Welding Of Sheets Research Articles

Mechanical Properties Analysis of Explosive Welded Sheet of AA2519-Ti6Al4V with Interlayer of AA1050 Subjected to Heat-Treatment.

The paper presents results of investigations of welding sheets of AA2519-Ti6Al4V, a difficult-to-joint components materials, produced by explosive welding with a thin technological interlayer of AA1050. The joining process leads to the formation of intermetalics in the vicinity of joint and generates significant residual stresses. In the next step the laminate was subjected to a heat treatment process in order to improve the mechanical properties by precipitation hardening. This treatment should not be carried out before welding because of negative influence on a ductility of the aluminum alloy. Material in this state was subjected to the tests of chemical composition, microstructure, and microhardness. A tensile test was carried out with accompanying strain analysis by the digital image correlation (DIC) method. Moreover, the residual stresses were determined which were measured by using two methods, the X-ray diffraction and the hole drilling. This approach made it possible to measure the residual stresses both in the plane parallel to the surface and in the cross section of the laminate.

Influence of Different Beam Oscillation Patterns in Electron Beam Welding of Niobium Sheets with Different Thickness.

The electron beam welding of the tubes and the half-cells for our 1.3 GHz single-cell superconducting radiofrequency (SRF) cavities is complex due to the different thicknesses of the tubes and the half-cells in the iris region. However, the mechanical properties and microstructure of the iris welds in niobium SRF cavities have barely been explored in previous studies. For high-quality iris welds, welding experiments of niobium sheets of 2 mm and 2.8 mm were carried out under different oscillating conditions. The results show that welding with no oscillation or sinusoidal oscillation may not be applied in actual welding owing to the large misalignment of the bottom surface. The weld grains were not significantly refined through beam oscillation. The joints with infinity oscillation had a higher elongation than circular oscillation, which exhibited a brittle fracture in the tensile tests at 77 K. Nevertheless, the texture of the weld with infinity oscillation implies poor formability, so the feasibility of infinity oscillation in actual welding needs verification in future study.

Formation of long-range ordered intermetallic η''' phase and the involvement of silicon during welding of aluminum-steel sheets

EN AW-6016-T4 aluminum alloy sheets were joined with zinc-coated DC04 steel sheets using the Cold Metal Transfer (CMT) welding process. Si-rich and virtually Si-free commercial filler alloys Al-3Si-1Mn (AA-4020) and Al-4.5Mg-Mn-Zr (AA-5087) were used. The influence of silicon on the formation and morphology of intermetallic phases in the joints was studied. The intermetallic seam was investigated by scanning electron microscopy (SEM), electron microprobe microanalyzer (EPMA) using wavelength dispersive spectroscopy (WDS), and transmission electron microscopy (TEM) using selected area electron diffraction (SAED), energy dispersive spectroscopy (EDS), and electron energy loss spectroscopy (EELS). Short-range ordered (SRO) η-Al 5 Fe 2 , long-range ordered (LRO) η'''-Al 5 Fe 2 , and θ-Al 13 Fe 4 phases formed in the Si-poor and Si-rich welds. The presence of Si in the filler metal leads to the additional formation of the α c -Al(Fe , Mn)Si phase. Grains containing η and η''' were identified. The continuous η seam was generally thinner for higher Si contents. It was found that Si contents higher than 3-3.5 at% in the η seam suppressed the formation of LRO η''' and favored the formation of η. • Impact of Si in the filler alloy on the intermetallic seam of Al-steel sheet joints. • Observation of the low-temperature stable, long-range ordered η”'-Al x Fe y phase in industrial welds. • Correlation between Si content and the formation of the η-type phase. • Domain formation of short-range and long-range ordered regions.

Friction Stir Spot Welding of Different Thickness Sheets of Aluminum Alloy AA6082-T6.

Friction stir spot welding (FSSW) is one of the important variants of the friction stir welding (FSW) process. FSSW has been developed mainly for automotive applications where the different thickness sheets spot welding is essential. In the present work, different thin thickness sheets (1 mm and 2 mm) of AA6082-T6 were welded using FSSW at a constant dwell time of 3 s and different rotation speeds of 400, 600, 800, and 1000 rpm. The FSSW heat input was calculated, and the temperature cycle experience during the FSSW process was recorded. Both starting materials and produced FSSW joints were investigated by macro- and microstructural investigation, a hardness test, and a tensile shear test, and the fractured surfaces were examined using a scanning electron microscope (SEM). The macro examination showed that defect-free spot joints were produced at a wide range of rotation speeds (400–1000 rpm). The microstructural results in terms of grain refining of the stir zone (SZ) of the joints show good support for the mechanical properties of FSSW joints. It was found that the best welding condition was 600 rpm for achieving different thin sheet thicknesses spot joints with the SZ hardness of 95 ± 2 HV0.5 and a tensile shear load of 4300 ± 30 N.

Sequentially combined thermo-mechanical and mechanical simulation of double-pulse MIG welding of 6061-T6 aluminum alloy sheets

Double-pulse MIG (DP-MIG) welding is an efficient aluminum alloy jointing technique, which can form heterogeneous aluminum alloy welded sheets with different microstructure and mechanical properties. In order to accurately analyze and predict mechanical properties of welded structures, the geometrical features, local material properties and residual stresses of different welded zones should be synthetically considered in the numerical simulation. This work proposes a sequentially combined thermal-mechanical and mechanical simulation to accurately characterize the mechanical properties of the welded joint through the finite element analysis (FEA) method. The thermo-mechanical simulation was carried out to analyze the transient temperature field and residual stress distribution, which are conductive to build mechanical simulation model with detailed geometric features, the corresponding local material properties as well as attached residual stress. Subsequently, the mechanical simulation was performed to investigate the stress distribution of the welded joint. The deformation behavior and load-carrying capacity of the welded joint from numerical simulation are all in good agreement with corresponding experimental study, which indicates the feasibility and superiority of the developed sequentially combined thermal-mechanical and mechanical simulation method. Also, the stress distribution of the welded joints analyzed by numerical simulation reveals that the fracture evolution mechanism depends on whether the reinforcement has been removed from the welded specimen. The existence of the weld reinforcement leads to the increase of shear stress under tensile condition; hence, the fracture morphology includes equiaxed dimples and elongated dimples. When the reinforcement is removed, the mechanism is trans-granular and inter-granular mixed fracture in the welded zone; otherwise, trans-granular fracture occurs in the heat-affected zone.

Research on quality inspection model of spot welding of equal-thickness three-layer sheets based on ultrasonic A-scan

To judge the spot welding quality automatically and effectively, this thesis uses the conventional ultrasonic A-scanning to study the mathematical model of nugget diameter for equal-thickness three-layer sheets. The finite element simulation model of the spot welding ultrasonic nondestructive (NDT) testing for equal-thickness three-layer low carbon sheets is established. The calculated values of the nugget diameter between different laminates are studied. Finally, the experiment of the spot welding ultrasonic nondestructive testing is carried out. This thesis verifies the correctness of the finite element simulation and the mathematical calculation model. The research results are of great significance to ultrasonic automatic inspection technology of spot welding.

The role of the underburden at Elgin Franklin in the understanding of the overburden 4D signal

Elgin, Franklin, and West Franklin are high-pressure high-temperature fields located in the Central North Sea. The fields share a similar reservoir and overburden geology. During the life of the fields, they have undergone a similar depletion over time. However, each field shows a different 4D behavior in the overburden. The 4D signal on Elgin is the strongest and is located away from the wells. The Franklin 4D signal is in line with expectation as the strongest signal close to the wells. On West Franklin, the 4D signal is small and barely distinguishable from noise. To explain the differences in 4D signal between the fields, a detailed underburden salt interpretation is performed. The differences in underburden between Elgin (thick with an abundance of salt) and West Franklin (marginal underburden with proximal salt) show a strong correlation with the 4D signals of the overburden. The renewed salt interpretation is used to update a vintage geomechanical model, from which strains and stresses are computed. During the stress initialization of the geomechanical model, the underlying salt (thick sheet or salt weld) creates stress perturbations on the salt/rock interface. When the reservoir compaction is simulated, the 3D model simulates the vertical stretches differently in the overburden for the fields. The stretching varies according to the underburden thickness and presence of salt below the underburden. The results of the geomechanical modeling help explain the differences observed in the overburden 4D signal of the fields.

Analysis and control of axial pressure in high-speed friction stir welding of alloy sheet

Aiming at the high-speed friction stir welding deformation and thickness reduction of 1 mm 6061-T6 aluminum alloy sheet, the characteristics of the axial pressure of the welding process and its influence on the joint structure and mechanical properties were analyzed in this paper. Experiments were performed to optimize process parameters. A fuzzy controller with axial pressure error and its change rate as input and welding speed as output had been designed to realize axial pressure control during friction stir welding. The welding axial pressure fluctuates slightly around the target value, and the system was stable with the controller. Besides, the microstructure of the corresponding weld nugget area was uniform, dense, and the transition area was uniform without obvious welding defects. The joint hardness distribution was stable with the classic “W” shape distribution. The mechanical properties of the joint were excellent, and the tensile strength reaches 195 MPa, which was about 70% of the base material (290 MPa).

On the laser beam absorption efficiency in laser welding of aluminium thin sheet with copper pipe

Welding is considered the most versatile joining method, with extensive applicability in every modern industrial field. Especially, laser welding technology is widely utilized due to its numerous advantages, and its capability to process a variety of different materials. Among the several process parameters that impact the welding results, the absorbed energy and the power density are of major importance. These parameters mainly depend on the utilized materials and their physical properties, as well as the laser beam inherent characteristics. Moreover, the welding of more complex shapes and geometries is even more challenging, since multiple scatterings are taking place as well. The current paper presents a simulation model of the laser beam path and its absorption in the case of welding an aluminium thin plate and a copper pipe. The Ray Tracing method has been employed, while, the model’s geometrical parameters, are dimensionless, reduced to the pipe's radius. The materials’ absorption coefficient is calculated as a function of the incident angle, while the multiple scatterings are taken into consideration. From the simulation, the total absorption, as well as the relevant power density are calculated for a series of different initial process control parameters, i.e., spot size, incident angle, relevant laser spot position.

Friction stir welding of AA3003-clad AA6013 thin sheets: Microstructural changes related to tensile properties and fatigue failure mechanism

The microstructure, tensile properties, and fatigue behavior of friction stir welding (FSW) joints of multilayer AA3003-clad AA6013 are experimentally investigated. Linear butt welding is performed using a concave tool equipped with a columnar threaded pin at a rotating speed of 600 rpm and a transverse speed of 200 mm/min. The microstructures of FSW joints were observed using a field emission scanning electron microscope equipped with an electron backscatter diffraction system and an energy dispersive spectrometer. The microstructural characterization in the stir zone (SZ) reveals grain refinement, precipitate refinement, zigzag line, and the AA3003-clad layer fragments due to material mixing. The tensile test result of all-weld joints shows that the tensile strength of the SZ is significantly higher than that of base metal, while the cross-weld joints show a typical ductile fracture in the base metal. The result of fatigue tests shows that all the cross-weld joints fracture from the SZ. Analysis of the fatigue failure mechanism indicates that the crack causing the fatigue fracture originates from the AA3003-clad layer fragments in the advancing side of the SZ. The fatigue analysis also confirms that surface roughness and zigzag line are not the cause of the final fatigue fracture of the cross-weld joint for the present study.

Analytical Estimation of Electromagnetic Pressure, Flyer Impact Velocity, and Welded Joint Length in Magnetic Pulse Welding

Magnetic pulse welding involves the joining of two metallic parts in a solid state by the use of a short and intense electromagnetic impulses and the resulting impact between the parts. The coalesced interface undergoes visco-plastic deformation at a high strain rate and exhibits a wavy shape at a microscopic scale. A practical estimation of the electromagnetic pressure, impact velocity and welded joint length as a function of the process conditions and the electromagnetic coil geometry is required but currently not available. Three novel analytical relations for the estimation of the electromagnetic pressure, impact velocity, and welded joint length for magnetic pulse welding of tubes and sheets, are presented. These relations were developed systematically, following a dimensional analysis, and validated for a wide range of conditions from independent literature. The comparison of the analytically computed results and the corresponding values reported in the literature has illustrated that the proposed analytical relations can be used for the estimation of the electromagnetic pressure and impact velocity for the magnetic pulse welding of tubes and sheets with a good level of confidence. The analytically calculated results for the welded joint length show a little discrepancy with the corresponding experimentally measured values. Further investigations and more experimentally measured results are required to arrive at a more comprehensive analytical relation for the prediction of welded joint length.

Experimental investigation of friction stir spot welding of polymer-aluminum alloy weldments

The friction stir spot welding (FSSW) process is one of the main solid-state joining methods used widely for welding different materials and dissimilar metals. In this article, the welding of Polytetrafluoroethylene (PTFE) and aluminum alloy sheets by the FSSW process will be investigated experimentally. The joining of polymer (PTFE) and metal (AA1050 aluminum alloy) was done successfully. The effect of process parameters including tool rotational speed, penetration depth, initial holding time, dwell time, and tool shoulder diameter on the joint strength and elongation of the weldments will be studied using response surface methodology (RSM). The joint strength was increased by creating a threaded hole in the aluminum sheet. A mechanical lock was created between the softened PTFE and the edge of the threaded hole. The shear-tensile tests have been carried out for 32 designed experiments. The results show that the joint strength increased by increasing the initial holding time due to the better wettability of PTFE and aluminum sheet. The joint strength increased by increasing the tool rotational speed and tool diameter (better pouring of the hole and formation of the mechanical lock). Two different fracture modes have been observed in the samples: (1) fracture in the peripheral area of the joint (partial interfacial fracture mode) and (2) fracture in the mechanically locked area (pull-out mode with tearing).

Investigation and Optimization of Resistance Implant Welding of Polypropylene Sheets

Recently, the use of resistance welding in the joining of polymeric materials and polymer composites in the aviation, marine, and automotive industries has been gradually increasing. However, challenges continue in regard to improving product quality as affected by several parameters. This study focused on the effects of wire geometries and wire diameters on the characteristics of polypropylene (PP) sheets united by resistance implant welding. Here, PP sheets manufactured by the injection molding method were joined via the resistance upset welding method with three different wire geometries, including spiral, wavy, and M-shaped, and two different wire diameters of 0.3 and 0.5 mm. Mechanical properties, morphological properties, and heating characteristics were examined. The results showed that wire diameter and wire geometry affected amount of heat formation in the weld zone and, therefore, weld performance in terms of the mechanical properties. The results obtained from the study can be used as a reference in similar applications.

Effect of the strength of steel sheets and wires on residual stress of thin steel sheet lap-fillet GMA weld joint

Weld residual stress of the lap fillet GMA welding joints which was performed using two strength grades of steel sheets and two strength grades of welding wires were measured. In addition, to consider the effects of steel sheet strength and weld metal strength on welding residual stress, thermal elastoplastic analysis using FEM was carried out for the experiments. As a result of the analysis using the temperature history of the heat-affected zone as a fitting parameter, the residual stress distributions near the toe were in agreement with the measurement in the FE analysis. Comparing the residual stress distributions in the direction perpendicular to the weld line on the weld metal surface near the toe, which is the occurring point of fatigue cracks in the FE analysis results, with the same steel sheet, the higher the weld metal strength the smaller the tensile residual stress. And comparing with the same wire, the higher the steel sheet strength the higher the tensile residual stress. The reason for the former is that when using high-strength wire, cooling transformation occurs at a lower temperature than using low-strength wire. As a result, it is considered that the tensile residual stress was effectively reduced by causing transformation expansion while the surrounding strength was high. The reason for the latter is considered to be that each stress value changes based on the yield stress of the steel sheet and weld metal because the plastic strain continues to occur in each direction until transformation occurs after welding. It was considered that the larger the ratio of the hardness of the weld metal to the base metal, the smaller the ratio of the residual stress of the weld metal near the toe to the yield stress.

Prediction of welding responses using AI approach: adaptive neuro-fuzzy inference system and genetic programming

Laser welding of thin sheets has widespread application in various fields such as battery manufacturing, automobiles, aviation, electronics circuits and medical sciences. Hence, it is very essential to develop a predictive model using artificial intelligence in order to achieve high-quality weldments in an economical manner. In the present study, two advanced artificial intelligence techniques, namely adaptive neuro-fuzzy inference system (ANFIS) and multi-gene genetic programming (MGGP), were implemented to predict the welding responses such as heat-affected zone, surface roughness and welding strength during joining of thin sheets using Nd:YAG laser. The study attempts to develop an appropriate predictive model for the welding process. In the proposed methodology, 70% of the experimental data constitutes the training set whereas remaining 30% data is used as testing set. The results of this study indicated that the root-mean-square error (RMSE) of tested data set ranges between 7 and 16% for MGGP model, while RMSE for testing data set lies 18–35% for ANFIS model. The study indicates that the MGGP predicts the welding responses in a superior manner in laser welding process and can be applied for accurate prediction of performance measures.

Effects of Discharge Current on Velocity of Moving Sheet and Joining Property in Welded Sheet Processed by Magnetic Pulse Welding

A systematic experiment was performed for four types of welding circuit with different circuit inductances and a common welding coil, where each circuit inductance is given by the sum of a different remaining inductance and a common effective inductance. It was demonstrated that increasing the circuit inductance causes adverse effects on the discharge current, resulting in a long first collision time and a low deformation velocity of the moving sheet. When the circuit inductance increases from 0.0587 μH to 0.2280 μH, the maximum current decreases from 223 kA to 132 kA at a discharge energy of 2.0 kJ. With the decrease in discharge current, the deformation velocity of the sheet decreases from 383 m∙s-1 to 164 m∙s-1. The higher the circuit inductance is, the lower the deformation velocity of the sheet is. With the lower velocity, the shearing load of the resulting welded sheet further decreases, ultimately leading to joining failure. However, in the circuit with a minimum inductance of 0.0587 μH, it is possible to weld an aluminum alloy sheet to a 1 GPa class high-strength steel sheet. It has been clarified that the decrease in circuit inductance improves the joining property of a welded sheet.

Welding of polymers by infrared laser radiation

A number of polymeric materials are translucent for infrared radiation. The use of low-power infrared lasers makes it possible to weld polymer sheets due to the penetration of radiation into the material depth. The possibilities of transmission welding of polybutene sheets, as well as several layers of polyethylene film are investigated. Epilog Fiber Mark 20 installation equipped with 20-W fiber infrared laser with 1.062 μm radiation wavelength is used. According to the investigation results, the maximum penetration depth of polybutene sheets at thea given radiation power is determined. The ability of welding up to eight layers of colored polyethylene film of PVD-108 and PVD-158 grade is shown.

Структура и свойства неразъемного соединения титанового сплава, полученного методом сварки трением с перемешиванием

In this paper we have successfully formed fixed joints by butt friction stir welding of rolled sheets made of Ti-6Al-4V titanium alloy, using tool made of a heat-resistant alloy based on nickel ZhS6U with liquid cooling in the welding process. There was found a formation of a part of the welding tool material in the stirring zone of the fixed connection by methods of metallographic analysis. It was shown by fractography methods that the fracture in the joint zone was ductile, however, when the tool material was caught, the fracture was brittle. In spite of this, by modifying the welding parameters, it became possible to obtain a connection equal to the strength of the base metal.

Dissimilar laser welding of copper and stainless-steel thin sheets for e-mobility applications

The article deals with laser welding of dissimilar materials: lap-welding was carried out in case of 0.24 mm thick pure copper on 0.5 mm thick AISI 304L stainless-steel sheets. The experiment was planned by means of DOE techniques and a full factorial design with three replicates was carried out. In order to characterize the joints, both in terms of mechanical and electrical characteristics, several analyses were performed. Shear tensile tests put in evidence the mechanical behavior of the joint with respect to laser power and welding speed, while hardness measurements allowed to evaluate the presence of eventual fragile intermetallic phases. Considering the potential application of this kind of joint in e-mobility, electrical resistance was measured by means of a 4-points micro-ohmmeter. Mechanical and electrical tests were performed both in single and in double bead configurations, so that the role of the extension of the joining area could be assessed.

Microstructural characterization of Friction stir assisted laminated lap welding of AA6063 sheets

Friction stir welding is a pioneering new technique for solid-state joining of Aluminium alloys, which also further strengthens the mechanical and microstructural properties of the base metal. Laminated lap welding on AA6063 sheets was performed using a stainless-steel tool with a square cross-section pin. The sample thus obtained was examined for their microstructural and hardness properties, and was characterized accordingly. Equiaxed grain structures are obtained commonly in friction stir welded samples. A refined grain size of ∼ 15 μm was observed in the microstructural characterization. The hardness profile depends on the degree of grain refinement as explained by the Hall-Petch effect. The microhardness was observed to be 135 % of the base metal hardness. The study has hinted towards the improvement of properties after friction stir lap welding and serves as a base for multilayer solid-state joining as a future prospect.