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Analysis of surface roughness and machining performance of AZ91 magnesium alloy cut by WEDM
Full text linkAZ91 magnesium alloys have poor machinability when conventional chip removal processes are used due to their low thermal stability and high susceptibility to softening and oxidation at elevated temperatures, which lead to excessive tool wear, poor surface quality, and deformation-induced machining challenges. This study investigated the impact of wire electrical discharge machining (WEDM) parameters on material removal rate (MRR) and surface roughness (SR) using magnesium. For this purpose, an analysis of variance (ANOVA) and Grey Relational Analysis (GRA) were performed to find the optimal settings. Findings indicate that pulse-on time (Ton) significantly affects both MRR and SR: higher Ton increases MRR but worsens SR, while shorter Ton improves SR but reduces MRR. Pulse-off time (Toff) and wire feed rate (WF) have secondary effects. Longer Toff improves surface quality but slightly reduces MRR, and lower WF improves cutting efficiency and MRR. The optimal settings identified by the Taguchi method were observed to be 123 μs Ton, 55 μs Toff, and 6 mmin−1 WF for high MRR; and 123 μs Ton, 58 μs Toff, and 4 mmin−1 WF for reduced SR. In summary, understanding how WEDM parameters affect MRR and SR allows manufacturers to achieve efficient material removal and desired surface quality
Effects of coupled diffusion and buoyancy forces on three-dimensional MHD convective Williamson-Casson nanofluid flow: a numerical study
Full text linkThe study analyses how thermal diffusion, Dufour effect, thermophoretic forces, Brownian motion, buoyancy-driven convection, and magnetic fields collectively impact microbial behaviour in a convective MHD flow of a Williamson-Casson nanofluid past an exponentially stretched surface. Utilising Boussinesq’s approach, we examine the density fluctuations induced by temperature and concentration variations. Upon implementing convective surface boundary conditions for the sheet, the governing partial differential equations are transformed into ordinary differential equations and then resolved computationally using the MATLAB “bvp4c” method. This procedure is continued until the equations are resolved. The graphical representation illustrates the impact of essential flow parameters on temperature, concentration, main and secondary velocities, and microorganism profiles. To better understand the behaviour of these parameters, numerical calculations of the local Sherwood number, motile density, skin-friction coefficient, and Nusselt number are conducted. Tabular analysis is used to evaluate the impact of various parameters on fluid flow, including skin friction, the Nusselt number, motile density, and the Sherwood number. The data provided herein closely resemble those previously published by other authors. Ultimately, nanofluids have the potential for significant technical applications in the future. This is due to certain physical characteristics examined in this study. These attributes possess the capacity to enhance thermophysical characteristics and heat mass transport
Wave propagation in a pipe conveying two phase flow
Full text linkThe study of wave propagation in pipes conveying a two-phase flow is of significant importance in various engineering applications, including the oil and gas, chemical, and nuclear industries. One of the most significant characteristics of a two-phase flow in pipes is the flow velocity whose estimation is achieved by various means. However, such approaches can be very sensitive to the operational and boundary conditions. Therefore, there is a need to develop a reliable approach based on the local flow dynamics and properties of the pipe. In this work, a wave-based approach for estimating the phase and group velocities was developed. The governing equation of the work was derived based on Hamilton, and the Chisolm correlation model was used for the two-phase flow. The dispersion relation of the governing equation is first derived in terms of the traveling wave feature. Then, the exact expressions of the phase velocity and group velocity for the bending waves are obtained. Furthermore, the free vibration frequency characteristics of the two phases was studied. The results indicate that in a single-phase flow, wave dispersion occurs at a wavenumber of 2.1, whereas in a two-phase flow with a vapour quality of 0.2, dispersion occurs at a higher wavenumber of 5.8, demonstrating that increasing vapour quality delays the onset of dispersion. This work contributes to a better understanding of wave propagation in a two-phase flow
Influence of localised corrosion shape on adhesive damage and a bonded assembly under thermo-mechanical loading
Full text linkThis study explores the damage prediction of repairs on bonded assemblies through a two-part analysis: simulation and experimentation. The effects of corrosion geometry on adhesive and plate damage were evaluated. In the first part, a three-dimensional finite element method (FEM) was used to analyse a cracked and corroded AL 2024 T3 alloy with a V-notch under thermo-mechanical loading. The analysis included calculating the stress intensity factor (SIF) at the crack tip in mode I at thermo-viscoelastic state, assessing the influence of corrosion geometry, determining the damaged area ratio (DR) for various adhesive configurations, optimising the patch shape for repairs, and examining the effects of crack depth on SIF.The second part involved an experimental investigation on the same bonded assembly under identical conditions. The findings reveal that the circular corrosion shape has minimal impact compared to the square shape, while the rectangular composite patch demonstrated superior performance as an optimal repair solution
Persistence of solvability in quantum systems deformed by Dunkl operators
Full text linkWe study persistence of solvability in nonrelativistic quantum systems with positiondependent mass upon introduction of a deformation by Dunkl operators. Conditions are derived for the governing Schrödinger equation of the conventional system to admit the same solutions as in the deformed case, up to a reparametrisation of coupling constants. These conditions require the positiondependent mass or the potential of the system to have a specific form. If this is the case for a particular system, then the Schrödinger equations for its conventional version and for the Dunkl-deformed partner share solutions in the same functional form
Public perception of the Kamenná District
Full text linkThe article describes the emergence of emergency and workers’ colonies in the city of Brno from the beginning of the 20s of the 20th century. It also briefly introduces the Kamenná District and its inhabitans from its inception up to the present. Here, the social transformation of the locality is highlighted, which is proven mainly by research on education and professional representation in the locality. Furthermore, the introduction briefly describes the phenomenon of gentrification and the definition of individual phases by Philip L. Clay. The primary goal of the work was to find out the public’s current opinion on the locality and thereby help to include the phenomenon of gentrification in one of the phases. The opinion of the public was ascertained using quantitative research by means of questionnaires on the Internet and in the field. The results brought the expected conclusions, the public views the Kamenná District positively and notices signs of renovation of buildings and streets, a richer cultural life or a change in the social structure of the quarter. Using the identified characteristics, gentrification was included in the third phase of its course. 
Verification of mechanical properties of forged moulding compound composite for small structural parts of microsatellites
Full text linkThe mechanical properties of a short fibre composite produced using the forged moulding compound technology were tested. Firstly, these properties were estimated using analytical calculations and the Tsai-Pagani equation. Next, technological tests were conducted, based on which testing samples were made for mechanical tests. The results of the mechanical tests were then compared to calculations. Finaly, a microsatellite part was produced using this technology and integrated into the satellite structure
Loss of particle ratio metric for particle image velocimetry accuracy estimation
Full text linkThis paper presents an algorithm for evaluating measurement uncertainty at individual points within the Particle Image Velocimetry (PIV) method. The algorithm presents a novel correlation plane metric known as the Loss of Particle Ratio (LPR). This metric is computed by evaluating the magnitude of two correlation peaks: Mutual Information (MI) and the autocorrelation peak. LPR is defined as the ratio of MI, accounting for the total number of particles contributing to signal peak growth, to the magnitude of the autocorrelation peak, which represents the total number of particles within an interrogation area (IA). The computation of LPR allows both the overall measurement accuracy and the accuracy in each direction to be determined. To improve accuracy, the proposed metric undergoes corrections based on the resultant displacement from the last iteration of the Standard Cross-Correlation (SCC) algorithm and the gradient value within the IA. The process of determining the measurement uncertainty relies on the analysis of synthetic data and the application of two tests – the Uniform Flow Test (UFT) and the Couette Flow Test (CFT). The paper explores the impact of individual corrections on the metric and establishes dependencies between the adjusted metric values and measurement uncertainty. The procedure defines the measurement uncertainty based on synthetic test parameterisation, considering key parameters that influence accuracy, such as the density of particles within the IA, the velocity gradient, the particle diameter, the displacement in the last iteration, and the noise level. The synthetic test parametrisation employs various methods for defining the gradient within the IA. The proposed procedure for determining the measurement uncertainty, utilising the corrected metric Loss of Particle Ratio, is compared with an approach based on synthetic test parameterisation for the Standard Cross-Correlation algorithm. The study contributes insights into the effectiveness of the proposed algorithm in assessing measurement uncertainty, offering a comprehensive comparison with existing methodologies
Analytical and numerical analysis of filament-wound toroidal pressure vessel loaded by internal pressure and temperature field
Full text linkThe presented work deals with the analysis of a toroidal pressure vessel manufactured using filament winding technology. An analytical model based on netting theory was used to determine the pressure vessel meridian curve, winding angle, and thickness change for two ratios of the inner and outer radius of the toroid. The theory of orthotropic continuum was used to determine the stress distribution along the meridian of the torus for loading by internal pressure and temperature field. The stress state was also analysed with the strength criteria for composite materials. The Finite Element Method (FEM) was used for the validation of the analytical model and for the determination of the filling hole effect on the stress state – the violation of membrane stress in its vicinity. The analytical model provides a fast solution, the validity of which was confirmed by FEM, that the temperature (especially after the curing process) has a non-negligible effect on the resulting failure index
Study of correlation between voltage variation and surface temperature during anode mode transitions in a model vacuum switch
Full text linkThe correlation between the voltage course and the anode surface temperature was studied by combined optical and electrical measurements. Performed analysis of the temporal evolution of electrical and optical signals reveals that in the case of constricted anode attachment a clear correlation between electrode surface temperature and arc voltage occurs. The results of the study provide new opportunities for qualification of electrode materials for switching applications