Experimental Vibrational Study Research Articles

Experimental Vibration Studies of Deep Groove Ball Bearings Having Damaged Surfaces

Bearing plays vital role in dynamic characteristic of any rotating machine. Vibration study of rolling element bearings in the presence of either local defect or distributed defect have been carried out by many researchers. In the present study experimental vibration studies of bearing in the presence of local defect on one of the bearing race and waviness on another race have been carried out. Moreover, the effects of local defect width, waviness order, radial load, rotational speed, presence of lubricant on vibration amplitude in the presence of local defect and race waviness have also been analyzed. Frequency peaks at both characteristic defect frequencies, based on location and type of defect have been observed in the presence of combined defects. The local defect frequency amplitude of inner race/outer race is affected by presence of distributed defect on outer race/inner race and vice versa. However, the waviness frequency amplitude found dominant as compared to local defect frequency amplitude. This study will be helpful to practicing engineers in analyzing the complex vibrations generated by defective rolling elements bearings.

Theoretical and experimental vibration studies of lubricated deep groove ball bearings having surface waviness on its races

A dynamic model has been presented to study vibrations of deep groove ball bearings having waviness on surface of bearing races. Masses of shaft, races, balls and housing have been considered in modelling. Stiffness and damping due to non-linear Hertzian contact and lubricant film have been incorporated in dynamic model. The coupled solution of governing equations of motions is obtained using Runge Kutta method. The vibrations velocity spectra of bearing housing computed through dynamic model have been validated with experimental results, which were generated using healthy and defective deep groove ball bearings. The effect of governing parameters like radial load, shaft rotational speed, waviness order, waviness amplitude on amplitude of waviness defect frequency have been investigated broadly using both theoretical and experimental results. Severe vibration amplitudes have been observed in presence of waviness order equal to number of balls. Good correlations between theoretical and experimental results have been observed. The present study would give researchers new insights into dynamic behaviour of shaft bearing system.

Determining the Quality of Electric Motors by Vibro-Diagnostic Characteristics

Experimental studies of vibrations of asynchronous electric motors (EMs) of the electric bus traction electric drive are carried out in the paper. The presented studies are based on generalization of the diagnostic features of vibration characteristics and statistics concerning the limiting values of vibration parameters of EMs and their dependence on the technical condition. The analysis of the obtained results allowed us to determine the permissible vibration levels of EMs in the frequency range from 5 Hz to 10 kHz. The method of diagnosing EMs traction electric drive according to the indicators of vibration levels is developed, which allows to evaluate their technical condition. The values of the permissible vibrational accelerations of the electric bus EMs are determined, which enable to estimate their technical level. This method allowed to develop classes of evaluation of the EMs technical condition by the level of their vibration, which makes possible to predict their resource.

The theoretical and experimental vibrational studies of thiourea and silver nitrate (2:1) complex

The theoretical and experimental vibrational studies for poly thiourea silver nitrate (2:1) complex using DFT method are performed on the basis of experimental data. During the geometry optimization process one equilibrium structure was found. The Mulliken charges, harmonic vibrational frequencies, Infrared and Raman intensities were calculated on the basis of quantum chemical density functional calculations using firefly (PC GAMESS) Version 7.1G. The clear – cut assignments of observed bands are performed on the basis of potential energy distribution (PED) analysis. Highest Occupied Molecular Orbital (HOMO) and the Lowest Occupied Molecular Orbital (LUMO) are obtained and graphically illustrated with minimum energy. The energy difference between HOMO and LUMO is analyzed. The other molecular properties like molecular electrostatic potential, Mulliken charges and thermodynamic properties of the title compound have also been calculated.

Experimental and analytical study of ultrasonic elliptical vibration cutting on AISI 1045 for sustainable machining of round-shaped microgroove pattern

This research report deals with an experimental and analytical study of the ultrasonic elliptical vibration cutting (UEVC) process on medium steel alloy (AISI 1045) for sustainable machining of round-shaped (R-shaped) microgrooves via relatively low-speed machining (0.5–2.5 m/min). The need for microgroove patterns on planar surfaces in the tribology field has increased significantly owing to superior lubrication performance in decreasing the coefficient of friction. Analyzing the surface roughness, microgroove morphology, cutting force, and chip formation during microgrooving are the main objectives of this experimental study. The experimental results showed that the UEVC process evidently produces lower surface roughness, lower cutting forces, better groove shape morphology, thinner chip thickness, and higher flow shear angle when compared to the conventional cutting process. A new approach in methods to analyze surface roughness and cutting force in UEVC microgrooving has also been developed and validated with the experimental results. Finally, these experimental studies indicate the achievement of sustainable machining of the R-shaped microgroove pattern using the UEVC process.

Experimental study of vibration of metallic and composite plates inside channel driven cavity flow

An experimental study was conducted for the fluid–structure interaction (FSI) of the vibration of a flexible structure inside the channel driven cavity flow (CDCF). The structure was a thin flat plate whose one edge was clamped at the bottom of the three-dimensional CDCF system. Both aluminum and composite plates were examined. Initially the vibrational characteristics of the structures were measured without fluid flow. Subsequently, each structural vibration was measured under various flow rates through the CDCF system. The structural vibration was measured using strain gages attached to the structures as well as non-contact displacement sensors. Time histories of the strains and displacements were obtained, and their time averages and the vibrational magnitudes were computed as a function of the nominal flow rate through the channel cross-section. This set of test data is expected to be useful for validation of a computer program for analyzing a FSI problem.

Picoplatin-based complexes with the bioactive orotate and 5-fluoroorotate ligands: Synthesis, DFT calculations, structure, spectroscopic characterization and in vitro cytotoxicity

Two novel, sterically hindered platinum(II) complexes Pt(Oro)(NH3)(2-pic), 1, and Pt(5-FOro)(NH3)(2-pic), 2, were synthesized by connecting the cis-[Pt(NH3)(2-picoline)]2+ fragment of picoplatin (new anticancer agent, being currently under clinical trials) with the chelating orotate or 5-fluoroorotate bioactive ligands. The complexes were characterized in depth using IR, Raman and multinuclear (1H, 13C, 19F, 195Pt) NMR spectroscopy, high resolution mass spectrometry (ESI-TOF), elemental analysis and thermogravimetry. The experimental vibrational spectroscopic studies combined with the theoretical (DFT) calculations were indispensable to elucidate the molecular structures of these complexes. A complete assignment of the IR and Raman spectra was made on the basis of the calculated potential energy distribution (PED). The spectroscopic (FT-IR and NMR) data have shown that of two possible isomers of each complex, just one isomer (A) exists in the solid state and in DMSO solution. Interestingly, the DFT calculations with the PBE0 and B3LYP methods have revealed that the other isomer (B) with the intramolecular NH⋅⋅⋅O hydrogen bond is more stable than A, in the gas phase. It is concluded that during the synthesis the steric and kinetic effects of the 2-picoline ligand play the dominant role, therefore, the isomer A is formed. The antiproliferative activity of 1, 2 and 5-fluoroorotic acid (3) was evaluated in vitro against several human cancer cell lines. The studied compounds exhibited larger IC50 values, in comparison to cisplatin, however 1, 2 and picoplatin showed much lower toxicity against the normal cell lines as compared with cisplatin. Complex 2 was significantly more potent than 1, 3 and picoplatin against HT-29 (human colorectal adenocarcinoma).

Dynamic Responses of a Four-Span Continuous Plate Structure Subjected to Moving Cars With Time-Varying Speeds

This paper presents an experimental and theoretical study of vibration of a four-span continuous plate with two rails on top and four extra supports excited by one or two moving model cars, which is meant to represent vehicle–track–bridge dynamic interaction. Measured natural frequencies of the plate structure are used to update the finite element (FE) model of the structure. Four laser displacement transducers are placed on the ground to measure the displacements of the plate. A laser-Doppler vibrometer is used to measure the real-time speed of the moving cars, which reveals that the speeds decrease with time at a small and almost constant deceleration which can affect the structural dynamic response. A fascinating experiment is the use of two cars connected in series, which is very rare and has never been done on a multispan structure. Vibration of the plate structure excited by two moving cars separated at a distance is also measured and exhibits interesting dynamic behavior too. A theoretical model of the whole structure is constructed and an iterative method is developed to determine the dynamic response. The numerical and the experimental results are found to agree very well, in particular when deceleration is considered in the theoretical model.

Experimental and theoretical vibrational study of N-carbamoyl-L-proline

The infrared and Raman spectra of N-carbamoyl-L-proline, C6H10N2O3 [(2S)-1-carbamoylpyrrolidine-2-carboxylic acid] were obtained and interpreted with the help of DFT calculations. Six relatively stable molecular conformers were predicted by theory, being one of these similar to the conformer present in the crystal whose X-ray study was already known. The vibrational study was based in that conformer. The experimental vibrational data and assignments were used as basis for the definition of the Scaled Quantum Mechanics (SQM) force field for the molecule. The Potential Energy Distribution (P.E.D.), which revealed the complex nature of many molecular vibrations, and a set of internal force constants were calculated from this SQM force field.

Экспериментальное и теоретическое исследования колебаний твердого тела со слоистой жидкостью

Экспериментальное и теоретическое исследования колебаний твердого тела со слоистой жидкостью

Experimental study of dual-impeller string vibration in a baffled mixing vessel

Vibration characteristics of 45∘ pitched blade impellers (PBIs) operating in a standard baffled mixing vessel were studied. Experiments were conducted for eight different impeller configurations with combinations of: numbers of impellers (single or double), diameter to tank diameter ratios D/DT = 1/2 and 5/7, and impeller spacing of 0, 0.75D, and 1.5D. The impeller orbit frequency and shape, mean square deflection, and phase relationship were studied with a glycerine-water mixture having Reynolds number, Re≤ 5000, and N/Ncrit≤ 1.2. Two high speed cameras were used to measure two orthogonal components of lateral impeller deflection. It was observed that the impeller orbits are periodic at low speed and exhibit chaotic motion at high speed which can be modelled using a random normal distribution. The mean square deflection continues to grow beyond N*>1 exponentially, and the addition of a second impeller increases the mean square deflection. Frequencies associated with impeller orbits for the D/DT = 1/2 showed that at low rotational speeds, the highest energy in power spectra of the impeller deflection is at twice the impeller rotational speed. With an increase in rotational speed, the energy in the power spectra shifts to synchronous and finally subsynchronous range with a broad band character. The phase relationship and whirl direction of top and bottom impeller were found to be dependent on the rotational speed and impeller spacing.

Investigations of self-excited vibration in splitter plate with a cavity in the supersonic mixing layer

The combustion efficiency strongly depends on the mixing process of fuel–air for a combined cycle engine. For an efficient mixing process, self-excited vibration of splitter plate is more practical than that of forced vibration. We have carried out a comprehensive numerical and experimental study of self-excited vibration. Finite element method (FEM) is applied to analyze the natural modal of vibration. Large eddy simulations (LES) are employed for the mechanistic study of self-excited vibration and their influence factors are evaluated from the experimental studies. Displacements are accurately measured by a non-intrusive laser vibrometer. It is found that the first-order vibration shape is quasi-two-dimensional and responsible for improved mixing. We found that self-excited vibration of the splitter plate is motivated by a cavity due to the acoustic self-oscillation. Moreover, self-excited vibration depends on the gap distance between fixed rod and splitter plate, static pressure difference between upper and lower nozzle outlet, length to depth ratio (K) and aft wall angle (θ). At zero gap distance, the frequency is up to 2.5 times higher than that of 3 mm gap distance. So, reduction in gap distance can efficiently increase the frequency of self-excited vibration, which is an encouraging point for the future study.

An experimental study of vortex-induced vibration of a circular cylinder in a shallow open channel

An experimental study of vortex-induced vibration of a circular cylinder in a shallow open channel

Nonlinear damped vibrations of planar discrete systems - numerical and experimental modelling

The consistently conducted analytical, numerical and experimental studies of nonlinear damped vibrations of planar discrete systems are presented in the paper. The combined methodology is applied to a horizontal vibrating system, consisting of two translational moving bodies connected by three springs. The non-linear nature of the damping is due to the dry friction forces accompanying the vibrating process. The mathematical model of the vibrating system is composed in a matrix form by the second order Lagrange equations. Numerical studies are realized in two ways. Firstly, in the Simulink environment, a simulation model was composed. Then, in the MATLAB environment, an animation model was developed using the third animation method offered by the programming system. The experimental studies were conducted by stand for study the small vibrations of discrete planar systems. The stand is part of the experimental equipment of the Lab for numerical and experimental dynamic modelling, UACEG, Sofia, Bulgaria. (www.dlab-uacg-bg.eu). All models - the dynamic model and its corresponding mathematical, simulation, animation and experimental model are open to additional bodies to obtain discrete vibrating systems with a larger number of degrees of freedom.

FT-IR spectra of the anti-HIV nucleoside analogue d4T (Stavudine). Solid state simulation by DFT methods and scaling by different procedures

A theoretical and experimental vibrational study of the anti-HIV d4T (stavudine or Zerit) nucleoside analogue was carried out. The predicted spectra in the three most stable conformers in the biological active anti-form of the isolated state were compared. Comparison of the conformers with those of the natural nucleoside thymidine was carried out. The calculated spectra were scaled by using different scaling procedures and three DFT methods. The TLSE procedure leads to the lowest error and is thus recommended for scaling. With the population of these conformers the IR gas-phase spectra were predicted. The crystal unit cell of the different polymorphism forms of d4T were simulated through dimer forms by using DFT methods. The scaled spectra of these dimer forms were compared. The FT-IR spectrum was recorded in the solid state in the 400-4000 cm−1 range. The respective vibrational bands were analyzed and assigned to different normal modes of vibration by comparison with the scaled vibrational values of the different dimer forms. Through this comparison, the polymorphous form of the solid state sample was identified. The study indicates that d4T exist only in the ketonic form in the solid state. The results obtained were in agreement with those determined in related anti-HIV nucleoside analogues.

Numerical and experimental study of wheel-rail impact vibration and noise generated at an insulated rail joint

As essential track components for rail connections and signal transmission and control, insulated rail joints (IRJs) have been widely used in traditional and high-speed railways. However, the IRJ is considered as one of the weakest parts of railway track structures due to the significant discontinuities in stiffness and geometry. When a train runs over an IRJ, a wheel-rail impact occurs and it increases with train speed. The impact consequently leads to vibration and noise and accelerates track deterioration in the vicinity of the IRJ. This paper establishes an explicit finite element wheel-IRJ dynamic interaction model to simulate high-frequency impact vibration and noise generated at a typical IRJ in the Dutch railway network, and validates the model against a comprehensive hammer test and a pass-by measurement. Good agreements between the simulation and measurements indicate that the proposed model can effectively reproduce high-frequency impact vibration and noise up to 10 kHz. This paper also connects the dominant frequencies of wheel-IRJ impact vibration and noise with the dynamic behaviour of the target IRJ, which may contribute to the mitigation of impact vibration and noise at IRJs as well as to train-borne detection of deterioration types of IRJs.

An experimental study of ground-borne vibration from shield tunnels

Along with the ongoing development of urban railways, ground-borne vibration from trains has received considerable attention in the past decades. Various research studies have been conducted to study this problem. In order to simplify the problem for analysis, it us commonly assumed that tunnels have a uniform lining; however in reality this usually not the case. With the development of shield tunnelling, precast segmental linings are widely used. The existence of the joints between tunnel segments can significantly affect the dynamic behaviour of the tunnel. In this paper, results from a series of physical model experiments are described to explore the dynamic characteristics of segmental tunnel linings. Three different tunnel lining models were tested: uniform, straight–jointed segments, and stagger–jointed segments. In the experiments, vibration excitation was applied to the model tunnel invert by a shaker. The tunnel and soil responses at different locations were measured by accelerometers during the tests. Comparison of the results from the different tunnel lining models shows that the segment joints have a considerable effect on the dynamic behaviour of the tunnel lining. Due to the effects of interface damping at the segment joints, the response of both types of segmental linings was found to be significantly smaller than the response of the uniform tunnel lining. The experimental results also show that the segment joints have less impact on the soil response and mainly affect the soil response in the frequency range below 80Hz.

Numerical and experimental studies of longitudinal and longitudinal-torsional vibrations in drilling of AISI 1045

Conventional drilling (CD) which is known by two rotary and linear motions is considerably used in material removal processes; however, this method cannot satisfy the new demands of modern industry anymore, encountering with some serious technological constraints such as fast tool wear, high thrust force, and so on. A new and promising method which has been used recently as an alternative technique to cope or at least diminish common difficulties in CD is imposing ultrasonic vibrations to the cutting process, where vibrations usually with high frequency and low amplitude are superimposed in the movements of cutting tool. This study is a new exercise which considers the effects of one and two directional ultrasonic vibrations in drilling of AISI 1045 compared to CD. In one directional technique known as longitudinal ultrasonic assisted drilling (L UAD), ultrasonic vibrations are added to the feed motion and in two directional vibrations; ultrasonic vibrations are simultaneously applied to both feed and rotary motions known as longitudinal-torsional ultrasonic assisted drilling (L-T UAD). The study which is performed both experimentally and numerically does its best to evaluate and compare the obtained results in CD, L UAD, and L-T UAD. In experimental part, a system including two vibratory tools and a rotary mechanism is designed, fabricated, and then assembled with other equipment on a milling machine to accomplish drilling tests. In numerical part, a FE model is also developed with the aim of further understanding of experimental results, by which drilling operations either conventional or vibratory in different forms can be conducted and studied. As a brief conclusion, it was found that ultrasonic vibrations can be used as an effective tool for enhancement of drilling process and longitudinal-torsional vibrations reveal better results than longitudinal vibrations.

EXPERIMENTAL STUDY OF THE DYNAMICS OF CENTRIFUGAL CASTING MACHINES FOR PRODUCTION OF MILL ROLLS

Purpose. The main purpose of experimental studies is to establish the adequacy of the developed mathematical models of machine fluctuations and the actual parameters of machine vibration. Almost all casting machines for the production of mill rolls have a unique design and performances. The additional aim of this work is to compare the vibration level of the casting machine with the requirements of the current vibration standards for new technological machines. Frequency analysis of the oscillations allows establishing defects in workmanship, errors of rotating parts installation and their influence on the dynamics of the machine. Methodology. Measurement of vibration parameters was performed on the moving parts of roller bearings of the machine. To measure the amplitudes of accelerations in three mutually perpendicular directions piezoelectric sensors with magnetic mount were used. Electrical signals from the sensors were recorded on magnetic tape. Further analysis of the oscillations was carried out and visualized using specialized frequency analyzer. The frequency analyzer implements the algorithm of fast Fourier transformation and/or integration of sensor input signal. After the first integration the data for plotting the vibration velocity spectrogram were obtained and as a result of the second integration there are the data of vibration displacements spectrogram of the machine supports. Findings. The results of experimental studies of centrifugal casting machine vibrations for the production of two-layer rolls were presented. There were obtained and analyzed the spectrograms of accelerations, velocities and displacements of moving parts of the upper and lower roller supports. The work of the machine is associated with the calculated values passing of critical frequencies and the short-term development of resonance oscillations of the rotor and roller bearings. Originality. For the first time the author obtained the frequency spectra of vibration of an industrial sample of a casting machine. The oscillations with frequencies that differ from the basic rotor frequency were detected. Practical value. Based on the results of the experiment, the actual vibration parameters of the machine in steady state when testing without die-casting the metal were determined. The adequacy of mathematical models of the dynamics of the machine and its industrial model was established. Using the method of one tone the coefficients of vibration velocity distortion of the rotor harmonic, indicating the nonlinear transformations in the system "rotor - bearings" were obtained. It was experimentally established that the vibration parameters of the machine are within the acceptable ranges, regulated by standards for vibroactive machines.

Synthesis, experimental and theoretical vibrational studies of 1-methyl and 1,2-dimethyl, 3-propyl imidazolium bis(trifluoromethanesulfonyl) imide

In this study, two ionic liquids containing the bis(trifluoromethanesulfonyl)imide ( $$[(\hbox {CF}_{3}\hbox {SO}_{2})_{2}\hbox {N}^{-}]$$ ) anion are synthesized. The syntheses are based on an alkylation reaction of 1-methyl imidazole and 1,2-dimethyl imidazole followed by anion exchange. The obtained ILs are characterized by $$^{1}\hbox {H-NMR}$$ , $$^{13}\hbox {C-NMR}$$ , $$^{19}\hbox {F-NMR}$$ and FT-IR spectroscopy. Vibrational spectroscopy studies were conducted by infrared (FTIR/ATR), Raman spectroscopy and DFT calculations. The presence of methylation in the C2 position gives rise to specific marker bands in the Raman and IR spectra. In order to ascertain whether cation conformers are present in our ionic liquids, a computational study was performed using the density functional theory. The comparison of the experimental data and the computed spectra shows that three conformers of the imidazolium ions are present in both ionic liquids. Synopsis We synthesized and investigated the vibrational properties of two ionic liquids, namely, 1-methyl,3-propyl imidazolium bis(trifluoromethane-sulfonyl) imide ( $$[1\hbox {-MPrIM}^{+}][(\hbox {CF}_{3}\hbox {SO}_{2})_{2}\hbox {N}^{-}]$$ ) and 1,2-dimethyl,3-propyl imidazolium bis(trifluoromethane-sulfonyl) imide ( $$[1,2\hbox {-DMPrIM}^{+}][(\hbox {CF}_{3}\hbox {SO}_{2})_{2}\hbox {N}^{-}]$$ ). Methylation in the C2 position gives rise to specific marker bands in the Raman and IR spectra. The comparison of the experimental data and the computed spectra at DFT level shows that three conformers of the imidazolium ions are present in both ionic liquids.