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A three-dimensional coupled model in a Eulerian framework has been developed in COMSOL Multiphysics software and used to study the complex phenomena of thermal and material flow during the friction stir welding (FSW) process. The moving heat source (tool) effect is modelled using a coordinate transformation. The frictional heat as a function of temperature-dependent yield strength of AA2219-T87 material and the deformation energy of plasticized material flow are considered. Further, the plasticized material flow around the rotating tool is modelled as non-Newtonian fluid using partial-sticking/sliding boundary condition with a computed slip factor (δ) at the workpiece-tool material interfaces. The coupled Eulerian model prediction accuracy has been validated against the experimental weldment zones and found a good agreement in terms of the shape and size. Subsequently, the effects of tool-pin profiles (cylindrical and conical) on thermal distribution, material flow, shear strain rates, thermal histories, and weldment zones were studied. It is found that the maximum temperatures, material flow velocities, and shear strain rates are low with the conical tool pin in contrast to the cylindrical one, and it is partly attributed to increased mixing of shoulder and pin-driven material flow around the rotating tool, which in turn decreased the size of weldment zones. Also, the maximum temperatures, material flow velocities, and shear strain rates on the advancing side are higher than those of the retreating side. Therefore, it is suggested to use the CFD model to design the FSW process and tool parameters in a cost-effective way in contrast to the tedious experimental route.

The purpose of this study is to examine the projectile penetration resistance of the base metal and heat-affected zones of armor steel weldments. To ensure the proper quality of armor steel welded joints and associated ballistic protection, it is important to find the optimum heat input for armor steel welding. A total of two armor steel weldments made at heat inputs of 1.29 kJ/mm and 1.55 kJ/mm were tested for ballistic protection performance. The GMAW welding carried out employing a robot-controlled process. Owing to a higher ballistic limit, the heat-affected zone (HAZ) of the 1.29 kJ/mm weldment was found to be more resistant to projectile penetration than that of the 1.55 kJ/mm weldment. The ballistic performance of the weldments was determined by analyzing the microstructure of weldment heat-affected zones, the hardness gradients across the weldments and the thermal history of the welding heat inputs considered. The result showed that the ballistic resistance of heat affected zone exist as the heat input was decreased on 1.29 kJ/mm. It was found that 1.55 kJ/mm does not have ballistic resistance.

Selecting the most effective welding settings impacts mechanical strength and weld quality, with parameters like current, voltage, and speed playing pivotal roles. The mechanical part encompasses material properties, welding process variables, and structural integrity, all contributing to the overall weld quality and strength. By integrating these mechanical factors with predictive modelling, a comprehensive understanding of weld performance can be achieved, enabling optimized welding settings and enhanced weld quality assurance. This study assesses and compares machine learning algorithms such as a random tree, random forest, and C4.5 to determine their predictive capability regarding the tensile strength in Monel 400 Weldments. By utilizing a dataset comprising 32 instances with attributes like Current, Voltage, and Speed, models were developed and assessed using K-Fold cross-validation. Among these algorithms, the random tree models emerge as the most proficient in accurately predicting the tensile strength for Monel 400 Weldments through classification ML techniques. Similarly, regression algorithms have been deployed to assess the dataset by varying the train-test split ratio and gradient boosting, which exhibited superior performance with a higher R 2 value of 0.99. Both random tree and Gradient boosting algorithms have commonly been recommended, with current being the most influential factor affecting tensile strength.

Ultrasonic signal classification of defects in weldment, in automatic fashion, is an active area of research and many pattern recognition approaches have been developed to classify ultrasonic signals correctly. However, most of the developed algorithms depend on some statistical or signal processing techniques to extract the suitable features for them. In this work, data driven approaches are used to train the neural network for defect classification without extracting any feature from ultrasonic signals. Firstly, the performance of single hidden layer neural network was evaluated as almost all the prior works have applied it for classification then its performance was compared with deep neural network with drop out regularization. The results demonstrate that given deep neural network architecture is more robust and the network can classify defects with high accuracy without extracting any feature from ultrasonic signals.

This study examined the structural integrity and residual stresses of dissimilar welding between super duplex stainless steel (sDSS 2507) and Inconel 625 using ER2594 filler wire and gas tungsten arc welding (GTAW). The mechanical properties of the weldments were assessed through various tests, such as hardness, impact, and transverse tensile tests, at different heat inputs, i.e., 0.73 and 1.4 kJ/mm. Optical and scanning electron microscopes with energy-dispersive spectroscopy studied base metal and weld zone/interface microstructure evolution. Additionally, the study analyzed the effects of heat input on residual stresses and evaluated those stresses using deep-hole drilling methods. In the weld metal and IN625 HAZ, Nb-rich Laves phases were irregularly distributed. Line mapping and electron probe micro-analysis showed Cr, Mo, and Nb enrichment, which precipitated as segregation at the weld interface. EDS studies also demonstrated Mo- and Nb-rich phases segregating in the inter-dendritic region of the weld zone, with the highest weight percentage at high heat input weldment. The Nb-rich Laves phases in the inter-dendritic regions reduced mechanical performance, and both weldments fractured at the weld zone during tensile testing. High heat input increased residual longitudinal and transverse stresses by 16 and 19%, respectively.

The aim of this work is thermomechanical and experimental study on the effect of tool rotational and traverse speed on friction stir welding of PMMA T-joint. Development of temperature profile in the joint region was measured and compared with the results of thermomechanical modeling and tensile. Moreover, flexural and hardness tests were carried out for all samples. The results show that the highest tensile (~ 84% PMMA strength) and flexural (~ 93% PMMA strength) strength can be obtained at a 1600 rpm tool rotational speed and 25 mm/min traverse velocity. In these parameters, smooth surface and defect-free joint were produced. Fractographic studies of weldments indicate fracturing in brittle mode. Hackled regions in the tensile test on fracture surface and crack branches in flexural fracture surface were observed, showing that the PMMA shrinkage holes play crack initiation role in all of these phenomena. According to the results, the lowest hardness of stir zone was on the joint which was welded with 1600 rpm and 25 mm/min speed (75.5 Shore D) and highest hardness of stir zone was on the joint that was welded with 1000 rpm and 50 mm/min speed (85.6 Shore D).

Friction stir welding (FSW) system was pondered to generate weld joints with favourable strengths. Owed to the least set of process parameters are to be monitored thru welding process, this green welding method contains visible benefits upon further welding methods. This work focuses on the effect of process parameters implied during the process of joining and orientation of the tool pin profile towards the enhancing the mechanical properties of the dissimilar weldments made with AA6082 - AA5083 aluminium alloys. This paper covers the comparative study of weld tensile properties of the weldments made by utilizing hybrid and conventional tool pin profiles. This paper also covers the optimization of the weld parameters using Taguchi method. The UTS of hybrid tool pin weldments ranges from 160.05 MPa to 213.46 MPa.

This paper deals for the first time with the effects of additional cooling medium by submerging underwater on the feasibility of dissimilar bond formation between aluminum and steel in solid-state during friction-stir welding (FSW) process. Sheets of AA5083 Al-Mg aluminum alloy and A441 AISI steel are considered into the investigation with a butt-joint design and immersing under the cooling water mediums with three different temperatures of 0, 25, and 50 °C besides ambient processing in the air atmosphere without excessive cooling. Thermo-mechanical cycles during the FSW process are monitored as well as the soundness of produced dissimilar weldments in terms of materials inter-mixing, grain structural features, possible phase transformations, mechanical property, and subsequent fracture behavior. The results showed that by increasing the cooling capability of the environment and employing the low-temperature water as the submerged medium, the peak temperature during the FSW process is continuously reduced down to ~ 400 °C. The impact influence is on suppressing the dissimilar metals inter-mixing as well as the grain structural coarsening during dynamic recrystallization and the kinetics of intermetallic compound (IMC) formation. By decreasing the peak temperature and submerging under cooling medium, the thickness of the IMC layer at the interface is continuously decreased as affected the indentation hardness resistance and subsequent transverse tensile behavior. All samples are failed at the joint interface along the IMC layer, with an excellent combination of tensile strength (~ 310 MPa) and elongation (~ 13%) for the room temperature cooling medium, as the optimum condition based on the evolution of experimental trends. The dominant flow mechanism as plastic constraint induced some fractural aspects of ductile in dimpler form or catastrophic on the corresponding failed portion depending on the joint brittleness.

PurposeAn experimental investigation for developing structure-property correlations of hot-rolled E410 steels with different carbon contents, i.e. 0.04wt.%C and 0.17wt.%C metal active gas (MAG) and cold metal transfer (CMT)-MAG weldments was undertaken.Design/methodology/approachMechanical properties and microstructure of MAG and CMT-MAG weldments of two E410 steels with varying content of carbon were compared using standardized mechanical testing procedures, and conventional microscopy.Findings0.04wt.%C steel had strained ferritic and cementite sub-structures in blocky shape and large dislocation density, while 0.17wt.%C steel consisted of pearlite and polygonal ductile ferrite. This effected yield strength (YS), and microhardness being larger in 0.04wt.%C steel, %elongation being larger in 0.17wt.%C steel. Weldments of both E410 steels obtained with CMT-MAG performed better than MAG in terms of YS, ultimate tensile strength (UTS), %elongation, and toughness. It was due to low heat input of CMT-MAG that resulted in refinement of weld metal, and subzones of heat affected zone (HAZ).Originality/valueA substantial improvement in YS (∼9%), %elongation (∼38%), and room temperature impact toughness (∼29%) of 0.04wt.%C E410 steel is achieved with CMT-MAG over MAG welding. Almost ∼10, ∼12.5, and ∼16% increment in YS, %elongation, and toughness of 0.17wt.%C E410 steel is observed with CMT-MAG. Relatively low heat input of CMT-MAG leads to development of fine Widmanstätten and acicular ferrite in weld metal and microstructural refinement in HAZ subzones with nearly similar characteristics of base metal.

Welding of Inconel 617 (IN617) alloy and austenitic 304L SS steel has been attempted using the autogenous Laser Beam Welding (LBW) process. Characterization of dissimilar weldments was performed on either side of the fusion boundaries. The metallographic results showed that the inhomogeneous microstructure formation for weld metal contained columnar and cellular dendrites near the interface, whilst the columnar, cellular and equiaxed types of dendrites were in the weld centre. The energy dispersive spectroscopy (EDS) and electron probe microanalysis (EPMA) studies revealed the white layer near the interface on both sides of the fusion line, as well as a significant change in the concentration of alloying elements (Fe, Cr, Ni, Co, and Mo). The weld metal accompanied by Cr, Ti and Mo precipitates evolved in the inter-dendritic spaces. The Cr and Mo-rich M23C6 and Mo-rich M6C phases in IN617 heat-affected zone (HAZ) were found in SEM/EDS and EPMA studies. The 304L SS side showed a distinct HAZ, whilst on the IN617 side, no distinct HAZ was seen. Samples were prepared from the dissimilar weldments to evaluate their mechanical properties, such as tensile strength and hardness. The microhardness plot showed the non-uniformity in hardness along the weldments. The weld metal hardness was 253 ± 10 HV. The tensile test of the welded joint results was compared with the base metals. The tested results exhibited that the failure of the specimen from 304L SS base metal (BM) or from weld metal with tensile strength was marginally lower than the Inconel 617 base metal but significantly higher than the 304L SS BM. The fracture surface study revealed the presence of Mo and Cr segregation in inter-dendritic spaces, which impoverished the tensile properties. The order of impact toughness was measured as follows: 304L SS BM > 304L SS HAZ > IN617 BM > weld metal > IN617 HAZ. The IN617 HAZ was recognised as the weakest area of the weldments in terms of impact strength. The welded joint was considered safe for AUSC application because the stress-rupture properties were evaluated in between base metals data.