A model for arc-cathode attachment in gas metal arc welding is presented. It considers the cathodic heating in the case of a non-refractory iron cathode, with the assumption of the lowering of the local plasma temperature, due to cold metal vapor. It takes the plasma bulk temperature as well as the cathode drop voltage as free parameters and it gives a maximum of heat flux and current density for a cathode surface temperature below boiling temperature. The applicability as a heat source description in a weld pool simulation has been shown, and the temperature field of the cathode was calculated, giving rise to heat flux and current density distributions, which differ significantly from the converntionally used axisymmetric Gaussian distribution. The maximum cathode surface temperature was lower than boiling temperature, which is in agreement with the observeration.

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While the application of the Smoothed Particle Hydrodynamics (SPH) method for the modeling of welding processes has become increasingly popular in recent years, little is yet known about the quantitative predictive capability of this method. We propose a novel SPH model for the simulation of the tungsten inert gas (TIG) spot welding process and conduct a thorough comparison between our SPH implementation and two finite element method (FEM)-based models. In order to be able to quantitatively compare the results of our SPH simulation method with grid-based methods, we additionally propose an improved particle to grid interpolation method based on linear least-squares with an optional hole-filling pass which accounts for missing particles. We show that SPH is able to yield excellent results, especially given the observed deviations between the investigated FEM methods and as such, we validate the accuracy of the method for an industrially relevant engineering application.

The properties of a thermally sprayed coating, such as its durability or thermal conductivity depend on its microstructure, which is in turn directly related to the particle impact process. To simulate this process, we present a 3D smoothed particle hydrodynamics (SPH) model, which represents the molten droplet as an incompressible fluid, while a semi-implicit Enthalpy-Porosity method is applied for modeling the phase change during solidification. In addition, we present an implicit correction for SPH simulations, based on well-known approaches, from which we can observe improved performance and simulation stability. We apply our SPH method to the impact and solidification of Al$$_2$$ 2 O$$_3$$ 3 droplets onto a substrate and perform a comprehensive quantitative comparison of our method with the commercial software Ansys Fluent using the volume of fluid (VOF) approach, while taking identical physical effects into consideration. The results are evaluated in depth, and we discuss the applicability of either method for the simulation of thermal spray deposition. We also evaluate the droplet spread factor given varying initial droplet diameters and compare these results with an analytic expression from the previous literature. We show that SPH is an excellent method for solving this free surface problem accurately and efficiently.

A transient three-dimensional model that describes physical phenomena inside a welding pool during gas-metal arc welding process is presented. The model considers such phenomena as heat-mass transfer, electromagnetics, hydrodynamic processes and deformation of the weld pool free surface. The fluid flow in the weld pool is induced due to the presence of the mechanical impact of the droplets, thermo-capillary surface tension, thermal buoyancy and electromagnetic forces. The weld pool surface deformation is calculated by considering arc pressure and droplet impact force. A comparative analysis of the impact of the electric current of the welding arc and different force factors causing the motion of liquid metal in the weld pool on the shape of the welded seam was carried out and discussed. Keywords: Arc welding / numerical simulation / hydrodynamics / welded seam formation / droplet impact Es wird ein transientes, dreidimensionales Modell vorgestellt, das die physikalischen Phä nomene in einem Schmelzbad beim Metallschutzgasschweißen beschreibt. Das Modell berü cksichtigt solche Phä nomene wie Wä rme-und Massenü bertragung, elektromagnetische Phä nomene, hydrodynamische Prozesse und die Deformierung der freien Schmelzbadoberflä che. Die Strö mungen im Schmelzbad werden hervorgerufen durch den mechanischen Aufprall der Tropfen, die thermokapillare Oberflä chenspannung, den thermischen Auftrieb und elektromagnetische Krä fte. Bei der Berechnung der Deformation der Schmelzbadoberflä che werden der Lichtbogendruck und die Kraft der auftreffenden Tropfen berü cksichtigt. Eine vergleichende Analyse des Einflusses des elektrischen Stromes des Schweißlichtbogens und der verschiedenen Krä fte, die die Bewegung des flü ssigen Metalls im Schmelzbad verursachen, auf die Form der Schweißnaht wurde durchgefü hrt und diskutiert. Schlü sselwö rter: Lichtbogenschweißen / numerische Simulation / Strö mungen / Schweißnahtbildung / Tropfenwirkung