Welding Sequence Research Articles

Evaluating evolutionary algorithms on spot welding sequence optimization with respect to geometrical variation

Spot welding is the prevalent joining process in the automotive industry. The spot welding sequence has a notable effect on the geometrical variation of the final assembly. Finding the optimal weld sequence for geometrical quality is a fast growing and NP-complete problem. Using exhaustive search for this purpose can be a time-consuming task. In this paper, genetic, particle swarm and ant colony optimization algorithms are applied to three industrial reference cases. The performance of these algorithms for finding the optimal sequence with respect to geometrical variation is compared considering the number of function evaluations.

Incremental magnetic pulse welding of dissimilar sheet metals

Magnetic pulse welding is a solid state welding process using pulsed magnetic fields resulting from a sudden discharge of a capacitor battery through a tool coil in order to cause a high-speed collision of two metallic components, thus producing an impact-welded joint. The joint is formed at room temperature. Consequently, temperature-induced problems are avoided and this technology enables the use of material combinations, which are usually considered to be non-weldable. The extension of the typically linear weld seam can easily reach several hundred millimetres in length, but only a few millimetres in width. If a larger connected area is required, incremental or sequential magnetic pulse welding is a promising alternative. Here, the inductor is moved relative to the joining partners after the first weld sequence and then another welding process is initiated. Thus, the welded area is extended gradually by arranging multiple adjacent weld seams. This paper demonstrates the feasibility of incremental magnetic pulse welding. Furthermore, the influence of important process parameters on the component quality is investigated and evaluated in terms of geometry and micrographic analysis. Moreover, the suitability of different mechanical testing methods is discussed for determining the strength of the individual weld seams.

Aluminium weld fatigue: From characterisation to design rules

In suspension design, traditionally subframes and links are welded structures, with one of the main design criteria being fatigue. Better understanding, correlation and correct design rules are vital to ensure safety and avoid over design that can lead to a reduction in competitiveness.A known mesh modelling T-joint SN method is used to design the welds and is mainly driven from standards used for thicker panels seen in the construction and ship building industry.To consider the thin sheet designs largely seen in automotive, Volvo & nCode have developed a new method based on structural stress and is known to be mesh insensitive. However, new difficulties emerged due to the clear separation between the membrane and bending behaviour needed for stress recovery. Specific tests need to be defined to ensure correct characterisation.Gestamp has generated a new standard of design rules to ensure correlation in Weld-Ends and in Mid-Weld cracks and correct toe position definition to ensure accurate stress recovery, and give more beneficial input to process by better defining the weld torch position. New test specimens have been developed and intensive testing carried out to fully characterise the bending and tension behaviour and reduce the gap in predictions between Lap Weld and Fillet Weld. This methodology has been successfully used in suspension designs with high confidence and correlation.These design rules have been used in conjunction with studying the effect of weld process and sequence on fatigue performance. Controlled distortion subframes, against high distortion subframes, have been tested to capture the benefit by reducing the fit-up gaps. Residual stresses are still a grey zone for Gestamp and further work is needed to better understand the effect.

The effects of welding current and purging gas on mechanical properties and microstructure of tungsten inert gas welded aluminum alloy 5083 H116

Aluminum alloy 5083 H116 has an exceptional performance in extreme environments, moderately high strength, outstanding corrosion resistance in salt water and high impact strength at cryogenic temperature. In the present study, Aluminum alloy AA 5083 H116 plates were joined by tungsten inert gas (TIG) process by single and double sided welding. Welding current used was 53 A and 80 A with the addition of purging gas during welding process. The effects on micro structure and mechanical properties like surface hardness and tensile strength of the welded region were studied. The results have shown that optimum current out of the two weld current used is 53 A. Better microstructures, tensile and hardness were found in the welded joint for the weld current 53 A where the tensile obtained in the softened zone was approximately 87% than that of the base metal (BM). With increasing of TIG current, the width of PMZ increased. In addition, the doubled sided welding sequence also produced broader PMZ area.

An information and simulation framework for increased quality in welded components

The recent trend toward using simulation models with real-time data as digital twins is rapidly increasing in industry. In this paper, a digital framework supporting real-time geometrical quality control of welded components, is presented. The concept is based on a structured process model for all operations included in typical welding, strategies for selective assembly, automatic adjustment of fixtures and optimization of weld sequence. The concept utilizes recently developed algorithms for fast welding simulation and in-line scanning to be used in the optimization loop of an automated welding station—a digital twin for a welding cell.

Fabrication and Qualification Studies of Aluminum Fuel Tank for Experimental UAV

Unmanned Aerial Vehicles (UAVs) are reusable, controllable air vehicle having sustained flight throughout its mission and are widely being utilized for various military and civil applications. Aluminum and its alloys is one of the extensively used non-ferrous metals in aerospace engineering applications due to its excellent properties like higher strength to weight ratio, goodmachinability and excellent formability. However, welding of aluminum and its alloys has always been a challenge due to drastic reduction in strength near heat effected zone. This paper mainly discusses aspects considered in design of pressurized aluminum alloy fuel tank for subsonic Experimental Unmanned Aerial Vehicle (XUAV). The fuel tank is the central module of the fuselage of the aircraft, and is shaped to minimize the stress and minimize sloshing. In the present paper, various weld joints utilized in propellant tank are presented. Also, the welding sequence evolved for fuel tank fabrication, assembly and in-process non-destructive inspections are discussed. Studies were carried out on prototype tank for its qualification namely fuel capacity check, leak test, pressure test, flow rate test etc. The satisfactory result of theoretical and experimental study implies that the fuel tank meets all the design requirements and altitude independence.

용접 잔류응력 최소화를 위한 설계변수 최적화

The objective of this paper is to investigate the influence of welding parameters on residual stress during circumferential welding of pipes. The 3D numerical simulation MSC-Marc code is used to predict the residual stress distribution developed during the welding. When two pipes are welded together, the residual stresses are generated in the vicinity of the weld, attributed to localized heating and subsequent cooling during the welding process. In order to obtain the optimum residual stress, suitable welding parameters are obtained. The influence of the design variables on the residual stress was evaluated using Taguchi method. These results indicate that the best result for welding residual stress can be obtained when the energy input, welding speed, welding sequence, and pipe diameter are 1.6 kW, 3.5 mm/s, sequence (a), and 60 mm, respectively. In general, the optimization parameters are usually chosen according to the specific conditions due to complex residual stress distribution.

Prediction and Welding sequence of Minimum Welding Deformation in Large Steel Block Welding

Prediction and Welding sequence of Minimum Welding Deformation in Large Steel Block Welding

Influences of heat input, welding sequence and external restraint on twisting distortion in an asymmetrical curved stiffened panel

Welding distortion not only degrades the fabrication accuracy of ship hull blocks but also decreases the productivity due to correction works. The accurate prediction of welding-induced distortion will help control the dimension accuracy. In this study, a computational approach based on inherent strain theory and interface element method was employed to efficiently and precisely estimate welding-induced deformation for large welded structures generated during assembly process. In the proposed approach, the local shrinkage due to heat input were considered by inherent strain components. On the other hand, the gap as well misalignment between the two parts to be joined, and the change of stiffness during assembly process were taken into account by interface elements. Meanwhile, the geometrical nonlinearity was included in the developed computational approach. In the current study, the features of welding deformation in an asymmetrical curved stiffened panel were numerically investigated by mean of the new computational approach. In addition, the influences of heat input, welding sequence and external restraint on the twisting distortion of the curved stiffened panel were further studied.

Numerical analysis of welding deformation and residual stress in marine propeller nozzle with hybrid laser-arc girth welds

Deformation and residual stress of the large marine propeller nozzle in hybrid laser-arc girth welding were studied. Welding distortion and residual stress of the basic T-joint were firstly analyzed by thermal-elastic-plastic finite element method and verified by experiment. Combination form of the Gaussian surface heat source model and the conical heat source model was proposed to simulate the thermal flux of laser and arc power at the weld zone. The prediction errors of the width and penetration of the weld profile were respectively 5.26% and 5.89%. For angular distortion, experiment results have a good consistent with simulation results. An obviously gradient of the longitudinal stress and transverse stress was appeared at interface zone of flange and web. An optimal welding sequence was then obtained by analyzing welding deformation and equivalent residual stress. Based on the local-global mapping method, welding deformation of the marine propeller nozzle was further predicted by loading plastic strain sourced from local model.

Analysis of distortion in the welding of ‘X’ and ‘V’ joints in reduced-scale models of segmented rings using continuous monitoring with laser sensors

Distortion in welded components is a permanent change of shape and dimensions from plastic deformations that occur due to thermal stresses developed during the welding process. Due to the high costs to correct the welding distortion, there is great interest from industries to predict, monitor and control these distortions. This paper compares the distortions occurring during welding models of the segmented ring scaled with two types of joints (‘X’ and ‘V’) using the method of monitoring progress of welding distortion with the laser sensors. For continuous monitoring are used laser sensors that are supported on the piece and the beams were projected on a translucent screen placed in front of the same. With the progression of distortion during welding light beams move around the screen in proportion to deformation occurred in the part. The displacements of points of light reflected on the screen are filmed from the opposite side of the bulkhead. The discretization of the film allows to analyze deformations along the welding process and determines the evolution of the distortion in function of time. It was confirmed that the welds performed joints in ‘X’ exhibit distortion values smaller than the joints in ‘V’. The results demonstrate that for the samples used in this experiment at least 60% of the distortion occurred after arc extinction. By experimental testing, it was possible to say that the technique of laser sensors monitoring is viable for use in industry and laboratories of welding, although it is necessary to optimize the data processing obtained by filming, allowing the instantaneous monitoring. The information on the evolution of distortion during welding will be useful to define and monitor more efficiently the best method of control. In addition, it may assist in experimental calibration numerical and computational models, or even to feed back the trajectory of a robot identifying deformations to perform corrections in the welding sequence ensuring also minor distortions.

Experimental Investigation on Flexural Response of Hybrid Steel Plate Girder

Flexural tests were conducted on five full scale I-shaped steel beams, three hybrid and two homogeneous, with two aims: 1) validate the inelastic flexural behavior of hybrid girder that is manufactured using lower grade steel 2) simplify finite element (FE) analysis procedure, for further parametric studies, by neglecting residual stresses when symmetrical welding sequence is adopted. Effect of material properties and member slenderness on flexural strength, ductility, and failure mode shapes is discussed. It is also found that failure mode shape and expansion of plastic field are mainly influenced by slenderness of member. Load-deflection and moment rotation response in tests are closely matching with non-linear finite element study. Close match is also observed in failure mode shapes and plastic field expansion. Considerable reduction is observed in residual stresses in symmetrically welded sections as compared to sections welded without proper sequence. This validates non-linear FE analysis procedure by neglecting residual stresses. Test results are compared with prediction equations for flexural strength, rotation capacity available in literature. Test results are also compared with provisions in EN 1993-1-1 and IS 800. Moment gradient (3-P) and uniform moment (4-P) loading have been considered to ensure that results are equally applicable in both cases.

The Effect of Type of Welding Sequence During Hardfacing Chromium Cast Iron for Erosion Resistance

Abstract The paper presents the capabilities of welding techniques to creating properties of wear resistant high chromium cast iron alloy. The use of the right kind of welding sequence allows you to change the structure and properties of the obtained welds. Tests were conducted for one type of additive material in the form of self shielded core wire. In order to determine the effect of the type of welding sequence on the properties of welds performed welding using string bead and weave bead. The resulting weld was tested on hardness and research structure in an optical microscope. In the following studies have been made erosive tests wear of made hardfacing. String beads gave structure rich in carbides and harder about 270 HV of the weld with weave bead. Also, wear resistance was nearly twice as better for welds made with string beads. In the experiment a decisive role in the resistance to wear plays a high hardness of the deposit and the presence of carbides in its structure. Changes in the basic parameters of the deposition process allows for the formation of structure and properties of hardfacing welds in a wide range.

Using X-Ray Diffraction and Finite Element Method to Analyze Residual Stress of Tube-to-Tubesheet Welded Joints in a Shell and Tube Heat Exchanger

A lot of failures have been generated in the tube-to-tubesheet joints of a shell and tube heat exchanger, which are greatly affected by the weld residual stresses. In order to ensure the structure integrity, it is very important to predict and decrease the residual stress in the joint between tube and tubesheet. In this paper, a combination of X-ray diffraction and finite element method (FEM) was used to analysis the residual stress distribution in the tube-to-tubesheet joints. The formation mechanism of residual stress before and after cosmetic welding was explicated. The effects of heat input and welding sequence on residual stresses were studied. The results show that the large tensile residual stresses which are in excess of yield strength, are generated in the tube-to-tubesheet joints. The residual stresses at the bottom surface and the edge of the tubesheet are relatively small even become compressive. The formation of the weld residual stress is mainly induced by the cosmetic welding rather than the back welding. The residual stresses increase as the heat input increases. The duplex welding method is recommended to decrease the residual stress.

A Study on the Influence of Various Welding Sequence Schemes on the Gain in Strength of Square Hollow Section Steel T-Joint

A Study on the Influence of Various Welding Sequence Schemes on the Gain in Strength of Square Hollow Section Steel T-Joint

<i>In Situ</i> EDXRD Study of MAG-Welding Using LTT Weld Filler Materials under Structural Restraint

Welding using low transformation temperature (LTT) filler materials is an innovative approach to mitigate detrimental welding residual stresses without cost-intensive post weld-treatments [1, 2]. Due to the local generation of compressive residual stresses in the weld line by means of a delayed martensite transformation a significant enhancement of the cold cracking resistance of highly stressed welded components can be expected. For the effective usage of these materials a deeper understanding of the microstructural evolution inside the weld material is necessary to determine the complex processes that cause the residual stress formation during welding. Solid-state phase transformation kinetics and the evolution of strain in LTT weld filler materials are monitored in-situ at the instrument ID15A@ESRF in Grenoble. The transferability to real components is implemented by using a realistic MAG welding process under consideration of structural restraint. During welding of multilayer joints, the phase transformation and phase specific strain evolution of each individual layer is investigated in transmission geometry by means of energy-dispersive X-ray diffraction EDXRD using high energy synchrotron radiation with a counting rate of 2.5 Hz. The measurement results of a 10% Cr / 10% Ni LTT weld filler are compared to data monitored for the conventional weld filler material G89. The in-situ data clearly indicate a strong effect on the local strain evolution and the formation of compressive strain. This results from the restraint volume expansion during the postponed austenite to martensite transformation of the LTT weld filler, which counteracts the thermal shrinkage. In contrast, for the conventional weld filler material the thermal contraction strains lead to tensile residual strain during welding. Furthermore, the results of in-situ observation during welding show that the transformation kinetic is dependent on the welding sequence.

Optimal pass planning for robotic welding of large-dimension joints with nonuniform grooves

Large-dimension welded joints are widely used in shipyards and oilfields. These joints typically have thick and nonuniform welding grooves, thus requiring multi-pass welding processes and tens of hours to complete. Although the development of robotic welding systems can shorten the welding time, it is important to have a detailed plan of the entire process before welding starts. Welding pass planning is crucial for the subsequent robot trajectory generation and provides the welding sequence in a deep groove and the welding parameters of every pass. A knowledge database is used in this research to obtain the relationship between the bead geometry and the welding parameters. A layer-by-layer welding pass planning scheme is proposed to address the nonuniform groove geometry, and an optimization method is proposed with the objective to maximize the section area of the weld bead, so that the number of passes can be minimized. The planning results show that the optimization method is able to provide feasible passes and welding parameters for every pass.

Fatigue Strength Improvement of TIG Welded Joint by Shot Peening Process

Aluminium alloys are widely used in engineering fields because of its characteristics. Components used in the fields of automobile, aerospace such as gears, shafts, turbines. In the mechanical field materials can be joined using many processes like riveting, bolted joints or by using permanent joining techniques like welding, brazing or soldering. The welded joints are often used for structural applications due to the reason that they provide nearly the same strength of the parent material. But researches show that even though they provide good strength in tension, they fail much faster when they exposed to fatigue loading. This may be due to various reasons like improper welding sequence, improper preparation or improper welding parameters of the joint materials. The fatigue life may also get reduced due to stress concentration developed during the welding process. Fatigue failures often results in catastrophic failures. Many designs have been reported, have been occurred due to fatigue failures which resulted in heavy loss of human lifespan and goods. Materials with even higher tensile strength are found to fail at less number of cycles after welding.

Effect of material model on residual stress and distortion in T-joint welding

ABSTRACTWelding-induced residual stress and distortion have detrimental influences on the ultimate strength of ships and offshore structures. Various experimental and numerical studies have been performed to understand the mechanism of residual stress and distortion under different factors, such as boundary condition, welding sequence and so on. In the present study, experimental tests and numerical simulations were performed to investigate the welding-induced residual stress and distortion under different material models. A sequentially coupled thermo-mechanical finite element model which implemented high temperature effects, temperature-dependent material properties and a moving volumetric heat source was developed to investigate the effect of material model on the residual stress and distortion in T-joint welds. The finite element models were validated carefully by the experimental tests. The results show that the material model has significant effects on residual stress and distortion. Considering that the welding process involves substantial plasticity, the material model must be carefully calibrated.

Assessment of HCLL-TBM optimum welding sequence scenario to minimize welding distortions

The ITER HCLL-TBM (Helium Cooled Lithium Lead Test Blanket Module) box assembly development implies the welding development of the following components: the Box and the Stiffening Grid (SG) made of vertical and horizontal Stiffening Plates (noted respectively v-SP and h-SP). This multi-chamber box structure in EUROFER97 steel is made of plates cooled by multiple meandering channels where circulates pressurized helium. For the assembly of these components, characterized by numerous multipass welds, Gas Tungsten Arc Welding (GTAW) is envisaged as reference process. Moreover, the TBM has large dimensions and thin plates which makes it very sensitive to welding distortions and is problematic regarding the assembly feasibility and compliance with geometric tolerances. This paper presents the numerical simulation and experimental work performed to optimize the v-SP to box assembly sequence, which is the most critical assembly regarding distortions, in order to minimize welding distortions.One of the technical lock of this study is high calculation times needed for this large component which implies to set up a simplified welding simulation method. The study is composed of three main phases: an experimental-numerical study of a T-joint fillet mock-up GTAW used to develop the preliminary welding procedure and to validate a simplified simulation method, a numerical optimization of the v-SP to box welding sequence via the simplified method, and the experimental application of the optimized v-SP to Box welding sequence on the TBM mock-up. The calculation and comparison of four different v-SP to box welding sequences allowed to identify the best sequence regarding welding distortions and to apply it experimentally.