Welding has been widely used in many fields of industry. Its advantages include high efficiency of joining, simple operation, good flexibility and low cost. However, uneven temperature distribution inevitably exists during welding. Such uneven temperature distribution causes rapid thermal expansion, which leads to heterogeneous plastic deformation by thermal constriction in and near the welding joint. Thus, residual stress appears in welding structure after cooling.
In order to accurately predict welding residual stress and deformation, welding temperature distribution should be simulated properly. What is important in welding simulation is to apply suitable heat source models according to the welding methods. The models include spot heat source model, line heat source model (HSM), surface heat source model and volume heat source model. As heat is transferred to workpieces in the form of volume in most welding methods, volume HSM is most widely used. Volume HSM is classified into semi-sphere HSM, elliptical heat source model and double-elliptical heat source model. At present, double-elliptical model is accepted as the most appropriate heat source model for gas metal arc welding (GMAW) with steep temperature slope at the front section of the welding pool and smooth slope at the rear section.
Cha Kwang Jin, a researcher at the Faculty of Materials Science and Technology, has performed a welding temperature simulation by FEM and predicted temperature distribution while varying welding parameters such as welding current.
For the simulation, he employed ANSYS software widely used for welding simulations across the world that offers the most approximate parameters to the desired result by varying several parameters of its own optimization module.
The FEM analysis results and experiment results of welding show that the analysis result is accurate when Gauss-distributed double-elliptical heat source for GMAW process simulation is used.