Springer Science and Business Media LLC

The quality and load-carrying capacity of weldments mainly depends on selecting suitable levels of input welding parameters. Current research intends to optimize input parameters, viz. current and welding speed, for various weld characteristics like penetration depth, weld width, weld bead hardness, and HAZ hardness for tungsten inert gas welded SS202. Experiments were organized using the response surface methodology’s central composite face-centered design approach. The experimental findings were analyzed using ANOVA, and regression equations were developed for all output parameters. Higher current and slower welding speeds increase penetration depth and weld width, and vice versa. The greatest penetration depth (1.764 mm), minimum weld width (4.097 mm), maximum weld bead hardness (347 Hv), and heat-affected zone hardness (302 Hv) were achieved with the optimized input values of welding current and speed, which were 103 A and 5 mm/sec, respectively. A confirmation test revealed that the predicted values aligned well with experimental results.

In this paper a modular generic architecture for cyber-physical systems based on free open software components is presented. The architecture is implemented over inexpensive components frequently found in information and communication technology contexts. More specifically, the robot operating system middleware abstracts communication among multiple networked modules, whereas the Docker lightweight virtualization container is proposed to wrap up software modules. Focus is on mobile robotics in production systems and industrial automation environments. Actually, an automated guided vehicle problem is demonstrated by means of a proof of concept aimed at industrial automation applications illustrating the potential of the proposed architecture and its implementation, built with low cost hardware modules.

Metal binder jetting (MBJ) is an additive manufacturing (AM) technology split into two process steps: printing and sintering. Firstly, product is built up layer-by-layer by the selective deposition of a binder agent on a powder bed. Secondly, a thermal treatment (sintering) consolidates the metal structure. MBJ is currently becoming more and more attractive on the reason of high potential scalability, cost-effective production and wide range of available material feedstocks. However, the transition towards industrial scale production is restrained by the critical control of dimensional and geometrical precision of parts after sintering operation. In fact, product geometry is affected by anisotropic dimensional change or even shape distortion. This study aims at investigating the dimensional and geometrical precision of through holes. Three sample geometries were designed, having a through hole with axis perpendicular to the building direction and located at different levels along sample height. Samples were measured by a coordinate measuring machine before and after sintering, in order to assess the shrinkage and any shape change. Results highlight the inhomogeneous volumetric and linear shrinkage of the three geometries, which is influenced by the printing position in the building plane. A macroscopic deformation of parallelepiped geometry was also evidenced, caused by the superposition of layer shifting originated on printing, and by the frictional forces between sample surface and alumina support during sintering. Such distortion significantly affects the shrinkage and form error of holes.

Metal additive manufacturing is the most effective way to manufacture short and complex components with near-net shapes but the problem with this process is time-consuming and costly. Wire arc additive manufacturing (WAAM) has become a promising approach for manufacturing large-scale structures. WAAM is widely used because of its low manufacturing cost and less fabrication time. For the last two decades, researchers have been doing investigations on WAAM of aluminium and its alloys. However, not enough research has been done on 5356 aluminium alloy fabricated by the WAAM process. This study focused on investing the effect of process parameters on WAAM fabricated 5356 aluminium alloy. Three process parameters namely, wire feed rate (WF), gas flow rate (GF), and welding speed are considered with three levels (L-1, L-2, & L-3) of values for the fabrication of weld beads. Taguchi method is adapted to reduce the number of trials for selecting the working range of input variables. By using Taguchi L9 orthogonal array, nine trials are identified and nine weld beads are fabricated using GMAW based WAAM process with 5356 aluminium alloy. Macro-level structural characterization has been done for the nine weld bead samples. ANNOVA analysis is used to investigate the effect of input process variables on output response variables. The correlations between the process variables and response variables are developed by using multiple regression method. Based on the results, by adopting grey relational analysis method optimized process parameters are identified. A conformation test is conducted for the optimized process parameters and a thin plate is fabricated with optimized process parameters.

RF MEMS switch is a micromechanical device fabricated using semiconductor technology that has numerous outstanding advantages such as low power consumption, small volume, high integration, and so on. One of the key features to be considered on the design of RF MEMS switches is the isolation of the DC bias and the RF signal being transmitted. It is attempted by the introduction of an insulator layer in between the actuation beam and the signal line. Silicon Nitride (Si3N4) is used as the material for insulation. This study involves the employment of a varying section fixed–fixed beam which helps in reduction of the spring constant as well as the pull-in voltage. An analytical model for the proposed device is developed and analyzed using MEMS design tools which are of industrial standard. The analysis shows that pull-in voltage can be decreased by 18% when compared to its similar counterparts. Additionally, this method gives the designer more opportunity to create switches with improved stiction immunity that require lower pull-in voltage. Therefore, the RF switch structure proposed in this work remains free from dielectric charging. Thus in this new switch, the pull-in voltage is considerably reduced still maintaining RF-DC isolation.

The paper investigates and provides an extensive overview of resistance welding in the aerospace industry for joining composite structures. The use of thermoplastic composites is increasing in the aerospace industry and has become a crucial material. Thermoplastics have many advantages over thermoset composites, the most important being their ability to undergo fusion bonding. Welding of thermoplastic composites provides a very advantageous alternative to mechanical fasteners and adhesive joints. Resistance welding of thermoplastics provides an advantage over other welding methods due to its fast and precise process. The ability to control multiple parameters of the welding process optimises the welding process at a very high level. For example, parameters like welding current, clamping pressure, and time of heat application have huge impacts on the weld. The heating element used for the process can also be modified to get desired results when the welding’s size, shape, and material are changed. For example, resistance welding can be done for various weld geometries like a lap joint, a double lap joint, and a skin or stringer joint, which is important in aircraft structures. Thermosets can also be fusion-bonded with the help of thermoplastic, and two techniques, co-curing and hybrid composites, are studied. To gain a better understanding of the welding process, finite element analysis modelling for numerical analysis and resistance welding method optimization is carried out.Defects in the resistance welding process, like void formation and current leakage, are discussed. Non-uniform heat distribution leads to multiple failures. Overheating and underheating also lead to diminishing weld quality. Heating element failure is also a significant cause of weld failure. For weld strengthening, surface treatments and additives like carbon nanotubes and graphene oxides are used. Further research for detailed analysis in different aspects, like fatigue analysis of the weld joint for critical aircraft structures, is required.

This paper presents the development of a beam-steerable reflectarray designed for IoT applications in the 5 GHz (WiFi) frequency range. The proposed reflectarray incorporates a combination of a Rotman lens and a combline series-fed array as the feed source, resulting in a planar structure capable of beam steering. By exciting the Rotman lens port, the combline array emits a beam in a specific direction. The reflected beam is then efficiently redirected by the reflectarray towards the desired direction, achieving high gain. The reflectarray system, utilizing a Rotman lens-based combline array as the feed source, enables the generation of four switchable beams directed at angles of $$-10^{\circ }$$ , $$-20^{\circ }$$ , $$-28^{\circ }$$ , and $$-45^{\circ }$$ . Prototypes of the reflectarray, Rotman lens, and combline array were fabricated separately using low-cost FR4 substrate with dimensions of $$100 \times 100 \times 1.6$$  mm $$^3$$ , $$120 \times 150 \times 1.6$$  mm $$^3$$ and $$120 \times 150 \times 1.6$$  mm $$^3$$ , respectively. The reflectarray antenna with a planar feed source exhibits a gain of 18 dBi at 5 GHz. The results from both the simulated and measured data show strong agreement, emphasizing the antenna’s cost-effectiveness, ease of fabrication, and simplicity, which make it highly suitable for IoT applications.

The latent heat energy storage using Phase Change Material (PCM) has an enormous appeal due to its profitable points associated with density and thermal characteristics. In this regard, a heat exchanger is modelled and analyzed to visualize the thermal behaviour and melting progression of PCM in a circular-shaped enclosed erect vessel via CFD tool. This work analyzes a multiphase transient study of a U-shaped copper tube placed in a closed cylindrical vessel through which heat transfer fluid flows for transferring heat to the PCM. This work shall be advantageous to the researchers to realize the thermal performance, time of PCM melting etc., to carry out research related to solar heat storage. The present study reports substantial decrease in the time taken to melt all the PCM filled in the container. Almost 32% of time is saved in the process of melting of PCM and thus improving the efficiency of the energy storage system.