Papers by Author: Hee Seon Bang

Abstract: In this paper, the characteristics of bond interface and bonding mechanism were investigated with peeling-off method. The fracture was observed and interfacial composition was certified by map scanning of EDX (Energy dispersive X-ray analysis). Based on the features of interfacial characters, the actual joining area mainly distributed at bond periphery; non-bonded at bond center. When the bonding time was lower, the ratio of the bond length to its width was larger and elemental aluminum distributed discontinuously on the bond fracture, primarily at the periphery. After aging, the fractures were also analyzed and Cu2Al3 intermetallic compound (IMC) was identified. The phenomena of bond interfacial tracings were analyzed, and the bonding mechanism was ascribed to plastic flow analyzed by finite element method based on the contact issues.

Abstract: Analytic procedure for dissimilar materials welding problem by using developed in-house solver is applied on butt and lap jointed model. In addition, the procedure of data transferring between commercial package and in-house solver for the preparation of input data for in-house solver has been developed. Therefore we can use the commercial package as pre and post processor for in-house solver and the results from in-house solver, for example, welding residual stress can be exported to commercial package as initial value to the model and then further analysis with the application of external loading can be carried out. For the similar material welding the welding residual stress has been decided by temperature dependent material properties that are input to the source program. In the case of dissimilar welding problem due to the difference of expansion and shrinkage rate between aluminum and steel there has been a slight variation in this dependency. Since the aluminum has large thermal expansion coefficient and the mechanical melting point is lower than steel, the order and level of mechanical behavior like stress history become different. The degree of mechanical deterioration of dissimilar materials welded model has been assessed with various view aspects, namely, welding residual stress, plastic strain, equivalent plastic strain and plastic work distribution and it has been revealed that Al5052 is mechanically more sever than SPCC for same heat input.

Abstract: Friction stir welding is being attracted and developed as an efficient joining method in the manufacturing field of Automobile, Aerospace and Ship building industries. As the FSW develops, more scientific research work investigations in this field have also been increased. Recent studies in FSW have revealed that both heat and metal flow characteristics have a non-symmetric complex nature about the tool axis. But until now there is no efficient 3D- heat flow model to be comparable with the experimentally measured values. The body of the work covered FSW of Al6061 and its thermal distribution based on a nonsymmetrical analytical model for the heat input in to the matrix of Al plates from FSW tool due to the effect of combined translation and rotational motion of the tool pin and shoulder. Finally the 3D- finite element heat transfer analysis program has been used to plot the heat distribution at the Friction Stir Welded joint in Al 6061 plate. The work concludes that the heat distribution result obtained from FE analysis has a reasonable agreement with the experimentally measured values.