• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.233-235
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• 2007

Finite element analysis was conducted for cold roller leveler to verify numerical model of roller leveler developed by POSTECH. On-line model of roller leveler was developed to predict rapid and precise roll intermesh of roller leveler in thick plate mill. The cold roller leveler in thick plate mill was analyzed using MARC & MENTAT and the results are compared with the results of numerical model of roller leveler calculated by POSTECH.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 제7회 압연 심포지엄
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• pp.93-96
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• 2009

The high grade thick plate is in great demand in the ship building industry and the construction industry. The main problems to produce the high grade plate are residual stress and flatness of plate. In the previous research, Finite Element Analysis(FEA) was conducted for cold roller leveler to understand the behaviors of cold roller leveler under different conditions of thickness, intermesh, and yield stress. In this study, a numerical model of roller leveler is developed and the calculated results of this model are compared with the FEA results to show the validity of the numerical model. The optimal leveling conditions to improve flatness of plate are suggested using this numerical model.

• 소성∙가공
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• 제24권4호
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• pp.241-247
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• 2015

In order to prevent shape defects such as fluting and stretcher strains during press forming of aged low carbon steel sheets, roller leveling conditions for reducing yield point elongation were studied. Yield point elongations of leveled sheets were determined as a function of leveling, which is defined as the plastic fraction or the ratio of plastically deformed part in sheet thickness section to the whole thickness of the sheet. By adjusting this plastic fraction during leveling to more than 78%, yield point elongation in the leveled sheets was reduced so no fluting occurred during subsequent tangential bending. Stretcher strains can be avoided by leveling the sheet to an 84% plastic fraction condition.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 춘계학술대회논문집
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• pp.319-322
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• 2003

For the analysis of leveling process by the 3-dimensional elastic-plastic finite element method, a finite element analysis program modeling large deformation of shell has been developed. This program fur analyzing large deformation of sheet during leveling includes spring-back analysis as well as efficient contact treatment between sheet and rolls of leveler. This is verified by the simple leveling experiment with 5 rolls at laboratory. Besides the leveling examples, problems within the category of large strain and rotation, such as 3-dimensional roll-up and gutter occurrence at continuous bending-unbending process are also tested for verification of the program. The residual curvatures of strip predicted by finite element analysis are within 20% error range of the experiment. The formation and direction of anticlastic curvature or gutter during bending-unbending under tension is predicted and this agrees with the experimental results.

• 소성∙가공
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• 제15권4호
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• pp.311-318
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• 2006

One of the most important quality problems in flat plate leveled from hot rolled coils in cut-to-Iength lines is bowing and cambering when they are cut in small width parts. It is verified analytically and experimentally that residual stress remained in plate is th ε source of the problem. In order to produce low residual stress flat plate from hot rolled coils, the proper conditions of leveling are studied and two things are implemented. One is proper plastic deformation area ratio to reduce residual stress within customer requirement by applying suitable plastic deformation and maintain leveling load within structural strength limit of leveler. The other is maintaining uniform plastic deformation along the width of the plate during leveling. Customer requirement for residual stress is met by applying above 70% of plastic deformation area ratio and uniform deformation along width of coil by adjusting back up rolls according to deformation analysis of work roll and back up roll assembly and leveling tests.