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Presently, the materials used in light combat aircraft structures are aluminium alloys and composites. These structures are joined together through riveted joints. The weight of these rivets for the entire aircraft is nearly one ton. In addition to weight, the riveted connection requires a lot of tools, equipments, fixtures and manpower, which makes it an expensive and time-consuming process. Moreover, Al alloy is also welded using tungsten inert gas (TIG) welding process by proper control of process parameters. This process has limitations such as porosity, alloy segregation and hot cracking. To overcome the above limitations, an alternative technology is required. One such technology is friction stir welding (FSW), which can be successfully applied for welding of aluminium alloy in LCA structures. Therefore, this paper aims to compare the load carrying capabilities of FSW joints with TIG welded and riveted joints.

FSW joints and TIG welded joints were fabricated using optimized process parameters, followed by riveted joints using standard shop floor practice in the butt and lap joint configurations.

The load-carrying capabilities of FSW joints are superior than those of other joints. FSW joints exhibited 75 per cent higher load-carrying capability compared to the riveted joints and TIG-welded joints.

From this investigation, it is inferred that the FSW joint is suitable for the replacement of riveted joints in LCA and TIG-welded joints.

Friction stir butt joints exhibited 75 per cent higher load-carrying capability than riveted butt joints. Friction stir welded lap joints showed 70 per cent higher load-carrying capability than the riveted lap joints. Friction stir butt joints yielded 41 per cent higher breaking load capabilities than the TIG-welded butt joints. Moreover, Friction stir lap weld joints have 57 per cent more load-carrying capabilities than the TIG-welded lap joints.

The primary objective of this investigation is to optimize the constricted arc tungsten inert gas (CA-TIG) welding parameters specifically welding current (WC), arc constriction current (ACC), ACC frequency (ACCF) and CA traverse speed to maximize the tensile properties of thin Inconel 718 sheets (2 mm thick) using a statistical technique of response surface methodology and desirability function for gas turbine engine applications.

The four factor – five level central composite design (4 × 5 – CCD) matrix pertaining to the minimum number of experiments was chosen in this investigation for designing the experimental matrix. The techniques of numerical and graphical optimization were used to find the optimal conditions of CA-TIG welding parameters.

The thin sheets of Inconel 718 (2 mm thick) can be welded successfully using CA-TIG welding process without any defects. The joints welded using optimized conditions of CA-TIG welding parameters showed maximum of 99.20%, 94.45% and 73.5% of base metal tensile strength, yield strength and elongation.

The joints made using optimized CA-TIG welding parameters disclosed 99.20% joint efficiency which is comparatively 20%–30% superior than conventional TIG welding process and comparable to costly electron beam welding and laser beam welding processes. The parametric mathematical equations were designed to predict the tensile properties of Inconel 718 joints accurately with a confidence level of 95% and less than 4.5% error. The mathematical relationships were also developed to predict the tensile properties of joints from the grain size (secondary dendritic arm spacing-SDAS) of fusion zone microstructure.

Titanium (Ti) alloys are in high demand in manufacturing industries all over the world. The property like high strength to weight ratio makes Ti alloys highly recommended for aerospace industries. Ti alloys possess good weldability, and therefore, they were extensively investigated with regard to strength and metallurgical properties of welded joint. This study aims to deal with the analysis of strength and microstructural changes in Ti-6Al-4V (Grade 5) alloy after tungsten inert gas (TIG) welding.

Two pair of Ti alloy plates were welded in two different voltages, i.e. 24 and 28 V, with keeping the current constant, i.e. 80 A It was a random selection of current and voltage values to check the performance of welded material. Both the welded plates were undergone through some mechanical property analysis like impact test, tensile test and hardness test. In addition, the microstructure of the welded joints was also analyzed.

It was found that hardness and tensile properties gets improved with an increment in voltage, but this effect was reverse for impact toughness. A good corroboration between microstructure and mechanical properties, such as tensile strength, hardness and toughness, was reported in this work. Heat distribution in both the welded plates was simulated through ANSYS software to check the temperature contour in the plates.

A good corroboration between microstructure and mechanical properties, such as tensile strength, hardness and toughness, was reported in this study.

Vibratory weld conditioning parameters have a great influence on the improvement of mechanical properties of weld connections. The purpose of this paper is to understand the influence of vibratory weld conditioning on the mechanical and microstructural characterization of aluminum 5052 alloy weldments. An attempt is made to understand the effect of the vibratory tungsten inert gas (TIG) welding process parameters on the hardness, ultimate tensile strength and microstructure of Al 5052-H32 alloy weldments.

Aluminum 5052 H32 specimens are welded at different combinations of vibromotor voltage inputs and time of vibrations. Voltage input is varied from 50 to 230 V at an interval of 10 V. At each voltage input to the vibromotor, there are three levels of time of vibration, i.e. 80, 90 and 100 s. The vibratory TIG-welded specimens are tested for their mechanical and microstructural properties.

The results indicate that the mechanical properties of aluminum alloy weld connections improved by increasing voltage input up to 160 V. Also, it has been observed that by increasing vibromotor voltage input beyond 160 V, mechanical properties were reduced significantly. It is also found that vibration time has less influence on the mechanical properties of weld connections. Improvement in hardness and ultimate tensile strength of vibratory welded joints is 16 and 14%, respectively, when compared without vibration, i.e. normal weld conditions. Average grain size is measured as per ASTM E 112–96. Average grain size is in the case of 0, 120, 160 and 230 is 20.709, 17.99, 16.57 and 20.8086 µm, respectively.

Novel vibratory TIG welded joints are prepared. Mechanical and micro-structural properties are tested.

The purpose of this paper is to predict and optimize the width of heat affected zone (HAZ) with better mechanical properties using suitable welding process and parameters for the fabrication of jet blast deflector (JBD) (high strength low alloy material of grade A588-B was used for fabrication) so that the JBD can sustain high exhaust parameters, because there are different welding zones formed due to the rapid cooling of weld metals. Out of the various zones of welding, HAZ remains the weakest zone in the entire weldment.

The present work describes the modeling, simulation, Modeling of three-dimensional plate and mess generation process are carried out using ICEM CFD software. FLUENT 16.0 software is used for ANSYS simulation where various models are used for analysis and results are validated with the experimental outcomes. High strength low alloy plates are welded by using shielded metal arc welding and tungsten inert gas (TIG) welding processes with two different electrodes. Optical microscopy and scanning electron microscopy were used for metallurgical study. The mechanical properties were evaluated by tensile strength test, vickers microhardness test and impact test. The corrosion resistance was evaluated by performing the potentiodynamic polarization test.

The present study indicated for better mechanical properties and improved corrosion resistance for TIG welded joints with type 308 L filler.

In aeronautical, defense, space and research organizations.

It can be shown from the scanning electron microscope technique that sound weld joint is produced with very good mechanical properties and joint also showed better corrosion resistance.

Stainless steel is one of the most important elements in structural design and application, and due to its excellent properties, it is widely used in industries for conventional structural engineering applications, such as thermal power plants, nuclear power plants, civil constructions, etc. (Mishra et al., 2014). A traditional tensile testing machine cannot determine the transversal stress–strain curves (Olden, 2002, 2013).

In the present study, identical mild steel specimen parts are welded at different intervals and then subjected to tensile loading. Welding is carried along the length of the specimen. Induced stresses are determined at the welded intervals and the stress–strain curve is obtained.

By considering the temperature of the weld at the interface, thermal stresses are determined. Brinell hardness number is determined at the interface and the base metal. Also, the change in the hardness at the heat-affected zone (HAZ) is found. Validation is carried out by comparing the results with the original stress–strain curve.

In the HAZ, there is a drop in the hardness number, which means that there is a change in the material property due to welding. The thermal stresses which develop at the interface can also play a very important role for property change. Results show that the stress developed due to the rise in temperature is lesser than that of normal stresses.

The purpose of this study is to conduct gas tungsten arc dissimilar welding of AISI 304 stainless steel and low carbon steel within a process window so as to investigate the effects of current, speed and gas flow rate (GFR) on the microstructure and mechanical properties of the weldments.

The welding experiment was carried out at different combinations of parameters using WN-250S Kaierda electric welding machine. A combination of scanning electron microscopy and energy dispersive X-ray spectroscopy was used to examine the microstructure of the weldments. Micro-hardness and tensile tests were performed using Vickers hardness tester and Instron universal testing machine, respectively. ANOVA was used to analyze the significance of the parameters on the mechanical properties.

The microstructure of the weld region is characterized with dendritic structure with the existence of ferrite and austenite phases. The utilized parameters show significant effects on the ultimate tensile strength (UTS) of the weldments. The current and GFR were found to be the most and least significant factors, respectively. Both the grain size and weld penetration contributed to the UTS of the weldments. The UTS (427-886 MPa) increased with decreasing current and welding speed. In all samples, the weld region exhibited higher hardness (297-396 HV) than the HAZ in the base metals (maximum of 223 Â ± 6 HV). All the three factors show significant effect with the welding speed contributing mostly to the hardness of the weld region.

The parametric combination that gives the optimum mechanical performance of the dissimilar gas tungsten arc weldments of AISI 304 stainless steel and low carbon steel was established.

Dissimilar joining of austenitic stainless steels and ferritic steels is a challenging task and has a wide range of applications due to its excellent mechanical and thermal characteristics. They are joined mostly by using conventional modes. In the current investigation, the study and optimization of hot wire TIG welding parameters was carried out.

These parameters will govern the desired characteristics of the joint. Solutions were found out through multi-response optimization by using response surface methodology and single response optimization using particle swarm optimization.

Optimized input welding parameters that were achieved are electrode current 180 amps, wire feed rate 1870 mm/min and hot wire current 98 amps and the optimized UTS is 665.45 MPa. The results from PSO were compared with RSM and the optimized input welding parameters for the electrode current, hot wire current and wire feed rate exhibited maximum ultimate tensile strength which were also confirmed from response and contour plots.

Sensitivity analysis was also performed to understand the effect of each individual parameters on the response. Microstructure features were evaluated for the joints and was found that the characteristics are within the desired criteria.

It is a great privilege and honour to be asked to deliver the annual Chester Beatty Lecture, particularly in the presence of Mr Chester Beatty himself. The theme of these Lectures is “metals in the service of mankind” and, in this respect, the material which I will be covering in this lecture has been serving mankind for a relatively short time compared with other metals such as copper, zinc, iron, etc. Titanium is a metal which has only achieved direct engineering usage, as distinct from some minor applications as a strengthening alloy in other metals, since the Second World War. Its rise in importance for structural purposes has been very rapid and the purpose of this paper is to outline its history, to indicate the reasons why designers are so impressed by its potential, and to give some examples of present and future applications.

Following a series of acquisitions ESAB is consolidating its efforts, but increasingly it will come to depend on welding automation for growth.