Role of Welding Parameters in Determining the Geometrical Appearance of Weld Pool

1996 ◽  
Vol 118 (4) ◽  
pp. 589-596 ◽  
Author(s):  
R. Kovacevic ◽  
Z. N. Cao ◽  
Y. M. Zhang
Keyword(s):  
Fluid Flow ◽  
Weld Pool ◽  
Numerical Models ◽  
Three Dimensional ◽  
Welding Current ◽  
Gta Welding ◽  
Welding Parameters ◽  
Geometrical Shape ◽  
Arc Length ◽  
Weld Pools

A three-dimensional numerical model is developed to describe the fluid flow and heat transfer in weld pools. Both full penetration and free deformation of the top and bottom weld pool surfaces are considered. Temperature distribution and fluid flow field are obtained. In order to analyze the influence of welding parameters on the geometrical appearance of weld pools, a normalized model is developed to characterize the geometrical appearance of weld pools. It is found that welding current can significantly affect the geometrical shape. When welding current increases, the curvature of the pool boundary at the trailing end increases. The effect of the welding speed on the geometrical appearance is slight, although its influence on the pool size is great. In the interest range of arc length (from 1 mm to 4 mm), the arc length can affect both the size and the shape of the weld pool. However, compared with the welding current and speed, its influences are much weaker. GTA welding experiments are performed to verify the validity of the numerical models. The appearance of weld pools was obtained by using machine vision and a high-shutter speed camera. It is found that the calculated results have a good agreement with the experimental ones.

Numerical Analysis of Fully Penetrated Weld Pools in Gas Tungsten Arc Welding

1996 ◽  
Vol 210 (2) ◽  
pp. 187-195 ◽  
Author(s):  
Y M Zhang ◽  
Z N Cao ◽  
R Kovacevic
Keyword(s):  
Free Surface ◽  
Weld Pool ◽  
Driving Forces ◽  
Numerical Models ◽  
Surface Tension Gradient ◽  
Bottom Surface ◽  
Welding Parameters ◽  
Back Side ◽  
Full Penetration ◽  
Weld Pools

Full penetration welding is widely used in metal joining, but it has been ignored in previous convective numerical models. In addition to the free surface on top of the pool, an additional free surface appears on the bottom of the workpiece. It can be shown that the top surface, temperature distribution and fluid flow field in the weld pool are all coupled with the pool's bottom surface. This complicates the numerical process and therefore no convective models have previously been developed for fully penetrated weld pools. In order to improve the numerical solution for the fully penetrated weld pool, a three-dimensional model is proposed. Free top and bottom pool surfaces have been included. The electromagnetic force, buoyancy force and surface tension gradient (Marangoni) are the three driving forces for weld pool convection. Welding parameters are changed in order to analyse their effects on weld pool geometry. It is found that the depression of the top surface contains abundant information about the full penetration state as specified by the back-side bead width.

Numerical Dynamic Analysis of Moving GTA Weld Pool

1998 ◽  
Vol 120 (1) ◽  
pp. 173-178 ◽  
Author(s):  
Z. N. Cao ◽  
Y. M. Zhang ◽  
R. Kovacevic
Keyword(s):  
Weld Pool ◽  
Plate Thickness ◽  
Three Dimensional ◽  
Calculated Data ◽  
Welding Process ◽  
Welding Current ◽  
Three Dimensional Model ◽  
Full Penetration ◽  
Weld Pools ◽  
Describe Heat Transfer

A three dimensional model with a moving heat source is developed to describe heat transfer and fluid flow in transient weld pools. Full penetration and free top and bottom surfaces are incorporated in the model in order to simulate the welding process more practically. The influence of plate thickness and welding current on the dynamics of weld pools is analyzed using calculated data. It is shown that when the workpiece is nearly penetrated, the depth of weld pool increases quickly. Also, the elevation of the top surface decreases quickly once the full penetration status is established.

Experimental Study and Modeling of GTA Welding Process

2003 ◽  
Vol 125 (4) ◽  
pp. 801-808 ◽  
Author(s):  
Min Jou
Keyword(s):  
Experimental Study ◽  
Weld Pool ◽  
Welding Speed ◽  
Welding Current ◽  
Distribution Parameter ◽  
Welding Parameters ◽  
Heat Distribution ◽  
Arc Length ◽  
Experimental Calibration ◽  
Current Voltage

It has been well recognized that the geometry of weld pool plays a fundamental role in determining the mechanical properties of weld joints. In this research, a series of experiment has been conducted to investigate the interaction and correlation of welding current, voltage, welding speed, and arc length affecting the formation of weld pool. The effect of arc length on arc efficiency and heat distribution parameter are also examined and addressed in this paper. In addition to the experimental study, a three-dimensional finite element model has been developed to analyze transient heat flow and to predict the formation of the weld pool. The correlation among the parameters including welding current, voltage, welding speed, arc length, open-loop response and the characteristic geometry of weld pool are established. The 3-D FEM can calculate not only the transient thermal histories but also the sizes of weld pool in single-pass arc welding. In order to obtain quality welds, this model will determine the effect of arc length on the formation of weld. Furthermore, the effects of welding parameters on the Gaussian heat source parameters (arc efficiency and heat distribution parameter) are also studied. The experimental calibration and verification are carried out to verify the numerical model. Experimental data are consistent and in quantitative agreement with values from FEM simulations.

A Study on Parameter Optimization for Circumferential Gas Tungsten Arc (GTA) Welding of Small Pipes considering Backing Gas Pressure: Part 1: Analysis of Weld Pool Surface Profile

1996 ◽  
Vol 210 (1) ◽  
pp. 77-85 ◽  
Author(s):  
S-J Na ◽  
T-J Lho
Keyword(s):  
Temperature Distribution ◽  
Finite Difference ◽  
Weld Pool ◽  
Surface Profile ◽  
Welding Current ◽  
Gta Welding ◽  
Welding Parameters ◽  
Difference Model ◽  
Gas Tungsten Arc ◽  
Pool Surface

It is well known that the weld bead becomes wider and the weld pool hangs down as the circumferential welding of small-diameter pipes progresses, if constant welding conditions are maintained over the entire joint length and/or no appropriate backing gas is supplied into the pipe. In order to obtain a weld bead which is uniform in width and does not hang down over the whole circumference of the pipe, the welding parameters such as welding current, welding velocity and backing gas pressure should be optimized as the welding progresses. In order to optimize the welding parameters, a mathematical model for determining the temperature distribution in the pipe workpiece and the surface profile of the resultant weld pool is indispensable. An efficient finite difference model was adopted for calculating the three-dimensional transient temperature distribution in circumferential gas tungsten arc (GTA) welding of pipes. Its solution was obtained by employing the alternating direction implicit (ADI) finite difference method, in which a periodic boundary condition and a periodic cubic spline function were used. For calculating the weld pool surface profiles in full penetration circumferential welding of pipes, a governing equation was derived in the cylindrical coordinate and solved using a simple finite difference model with the ADI scheme. In Part 2 of this paper, an efficient parameter optimization method is used to evaluate the optimal welding current for a required bead width when the welding velocity is given.

Nonaxisymmetric Convection in Stationary Gas Tungsten Arc Weld Pools

1997 ◽  
Vol 119 (1) ◽  
pp. 164-172 ◽  
Author(s):  
Y. Joshi ◽  
P. Dutta ◽  
P. E. Schupp ◽  
D. Espinosa
Keyword(s):  
Computational Study ◽  
Numerical Models ◽  
Three Dimensional ◽  
Pulsed Laser ◽  
Surface Flow ◽  
Rotational Flow ◽  
Visualization System ◽  
Gas Tungsten Arc ◽  
Laser Visualization ◽  
Weld Pools

Observations of surface flow patterns of steel and aluminum GTAW pools have been made using a pulsed laser visualization system. The weld pool convection is found to be three-dimensional, with the azimuthal circulation depending on the location of the clamp with respect to the torch. Oscillation of steel pools and undulating motion in aluminum weld pools are also observed even with steady process parameters. Current axisymmetric numerical models are unable to explain such phenomena. A three-dimensional computational study is carried out in this study to explain the rotational flow in aluminum weld pools.

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.

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.

scholarly journals Fluid Flow Characteristics and Weld Formation Quality in Gas Tungsten Arc Welding of a Thick-Sheet Aluminum Alloy Structure by Varying Welding Position

2018 ◽  
Vol 8 (8) ◽  
pp. 1215 ◽  
Author(s):  
Baohua Chang ◽  
Hong Xiao ◽  
Jinle Zeng ◽  
Shuo Yang ◽  
Dong Du ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Molten Metal ◽  
Weld Pool ◽  
Flow Characteristics ◽  
Sheet Thickness ◽  
Thick Sheet ◽  
Weld Formation ◽  
Sheet Aluminum ◽  
Weld Pools ◽  
Welding Position

This study aims to reveal the cause of different weld formation quality for varying welding position in the GTAW (Gas Tungsten Arc Welding) of a thick-sheet aluminum alloy structure. The fluid flow characteristics of weld pools are investigated by CFD (Computational Fluid Dynamic) modeling and high-speed imaging for the climbing and flat welding positions, which correspond to the start and finish ends of the welds of the structure, respectively. Results show that the directions of gravity relative to weld pools may notably affect the fluid flows in weld pools for different welding positions. For flat welding, gravity will accelerate the fluid flow in the direction of sheet thickness only and in turn result in a high velocity downwards, which implies a good penetrating capability. Welds of good formation with smooth surface and consistent width can be produced under flat welding position. In contrast, for climbing welding, gravity will act on the molten metal in both the direction of sheet thickness and the lateral direction of the weld pool. As a result, the velocity in sheet-thickness direction is decreased, which implies a decreased penetrating capability. Meanwhile, the velocity backwards is increased in the top portion of the weld pool, which makes the molten metal apt to flow out of the weld pool. Both the decreased penetrating capability and the accelerated molten metal outflow would render the climbing welding process unstable, and result in welds of poor formation with uneven weld surface and inconsistent weld width. Based on the study, possible methods are proposed that could be used to improve the weld formation quality when welding thick-sheet aluminum alloys structures using various welding positions.

The Behaviour of Nitrogen on the Welding Parameters of the Dissimilar Weld Joints between AISI 304 and AISI 316L Austenitic Stainless Steels Produced by Gas Tungsten Arc Welding

2012 ◽  
Vol 248 ◽  
pp. 395-401 ◽  
Author(s):  
Wichan Chuaiphan ◽  
Loeshpahn Srijaroenpramong
Keyword(s):  
Weld Metal ◽  
Nitrogen Content ◽  
Welding Current ◽  
Welding Parameters ◽  
Aisi 316L ◽  
Arc Length ◽  
Aisi 304 ◽  
Dissimilar Weld ◽  
Weld Metals ◽  
Welding Arc

The behavior of nitrogen into the dissimilar joining metal between AISI 304 and AISI 316L Austenitic stainless steel during gas tungsten are welding process was investigated. Studied by using an arc nitrogen atmosphere – controlling in chamber. The relations between nitrogen content of the dissimilar weld metal and the welding parameters, such as the welding current, welding speed, welding arc length and penetration area of weld metals were also evaluated. The results show that the nitrogen content of the weld metals decreased with an increasing welding current, and increasing penetration areas of weld metal, but scarcely depends on the welding arc length. The nitrogen content of the weld metals increased with the welding speed, but decreased penetration areas of weld metals. The role of nitrogen content on the dissimilar weld metals stainless steel is further confirmed by the experimental microstructure, mechanical and corrosion behaviour of the weld metal.

scholarly journals Three-Dimensional Hydromechanical Modeling during Shearing by Nonuniform Crust Movement

Geofluids ◽  
2017 ◽  
Vol 2017 ◽  
pp. 1-14 ◽  
Author(s):  
Yuqing Zhao ◽  
You-Kuan Zhang ◽  
Xiuyu Liang
Keyword(s):  
Fluid Flow ◽  
Pore Pressure ◽  
Fault Zone ◽  
Numerical Models ◽  
Three Dimensional ◽  
Practical Investigations ◽  
Geological Formation ◽  
Distribution Of Stress ◽  
Coupling Processes ◽  
Fluid Interaction

Hydromechanical modeling of a geological formation under shearing by the nonuniform crust movement during 10000 years was carried out to investigate the solid stress and pore pressure coupling processes of the formation from the intact to the fractured or faulted. Two three-dimensional numerical models were built and velocities in opposite directions were applied on the boundaries to produce the shearing due to the nonuniform crust movement. The results show that the stress and pore pressure became more and more concentrated in and around the middle of the formation as time progresses. In Model I with no fault, stress and pore pressure are concentrated in the middle of the model during shearing; however, in Model II with a fault zone of weakened mechanical properties, they are more complex and concentrated along the sides of the fault zone and the magnitudes decreased. The distribution of stress determines pore pressure which in turn controls fluid flow. Fluid flow occurs in the middle in Model I but along the sides of the fault zone in Model II. The results of this study improve our understanding of the rock-fluid interaction processes affected by crustal movement and may guide practical investigations in geological formations.

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