Synchronous Welding Research Articles

The effect of cryogenic applications on tensile strength of aluminum 2219-T87 T-joint welded by dual laser-beam bilateral synchronous welding

2219 aluminum alloy has been widely used in aerospace industry due to its high specific strength, excellent weldability as well as outstanding ductility. The dual laser-beam bilateral synchronous welding (DLBSW) technology is employed in the joining of 2219-T87 aluminum alloy skin-stringer structure in T-joint. In order to establish the tensile strength of T-joints at room and cryogenic temperatures, the tensile testing is carried out. The microstructure of weld seam is observed for exploring the relationship between the grain size and tensile strength. In addition, the fracture morphology is observed by scanning electron microscope (SEM). The elemental analysis of fractured surface is done by energy dispersive spectrometer (EDS) and is used to study the effect of chemical element composition on tensile strength. The results show that the highest tensile strength of 360.01 MPa was achieved when the tensile test obtained at room temperature while the joint welded by same parameter exhibit a much higher tensile strength of 422 MPa when tested at cryogenic temperature. According to the results of microstructure analysis, grain size reduction was observed when the joint was exposed to cryogenic temperature. From the fracture morphology of joints, it was found that dimples of the sample tested at cryogenic temperature are bigger and deeper than that at room temperature. The results of EDS show that the amount of the Al2Cu increases at 77 K which causes an increase in tensile strength.

The effect of temperature alternating load on residual stresses for Al-Li alloy T-joints welded by dual laser beam bilateral synchronous welding

The finite element (FE) simulation is employed to predict the residual stresses, which is induced by the welding and the temperature alternating load. The simulation of 5A90 Al-Li alloy T-joint welded by the dual laser beam bilateral synchronous welding (DLBSW) is carried out. Then the evolution of the residual stresses is obtained under the temperature alternating load which is achieved by changing the ambient temperature on T-joint. In addition, the accuracy of simulation model has been verified by comparing the experimental results with the simulation results. According to the comparison, the simulation results are consistent with the experimental results, which shows that the residual stresses of 5A90 T-joints decrease under the temperature alternating load. Besides, the FE simulation is a relatively efficient and accurate method to predict the change of residual stresses under the temperature alternating load.

Ways to improve welding operations in construction of oil product storage tanks

It is shown that in order to further increase the welding rate in the construction of oil product storage tanks, fi rst of all it is necessary to develop and implement high-performance methods for double-sided arc welding of vertical joints. It is noted that the most useful technique to increase the welding rate and the quality of vertical joints on the side walls of the tanks is to replace single-arc automatic welding with multi-arc welding in gas-shielded or gas mixtures. Whereby the method exhibiting the most promise for is the double-sided synchronous welding. In this case, two arcs on the both sides of the workpiece are involved in the weld formation. It is determined that for the formation of technical requirements for the welding process and needed welding equipment, and for their implementation in multi-arc welding of vertical joints, it is necessary to conduct comprehensive study of multiparameter relationship between the double-electrode welding modes and the quality of the welded joints in the construction of oil product storage tanks based on physical and mathematical modeling.

Study on the formation mechanism of fine equiaxed grain ribbons along the fusion lines during 2060/2099 Al-Li alloys dual laser-beam synchronous welding process

The dual laser-beam synchronous welding (DLBSW) technology is newly developed in order to improve productivity and weld seam quality. In this investigation, AA2060 and AA2099 Al-Li alloys were welded using ER4047 welding wire under different heat input in DLBSW process. The microstructure characteristics especially the fine equiaxed grain ribbons along the fusion lines of T-joints were investigated by observing the micro morphology both in cross section and vertical section. It was found that the non-dendritic equiaxed grain near the fusion line was spherical in three dimensional with small size compared with the equiaxed grain in the weld seam center. Besides, the action of thermal buoyancy flow and Marangoni convection was found to have great effect on the formation of fine equiaxed grain ribbons in the molten pool. Moreover, the energy dispersive spectrometer (EDS) results of non-dendritic equiaxed zone (EQZ) indicated that the strip-shaped intergranular precipitation phase in EQZ is rich in Cu, while the bulk-shaped intergranular precipitation phase is rich in Si.

Influence of Laser Power on Grain Size and Tensile Strength of 5A90 Al–Li Alloy T-joint Fabricated by Dual Laser-Beam Bilateral Synchronous Welding

Dual laser-beam bilateral synchronous welding is introduced to produce the 2.5 mm thick 5A90 Al–Li alloy T-joint. The grain morphology and grain size of weld metal (WM) in the T-joint are analyzed and calculated. The tensile experiment, scanning electron microscopy and energy disperse spectroscopy are respectively employed to study the tensile strength, fracture morphology and chemical composition of the T-joint. The results reveal that when the laser power is increased from 2500 to 3000 W, the grain sizes of fine-grained layers and columnar dendrites near the fusion line are significantly reduced. Conversely, that of equiaxed dendrites at the WM center is not sensitive to the variety of laser power. Moreover, the degree of elemental segregation in WM near the fusion line is also aggravated with the increasing of the laser power. The tensile strength of the T-joint with the laser power of 2500 W is significantly higher than that with the laser power of 3000 W. The tensile fracture locations are occurred in the weld toe with obvious pores, shear dimples and tear ridges, which are the typical characteristics of ductile fracture. Besides, the chemical compositions of the second phase particles in the WM are more sensitive to than the variation of laser power compared with that of the matrix.

Effect of welding parameters on porosity distribution of dual laser beam bilateral synchronous welding in 2219 aluminum alloy T-joint

The dual laser beam bilateral synchronous welding (DLBSW) for T-joint is limited to develop for the porosity defect in joint. In order to investigate the effect of porosity in T-joint, the DLBSW experiment of 2219 Aluminum Alloy T-joint is carried out. While, the distribution of porosity is scanned by X-ray non-destructive testing (NDT) and the size of porosity is measured by particle size analysis software Nano measurer 1.2. The morphology of pore in fracture and the elemental concentration around the pore are investigated by scanning electron microscopy (SEM) and energy spectrometer (EDS). Furthermore, the analysis results of porosity distribution show that the optimal parameter is 3700 W of laser power and 2.5 m/min of welding rate, under which the number of porosities reaches the minimum. The main factor, caused the fracture of weld seam, is the concentrated porosities in T-joint. In addition, technical porosity is mainly found in the center of the weld seam or at the bottom of the weld seam, and it can be eliminated by improving welding parameters. Metallurgical porosity mainly exists at the edge and the top of the weld seam, including hydrogen porosity and metal vapor porosity which formed by the burning of metal elements.

FE analysis of the residual stresses for the laser welded T-joint of Al-Li alloy under service loads

This paper attempts to reveal the evolution of welding residual stresses (WRS) in skin-stringer structure of Al-Li alloy exposed to service loads. 3D thermal-structural finite element (FE) formulation of the dual laser-beam bilateral synchronous welding process is first derived, and its accuracy is verified by experimental tests to acquire accurate WRS. FE numerical analyses incorporated with the elastic-plastic constitutive model, taking the WRS, strains distribution and total equivalent plastic strains as an initial condition, are next carried out to explore the residual stresses redistribution of the T-joint under service loads. The results unveil that longitudinal stress relaxation is pronounced (especially at the weld) in the skin after the end of the loads applying. However, the longitudinal stress in the middle of the stringer is not sensitive to the service loads. The extended high tensile stress concentration zone inside the joint in case 2 and case 4 may be the potential failure location after the progressive loading of the skin-stringer welding structure. Additionally, the weld toe, which is the obvious stress sudden change zone in the service process, is a non-negligible position for the improved failure estimation of the aerospace skin-stringer structure.

Research on the stripping performance during dual laser-beam bilateral synchronous welding of 2219 aluminum alloy T-joint for spacecraft

The promising dual laser-beam bilateral synchronous welding (DLBSW) technology was employed in the 2219 aluminum alloy T-joint which consisted of the skin and stringer components. The coherent weld seam (WS) is achieved under the heat affect of dual laser beam. The stripping experiment was carried out to test the stripping strength of DLBSW joint. With the purpose of discussing the relationship between the welding shape and stripping strength, H1 was measured to evaluate the shape of welded T-joint. The microstructure characteristics of T-joint were observed to discuss the crack location during striping experiment. Besides, the fracture morphology was observed by scanning electron microscope (SEM). The chemical element composition on the impure phase in the fracture was detected by energy dispersive spectrometer (EDS). The highest stripping strength is 317.46 MPa with the laser power of 5500 W and welding speed of 4.2 m/min. The stripping crack locations are mainly divided into three categories. The highest stripping strength is achieved under the second category of crack location which is taken place near the upper fusion line. It is indirectly found that the strength of WS in case 6 with the laser power of 5500 W is highest than the others. The degrading of stripping strength is mainly owing to the reducing of plasticity as well as the formation of internal defects such as pores, bonded structure and nubby impure phases. The nubby impure phase is mainly metal oxides (TiO2, Al2O3) which generally degrade the weld quality. It is notable that a new skin component accompanied with two bosses is firstly designed in the present study to replace the wire filler.

Study on 2219 aluminum alloy T-joint during dual laser-beam bilateral synchronous welding : Effect of the welding speed and incident beam angle on grain morphology

The 2219 aluminum alloy T-joints consisting of 4 mm thick stringer and 3.5 mm thick skin with preset double bosses were fabricated by dual laser-beam bilateral synchronous welding (DLBSW) in this investigation. The effect of the welding speed and the incident beam angle on the grain morphology including grain size on one-dimensional (1D) and two-dimensional (2D) scales were studied in detail. The microstructure of different regions of T-joint were identified using optical microscopy (OM). The width of non-dendritic equiaxed zone (EQZ) and the columnar dendrites grain size Zl were measured and quantitatively studied on 1D scale, while the grain size Zs of EQZ and the equiaxed dendrites on 2D scale. The results show that the grain morphology of different regions of the T-joint is significantly different due to the difference of welding heat input and cooling rate. The grain size Zs of EQZ and equiaxed dendrites crystal zone increase as the welding speed increase, while decrease as the incident beam angle increase. The grain size Zl of columnar dendrites increase as the heat input decreases.

The deformation and residual stress simulation of dual laser-beam bilateral synchronous welding for Al-alloy aircraft panel structure

The deformation and residual stress simulation of dual laser-beam bilateral synchronous welding for Al-alloy aircraft panel structure

Fracture mechanism on Al-Li alloy T-joint welded by dual laser-beam bilateral synchronous welding

Dual laser-beam bilateral synchronous welding technique is considered to replace riveting in terms of skin–stringer joints. The 2.0-mm thick Al-Li alloy T-joint, which is welded by dual laser-beam bilateral synchronous welding between 2099-T83 stringer and 2060-T8 skin, is investigated in the current study. Under the tailored process conditions, the examinations and analyses of microstructures, microhardness distribution, hoop tensile mechanical properties, and fractographies of the T-joint are conducted. Experimental results show that the maximum tensile strength of the weld seam is up to 85% of the tensile strength of the skin material. In order to explore the special fracture characteristics of dual laser-beam bilateral synchronous welding joints after tensile test, a three-dimensional finite element model is established and the residual stress of the weldment is analyzed. Considering the scanning electron microscopy results and simulation results comprehensively, stress concentration is the main reason for the weldment failure in tensile test.

Laser High-Speed Impact Composite Forming of Aluminum/Aluminum

Based on the laser-driven flyer micro forming and laser high-speed impact welding, this paper put forward the laser high-speed impact synchronous welding and forming new process, and builds the compound welding experiment platform. The three-dimensional deep field digital microscope of KEYENCE VHX-1000C was used to measure the surface morphology and the maximum deformation depth of the welding and formingsamples. By observing the surface morphology of the sample, it was found that strong plastic deformation occurred on the surface of the materials and well reproduced the shape of the mold. When the laser energy was below 4.5J, the maximum deformation depth of the samples increased with the laser energy. However, the maximum deformation depth decreased due to the spring back phenomenon when the laser energy was larger than 4.5J. The Axio CSM 700 confocal microscope was used to measure the morphology of the welding interface. The cross profile of the welding interface showed that most regions had been welded and the welding interface was nearly flat.

The deformation and residual stress simulation of dual laser-beam bilateral synchronous welding for Al-alloy aircraft panel structure

This paper reports a numerical investigation of dual laser-beam bilateral synchronous welding (DLBSW) for T-joint structure of aircraft fuselage. Finite element numerical simulation of DLBSW is carried out to obtain suitable matching of welding parameters for civil aircraft panels which composed of 6156 aluminium alloy skin and 6056 aluminium alloy stringer. The distribution of welding residual stress and welding distortion on the aircraft panels are predicted and discussed. Three-dimensional finite element model of the panel containing three stringers has been developed to simulate the temperature field, residual stress distribution and welded panel distortion. It is simulated that three stringers are welded to base plate of the specimen through different welding sequences and the welding sequence with the smallest distortion is acquired.

Experimental and numerical investigation of laser shock synchronous welding and forming of Copper/Aluminum

A novel laser shock synchronous welding and forming method is introduced, which utilizes laser-induced shock waves to accelerate the flyer plate towards the base plate to achieve the joining of dissimilar metals and forming in a specific shape of mold. The samples were obtained with different laser energies and standoff distances. The surface morphology and roughness of the samples were greatly affected by the laser energy and standoff distances. Fittability was investigated to examine the forming accuracy. The results showed that the samples replicate the mold features well. Straight and wavy interfaces with un-bonded regions in the center were observed through metallographic analysis. Moreover, Energy Disperse Spectroscopy analysis was conducted on the welding interface, and the results indicated that a short-distance elemental diffusion emerged in the welding interface. The nanoindentation hardness of the welding regions was measured to evaluate the welding interface. In addition, the Smoothed Particle Hydrodynamics method was employed to simulate the welding and forming process. It was shown that different standoff distances significantly affected the size of the welding regions and interface waveform characteristics. The numerical analysis results indicated that the opposite shear stress direction and effective plastic strain above a certain threshold are essential to successfully obtain welding and forming workpiece.

Research on the Characteristics of Double-Sided Hybrid Laser-GMAW Synchronous Horizontal Welding of High-strength Thick Steel Plates

Research on the Characteristics of Double-Sided Hybrid Laser-GMAW Synchronous Horizontal Welding of High-strength Thick Steel Plates

Renault develops innovative arc welding solutions for exhaust systems that cut production costs by 30 per cent

Outlines Renault’s development of cost‐effective exhaust manufacturing systems using synchronous robotic welding aided by vision technology, reports on the accuracy problems encountered and the solutions implemented, relates how cycle times have been cut and quality improved.