• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.156-158
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• 2003

Sheets of aluminum alloy 1050 were asymmetrically cold rolled in a rolling mill with different roll speeds. In order to promote the shear deformation during asymmetrical rolling, cold rolling without lubrication was performed. The variation of the shear strain state during asymmetrical rolling was tackled by means of FEM calculations. Asymmetrical rolling gave rise to the development of pronounced residual shear strain gradients throughout the thickness layers.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.69-77
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• 1999

Roll profile design in spape rolling with a complex-shaped part depends on the designer's experience, which is general, is acquired through costly trial-and-error process. As a prerequisite for developing a scientific approach to roll profile design, we present a finite element model to simulate 3-D deformation of complex-shaped parts occuring in multi-pass sequence. Demonstrated is the process model's capability to deal with rolling of a complex-shaped part.

• Journal of Mechanical Science and Technology
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• v.16 no.10
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• pp.1296-1302
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• 2002

A mathematical model for cold rolling and temper rolling process of thin steel strip has been developed using the influence function method. By solving the equations describing roll gap phenomena in a unique procedure and considering more influence factors, the model offers significant improvements in accuracy, robustness and generality of the solution for the thin strip cold and temper rolling conditions. The relationship between the shape of the roll profile and the roll force is also discussed. Calculation results show that any change increasing the roll force may result in or enlarge the central flat region in the deformation zone. Applied to the temper rolling process, the model can well predict not only the rolling load but also the large forward slip. Therefore, the measured forward slip, together with the measured roll force, was used to calibrate the model. The model was installed in tile setup computer of a temper rolling mill to make parallel setup calculations. The calculation results show good agreement with the measured data and the validity and precision of the model are proven.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.05a
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• pp.221-224
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• 2004

The clad samples of five plies of sheets comprising ferritic stainless steel (STS) and aluminum (Al) were prepared by roll-cladding at $350^{\circ}C$. The evolution of strain states and textures during roll-cladding of STS430/AA3003/AA3003/AA3 003/STS430 and STS430/AA3003/STS430/AA3003/STS430 was investigated by measurements of crystallographic textures and by simulations with the finite element method (FEM). Because the deformation mainly occurs in the Al layer during roll-cladding, the present investigation was focused on the Al layers located. The stacking sequence of sheet materials in the clad samples played an important role in the evolution of strain states during roll-cladding.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.6
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• pp.96-103
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• 2002

The objective of this study is to adjust the roll gap fur the dimension accuracy of bar in hot bar rolling process considering roll wear. In this study hot bar rolling processes fur round and oval passes have been investigated. In order to predict the roll wear, the wear model is reformulated as an incremental from and then wear depth of roll is calculated at each deformation step on contact area using the results of finite element analysis, such as relative sliding velocity and normal pressure at contact area. Archard's wear model was applied to predict the roll wear. To know the effects of thermal softening of DCI (Ductile Cast Iron) roll material according to operating conditions, high temperature micro hardness test is executed and a new wear model has been proposed by considering the thermal softening of DCI roll expressed in terms of the main tempering curve. The new technique developed in this study for adjusting roll gap can give more systematically and economically feasible means to improve the dimension accuracy of bar with full usefulness and generality.

• Transactions of Materials Processing
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• v.25 no.3
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• pp.169-175
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• 2016

The hearth roll, which transfers the cold-rolled strip sheet in a Continuous Annealing Line (CAL), is always subjected to changes in the surface temperature and subsequently experiences thermal stress in service. These variations lead to the generation of thermal cracks on the hearth roll surface as well local plastic deformation. We performed finite element analysis to predict the thermal stress changes on the hearth roll surface and designed the collar shape of the hearth roll to minimize these thermal stresses. Results show that the hearth roll with a collar having an obtuse angle is much more effective than a hearth roll with collar having a right angle when the tangential stress, which is one of main causes leading to surface cracks, is compared for the various conditions. It was found that the tangential stress and the temperature on the surface of hearth roll can be reduced by 51.9% and 26℃ if the shape of roll on collar is re-designed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.05a
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• pp.413-416
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• 2006

Two clad composites of five ply sheets comprising STS430/AA3003/AA3003/AA3003/STS430 and STS430/AA3003/STS430/AA3003/STS430 were produced by roll cladding at $350^{\circ}C$. In order to clarify the deformation behavior and strain states in the composites during roll cladding, the variation of individual sheet thickness and the evolution of through thickness textures and microstructures of the composites were investigated. The thickness reduction of each sheet depended on the location of the sheet and on the strength of each sheet in the composites. In order to elucidate the evolution of textures and microstructures in AA3003 sheets, the strain states in AA3003 sheets during roll cladding were calculated by FEM. The formation of shear textures and fine grains in AA3003 sheet was discussed in terms of the strain states in each sheet layer. Finally, the strain states extracted from the FEM were verified by texture simulations

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.400-403
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• 2008

For the effective manufacture of doubly curved metal plates, a line array roll set (LARS) process is proposed. The suggested process utilizes a pair of upper and lower symmetric roll assemblies. In the process, the initial plate is progressed into the final shape in a stepwise or pathwise manner according to the basic principle of the incremental forming process. The deformation proceeds simultaneously in the longitudinal and transverse directions. Moreover, there is a close correlation between the deformation in the longitudinal direction and that in the transverse direction of the plates. Therefore, the finally formed shape in the incremental forming process is strongly dependent upon process conditions, such as the forming path and the forming increment. The manufacturing of arbitrary doubly curved plates with various curvatures is not an easy task because of such complicated behaviors of the plate; thus, the forming schedules for the desired shape should be carefully and accurately designed. In this study, several experiments with the LARS system were carried out for the fundamental investigation on process design for manufacturing of doubly curved plates.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.366-372
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• 1999

The deformation behavior of commercial stainless steels under hot rolling conditions was investigated by means of hot compression tests performed in the temperature range 800$^{\circ}C$ to 1200$^{\circ}C$. The measured flow stress-strain curves were analyzed by using a simple flow stress model. It was found that the reference strength of stainless steels are much higher than that of carbon steel and that nitrogen and molybdenum alloying greatly increases flow stress of austenitic stainless steel. Ferritic and duplex stainless steel showed comparatively low flow stresses. The flow stress model, which correlates the flow stress with temperature and strain rate, was applied to predict roll forces during hot-plate rolling of stainless steels.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.5
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• pp.9-15
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• 2013

Roll-to-roll printing technology has lately become a subject of special interests in the field of printed electronics. Since this technology has the advantage that continuous and mass production is possible. And for high precision register control is required in multi-layer printing to produce the electronic devices, this is one of the most important technologies in roll-to-roll printing technology. Register error could be generated by various reasons like eccentricity of roll and thermal deformation due to temperature variation in drying section. In this study, the effect of tension variation on the register was analyzed. The results of these analyses show that it is essential to consider the tension disturbance which is generated by the change of temperature in drying section, and conventional register model has limitation to estimate the register error. In order to overcome the limitation of the register model, advanced register model based on the SI process was developed. Also, the performance of the developed model was verified experimentally.