Numerical models of gas metal arc welds using experimentally determined weld pool shapes as the representation of the welding heat source

The objectives of this work were to measure the full 3-dimensional weld pool shape for the Gas Metal Are Welding (GMAW) process, and to examine the use of this information within numerical models. A mechanical ejection device instantaneously emptied the molten metal from a weld pool by rapidly accelerating and decelerating the test plate being welded. A non-contact laser profiling system was used for accurate measurement of the exposed weld pool cavity. Welding speed and welding current were found to have the greatest influence on the length of a weld pool, and increasing heat input level yielded higher values for all critical weld pool dimensions. In conductive heat transfer finite element models, the welding are can be represented as a heat flux, but this approach introduces some arbitrariness within the defined heat source. Here, in a novel alternative approach, the measured pool cavity has been used as a fixed temperature boundary in 3D quasi-steady state numerical models of the GMAW process. A comparison of predicted and measured T85 cooling times (time taken to cool between 800 and 500 degrees C) has demonstrated the accuracy and viability of this modelling strategy. (C) 1997 Published by Elsevier Science Ltd.