https://web.mst.edu/~tsai/Published%20papers/Hu-IJHMT-2006-1.pdf

Heat and mass transfer in gas metal arc welding. Part II: The metal

https://web.mst.edu/~tsai/publications/Rao-IJHMT-2010-2-18.pdf

Modeling of the transport phenomena in GMAW using argon-helium mixtures. Part II - The metal

Most previous three-dimensional modeling on gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) focuses on the weld pool dynamics and assumes the two-dimensional axisymmetric Gaussian distributions for plasma arc pressure and heat flux. In this article, a three-dimensional plasma arc model is developed, and the distributions of velocity, pressure, temperature, current density, and magnetic field of the plasma arc are calculated by solving the conservation equations of mass, momentum, and energy, as well as part of the Maxwell’s equations. This three-dimensional model can be used to study the nonaxisymmetric plasma arc caused by external perturbations such as an external magnetic field. It also provides more accurate boundary conditions when modeling the weld pool dynamics. The present work lays a foundation for true three-dimensional comprehensive modeling of GTAW and GMAW including the plasma arc, weld pool, and/or electrode.

/pdf/three-dimensional-modeling-of-the-plasma-arc-in-arc-welding-afx5g5idt9.pdf

Three-Dimensional Modeling of the Plasma Arc in Arc Welding

In this thesis the objective is to optimize the control algorithms for the manual pulsed Gas Metal Arc Welding (GMAW) process, with the aim of enhancing the quality of welded joints. To be able to develop controllers for the GMAW process, and also for enabling process simulation, a mathematical model describing the GMAW process is developed. The mathematical model includes a description of the electrical circuit, the drop dynamics, and the melting rate, and also, the model includes criteria for drop detachments. Basically, the electrical circuit consists of the welding machine, the wires, the electrode, and the electrical arc. The drop is modelled as a mass-spring-damper system influenced by a number of external forces. Of these external forces the electromagnetic force is the most significant. Due to the importance of the electromagnetic force, a thorough derivation of the electromagnetic force is included in the thesis. The melting rate of the consumable electrode is modelled both from a statically (steady-state) point of view, and from a dynamically point of view. The static model is a simple equation describing the melting rate, while the dynamic model is more complex. The structure of GMAW control is discussed, and based on this discussion a general control structure is presented. This structure includes an arc length controller and a metal transfer controller, and also, an inner loop controlling the welding current. The current is assumed to be controlled by a traditional PI-controller, and therefore, this inner control loop is not considered in the thesis. For arc length control, a nonlinear controller based on feedback linearization is proposed, and robustness and performance are considered. For metal transfer control an approach based on obtaining a uniform drop size prior to pulse initiation is proposed. This is carried out by calculating the amount of melted electrode between the current pulses during the welding process. The purpose of the uniform drop size approach is to enhance the robustness of the drop detachment process. In addition to the arc length controller and the metal transfer controller, an arc length minimization algorithm is proposed for enhancing the ability to focus the arc, and also, to minimize the heat input into the workpiece. Simulation programs for testing the controllers and algorithms have been developed, and successful tests have been carried out.

/pdf/advanced-control-methods-for-optimization-of-arc-welding-4yq0936pdl.pdf

Advanced Control Methods for Optimization of Arc Welding

This article analyzes the transient complex heat transfer and fluid flow in molten metal and arc plasma during the gas metal arc welding process. The model predicts the formation, growth, detachment, and transfer of droplets from the tip of a continuously fed electrode under the influences of several competing forces including gravity, electromagnetic force, arc pressure, plasma shear stress, and surface tension. Simulations were conducted for five different current levels to study the effects of current on the distributions of temperature, velocity, pressure, and current density in the droplet and/or the arc plasma. Agreement between the simulated results and published experimental data was obtained.

/pdf/metal-transfer-and-arc-plasma-in-gas-metal-arc-welding-2x9ungf5h8.pdf

Metal Transfer and Arc Plasma in Gas Metal Arc Welding

A theoretical model of a gas metal arc welding system has been developed to make predictions of the anode temperature profile, welding arc length and arc current. The model incorporates a one-dimensional thermal model of the moving consumable anode and a two-dimensional model for the arc plasma. The model makes possible the calculation of the relationship between the welding arc current, wire feed rate and the supply voltages, for various wire diameters and shielding gases. The predicted welding current for a given wire feed rate shows good agreement with our experimental observation for operation in the spray transfer mode, for steel wire of two different diameters, assuming a workpiece sheath voltage of 15 V.

https://iopscience.iop.org/article/10.1088/0963-0252/4/3/020/pdf

S W Simpson

Papers

A theoretical study of a gas metal arc welding system