Ho Won Lee | Korea Advanced Institute of Science and Technology (original) (raw)

Papers by Ho Won Lee

Research paper thumbnail of Adaptive characterization of recrystallization kinetics in IF steel by electron backscatter diffraction

Journal of Microscopy, 2013

In this study, a rigorous methodology for quantifying recrystallization kinetics by electron back... more In this study, a rigorous methodology for quantifying recrystallization kinetics by electron backscatter diffraction is proposed in order to reduce errors associated with the operator's skill. An adaptive criterion to determine adjustable grain orientation spread depending on the recrystallization stage is proposed to better identify the recrystallized grains in the partially recrystallized microstructure. The proposed method was applied in characterizing the microstructure evolution during annealing of interstitial-free steel cold rolled to low and high true strain levels of 0.7 and 1.6, respectively. The recrystallization kinetics determined by the proposed method was found to be consistent with the standard method of Vickers microhardness. The application of the proposed method to the overall recrystallization stages showed that it can be used for the rigorous characterization of progressive microstructure evolution, especially for the severely deformed material.

Research paper thumbnail of Numerical Prediction of Austenite Grain Size in Round-Oval-Round Bar Rolling

ISIJ International, 2003

In bar or rod rolling process, improvement of mechanical properties of the hot rolled products re... more In bar or rod rolling process, improvement of mechanical properties of the hot rolled products requires numerical prediction of austenite grain size (AGS) for better controlling the microstructural evolution. In this study, a fully three-dimensional finite element (FE) program, which can simulate three-dimensional deformation and heat transfer was integrated with an AGS evolution model available in the literature. It was applied to a four-pass round-oval-round rolling sequence to characterize the AGS distributions depending on the change of roll gap and rolling speed. The predicted AGS distribution obtained from the FE based approach was compared with that obtained from the approximate analytical approach based on elementary theory of plasticity, developed for practical purpose. It was found out that reducing roll gap and increasing the rolling speed leads to fine and uniform grain distribution and recrystallization behavior divided into meta-dynamic and static recrystallization region, respectively. In addition, AGS predicted from the approximate analytical approach was in agreement with that from the FE based approach, but showed discrepancies at higher rolling speed conditions investigated in the present work.

Research paper thumbnail of Numerical Prediction of Austenite Grain Size in Round-Oval-Round Bar Rolling

ISIJ International, 2003

In bar or rod rolling process, improvement of mechanical properties of the hot rolled products re... more In bar or rod rolling process, improvement of mechanical properties of the hot rolled products requires numerical prediction of austenite grain size (AGS) for better controlling the microstructural evolution. In this study, a fully three-dimensional finite element (FE) program, which can simulate three-dimensional deformation and heat transfer was integrated with an AGS evolution model available in the literature. It was applied to a four-pass round-oval-round rolling sequence to characterize the AGS distributions depending on the change of roll gap and rolling speed. The predicted AGS distribution obtained from the FE based approach was compared with that obtained from the approximate analytical approach based on elementary theory of plasticity, developed for practical purpose. It was found out that reducing roll gap and increasing the rolling speed leads to fine and uniform grain distribution and recrystallization behavior divided into meta-dynamic and static recrystallization region, respectively. In addition, AGS predicted from the approximate analytical approach was in agreement with that from the FE based approach, but showed discrepancies at higher rolling speed conditions investigated in the present work.

Research paper thumbnail of Cellular Automata Modeling of Grain Coarsening and Refinement during the Dynamic Recrystallization of Pure Copper

MATERIALS TRANSACTIONS, 2010

In this study, a cellular automata technique was developed to simulate a dynamic recrystallizatio... more In this study, a cellular automata technique was developed to simulate a dynamic recrystallization process of pure copper. Moore's neighboring rule was applied with partial fraction and time step control in the current approach to represent the grain growth kinetics more accurately. The cellular automata model developed in this study was applied to a simulation of the dynamic recrystallization of pure copper during hot deformation and compared with the experimental flow stresses and grain sizes determined from hot compression tests for validation. The predicted results were in reasonably good agreement with the experimental results. The grain coarsening and refinement phenomena were also investigated in detail. Finally, the effects of the process parameters on the microstructure and flow stress were investigated from various simulation results.

Research paper thumbnail of Cellular Automata Modeling of Grain Coarsening and Refinement during the Dynamic Recrystallization of Pure Copper

In the automobile industry, there is currently a strong driving force to produce high-strength me... more In the automobile industry, there is currently a strong driving force to produce high-strength metals owing to environmental and energy concerns. The basic strengthening mechanisms include substructural strengthening, solid solution strengthening, precipitation strengthening, grain boundary strengthening, and phase transformation strengthening. In particular, grain boundary strengthening through grain refinement is known to enhance both the strength and toughness of a material. 1)

Research paper thumbnail of Research activities of computer-aided materials processing laboratory

AbstrAct Purpose: of this paper is to review the research works carried out at the national resea... more AbstrAct Purpose: of this paper is to review the research works carried out at the national research laboratory for computer-aided materials processing at the department of mechanical engineering at KAIST.

Research paper thumbnail of Adaptive characterization of recrystallization kinetics in IF steel by electron backscatter diffraction

Journal of Microscopy, 2013

In this study, a rigorous methodology for quantifying recrystallization kinetics by electron back... more In this study, a rigorous methodology for quantifying recrystallization kinetics by electron backscatter diffraction is proposed in order to reduce errors associated with the operator's skill. An adaptive criterion to determine adjustable grain orientation spread depending on the recrystallization stage is proposed to better identify the recrystallized grains in the partially recrystallized microstructure. The proposed method was applied in characterizing the microstructure evolution during annealing of interstitial-free steel cold rolled to low and high true strain levels of 0.7 and 1.6, respectively. The recrystallization kinetics determined by the proposed method was found to be consistent with the standard method of Vickers microhardness. The application of the proposed method to the overall recrystallization stages showed that it can be used for the rigorous characterization of progressive microstructure evolution, especially for the severely deformed material.

Research paper thumbnail of Numerical Prediction of Austenite Grain Size in Round-Oval-Round Bar Rolling

ISIJ International, 2003

In bar or rod rolling process, improvement of mechanical properties of the hot rolled products re... more In bar or rod rolling process, improvement of mechanical properties of the hot rolled products requires numerical prediction of austenite grain size (AGS) for better controlling the microstructural evolution. In this study, a fully three-dimensional finite element (FE) program, which can simulate three-dimensional deformation and heat transfer was integrated with an AGS evolution model available in the literature. It was applied to a four-pass round-oval-round rolling sequence to characterize the AGS distributions depending on the change of roll gap and rolling speed. The predicted AGS distribution obtained from the FE based approach was compared with that obtained from the approximate analytical approach based on elementary theory of plasticity, developed for practical purpose. It was found out that reducing roll gap and increasing the rolling speed leads to fine and uniform grain distribution and recrystallization behavior divided into meta-dynamic and static recrystallization region, respectively. In addition, AGS predicted from the approximate analytical approach was in agreement with that from the FE based approach, but showed discrepancies at higher rolling speed conditions investigated in the present work.

Research paper thumbnail of Numerical Prediction of Austenite Grain Size in Round-Oval-Round Bar Rolling

ISIJ International, 2003

In bar or rod rolling process, improvement of mechanical properties of the hot rolled products re... more In bar or rod rolling process, improvement of mechanical properties of the hot rolled products requires numerical prediction of austenite grain size (AGS) for better controlling the microstructural evolution. In this study, a fully three-dimensional finite element (FE) program, which can simulate three-dimensional deformation and heat transfer was integrated with an AGS evolution model available in the literature. It was applied to a four-pass round-oval-round rolling sequence to characterize the AGS distributions depending on the change of roll gap and rolling speed. The predicted AGS distribution obtained from the FE based approach was compared with that obtained from the approximate analytical approach based on elementary theory of plasticity, developed for practical purpose. It was found out that reducing roll gap and increasing the rolling speed leads to fine and uniform grain distribution and recrystallization behavior divided into meta-dynamic and static recrystallization region, respectively. In addition, AGS predicted from the approximate analytical approach was in agreement with that from the FE based approach, but showed discrepancies at higher rolling speed conditions investigated in the present work.

Research paper thumbnail of Cellular Automata Modeling of Grain Coarsening and Refinement during the Dynamic Recrystallization of Pure Copper

MATERIALS TRANSACTIONS, 2010

In this study, a cellular automata technique was developed to simulate a dynamic recrystallizatio... more In this study, a cellular automata technique was developed to simulate a dynamic recrystallization process of pure copper. Moore's neighboring rule was applied with partial fraction and time step control in the current approach to represent the grain growth kinetics more accurately. The cellular automata model developed in this study was applied to a simulation of the dynamic recrystallization of pure copper during hot deformation and compared with the experimental flow stresses and grain sizes determined from hot compression tests for validation. The predicted results were in reasonably good agreement with the experimental results. The grain coarsening and refinement phenomena were also investigated in detail. Finally, the effects of the process parameters on the microstructure and flow stress were investigated from various simulation results.

Research paper thumbnail of Cellular Automata Modeling of Grain Coarsening and Refinement during the Dynamic Recrystallization of Pure Copper

In the automobile industry, there is currently a strong driving force to produce high-strength me... more In the automobile industry, there is currently a strong driving force to produce high-strength metals owing to environmental and energy concerns. The basic strengthening mechanisms include substructural strengthening, solid solution strengthening, precipitation strengthening, grain boundary strengthening, and phase transformation strengthening. In particular, grain boundary strengthening through grain refinement is known to enhance both the strength and toughness of a material. 1)

Research paper thumbnail of Research activities of computer-aided materials processing laboratory

AbstrAct Purpose: of this paper is to review the research works carried out at the national resea... more AbstrAct Purpose: of this paper is to review the research works carried out at the national research laboratory for computer-aided materials processing at the department of mechanical engineering at KAIST.