• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.4
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• pp.355-360
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• 2012

Cold drawn(CD) bars feature superb surface roughness, dimensional precision, and straightness. They are used in the manufacture of automotive parts and home electrical appliances. Two cross-roll straighteners have been used to manufacture CD bars for these industries. This study investigated the variation of the gap size between the two cross-rolls. It was found that changes in the gap size have a large influence on the residual stress and plastic deformation. Finite element method(FEM) simulations were performed to study the influence of the gap size on the residual stress in CD bars, and experiments were performed to verify the FEM results. The residual stresses were measured with X-ray diffraction in both the axial and the hoop directions.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.4
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• pp.321-327
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• 2003

As the continuous casting process is to product slab with high temperature liquid steel, the main role of strand driven roll is to withdraw slab from mold as operator set up casting speed pattern. The strand driven roll in old cast machine is controlled casting speed only. Due to inaccuracies in drive setting up, varying roll diameters, bulging in the product, withdrawal force was distributed irregularly. As a result, because of horizontal crack in slab comer, high casting speed can't be achieved. In this paper, the correlation between the distribution of withdrawal force and slab quality is investigated and the new control algorithm which can be distributed regularly the withdrawal force of strand driven roll is proposed. The principle of proposed algorithm is not to control motor torque directly but to control motor speed reference according to sharing ratio of withdrawal force which is set up in high level controller. The proposed algorithm implemented in POSCO Kwangyang 1-4 continuous casting plant.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.6977-6984
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• 2015

It is faced with the necessity of multi roll forming process of the ball slide rail which is made by adding the separate manufacturing processes, piercing, bending, trimming, to the roll forming process of a continuous plastic deformation, to improve the quality. However, the vibration and noise of the press machine in this process leads to the quality degradation of slide rail manufactured in this process. In this study, the roll was designed considering the optimal strain rates by the roll forming program with finite element method. And to estimate the static stability of the multi process the Von-Mises stress and deformation on the press was calculated with a structural analysis program. Also, to avoid driving systems in the resonance region their natural frequencies in the 1st and 2nd mode were calculated through the modal analysis. To verify its dynamic stability improvement the magnitudes of noise and vibration in the existing and studied system were compared using a microphone and accelerometers. And the widths and surface roughnesses of the rails which had been produced in the existing and studied process were measured. Therefore, it is known that multi roll forming process is stable in the analytical and experimental study.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2008.06a
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• pp.765-766
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• 2008

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.485-486
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• 2007

• Proceedings of the KWS Conference
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• 2005.11a
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• pp.44-46
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• 2005

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.8
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• pp.855-861
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• 2011

We predict the rolled-strip profile for a 6-high mill using thin rolling theory and a numerical model. In the numerical model, we calculate the distributions of the contact pressures between the rolls and the rolling pressure between the strip and the work roll in the transverse direction using the geometric structure of the 6-high mill and the boundary conditions. We determine the distribution of the rolling pressure in the rolling direction via a thin-foil rolling model using Fleck's theory. We calculate the three-dimensional elastic deformation of the work roll using the pressures of the width and rolling directions. We then obtain the three-dimensional strip profile via the elastic deformation of the work roll during the rolling process. The profile is verified by a thin cold-rolling test and FE simulation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.2
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• pp.271-277
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• 2013

Skin pass rolling is a very important process for applying a certain elongation to a strip in the cold rolling and annealing processes, which play an important role in preventing the stretching of the yield point when the material is processed. The exact prediction of the rolling force is essential for obtaining a given elongation with the steel grade and strip size. Unlike hot rolling and cold rolling, skin pass rolling is used to apply an elongation of within 2% to the strip. Under a small reduction, it is difficult to predict the rolling force because the elastic deformation behavior of the rolls is complicated and a model for predicting the rolling force has not yet been established. Nevertheless, the exact prediction of the rolling force in skin pass rolling has gained increasing importance in recent times with the rapid development of high-strength steels for use in automobiles. In this study, the possibility of predicting the rolling force in skin pass rolling for producing various steel grades was examined using foil rolling theory, which is known to have similar elastic deformation behavior of rolls in the roll bite. It was found that a noncircular arc model is more accurate than a circular model in predicting the roll force of high-strength steel below TS 980 MPa in skin pass rolling.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06b
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• pp.237-239
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• 2011

기존의 오선지를 이용하여 음악을 시각적으로 표현하는 방법은 오선 기보법에 익숙하지 않은 일반 사용자들이 많은 양의 음악적 지식을 습득해야 한다는 제약을 가지고 있다. 현재는 이러한 한계를 개선한 직관적인 음악 표기법 중에서 피아노 롤 표기법이 많이 사용되고 있으나 모바일 환경에서는 단말기 화면 크기의 제약으로 인해 사용자가 원하는 위치에 정확히 음표를 입력하기 불편하다는 문제가 있다. 따라서 모바일 환경에서는 사용자가 월하지 않는 부정확한 입력이 이뤄졌을 경우 빠른 수정이 가능한 직관적인 인터랙티브 인터페이스가 요구된다. 따라서 본 논문에서는 옥타브 줌인/아웃과 함께 기존의 피아노 롤 표기법에서 사용되는 음표를 막대 모양으로 변형시켜 이를 사용자가 터치 앤드래그하여 입력할 수 있는 모바일용 음표 입력 인터페이스를 제안한다.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.357-360
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• 2008

In roll forming process, a sheet metal is continuously progressively formed into a product with required cross-section and longitudinal shape, such as a circular tube with required diameter, wall-thickness and straightness, by passing through a series of forming rolls in arranged in tandem. In this process, each pair of forming rolls installed in a forming machine play a particular role in making up the required cross-section and longitudinal shape of the product. In recent years, that process is often applied to the bumper rail in the automotive industries. In this study, a optimal SILL SIDE manufacturing technology, model deign and proper roll-pass sequences can be suggested by forming number of roll-pass and bending angle. And also effects of the process parameters on the final shape formed by roll forming defects were evaluated.