Welding sequences optimization of box structure based on genetic algorithm method

In this article, The genetic algorithm method was proposed, that is, to establish the box structure＇s nonlinear three-dimension optimization numerical model based on thermo-mechanical coupling algorithm, and the objective function of welding distortion has been utilized to determine an optimum welding sequence by optimization simulation. The validity of genetic algorithm method combining with the thermo-mechanical nonlinear finite element model is verified by comparison with the experimental data where available. By choosing the appropriate objective function for the considered case, an optimum weldiing.sequence is determined by a genetic algorithm. All done in this study indicates that the new method presented in this article will have important practical application for designing the welding technical parameters in the future.

Effect of welding sequence on residual stress in thin-walled octagonal pipe-plate structure

A three-dimensional finite element approach based on ABAQUS code was developed to investigate the effect of welding sequence on welding residual stress distribution in a thin-walled 6061 aluminum alloy structure. To obtain sound numerical results, the therrno-mechanical behaviour was simulated using a direct-coupled formulation. Nine different simulation sequences were carried out by single-pass TIG welding of an octagonal pipe-plate joint, and the distributions of longitudinal and transverse residual stresses both on the outer and inner surfaces of the pipe were analyzed. The results suggest that the final residual stresses in the weld and its vicinity are not affected by the initial residual stresses of the structure. Selecting a suitable welding sequence can reduce the final residual stress in an octagonal pipe-plate joint.

Effect of welding sequence on residual stress and deformation of 6061-T6 aluminium alloy automobile component

Four different welding sequences of double-pulse MIG welding were conducted for 6061-T6 aluminum alloy automobile bumpers by using nonlinear elastoplasticity finite element method based on ABAQUS software.The post-welding residual stress and deformation were definitely different among the four welding sequences.The results showed that the highest temperature in Solution A was approximately 200℃higher than the melting point of base metal.High residual stress was resulted from this large temperature gradient and mainly concentrated on the welding vicinity between beam and crash box.The welding deformation primarily occurred in both of the contraction of two-ends of the beam and the self-contraction of crash box.Compared with other welding sequences,the residual stress in Solution A was the smallest,whereas the welding deformation was the largest.However,the optimal sequence was Solution B because of the effective reduction of residual stress and good assembly requirements.

Effects of welding parameters and welding sequence on residual stress and distortion in Al6061-T6 aluminum alloy for T-shaped welded joint

The distribution of temperature and then the distribution of residual stress and distortion in the stiffened aluminum alloy Al6061-T6 plates under the metal inert gas(MIG)welding process were investigated by three dimensional thermo-mechanical coupled finite element model using Ansys software.The properties of materials were considered temperature-dependent and the filler metal was added to the workpiece by the element birth and death technique.In three modes of current,two different speeds and two various sequences,the distribution of residual stress and distortion were calculated and analyzed.The results showed that increase in welding speed decreased the vertical deflection in the plate,transverse shrinkage and angular distortion of plate and the lateral deflection of stiffener,but increased the maximum longitudinal tensile stress in the plate and stiffener.Furthermore,increase in current increased the residual stress and deformation in the plate and stiffener,and the change in the welding sequence changed the distribution of the distortion in the plate and the stiffener without significant change in the distribution of the longitudinal residual stress.

Prediction of welding distortion during assembly process of thin plate structures

Ships and automobiles are fabricated front thin plates. To assemble parts, welding is commonly employed. However, welding distortion in large thin-plate panel structure is usually cased by buckling due to the residual stress. In this study, an elastic finite element method for predicting the welding distortion of three-dimensional thin-plate structures with considering welding sequence was proposed. In this method, the inherent strain was employed to model the local shrinkage due to welding itself, and the interface element was introduced to simulate the assembly process. The proposed method was applied to study the influence of welding sequence on the buckling distortion of the large thin-plate panel structure during assembly.

Study on welding deformation of the side beam based on numerical simulation method

The welding deformation is a key factor affecting the production quality of the side beam of the subway bogie frame. A major issue is how to control the welding deformation during the manufacturing processes. Based on the ＂Local- Global＂ method, the thermal cycle and the stress of a local model extracted from the global side beam model were simulated. The simulated strain result was mapped into the global model as an initial load to simulate the welding assembly deformation. Then the deformation distribution of the side beam was obtained by elastic finite element method, and compared with the measurement results. Furthermore, the welding deformation under different welding sequences and constraints was simulated. The influence of the welding sequences and constraints on the side beam deformation was analyzed. The results indicate that the deformation is the smallest when the sequence is symmetrical and decreases with the increase in constraints.

Multi-objective optimization of gas metal arc welding parameters and sequences for low-carbon steel (Q345D) T-joints

Q345D high-quality low-carbon steel has been extensively employed in structures with stringent weld- ing quality requirements. A multi-objective optimization of welding stress and deformation was presented to design reasonable values of gas metal arc welding parameters and sequences of Q345D T-joints. The optimized factors included continuous variables （welding current （I）, welding voltage （U） ahd welding speed （V）） and discrete variables （welding sequence （S） and welding direc- tion （D））. The concepts of the pointer and stack in Visual Basic （VB） and the interpolation method were introduced to optimize the variables. The optimization objectives included the different combina- tions of the angular distortion and transverse welding stress along the transverse and longitudinal dis- tributions. Based on the design of experiments （DOE） and the polynomial regression （PR） model, the finite element （FE） results of the T-joint were used to establish the mathematical models. The Pareto front and the compromise solutions were obtained by using a multi-objective particle swarm optimization （MOPSO） algorithm. The optimal results were validated by the corresponding results of the FE method, and the error between the FE results and the two-objective results as well as that be-tween the FE results and the three-objective optimization results were less than 17.2% and 21.5%, respectively. The influence and setting regularity of different factors were discussed according to the compromise solutions.