Welding Sequence Optimization Research Articles

Numerical Simulation Study on Welding Process of Upper Frame of Hydropower Unit

To optimize the welding process of the upper frame of the hydropower unit, a thermal elastic–plastic (TEP) finite element model of the typical T-joint of the upper frame was established, and the effectiveness and accuracy of the model were verified by welding tests. The effect of welding speed and interlayer cooling time on welding residual stress and deformation was analyzed, and a welding process in line with the requirements was obtained. Based on the results of the TEP calculation, the inherent strain was obtained, and the inherent strain method (ISM) was used to predict the overall deformation of the upper frame under three welding sequence schemes, and the optimal welding sequence was obtained.

Digital Twin-Based Clamping Sequence Analysis and Optimization for Improved Geometric Quality

Geometric deviation associated with the assembly of sheet metal is a general concern for manufacturers. The typical assembly step involves a sequence of events that exert forces on the parts to enforce them to the nominal condition and to connect the parts together. The simulation and optimization of the assembly steps often neglect the sequence of operations due to the problem and computation complexity. This paper investigates the influence of the clamping sequence in the body-in-white (BIW) manufacturing process on the geometrical quality of the assembly. An approach for modeling clamping sequences for non-rigid variation simulation is introduced in a digital twin context, taking the part deviation into consideration. An optimization method is proposed to achieve minimum geometric deviation after clamping the parts and welding them together. The method is successfully applied on two reference assemblies, and the results show that the sequence of clamping can impact the total geometric deviation up to 31%. Combining clamping and welding sequence optimization can enhance the quality improvement to 77% after releasing the assembly from the fixture and springback.

Suppressing welding deformation instability of vacuum vessel considering external restraint and welding sequence

The vacuum vessel has a double-layer shell structure with complex ribs and high-density, full-penetration welded joints. Suppression of welding deformation is very critical to the improvement of manufacturing accuracy. In this paper, the welding experiment is studied for a double-layer shell pre-developed part. The welding deformation measured after welding is compared with the simulation results based on the inherent strain theory, which verified the effectiveness of the numerical simulation method. The welding deformation of the vacuum vessel poloidal segment is simulated numerically. The influence of different welding sequences on welding deformation without constraints is analyzed, and the position where large deformation occurs is fixed by multiple constraints to restrain deformation. The influence of several restraint schemes and fixture removal sequences on deformation suppression is compared. The results show that the optimum welding sequence can reduce 13.6 % of the welding deformation, the minimum welding deformation under free conditions is 14.52 mm, and the final deformation is effectively reduced to 3.6 mm by fixed constraints, which can provide technical guidance for engineering manufacturing.

Welding sequence optimization using the strain direct boundary method based on the welding induced change in structural stiffness

Welding sequence optimization using the strain direct boundary method based on the welding induced change in structural stiffness

Prediction and Validation for Welding Deformation of the Upper Port Stub

The vacuum vessel (VV) as an ultrahigh vacuum pressure vessel is one of the essential components of the Chinese Fusion Engineering Test Reactor (CFETR) device. VV has strict position tolerance. The VV port stub is a typical large-scaled welded structure manufactured by electron beam welding (EBW) technique. Welding has the most significant influence on deformation. Therefore, it is essential to analyze welding deformation. A systematic welding simulation method aimed at welding deformation controlling for a large EB welded structure is proposed in this article. First, the dynamic process of EBW of 50-mm-thick ultralow carbon austenitic stainless steel was simulated based on the thermal elastoplastic theory. The weld forming mechanism of high energy density welding of the thick plate was revealed. Then the inherent strain extracted from the results of the simulation of local welding was introduced to the simulation of tailor welding of the port stub. Finally, optimal welding sequence and clamping conditions were obtained, and the reliability of the simulation was verified by the profile measurement results of the inner shell of the upper port stub.

Welding sequence optimization to reduce welding distortion based on coupled artificial neural network and swarm intelligence algorithm

This study aims to develop a welding sequence optimization (WSO) framework based on coupled artificial neural network (ANN) and swarm intelligence algorithm for minimizing welding distortion of thin-walled squared Al–Mg–Si alloy tube components. This framework is mainly composed of two critical computer programs. Firstly, a multilayer feedforward backpropagation neural network (BPNN) system was established to rapidly estimate residual distortion for an arbitrary welding sequence so that welding sequence can be optimized for achieving desired welding quality. For this purpose, a series of nonlinear thermo-elastic–plastic finite element (FE) simulations were conducted and verified with experiments to generate the input database of the neural network. Subsequently, a reliable BPNN model was successfully created and trained within an acceptable error. Secondly, a novel swarm intelligence algorithm, namely, bees algorithm (BA) was proposed to solve the complicated WSO problems. In this optimization process, the trained BPNN model was implanted into this proposed BA for computing the fitness value of arbitrary welding sequences. Moreover, welding experiments were also performed to confirm the performance of the proposed optimization method. Comparing the results from experimental measurements, FE simulations, and proposed WSO framework, it is demonstrated that this proposed BPNN-and-BA-based WSO framework can be successfully applied in practical engineering to obtain an optimal welding sequence for minimizing final welding distortion.

Immune Optimization of Double-Sided Welding Sequence for Medium-Small Assemblies in Ships Based on Inherent Strain Method

The double-sided welding process is widely used in ship construction due to its high welding efficiency and forming quality. In order to further reduce the deformation caused by double-sided welding for medium-small assemblies in ships, the optimization of the double-sided welding sequence based on an artificial immune algorithm is carried out. First, the formation mechanism of welding deformation under the double-sided welding process is analyzed by the inherent strain method; next, the reduction of the welding deformation is taken as the optimization goal, and the welding sequence optimization model for double-sided welding is constructed; then, an immune clonal optimization algorithm based on similar antibody similarity screening and steady-state adjustment is introduced, and the immune optimization process for double-sided welding sequence is designed; finally, double-sided welding sequence optimization tests are carried out for four different types of medium-small assemblies in ships. Numerical test results show that, compared with IGA (Immune genetic algorithm), ICA (Immune clonal algorithm), and GA (Genetic algorithm), the maximum welding deformation caused by the welding sequence optimized by the proposed immune clonal algorithm is reduced by 2.4%, 2.8, and 3.3%, respectively, the average maximum welding deformation is reduced by 2.6%, 2.5, and 3.4%, respectively, and the convergence generation is reduced by 16.2%, 13.4, and 11.2%, respectively, which verifies the strong optimization ability and high optimization efficiency of the immune clonal algorithm introduced in the double-sided welding sequence optimization.

Mathematical modelling of carbon emissions and process parameters optimisation for laser welding cell

Laser welding has been widely employed for aluminum alloy body-in-white. However, owing to the low utilisation efficiency of energy and material, the carbon emission of laser welding is serious. In this paper, the mathematical modelling of carbon emissions and process parameters optimisation for laser welding cells are studied. The carbon emission characteristics of the laser welding system are analysed, and the carbon emission model of the laser welding cell considering both welding features and welding transfers is established. Besides, the process parameters optimisation model of laser welding cell is developed. To obtain optimal welding sequence, a combinatorial algorithm based on Culture Algorithm and Ant Colony Algorithm is proposed. Based on the optimal welding sequence, the optimal transfer speed is obtained through mathematical theory. Furthermore, a case study is performed to verify the feasibility and reliability of the process parameters optimisation model. Additionally, compared with the Ant Colony Algorithm, the proposed solution algorithm has better comprehensive performance in terms of convergence speed and optimisation accuracy. This study lays a theoretical foundation for carbon emission modelling of the laser welding cell, and can support the automobile enterprise to make processing parameters selection of the laser welding line in the design stage.

Immune Optimization of Welding Sequence for Arc Weld Seams in Ship Medium-Small Assemblies

The arc weld seam is a common form in ship medium-small assemblies. In order to reduce the deformation of the welded parts with an arc weld seam, and then improve the welding quality, research on the optimization of welding sequences based on the artificial immune algorithm is carried out in this paper. First, the formation mechanism of welding deformation is analyzed by the thermo-elastic-plastic finite element method; next, the reduction in the welding deformation is taken as the optimization goal, and the welding sequence optimization model for the arc weld seam is constructed under the condition of boundary constraints; then, an immune clonal optimization algorithm based on similar antibody similarity screening and steady-state adjustment is proposed, and its welding sequence optimization ability is improved through antibody screening and median adjustment. Finally, the welding sequence optimization tests are carried out based on the Ansys platform. Numerical tests of a typical arc weld seam show that different welding sequences will cause different welding deformations, which verifies the importance of welding sequence optimization. Furthermore, the numerical test results of four different types of welds in ship medium-small assemblies demonstrated that the use of distributed optimization algorithms for welding sequence optimization can help reduce the amount of welding deformations, and the immune clonal algorithm, based on antibody similarity screening and steady-state adjustment, achieves the optimal combination of the welding sequence. Compared with the other three optimization algorithms, the maximum welding deformation caused by the welding sequence optimized by the proposed immune clonal algorithm is reduced by 3.1%, 4.0%, and 3.4%, respectively, the average maximum welding deformation is reduced by 3.5%, 5.5%, and 4.7%, respectively, and the convergence generation of the optimization algorithm is reduced by 16.8%, 13.1% and 14.5%, respectively, which further verifies the effectiveness and superiority of the proposed immune clonal algorithm in the optimization of welding sequences.

A Study on Minimizing Welding Deformation of Joints for the Sealing of Emission After-Treatment Structure.

As the environmental pollution issue has recently become significant, environmental regulations in Europe and the United States are being strengthened. Thus, there is a demand for the quality improvement of emission after-treatment systems to satisfy the strengthened environmental regulations. Reducing the amount of welding heat distortion by optimization of the welding order of each part could be a solution for quality improvement since the emission after-treatment system consists of many parts and each assembly is produced by welding individual ones. In this research, a method to derive a welding sequence that effectively minimizes welding deformation was proposed. A two-stage simulation was performed to obtain the optimal welding sequence. In the first stage, the welding sequence was derived by analyzing the number of welding groups in each assembly of a structure. The derived welding sequence was verified by performing a thermal elasto-plastic analysis and comparing it with the experimental results.

FEM Research on Welding Thermal Deformation of Copper Alloy Sheet and Optimization of Welding Sequence

To reduce the residual stress and deformation of the copper alloy sheet after welding, and improve the welding quality of the copper alloy sheet, the finite element method (FEM) research on welding thermal deformation and welding sequence optimization was carried out. First, a finite element model of copper alloy sheet welding was established based on ANSYS, the mechanical property parameters of the model at high temperature were determined, and the thermal–structural coupling calculation was performed on the model. Then, the change trend and magnitude of the residual stress and deformation of the model after welding were analyzed. Finally, different welding sequence schemes were designed, and numerical simulation calculations were carried out. The results of the welding sequence solution show that the change trend of the residual stress after welding of the base metal under different welding sequences is basically the same; repeated heating of the base metal at the same position causes large residual stress; the weldment vertical plate is subjected to opposing forces in the x-axis and y-axis directions at the same time. Among four welding schemes, the welding scheme that alternately welds symmetrically from the start and end positions of the weld seam to the middle position of the plate causes the least welding deformation. Compared with the other three schemes, its deformation reduces by 26.6%, 18.3%, and 19.4%, respectively.

Influence of welding sequence on the mechanical properties of a latticed shell formed by orthogonal and oblique members

With the development of economy and the improvement of people’s aesthetic level, large-span latticed shells are increasingly used. Such structures are commonly large in volume and huge in welding. In order to select an optimum welding sequence and avoid correcting complex welding deformation, a latticed shell formed by orthogonal and oblique members was taken as the research object in this paper. The finite element models of single and whole latticed shells were established respectively, and according to the equal deformation principle, the influence of different welding sequence on the deformation and internal force of the structure in each construction stage was quantitatively analyzed. The results show that in the welding and assembling stage of small assembling units in the single latticed shell, welding sequence has the greatest impact on the longitudinal deformation, and the change rate of the longitudinal deformation is up to 83.63%; whereas in the tension, sliding and closure stages of each piece of the latticed shell, the transverse deformation is most affected by welding sequence, and the change rate is 33.05%; in different construction stages, the axial stress of the latticed shell is less vulnerable to welding sequence. Furthermore, it is feasible to control the welding shrinkage deformation by selecting a reasonable welding sequence, and the symmetrical welding sequence from both ends to the middle should be adopted during construction.

Recent Advances in the Prediction of Weld Residual Stress and Distortion - Part 2

Weld residual stress can contribute to the reduction of structure lifetime and accelerate the formation of fatigue cracks, brittle fractures, or stress corrosion cracking. Distortion can have a significant impact on the dimensional ac-curacy of assembly, structure strength, and fabrication cost. In the past two decades, there have been many significant and exciting developments in the prediction and mitigation of weld residual stress and distortion. This paper reviews the recent advances in mitigation techniques that have been applied in the structure design, manufacturing, and postweld stages. The techniques used in the structure design stage include selecting the type of weld joint and weld groove, using balanced welding, determining appropriate plate thickness and stiffener spacing, and considering distortion compensation. Mitigation techniques used in the manufacturing stage include welding sequence optimization, reducing welding heating input, selecting low-transformation-temperature filler metals, prebending, precambering, constraints, trailing and stationary cooling, in-processing rolling, transient thermal tensioning, and additional heat sources. Postweld mitigation techniques include postweld heating and mechanical treatment. Finally, the remaining challenges and new development needs were discussed to guide future development in the field of mitigating weld residual stress and distortion.

Efficient Spot Welding Sequence Simulation in Compliant Variation Simulation

Abstract Geometrical variation is one of the sources of quality issues in a product. Spot welding is an operation that impacts the final geometrical variation of a sheet metal assembly considerably. Evaluating the outcome of the assembly, considering the existing geometrical variation between the components, can be achieved using the method of influence coefficients (MICs), based on the finite element method (FEM). The sequence with which the spot welding operation is performed influences the final geometrical deformations of the assembly. Finding the optimal sequence that results in the minimum geometrical deformation is a combinatorial problem that is experimentally and computationally expensive. Traditionally, spot welding sequence optimization strategies have been to simulate the geometrical variation of the spot-welded assembly after the assembly has been positioned in an inspection fixture. In this approach, the calculation of deformation after springback is one of the most time-consuming steps. In this paper, a method is proposed where the springback calculation in the inspection fixture is bypassed during the sequence evaluation. The results show a significant correlation between the proposed method of weld relative displacements evaluation in the assembly fixture and the assembly deformation in the inspection fixture. Evaluating the relative weld displacement makes each assembly simulation less time-consuming, and thereby, sequence optimization time can be reduced by up to 30%, compared to the traditional approach.

INFLUENCE OF TACK WELDS DISTRIBUTION AND WELDING SEQUENCE ON THE ANGULAR DISTORTION OF TIG WELDED JOINT

In this paper the influence of tack welds distribution and welding sequence on angular distortion of the Tungsten Inert Gas (TIG) welded joint was tested. Additionally, the effect of welding current on angular distortion was assessed. For research X2CrTiNb18 (AISI 441) stainless steel (2.5 mm thick) was chosen. During research specimens were prepared with different distributions of tack welds. Then they were welded by different welding sequences with the use of different welding current values. After welding the angular distortion of each specimen was measured by using the coordinate measuring machine. In the next step specimens were cut. Cross-sections were polished and the metallographic macroscopic testing was conducted to check the geometry of performed welds. Performed experiments allowed determining the optimal tack weld sequence and welding parameters for welding thin stainless steel sheets.

Numerical Optimization of the Welding Sequence for Mitigating Welding Deformation in Aluminum Pipe Structures by Using a Genetic Algorithm

Aluminum is widely used in fields that require lightweight technology, such as in the aerospace and automobile industries. The welding of aluminum alloys, however, tends to generate large deformations in the welded structures due to its large heat conductivity and thermal expansion. Therefore, this study aims to reduce welding deformations that occur in the welding process by obtaining an optimal welding sequence. The welding sequence optimization process consists of two main stages. The first involves the prediction of the welding deformation behavior by using thermo-elastic-plastic finite element analysis. The second stage optimizes the welding sequence by using a genetic algorithm (GA), which can efficiently optimize very large solution spaces considering not only the welding sequence, but also the welding direction. In addition, this study proposed an appropriate and efficient GA for the present optimization problem. The optimization results showed that the developed finite element analysis model were in good agreement with the experimental results, and the proposed optimization tool can reduce the welding deformation considerably.

Effective thermal elastic plastic finite element computation for welding distortion investigation of pozidriv-type welded structure with rectangular pipes and its mitigation

Welding distortion of pozidriv-type welded structure with rectangular pipes by 20 welding passes was examined with experimental and computational approaches, and mitigation techniques were also investigated for precision fabrication. Welding experiment to fabricate pozidriv type welded structure was conducted beforehand, and out-of-plane welding distortion was measured with contact type displacement sensor. Effective thermal elastic plastic finite element computation with iterative substructure method and parallel computation was developed, and then employed to examine the thermal-mechanical response during the entire welding process and predict the residual out-of-plane welding distortion. Good agreement between computed results and measurement data was observed with comparison. The influences of welding sequence and clamping constraint with tack welding on welding distortion were considered, which were also practiced for out-of-plane welding distortion mitigation. Both experiment and finite element computation show that out-of-plane welding distortion with welding sequence optimization and clamping constraint can be significantly reduced with about 38% and 56% magnitude of original welding distortion, respectively, while their mechanisms were also clarified by means of stiffness variation of solving welded structure.

Numerical Prediction of Welding Distortion Considering Gravity Force on General Ship Grillage Structure by Elastic Finite Element Method Using Inherent Strain

The accurate numerical prediction of welding deformation is important to improve the structural safety of ships and offshore structures in heavy industries. The precise reflection of the real working condition in the numerical prediction is an essential factor to improve its result. In the present study, the effect of the gravity force on numerical prediction of the optimal welding sequence of a general ship grillage structure was validated with the introduction of a new boundary condition in which the structure is placed over rails. Additionally, the direction of the gravity force of welded structures could be changed at the final assembly process according to the production plan. The effect of the gravitational orientation on the final welding displacements was also investigated herein. The elastic finite element method using the inherent strain, interface element, and multipoint constraint function was introduced to analyze the welding deformation. This study validated the influence of the gravity force on the numerical prediction of welding displacements in a general ship grillage structure.

Parameter analysis and optimization of welding sequence for the aluminium alloy sidewall in a high-speed train body

The sidewall is the most complex structure and welding process part in the aluminum alloy train body, and its welding deformation is greatly influenced by welding sequence parameters. In this paper, the relationship between the welding residual stress and welding deformation of the sidewall and welding sequence parameters is studied, and the optimal welding sequence is determined. Using a verified finite element model of one intercepted sidewall, the relationships between the welding residual stress and welding deformation of the sidewall and the welding of welds, welding sequences of welds and the weld sequence are studied, respectively. Some conclusions can be drawn from the analysis results. One is that the welding results at one weld are only determined by self-welding, and have nothing to do with other welds, and welding results outside one weld are affected by welds on both sides. The second is that for a single weld, the from-one-end-to-the-other welding sequence is best, and the identical welding sequence is best for each weld. The third is that the fixed welds are firstly welded and a cross weld sequence is best.

Rapid sequence optimization of spot welds for improved geometrical quality using a novel stepwise algorithm

ABSTRACT Joining sequence optimization is a combinatorial problem, requiring extensive computational time. The significance of determination of an optimal sequence for improved geometrical quality is substantial. Previously, genetic algorithms have been studied for defining the optimal sequence. However, these algorithms are highly dependent on the internal parameters, requiring additional computational analysis and thereby extended evaluation time. In this article, a novel robust stepwise algorithm is introduced to determine the optimal weld sequence. Application of the proposed algorithm leads to drastic time improvements for defining the optimal weld sequence of each assembly. Three industrial assemblies are evaluated. Comparison with the previously applied population-based optimization algorithms indicates that the optimization time can be reduced drastically with the proposed stepwise algorithm. The stepwise algorithm is intended to be applied in a geometry assurance digital twin, where the assembly parameters are being optimized for each individual assembly.