Welding Of Sheets Research Articles

The Effect of Top Surface Lubrication on the Friction Stir Welding of Polycarbonate Sheets

Abstract In this work, top surface lubrication during friction stir welding of polycarbonate sheets was applied. A homogenous layer of Paraffin wax has been placed on the top surface of the joint area with a width that ensures to cover the shoulder diameter. Then FSW was applied using conventional FSW tool with rotating pin and shoulder at different FSW parameters (Rotation speeds of 1 000, 1500, 2 000 min–1 and welding speeds of 25, 50, 75,100 mm/min). The main objective of using the wax is to act as a lubricant that reduces the friction between the shoulder and the polycarbonate surface. The joints produced were investigated in terms of surface quality, internal defects, and mechanical properties. During FSW the wax is melted and played as lubricant between the tool shoulder and the polycarbonate surface and resulted in defect-free surface with no thickness reduction of the original plate. The transverse cross-section showed defect-free joints for the majority of the FSW parameters investigated. Tensile testing results showed a reduction of the tensile strength after FSW, and an enhancement in the tensile strength with the increase of welding speed or rotation speed. The fracture occurs at the joint zone and the fracture surface investigation using SEM showed the existence of spherulitic structure in the weld joint.

Studying the effects of process parameters on the mechanical properties in friction stir welding of Al-SiC composite sheets

Friction stir welding (FSW) was applied to join Al-SiC composite sheets, and the response surface method (RSM) was employed to optimize the effects of traverse speed and rotational rate process parameters on the mechanical properties of welded sheets. Eleven test cases were designed to carry out the FSW process. The mechanical properties of the welded sheets were studied via tensile and microhardness tests. XRD diffraction patterns were also used to obtain residual strains. An RSM analysis was carried out on the results to determine the optimal process parameters and achieve the best mechanical properties for welded composite sheets. The results show that the combined effect of the two parameters played a key role in determining the tensile strength, microhardness, and residual stress and strain of the welded sheets. Optimal mechanical properties were obtained at a rotational rate of 1300 rpm and traverse speed of 70 mm/min.

Electrodynamic Treatment of Structural Elements Made of Aluminium and Magnesium Alloys

The article discusses the electrodynamic treatment (EDT) of thin-walled welded structures and EDT equipment, presents results of mathematical modelling concerning the effect of EDT on stresses in welded sheets made of aluminium alloy AMg6 as well as discusses the effect of EDT on the plastic strain mechanism. In addition, the article presents tests results concerning the effect of EDT during the welding of ship structures made of AMg6 plates and discusses the role of EDT in bulge formation. In addition, the article discusses the application of EDT during the repair welding of aero-engine nacelles made of magnesium alloy ML10 and the effect of EDT on openings in an airplane wing stinger in relation to its service life.

Effect of Strain Rate on the Tensile Mechanical Properties of Electron Beam Welded OFE Copper and High-Purity Niobium for SRF Applications

An investigation of the tensile mechanical properties of electron beam welded OFE copper and high-purity niobium sheets is presented. Specimens were deformed in tension at strain rates ranging from 10−3 to ~ 1600 s−1. The 0.2% yield stress and ultimate tensile strength (UTS) of the welded niobium specimens are similar to those of unwelded specimens at strain rates lower or equal to 20 s−1. At higher strain rates, these mechanical properties are lower for welded niobium specimens. The 0.2% yield stress of welded OFE copper specimens is consistently lower than unwelded specimens over the range of strain rates studied, while the UTS is comparable at all strain rates. The elongation to failure of welded OFE copper specimens remains unchanged at all strain rates while the ductility of niobium specimens reduces at strain rates greater or equal to 20 s−1 and reaches a minimum at ~ 400 s−1. The effects of the weld on a non-standardized short specimen geometry, developed for this study to obtain strain rates in the order of 103 s−1, are more pronounced for niobium due to large grain sizes (up to 1200 μm) in the fusion region. However, comparable strength and ductility trends, with respect to a standard specimen, were measured at low strain rates. The conservation of strength and the relatively high ductility of the welded sheets, especially for OFE copper, suggest that bent and electron beam welded tubes could be used for the fabrication of seamless superconducting radiofrequency (SRF) cavities. These results are promising for the use of high-speed forming techniques, like electro-hydraulic forming, for the manufacturing of parts using welded tubes and sheets.

ANN modeling and multiobjective genetic algorithm optimization of pulsed laser welding of Ti6Al4V alloy sheets with various thicknesses

According to the high cost and time-consuming nature of laser welding experiments, repetition of one experiment in a wide range of data is not feasible; so, achieving unexperimented data can be interesting. Hence, the high precision predictability of artificial neural networks (ANN) seems useful. ANN is an intelligent approach to solve different problems. In this study, the experimental data belonging to the pulsed laser welding of two Ti6Al4V sheets, one of them with 1 mm thickness and the other with 1, 1.5, and 3 mm thicknesses, were used to predict the dimensions of the heat-affected zone (HAZ) and the maximum temperature. Moreover, 12 learning methods of a backpropagation network was utilized to select the best one. The Levenberg–Marquardt method had the best performance by considering the mean square error. According to the ANN results, when the laser focus is at the vicinity of workpiece’s surface, the maximum temperature and HAZ width are achieved. It should be also mentioned that increasing thickness and welding speed results in decreasing width of HAZ. By comparing the ANN and experimental results, the maximum relative error for the temperature and HAZ width was obtained equal to 8.62% and 8.22%, respectively. Therefore, ANN can be employed as a tool to develop experimental results and predict indeterminate values in unexperimented ranges with very high precision. Furthermore, in order to optimize the parameters of laser welding, the multiobjective genetic algorithm was used to reduce the HAZ width. The genetic algorithm specified that the HAZ width can be reduced to 0.24 mm by increasing the velocity and thickness.

FOUNDATION OF THE NEW RAILWAY BRIDGE OVER THE NOSICKÁ DAM ON THE RIVER VÁH

The new railway bridge over the Nosická dam is a part of the complex modernization of the railway corridor from Púchov to Žilina. Our company participated on the project using a wide variety of special foundation techniques on artificial islands for piers P6, P5, P4 and P3 and the pillar foundations. We applied the many years of experience gained by our company through working on projects involving water. Bored piles, as well as vibrated sheet piles, welding and assemblage work have all been carried out from a floating pontoon platform and also there was jet grouting applied to stabilize embankments. At the same time we provided active assistance with temporary floating bridges and platforms for the kind of transfer on water required by our client.

Numerical Modeling and Experimental Analysis of Water Jet Spot Welding and Friction Stir Spot Welding: A Comparative Study

In this work, a finite element method was implemented to comparatively study the welding of AA6061-T6 aluminum alloy sheets by water jet spot welding and friction stir spot welding processes. The Johnson–Cook (J–C) model was applied to define the mechanical and thermal behaviors of the material during both welding processes. The simulation results showed good agreement with the experimental measurements. The process of jet impact on the flyer plate surface occurred on a short time scale which made it challenging to experimentally study the dynamic of this process. Therefore, a simulation was of great importance to consider this phenomenon. The water jet pressure and velocity, as well as the strain and stress distribution on the flyer plate surface, were thoroughly analyzed. The depression growth during the primary impact of the water jet was also studied. Regarding the FSSW process, mechanical characteristics such as stress and strain distribution, material flow, as well as the force and torque variation on the workpiece were investigated. Finally, the hardness profile and the temperature distribution in the joint area were compared in both welding processes.

Novel measures for spatter prediction in laser welding of thin-gage zinc-coated steel

This paper studies full-penetration remote laser stitch welding of thin-gage zinc-coated steel sheets in a lap joint condition. The spatter was classified as either Type A or Type B based on their characteristics, corresponding to low and high linear energies, respectively. The Type A spatter was mainly affected by the zinc vapor outgassing through the keyhole openings, while Type B was more influenced by the vulnerability of the keyhole rear wall to the impact of the high-pressure zinc vapor jet originating from the faying interface. Two measures, Zout and Zp, are proposed to predict the occurrence of Type A and Type B spatter. A thermo-fluid numerical model was developed to investigate the physics in the remote laser welding of zinc-coated steels, such as molten pool dimensions, keyhole stability, and zinc coating evaporation and to calculate Zout and Zp in the welding process. The effects of welding parameters, such as laser power and feed speed, on spatter occurrence were studied numerically and verified against experimental observations. It was found that the laser linear energy could directly affect values of Zout and Zp. A medium linear energy, striking a balance between Zout and Zp, could generate welds with much less spatter compared to a relatively low or high linear energy.

An experimental design of spot welding of Ti6Al4V sheets and numerical modeling approach

In this study, the traditional α–β titanium alloy Ti6Al4V sheets were joined by the resistance spot welding (RSW) process. RSW method was modeled numerically and investigated experimentally by using different welding parameters. In numerical modeling, material properties and process parameters were modeled with the finite element method (FEM), and simulations were realized in experimentally performed parameters. In order to validate and calibrate the developed numerical model, preliminary experiments were carried out and then Taguchi L9 orthogonal experimental design was determined to examine the effect of different parameters that are thought to be suitable for this process. The signal/noise (S/N) ratio was used to interpret the results in the determined experimental setup. The experimental study aims to validate the established numerical model and to obtain information such as the unpredictable strength of the welded joint through the numerical model. The experimental results were analyzed by using the Taguchi technique with the help of the Minitab software. In this study, electrode force, welding current, and welding time parameters were determined as the control factors, and the effect of these factors on the results was found using analysis of variance (ANOVA). Lastly, verification tests were performed, and it was determined that optimization was applied successfully.

Study of Friction Stir Spot Welding of Aluminum/Copper Dissimilar Sheets using Taguchi Approach

Friction stir spot welding of dissimilar aluminum and copper sheets was investigated in details using Taguchi approach in this study. Analysis of variance was conducted to identify the effective parameters and their contributions on the mechanical performance. The findings revealed that the outputs followed normal distribution. The results indicated that the rotational speed with the contribution of 87.7% was the most effective parameter on the maximum tensile force tolerated by the welded samples. Dwell time and penetration depth were in second and third ranks from effectiveness viewpoint with the contributions of 8.8 and 2.9%, respectively. The results revealed that the maximum tensile force was significantly improved with the rotational speed. The maximum tensile force was enhanced by almost 228% by increasing the rotational speed from 550 rpm to 1500 rpm. Increasing the dwell time from 10 to 20 s led to improve the maximum tensile force by 31%.The sequence of the parameters was as rotational speed, dwell time and penetration depth from standpoint of influence on the maximum force according to the results of signal to noise ratio analysis. The signal to noise ratio analysis showed that the rotational speed of 1500 rpm, the penetration depth of 2.85 mm, and the dwell time of 20 s were the optimum conditions.

The Mechanism of Weld Formationin Welding of Steel Sheets (Part 1: main modes of weld formation; geometrical characteristics of welding bath craters)

The Mechanism of Weld Formationin Welding of Steel Sheets (Part 1: main modes of weld formation; geometrical characteristics of welding bath craters)

A study on thermo-mechanical analysis of ultrasonically welded dissimilar alloys for automotive application

Abstract Ultrasonic spot welding (USW) method has the capability to produce highly efficient solid-state bonds in lightweight alloys with minimum power consumption. Unlike fusion welding techniques, this technique utilizes less energy and produces superb joint quality with refined grain structures and minimal intermetallic compounds (IMCs). This method has been receiving attention progressively in the material joining field because of its advantages like environmentally friendly, shorter weld time, and involvement of low temperature. Thus, these properties make this process suitable for welding of malleable thin metal sheets. During the USW process, it is noticed that the effect of intensive material contact increases when the weld progresses, and it leads to the frictional heating and plastic deformation phenomena. Subsequently, it results in the change of mechanical and microstructural characteristics at the weld zone. To reduce the forming load and static stress distribution from the welded samples, it is necessary to analyze the thermo-mechanical properties of ultrasonically welded joints. In the current study, various aspects of ultrasonic energy on material deformation and temperature variations are investigated using the finite element analysis (FEA). As a result, several types of features are noticed in the weld region with different forming morphologies. To further explore the effect of weld process parameters on the weld interface of this dynamic process, the strength and fracture in USW are also studied.

Dissimilar resistance spot welding of mild steel and stainless steel metal sheets for optimum weld nugget size

Different grades of steels are regularly used for various structural applications and it is always a difficult task to produce dissimilar welded joints. An attempt is made to weld thin sheets of mild steel (MS) and stainless steel (SS) materials by spot welding process by varying the different process parameters such as welding current, sheet thickness and different combinations of mild steel and stainless steel like MS with SS, MS with MS and SS with SS. The electrode is used as a copper and chromium alloy of 6 mm diameter. The experiment is designed as per the Taguchi L9 orthogonal approach by varying the three factors at three levels. The optimization of chosen factors and obtained weld nugget diameters as response values are performed to testify the statistical significance of the model terms by using R-square, analysis of variance (ANOVA), t and F tests, and desirability function. The outcomes will be useful in choosing the exact combinations of process parameters to achieve the desired quality spot-welded joints for automotive applications.

Impact of friction stir welding tool profile on the strength of dissimilar aluminium and stainless steel welded joints

The two different grades of alloys such as Aluminum AA6063 and stainless steel SS304 of 8 mm thickness are friction stir welded by taking factors like depth of the cut, tool pin profile, feed, tilt angle, rotational speed. The friction stir (FS) welding experiment is conducted by varying the tool profile as hexagonal, circular, square, triangular, and tapered and other factors as constant. The impact of tool profile on strength of weld joint is experimentally investigated by conducting hardness and tensile tests. The FS welding is performed to weld two dissimilar metals by varying the tool profiles to identify the suitable tool profile for effective dissimilar welded joint. The hexagonal pin profile found to be best for the FS welding of Aluminum AA6063 and stainless steel SS304 metal sheets as strength (tensile) of the weld joint is produced as 54.889 MPa and hardness 280.89BHN. The research work will help to suggest the suitable pin profile for Aluminum and steel metal sheets welding by the FS welding technique.

Laser dissimilar welding of copper and steel thin sheets for battery production

Laser processing of metallic thin sheets has gained undoubted industrial interest in the last decade especially due to its implications in the e-mobility field. In particular, dissimilar welding of thin sheets made of different materials, such as aluminum, copper, and steel is nowadays recognized as an effective solution for many joining applications in battery and related component production. According to these considerations, the present paper is aimed at evaluating the possibility to perform a sound joining of thin copper sheets on thin steel ones in a lap-welding configuration. This application is of particular interest especially when cylindrical cells have to be electrically connected to any of the elements constituting the battery, such as printed circuit boards, busbars, etc. By means of a continuous wave fiber laser and a galvo scanner, an experimental campaign was carried out in order to define a process window for characterizing the above-mentioned welding application. The results were characterized by means of metallographic analyses, microhardness measurements, electrical conductivity tests, and scanning electron microscopy-energy dispersive system analyses. Particular attention was placed on the role of process parameters in controlling the penetration depth on the lower steel layer, since it constitutes the external housing of the single cell and a drop through can seriously damage the cell itself.

Optimization of process parameters of friction stir spot welding of polycarbonate sheets and morphological analysis

AbstractFriction stir spot welding has a great impact on the joining process of thermoplastics. In this work, effects of varying rotational speed, plunge depth, and dwell time were investigated on polycarbonate sheets and a filler sheet was utilized to reduce the keyhole size of friction stir spot welded joints. The welding parameters were arranged according to Taguchi L9 orthogonal design of experiments to determine the optimum levels of process parameters. Lap shear tests were performed to examine the mechanical properties. Using analysis of variance and signal to noise ratio, influences of each welding parameter on the lap joint shear load were evaluated. According to achieved results, tool rotational speed has the highest effect while plunge depth has minimum effect on the mechanical behavior of friction stir spot welded joints. Optimum process parameters were attained as 1000 min−1 for rotational speed, 10.5 mm of plunge depth, and 40 s of dwell time. Optimized process parameters showed 15 % improvement compared to the initial welding parameters. Cross‐sectional appearances of welded samples which play an important role in determining lap joint shear load were analyzed by morphological and visual comparisons. Failure modes of the fractured samples for lowest, moderate and highest lap joint shear loads were also observed.

Deformation and Microstructural Analysis of Fiber Laser and TIG Welding of Thin Ti6Al4V Sheet by Coordinate Measurement Machine (CMM)

This paper reports on a study to compare the mechanical and deformation properties of Ti6Al4V titanium alloy joints between a pulsed fiber laser source and a tungsten inert gas (TIG) welding. Ti6Al4V alloy sheets - 0.8 mm thick-deformation modifications were investigated via a 3D laser scanner integrated to a portable-arm Coordinate Measurement Machine (CMM) and PC-DMIS software. Deformation pattern, residual distortions, weld geometry, microstructure and microhardnes properties of the joints produced with fiber laser source and tungsten inert gas welding were compared. Compared with the TIG, the welded by fiber laser has narrow heat affected zone (HAZ), small overall residual distortion, fine microstructure, high Vickers hardness. It can be concluded that fiber laser welding is more suitable for welding the thin Ti6Al4V titanium alloy plate than TIG welding; due to the small beam focus characteristics of fiber lasers enabiling deep penetration welding.

EXPLOSIVE WELDING OF HEAT RESISTANT ALLOYS BASED ON REFRACTORY METALS WITH HIGH STRENGTH STEEL

In this work, the parameters of explosive welding of plates and pipes from heat resistant alloys with high-strength steel were established. It was found that to ensure strong adhesion, it is necessary to increase the kinetic energy of a flayer plate made of a heat-resistant alloy several times in comparison with the explosion welding of steel sheets. Metallographic studies have shown that at similar modes of explosion welding in cylindrical products, the number of cast inclusions is significantly increased compared to sheets up to the appearance of a continuous layer at the weld interface. Mechanical tests have confirmed the quality of the joint. This material is promising for work in structures experiencing thermal and erosive effects.

THE ISSUE OF CLEANING AND ACTIVATION OF WELDED SURFACES DURING EXPLOSION WELDING OF LARGE-SIZED SHEET

The analysis of published data on cleaning and activation of welded surfaces during pressure welding in the solid phase has been carried out. A new understanding of cleaning and activation processes during explosion welding of large-sized sheets is proposed. It is based on the impact of the shock plasma, which arises during hypersonic shock-compressed gas flow around the welded surfaces.

Computational intelligence based prediction of joint penetration in laser fabrication

In the present study, laser welding of stainless steel sheets of 2.5 mm thickness was conducted to study the weld geometry parameters. The inputs considered here for laser welding were beam power, welding speed, and beam inclination angle. Experimental runs were conducted based on the central composite full factorial design. A multivariate regression model was developed to establish interdependency between input and output of laser welding. The novelty of the paper is in implementing an adaptive neuro-fuzzy inference system (ANFIS) for prediction of weld bead parameters in laser welded joint. An evolutionary algorithm like genetic algorithm (GA) and particle swarm optimization (PSO) had been applied to fine-tune the ANFIS parameters and to enhance the prediction capability of the established network. The performances of these networks were evaluated on the result of coefficient of correlation and root mean square error. Coefficient of correlation (R and root mean square error were found to be 0.9636 and 0.0521, respectively for PSO-ANFIS model. The prediction accuracy along with the performance criteria for the developed models pointed out that PSO-ANFIS model have better prediction accuracy than other discussed models.