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

This paper presents the development of an electrode extension model for the gas metal arc welding process based on the process voltage. The full dynamic model for the electrode extension is derived by combining a dynamic resistivity model with the voltage model. The electrode extension model was found to be represented mathematically by a nonlinear, time-varying, second-order ordinary differential equation. This model can be used in through-the-arc sensing and arc length control systems. To experimentally verify the model, the process dynamics were excited by a continuous sinusoidal variation of arc current. Using a constant current power source with the electrode positive, sinusoidal perturbations of variable amplitude were superimposed on the current to allow direct measurement of changes in electrode extension, arc length, and total voltage. A high-speed video system was used to capture the experimental electrode extension dynamics. The model was verified by comparing the frequency response of the model to the frequency response of the real process. Agreement between the simulations and the experimental results was found to be very good. The accuracy of this model was found to be approximately /spl plusmn/0.6 mm, which is considered to be suitable for process control applications.

A real-time prediction model of electrode extension for GMAW

In order to investigate the effect of droplet impact on molten pool dynamics in hybrid laser-MIG (metal inert gas) welding, a three-dimensional mathematical model was developed, and a new approach to simulate the droplet impact was proposed. In the model, the droplet heat and impact under the influence of laser was considered, and the deformation of molten pool was calculated with considering droplet impact and arc pressure. To simplify the model, a modified body heat source model was presented for laser source to take into account multiple reflections and Fresnel absorption. Surface tension, electromagnetic force, and buoyancy were considered to calculate the fluid flow pattern. Furthermore, several dimensionless numbers were used to recognize the importance of the driving forces in molten pool. It was found that molten pool dynamics and final weld bead geometry were strongly affected by the droplet impact. To demonstrate the importance of droplet impact, the temperature, velocity distribution, and the deformation of molten pool were analyzed and compared under different conditions. With considering droplet impact, the penetration was bigger, and the width was smaller. Furthermore, the simulated weld bead geometry was in good agreement with experimental measurement.

Effect of droplet impact on molten pool dynamics in hybrid laser-MIG welding of aluminum alloy

Modeling of MIG/MAG welding with experimental validation using an active contour algorithm applied on high speed movies

This work describes derivation of a control model for electrode melting and heat and mass transfer from the electrode to the work piece in gas metal arc welding (GMAW). Specifically, a model is developed which allows electrode speed and welding speed to be calculated for given values of voltage and torch-to-base metal distance, as a function of the desired heat and mass input to the weldment. Heat input is given on a per unit weld length basis, and mass input is given in terms of transverse cross-sectional area added to the weld bead (termed reinforcement). The relationship to prior work is discussed. The model was demonstrated using a computer-controlled welding machine and a proportional-integral (PI) controller receiving input from a digital filter. The difference between model-calculated welding current and measured current is used as controller feedback. The model is calibrated for use with carbon steel welding wire and base plate with Ar-CO[sub 2] shielding gas. Although the system is intended for application during spray transfer of molten metal from the electrode to the weld pool, satisfactory performance is also achieved during globular and streaming transfer. Data are presented showing steady-state and transient performance, as well as resistance to external disturbances.

A model for heat and mass input control in GMAW

The present study examines the thermal processes occurring in moving electrodes for GMAW with the objectives of 1) determining which phenomena are important in controlling the melting rate and 2) explaining the formation of a tapering tip observed for some combinations of electrode materials and shielding gases

Y S Kim

Papers

Analyses of electrode heat transfer in gas metal arc welding