Sharif Digital Repository

A 2-D numerical model was developed to predict the shape of weld pool in stationary GTA welding of commercial pure aluminium, without considering fluid flow in the weld pool. A Gaussian current density and heat input distribution on the surface of the workpiece were considered. The parameters of Gaussian distribution were modified by comparing calculated results with experimental ones. It was found that these distribution parameters are functions of applied current and arc length. Effects of arc length, applied current and welding time on the geometry of the weld pool were investigated. To check the validity of the model, a series of experiments were also conducted. In general, the agreement... 

In this work, a three-dimensional model has been proposed to predict temperature distribution and weld-pool shape during dissimilar arc welding of low-carbon steel (CK4) and ferritic stainless steel (AISI 409). The model has been developed using the finite-element software ANSYS, while in the analysis, the effects of process parameters, as well as dilution, in the weld pool have been considered. To verify the predictions, welding experiments were conducted under different welding conditions, and the model results were then compared with the measured weld-pool geometry; a reasonable consistency was observed  

In this work, temperature field and weld pool geometry during gas tungsten arc welding of 304 stainless steel are predicted by solving the governing equations of heat transfer and fluid flow under quasi-steady state conditions. The model is based on numerical solution of the equations of conservation of mass, momentum, and energy in the weld pool. Weld pool geometry, weld thermal cycles, and various solidification parameters are then calculated by means of the model predictions. The model considers the effects of various process parameters including welding speed and heat input. It is found that the weld pool geometry, predicted by the proposed model, is in reasonable agreement with the... 

In the present study, the temperature and the velocity fields during gas tungsten arc welding of commercial pure aluminum were simulated using the solution of the equations of conversation of mass, energy and momentum in three dimensions and under steady-state heat transfer and fluid flow conditions. Then, by means of the prediction of temperature and velocity distributions, the weld pool geometry, weld thermal cycles and various solidification parameters were calculated. To verify the modeling results, welding experiments were conducted on two samples with different thicknesses and the geometry of the weld pool was measured. It is found that there is a good agreement between the predicted... 

A mathematical model is developed to assess the solidification behaviour of the weld pools. To do so, during gas tungsten arc welding of commercial pure aluminium, equations of conversation of mass, energy and momentum are numerically solved considering three-dimensional steady state heat transfer and fluid flow conditions. The weld pool geometry, weld thermal cycles and various solidification parameters are calculated using temperature and velocity fields acquiring from the utilised model. The solidification behaviour of the weld pool at the weld centreline and the fusion line is then studied using the solidification parameters including temperature gradient G, solidification rate R and the... 

This study concentrates on the effects of weld sequence and welding fixtures on distribution and magnitude of induced arc welding residual stresses built up in butt-joint of Gas Tungsten Arc Welding (GTAW) AA5251 plates. Aluminum plates have been welded under different welding conditions and then, longitudinal and transverse residual stresses were measured in different points of the welded plates employing hole-drilling technique. The results indicate that welding sequence significantly alters the distributions of both longitudinal and transverse residual stresses while the changing in the weld sequence leads to 44% decrease in longitudinal residual stress. Besides, both the geometry of weld... 

In this paper, a thermo-mechanical model has been used to predict the temperature history and residual stress distribution in gas tungsten arc welding of AA5251 plates. This model has also been utilized to estimate the residual stresses under different welding sequences, while in the model the effect of temperature on material properties were taken into account. In order to verify the predictions, residual stresses within the welded samples and weld pool geometry were experimentally measured employing hole drilling and macro-examination of weld cross-section, respectively. The comparison between numerical and experimental data shows a reasonable agreement. The predictions show that the... 

The purpose of this work is to assess the effect of welding fixtures on distributions and values of residual stresses during Gas Tungsten Arc Welding (GTAW). The butt-joint GTAW of AA5251 plate is investigated using a transient thermo-mechanical analysis performed by the finite element program, ABAQUS. The model considers two different welding conditions including unconstrained and perfectly constrained conditions while macro examination and residual stress measurements by implementing hole drilling techniques are utilized to evaluate the predictions. The results show that the utilizing of a welding fixture alters the temperature field within the plate being welded and the depth of the weld... 

Since the mechanical properties and the integrity of the weld metal depend on the solidification behaviour and the resulting microstructural characteristics, understanding weld pool solidification is of importance to engineers and scientists. Thermal and fluid flow conditions affect the weld pool geometry and solidification parameters. During solidification of the weld pool, a columnar grain structure develops in the weld metal. Prediction of the formation of the microstructure during welding may be an important and supporting factor for technology optimization. Nowadays, increasing computing power allows direct simulations of the dendritic and cell morphology of columnar grains in the...