In WELDING process, stresses after cooling, which remain in body, are called RESIDUAL stresses. Sometimes, the magnitude of stresses is high and reduces the strength of welded pieces, moreover, they cause crack in the weld. To predict WELDING RESIDUAL stresses, it is necessary to do thermal and mechanical analysis.In this paper, some parameters which influence the WELDING using ANSYS software are investigated. Results show that even by decreasing the travel speed of torch, it makes no differences in the amount of RESIDUAL stresses, but preheating causes decreasing the produced stresses about 22 percentages. Suitable WELDING sequences also, decreases RESIDUAL stresses up to 25 percentages.

One major disadvantage of many arc WELDING processes is WELDING-induced RESIDUAL stresses and DISTORTIONS. The non-uniform heating and cooling during arc WELDING result in non-uniform expansion and contraction of the weld and surrounding base material, which produces undesirable RESIDUAL stresses and deformations in the welded joint. A number of methods can be used to control WELDING-induced DISTORTIONS. The methods used for controlling WELDING DISTORTIONS affect RESIDUAL stresses and vice versa. One practical method for minimizing WELDING angular DISTORTIONS is the use of clamping. In this paper, the effect of clamping and clamp releasing time on WELDING RESIDUAL stresses and DISTORTIONS in the single-pass butt WELDING of 304 stainless steel plates are investigated. Cases with and without clamping have been studied, and RESIDUAL stresses and angular DISTORTIONS have been predicted by three-dimensional finite element simulation. Moreover, experiments have been carried out to measure temperature histories, angular DISTORTIONS and RESIDUAL stresses for the unclamped case to verify the numerical model. The results of this study revealed that clamping and clamp release time have a great inuence on the distribution of RESIDUAL stresses and final angular DISTORTIONS. Using clamping during WELDING and releasing after cooling to ambient temperature can significantly reduce the amount of final angular DISTORTIONS.

In this study, the effect of WELDING parameters on the RESIDUAL stresses of resistance spot WELDING of AZ31 magnesium alloy was investigated. Resistance spot WELDING is a complicated multi-regime phenomenon which simulated by a developed electro-thermo-mechanical coupled finite element model. Interactions of parameters were determined using DOE method. The FE model was used to predict temperature changes, nugget growth, and the RESIDUAL stresses distribution. The results of the simulation were validated with experimental data, based on the nugget diameter. The results showed that by increasing current and WELDING time the RESIDUAL stresses are reduced. Increasing electrode force causes to increase RESIDUAL stress but increasing holding time creates a peak in the amount of RESIDUAL stresses. Also, evaluation of current sources revealed, in the same conditions, using direct current creates less RESIDUAL stress than alternating current.

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%.

In this investigation, the thermal and RESIDUAL stresess distributions developed during the circumferential butt tungsten arc WELDING (GTAW) of Incoloy 800H pipes were simulated using the finite element method. A coupled thermostructural model was developed in three dimensions using ANSYS software. A subroutine based on the Goldak model was added to the model to simulate the distribution of arc heat source. The plastic behaviour of the material was described by Von-Mises yield function and the bilinear kinematics hardening in the mechanical part of the model, which is sequentially coupled with the thermal one. In order to validate the coupled model, temperature distributions during WELDING and RESIDUAL stresses distributions in the welded pipes were both measured using thermocouples and hole drilling method, respectively. Using this model, a process parameter study was performed for the process variables such as WELDING efficiency and the amount of heat input in each pass.The results showed a tension-compression distribution of the axial stresses through thickness from inside to outside surface of the pipe and a tensile distribution for the hoop stresses. Increasing the heat input by 36% increased the axial RESIDUAL stresses along the weld centerline on the inner surface of pipe to 11%. The present simulation model is able to predict distributions of temperature and RESIDUAL stresses during the GTAW process with a reasonable precision.

The effect of WELDING RESIDUAL stresses that was created in thin infill plate of steel plate shear wall system during constructional processes was studied in this research. RESIDUAL stresses in a welded structure is the result of the non-uniform expansion and contraction and plastic deformation of the weld and surrounding base metal due to heating and cooling cycle, during WELDING process, this issue could affected SPSW`s behavior. In this research ABAQUS finite element software is utilized to simulation of WELDING process and steel plate shear wall behavior. Sequentially coupled thermo-elastic–plastic finite element computational procedure is developed to calculate temperature field and WELDING RESIDUAL stresses in SPSW. The result shows that RESIDUAL stresses created in infill plates of three story steel plate shear wall with rigid beam-column connection due to WELDING process makes yielding load, ultimate load, stiffness, ductility and energy absorption, decrease 1.4%, 1.26%, 7.6%, 7.3%, 3.4% respectively in model with RESIDUAL stresses in comparison with model without RESIDUAL stresses. Thus, the ignore of RESIDUAL stresses effect due to WELDING in prospect of thin steel plate shear walls (SPSWs) behavior is negligible.

In this paper, thermo-mechanical behavior of the WELDING process was analyzed to determine the effect of edge preparation on the RESIDUAL stress magnitude and distribution in dissimilar joints. By using a verified finite element model, an efficient user subroutine was developed to consider the effects of phase transformation. In order to verify the model, experimental data for similar and dissimilar joints, obtained by deep hole drilling method, were utilized. Good agreement was observed between the finite element and experimental data. The results indicated that the developed computational method is an effective tool to predict the RESIDUAL stress of dissimilar weld joints. The present finite element model was developed in a butt-welded pipe to consider the effect of pipe wall-thickness, groove shape and root opening distance. It was observed that the pipe wall-thickness has important influences on the distribution and magnitude of RESIDUAL stress. Moreover, By increasing the pipe thickness in the dissimilar butt-welded pipes, tensile axial RESIDUAL stresses on the inner surface of the dissimilar joint decreased on the stainless steel side, but only a small variation was observed on the carbon steel side.The compressive axial RESIDUAL stresses on the inner surface and the tensile axial RESIDUAL stresses on the outer surface increased by increasing the pipe wall thickness, especially on the carbon steel side.Increasing the weld groove shape and root opening distance leads to higher compressive axial stresses on the inner surface and higher tensile axial stresses on the outer surface, only on the carbon steel side.

In electric arc WELDING, the heat generated by the arc causes non-uniform expansion and contraction in the weld and surrounding areas. Uneven expansion and contraction and the resulting plastic deformation are the main sources of RESIDUAL distortion and stress in welded structures. The distribution of RESIDUAL stresses in a welded joint depends on factors such as heat input, arc WELDING speed, material properties, preheating, part thickness, groove geometry and WELDING execution schedule. In this research, a head to head joint is investigated by penetration WELDING with experimental methods and finite element simulation. RESIDUAL stresses are measured by the central hole drilling method and by converting the obtained data into RESIDUAL stresses, the obtained results are used to verify the developed finite element model. In the finite element model, the non-coupled thermal-mechanical mode is used and the method of birth and death of the elements is used in the simulation of filler materials. In the simulation, the phase transformation process is considered and with the help of LTT filler introduced, the RESIDUAL stresses in the single-pass WELDING show a 15% reduction and in the two-pass WELDING show a 17% reduction in the tensile RESIDUAL stresses. By examining the effect of the arrangement and composition of the passes and the type of WELDING fillers, it was found that the combination of LTT electrode with 6010 electrode provides more favorable results for RESIDUAL stresses. Regarding the effect of thickness change in the cross section of the samples, the output of the results of both numerical analysis software does not show significant changes.

In this paper, a suitable method is presented to predicate fatigue crack propagation for cyclic loading with overload in RESIDUAL stresses field resulted by weld. For this, first effective stress intensity factor (SIF) and effective cycle ratio (R) are introduced as function depending on SIFs resulted by external load, weld RESIDUAL stress and overload. Weight function is applied to calculate SIF resulted by weld RESIDUAL stress. Also, a method is introduced to determine overload SIF and overload stress ratio. Then fatigue crack propagation equation is modified for our purpose. In other words, a simple and efficient method is presented in this paper for predicting fatigue crack propagation rate in welded joints when the overload is happening. Finally, for evaluating this modified equation, experimental methods are applied. Test samples were M(T) geometry made of aluminum alloy with a longitudinal weld by the Gas Tungsten arc WELDING process. Modified equation has a good agreement with the experimental model presented in this field.