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This paper aims to anticipate the possible development direction of WAAM. For large-scale and complex components, the material loss and cycle time of wire arc additive manufacturing (WAAM) are lower than those of conventional manufacturing. However, the high-precision WAAM currently requires longer cycle times for correcting dimensional errors. Therefore, new technologies need to be developed to achieve high-precision and high-efficiency WAAM.

This paper analyses the innovations in high-precision WAAM in the past five years from a mechanistic point of view.

Controlling heat to improve precision is an effective method. Methods of heat control include reducing the amount of heat entering the deposited interlayer or transferring the accumulated heat out of the interlayer in time. Based on this, an effective and highly precise WAAM is achievable in combination with multi-scale sensors and a complete expert system.

Therefore, a development direction for intelligent WAAM is proposed. Using the optimised process parameters based on machine learning, adjusting the parameters according to the sensors’ in-process feedback, achieving heat control and high precision manufacturing.

This study aims to describe the effects of capillary forces or action, viscosity, gravity and inertia via the computational fluid dynamics (CFD) analysis. The study also includes distribution of the binder droplet over the powder bed after interacting from different heights.

Additive manufacturing (AM) has revolutionized many industries. Binder jetting (BJT) is a powder-based AM method that enables the production of complex components for a wide range of applications. The pre-densification interaction of binder and powder is vital among various parameters that can affect the BJT performance. In this study, BJT process is studied for the binder interaction with the powder bed of SS316L. The effect of the droplet-powder distance is thoroughly analysed. Two different droplet heights are considered, namely, h1 (zero) and h2 (9.89 mm).

The capillary and inertial effects are predominant, as the distance affects these parameters significantly. The binder spreading and penetration depth onto the powder bed is influenced directly by the distance of the binder droplet. The former increases with an increase in latter. The binder distribution over the powder bed, whether uniform or not, is studied by the stream traces. The penetration depth of the binder was also observed along the cross-section of the powder bed through the same.

In this work, the authors have developed a more accurate representative discrete element method of the powder bed and CFD analysis of binder droplet spreading and penetration inside the powder bed using Flow-3D. Moreover, the importance of the splashing due to the binder’s droplet height is observed. If splashing occurs, it will produce distortion in the powder, resulting in a void in the final part.

In binder jetting, the interaction between the liquid binder droplets and the powder particles defines the shape of the printed primitives. The purpose of this study is to explore the interaction of the relative size of powder particles and binder droplets and the subsequent effects on macro-scale part properties.

The effects of different particle size distribution (5–25 µm and 15–45 µm) of stainless steel 316 L powders and droplet sizes (10 and 30 pL) on part density, shrinkage, mechanical strength, pore morphology and distribution are investigated. Experimental samples were fabricated in two different layer thicknesses (50 and 100 µm).

While 15–45 µm samples demonstrated higher green density (53.10 ± 0.25%) than 5–25 µm samples (50.31 ± 1.06%), higher sintered densities were achieved in 5–25 µm samples (70.60 ± 6.18%) compared to 15–45 µm samples (65.23 ± 3.24%). Samples of 5–25 µm also demonstrated superior ultimate tensile strength (94.66 ± 25.92 MPa) compared to 15–45 µm samples (39.34 ± 7.33 MPa). Droplet size effects were found to be negligible on both green and sintered densities; however, specimens printed with 10-pL droplets had higher ultimate tensile strength (79.70 ± 42.31 MPa) compared to those made from 30-pL droplets (54.29 ± 23.35 MPa).

To the best of the authors’ knowledge, this paper details the first report of the combined effects of different particle size distribution with different binder droplet sizes on the part macro-scale properties. The results can inform appropriate process parameters to achieve desired final part properties.

Personal Protective Equipment plays an inevitable part in the current scenario of pandemics in the world. A novel coronavirus, Severe Acute Respiratory Syndrome-Corona Virus-2 (SARS-Cov 2), began as an outbreak of pneumonia in Wuhan, China, in late December 2019, and quickly spread worldwide. It quickly escalated into an international public health crisis. This opened up the high demand for the innovation and research of new materials in the Personal Protective Equipment industry.

PubMed, Embase and Google Scholar were searched for relevant literature regarding personal protective equipment and the information was organized in a systematic way.

There are no adequate number of studies taken up in the field of use of textiles in medical applications especially with PPEs.

This structured review will generate a sense of the significance of using PPE for controlling pandemics and also awaken need for additional research and innovations in this area.

The authorities of the management should take timely intervention in choosing the right material for their PPE in their hospitals. Hence health care professionals teams have an inevitable role in preventing the adverse environmental impact due to the inadvertent disposal of PPEs.

There is a lack of systematic way of disposing contaminated single-use face masks in a safe, environmentally acceptable manner. The dumping of single-use PPE in domestic garbage has had an adverse effect on the environment. Mismanaged plastic waste endangers the health of ecosystems by polluting marine and terrestrial environments, posing a significant risk of ingestion or injury to animals and contaminating habitats.

This review article provides an in-depth review of the use of different materials in PPE and challenges regarding its long-term use and implications on the environment.

This study aims to demonstrate a modified wire arc additive manufacturing (AM) named non-transferring arc and wire AM (NTA-WAM). Here, the build plate has no electrical arc attachment, and the system’s arc is ignited between tungsten electrode and filler wire.

The effect of various deposition conditions (welding voltage, travel speed and wire feed speed [WFS]) on bead characteristics is studied through response surface methodology (RSM). Under optimum deposition condition, a single-bead and thin-layered part is fabricated and subjected to microstructural, tensile testing and X-ray diffraction study. Moreover, bulk texture analysis has been carried out to illustrate the effect of thermal cycles and tensile-induced deformations on fibre texture evolutions.

RSM illustrates WFS as a crucial deposition parameter that suitably monitors bead width, height, penetration depth, dilution, contact angle and microhardness. The ferritic (acicular and polygonal) and lath bainitic microstructure is transformed into ferrite and pearlitic micrographs with increasing deposition layers. It is attributed to a reduced cooling rate with increased depositions. Mechanical testing exhibits high tensile strength and ductility, which is primarily due to compressive residual stress and lattice strain development. In deposits, ϒ-fibre evolution is more resilient due to the continuous recrystallisation process after each successive deposition. Tensile-induced deformation mostly favours ζ and ε-fibre development due to high strain accumulations.

This modified electrode arrangement in NTA-WAM suitably reduces spatter and bead height deviation. Low penetration depth and dilution denote a reduction in heat input that enhances the cooling rate.

The criteria importance through intercriteria correlation (CRITIC) and range of value (ROV) combined methods were used to determine a single index for all multiple responses.

This paper used cold metal transfer (CMT) and pulse metal-inert gas (MIG) welding processes to study the weld-on-bead geometry of AA2099-T86 alloy. This study used Taguchi's approach to find the optimal setting of the input welding parameters. The welding current, welding speed and contact-tip-to workpiece distance were the input welding parameters for finding the output responses, i.e. weld penetration, dilution and heat input. The L9 orthogonal array of Taguchi's approach was used to find out the optimal setting of the input parameters.

The optimal input welding parameters were determined with combined output responses. The predicted optimum welding input parameters were validated through confirmation tests. Analysis of variance showed that welding speed is the most influential factor in determining the weld bead geometry of the CMT and pulse MIG welding techniques.

The heat input and weld bead geometry are compared in both welding processes. The CMT welding samples show superior defect-free weld beads than pulse MIG welding due to lesser heat input and lesser dilution.

The COVID-19 pandemic had a huge impact on people's lives, air travel and tourism. The authors explored travelers' perceptions of COVID rapid antigen tests before boarding aircraft, willingness to fly and the precautionary actions for safe air travel.

All the participants were asked to complete the survey while reflecting on their experiences of air travel during this COVID-19 pandemic. The questionnaire consisted of demographic information of the participants and air travel preferences during pandemic. The survey was conducted through Google Form in both English and Arabic language. The link was shared through emails and WhatsApp.

In this survey, majority had willingness to fly during pandemic. 45.2% preferred to undergo rapid test before boarding, while 41.9% refused owing to no added benefit (23.8%) and nasal discomfort (9.3%) among others. The best indicators to resume safe air travel were COVID-19 vaccination (80.4%), wearing face mask during flying hours (70.8%) and maintain social distancing with aircraft seating (49.6%).

The findings of the current survey could help the organizations and the biosecurity authorities to act and support accordingly and thus reduce passenger anxiety about resuming the flights, thereby increasing willingness to fly and preparing oneself and the aviation industry for future pandemics.

The findings of the current survey could help the organizations and the biosecurity authorities to act and support accordingly and thus reduce passenger anxiety about resuming the flights, thereby increasing willingness to fly, and preparing oneself and the aviation industry for future pandemics.

The purpose of this study is to reduce the cracks, pores and unfused defects in arc welding, improve the crystalline structure of the weld, refine its grains and improve the mechanical properties.

Taking E690 marine steel as the research object, the experiment adopts a new process method of laser forging coupled arc welding. Welding for comparative experiments. Experiments show that the “V”-shaped groove arc welding process has a larger fusion area, but has pores, the arc current is 168 A, the arc voltage is 28 V and the welding speed is 600 mm/min.

It can be seen from tensile tests that the coupling welding process has the highest tensile strength and yield strength, 872 MPa and 692 MPa, respectively, and the fracture elongation is 29.29%. The single-beam laser forging coupled arc welding process has a distance of laser and wire of 6–8 mm, a laser wavelength of 1,064 nm and the highest weld fusion ratio. The microhardness test shows that the average hardness of single-beam laser forging in the weld zone is 487.54 HV, which is 10.30% higher than that of arc welding. The average hardness in the fusion zone is 788.08 HV, which is 14.52% higher than that of the arc welding process.

The originality of the experiment: proposed a new process method of coupling arc repair for offshore steel forging; adopted a new process method of simultaneous coupling of single-beam short-pulse laser, double-beam short-pulse laser and arc welding; and obtained effect of pulsed laser and arc composite repair on porosity and fusion of E690 marine steel welds.

An 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.

Mechanical 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.

0.04wt.%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).

A 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.

The purpose of this study is to explore the mist-air film cooling performance on a three-dimensional (3-D) flat plate. In mist-air film cooling technique, a small amount of water droplets is injected along with the coolant air. The objective is to study the influence of shape of the coolant hole and operating conditions on the cooling effectiveness.

In this study, 3-D numerical simulations are performed. To simulate the mist-air film cooling over a flat plate, air is considered as a continuous phase and mist is considered as a discrete phase. Turbulence in the flow is accounted using Reynolds averaged Navier–Stokes equation and is modeled using k–e model with enhanced wall treatment.

The results of this study show that, for cylindrical coolant hole, coolant with 5% mist concentration is not effective for mainstream temperatures above 600 K, whereas for fan-shaped hole, even 2% mist concentration has shown significant impact on cooling effectiveness for temperatures up to 1,000 K. For given mist-air coolant flow conditions, different trend in effectiveness is observed for cylindrical and fan-shaped coolant hole with respect to main stream temperature.

This study is limited to a flat plate geometry with single coolant hole.

The motivation of this study comes from the requirement of high efficiency cooling techniques for cooling of gas turbine blades. This study aims to study the performance of mist-air film cooling at different geometric and operating conditions.

The originality of this study lies in studying the effect of parameters such as mist concentration, droplet size and blowing ratio on cooling performance, particularly at high mainstream temperatures. In addition, a systematic performance comparison is presented between the cylindrical and fan-shaped cooling hole geometries.