• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.10a
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• pp.7-15
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• 1995

An application-oriented approach to automatic pass schedule design in shape rolling was presented in this paper. The design approach and its related program are composed of several modules for input data, graphic display, data processing, calculation of design information, drawing of detailed pass shapes, database management and finite element analysis for design verification. The developed program was applied to automatic pass schedule design for a square-to-round bar shape rolling.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.217-218
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• 2007

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.1
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• pp.376-385
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• 1991

For manufacturing trimming-free plates which have rectangular shaped edges and straight edges in as-rolled state, it is necessary to investigate rolling characteristics of overlap, bulge and width deviation etc. in a standardized plate rolling process. The present wok is for preventing edge overlap as the first approach to develop trimming-free plate rolling technique. An experimental study on overlap control was done with plasticine material in order to examine influence factors and find a control method by use of a laboratory mill scaled down to one tenth of actual production mill. It was found that edge overlapping was increased with the increase of slab thickness and of broadside rolling ratio, but decreased with the increase of chamfered amount on slab edges. In the simulated rolling experiment with edge chamfered slabs of various chamfered angles, the chamfered angle of 60.deg. was the most effective one for reducing overlapping irrespective of slab thickness and of broadside rolling ratio.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.5 s.176
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• pp.1215-1230
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• 2000

Parallel Approaches using Cray T3E which is NIPP (Massively Parallel Processors) machine are presented for the efficient computation of the finite element analysis of 3-D shape rolling processes. D omain decomposition method coupled with parallel linear equation solver is used. Domain decomposition is applied for obtaining element tangent stifffiess matrices and residual vectors. Direct and iterative parallel algorithms are used for solving the linear equations. Direct algorithm is_parallel version of direct banded matrix solver. For iterative algorithms, the well-known preconditioned conjugate gradient solver with Jacobi preconditioner is also employed. Moreover a new effective iterative scheme with block inverse matrix preconditioner, which is named by present authors, is presented and its results are compared with the one using Jacobi preconditioner. PVM and MPI are used for message passing and synchronization between processors. The performance and efficiency of each algorithm is discussed and comparisons are made among different algorithms.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1091-1096
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• 2003

It is very important to find out causes of strip pinching for the high quality of products and for the stable operation of hot roiling system. We have examined the strip pinching from three points of view to find out the causes of strip pinching in hot rolling system: strip shape, rolling operation conditions, and behavior of strip. Wedge, off center, and difference of rolling force through CMD are found to possibly provide major initial causes of strip pinching. Generally strip pinching occurred in the tail of strip. Thus, computer simulations by using a FEM code were also carried out to find out the initial mechanism of strip pinching depending upon the force and geometric boundary conditions at the time of strip tail rolling. The strong compression force effect due to the sudden release of strip tail from the work roll and non-uniform strip tail shape (ex. Tongue tail) across the CMD were found to provide possible major causes of strip pinching.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.381-383
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• 2005

This paper is concerned with the prediction of micro structural changes of Al alloys during cryogenic rolling using an Eulerian finite element analysis. The main objective of cryogenic rolling is to obtain ultra-fine grains by severe plastic deformation at the extremely low temperature. Thereby, this simulation focuses on micro structural developments - the texture development and the changes in the size and shape of grains. The former one may be modeled using a crystal plasticity theory while the other can be predicted by a streamline technique. Applications to three pass rolling are given.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.219-221
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• 2006

Asymmetrical rolling was performed by rolling AA 1050 sheets with different velocities of upper and lower rolls. In order to study the effect of roll gap geometry on the evolution of strain states and textures during asymmetrical rolling, the reduction per rolling pass was varied. After asymmetrical rolling, the outer thickness layers depicted shear textures and the center thickness layers displayed a random texture. With decreasing reduction per an asymmetrical rolling pass, the thickness layers depicting shear textures increases. The strain states associated with asymmetrical rolling were investigated by simulations with the finite element method (FEM).

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.142-149
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• 1999

Strip profile and shape control is one of the most important technologies in cold mill, especially for ultra-thin and wide cold strip. The 6-high mills, both of HCMW and UCMW mill, are known to be very effective for the shape controllability. The optimized values of these factors for set-up scheduling were analyzed and found that excellent strip control would be possible by controlling the combination of the influencing factors according to hot coil profile. The important considerations for operation were discussed for individual stand.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.94-97
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• 1997

금속을 반고상 상태에서 성형하기 위하여 미세조직학적 거동을 밝히기 위해, 본 연 구에서는 높은 비강도, 내마모성을 가진 과공정 Al-Si 합금을 반응고 가공하였을 때의 미세 조직과 상온 가공 후 반고상 온도로 일정시간 유지하였을 때의 미세조직을 관찰하였다. 일 반주조시의 개량 원소 P과 Sr을 첨가하였으며 쐐기형 주조재, 압연재, Si 입자강화 Alrl 복 합재료를 반고상 상태로 가열한 미세조직을 관찰하여 초정 Si입자의 형상 변화를 관찰하였 다. 반응고 교반시 초기에는 P과 Sr의 첨가에 의해 초정 Si입자가 미세화 되었으나 교반이 지속되어 가면서 이러한 경향은 감소하였으며 구상에 가까운 형태로 변화 하였는데, 이는 교반이 지속되면서 첨가 원소의 효과보다 교반 자체의 미세조직 변화 기구에의 의존도가 높 아지기 때문인 것으로 사료된다. 냉각속도를 달리한 쐐기 형상에서의 금형에서 주조된 미세 조직을 관찰한 결과 냉각속도가 느릴 때에만 첨가원소의 영향이 나타났으며, 반고상 온도 유지 후 초정 크기에는 큰 변화가 없었으나 $\alpha$-halo가 형성되고 미세한 Si입자가 생성되었 다. 이는 입자 크기의 성장에 따른 주위의 농도구배로 인해 생성된 것으로 사료된다. 압연시 첨가원소는 핵생성과 재결정을 촉진시켜 초정 Si의 크기를 크게 감소시켰다. 반용융 처리시 초정 Si입자는 약간 성장하였으며, $\alpha$-halo도 생성되었다. 압출한 시료를 반용융 처리한 경 우 Si입자의 형상 변화는 거의 없었으며, Si입자에 형성되어 있던 산화막이 기지와 초정 Si 압자간의 확산장벽으로 작용하여 $\alpha$-halo가 거의 생성되지 않았다. 반응고 교반시 미세조직 변화 기구로는 취성파괴, 합체, 마모를 제안하였으며, 각 공정에서의 초정 Si결정의 크기를 비교하였을 때 45$\mu\textrm{m}$ 이하의 분말을 섞어 압출하였을 때 가장 작은 초정 Si입자 크기를 얻음 을 볼 수 있었다.

• Transactions of Materials Processing
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• v.10 no.7
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• pp.579-583
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• 2001

Shape changes of a workpiece in an Eulerian Finite Element analysis for the steady state, three-roll-stand shape rolling are modelled. Although an Eulerian analysis has many advantages for the steady state rolling problems, it necessitates an assumption about the unknown shape of the control volume. In almost all cases, the assumed control volume does not match the final shape and the control volume should be updated. This update can be accomplished by performing a free surface correction. The final shape of a material point, which has a spherical shape at the inlet, can be also predicted by integrating a deformation gradient along a stream line. Analyses of three-roll-stand shape rolling are performed and the results are discussed in detail.