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Determination of optimal drive parameters for high-speed linear systems
Get PDFThe problem of optimizing the drive design parameters for a high-speed linear system is solved based on minimizing the inertial torque. New analytical expressions are obtained for determining the optimal gear ratio of the intermediate transmission, taking into account the moments of inertia of rotating masses, the carriage mass, and the screw pitch. An optimization problem is proposed to determine the number of gear teeth and the screw pitch by minimizing a function that includes the relative error between the actual and calculated gear ratio, as well as the total number of teeth required to ensure the specified travel speed of a carriage. At the next calculation stage, the number of gear teeth is refined based on the nearest standard screw pitch values. The resulting parameters are evaluated using a transient dynamic analysis according to key kinematic and energy characteristics
Experimental study of the effect of the cell size honeycomb core on the impedance of single-layer SAS
Get PDFThe study of the acoustic characteristics of sound-absorbing structures (SAS) seems to be an urgent task aimed at solving the problem of noise both in the cabin of aircraft and aircraft engine noise. Results of experimental study of the effect of the size of the cell edges of a fiberglass honeycomb core and the degree of perforation on the acoustic characteristics of single-layer sound-absorbing structures are presented. Tests of samples of sound-absorbing structures were performed on an interferometer type installation with a normal incidence of sound waves. The dependence of the acoustic characteristics of SAS on the size of the edge of the honeycomb filler is shown, in connection with the overlap of the holes of the perforated sheet of SAS with the edges of the honeycomb block. The dependence of the resonant frequency and the efficiency of the structure on the diameter of the holes of the perforated sheet are shown
Influence of dynamic behavior of excavator steel structure on correction of human vibrations: operator cabin case study
Get PDFIn this paper, the investigation and the influence of the dynamic behavior of the structure of the structural part on the correction of human vibrations of the cabin of the unloading boom of a bucket wheel excavator are performed. Diagnostic analysis using the finite element method influenced the reconstruction of the local part of the structure to increase the first natural frequency of the given structure, i.e. to reduce the human vibrations of the unloading boom booth. This way, the lifespan of structural parts is extended, but also the health of the operator and better working conditions are affected. By monitoring the state of human vibrations in a certain time interval, before and after the reconstruction, this correct approach was prove
Dynamics and stability analysis of a single-mass oscillatory system with a slider-crank vibration exciter
Get PDFTraditional slider-crank mechanisms transmit high loads through the mechanical structure, hindering the design of compact machines. The paper considers the dynamic behavior of a single-mass oscillatory system actuated by a slider-crank excitation mechanism. The research methodology involves mathematical modeling and computer simulation to analyze the trajectory and kinematic characteristics of the considered oscillatory system. The dynamic diagram of the single-mass vibratory system is considered, and the mathematical model describing its motion is derived using Euler-Lagrange equations. The obtained results show the time response curves of the oscillating mass plane-parallel motion under different excitation conditions, as well as the amplitude and phase responses as functions of frequency. The primary scientific novelty of this research is determining the influence of specific design parameters of the vibration exciter on the trajectory of the working member motion, as well as defining the stability of the response at different frequencies. The research highlights the possibility of generating circular, elliptical, and rectilinear vibrations of the working member depending on the specific operation, such as conveying, screening, sieving, or compacting. This adaptability is crucial for tailoring the system to different industrial applications and optimizing its performance for specific tasks
Vibrodiagnostics and dynamic operation of reinforced concrete sleepers under the influence of moving load
Get PDFVidrodiagnostics is one of the methods of monitoring and diagnosing the railroad track for defects and damages. Determination of vibration (dynamic) impact on the track from the rolling stock load is possible with the help of vibration sensors - velocimeters and accelerometers. The article presents the results of full-scale (operational) tests of reinforced concrete sleepers with different types of bonding on three sections of the railroad mainline. The dependences between the maximum amplitudes of vibration displacement, vibration velocity are determined. The purpose of this study was to identify the main causes of defects in reinforced concrete sleepers by vibrodiagostic method, to identify the greatest attenuation of vibrations of the track structure, damping of vibration from passing rolling stock and determination of the best dynamic operation of the track. This research will help further technological and economic development of railroads, as well as maintain safe operation of the main network of the Republic of Kazakhstan
The effect of the quantity and length of fibers on the mechanical properties of fiber-reinforced concrete based on polypropylene fibers
Get PDFIn these studies, the effect of polypropylene fibers on the mechanical properties of concrete was studied, and special attention was paid to determining their optimal amount and acceptable length. The fibers were added to the concrete composition in amounts of 0.1-0.5 % and lengths of 10, 20, 30, 40, 50 mm and tested. According to the results of the study, the highest results were recorded at a fiber content of 0.2-0.3 % and lengths of 20-30 mm, and the compressive strength of concrete increased by up to 15.9 % compared to ordinary concrete. When adding fibers in excess (≥ 0.4 %) or with a length of 50 mm, a decrease in strength was observed. The results obtained showed that it is possible to increase the quality and improve the strength of concrete by selecting the optimal parameters of polypropylene fibers
Torsional dynamics and parametric instability in integrated electric drive systems with PMSM and gear train
Get PDFThis study investigates the vibrational stability and torsional vibration characteristics of an integrated electric drive system composed of a permanent magnet synchronous motor (PMSM) and a two-stage gear pair under parametric excitation. An electromechanically coupled nonlinear torsional dynamic model is established, incorporating electromagnetic effects and time-varying mesh stiffness. The method of multiple scales is employed to analyze the parametric excitation-induced vibrational stability of the system, and the Runge-Kutta method is used to solve the vibrational differential equations and examine the dynamic response characteristics. The results indicate that the system exhibits significant coupled vibrational behavior: the spectrum of the dynamic meshing force contains not only the meshing frequency of the current gear pair but also the system’s natural frequencies and meshing frequency components from other gear stages. Under conditions without external excitation, the system is found to exhibit not only primary resonance responses due to time-varying mesh stiffness excitation but also various nonlinear vibrational phenomena such as subharmonic resonance, superharmonic resonance, and combination resonance. The response is particularly pronounced near twice the first-order natural frequency
LSGAN-Transformer life prediction method for rolling bearings under few samples
Get PDFAiming at the problem that it is difficult to obtain a large amount of data for bearings with complex working conditions, which leads to the inability to accurately predict their life, a rolling bearing life prediction method based on few samples, LSGAN-Transformer, is proposed. A dropout layer is added to the LSGAN generator to avoid the overfitting phenomenon that often occurs during few-sample training. The normalization of each layer in the traditional Transformer model is moved forward to the input of the decoder and encoder submodules before the residual network, forming a direct gradient path from input to output, avoiding the problem of excessive expected gradient near the output layer that often occurs in the traditional Transformer network. Verification on the PHM2012 dataset and the XJTY-SY dataset shows that the MAE and RMSE of the proposed method are greatly improved; compared with other common prediction models, the MAE and RMSE of the proposed method are improved by 30.61 % and 35.93 % respectively
Stodola-Vianello iteration method for the free flexural vibration frequencies of Shimpi’s single variable shear deformable beams
Get PDFThe natural vibration frequency analysis of beams is vital for their design against resonance failures because such failures occur when the excitation load frequencies of vibration coincide with such natural frequencies. This work presents a single variable shear deformable beam equation formulated using Shimpi’s displacement field assumptions. This results in a quadratic shear stress profile over the depth and a satisfaction of the transverse shear stress-free boundary conditions. The governing equation is obtained using a first principles consideration and equilibrium method as a partial differential equation (PDE) which is non-homogenous for forced vibrations and homogeneous for free vibrations. The study then used the Stodola-Vianello iteration method to solve the resulting homogeneous PDE for simply supported boundary conditions and harmonic response. The problem reduced to an iterative problem of algebra involving the computation of an (n+1)th vibratory modal shape function from an nth shape function that satisfies the boundary conditions. This work used a sinusoidal shape function which is exact for the simply supported boundary condition investigated. The use of boundary conditions solved the integration constants involved. Application of the convergence rule led to the eigenequation from which the eigenvalues were found. The eigenvalues were presented for the first four modes of vibration and for a rectangular beam. It was found that for l/h varying from 5 to 100, the natural vibration frequencies were identical with the ωn values obtained using Navier method for other thick beam vibration problems. It was also found that ωnwas close to the exact values for all vibration modes and for all values of l/h between 5 and 100. For all vibration modes and all considered l/h values negligible differences, were observed between the ωn obtained using SVIM and the exact values obtained by previous researchers
Modern strengthening techniques for enhancing the load-carrying capacity of in-service road bridges in Uzbekistan
Get PDFThe sustained growth of traffic intensity and axle loads in Uzbekistan has accelerated the deterioration of in-service road bridges, making cost-effective strengthening a national priority. This paper presents a structured review and comparative assessment of strengthening approaches grouped into: (i) traditional cross-section enlargement and substructure rehabilitation, (ii) structural scheme optimization and dead-load reduction (including external prestressing and span continuity), and (iii) advanced solutions based on carbon-fiber-reinforced polymers (CFRP). A worked example for a typical reinforced-concrete girder span demonstrates the compensation of a deficient bending moment of ΔM= 70 kN·m and indicates an ~18-25 % increase in load-carrying capacity after strengthening. The paper further synthesizes implementation considerations for arid-continental climates, including surface preparation, adhesion control, protective coatings, and staged load testing. Drawing on regional practice, CFRP systems are highlighted as offering high strength-to-weight benefits, installation speed, and minimal traffic disruption; reported gains for flexural elements typically range from 25 % to 45 %, subject to detailing and quality assurance. The results support integrating CFRP-based measures and complementary dead-load optimization into bridge rehabilitation programs in Uzbekistan, with recommendations for monitoring intervals (6-12 months) and future durability studies on adhesives and UV/moisture protection. Overall, the study consolidates methods and provides quantitatively grounded guidance for extending service life under contemporary traffic demands