Development of egg-configuration heat source model in numerical simulation of autogenous fusion welding process

Abstract

The mathematical structure of the heat source models should at least approximately represent the phenomena of real heat source. In fusion welding process, only the surface heat flux fails to realize enhanced heat transfer due to predominant effect of momentum transport of the material within molten pool. The convection in the weld pool can be substituted by apparent volumetric heat source which is unrealistic to define outside the molten pool volume. The key issues to define a decent volumetric heat source are the geometric shape and size, non-symmetric heat density distribution due to moving arc or laser beam. In present work, the egg-configuration volumetric heat source model is proposed to address these issues. The proposed heat source model which is derived from ellipsoid shape provides the non-symmetry heat energy distribution with less number of model parameters and conserves the continuity in profile during moving heat source problem. The general equation of egg-configuration heat source provides the basis of Gaussian distributed disc, hemispherical, and semi-ellipsoidal volumetric heat source models which can be considered as the special cases of proposed heat source model. A 3D finite element based transient heat transfer analyses is conducted using the proposed heat source model for gas tungsten arc welding (GTAW) and diode laser welding processes. The maximum deviation of 10% in weld pool size estimation is observed as compared to experimental results. The time-temperature history confirms the peak temperatures of 940 K and 1060 K, respectively for GTAW and laser welding processes. The amount of the maximum cooling rate predicted for GTAW is 603 K/s which is significantly lower than 11.1 × 103 K/s for laser welding. Overall, the proposed heat source model generalized the applicability over a wide variety of materials and autogenous fusion welding processes.