Experimental Vibrational Study Research Articles

МЕТОДИКА ОПРЕДЕЛЕНИЯ ХАРАКТЕРИСТИК ВИБРОПРОЧНОСТИ КОНСТРУКЦИИ ПРИ ВЫСОКОСКОРОСТНЫХ ТРЕКОВЫХ ИСПЫТАНИЯХ АВИАЦИОННОЙ ТЕХНИКИ

Achieving the speed limits by ballistic aircraft is a priority, relevant and new technical challenge for the present. Track tests of such products are one of the final stages, confirming their practical performance and efficiency. Testing of products of aviation and rocket technology at the "Rocket Rail Track 3500" FKP "GkNIPAS" named after L.K. Safronov allow to accurately simulate the real conditions in which they are operated. The experimental setup includes a two-rail track, made on a special base, which excludes the unacceptable deflection of the R65 rail, with its fixing every 0.5 m by a special embedment design. The rail track has an acceleration section with an angle of attack of 2º and a length of 2500 m and a deceleration section. The test object is placed on the missile track carriage in such a way as to exclude the impact on it of shock waves reflected from the elements of the carriage and relief. Solid propellant rocket engines are installed on the carriage, which provide the necessary thrust. The sliding bearings of the rocket carriage cover the head of the rails. The thrust of the starting rocket engines provides the necessary acceleration to achieve the maximum values of the required test speed. Track high-speed tests of special equipment objects are accompanied by intense vibration and shock loading of the structure. As the speed of products increases above 600 m/s, as tests have shown, the amplitude of elastic oscillations of the structure can reach the maximum values permissible from the strength conditions. Experimental and theoretical study of vibration and shock effects on the structure of a track carriage with test objects under the conditions of an existing rail track is an urgent task for practice.

Experimental study of vibrations of cross-rod spatial structures

This article explores a technique for studying the dynamic characteristics of cross-rod spatial structures (CRSS) using small-scale models, including the developed nodal connection of spatial frame rods protected by copyright. Using a nodal connection makes it possible to regulate the construction lifting of large-span structures and increases their strength and reliability. The developed nodal connection of the structure can be used for any spatial frames of buildings and structures and is especially effective for the frames erected in areas of high seismicity. Choosing methods for excitation of free and forced vibrations is being investigated, equipment for recording and recording vibrations is selected, and a layout of vibration sensors and sources of excitation of free and forced vibrations is being developed. Natural vertical oscillations of the structure model were caused by removing it from the state of equilibrium by concentrated loads applied in the middle and a quarter of the span with their subsequent removal. The test results and their analysis are analyzed. The experimental models' elements at all loading stages worked in the elastic stage. The tests showed that the structure has sufficient strength, stability, rigidity, and seismic resistance. Based on the results obtained, recommendations were made for their use in calculating and designing CRSS for seismic regions.

A Comparative Experimental Study of Vibration and Acoustic Emission on Fault Diagnosis of Low-Speed Bearing

A Comparative Experimental Study of Vibration and Acoustic Emission on Fault Diagnosis of Low-Speed Bearing

Экспериментальные исследования колебаний трамвая «Витязь-М»

Objective: Based on experimental studies of vibrations of Vityaz-M tram car occurring at speeds of 50 km/h or more on track straight sections with P65 rails on reinforced-concrete sleepers, to evaluate the effect of transversal vibrations on traffic safety and passenger comfort. To show the inconsistency of existing regulatory documentation on the structure and maintenance of tram tracks and tram chassis with the development prospects. Methods: Experimental measurements of vibration accelerations of tram body and tram chassis, having different mileage, when moving along track experimental section. Measurement and analysis of geometric parameters of rail track experimental section and of trams. Results: Measurements of vibration accelerations occurring during tram motion with 20 to 50 km/h speeds were performed as well as geometric parameter analysis for rail track experimental section and rolling stock wheels’ profiles, participated in the tests, was pursued. During the races, vibration accelerations that occur during movement were measured in three directions — longitudinal, transversal and vertical. The appearance of transversal vibrations of tram body affecting passenger discomfort and traffic safety has been confirmed. The root mean-square values of the amplitudes of vibration accelerations towards three directions in acceleration gravity (g) fractions have been obtained in two variants — at trolley motion between joints and at joints. Vibration acceleration frequency analysis has confirmed a sharp increase in the amplitude of transversal vibrations at frequencies in the region of 1–2 Hz at a speed of 50 km/h for a tram with worn wheels. The compliance of rail track experimental section geometry with the accepted standards as well as the compliance of rolling stock wheels dimensions with constructive documentation are noted. Practical significance: The need for further comprehensive study of the interaction of track and rolling stock while high-speed tram introduction with the purpose to improve existing standards on the structure and maintenance of tram tracks and tram chassis.

Experimental and simulation study of ultrasonic elliptical vibration cutting SiCp/Al composites: chip formation and surface integrity study

SiCp/Al composites are considered as a typical difficult-to-machining material due to the presence of reinforcing particles in the matrix. As the aerospace and military industries demand high dimensional accuracy, high efficiency and low damage for SiCp/Al composites, traditional cutting (TC) methods are no longer sufficient. Ultrasonic elliptical vibration cutting (UEVC) is a cutting technique suitable for difficult-to-machining materials. Its intermittent cutting characteristics can reduce the cutting force, and when the tool cuts the workpiece at ultrasonic frequency, similar to a dynamic impact behavior of the tool on the workpiece with ultrasonic frequency, improve the machinability of the material. In this paper, a multiphase based simulation model is developed that integrates the relationship between three phases and the random distribution of particles. The cutting process of SiCp/Al composites under UEVC and TC is simulated and the removal mechanism of SiCp/Al composites under UEVC is analyzed. The effects of dynamic impact on the UEVC of composites were discussed in terms of chip formation, cutting force and surface morphology. Finally, the correctness of the simulation results was verified by the relevant cutting experiments. The results showed that the UEVC produced more continuous serrations, easier fracture of SiC particles and improved machining performance of SiCp/Al composites compared with the TC. The cutting forces were reduced by 26% and 23%, and the surface roughness was reduced by 19% and 28% at two cutting depths of 25 μm and 50 μm, respectively.

Raman scattering investigation of structural phase transition in compressed EuSn2As2

The layered EuSn2As2 crystal has been proved to be an intrinsic magnetic topological insulator with Bi2Te3-type rhombohedral structure at ambient conditions and undergoes a structural phase transition under pressure. Here, we report an experimental lattice vibration study of EuSn2As2 up to 30.5 GPa by in situ Raman scattering measurements. Four Raman-active modes (2A1g + 2Eg) at ambient pressure are observed experimentally and identified by first-principles calculations. Upon compression, the Eg2 and A1g2 modes merge together at 12.45 GPa, meanwhile the frequencies, intensities, and linewidths of all Raman modes show discontinuous changes, exhibiting a structural phase transition. No Raman-active modes are observed above 21.5 GPa, indicating the new high-pressure metallic phase is completely achieved. The evolution of all observed modes under pressure is also discussed with a two-stage reconstruction mechanism proposed recently by ab initio calculations and XRD measurements. These results provide a basic information about the lattice dynamics and expand our understandings on the structural evolution in layered magnetic topological insulators under high pressure.

Muscimol hydration and vibrational spectroscopy – The impact of explicit and implicit water

The presented study focuses on the interaction of the well-known neurotoxin muscimol with water. Two approaches for the water solvent are applied – the explicit and the implicit. The muscimol-water clusters were obtained by the molecular dynamics simulations and the first solvation shell was kept for further studies. Implicit water was mimicked via the polarized continuum model (PCM). All three tautomeric forms of the free muscimol molecule are considered in the calculations. The combined theoretical and experimental vibrational IR and Raman studies determined the stability of the prevailing zwitterion form in water. We proved that water molecules in the first solvation shell are crucial for the correct prediction of structural and spectroscopic parameters of muscimol due to its ability to form strong hydrogen bonds. We believe that our findings will shed some light on the binding preferences of muscimol with the γ-aminobutyric acid (GABA) receptor.

Molecular Structure, Experimental and Theoretical Vibrational Spectroscopy, (HOMO-LUMO, NBO) Investigation, (RDG, AIM) Analysis, (MEP, NLO) Study and Molecular Docking of Ethyl-2-{[4-Ethyl-5-(Quinolin-8-yloxyMethyl)-4H-1,2,4-Triazol-3-yl] Sulfanyl} Acetate

The spectroscopic characterization of the new synthesized heterocyclic aromatic organic compound ethyl −2-{[4-ethyl −5-(quinolin- 8-yloxymethyl) -4H- 1,2,4-triazol −3-yl] sulfanyl} acetate (abbreviated by Q-tsa) was carried out using experimental FTIR, UV–Vis, 1H, and 13C NMR techniques. To support the analytical results, theoretical calculations were performed on Q-tsa using DFT method associated with B3LYP functional with 6-31G(d,p) and 6-311G(d,p) basis sets. Furthermore, the reactivity of the title compound was studied by the investigation of frontier molecular orbitals (FMO) analysis, HOMO-LUMO energies, density of state (DOS), molecular electrostatic potential (MEP), global and local chemical reactivity descriptors. Thermodynamic properties were separately computed and discussed. The attractive, repulsive and van der Waals strong and weak interactions in Q-tsa were performed via RDG analysis followed by the investigation of topological properties via AIM theory. Similarly, the NLO activity of the studied compound was highlighted by computing the first hyperpolarizability in different available solvents. Finally, through molecular docking, the biological activity of Q-tsa was studied and discussed.

Analytical and Experimental Study of Beam Bending Vibration

This study presents free bending vibration analysis of beams of glass epoxy material. The analytical and the modal model (experimental) methods were used to conduct the investigation. The experiment represents basic concepts of the modal model analysis method, which allows us to find the beam's natural frequencies and vibrational mode shapes. The analytical solution was found using Maple and compared to the frequencies obtained experimentally.

Application of modal and harmonic analysis to predict the automotive transmission vibration at an early stage of design

Introduction (problem statement and relevance). The need to increase the operating speeds and input torque of automobile transmissions because of their vibration is becoming a more and more urgent problem.The purpose of the study was to substantiate the applicability of harmonic analysis, which makes it possible to determine the actual values of vibration values during a steady oscillatory process, for the initial assessment of the gearbox vibration activity.Methodology and research methods. The calculation of the gearbox vibration activity was carried out by modal and harmonic analyses, implemented by the finite element method, and followed by the experimental study of gearbox vibration on a test bench.Scientific novelty and results. The presented experimental and calculated results of the research show that the difference between the experimental and calculated values is no more than 4.2%. This proves the possibility of applying modal and harmonic analysis to predict the gearbox vibration state at an early stage of product design at the stand.Practical significance. The given calculation algorithm makes it possible to predict, with a sufficient degree of accuracy, the vibration of the gearbox before the manufacture of a prototype in experimental production.

Experimental and analytical study of ultrasonic elliptical vibration cutting of micro-pyramid reflective mold based on guided wave transmission

Experimental and analytical study of ultrasonic elliptical vibration cutting of micro-pyramid reflective mold based on guided wave transmission

An approximate mathematical model for estimating the influence of vibrations on attached elements of a mobile robot video system

The problem of constructing and applying of mathematical model for assessing the influence of vibrations on the attached elements of the video system of a mobile robot is solved. This robot is considered as a mobile platform for placing of the special equipment for various purposes. The analysis of mathematical models and the results of experimental studies of vibrations of multi-support wheeled machine and its structural elements has been conducted. On the basis of this analysis, the form of a stochastic mathematical model of vibrations of the structure of a mobile robot has been substantiated. The vibration model is specified as a correlation function or spectral density of a random process for various conditions of the robot’s movement. Differential equations of the shaping filter for modeling а random vibration process with given characteristics are presented. Differential equations for the probabilistic moments of the vibration process are presented. Based on the equations for the probabilistic moments and the proposed formula, an assessment of events, which consist in exceeding the vibration amplitude of a given level was carried out. These events are named as outliers of a random process and characterize the range within the basic properties of the equipment installed on the mobile platform are preserved. An analytical study of a mathematical model to determine the intensity of emissions of a random vibration process has been carried out. The probabilistic characteristics of the vibration process and the intensity of emissions are determined. The obtained theoretical results make it possible to assess the performance of the elements of a video system installed on a mobile platform and to formulate the basic requirements for tolerances for their parameters. The results of computer modeling clearly showed the efficiency of the proposed mathematical model for assessing the influence of vibrations.

Experimental study of post-crack vibrations in dynamic fracture

Vibrations induced by crack propagation in a strip of bonded silicon wafers are studied. A new optical setup enables the fast recording of crack-originated acoustic waves, emitted both ahead and behind the crack front, in bonded and separated wafers, respectively. Three types of crack-induced vibrations are identified, corresponding to different excitations and responses of the system: (1) “pneumatic” vibrations involving inertia and gas expansion/compression, (2) standard flexural waves involving inertia and bending rigidity, and (3) post-crack vibrations involving inertia, bending rigidity, and coupling to gas pressure. We show that a standard “beam on elastic foundation” model can explain these latter vibrations that occur along crack edges and is consistent with the observed frequencies.

Experimental and theoretical vibrational study of the fungicide pyraclostrobin

The vibrational study of the pyraclostrobin (methyl N-(2-{[1-(4-chlorophenyl)-1H-pyrazol-3-yl]oxymethyl}phenyl) N-methoxycarbamate) molecule, a synthetic fungicide for agricultural uses, was performed. Pyraclostrobin belongs to the strobilurin family and acts by inhibiting the fungus respiratory chain at the level of Complex III, becoming an excellent agent for preventive, curative and eradicative activities against a wide range of fungal plant pathogens. However, its presence needs to be monitored to avoid the excessive and/or improper use that may compromise human or environmental health. The FTIR and Raman spectra of pyraclostrobin in pure solid state were recorded and compared with those obtained from both the substance in CH2Cl2 solution and in an agricultural commercial product (Comet® BASF). The spectral analysis was complemented with quantum-chemical calculations at the DFT level (B3LYP/6-311G*) for the predictions of the molecular geometry and its vibrational behavior. The high flexibility of the molecule was explored by performing potential energy scans on several dihedral angles and the results suggested that the main conformer of pyraclostrobin is that possessing the ortho-substituted benzene ring in perpendicular orientation regarding the plane that contains the ether group and the pyrazole ring, although the presence of a second preferred conformation in the experimental vibrational spectra was not ruled out. Among the many vibrational bands of pyraclostrobin that were well identified in the spectrum of the composite product for agricultural use, the one located at 936 cm−1 stood out. This signal was assigned to a vibration of the pyrazole ring and promised to be a good candidate as marker of the presence of the fungicide in complex matrixes.

Development and verification of hydroelastic model experiment for the flow-induced vibration analysis of roller compacted concrete dam

To carry out the experimental study of flow-induced vibration for roller compacted concrete dam (RCCD), the improved hydroelastic model experiment (HEME) technology that satisfying both the hydraulic and structural dynamic similarities is presented, and an improved combinatorial method is proposed to effectively and accurately calculate the dynamic characteristics of RCCD model under natural excitation and complex environment. Due to the insufficient study on the simulation technique for the interfaces between adjacent concrete layers in RCCD, the conventional HEME technology which is frequently applied is not applicable to the RCCD dynamic analysis. Therefore, the hydroelastic simulation schemes for cold joints and ordinary interfaces in RCCD are firstly presented based on experimental and theoretical researches and numerical verification. Then, the integral RCCD model is established and its dynamic displacements under flood discharge excitation are tested. Furthermore, the proposed method that combines the advantages of natural excitation technique (NExT), singular entropy (SE) method, and eigensystem realization algorithm with data correlation (ERA/DC) method is applied to calculate the dynamic characteristics of RCCD model. The dynamic characteristics of the RCCD model calculated by the proposed theoretical method are very similar to those of the actual RCCD calculated by numerical simulation, which indicate the effectiveness and accuracy for the improved HEME technology and combinatorial method.

Nitroethane at high density: an experimental and computational vibrational study.

The vibrational spectrum of liquid and solid nitroethane was measured as a function of pressure. Both Raman scattering and absorption IR spectroscopies were applied to samples of nitroethane, statically compressed at ambient temperature to a maximum pressure of 8.0 GPa and 16.9 GPa, respectively. A new amorphous to crystalline transition pressure was found to lie between 1.59-1.63 GPa. Davydov splitting of internal modes into two components suggests two molecules associated with the unit cell, which is consistent with the DFT predictions made in a previous study. For most bands below 1200 cm-1, pressure induced mode progression was consistent with DFT predictions. Conversely, observed mode shifts in the 2950-3100 cm-1 region were generally stiffer than their DFT counterparts. A discontinuity in mode evolution between 3.7-4.3 GPa was observed for a number of modes and shown to coincide with hydrogen bond rearrangement in this pressure region. Preferred orientation and crystallite strain might explain the increased scatter between the various pressure induced mode shift cycles. Time intervals on the order of ∼30 h may be required between spectra, in order to give the crystallites time to equilibrate their strain.

Experimental and Comparative Study of Rotor Vibrations of Permanent Magnet Machines with Two Different Fractional Pole/Slot Combinations

This study deals with the noise, vibration, and harshness (NVH) characteristic analysis of permanent magnet synchronous motors (PMSMs) for electrical machines, such as electrically driven tools that are used in industries. An improved NVH design is needed for application to industrial tools. In general, the electromagnetic NVH characteristics of PMSMs are classified into electromagnetic excitation sources, such as total harmonic distortion of EMF, torque pulsation, magnetic pull force, and unbalanced magnetic force (UMF). This study compares the vibration and noise generated by fractional pole/slot combinations. In PMSMs with fractional pole/slot combinations, UMF is an important NVH source. PMSMs generate UMF because of armature reaction fields based on the pole/slot combinations and harmonics of magnetic flux density. UMF was derived using the finite element method, and the rotor vibration analysis was performed using electromagnetic mechanical coupling analysis. The analysis results and the effect of electromagnetic excitation characteristics on the rotor vibration of the PMSMs were compared and analyzed.

Molecular structure, spectroscopic, quantum chemical, topological, molecular docking and antimicrobial activity of 3-(4-Chlorophenyl)-5-[4-propan-2-yl) phenyl-4, 5-dihydro-1H-pyrazol-1-yl] (pyridin-4-yl) methanone

The conjugated experimental and theoretical vibrational study of 3-(4-Chlorophenyl)-5-[4-propane -2-yl) phenyl-4, 5-dihydro-1H-pyrazole-1-yl] (pyridine -4-yl) methanone (CPPPM) molecule has been extend out and they have been dully compared with standard values in arrangement to exhibit the constancy of the results. Results of DFT analysis move out using B3LYP functional with 6-311++G (d, p) and 6-311G (d, p) basis sets, respectively. The experimental geometrical parameters were compared with theoretical data. The fundamental modes of vibrations were attributing by PED, the computed and experimental values uphold each other. The HOMO-LUMO energy allotment was computed which demonstrate the charge carry over within the molecule. Molecular Electrostatic Potential (MEP) was mapped. The UV-Vis data of the molecule were used to study the visible absorption maxima (λmax) by Time- Dependent DFT. Topological parameters at bond critical points (BCPs) have been evaluated by Quantum theory of atoms in molecules (QTAIM), Electron Localization Function (ELF) and reduced density gradient of the title molecule was investigated by the interaction of molecule . The natural bonds orbital (NBO) analysis was executed to know the transpose of electrons within the molecule and the stability, charge delocalization of the entitle molecule were deliberate. CPPPM has been picking for its antimicrobial activity and found to demonstrate antibacterial and antifungal effects. Docking simulation has been achieved.

THE INFLUENCE OF THE STIFFNESS OF THE ELEMENTS OF RAIL DAMPING ON THE PARAMETERS OF THE MULTI-MASS WAGON–TRACK VIBRATORY SYSTEM

The task of achieving the increase in the weight and velocity of trains being core objective for most railways is inherently associated with solving problems of improving the dynamic qualities of wagons and locomotives during their interaction with the upper structure of the railway track. The strength and stability of rolling stock against derailment in various climatic zones should be ensured together with minimizing operating costs.Analysis of the reliability and performance of the wagon–track system can be conducted based on multivariate dynamic calculations of mathematical models and through experimental studies of dynamic vibrations. Currently, the issues of the influence of changes in the elastic-hysteresis properties of various impact absorber materials under the action of temperature factors on the elements of a multi-mass vibratory system remain insufficiently studied. The purpose of the research described in the article was to analyze the dynamic processes taking place in a multi-mass wagon–track vibratory system under the influence of changes in stiffness and internal friction coefficients of a damping rail component depending on a type of structural material and ambient temperature.The research resulted in elaborating model of multi-mass vibratory wagon–track system. Multivariate model calculations were carried out regarding various stiffness and internal friction parameters of damping elements situated under the rail; the parameters being selected from experimentally constructed dynamic hysteresis. The work presents results of calculations of the reaction forces and deviations in the elements of the vibratory system depending on temperature, type of material, thickness and design of damping elements.

Experimental study of resonance vibrations of the vibratory machine excited by a ball auto-balancer

A prototype of the universal resonance vibratory machine of wide use has been designed. The base of the vibratory machine is a vibratory table. Elastic supports make it possible for the platform of a vibratory machine, which has three degrees of freedom, to execute three main vibrational motions corresponding to three resonant frequencies. The vibration exciter is shaped in the form of a ball auto-balancer. It is assumed that the balls in the auto-balancer would get stuck at the first resonance shaft rotation velocity. The first form of resonance oscillations would be induced in this case.The vibratory table can be used on its own. In addition, the platform can host attachments with sieves for sifting or separating a loose material, a tumbling container, molds for bricks, slabs, etc.The experimental study has established that the proper choice of the number of plates in the supports, the number and mass of the balls could ensure almost matching dynamic characteristics of the vibratory machine in the configurations including a vibratory table and vibratory separator. At the same time, when the shaft rotates at speeds exceeding the first resonance frequency, the platform executes (almost undisturbed) vertical progressive oscillations. As the shaft’s rotation speed increases, the platform’s oscillation amplitude increases while the frequency practically does not change. If the shaft rotation speed exceeds the first resonance frequency by 15–20 %, the accelerations of the platform become sufficient to form a boiling layer at the surface of the platform. As the shaft’s rotation speed increases, the growth of the amplitude of oscillations slows down, which is due to both the sliding of the balls along the track and the non-linearity of the supports at large deformations.The current study has confirmed the efficiency and versatility of the designed vibratory machine, thereby providing the basis for its further improvement