Vibrational Frequencies Research Articles

Resonance and surfactant effects on the interaction of a rising bubble and a sedimenting particle in an oscillating fluid

This paper considers the interaction of a rising bubble and a sedimenting fine particle in a liquid with a soluble surfactant subjected to the gravity field, forced flow, and vibrations. The frequency of vibrations is close to the resonance value. The particle motion trajectories are calculated, taking into account its inertia, fluid viscosity, Basset force, buoyancy force, and the mean force acting on the particle due to the inhomogeneity of the pulsating field. The collision efficiency is evaluated, and the cross sections of the sedimenting particles captured by the rising bubble are found. It is demonstrated that even at low vibration intensity but in the presence of a weak surfactant effect, a significant increase in the probability of particle–bubble collision and in the capture cross section can be achieved. The obtained results can be used to intensify the flotation processes by ultrasonic treatment.

A thermal flexible rotor dynamic modelling for rapid prediction of thermo-elastic coupling vibration characteristics in non-uniform temperature fields

The flexible rotors within aero-engines operate in complex thermal environments, where temperature influences both the vibration frequency and amplitude. This study establishes a simple thermal flexible rotor dynamics model to rapidly and precisely predict thermo-elastic coupling vibration characteristics within a non-uniform temperature field. The thermal potential energy of the thermal rotor element is derived for any temperature field, and the motion equation is obtained using the Euler-Lagrange equation. Specifically, the generalized vector of an arbitrary point and cross-sectional non-uniform thermal stress of the thermal rotor element are considered in the thermal potential energy. The model's frequency error is less than 1% under identical boundary conditions. Numerical findings indicate that thermal stress, temperature-dependent material properties, and the coupling effect collectively reduce the natural frequency (NF), with thermal stress having a more pronounced impact under axial constraint. Additionally, thermal stress and material decrease the amplitude across a broad range of rotation speeds, contrasting with thermal bending. This model will play a key role in the iterative calculation of thermo-elastic coupling vibration control due to its accuracy and simplicity.

Effect evaluation of fluid movement and rock properties for artificial seismic activity on hydrocarbons

Despite the effectiveness of seismic stimulation in enhancing oil production from reservoirs, the impact of high-frequency vibrations on oil droplets confined within pore throats has not been adequately investigated. This laboratory-scale experimental study examines the impact of low and high-frequency sinusoidal vibrations in dislodging oil droplets trapped in a specific pore-throat region. Sinusoidal vibrations ranging from 10 to 80 Hz and with maximum displacement amplitudes of 1.2–0.06 mm are applied. By comparing the images captured prior to and after the application of seismic vibrations, the amount of oil recovered is determined. Commercial gasoline and diesel are used as trapped oil samples, and water is used as the injection fluid to bring out the effect of fluid viscosities in seismic dislodgment. While applying vibrations to trapped oil in the pore throat, three different recovery modes are observed: continuous, snap-off, and emulsified. The continuous oil recovery mode is observed in cases with minimal flow resistance through the pore throat, whereas a snap-off or intermittent recovery mode is observed when the flow resistance is high, and the vibration frequencies fall within the midrange of 40-60 Hz. An emulsified oil recovery mode is observed at high vibration frequencies. The amount of recovered oil increases as geometrical restrictions and trapped oil viscosity decrease. Seismic mobilization is observed to be directly proportional to the mobilization velocity and inversely proportional to the entrapped oil viscosity and geometrical restriction factors.

Based on the Fuel Cell Stack Vibration Test and Evaluation Method under the Actual Operation Scenario of Vehicles

Abstract Based on the application scenario of fuel cell vehicle, a test and evaluation method of bench vibration of fuel cell stack based on actual operation requirements is proposed in this paper. Firstly, the application requirements of logistics vehicles are analyzed, and the impact of vibration and shock on fuel cell piles under different road conditions is studied. Secondly, based on the condition of the proportion of the road used by the logistics vehicle, based on the principle of user correlation and other damage, a bench vibration test method based on the use scenario of the logistics vehicle is proposed. The research shows that the fuel cell stack has the maximum vibration frequency at 50hz, and there is basically no vibration frequency above 200HZ.

Inflated electronic and optical assessment of gC3N4/ZnO nanocomposite as a potential emissive layer material for OLED application

Organo-inorganic nanocomposite materials have been proven to be novel hybrid materials with inflated electronic and optical performance that can be tailored with the judicious selection of the building units or their combinations. Here, hydrothermal, thermal polycondensation, and ultrasonication techniques were used to synthesize pure ZnO, gC3N4, and gC3N4/ZnO with varying weights % such as 10%, 15%, 20%, and 25% of ZnO inorganic filler elements in gC3N4 matrix. The crystalline phase (hexagonal wurtzite) and crystallite size (10.0 nm, 17.6 nm, and 15.90 nm) of the synthesized materials were examined by X-ray diffractometer. The FESEM and HRTEM characterizations revealed the sheet-like gC3N4 and spherical-type ZnO nanoparticle-like microstructures of the samples. The present functional groups, corresponding vibrational frequency, chemical states, and binding energy were investigated using FTIR and XPS spectroscopic methods. Optical parameters such as optical band gap energy (Eg = 3.24 eV), Urbach energy (Eu = 0.41 eV), refractive index (n= 1.99), emission quantum yield (∼ 69.03%), and color purity of the nanocomposites were examined using UV visible and photoluminescence spectroscopic techniques. IV and Hall measurements techniques were used to determine the semiconducting parameters of the optimized sample, such as conductivity (∼62.90×10−5 S/cm), carrier mobility (∼ 44.1 cm2/Volt. Sce), carrier concentrations (∼1.825×1014 cm−3), and sheet resistance (∼1.062×103 Ω/cm2). Due to their excellent optical and electrical behavior, the nanocomposite materials were found to be fairly suitable as a potential emissive layer material for OLED applications.

Ultrasonic vibration-assisted high-resolution electrohydrodynamic (EHD) printing

Electrohydrodynamic (EHD) printing has become a promising and cost-effective technique for producing high-resolution and large-scale features. One widely recognized obstacle in EHD printing is nozzle clogging due to solvent evaporation or ink polymerization. Moreover, printing highly viscous materials often requires pressure or other external force to assist the ink flow during the printing, which increases the complexity of process control and the required energy. In this work, we developed a novel ultrasonic vibration-assisted EHD printhead and associated process to effectively eliminate the nozzle clogging for the printing of high-viscosity and high-evaporation-rate inks. A series of experimental tests were conducted to characterize the printhead design and process parameters (i.e., vibration frequency, vibration amplitude, and printing voltage). The results demonstrated that superimposing ultrasonic vibration on the EHD printing nozzle can effectively enhance current EHD printing capabilities, such as reducing required pressure, eliminating nozzle clogging, and providing stable and continuous printing for high viscosity and high solvent evaporation rate material. With the optimal parameters, a filament with a diameter of around 1 µm can be continuously printed. In the paper, we successfully applied this developed ultrasonic-assisted EHD process to print high-resolution 2D patterns.

Frequency identification method based on active aliasing of biprobes blade tip timing without once-per-revolution

Rotary blades are the core components of aeroengines, gas turbines and centrifugal compressors. However, due to the complexity of their work environment, monitoring their health is necessary. Blade tip timing (BTT) is an effective non-contact monitoring method for rotating blades. However, conventional BTT rely heavily on once-per-revolution (OPR) signals, which cannot be accurately obtained in complex environments. At the same time, there is a serious under-sampled problem in the BTT signal. Consequently, the extraction of blade vibration parameters from under-sampled BTT signals without relying on OPR signals remains a research hotspot. In this paper, an active aliasing method based on the vibration difference of the blade is proposed to extract the vibration frequency of the blade. In the proposed method, two BTT probes are used to calculate the blade vibration difference, and time delay estimation is used to estimate the approximate value of the natural frequency at small angle delays. Then, a series of aliasing frequencies are generated under various large angle delays. Next, the estimated natural frequency and aliasing frequency are combined to solve the exact natural frequency value. In addition, numerical simulations demonstrate the effectiveness and robustness of the method. Finally, experimental research was conducted on the BTT experimental platform. As a result, this method can accurately identify the inherent frequency of asynchronous vibration of the blades.

Ultrasonic Vibration-assisted Tube Extrusion Shear Expansion (UVaTESE): A Novel Process to Manipulate the Texture of AZ31 Magnesium Alloy

AZ31 magnesium (Mg) alloy prepared via the extrusion process forms an immensely strong {0001} basal texture, therefore there is a necessity to improve the existing extrusion process to achieve a weakening of the {0001} basal texture of the AZ31 Mg alloy. In this study, a novel process called UVaTESE is proposed. The Mg alloy texture and slip system activation at four ultrasonic vibration (UV) frequencies have been simulated via ABAQUS-VUMAT and VPSC, individually. The simulation results indicate that UV is capable of diffusing the {0001} basal texture of the Mg alloy along the extrusion direction (ED) and transverse direction (TD) and significantly improves the activation of pyramidal slip <c+a>. The simulations are verified experimentally, and the {0001} basal texture of AZ31 Mg alloy has the identical tendency to disperse along ED and TD. Prismatic slip <a> and pyramidal slip <c+a> jointly lead to diffusion of the grain basal texture along the TD, while grains with basal texture diffused along the ED are controlled by both basal slip <a> and pyramidal slip <c+a>. UV has a positive effect on the grain refinement as well as on the homogeneity of AZ31 Mg alloy. The proportion of dynamic recrystallization (DRX) of AZ31 Mg alloy is proportional to the frequency of UV, and it is noteworthy that the mechanism of DRX behavior is not affected by UV. This novel process provides a fundamentally innovative approach to the preparation of Mg alloys and magnesium-aluminum (Mg-Al) composite tubes via extrusion.

The experimental research of which different types of impact signals affect the bifurcation chaos behavior of three-degree-of-freedom collision system

Abstract Collision is a faulty behavior in mechanical equipment, which greatly affects the safety of equipment. In this paper, aiming at the collision failures that are prone to occur in mechanical equipment, the nonlinear fault collision behavior of a class of three-degree-of-freedom collision systems is studied. A three-degree-of-freedom piecewise non-smooth collision experiment platform system has been established to facilitate further analysis of the bifurcations and chaos inherent to the bearings system. This analysis is conducted through the use of Poincaré mapping on the collision plane. The excitation signals employed, which include sinusoidal, triangular, and rectangular signals, result in the emergence of specific types and orders of bifurcation behaviours within the system, as evidenced by the establishment of a Poincaré mapping at the collision surface, and this is observed to occur as the vibration frequency increases. The characteristics of impact signals generated by force sensors and the influence of impact signal type on the system are investigated. The nonlinear impact behavior of three-degree-of-freedom collision systems provides a reliable foundation for the design, fault diagnosis, and theoretical guidance of large-scale high-speed rotating machinery, as well as technical support for safe and stable operation of high-speed rotating machinery, which is essential for failure analysis and vibration reduction in equipment.

Numerička analiza titrajnog odziva dalekovoda velikog raspona prijenosnih vodova izazvanog vjetrom

Based on the engineering background related to ±800 kV ultra-high voltage (UHV) transmission lines spanning the Yellow River, finite element models were developed for single-tower and transmission tower-line systems, with their wind-induced responses under wind loads were simulated and analysed. In addition, the coupling effect in a large-span transmission tower line system was investigated. The results showed that the natural vibration frequency of the tower-line system was slightly lower than that of a single tower and that the torsional natural frequency was the most significantly reduced. The transmission tower-line system has a maximum displacement of 1.92 times that of a single tower when the wind angle is 0°. The maximum axial force and stress in the tower-line system are 1.6 times and 1.37 times higher than those in a single tower. The interaction between the tower and wires significantly affects the wind-induced response of the tower body. Hence, considering the dynamic coupling effect of the tower-line transmission system is important when designing a tower.

Close Range and High-Resolution Detection of Vibration by Ultrasonic Wave Using Silicon-on-Nothing PMUTs.

This article presents a novel method for close-range, high-resolution ultrasonic time-of-flight (ToF) ranging using piezoelectric micromachined ultrasonic transducers (PMUTs) operating below the device resonance in air. The proposed method involves cross correlation techniques to accurately detect the reflected echo signals despite the presence of ringdown signal interference. For the experiments, a high fill-factor array of silicon-on-nothing (SON) PMUTs was used to enhance the signal-to-noise ratio (SNR). A thorough investigation was conducted to determine the optimal driving frequency for below-resonance ToF ranging, to improve resolution and minimize detection errors. The results of the experiments showed that the system was able to accurately measure sub- μ m vibrations of a metal plate placed 13 mm away from the PMUT array. The system exhibited the ability to detect target object vibrations with a peak-to-peak displacement under 6 μ m and sub- μ m floor noise. Moreover, the maximum detectable vibration frequency reached up to 1 kHz. This study highlights the potential of the proposed ToF ranging method in noncontact vibration monitoring applications across various fields, such as robotics and predictive maintenance.

Vibration modal analysis of adaptive grinding and polishing tools

Abstract Adaptive grinding and polishing tools have a compact structure, fast response, and stable performance, and they can improve the efficiency of polishing and grinding large welded parts. The vibration frequency of the AGP600 adaptive grinding and polishing tool is abnormal after switching from the blade grinding head to the nylon grinding head, and the vibration is noticeable when the rotational speed is more significant than 4, 000 r/min, which seriously affects the quality of grinding. To analyze the cause of its vibration, this paper adopts HyperWorks to analyze the modal frequency of AGP600, carries out the vibration modal test, and analyses the reasons for the different vibration harmonic frequencies of AGP600. Finally, improvement measures for AGP600 are proposed, through which the vibration of AGP600 grinding tools can be reduced.

Designing of new functionalized imidazolium based ionic liquids attached to the antracene derivatives and investigation on the influence of intramolecular hydrogen bondings in anions on their intermolecular hydrogen bondings and some of the other properties: A DFT M06-2X-GD3 study

To promote the development of new functionalized ionic liquids, it is necessary to get a deeper insight into their features of physicochemical and electronic and molecular structure. In this study, the interaction energies and structural and vibrational frequencies parameters in accompanied with some of the physiochemical, electronic and optic attributes of ionic liquids designed by the covalently attachement of imidazolium to anthracene derivatives ([X-AnMIM][A2] and [X-AnMIM][A3], X: NH2, OH, OMe, H, Cl, CHO, CN and NO2) ILs have been evaluated. Two conjugate bases of acids 1,3,5-pentanetriol (A2) and 3-(2-hydroxyethyl)-1,3,5-pentanetriol (A3) are used as anions which have two and three intramolecular hydrogen bonds, respectively. Based on the results of calculations at M06-2X-GD3/6-311++(d,p) level of theory, the differences in these properties in addition to the structural type of anions and cations can be attributed to the cation- anion , intra and intermolecular hydrogen bonding, interactions in ionic liquids. The results depict that the ILs based on A2 anions form stronger hydrogen bonds with [X-AnMIM]+ cations. The potency of interaction between cations and anion reduces with the increasement in the number of intramolecular hydrogen bonds and also decreasement in the basic strength in the anionic part. A clear red shift is observed between [X-AnMIM][A2] and [X-AnMIM][A3] ILs and isolated anthracene, which is a clear manifestation of the effect of the imidazolium cation on the electronic energy levels of anthracene. It can be expected that the studied ILs are not electrochemically stable during the electrochemistry applications.

A novel double-arch piezoelectric energy harvester for capturing railway track vibration energy

This study introduces a novel piezoelectric stack energy harvester with a double-arched frame structure. This design effectively cushions impacts from track vibrations, thereby protecting the fragile piezoelectric stack made of brittle materials. The energy harvesting characteristics of the device are studied in detail through experiments and theoretical simulations. The harvester's output voltage depends on the external resistance and increases with higher resistance. The optimal resistance for the single X-direction piezoelectric stack is 340kΩ, which can output 0.519mW of power under a 3Hz frequency and an 8kN sinusoidal load. The Y-direction piezoelectric stack outputs 0.012mW, resulting in a total output of 1.050mW for the entire harvester. The output power of the harvester is positively correlated with the load vibration frequency, increasing rapidly for frequencies below 9Hz. The impact of load magnitude on the harvester's output shows a generally linear increase. In impact experiments, the single X-direction piezoelectric stack successfully lit 54 LEDs under a 5J energy impact, demonstrating the harvester's high power density and potential for practical applications.

Study on the Transition Mechanism of Vibrating Low-Pressure Turbine Blades Based on Large Eddy Simulation

The low-pressure turbine blades are susceptible to vibration issues due to their thin profiles and large aspect ratios. Blade vibration will significantly affect the evolution of the boundary layer and the flow state. This paper utilizes large eddy simulation to predict the development of the boundary layer on the suction side of low-pressure turbine blades at low Reynolds numbers (Re = 25,000). It introduces different vibration cases to elucidate the mechanisms by which blade vibrations influence boundary layer separation and transition. The study demonstrates that the introduction of vibration cases significantly reduces both the size of the overall spanwise vortices and their roll-up height. A staggered distribution of spanwise vortices, characterized by alternating high and low regions, is observed near the trailing edge of the vibrating blades. The shorter spanwise vortices develop rapidly, nearly traversing the process of hairpin vortices (Λ vortex) generation and development, and directly breaking down into smaller-scale vortices. This accelerates the transition process. Blade vibration primarily promotes turbulence reattachment by facilitating the transition process dominated by the K-H instability mechanism within the separating shear layer. Consequently, it effectively restricts the growth of the separation bubble on the suction side of the blades, significantly reducing aerodynamic losses. Moreover, increasing the vibration frequency within a certain range can amplify these effects, achieving up to a 23% reduction in total pressure loss compared to stationary blades.

A new magnetic negative stiffness mechanism: A case study of Fast Steering Mirror for quasi-zero stiffness vibration isolation

Quasi-Zero Stiffness (QZS) is essential for low-frequency passive vibration isolation, with the negative stiffness mechanism (NSM) being pivotal for achieving QZS. Mechanical spring-based NSMs often face issues like contact friction, parasitic high-frequency modes, and stiffness nonlinearity. This paper presents a new magnetic NSM designed to overcome these challenges effectively. The mechanism is applied to a Fast Steering Mirror (FSM) as a case study, enhancing its vibration isolation performance. Initially, a torque model for the magnetic NSM is established, exploring the impact of various structural dimensions on torque and nonlinear issues. The magnetic NSM features adjustable negative stiffness and a large, adjustable linear working range. Experiments were designed to validate the principle of the magnetic NSM and its effect on the QZS FSM’s vibration isolation performance. The experimental results confirm the accuracy of the magnetic NSM principle. The QZS FSM stiffness is significantly reduced to quasi-zero stiffness, resulting in a decrease of the resonance peak from 20.1 to −12.8 dB and lowering the minimum suppressible vibration frequency from 54.63 to 3.44 Hz, thereby enhancing the vibration isolation performance of the QZS FSM.

Design, synthesis, and evaluation of some metal ion complexes of mannich base derived from 2-Mercaptobenzimidazole as potential antimicrobial agents

This study aims to prepare new compounds and investigate them spectroscopically and biologically against selected types of positive and negative bacteria and fungi to demonstrate their biological effectiveness. The prepared ligand combining formaldehyde, indole, sulfa benzamide, and 2-mercapto benzimidazole, a Mannich base ligand (L) was synthesized. The six metal ions including Cobalt (II), Nickel (II), Copper (II), Palladium (II), Platinum (IV), and gold (III) have interacted with the ligand and formed new complexes. Different spectroscopic methods, including C.H.N.S., FTIR, UV- Range visible, 1HNMR, 13CNMR, mass spectra, magnetic moment, and molar conductivity were used to suggest the new geometry of the complexes. The result from the infrared spectrum showed that the ligand behaves as tridentate with all prepared complexes. Conductivity analysis revealed the electrolytic nature of palladium, platinum, and gold ions complexes and non-electrolytes. The antibacterial activity of the compounds that were produced was tested using an agar-well diffusion procedure towards two strains of gram-positive as well as two strains of gram-negative bacteria and fungi (Staphylococcus, Streptococcus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans) respectively at 0.02M. The standard (∆Eo) and (∆Hfo) of ligand and six complexes were calculated using the program Hyper chem 8.0.7. The research established that complexes are more stable than ligands. Calculated HOMO and LUMO and vibration frequencies using (parametric method 3 (PM3)) to find out the active sites in the ligand showed that they can coordinate and note the extent to which the results of theoretical vibrational frequencies are close to the process when calculating the vibrational frequency of the active aggregates.

Numerical analysis and experimental research on the vibration performance of concrete vibration table in PC components

Abstract Vibration table is the key equipment to realize high efficiency and high quality forming and compacting of concrete in prefabricated component (PC) production line, and its performance directly affects the shape quality and compressive strength of PC components. However, the operating parameters of the vibration table are difficult to match the rheology of the concrete during the construction process, which directly leads to a low molding efficiency or unqualified shape quality in the case of slab-type components. Therefore, it is crucial to accurately describe the concrete flow behavior during vibration to improve the construction performance and compaction effect. In this work, the coupled theory of computational fluid dynamics and discrete element is used to study the concrete vibration and compacting characteristics, and the influence of process parameters on vibration performance is analyzed in order to realize the adjustment and optimization of key parameters. First, the concrete solid-liquid two-phase model parameters are calibrated by V-shaped funnel experiments and slump experiments. Then, based on the simulation results, the homogeneity and compactness of concrete are discussed using the segmented sieving method and the slicing method, and the indexes for evaluating the working performance of the vibration table are proposed. Finally, the relationship between vibration frequency (20–30 Hz), vibration amplitude (3–4 mm), and vibration time (15–35 s) and concrete vibration compaction characteristics is investigated to provide a theoretical basis for improving the molding efficiency and mold quality of PC components.

Frequency stabilization of self-sustained oscillations in a sideband-driven electromechanical resonator

We present a method to stabilize the frequency of self-sustained vibrations in micromechanical and nanomechanical resonators. The method refers to a two-mode system with the vibrations at significantly different frequencies. The signal from one mode is used to control the other mode. In the experiment, self-sustained oscillations of micromechanical modes are excited by pumping at the blue-detuned sideband of the higher-frequency mode. Phase fluctuations of the two modes show near-perfect anticorrelation. They can be compensated in either of the modes by a stepwise change of the pump phase. The phase change of the controlled mode is proportional to the pump phase change, with the proportionality constant independent of the pump amplitude and frequency. This finding allows us to stabilize the phase of one mode against phase diffusion using the measured phase of the other mode. We demonstrate that phase fluctuations of either the high-frequency mode or the low-frequency mode can be significantly reduced. The results open new opportunities in generating stable vibrations in a broad frequency range via parametric down-conversion in nonlinear resonators. Published by the American Physical Society 2024

Frequency studies of nonlinear TSDT FGM plates in the linear shear corrections and thermal environment temperature

The effects of third-order shear deformation theory (TSDT) and varied linear shear correction coefficient on the vibration frequency of thick functionally graded material (FGM) plates with fully homogeneous equations under thermal environment and power law are investigated. The nonlinear coefficient c_1 term of displacement field of TSDT is included in the fully homogeneous equation under vibration of FGM plates. The determinant of the coefficient matrix in dynamic equilibrium differential equations under vibration can be represented in the fully fifth-order polynomial equation, thus the natural frequency can be found. The natural frequency with/without the nonlinear c_1 term of displacement fields is investigated. It is a significant novelty with the consideration of the nonlinear c_1 term in the frequency computation.