Browsing by Author "Egerland, Stephan"

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    Arc instabilities during split anode calorimetry with the TIG welding process
    (Springer, 2018-03-29) Egerland, Stephan; Colegrove, Paul A.; Williams, Stewart W.
    Split anode calorimetry investigations of tungsten inert gas (TIG) arcs were conducted using a large-diameter shielding gas nozzle. Some conditions displayed arc symmetry whilst others proved distinctly asymmetric. The variation of welding current and electrode tip to workpiece distance (ETWD) was studied. Decreasing the ETWD was found to increase the current density towards the arc axis but similar to a previous study of the authors, Gaussian distributions were not observed. The gas nozzle was designed to produce laminar gas flow and sound shielding behaviour; however, anode surface oxidation was found after welding, presumably caused by shielding gas contaminated with oxygen through the welding sequence. Therefore, axial arc symmetry was influenced by random effects. The conditions and reasons for the observed phenomena are explored within this paper.
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    Influence of shielding gas nozzle design on power density distribution in low-current TIG welding arcs
    (Springer, 2020-03-17) Egerland, Stephan; Colegrove, Paul; Williams, Stewart
    Shielding gas nozzle diameter variation and its impact on the anodic power distribution of low-current tungsten inert gas arcs were investigated, while maintaining either shielding gas flow rate or flow velocity constant. In addition, the effects of anode surface condition and flow behaviour type (laminar or turbulent) caused by the shielding gas nozzle applied were studied. It was found that arcs of 50 amperes (A) welding current were highly unstable deploying the conditions used, while increasing the arc electrical current to 100 A led to improved arc stability. As found in previous investigations, non-Gaussian distribution profiles occurred at 50 A, even with improved shielding. The power density maxima were found shifted away from the arc axis
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    Investigation of low current gas tungsten arc welding using split anode calorimetry
    (Taylor and Francis, 2016-05-27) Egerland, Stephan; Colegrove, Paul A.; Williams, Stewart W.
    Most previous split anode calorimetry research has applied high weld currents which exhibit pseudo Gaussian distributions of arc current and power density. In this paper we investigate low current arcs and show that both the current and power distributions have minima in the centre – varying significantly from the expected Gaussian profile. This was postulated due to the formation of the arc with the copper anode and the tungsten cathode. Furthermore, a number of parameters were varied including the step size between measurements, anode thickness and anode surface condition as well as cathode type and tip geometry. The step size between measurements significantly influenced the distribution profile and the anode thickness needed to be above 7 mm to obtain consistent results.
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    Measuring the process efficiency of controlled gas metal arc welding processes
    (2011-07-31T00:00:00Z) Pepe, Nuno; Egerland, Stephan; Colegrove, Paul A.; Yapp, David; Leonhartsberger, Andreas; Scotti, Ameirico
    The thermal or process efficiency in gas metal arc welding (GMAW) is a crucial input to numerical models of the process and requires the use of an accurate welding calorimeter. In this paper, the authors compare a liquid nitrogen calorimeter with an insulated box calorimeter for measuring the process efficiency of Fronius cold metal transfer, Lincoln surface tension transfer and RapidArc, Kemppi FastRoot and standard pulsed GMAW. All of the controlled dip transfer processes had a process efficiency of ∼85% when measured with the liquid nitrogen calorimeter. This value was slightly higher when welding in a groove and slightly lower for the RapidArc and pulsed GMAW. The efficiency measured with the insulated box calorimeter was slightly lower, but it had the advantage of a much smaller random erro