Development of avocado shape heat source model for finite element based heat transfer analysis of high-velocity arc welding process

Abstract

The mathematical representation of the welding heat source is a critical task as the competence of the model decides the prediction accuracy of the thermal profile of the welded joint. The geometric shape of the moving heat source in fusion welding is a strong function of weld velocity. The elliptical shape conforms to the non-symmetric volumetric energy distribution by a double-ellipsoidal heat source model at low speed. However, the geometric conformity of the elongated weld pool may not be elliptical at relatively high welding speed. In the present work, a new volumetric heat source model, the so-called avocado shape, is proposed, a more realistic approximation of the applied volumetric heat flux and flexible enough to accommodate a wide variation of welding conditions. The proposed model is a modified version of ellipsoidal shape with non-symmetrical energy distribution and unequal axis length in the front and rear parts along the weld velocity vector. Thus, it is different from the double-ellipsoidal model in terms of user-defined parameters and from the egg-configuration model in terms of unequal axis lengths. The avocado shape heat source model is self-consistent since it estimates all the parameters from weld width and depth of penetration. The heat source follows the Gaussian distribution of volumetric energy flux for a moving heat source problem. A finite element based heat transfer analysis is performed using the avocado shape heat source model for gas tungsten arc welding (GTAW) and submerged arc welding (SAW) processes. Compared with the experimentally measured weld dimensions, time-temperature history and microstructure evaluate the prediction accuracy of the proposed heat source model.