• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.08a
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• pp.88-97
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• 1999

In this study, a systematic approach for roll pass design in bar rolling was studied. To minimize the trial and errors in the process design, a roll CAD system and a FE analysis system were combined. Based on the system, a methodology for roll pass design by FEM was studied. At first, designed process was compared with the FE analysis results and process redesign based on the FEM results was performed to obtain the specified final geometry. Then, empirical formula for roll speed set-up was compared with the FE analysis results. Further study on various simulations for bar rolling will help in making up for the inaccuracy in the currently used empirical roll speed rules. In addition, verification of the accuracy of the FE analysis system must be performed using experimental data in the industry.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.10a
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• pp.16-29
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• 1995

A full three-dimensional thermo-coupled rigid-viscoplastic finite element method and the currently developed microstructural evolution system which includes semi-empirical mathematical equations suggested by different research groups were used together to form an integrated system of process and microstructure simulation of hot rolling. The distribution and time history of thermomechanical variables such as temperature, strain, strain rate, and time during pass and between passes were obtained FEM analysis of multipass hot rolling processes. Then distribution of metallurgical variables were calculated successfully on the basis of instantaneous thermomechanical data. For the verification of this method the evolution of microstructure in plate rolling and shape rolling was simulated and their results were compared with the data available in literature. Consequently, this approach makes it passible to describe the realistic evolution of microstructure by avoiding the use of erroneous average value and can be used in CAE of multipass hot rolling.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.10a
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• pp.202-209
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• 1997

The mechanical properties of Ti-6Al-4V greatly vary for changes of microstructures. Therefore, when manufacturing components with this material, it is important to understand the influence of process parameters to the resulting microstructures. In the present investgation, it was attempted to relate the process parameters with the microstructures in a hot forged Ti-6Al-4V disk. The investigation was carried out by a rigid thermo-viscoplastic FEM analysis, flow stress measurements and microstructure studies. It was found that the dynamic recrystallization would hardly occur in this material and that variations of strain, strain rate and temperature of several locations in the disk were below the assumed dynamic recrystallization zone. These findings confirmed the experimental obervations that the microstructures in the disk were only deformed without being recrystallized.