A Study on the Three-Dimensional Analysis of Heat and Fluid Flow in Gas Metal Arc Welding Using Boundary-Fitted Coordinates

1994 ◽  
Vol 116 (1) ◽  
pp. 78-85 ◽  
Author(s):  
J.-W. Kim ◽  
S.-J. Na
Keyword(s):  
Surface Tension ◽  
Fluid Flow ◽  
Weld Pool ◽  
Surface Deformation ◽  
Driving Forces ◽  
Gma Welding ◽  
Gas Metal Arc Welding ◽  
Three Dimensional ◽  
Weld Bead ◽  
Surface Boundary

Computer simulation of three-dimensional heat transfer and fluid flow in gas metal arc (GMA) welding has been studied by considering the three driving forces for weld pool convection, that is the electromagnetic force, the buoyancy force, and the surface tension force at the weld pool surface. Molten surface deformation, particularly in the case of GMA welding, plays a significant part in the actual weld size and should be considered in order to accurately evaluate the weld pool convection. The size and profile of the weld pool are strongly influenced by the volume of molten electrode wire, impinging force of the arc plasma, and surface tension of molten metal. In the numerical simulation, difficulties associated with the irregular shape of the weld bead have been successfully overcome by adopting a boundary-filled coordinate system that eliminates the analytical complexity at the weld pool and bead surface boundary. The method used in this paper has the capacity to determine the weld bead and penetration profile by solving the surface equation and convection equations simultaneously.

Modeling of GMA Weld Pools With Consideration of Droplet Impact

1998 ◽  
Vol 120 (4) ◽  
pp. 313-320 ◽  
Author(s):  
Zhen Ning Cao ◽  
Pingsha Dong
Keyword(s):  
Fluid Flow ◽  
Weld Pool ◽  
Surface Deformation ◽  
Impact Force ◽  
Gma Welding ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Heat Content ◽  
Heat Transfer Process ◽  
Droplet Impact

A three-dimensional weld pool model has been developed to study the fluid flow and heat transfer process during gas metal arc (GMA) welding. Both droplet heat content and impact force were considered in analyzing the effect of droplets on the formation of weld pool. The fluid flow in the weld pool was induced by the presence of surface tension, electromagnetic and buoyancy force. The surface deformation of weld pool was calculated by considering arc pressure and droplet impact force. Computational results under partial and full penetration welding conditions were obtained. The effect of heat flow and fluid flow characteristics on weld pool geometry was discussed, particularly with respect to the presence of droplet heat input and impact force.

Modeling the Transport Phenomena During Hybrid Laser-MIG Welding Process

2003 ◽  
Author(s):  
Z. Zhou ◽  
W. H. Zhang ◽  
H. L. Tsai ◽  
S. P. Marin ◽  
P. C. Wang ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Weld Pool ◽  
Solid Phase ◽  
Three Dimensional ◽  
Welding Process ◽  
Weld Bead ◽  
Mig Welding ◽  
Multiple Reflections ◽  
Computer Animations ◽  
Solidification Processes

Hybrid laser-MIG welding technology has several advantages over laser welding alone or MIG welding alone. These include the possibility of modifying weld bead shape including the elimination of undercut, the change of weld compositions, and the reduction of porosity formation in the weld. Although the hybrid laser-MIG welding method is becoming popular in industry, its development has been based on the trial-and-error procedure. In this paper, mathematical models and the associated numerical techniques were developed to calculate the heat and mass transfer and fluid flow during the laser-MIG welding process. The continuum formulation was used to handle solid phase, liquid phase, and mushy zone during the melting and solidification processes. The volume-of-fluid (VOF) method was employed to handle free surfaces, and the enthalpy method was used for latent heat. The absorption (Inverse Bremsstrahlung and Fresnel absorption) and the thermal radiation by the plasma in the keyhole, and multiple reflections at the keyhole wall were all considered in the models. The transient keyhole dynamics, interactions between droplets and weld pool, and the shape and composition of the solidified weld bead were all predicted for both the pulsed laser-MIG welding and three-dimensional moving laser-MIG welding. Computer animations showing the fluid flow, weld pool dynamics, and the interaction between droplets and weld pool will be shown in the presentation.

Three-Dimensional Modeling of Gas Metal Arc Welding of Aluminum Alloys

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
H. Guo ◽  
J. Hu ◽  
H. L. Tsai
Keyword(s):  
Weld Pool ◽  
Arc Welding ◽  
Gas Metal Arc Welding ◽  
Three Dimensional ◽  
Welding Process ◽  
Weld Bead ◽  
Three Dimensional Modeling ◽  
Dimensional Modeling ◽  
Metal Arc Welding ◽  
Arc Welding Process

A three-dimensional mathematical model and numerical techniques were developed for simulating a moving gas metal arc welding process. The model is used to calculate the transient distributions of temperature and velocity in the weld pool and the dynamic shape of the weld pool for aluminum alloy 6005-T4. Corresponding experiments were conducted and in good agreement with modeling predictions. The existence of a commonly observed cold-weld at the beginning of the weld, ripples at the surface of the weld bead, and crater at the end of the weld were all predicted. The measured microhardness around the weld bead was consistent with the predicted peak temperature and other metallurgical characterizations in the heat-affected zone.

Transport Phenomena and Their Effect on Weld Quality in GMA Welding of Aluminum Alloys

Volume 3 ◽  
2004 ◽  
Author(s):  
H. Guo ◽  
H. L. Tsai ◽  
P. C. Wang
Keyword(s):  
Aluminum Alloys ◽  
Weld Pool ◽  
Gma Welding ◽  
Gas Metal Arc Welding ◽  
Welding Current ◽  
Weld Penetration ◽  
Three Dimensional Model ◽  
End Effects ◽  
Welding Arc ◽  
Micro Cracks

Gas metal arc welding (GMAW) of aluminum alloys has recently become popular in the auto industry to increase fuel efficiency of a vehicle. In many situations, the weld is short (say, less than two inches) and the “end effects” become very critical in determining the strength of the weld. At the beginning stage of the welding, when the metal is still “cold”, which is frequently called cold weld, limited weld penetration occurs. On the other hand, at the ending stage of the welding, a “crater” is formed involving micro-cracks and micro-pores. Both the cold weld and the crater can significantly decrease the strength of the weld and are more severe for aluminum alloys as compared to steels. Hence, there are strong needs to improve the GMAW process in order to reduce or eliminate the aforementioned end effects. In this paper, both mathematical modeling and experiments have been conducted to study the beginning stage, ending stage, as well as the quasi-steady-state stage of GMA welding of aluminum alloys. In the modeling, a three-dimensional model using the volume-of-fluid (VOF) method is employed to handle the free surfaces associated with the impingement of droplets into the weld pool and the weld pool dynamics. Transient weld pool shapes and the distributions of temperature and velocity in the weld pool are calculated. The predicted solidified weld bead shapes, including weld penetration and/or reinforcement, are in agreement with experimental results for welds in the aforementioned three stages. It was found that the thickness of the molten weld pool is smaller and there is no vortex developed, as compared to steel welding. The lack of penetration in cold weld is due to the lack of pre-heating by the welding arc. Three techniques are proposed and validated numerically to improve weld penetration by increasing the energy input at the beginning stage of the welding. The crater formation is caused by rapid solidification of the weld pool when the welding arc is terminated. By reducing welding current and reversing the welding direction before terminating the arc, the weld pool is maintained “hot” for a longer time allowing melt flow to fill-up the crater. This method is validated experimentally and numerically to be able to eliminate the formation of the crater and the associated micro-cracks.

Modeling of Three-Dimensional Gas Metal Arc Welding With Groove

2007 ◽  
Author(s):  
J. Hu ◽  
H. L. Tsai
Keyword(s):  
Weld Pool ◽  
Arc Welding ◽  
Filler Metal ◽  
Gas Metal Arc Welding ◽  
Three Dimensional ◽  
Plasma Arc ◽  
Droplet Impingement ◽  
Sulfur Species ◽  
Metal Arc Welding ◽  
Arc Pressure

This article analyzes the dynamic process of groove filling and the resulting weld pool fluid flow in gas metal arc welding of thick metals with V-groove. Filler droplets carrying mass, momentum, thermal energy, and sulfur species are periodically impinged onto the workpiece. The complex transport phenomena in the weld pool, caused by the combined effect of droplet impingement, gravity, electromagnetic force, surface tension, and plasma arc pressure, were investigated to determine the transient weld pool shape and distributions of velocity, temperature, and sulfur species in the weld pool. It was found that the groove provides a channel which can smooth the flow in the weld pool, leading to poor mixing between the filler metal and the base metal, as compared to the case without a groove.

Arc Behavior Numerical Analysis in GMAW Welding Deposition-Based Rapid Forming

2014 ◽  
Vol 488-489 ◽  
pp. 285-288
Author(s):  
Feng Liang Yin ◽  
Sheng Zhu ◽  
Hong Wei Liu ◽  
Lei Guo
Keyword(s):  
Heat Flux ◽  
Fluid Flow ◽  
Weld Pool ◽  
Numerical Study ◽  
Three Dimensional ◽  
Radial Distance ◽  
Maximum Pressure ◽  
Forming Process ◽  
Arc Behavior ◽  
Gmaw Welding

Metal fluid flow in weld pool would influence final quality of forming part in GMAW welding deposition-based rapid forming process. To numerical study fluid flow in weld pool, heat and force effects on weld pool surface must been made clear firstly. A three-dimensional numerical model has been built to study arc behavior in GMAW welding deposition-based rapid forming process. Solving the model, heat flux and pressure distributions on the cathode were derived. Calculated results show that heat flux from the arc to the cathode is related to arc temperature nearly above the cathode, and is not monotonous about radial distance within 2 mm distance away from arc axis. A maximum pressure with a value of 800 Pa happens at 1mm away from arc axis.

Surface Deformation and Convection in Electrostatically-Positioned Droplets of Immiscible Liquids Under Microgravity

2005 ◽  
Vol 128 (6) ◽  
pp. 520-529 ◽  
Author(s):  
Y. Huo ◽  
B. Q. Li
Keyword(s):  
Surface Tension ◽  
Fluid Flow ◽  
Free Surface ◽  
Electric Field ◽  
Outer Layer ◽  
Thermal Gradient ◽  
Surface Deformation ◽  
Inertia Force ◽  
Weighted Residuals ◽  
Inertia Forces

A numerical study is presented of the free surface deformation and Marangoni convection in immiscible droplets positioned by an electrostatic field and heated by laser beams under microgravity. The boundary element and the weighted residuals methods are applied to iteratively solve for the electric field distribution and for the unknown free surface shapes, while the Galerkin finite element method for the thermal and fluid flow field in both the transient and steady states. Results show that the inner interface demarking the two immiscible fluids in an electrically conducting droplet maintains its sphericity in microgravity. The free surface of the droplet, however, deforms into an oval shape in an electric field, owing to the pulling action of the normal component of the Maxwell stress. The thermal and fluid flow distributions are rather complex in an immiscible droplet, with conduction being the main mechanism for the thermal transport. The non-uniform temperature along the free surface induces the flow in the outer layer, whereas the competition between the interfacial surface tension gradient and the inertia force in the outer layer is responsible for the flows in the inner core and near the immiscible interface. As the droplet cools into an undercooled state, surface radiation causes a reversal of the surface temperature gradients along the free surface, which in turn reverses the surface tension driven flow in the outer layer. The flow near the interfacial region, on the other hand, is driven by a complimentary mechanism between the interfacial and the inertia forces during the time when the thermal gradient on the free surface has been reversed while that on the interface has not yet. After the completion of the interfacial thermal gradient reversal, however, the interfacial flows are largely driven by the inertia forces of the outer layer fluid.

scholarly journals Influence of Arc Power on Keyhole-Induced Porosity in Laser + GMAW Hybrid Welding of Aluminum Alloy: Numerical and Experimental Studies

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1328 ◽  
Author(s):  
Guoxiang Xu ◽  
Pengfei Li ◽  
Lin Li ◽  
Qingxian Hu ◽  
Jie Zhu ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Fluid Flow ◽  
Solidification Rate ◽  
Gas Metal Arc Welding ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Gas Bubble ◽  
Hybrid Welding ◽  
Destructive Testing ◽  
Arc Power

A three-dimensional numerical model is used to simulate heat transfer and fluid flow phenomena in fiber laser + gas metal arc welding (GMAW) hybrid welding of an aluminum alloy, which incorporates three-phase coupling and is able to depict the keyhole dynamic behavior and formation process of the keyhole-induced porosity. The temperature profiles and fluid flow fields for different arc powers are calculated and the percent porosities of weld beads were also examined under different conditions by X-ray non-destructive testing (NDT). The results showed that the computed results were in agreement with the experimental data. For hybrid welding, with raising arc power, the keyhole-induced porosity was reduced. Besides the solidification rate of the molten pool, the melt flow was also closely related to weld porosity. A relatively steady anti-clockwise vortex caused by arc forces tended to force the bubble to float upwards at the high temperature region close to the welding heat source, which benefits the escape of the gas bubble from the melt pool. When increasing the arc power, the anti-clockwise region was strengthened and the risk of the gas bubble for capture by the liquid/solid interface underneath the keyhole tip was diminished, which resulted in the lower weld percent porosity.

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