RESEARCH PAPER Effects of evaporation-determined model of arc-cathode coupling on weld pool formation in GMAW process simulation O. Mokrov 1 & M. Simon 1 & R. Sharma 1 & U. Reisgen 1 Received: 19 September 2019 /Accepted: 28 February 2020 # International Institute of Welding 2020 Abstract Currently used approaches for modeling the cathodic heat input in gas metal arc welding (GMAW) process simulation are usually based on very simplified approaches, either using a Rykalin-Rosenthal-distributed heat flux or a thermal conductivity approach, which do not reflect the deep physical processes involved. In this paper, a new approach for the calculation of the arc-cathode coupling in GMAW is presented, and the influence of the parameter variation on the formation of the weld pool is studied. The evaporation-determined model for arc-cathode coupling (EDACC) takes into account the recent findings on the plasma temper- ature in the GMAW arc, which is dominated by metal vapor, as well as the metal evaporation, which is readily ionized in the cathode region. It determines a relationship between the weld pool surface temperature and the heat flux as well as the current density distribution. As a result, the heat flux as well as the current density distribution is not axisymmetric. In this work, the model was coupled to a simplified weld pool simulation, and the influence of the model parameters like distribution of plasma temperature and welding velocity were investigated. Additionally, also the influence of the droplets on the weld pool surface temperature distribution and its effect on the arc-cathode attachment, as determined by the model, were studied. Keywords GMAW . Cathode . Modeling . Heat flux . Current density . Weld pool 1 Introduction The gas metal arc welding (GMAW) process is widely used in the industry. However, due to the highly dynamic and non- linear behavior of the phenomena involved, the understanding of the physics behind the process is still not fully developed. Therefore, in the simulation of the process, substitution models are being used, which do not capture the full depth of the phenomena and their interactions. Only recently, a mod- el for the cathode boundary layer has been published which can explain the distributions of heat flux and current density in GMAW on a physical basis [1]. In the present work, a study is presented which shows the effect of the new model on the formation of the weld pool and compares it with the effects of the currently widely used Rykalin-Rosenthal (Gaussian- shaped) surface heat source distribution [2]. 2 Problem statement In GMAW process simulation, the realization of the coupling between arc and weld pool is of essential importance for the fluid flow dynamic, which is mainly driven by droplet impact and electromagnetic Lorentz force. However, current ap- proaches usually rely on simplified assumptions like a Rykalin-Rosenthal distribution of heat flux and current density, e.g., [3, 4], or by introducing a heat conduction coefficient between the arc and the weld pool as is realized in [5]. The approach using the Rykalin-Rosenthal distribution is based on the assumption that the processes responsible for the attachment are of statistical nature and therefore normally distributed. However, this approach has several drawbacks; as in general, in this approach, the highest heat flux will be localized at the position of the highest temperature, therefore leading to mas- sive overheating and, when considering a realistic model for evaporation, like [6], also to considerable heat losses in this area Recommended for publication by Study Group 212 - The Physics of Welding * M. Simon simon@isf.rwth-aachen.de 1 ISF – Welding and Joining Institute, RWTH Aachen University, Pontstr. 49, 52062 Aachen, Germany Welding in the World https://doi.org/10.1007/s40194-020-00878-3