Advances in Science and Technology Vol. 181

Abstract: This paper studies how a magnetic field affects the stability domain of a high aspect-ratio plate subjected simultaneously to supersonic gas flow and a temperature gradient across its thickness. Formulating the problem mathematically leads to a boundary value problem describing the plate’s stable configuration. The model is built on the fundamental assumptions of magneto-thermo-elastic plate theory and piston theory. It also employs an extended formula of piston theory, previously derived and explained in detail in [1,2]. Using the Routh–Hurwitz criterion, the study determines the stability regions of the plate under the combined effects of the temperature field and the external flow, and analyzes how the magnetic field modifies these regions. Additionally, based on an obtained formula for the critical flow velocity, the paper computes the corresponding critical velocities for various temperature distributions and explores the impact of the magnetic field on these values.

Abstract: This paper briefly summarises the structure of hierarchical shell finite elements and presents computational results for rotationally symmetric shell structures.

Abstract: The concept of fractional derivative as a mathematical operation was first proposed by Leibniz.In recent years, it has appeared increasingly in constitutive equations that describe the behavior ofvarious materials. This naturally raises the question of whether fractional differentiation could haveimplications for the fundamental structure of Newtonian mechanics. In this study, this possibility isinvestigated in the context of the mechanics of a system of material points. The analysis is grounded inthe principle of stationary action, which, following the seminal works of Noether, serves as a unifyingfoundation across the various branches of physics. This principle provides a coherent framework thatencompasses the established variables and theorems, enabling the derivation of general conclusions.Accordingly, it offers a suitable theoretical basis for examining the role of fractional derivatives withinmechanical systems.

Abstract: In this paper, starting from the introduction of the inerter, which completes electrical - mechanicalsystem analogy, and the introduction of pseudoinverse form of the analytical mechanic (Udwadia -Kalaba formalism ), which allows a handling of the anholonomic constraints without the introductionof the pseudo velocities. The paper investigates the effect of the inerter in a linear vehicle dynamicmodel and gives a procedure for deriving the equations of motion for a nonholonomic mechanicalsystems. Mechanical systems related to articulated vehicle models.

Abstract: The accurate characterization of non-Newtonian fluid pipe flow is essential for engineering applications, such as vibration dampers, and fluid-processing industrial applications. Since traditional measurement setups require circulating significant fluid volumes, this study introduces a novel, compact measurement device developed to determine flow coefficients for a pipe flow using minimal volume of media. This research investigates the pipe flow of shear thickening fluid samples synthesized from PEG200 and fumed silica at 18 wt.% and 24 wt.% concentrations. The experimental results confirmed that increasing the solid volume fraction intensifies the shear thickening characteristics, which causes a sudden increase in pressure loss. The measured values were compared with analytical predictions, and the close agreement between them validates the reliability of this novel measurement technique for characterizing these complex fluids.

Abstract: This study examines the influence of surface finish and geometric parameters on the performance of spur gears used in robotic transmissions. It investigates gear manufacturing errors and their impact on performance, durability, and quality, aiming to optimize gear design parameters for high precision, durability, and load-carrying capabilities. Experimental studies were conducted, revealing that smoother surfaces lead to lower friction and wear. Geometric parameters play a crucial role in optimizing gear meshing and alignment, directly affecting torque transmission and noise levels. The study emphasizes the importance of analyzing these factors for improving the efficiency, precision, and lifespan of robotic applications.

Abstract: This paper highlights the actual influence of gear ratio size on the service life of rolling bearings within the universal helical gear reducers with external gearing. The service life of a reducer primarily depends on the lifespan of its bearings, and further it depends on the gears, keys, shafts, and other components. However, the overall life time of the reducer depends on the intensity of use, working conditions, and maintenance quality. By analyzing the influence of the gear ratio size on the service life of the reducer, it can be concluded that this factor has a remarkably strong impact - not only in single-, double-, and triple-stage reducers, but also in reducers built within a universal housing designed for double-and triple-stage configurations. This influence is somewhat bigger in triple-stage reducers than in double-stage reducers due to the lower rotational speed of the output shaft. Therefore, by properly selecting the bearings and defining the corresponding load of the reducer for specific gear ratios, efforts are made to minimize the influence of the gear ratio as much as possible.

Abstract: Hedge cutters are electric power tools used to trim vegetation in domestic and professional environments. The cutting performance, along with vibration patterns and mechanical stress on the blades, depends heavily on the eccentric mechanism, which converts rotary motor motion into back-and-forth blade motion. The research investigates AC-powered hedge cutters by studying three commercial devices that maintain constant speed through their different eccentric-disk designs. The research investigates how eccentricity affects blade movement, speed, acceleration, and jerk through both mathematical kinematic modeling and computer-based simulation. The results demonstrate that higher eccentricity values produce greater peak velocities and accelerations, which could improve cutting performance but would also increase dynamic forces and vibration. The comparison provides numerical data that helps understand how eccentric design elements affect the system, enabling better mechanical design and optimization of the hedge-trimmer mechanism.

Abstract: The focus of this research is on the geometric design and finite element method (FEM) analysis of a connecting spur gear pair as a part of a mechanical wire bending machine. This goal of this study is to improve the performance of the machine and durability, this will be achieved by optimizing the gear geometry and analyzing stress distribution (Static stress study). Previously, the gear pair was first designed using CATIA and Fusion 360, following standard design parameters like module, center distance and pressure angle. The designed model was analyzed using FEM instruments to model deformation, static stress and contact behavior between teeth. The simulation results were compared with theoretical calculations to validate design accuracy and identify major stress regions. This study provides important insights into enhancing load transmission efficiency, extending gear life and minimizing wear in bending machinery applications.