단하는 모델을 제안한다. 제안된 모델은 크롤링 기술을 사용하여 뉴스의 제목과 내용을 가져온 후 인공지능 기술을 이용한 유사도 검사로 기사의 어뷰징 여부를 판단하여 양질의 뉴스 정보를 사용자에게 제공될 수 있다.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.2
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• pp.173-181
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• 2014

In this paper, the algorithm that can automatically segment the lung, the airway and the pulmonary vessels in a chest CT was proposed. The proposed method is progressed in three steps. In the first step, the lung and the airway are segmented by the region growing law through the optimal threshold and three-dimensional labeling. In the second, from the start point to the first carina of the airway is segmented by the deduction operation, and the next airway of the bifurcations are segmented by applying a variable threshold technique. In the third step, the left/right lungs are divided by the restoration process for the lung, and the outside of lungs for abnormal is checked by applying the advanced rolling ball algorithm, and if abnormal is found, that part is removed, and it is restored to the normal lungs by connecting the outside of the lung in the form of second-order polynomial. Finally, pulmonary vessels are segmented by applying the three-dimensional connected component labeling method and three-dimensional region growing method. As the results of simulation, it could be confirmed that the pulmonary vascular is accurately divided without loss of tissue around lung.

• Transactions of Materials Processing
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• v.25 no.1
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• pp.5-11
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• 2016

The control of the roll velocities is essential in maintaining stability during ring rolling, but such control is difficult. The determination of the best roll velocities can be helped with the use of FE simulations and processing maps, which give the useful information such as power dissipation and flow instability for hot metal forming processes. In the current study, the workability of 7050 aluminum alloy is evaluated by using processing map. With the developed information, the stability of the ring rolling condition, called the Constant Growth Velocity Condition (CGVC), is evaluated.

• Transactions of Materials Processing
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• v.27 no.5
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• pp.289-295
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• 2018

The profile ring rolling process can realize various ring shapes unlike conventional rectangular cross-sectional ring products. In this paper, the defective groove in the bottom surface of L-shaped ring products was analyzed. Grooves are generated by non-uniform external forces due to profile main roll and initial blank shape. Process parameters such as the motion of dies and working temperature were determined. Mechanism of groove formation was analyzed by FE simulation on the basis of local external forces acting on the blank. Analysis results were similar to the groove actually occurring in the production line. Based on results of the analysis, two solutions were proposed for the groove. The position of the base plate supporting the blank was adjusted and edge length of the main roll was extended to suppress growth of grooves. It has been verified that groove was improved by applying two proposed methods in the shop-floor.