In the present study, temperature fields and residual stress states in the weld joint of the stainless steel pipe are computed numerically using a thermo-elastic-plastic analysis. This weld joint is a circumferential butt-weld one and is done in two passes using gas tungsten arc welding. Welding procedure is simulated in two and three dimensions using a subroutine developed in finite element ABAQUS software for applying heat flux. Furthermore, the element birth and death technique is used to simulate weld passes and filler metal deposition into the weld pool. When the simulation is done, the effect of welding sequence on welding residual stresses are considered using four different welding sequences proposed. Finally, the effect of hydrotest process in decreasing the residual stresses is evaluated. The results of the simulation show that selecting a suitable welding sequence can substantially decrease the amount of tensile residual stresses and can change them to compressive stresses in certain situations. Also the results of this research show that applying a hydrotest pressure after welding process can reduce welding residual stresses up to 65%.

Accurately predicting welding residual stresses and developing a convenient welding sequence for a weld system is an appropriate task since welding residual stress is inevitably produced in a welded structure. In this work, the effect of layered, block and cascade welding sequences on the thermo-mechanical response of shell weldments is studied by use of a 3-D thermo-viscoplastic model. An Anand model is used to simulate the rate dependent plastic deformation of welded materials. At the same time, modeling of the welded region in the present study has been done on the basis of the "isothermal melting pool" approach. The temperature dependency of the thermal and mechanical properties of materials is considered in the analysis and the effect of the welding speed and welding lag, and the inter-pass temperature is introduced into the model as well. Thus, the model presented here has provided a convenient welding sequence to enhance the fabrication process of a circular weld.

Preheating treatment and employing a proper welding sequence are introduced as two efficient approaches for reducing residual stresses in welding processes. Selecting a right welding sequence and a proper preheating temperature for a weld system are crucial tasks, since welding residual stresses are inevitably produced in a welded structure. However, obtaining residual stresses is very complex, and much time is needed in some cases, particularly for the modeling and prediction of residual stresses in welded structures. So in this work, we attempt to show that these stresses depend on generated entropy during the arc welding process. Thus by obtaining thermal irreversibility effects from temperature distribution, due to a variation of different welding parameters, selection of optimum factors to achieve minimum residual stress is not only possible, but easier to undertake. In the proposed method, it is not a necessity to obtain residual stress values, and one can predict the behavior of residual stress qualitatively. To do so, 3D numerical models are employed to study the similar behavior of created residual stresses and entropy due to a variation of different preheating temperatures and three common welding sequences.

Increasingly, Welding is used in industry for assembled various products, such as ships, cars, trains and bridges. Welding distortion often results such as lack of accuracy during assembly and will have increases manufacturing costs. So, predict and reduce welding distortion is very important to improve the quality of welded structures.  In this study, firstly, a prediction method of welding distortion, which merges thermo-elastic-plastic finite element method (FEM) and large deformation elastic FEM based on inherent strain theory, was developed. Secondly, the inherent deformations of weld joints in a large thin plate panel structure were calculated using the thermo-elastic-plastic FEM and their specifications were also examined. Then, using the obtained inherent deformations, the usefulness of the proposed elastic FEM was demonstrated through the prediction of welding distortion in the large thin plate panel structures. Finally, the influences of welding sequence on distortion were investigated. The results of elastic analysis shows distortion in edges and interior parts of the panels, that can be reduced by changing welding sequence to symmetrical welding sequence.

Studies on welding process of Aluminium weldments shows that post-weld residual stress and deformation are influential on structure efficiency and there are different variable which affect these stresses and deformation. In this study the effect of geometrical variables and welding sequence on residual stresses and deformation in Aluminium H321 have investigated by the finite element software Ansys. Thermo elastic-plastic model was verified by metallography experiment and measurement of post-weld deformation afterward, weld leg, penetration depth and welding sequence were optimized to minimize the distortion. It was concluded that weld-volume increase post-weld distortion and it can be minimize by choosing an appropriate weld sequence.

In this research, opening welding on an aluminum shell and investigating the effect of welding sequence on residual stresses and distortion after welding by finite element simulation have been investigated. Then, the results are compared in ABAQUS and SYSWELD.Using experimental data, simulation and experimental results are compared. The temperature distribution is not uniform in different area of the welding zone, the most important factor in this incident is the non-uniform welding geometry. Thermal retransmission and the difference between thermal pick in different situations increases with increase of welding steps, which will affect the development of residual stresses as well as distortion after welding. The peak of the residual stresses is reduced and more uniform distribution occurs as the number of welding sequences increases.. The results show that the higher the distortion in the weld region (the elongation), the greater the amount of elongation. Also, the amount of elongation will be greater, with the higher the distortion in the weld area.

In this paper, the effect of welding sequence on the magnitude and shape of distortion in ship hull structure is investigated. The simulation consists of sequentially coupled thermal and mechanical analyses using an element birth and death technique to model the addition of welding metal to the work piece. Thermal distribution in steel ship hull structures welded by gas metal arc welding is investigated using 3D finite element method (FEM) in ANSYS commercial code. A macro code programmed based on Goldak model is developed to apply thermal loading generated by the heat sources. The analyses are planned to be performed for 3D, transient and nonlinear conditions. In continue to exact investigation the effect of welding sequence on the magnitude and shape of distortion in ship hull structure, evaluation of the results are drawn on lines. Finally, it clearly found significant features of distortion, where not only the magnitude but also the deformed shape of welding distortion is obviously different.

In the present study, the effects of the length, thickness, welding current, welding sequence, holding time in the fixture and similarity of the base metals on welding residual distortion of dissimilar joint between carbon steel CK4 and stainless steel AISI409 were firstly investigated on the basis of a verified finite element model. Then, considering the welding current, fixing time and sequence of welding operation, the magnitude of welding residual distortion was minimized. The results showed that in the studied dissimilar joint, the minimum distortion occurred when the welding current was about 95A; fixing time was 120 sec and symmetric layout was used.

Welding is one of the most important production methods in marine vehicle. Otherwise in welding process while the welding metal is heated or cooled temperature tension around the welding metal cause internal forces which is a factor of bending, bulking and rotating in the parts. This change or displacement is known as distortion. In order to solve the distortion problem of welding peaces three discussion is developed. The first is optimization of the welding and production method for prevention of distortion. The second one an acceptable distortion tolerance is predefined and used in design. The Third one is repairing the produced distortion. One of the best methods in solving the problems of bending in long truss welding in marine vehicle is prevention of creating distortion by using a suitable welding sequence. In this research in order to reduce the bending of aluminum truss welding with 4 meter length, three different procedure is investigated and after testing on the prototype the best method is chosen. And the original peace is welded with the minimum distortion. The research result reveals that the best method for solving the problem of bending truss is preventing the distortion creation. Resolving the distortion in these cases is too difficult and in some cases improbable. Otherwise in order to prevent the distortion the best method is suitable welding sequence identification.

In this paper, experimental of residual stress and distortion generated when welding a and numerical studies were carried out to investigate the welding effects on the buckling behavior of aluminum cylindrical shells under external hydrostatic pressure. The cylindrical shell that is made of AL 5083 was tested under hydrostatic pressure before and after it was welded. Also, the numerical study was done by finite element software code "ABAQUS". Moreover, numerical simulation based on finite element modeling was used to study the influence of welding sequences on the distribution cylindrical shell. The simulation consisted of sequentially coupled thermal and structural analyses. sequences on the d numerical results were adopted.