Three-dimensional modeling of transport phenomena and their effect on the formation of ripples in gas metal arc welding

Abstract

Distinct, periodic arc-shaped ripples are observed on the surface of the weld bead in almost any welded components which have a significant effect on weld quality. This article presents the complex transport phenomena and their effect on the formation of ripples in three-dimensional moving gas metal arc welding. The transient distributions of the melt flow velocity and temperature in the weld pool, weld pool shape and dynamics, and solidified weld bead are calculated. It is found that the surface ripples are formed by the interplay between the up-and-down weld pool dynamics, caused mainly by the periodic droplet impingements, and the rate of weld pool solidification. The effects of various welding parameters, including the welding current, droplet size, droplet frequency, droplet impinging velocity, and travel speed on the pitch ͑distance between two ripples͒ and height of the ripple are investigated. This study provides fundamental understanding to the underlying physics that cause the formation of ripples with different pitches and heights.

Numerical investigation of weld pool behaviors and ripple formation for a moving GTA welding under pulsed currents

“…(5). The physical meanings of variables in the above equations are expressed elsewhere [7] and will not be repeated here.…”

“…Few of the above models focused on the moving GTAW under pulsed current, especially the weld pool behavior and their effects on the surface rippling. Hu et al [6] and Rao et al [7] developed 3D transient models to study the formation of ripples in the moving GMAW under various welding conditions, but the prediction of ripple formation for pulsed GTAW were not involved. From the above review, it is found that the effects of the welding parameters, such as welding current waveform, pulse frequency and welding speed, on the weld bead formation and surface ripples during pulsed GTAW have not received much attention, and the underlying mechanisms have not been understood well.…”

“…For GTAW, arc plasma exerts a sufficient pressure on the weld pool surface to produce pool oscillations when the arc pressure either fluctuates or is released. For GMAW (gas metal arc welding), in addition to the impact of the arc pressure, the ripple formation is mainly caused by the interplay between the periodic droplet impingements and the weld pool solidification [6,7].…”

“…Up to date, a few studies on the arc welding have been focused on the fundamental understanding of possible mechanisms that lead to the formation of surface ripples [3][4][5][6][7]. It has been found that the formation of ripples is complex and probably involves more than one mechanism, depending on the process variables.…”

Fabrication and Tribological Functions of Microdent Arrays on Ti–6Al–4V Surface by Laser Shock Peening

“…In recent years the study on MP forming and welding of light weight materials has received increased interest, and a series of papers were published by Daehn's group at Ohio State University, among which Tamhane et al [7] studied on sample size effect on the ductility of a ring expansion process, Daehn et al [8,9] 'Corresponding author. reported the improved formability in electromagnetic sheet form ing, Thomas et al [10] reported the forming limit testing and anal ysis on aluminum tube expansion, Fenton and Daehn [11] performed a modeling work on electromagnetic sheet forming, Golowin et al [12] developed a new type of electromagnetic actu ator with uniform pressure, and Zhang et al [13,14] studied on the microstructures at the vicinity of the welded Al-Cu interface using electron backscattering diffraction method (EBSD) and showed that severely deformed and recrystallized fine-grained materials produced near the welded interface.…”