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Establishing the natural frequency of oscillations of a continuous system with a concentrated mass in aviation and manufacturing engineering
Get PDFThe uneven transportation of products in the working bodies (trays) of one-mass vibrating conveyors with inertial exciters prompted the conduct of a study aimed at establishing the natural frequency of oscillations of a continuous system, namely, a long-dimensional body with distributed parameters in the form of a beam with a rigidly fixed concentrated mass. Using the Krylov-Duncan functions, the differential equation of movement of the beam was solved, taking into account the concentrated mass and the boundary conditions at its ends. The system of equations made it possible to analytically establish the natural frequency of such a continuous system. This approach was tested to establish the natural oscillation frequency of a glider, demonstrating its versatility for use in various industries. An analysis of the obtained results was carried out, and conclusions were drawn
Design and verification of a new type of hydraulic vibration isolator for high-speed train floors
Get PDFWith the development of high-speed trains, the requirements for noise, vibration, and comfort are becoming increasingly stringent. The train body floor, as one of the main pathways for vibration transmission, is crucial to be treated for vibration reduction and noise attenuation. This paper, in response to this demand, has developed a new type of floor vibration isolator specifically for high-speed trains. Through finite element simulation analysis and experimental verification, it has been proven that this vibration isolator can effectively reduce the vibration of the train body floor and significantly enhance the NVH (Noise, Vibration, and Harshness) performance of the train
Analysis of the natural characteristics of fiber-reinforced cantilever beams using 8-node solid elements
Get PDFA combined theoretical and experimental approach is employed to investigate the dynamic characteristics of fiber-reinforced cantilever beams. An 8-node element method establishes the theoretical model of the cantilever beam, allowing for the determination of its dynamic properties. A relevant experimental platform is constructed to test the fiber-reinforced cantilever beams, thereby validating the accuracy of the theoretical model. The results indicate that the theoretical model accurately predicts the dynamic characteristics of fiber-reinforced cantilever beams. Finally, based on the established theoretical model, the effects of cantilever beam length, width, and elastic modulus on the dynamic characteristics of the cantilever beam are discussed
Signal Sampling criteria and application of structural monitoring based on amplitude analysis
Get PDFThe research explores the influence of sampling frequency on the amplitude analysis error for signals with diverse functional forms, and delineates the approach for ascertaining the optimal sampling frequency for amplitude analysis of signals under dynamic monitoring. A method for determining the sampling frequency of amplitude analysis based on the maximum error criterion is proposed through theoretical derivation of sine function and its composite forms. The correctness of the proposed method is further verified through numerical simulation analysis using MATLAB software. The results indicate that the Nyquist sampling criterion does not meet the precision requirements for amplitude analysis; the impact of odd multiples and even multiples `sampling frequencies on the accuracy of signal amplitude analysis is different; the maximum amplitude error is closely related to the order of the signal; and the even multiples sampling frequency is more reasonable for amplitude analysis. The proposed sampling frequency determination method was applied to the construction of dust removal impact testing system and the fatigue damage analysis of a four-section boom pump truck structure, demonstrating the feasibility of this method in engineering applications. The research in this paper provides theoretical and methodological support for the economic collection and efficient processing of massive condition monitoring signals in engineering practice
Parametric study of the noise of a propeller-driven fixed-wing unmanned aerial vehicle with a piston engine
Get PDFThe results of full-scale acoustic tests of a Ptero-G0 unmanned aerial vehicle (UAV) in an anechoic chamber are presented. The aim of the work is to determine the acoustic characteristics of a Ptero-G0 UAV and to assess the influence of various parameters on the noise level of the device. A unique aspect of the experiment is that a full-scale apparatus with a power plant including a single-cylinder 4-stroke piston engine and 2-bladed fixed-pitch propeller, was studied. Data on the spectral, energy and directivity characteristics of the UAV and its power plant were obtained. The tests assessed the effects of incoming flow velocity, power condition of the power plant, pitch angle of the UAV, propeller diameter, and vibrations of the bonnet on the UAV noise. In particular, increase in the power condition (engine speed) and incoming flow velocity led to an increase in spectral noise levels in the 1/3-octave frequencies bands ranging from 40 to 10,000 Hz. At the same time, background levels up to 40 Hz were determined by background noise. The influence of engine speed and incoming flow velocity on the directivity pattern has not been established. An increase in propeller diameter at a constant speed resulted in higher circumferential speed of the propeller and thrust, as well as increased load on the engine. As a result, intensity of the tonal components of propeller and engine noise increases. A slight decrease in diameter (by 6 %) led to a decrease in the overall noise level by 1.3 dB. Placing the engine in the bonnet without a vibration insulation system led to an increase in the overall sound pressure levels by up to 2.5 dB
Experimental studies of dynamic properties of soils of railroad embankments
Get PDFThe safety and stability of train traffic directly depend on the reliable operation of railroads and the condition of the subgrade. The main purpose of the research was to study the influence of vibration effects on the deformation characteristics of cohesive soils used in the subgrade of railroad embankments. The paper presents the results of compression tests, as well as deformability parameters of the studied soils under static and vibrodynamic loads. The values of deformation modulus (E) for soils of natural origin and with disturbed structure are discussed. It is confirmed that the change in the modulus of deformation of non-water saturated cohesive soils under the influence of vibration depends on changes in the stress state. The modulus of deformation of non-water-saturated clayey soils under static and vibrodynamic loads is determined by the type and nature of interactions between soil particles, as well as possible changes in the process of testing. Soil humidity is one of the key factors influencing the nature of water-colloidal bonds and deformation properties of the soil sample under both static and vibrodynamic loading conditions
Optimization of the dynamic stiffness of the body attachment points for a certain vehicle model
Get PDFTo solve the issue of abnormal vibration while accelerating during the development of a certain vehicle model, this paper utilizes the transfer path analysis (TPA) method to identify the key factors contributing to abnormal noise and vibrations within the vehicle. Through a combination of theoretical derivation and simulation analysis, the study examines the dynamic characteristics of the vehicleβs attachment points, particularly focusing on the shock absorber mounting locations. Based on the findings, a specific method for optimizing the dynamic stiffness of these attachment points is proposed. This optimization significantly improves the vehicleβs NVH (Noise, Vibration, and Harshness) performance, thereby reducing unwanted noise and enhancing the overall comfort and driving experience. The paper offers valuable insights and practical solutions to improve vehicle development processes and ensure superior NVH outcomes
Mechanical response characteristics of railway tunnels under train loading
Get PDFThis study focuses on the mechanical response characteristics of railway tunnels under train loading, which is investigated in depth through model tests. The design of the test covers the similarity ratio, model box, structural model, transducer and loading condition, etc. The model test process includes shaker fixing and model box filling. The test results show that: (1) under different loading frequencies, the acceleration at each measurement point of the tunnel lining cross-section is sinusoidal, which is positively correlated with the frequency, and there is a good third-order polynomial fitting relationship between the loading frequency and the peak acceleration. (2) The peak acceleration of the vault and the left arch foot varies significantly under specific frequency conditions, and the peak acceleration of the superelevation arch grows rapidly; (3) The pattern of change of peak acceleration in the time domain analysis is highly consistent with the pattern of change of amplitude in the corresponding frequency domain analysis. This study provides important data support and theoretical basis for the design, construction and maintenance of railway tunnels, which helps to ensure the safe operation of railway tunnels, and at the same time provides a reference for further in-depth research on the evolution of the performance of the tunnel structure under the action of complex train loads
Finite element analysis of vibration transmission in building-integrated metro systems
Get PDFThis study develops a comprehensive model that integrates the vibration source, building structure, and surrounding soil layers. The methodology involves a vertical vehicle-track coupling dynamic model and a multi-scale coupled finite element model encompassing moving loads, track structure, building body, and surrounding strata. The results show that vibrations induced by trains operating on the first level remain within acceptable limits. However, when trains operate simultaneously on both the first and second levels, vibration levels in the overlying structure exceed specified standards. Further targeted design optimizations are recommended
Scientific and practical substantiation of transient processes in asynchronous electric motors of mainline electric locomotives
Get PDFThe research work focuses on scientifically substantiating the operating conditions of small and medium-power auxiliary asynchronous electric motors used in mainline electric locomotives under JSC βUzbekistan Railwaysβ. The aim is to provide a scientific basis for the operational efficiency of auxiliary asynchronous electric motors and, based on the research findings, to conduct a practical investigation of their service life. This, in turn, will enable timely maintenance of auxiliary asynchronous electric motors in locomotives. Additionally, it will contribute to improving the performance indicators of auxiliary asynchronous electric motors