Simulation of Weld Pool Dynamics in the Stationary Pulsed Gas Metal Arc Welding Process and Final Weld Shape

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WELDING RESEARCH
SUPPLEMENT TO THE WELDING JOURNAL, DECEMBER 2006
Sponsored by the American Welding Society and the Welding Research Council

Simulation of Weld Pool Dynamics in the
Stationary Pulsed Gas Metal Arc Welding
Process and Final Weld Shape
A computer simulation accurately predicts weld pool
fluid flow convection and final weld shape
BY M. H. CHO, Y. C. LIM, AND D. F. FARSON

ABSTRACT. The pulsed gas metal arc
welding (GMAW-P) process was modeled
numerically using a code based on the volume of fluid (VOF) technique, chosen primarily for its ability to accurately calculate the shape and motion of free fluid surfaces, which is needed for subsequent study of welding phenomena such as bead

hump formation, incomplete fusion in
narrow groove welds, and weld toe geometry. According to the mathematical models with parameters obtained from analysis of high-speed video images and data acquisition (DAQ) system, GMAW-P was
simulated and then validated by comparison of measured and predicted weld deposit geometry, transient radius, and temperature history. Based on the weld simulation parameters, a parametric study
of weld simulation was performed to
demonstrate and understand the effectiveness of individual simulation parameters on heat and fluid flow in the molten weld pool and the final configuration of
stationary welds. Constricted current density drastically increased the weld penetration and decreased the weld radius, primarily by reducing the convexity of the weld deposit and promoting heat transfer

to the bottom of the weld pool. Conversely, decreased arc force and increased arc pressure radius both decreased the
weld penetration for the same reason.
Based on the understanding of weld pool
M. H. CHO(ch.130@osu.edu) is postdoctoral
researcher, Y. C. Lim (lim.746@osu.edu) is
graduate research associate, and D. F. Farson
(farson.4@osu.edu)is associate professor, Department of Industrial, Welding and Systems Engineering, The Ohio State University, Columbus, Ohio.

spreading, GMAW-P was simulated with
an additional heat source to demonstrate
the utility of the simulation in predicting
final weld shape in complex welding
situations.

Introduction
During arc welding processes such as
gas metal arc welding (GMAW) and gas
tungsten arc welding (GTAW), fluid flow
and heat flow are key factors that determine the final weld shape. Therefore, many previous efforts have been made to
predict these two aspects of arc welding by
numerical simulation. While currently
available welding heat flow and distortion
simulations are quite comprehensive and
accurate enough for many practical purposes, phase change and fluid flow phenomena occurring in arc welding are complex and have still not been realistically simulated. In particular, numerical
model-based prediction of the dynamic
changes in the shape of the liquid weld
pool surface would be useful in many applications if they were possible. Examples include weld toe shape (Ref. 1) and weld
bead hump formation (Ref. 2).
In GMAW, heat input to the weld pool

KEYWORDS
3-D Numerical Simulation
Fluid Flow
Heat Flow
Pulsed GMAW
Volume of Fluid
Weld Shape
Weld Simulation

is composed of a direct arc heat input and
the enthalpy of molten droplets transferring from the welding wire. In numerical weld pool simulations, the current density
is also needed to predict the distribution
of Lorentz force in the weld pool fluid.
These parameters are difficult to measure
for GMAW because of difficulties posed
by filler metal transfer, but measurements
have been made for GTAW. To quantify direct heat and also the electrical current distributions on the weld pool surface, Lu
and Kou (Ref. 3) measured power and
current density distributions using a split
copper block. Based on the analysis by the
Abel inversion method, the shape of
power and current distribution were
found out to be Gaussian density functions, so the arc shape could be...
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