Prediction of welding residual stress with real-time phase transformation by CFD thermal analysis

A new method of numerical thermal-metallurgical-mechanical analysis for the gas metal arc welding process is proposed. The latest thermal-metallurgical analysis method, using real-time temperature and phase fraction history was employed in this study. The thermal-metallurgical strain behavior of a wide temperature range of austenization is considered, using dilatometry information and temperature and phase fraction dependent mechanical properties. A simple volumetric strain balance was used to describe the effect of phase transformation in the mechanical analysis. Following validation of the thermal-metallurgical analysis, the stress distribution predicted by the thermal-metallurgical-mechanical analysis was compared with measured directional stresses. In the results, the phase transformed weldment did not always appear to be expanded when a wide range of austenization temperatures was considered in the heating process. Moreover, the thermal-metallurgical-mechanical analysis of the welding process identified stress concentration on the near welding line, and nonlinear deflection by the gradient of total volumetric strain, and phase dependent yield strength. However, the model for this study did not consider the mechanical history reset of the liquid state. Also, the limitation of the stress measurement method made it difficult to make a detailed comparison with the calculated results. The model change method to allow treatment of the liquid state, and a neutron diffraction method for complete validation, will be utilized in future work to overcome these limitations.