Similar Welds Research Articles

Influence of Softening Mechanisms on Base Materials Plastic Behaviour and Defects Formation in Friction Stir Lap Welding

The AA6082-T6 and AA5754-H22 aluminium alloys were selected as the base materials to fabricate similar and dissimilar friction stir lap welds. Three lap configurations, AA6082/AA5754, AA5754/AA6082 and AA6082/AA6082, were produced using three pin profiles and tested to analyse the role of the plastic behaviours of the base materials on the welding conditions. The macrostructural characterisation was carried out to understand the material flow response and hook defect formation. The mechanical characterisation of the joints was done by microhardness and lap tensile shear testing. The finite element analysis and phase simulation were conducted to predict the phase dissolution temperatures and the softening kinetics. The welding torque and axial forces registered were analysed to quantify differences in the alloy’s flowability during welding. The analysis of the welding machine outputs enabled to conclude that higher axial forces were registered when the AA5754 alloy was placed at the top of the dissimilar lap joint, showing that the non-heat-treatable alloy has lower flowability than the heat-treatable alloy. These results were associated with the flow-softening of the AA6082 alloy in plastic deformation at high temperatures. The coupled experimental and numerical analysis revealed that the plastic behaviour of the base materials strongly influenced the material flow and, in this way, the hook defect formation and the shear tensile properties of the welds.

Development and application of knowledge-based software for railcar frame welding process

As main welded components of the rail vehicle, the railcar frames have specific needs in preparing a suitable welding document for each welded joint to guide the welding process during the manufacturing process. In this paper, the expert system and database technology are introduced into the field of rail vehicle welding process preparation, and a knowledge-based software for railcar frame welding process is developed. This system could maintain the normal operation of the enterprise rail welding system based on knowledge base and database. The numerous paper-based and fragmented electronic documents are stored in a unified format within the system’s database, and a reasoning mechanism based on Rule-Based Reasoning (RBR) and Case-Based Reasoning (CBR) is designed to intelligently match the welding procedure specification (WPS) and welding procedure qualification report (WPQR) online. Furthermore, the system supports multiple departments and personnel by integrating the function of workflow to carry out the WPS prepare and review process. Thousands of welded joints with various structures and complex positions in the same vehicle body can be aggregated into a welding summary table to reduce the repeated welding procedure qualifications (WPQ) of the same or similar welding joint. This method not only saves manpower and resources, but also ensures the accuracy of these process documents. In the end, the future development trend of this kind of application software is prospected.

Effects of various tool plunge depths on microstructure evolution, mechanical properties and dome structure features of friction stir spot welded AA5052‐H32 similar joints

AbstractThe solid‐state nature of friction stir spot welding process provides outstanding advantages for the sound joining of aluminum alloys. Within this study, 3 mm‐thick AA5052‐H32 sheets are successfully joined by friction stir spot welding using 2344 hot‐worked steel pin to investigate the effects of various tool plunge depths on the microstructure, mechanical and metallurgical properties of similar welds. Therefore, the experiments are performed at different plunge depths in the range of 3 mm–4 mm. Accordingly, the relationships between the process parameter (tool plunge depth) and the responses (microstructure, dome structure, microhardness and lap shear tensile load) are established. Microstructure analyses demonstrate that the increase in the plunge depth leads to more grain refinement within the stir zone, which significantly affects the mechanical performance of the similar joints. This study also indicates that the tool plunge depth in friction stir spot welding process has a noteworthy influence on the characteristic features of the 5052 aluminum alloy joints, such as the dome structure. Moreover, an explicit increase in the microhardness towards the weld stir zone is observed in all specimens. It is found that the average maximum tensile‐shear force enhances with the increment in the tool plunge depth from 3 mm to 4 mm.

High strength impact welding of NiTi and stainless steel wires

This work demonstrates the use of a solid-state microwelding process to create very high strength welds between superelastic NiTi and themselves as well as stainless steel (SS) wires. Vaporizing foil actuator welding (VFAW) uses the pressure from a vaporized metal foil to impact weld the wires by driving them into one another. The small scale nature of this explosive-like process allows its use in factories. Advanced techniques were used to examine the structures and properties of the welds that were created. The NiTi/SS welds had the typical wavy interface of ideal impact welds, with no thermally induced defects such as chemical segregation near the interface or brittle intermetallic formation. These latter two are significant issues in traditional fusion based methods. Microhardness tests show that the NiTi/NiTi and NiTi/SS weld interfaces were locally strengthened compared to the softening of other welding processes. Lap shear tests show that NiTi/SS welds made by VFAW present much higher joint efficiency (near 100%) compared to less than 60% for other traditional joining technologies. Tensile cycling of both the NiTi/NiTi and the NiTi/SS welds shows similar stabilization of the pseudoelastic curves as the NiTi base metal. The irrecoverable strains of the NiTi/NiTi welds and NiTi/SS welds after cycling were comparable to that in the NiTi base metal. The unparalleled performance of these high-strength solid-state similar and dissimilar welds of nitinol is a solution to the increasing demands of applications in various industrial fields including the medical, aerospace and electronic sectors.

Analytical Structural Stress and Stress Intensity Factor Solutions for Similar and Dissimilar Spot Welds in Cross-Tension Specimens

Analytical Structural Stress and Stress Intensity Factor Solutions for Similar and Dissimilar Spot Welds in Cross-Tension Specimens

Prediction of weld geometry, temperature contour and strain distribution in disk laser welding of dissimilar joining between copper & 304 stainless steel

In this study, a simulation is developed for dissimilar metal sheets followed by a mathematical model for laser welding. The continuous disk laser welding process for dissimilar joining between 304 stainless steel and copper is simulated. For this purpose, six different heat flux distribution models are implemented into Abaqus/Standard solver using additional DFLUX subroutine written in the FORTRAN programming language. By estimating the temperature distribution, prediction of the geometry and dimensions of weld cross section including the fusion zone (FZ) and heat affected zone (HAZ), a heat source model was suggested for finite element modelling of the dissimilar keyhole laser welding process for joining 304 stainless steel and copper sheets with 20 × 15 × 2 mm dimensions by butt joint. The weld joint output parameters such as temperature, strain distribution and weld geometry were examined. The results showed that copper, due to the higher thermal conductivity during cooling, passed through more heat at the same period of time, so these results lead to lower temperature in the center of FZ and a smaller HAZ in this dissimilar welding in comparison to similar welding. The validation of the simulation results, including the temperature distribution, weld cross section geometry, dimensions of FZ and HAZ, was confirmed by comparison with the experimental results reported by other researchers. The computed results are well agreed with experimentally measured values and show the robustness of the present numerical model used for dissimilar laser welding.

Statistical Review of Microstructure-Property Correlation of Stainless Steel: Implication for Pre- and Post-Weld Treatment

For the past three centuries, there has been a very high demand for stainless steel for different applications, due to its corrosion resistance coupled with the good strength and low cost of the metal. Several welding techniques have been adopted in the fabrication of stainless steel, with the choice of welding technique hinged on the desired requirements. Advancement has been made in its dissimilar welding with other metals like aluminum, copper and titanium. While similar welding of stainless steel faces the challenge of weld metal property deterioration, dissimilar welding poses more serious challenges due to the differential in chemical composition and the thermophysical properties of the base metals. A review of the literature reveals that considerable progress has been made in the improvement of the properties of the weld joint by the application of several weld treatment processes. It was discovered that most of the researchers focused on the effect of these weld treatment processes on the properties of the weld joints, with little attempt to establish a relationship between the microstructure and properties. This review paper critically analyzed the effect of weld treatment processes on the properties of stainless steel in light of microstructure-property correlation.

Comparative study between MSC Marc/Mentat student version and Simufact Welding for three-passed butt joint

In this research, FEM simulation was created butt joint with weld filler 3D-solid geometry. The assigned substrate element type is created and modeled on a 9 mm thickness. The three-passes of butt joint was undergoing with using the MSC Marc / Mentat student version simulation and simufact welding simulation. The butt joint designed with three passes which are penetration, filler pass and the capping for both simulations. Thermo-mechanical FEM simulations using MSC Marc / Mentat student version and simufact welding are implemented throughout the analysis. The preferred heat source model is an ellipsoid Goldak normally used for arc welding processes and weld path process in one direction. The temperature distribution caused by the welding process on the specimens must be analyzed with the same clamping conditions and the same load. Both simulations were collecting the temperature distribution to observe the calibration of software. From the results of the temperature distribution, which simulation can be assessed which is more accurate. But to be more accurate in comparing it, the two simulations must be compared directly with the experimental, with the similar material, dimensions, and welding parameters.

Long-term thermal degradation of narrow gap orbital welded P91 and P92 steels

This paper deals with an evaluation of mechanical properties and microstructures of similar and dissimilar narrow gap orbital welds of martensitic steels P91 and P92 after long-term laboratory ageing at elevated temperatures (650, 675 and 700 °C, 5000 to 30 000 h). Conclusions of this assessment are the kinetic dependencies of structural and mechanical properties changes during long-term exposure to high temperatures.

Tegangan Ambang pada Sambungan Las CDW antara Baja dan Kuningan dalam Lingkungan Korosif

Failure at the welded joint can be occurs due to the Stress Corrosion Cracking (SCC) phenomenon. Dissimilar welding is more susceptible to SCC when compared to similar welding. This can be occurs because the material or metal that connected is non-homogeneous material. which causes the material will be difficult to be combined perfectly. This study aims to determine the threshold stress (σ Th ) at the dissimilar welded joint between steel and brass which have SCC loads. Both materials were connected by the welding method by using a Capacitive Discharge Welding (CDW) welding machine. Surface preparation or surface treatment is applied to one of the basic materials (low carbon steel) to obtain optimal joint results. The welded joint was tested by using Constant Load Test (CLT) methods, which is engineered in such a way that the welded joint get the stress, corrosive environment (1M NHO 3 solutions) and voids produced by the weld joint itself. The result shows that the threshold stress of the dissimilar welding joint between steel and brass by the CDW method is 330 MPa.

Improving the mechanical property of dissimilar Al/Mg hybrid friction stir welding joint by PIO-ANN

Ultrasonic-stationary shoulder assisted friction stir welding (U-SSFSW) is a novel hybrid welding technique, which reveals promising prospect in joining Al/Mg dissimilar alloys. A thorough understanding of U-SSFSW process is imperative for the further application of this technique. Pigeon-inspired optimization (PIO) is a swarm intelligent optimization algorithm and is proposed in mathematical modeling and process optimization by artificial intelligence. In this study, PIO optimized artificial neural network (PIO-ANN) was firstly established to acquire the relationships between the inputs and output of the Al/Mg welding process by U-SSFSW technique. A reliable PIO-ANN was achieved and the joint with a tensile strength of 161 MPa was acquired under the PIO optimized parameters. This tensile strength is higher than any ever-reported results with the similar welding condition. The joint formation, microstructure, microhardness and fracture behaviors were systemically investigated based on the reported studies and the confirmation experiment of this study to explore the enhancing mechanism of U-SSFSW Al/Mg joint.

Effect of welding sequence on stress and deformation field of Invar alloy multi-layer and multi-pass welding: A simulation study

The welding sequence has an important influence on the formation of stress and deformation in multi-layer and multi-pass welding (MLMPW). In this paper, a 3D finite element model of Invar alloy welding that can calculate the welding stress and deformation has been established using MSC. Marc. The simulation results show that there is high residual tensile stress in the welding zone. For six-layer twelve-pass welding, the welding sequence has little effect on maximum stress value. Meantime, welding deformation is mainly distributed far from the weld metal area and is mainly affected by welding sequence under similar other welding conditions. It is found that the deformation angle of welding sequence D is the smallest, with a value of [Formula: see text].

Microstructural Evaluation of Similar and Dissimilar Welding of Aluminum Metal Matrix Hybrid Composite by Friction Stir Welding

To address the challenges of reducing the CO2 emission in automotives, Aluminum metal matrix hybrid composites have been extensively used in automotive and aerospace industries for the fabrication of light weight structure. Huge demand in joining dissimilar metals increased day by day, because it reduces the weight and cost of components by utilizing hybrid structures. The friction stir welding is adopted for dissimilar AA5754 rheo-squeeze cast (RSC) with AA7075 stir casted hybrid composite. Micro sized B4C and nanosized Al2O3 are reinforced into this material. Friction stir welding of these alloys by varying the tool material, pin and shoulder profiles, rotational speed, tool traverse speed and tilt angle. Microstructure of the joint are studied and inferences drawn are presented. The better welding was obtained with triangular and square pin profile when compared to cylindrical pin whereas triangular pin profile was more better than square pin. Tapered shoulder possessed greater strength, which resulted in a good weld in contrast to flat shoulder. The high carbon high chromium steel (HCHCr) tool exhibited a higher tool wear rate than stainless steel (SS) tool and found to be an appropriate one to weld aluminum hybrid composite.

Analysis of fatigue properties in similar friction stir welding joints of aluminum alloy ( AA5086-H32 )

Similar aluminum alloys (AA5086-H32 with AA5086-H32) were welded by friction stir welding (FSW) using three different values of linear speeds; namely 50, 75 and 90 mm/min.and different and rotating speed namely 680, 920 and 1500 rpm. Tensile test was used to determine the joint efficiency of welded samples. The microstructure, hardness, tensile tests and fatigue properties were studied for the welded sample which gave the highest tensile strength. The fatigue test was carried out at a constant stress amplitude cantilever fully reversed( R=-1) in the stir zone of weld and nearby zone or region at a distance of 5, 10 and 15 mm from the welding line. The fracture fatigue surface was analyzed using SEM. It was found that the maximum joint efficiency of 80% was obtained at rotating speed of 680 RPM and linear speed of 75 mm/min. The maximum value of hardness was at the stir zone center of the weld and started to decrease away from it. Fatigue strength of the FSW welded samples was less than the parent or base alloy.

Effect of welding process parameters on embrittlement of Grade P92 steel using Granjon implant testing of welded joints

Precipitation of Cr-rich carbides, diffusible hydrogen content and heterogeneous microstructure formation across the weldments makes heat-affected zone (HAZ) susceptible to intergranular cracking and makes weldability of creep strength enhanced ferritic (CSEF) Grade P92 steel a critical issue. In the present research work, the Granjon implant test and mercury method (for diffusible hydrogen measurement) have been performed on Grade P92 steel welded specimens to study the effect of welding parameters on diffusible hydrogen levels and their subsequent effect on hydrogen-assisted cracking (HAC). The weld metal was deposited by a shielded metal arc welding process on Grade P92 steel samples using P92 matching filler. The three different welding conditions are used to measure the diffusible hydrogen level in the deposited metal. Granjon implant test was performed to evaluate HAZ HAC susceptibility with similar welding conditions which were used in the mercury method. Lower critical stress (LCS) was also evaluated using the Granjon implant test. The higher susceptibility of CSEF Grade P92 steel welded plate towards HAZ HAC was noticed in case of lower heat input or higher diffusible hydrogen content. However, by considering LCS, fracture mode and diffusible hydrogen content, the weld deposited using the highest heat input (condition III) offers great resistance to HAZ HAC.

Similar and dissimilar welds of ultrafine grained aluminium obtained by friction stir welding

Samples from commercially pure aluminium were subjected to various number of passes of Incremental Equal Channel Angular Pressing (I-ECAP) and subsequently welded using Friction Stir Welding (FSW). Similar and dissimilar welds were obtained and investigated in terms of their microstructure and mechanical properties. In the case of similar weld from coarse grained aluminium in the stir zone a decreased average grain size was obtained, which resulted in enhanced microhardness. In the case of samples after I-ECAP, the ultrafine grained regime has not been preserved, which caused a drop in microhardness in the stir zone. Nevertheless, obtained results were still higher than those for coarse grained sample. In all welds the average grain size of 2.1–3.7 μm was obtained. No correlation between the microstructure of base material and stir zone has been found. Tensile tests revealed, that the localization of deformation was obtained in each weld in the area of the biggest average grain size. For dissimilar welds from deformed and undeformed samples a gradient change in microstructure and microhardness was obtained on the cross-section of the welds.

Microstructure and mechanical behavior of similar and dissimilar AA2024 and AA7039 friction stir welds

In this work, similar and dissimilar friction stir welds of AA2024 and AA7039 were formed using optimized process parameters and truncated threaded tool. Characterization of weld joints for mechanical and microstructural properties was performed by tensile test, micro hardness test, optical microscopy, scanning electron microscopy, and energy dispersive spectrometry. The tensile strength of similar joints was higher than dissimilar joints despite lower microhardness of former. Fracture of FSW joints was found to be started by the fracture of strengthening precipitate θ or η or both in the region of tensile fracture. Dissimilar joints and similar joints of AA7039 exhibited ductile fracture mode while similar joints of AA2024 showed brittle fracture mode.

Similar and dissimilar welding effect on the mechanical properties of 5383 H34, 5754 H34 and 6005 T6 aluminum alloys

ABSTRACT Aluminum alloys are not covered by their specific weight. Each class of aluminum alloy presents a set of properties that are favorable to a given function in the same product, just as the alloys may be present in the same vehicle. However, it is necessary to know the changes in the mechanical properties that occur with the union process of these aluminum alloys. The objective of this study was to evaluate the mechanical and morphological properties of alloys 5383 H34, 5754 H34 and 6005 T6 similarly welded and dissimilar by the MIG process. Six combinations of these alloys were characterized by mechanical tensile, folding and Vickers micro-hardness tests, as well as scanning electron microscopy (SEM) and optical microscopy (OM). Among the results obtained, a decrease in tensile strength was observed for all welded alloys. In addition, the microhardness was affected in the melt line, in the weld bead and in the HAZ (heat affected zone). The main causes of the reduction of the mechanical resistance of the welded alloys were the grain growth and the precipitate dissolution. The data obtained in this study contribute in a very positive way to the development and dimensioning of new projects and technologies involving aluminum alloys.

Study of microstructure and mechanical properties of aluminium alloy (AA-6351-T6) using friction stir welding

The current study investigates the effect of welding speed on the mechanical and microstructural properties in similar friction stir welding of Aluminium Alloy (AA-6351-T6). The contribution of intense plastic deformation and high-temperature exposure within the stirred zone during friction stir welding results in recrystallization and development of texture within the stirred zone and precipitate dissolution and coarsening within and around the stirred zone. Based on micro-structural characterization of grains and precipitates, three distinct zones, stirred (nugget) zone, thermo-mechanically affected zone (TMAZ), and heat-affected zone (HAZ).The micro-structural changes in various zones have significant effect on post weld mechanical properties.

Effect of welding speeds on microstructure and mechanical properties of dissimilar friction stir welding of AA7075 and AA5083 alloy

Effect of welding speeds is studied in Friction stir welding (FSW) using cylindrical tool for the welding of Aluminum 7075 and 5083 alloys. Sound joint of similar and dissimilar FSW were obtained by use of 20 and 45 mm/min welding speed. The temperature distribution on entire weld zone influences the grain size of FSW. The grain size at different zones, affect the properties of FSW. This study, observed that the dissimilar joining of AA7075 and AA5083 exhibits better strength at the welding speed of 20 mm/min. Similar FSW achieved better strength at 45 mm/min welding speeds. Dissimilar welding required higher heat input as compare to similar welding.