• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.327-327
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• 2000

Derivation of a slab dimension from the desired tolerance degrades the product quality, resulting in significant yield loss by trimming. This necessitates the dimensional control system to be operated in tighter dimensional accuracy. This paper presents an integral approach to a dimensional control system design taking into account the interaction between the edging process and the gap rolling process. To investigate the effects of each process controller, a simple PID controller is adopted as a preliminary study. The control performance is analyzed in detail in terms of the system response accuracy for various operating conditions.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.180.2-180
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• 2001

In the hot rolling process, the RF AGC (Roll Force Auto Gauge Control) is used to control the roll gap to reduce the variation of rolling force caused by the roll eccentricity and the variation of material thickness. However the effect of the roll eccentricity cannot be distinguished. To eliminate the effect of the roll eccentricity, the roll eccentricity estimation is needed to supplement some drawbacks of RF AGC. In this paper, an ALE(Adaptive Line Enhancer) that extracts the rolling force variation due to the roll eccentricity is suggested. We also provide an algorithm that enhances the convergence time of roll eccentricity estimation. The performance improvement of the Suggested algorithm is shown via simulations.

• 한국정밀공학회지
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• 제17권9호
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• pp.174-180
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• 2000

A reliable analytic model that determines the cross sectional shape of a workpiece(material) in round-oval(or oval-round) pass sequence has been developed. the cross sectional shape of an outgoing workpiece is predicted by using the linear interpolation of the radius of curvature of an incoming workpiece and that of roll groove to the roll axis direction. The requirements we placed on the choice of the weighting function were to ensure boundary conditions specified. The validity of the analytic model has been examined by hot rod rolling experiment with the roll gap and specimen size changed. The cross sectional shape and area of a workpiece predicted by the proposed analytic model were good agreement with those obtained experimentally. It was found that the analytic model has not only simplicity and accuracy for practical usage but also save a large amount of computational time compared with finite element method.

• 대한기계학회논문집B
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• 제37권5호
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• pp.459-465
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• 2013

열연 판재 제조과정에서는 제품의 강도와 인성을 제어하기 위해 압연 직후 $800^{\circ}C$ 이상의 고온 소재를 수냉각 방식으로 급속 냉각시킨다. 이 과정에는 소재 표면과 냉각수 사이의 비등 열전달 현상과 소재 표면에 쌓이는 체류수의 자유표면 유동, 소재의 고속 주행 등 매우 복잡한 물리현상들을 포함하고 있다. 본 연구에서는 이 모든 물리 현상들을 수치적으로 모델링한 해석 모델을 적용하여 기본 열전달 해석을 수행한다. 실제로 소재는 냉각에 의해 내부에서 오스테나이트로부터 페라이트로 상변태가 일어나고 이로 인해 소재의 국부적인 열물성치의 변화가 발생하지만 본 연구에서는 상변태를 직접 푸는 방법 대신 이미 알려진 소재의 온도에 따른 물성변화 곡선을 이용하여 냉각해석을 수행하고 이를 기존의 일정 물성치 조건에서 해석한 결과와 비교하여 소재의 물성변화가 소재 냉각에 미치는 영향과 상변태 해석의 필요성에 대해 검토하였다.

• 열처리공학회지
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• 제35권2호
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• pp.74-81
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• 2022

This study aims to mitigate the microstructural heterogeneity arising from the manufacture of magnesium alloy plates using the twin roll casting (TRC) process. Homogenization was introduced through hot rolling and heat treatment, followed by confirmation of observed changes in the microstructure. Following the TRC process, the hot rolled 2mm plate exhibited a dendritic cast structure tilted in the roll rotation direction, while central segregation were developed. This nonuniform structure and central segregation disappeared upon heat treatment, followed by recrystallization to form uniform and fine grains. Abnormal grain growth (AGG) was observed over the course of heat treatment; grains exhibiting AGG occupied up to 75% of the total area after having held the sample at 400℃ for 64 h. The formation of coarse grains was also observed during heat treatment at 340℃ over a relatively long duration, though the maximum grain size was significantly smaller than that corresponding to the heat treatment at 400℃. AGG in the 400℃ heat treatment occurred because of movement of the grain boundary, which had been fixed prior as a result of the grain boundary fixing effect of the precipitation phase. The re-dissolution of the Ca₂Mg₅Zn₅ precipitated phase over the long duration of the high-temperature annealing process caused the surrounding grains to disappear and regrow.

• 한국정밀공학회지
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• 제33권4호
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• pp.257-264
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• 2016

Solid state joining techniques are increasingly applied in a wide range of industrial applications. Friction welding is a solid state welding technique that is used to join similar or dissimilar materials. In this study, friction welding was applied to rotor shaft composed of a disk and a shaft. The disk and shaft were manufactured by hot forging and rolling, respectively. The aim of the study was to predict the structural characteristics during hot forging and friction welding process for rotor shaft of turbo charger. The structural characteristics were determined by heat input and heat affected zone (HAZ) during a short cycle time. Thus, transient FE analysis for hot forging and friction welding was based on heat transfer. The results were used to predict structural characteristics during hot forging and friction welding processes. The prototype of rotor shaft was manufactured by the result-based process parameters.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.129.4-129
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• 2001

The looper control of hot strip finishing mill is one of the most important control item in hot strip rolling mill process. Loopers are placed between finishing mill stands and control the mass flow of the two stands. Another important action of the looper is to control the strip tension which influences on the width of the strip. So it is very important to control both the looper angle and the strip tension simultaneously but the looper angle and the strip tension are strongly interacted by each other. There are many control schemes such as conventional, non-interactive, LQ(Linear Quadratic), Hinf and ILQ(Inverse Linear Quadratic), Adaptive(gain scheduling) control in the looper control system. In this paper, we present the modeling for the looper of a hot strip finishing mill to control the tension of the strip and suggest another control method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 D
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• pp.2267-2269
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• 2001

The looper control of hot strip finishing mill is one of the most important control item in hot strip rolling mill process. Loopers are placed between finishing mill stands and control the mass flow of the two stands. Another important action of the looper is to control the strip tension which influences on the width of the strip. So it is very important to control both the looper angle and the strip tension simultaneously but the looper angle and the strip tension are strongly interacted by each other. There are many control schemes such as conventional, non-interactive, LQ, LQG/LTR, and ILQ control in the looper control system. In this paper, we present the modeling for the looper of a hot strip finishing mill to control the tension of the strip and suggest the non-interactive(cross) and LQG/LTR control method.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 Proceedings of the Korea Automatic Control Conference, 11th (KACC); Pohang, Korea; 24-26 Oct. 1996
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• pp.319-323
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• 1996

A new steel-making process, strip-casting, is introduced. The strip-casting is a new technique making the thin steel strip from the molten steel directly without resorting to repetitive reheating and hot-rolling required in a conventional steel-making method. This paper derives the mathematical model of strip caster, proposes a control strategy for stable startup operation and a fuzzy decision making rule for automatic control mode change in strip-casting process.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 춘계학술대회논문집
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• pp.130-133
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• 1998

An integrated finite element computer simulator is presented for the prediction of three dimensional heat transfer and metal flow occurring in the strip, and heat transfer and thermo elastic phenomena occurring in the rolls in 4 high mill hot strip rolling. Basic finite element models are described, with emphasis on combining each model to deal rigorously with the coupled aspect of the thermo-mechanical behaviors of the rols and strip through an iterative solution procedure. A series of process simulation are carried out to investigate the effect of various parameters under the actual process conditions. The results are shown and discussed.