Volume 21 (2021): Issue 1 (March 2021)

Thermal buckling study on the symmetric laminated composite trapezoidal plate with a circular cutout subjected to a uniform increase in temperature for various boundary conditions is explored in this paper. In a mathematical model, the first-order shear deformation principle is employed in accordance with the variational energy system. For acquiring the thermal buckling temperature, a nine-node heterosis plate relation has been used in the finite element formulation. By correlating the present findings with accessible literature, the effectiveness of the present formulation is verified. The impact of different parameters, such as trapezoidal shape, cutout size, ply-orientation, plate edge conditions and plate width to thickness ratio have been considered to study the effect of each parameters on the buckling characteristics of plate under various temperatures. It is observed from the study that each parametric investigation significantly affect the thermal buckling behaviour of trapezoidal plates.

A variety of tool shoulder designs comprising three families i.e. blade, spiral and circular shaped scrolls, were produced to improve the material flow and restrictions to avoid the tunnel void. The bobbin tools were manufactured by 3D printing additive manufacturing technology using solid filament. The butt weld joint was produced by each tool using plasticine as the workpiece material. The apparent surface features and bi-colour cross-sections provided a physical flow comparison among the shoulder designs. For the bobbin friction stir welding (BFSW), the tool shoulder with a three-spiral design produced the most stability with the best combination of the flow patterns on surface and cross-sections. The circular family tools showed a suitable intermixing on the surface pattern, while the blade scrolls showed better flow features within the cross-sections. The flow-driven effect of the shoulder features of the bobbin-tool design (inscribed grooves) was replicated by the 3D-printed tools and the analogue modelling of the weld samples. Similar flow patterns were achieved by dissimilar aluminium-copper weld, validating the accuracy of the analogue plasticine for the flow visualization of the bobbin friction stir welding.

Wastewaters from dairy processing factories contaminated with α-oxypropionic acid were monitored. Theoretical analysis of industrial wastewater treatment methods on zeolites of Sokyrnytsia deposit was carried out. The process of sorption of α-oxypropionic (α-oxypropionic) acid by natural zeolite of Sokyrnytsia deposit was considered. It was established that the most economically advantageous and safe is the method of adsorption using a natural sorbent - zeolite, which provides the lowest concentration of contaminants in treated wastewaters from dairies. An assessment of their number, localization features and measures of toxicological impact on the environment was done. The existing theoretical apparatus of description of adsorption processes was analyzed. The sorption properties of natural zeolite (clinoptilolite of Sokyrnytsia deposit) and activated carbon to α-oxypropionic acid were tested. Equilibrium values of adsorption capacity were calculated and corresponding isotherms at a temperature of 20 ° С were constructed. The porosity of the sorbent and its influence on the sorption properties were studied by the methods of physicochemical analysis. Infrared spectroscopic and electron microscopic studies confirmed the presence of the process of sorption by the surface of the internal pores of the zeolite of α-oxypropionic acid molecules. Experimental studies have confirmed the possibility of using natural zeolite for wastewater treatment of dairy factories. It was experimentally confirmed by physicochemical methods of analysis (electron microscopy, IR spectroscopy, microprobe analysis, mercury porometry) and was established that the process takes place both by the mechanism of ion exchange and physical adsorption. The content of carbon radicals in the zeolite matrix after the sorption process was confirmed by X-ray spectral microanalysis. The ability of zeolite to adsorb organic carboxylic acid radicals was confirmed by the results of IR spectroscopic studies. On the IR spectra there are strips of deformation and valence oscillations of the groups of the crystal lattice of the zeolite Si-O, Si-O-SiOH: 452, 990–1210, 1638, 3368 cm⁻¹. The oscillation spectra of free OH groups in the region of 2600 cm⁻¹ were revealed.

The article presents the results of the preliminary research of tribological properties of flame sprayed nickel and aluminum coatings reinforced with carbon nanotubes made on the structural steel S235J0 substrate. The carbon material – carbon nanotubes Nanocyl NC 7000 (0.5 wt.% and 1 wt.%) was used for structural reinforcement. The properties evaluation was made by the use of optical microscopy, scanning electron microscopy, Raman spectroscopy, microhardness measurements, and by means of abrasion and erosion resistance laboratory tests. The obtained results were compared with pure nickel powder coatings 2N5 (Ni 99.5%) and with pure aluminum powder coatings (EN AW 1000 series). It was proved that the flame spraying of nickel and aluminum coatings reinforced with particles carbonaceous material can be an effective alternative for other more advanced surfacing technology. The preliminary test results will be successively extended by further experiments to contribute in the near future to develop innovative technologies, that can be implemented in the aviation industry and the automotive. The presented research is a continuation of the work previously published.

The paper presents research in the field of underwater wet cutting with the use of flux-cored wires in order to improve the quality and performance. The research has resulted into the development of gas and slag systems for flux-cored wires and determination of, optimal parameters for cutting stability and quality. The underwater wet cutting mechanism is a cyclical process with the formation of periodic keyholes in metal, and it consists of operating and idle cycles. Efficiency of the cutting process can be determined by analyzing cycle times, welding current, voltage, power and a number of short circuits. To assess the stability and efficiency of the underwater wet cutting process, the authors have developed the method for analyzing oscillograms to calculate the probability density of current, voltage and power. To determine the quality of cutting, the authors have provided a criterion based on the ratio of the voltage probability density in the idle and operating cycles.