Resonance Frequency Of Oscillations Research Articles

Research of anti­resonance three­mass vibratory machine with a vibration exciter in the form of a passive auto­balancer

A three-mass anti-resonance vibratory machine with a vibration exciter in the form of a passive auto-balancer has been analytically synthesized. In the vibratory machine, platforms 1 and 2 are visco-elastically attached to platform 3. Platform 3 is visco-elastically attached to the base. The motion of loads relative to the auto-balancer housing is hindered by the forces of viscous resistance. A theoretical study has shown that the vibratory machine possesses three resonance frequencies and three corresponding forms of platforms' oscillations. Values for the parameters of supports that ensure the existence of an anti-resonance form of motion have been analytically selected. Under an anti-resonance form, platform 3 is almost non-oscillating while platforms 1 and 2 oscillate in the opposite phase. In the vibratory machine, platform 1 can be active (working), platform 2 will then be reactive (a dynamic vibration damper), and vice versa. At the same time, the vibratory machine will operate when mounting a vibration exciter both on platform 1 and platform 2. An anti-resonance form would occur when the loads get stuck in the vicinity of the second resonance frequency of the platforms' oscillations. Given the specific parameters of the vibratory machine, numerical methods were used to investigate its dynamic characteristics. Numerical calculations have shown the following for the case of small internal and external resistance forces in the vibratory machine: ‒ theoretically, there are seven possible modes of load jam; ‒ the second (anti-resonance) form of platform oscillations is theoretically implemented at load jamming modes 3 and 4; ‒ jamming mode 3 is locally asymptotically stable while load jamming mode 4 is unstable; ‒ for the loads to get stuck in the vicinity of the second resonance frequency, one needs to provide the vibratory machine with the initial conditions close to the jamming mode 3, or smoothly accelerate the rotor to the working frequency; ‒ the dynamic characteristics of the vibratory machine can be controlled in a wide range by changing both the rotor speed and the external and internal forces of viscous resistance. The results reported here are applicable for the design of anti-resonance three-mass vibratory machines for general purposes

Searching for the two­frequency motion modes of a three­mass vibratory machine with a vibration exciter in the form of a passive auto­balancer

The dynamics of a three-mass vibratory machine with the rectilinear translational motion of platforms and a vibration exciter in the form of a ball, roller, or pendulum auto-balancer have been analytically investigated. The existence of steady state motion modes of a vibratory machine that are close to two-frequency regimes has been established. At these motions, the loads in an auto-balancer create constant imbalance, cannot catch up with the rotor, and get stuck at a certain frequency. These loads work as the first vibration exciter, thereby exciting vibrations in resonance with the frequency at which loads get stuck. The second vibration exciter is formed by an unbalanced mass on the body of the auto-balancer. The mass rotates at the rotor's rotation frequency and excites faster vibrations with this frequency. The auto-balancer excites almost ideal two-frequency vibrations. Deviations from the two-frequency law are proportional to the ratio of the mass of the loads to the mass of the platform, which hosts the auto-balancer, and do not exceed 5 %. A three-mass vibratory machine has three resonant (natural) oscillation frequencies, q1, q2, q3 (q1).

Influence of the pump scheme on the output power and the intensity noise of a single-frequency continuous-wave laser.

The influence of the pump scheme on the intensity noise of the single-frequency continuous-wave (CW) laser is investigated in this paper, which is implemented in a single-frequency CW Nd:YVO4 1064 nm laser by comparing the traditional 808 nm pumping scheme (TPS) to the direct 888 nm pumping scheme (DPS). Under the conditions that the lasers with TPS and DPS have the same cavity structure and the cavity mirrors, as well as the same operation state including the thermal lens of the laser crystals and the mode-matching between the pump laser mode and the laser cavity mode at the laser crystals, the output power of the laser with DPS is up-to 32.0 W, which is far higher than that of 21.1 W for the laser with TPS. However, the intensity noise of the DPS laser including resonant relaxation oscillation (RRO) frequency of 809 kHz, RRO peak amplitude of 31.6 dB/Hz above the shot noise level (SNL) and the SNL cutoff frequency of 4.2 MHz, respectively, is also higher than that of 606 kHz, 20.4 dB/Hz and 2.4 MHz for the TPS laser. After further analyses, we find that the laser crystal with high doping concentration and long optical length is employed for DPS laser in order to improve the pump laser absorption efficiency, which can simultaneously increase the dipole coupling between the active atoms and the laser cavity, and then results in a high RRO frequency with a large amplitude peak as well as a high SNL cutoff frequency of the laser.

Detection Principles of Temperature Compensated Oscillators with Reactance Influence on Piezoelectric Resonator.

This review presents various ways of detection of different physical quantities based on the frequency change of oscillators using piezoelectric crystals. These are influenced by the reactance changes modifying their electrical characteristics. Reactance in series, in parallel, or a combination of reactances can impact the electrical crystal substitute model by influencing its resonant oscillation frequency. In this way, various physical quantities near resonance can be detected with great sensitivity through a small change of capacitance or inductance. A piezoelectric crystal impedance circle and the mode of frequency changing around the resonant frequency change are shown. This review also presents the influence of reactance on the piezoelectric crystal, the way in which the capacitance lost among the crystal’s electrodes is compensated, and how the mode of oscillators’ output frequency is converted to lower frequency range (1–100 kHz). Finally, the review also explains the temperature–frequency compensation of the crystals’ characteristics in oscillators that use temperature–frequency pair of crystals and the procedure of the compensation of crystals own temperature characteristics based on the method switching between the active and reference reactance. For the latter, the experimental results of the oscillator’s output frequency stability (fout = ±0.002 ppm) at dynamical change of environment temperature (0–50 °C) are shown.

Analysis of Viscoelastic Parameters of Fluids by Low-Frequency Piezoelastography.

Theoretical and experimental analysis of viscoelastic properties of fluids at low oscillating shear stresses was performed. Mathematic approach for calculating the complex coefficient of viscosity on the basis of experimental data on the amplitude-phase characteristics measured by the method of low-frequency piezoelastography was developed. The dependencies of the amplitude and phase shift of the signal recorded by a piezoelectric detector of a ARP-01M Mednord piezoelectric thromboelastograph on the frequency of forced oscillations of a resonator needle in air, water, and glycerin at fixed temperature of 37°C were studied. It was found that with increasing fluid viscosity, the resonance frequency of oscillations decreases in comparison with the frequency of oscillations in air.

Piezoelectric displacement mapping of compliant surfaces by constant-excitation frequency-modulation piezoresponse force microscopy

A simple experimental method for piezoresponse force microscopy (PFM) measurements for reliable evaluation of piezoelectric surface displacements even on compliant surfaces is proposed based on atomic force microscopy (AFM) operated in frequency-modulation (FM) dynamic mode with constant excitation (CE), by using non-contact mode cantilevers. Surface displacement by piezoelectric effect after application of an electric potential to the conductive AFM probe translates into a likewise variation of the probe oscillation amplitude, while the related electrostatic forces mainly affect the oscillator resonant frequency, and cantilever bending is limited due to their high stiffness. Our non-contact CE-FM-PFM method is shown to reduce electrostatic force contributions as compared to contact-PFM modes. Converse piezoelectric effect mapping is demonstrated on poly(vinylidenefluoride) nanofibers obtained by electrospinning.

РОЗРОБКА П’ЄЗОДВИГУНА ДЛЯ БІОПРОТЕЗА

Currently, worldwide, the development and research of piezoelectric motors is a very relevant and important problem that attracts a large number of researchers. The interest in this problem is due to the prospect of creating small piezoelectric motors. This allows to obtain unique devices in which electric vibrations turn into rotary movement, in addition, the rotating moment that develops on the shaft of such an engine is so large that eliminates the need for a mechanical gearbox to increase the torque. The world leaders in the production of piezoelectric motors are the following companies: Physik Instrumente (PI), New Scale Technologies and others. The main purpose of this paper is to study and improve piezomotors, for the use in bioprostheses as actuators. Piezomotors are the main element of many microelectromechanical systems that are used in military sphere, in particular in robotics, and also in scientific research instruments. But all these piezoelectric motors have a number of disadvantages, the main of which are: high control voltage, small range of movement of the moving parts, the complexity of manufacturing structures, and large dimensions that reduce their application in various fields. Based on the drawbacks of these constructions, we have proposed and developed our own piezoelectric motor design, and simulated one biomorphic plate in the COMSOL Multiphysics program package. With the COMSOL Multiphysics program, forms of mechanical oscillations, deformations, resonance frequency of bending oscillations, and maximum amplitude of oscillations are determined. Also, in this paper, the coefficient of stiffness of bimorph piezoelements is given, thus, a qualitative mathematical model can significantly reduce the time and costs for the development of bimorph piezoelements. The use of bimorph piezoelectric cells in the developed piezoelectric motor increases the ampli-tude of oscillations, and reduces the amplitude of the control signal. The obtained data can be used in the design of devices where piezoceramic actuators are used.

The Influences of Organic Matter Concentrations in Juices for Pathogen Detection Using Phage-Based Biosensors

Fruit and vegetables are playing an important role of today’s healthy diet. Juices are the liquid extracts from fruit and vegetables, which contain lots of organic matters, such as vitamins, minerals and plant chemicals (phytonutrients). Commercial bottle juices usually contain different percentages of real juices in their juice products. Therefore, the amount of organic matter content in juices are different in various brands of juices. The foodborne pathogen outbreaks through the consumption of fruit or vegetable juices continue to be reported (CDC, 2016). It indicates that pathogens like Salmonella can be packaged with juices even with current manufacture microbial-inactivation process. According to several studies, the acidity in tomatoes juice and the phyto-chemicals (like chlorophyll) from damage leaves in leafy greens samples can affect the sensitivity of pathogen detection in juices. For example, chlorophyll is one of the substances in leafy green juice that inhibits PCR reaction for pathogen detection. This made the pathogen detection in some juices a difficult task to achieve. The phage magnetoelastic (ME) biosensors are wireless sensors, whose resonance oscillation and resonance frequency are actuated and detected through magnetic fields. These biosensors have been shown to be highly sensitive and specific in pathogen detection including Salmonella on various food surfaces or liquids (Li et al., 2010). Therefore, in this study, different concentrations of juices from tomatoes and spinach with artificially spiked Salmonella (at the concentration of 104 cfu/ml) was tested by ME biosensors. The influence of pathogen detection capability was then studied by comparing the bacterial capture rates on biosensors. In tomato juice, the results showed that the capture rate of Salmonella can be reached up to 90.68% by using 100 ME biosensors in a tube rocking experiment with 10% tomato juice content. In spinach juice, the capture rate of Salmonella showed similar results as 90.68% in the same 10% juice concentration. However, when the juice concentration of spinach went up to 15% and 20%, the bacterial capture rate slightly decreased. The Salmonella capture rate were shown as 89.82% and 89.065, respectively. The decreasing of capture rate was obvious by using 50 ME sensors for the 15% and 20% spinach juices. In conclusion, by using 100 phage ME biosensors, the detection platform can detect as high as 89% Salmonella in high juice concentration (15 % and 20%) of both tomato and spinach juice samples. While in the moderate juice concentration zone (5-10%), the ME biosensors show very promising results of detecting 90% Salmonella in both juices.

A dynamic solution for predicting resonant frequency of piston mode fluid oscillation in moonpools/narrow gaps

The objective of this study is to develop a simple tool for predicting the resonant frequency of the piston mode wave oscillation in a moonpool or a narrow gap between twin floating barges. Based on the dynamic analysis and the domain-decomposition, a linear harmonic oscillator model for the fluid oscillation in a confined space is formulated, which immediately leads to an explicit dynamic solution for the resonant frequency. In the model, it is assumed that the water depth is equal to or greater than a critical value dependent on the ratio of the draft to the breadth of the floating body. The predicted resonant frequencies are compared with the numerical results of the linear potential model and the viscous fluid model, the semi-analytical potential solutions and the experimental measurements. Good agreements are observed for a wide range of geometric parameters of the moonpool and the narrow gap of either sharp or round edge shapes. The present dynamic method is also applied to predict the resonant frequency of the piston mode oscillation in the gap between a floating body and a vertical wall with a reasonable success.

DEFLECTIONS AND FREQUENCY ANALYSIS IN THE MILLING OF THIN-WALLED PARTS WITH VARIABLE LOW STIFFNESS

The disadvantage of the geometry of thin-walled parts, in terms of processing, is the low ability to resist static and dynamic loads. It is caused by the elastic deformation of elements with a low stiffness. Modelling approaches for the evaluation of deflections during machining are presented. Mathematical models of deflections, cutting forces and harmonic response are proposed. The processes of material removal and deflection of a thin-walled sample at the critical points are modelled. A frequency analysis was performed, consisting of a modal analysis of natural frequencies and a harmonic response analysis. As a result, a graph of the deflections amplitude from the frequency of driven harmonic oscillations is generated. The analysis of the obtained values was performed. As a result, the resonance frequency and maximum amplitude of oscillations for the operating parameters are determined.

Motion equations of the single­mass vibratory machine with a rotary­oscillatory motion of the platform and a vibration exciter in the form of a passive auto­balancer

This paper describes a mechanical model of the single-mass vibratory machine with a rotary-oscillatory motion of the platform and a vibration exciter in the form of a passive auto-balancer. The platform can oscillate around a fixed axis. The platform holds a multi-ball, a multi-roller, or a multi-pendulum auto-balancer. The auto-balancer's axis of rotation is parallel to the turning axis of the platform. The auto-balancer rotates relative to the platform at a constant angular velocity. The auto-balancer's casing hosts an unbalanced mass in order to excite rapid oscillations of the platform at rotation speed of the auto-balancer. It was assumed that the balls or rollers roll over rolling tracks inside the auto-balancer's casing without detachment or slip. The relative motion of loads is impeded by the Newtonian forces of viscous resistance. Under a normally operating auto-balancer, the loads (pendulums, balls, rollers) cannot catch up with the casing and get stuck at the resonance frequency of the platform's oscillations. This induces the slow resonant oscillations of the platform. Thus, the auto-balancer is applied to excite the dual-frequency vibrations. Employing the Lagrangian equations of the second kind, we have derived differential motion equations of the vibratory machine. It was established that for the case of a ball-type and a roller-type auto-balancer the differential motion equations of the vibratory machine are similar (with accuracy to signs) and for the case of a pendulum-type vibratory machine, they differ in their form. Differential equations of the vibratory machine motion are recorded for the case of identical loads. The models constructed are applicable both in order to study the dynamics of the respective vibratory machines analytically and in order to perform computational experiments. In analytical research, the models are designed to search for the steady-state motion modes of the vibratory machine, to determine the condition for their existence and stability

Field Characteristics of Spin-Torque Diode Sensitivity in the Presence of a Bias Current

The use of the spin-torque diode effect, which is generated upon the current-induced transfer of spin angular momentum in magnetic tunnel junctions, opens the prospect of considerably improving microwave sensitivity in the gigahertz frequency band over that of semiconductor Schottky diodes. In this work, the spin-diode effect of microwave signal rectification in a magnetic tunnel junction upon the resonant excitation of spin waves in the free magnetic layer as a result of the current-induced spin-transfer torque effect is analyzed theoretically. Frequency characteristics of the resonant response of a spin-torque diode to a microwave signal are calculated in the linear macrospin approximation as functions of the direction and value of the applied magnetic field and bias current. It is shown that with zero bias current, the maximum rectified voltage across a junction is obtained in the geometry of mutually perpendicular magnetizations of magnetic layers; as the resonant frequency of oscillations in a magnetic field increases, this voltage drops at the retained equilibrium orientation of spins in the layers. After the bias current is switched on, the resonance amplitude of forced oscillations of the free layer spins upon microwave excitation grows sharply at the critical point of the spin-torque diode’s loss of equilibrium state stability. The linewidth at this point is limited only by nonlinear effects. Improving spin-torque diode sensitivity is important for its use in microwave holographic vision systems.

Quantum control of phase fluctuations in semiconductor lasers

Few laser systems allow access to the light-emitter interaction as versatile and direct as that afforded by semiconductor lasers. Such a level of access can be exploited for the control of the coherence and dynamic properties of the laser. Here, we demonstrate, theoretically and experimentally, the reduction of the quantum phase noise of a semiconductor laser through the direct control of the spontaneous emission into the laser mode, exercised via the precise and deterministic manipulation of the optical mode's spatial field distribution. Central to the approach is the recognition of the intimate interplay between spontaneous emission and optical loss. A method of leveraging and "walking" this fine balance to its limit is described. As a result, some two orders of magnitude reduction in quantum noise over the state of the art in semiconductor lasers, corresponding to a minimum linewidth of [Formula: see text], is demonstrated. Further implications, including an additional order-of-magnitude enhancement in effective coherence by way of control of the relaxation oscillation resonance frequency and enhancement of the intrinsic immunity to optical feedback, highlight the potential of the proposed concept for next-generation, integrated coherent systems.

Experimental study into rotational-oscillatory vibrations of a vibration machine platform excited by the ball auto-balancer

We have experimentally investigated the rotational-oscillatory vibrations of vibratory machine platform excited by the ball auto-balancer. The law of change in the vibration accelerations at a platform was studied using the accelerometer sensors, a board of the analog-to-digital converter with an USB interface and a PC. The amplitude of rapid and slow vibratory displacements of the platform was investigated employing a laser beam. It was established that the resonance frequency (frequency of natural oscillations) of the platform is: 62.006 rad/s for the platform with a mass of 2,000 gm; 58.644 rad/s ‒ of 2,180 gm; 55.755 rad/s ‒ of 2,360 gm. An error in determining the frequencies does not exceed 0.2 %. The ball auto-balancer excites almost perfect dual-frequency vibrations of a vibratory machine platform. Slow frequency corresponds to the rotational speed of the center of balls around the longitudinal axis of the shaft, while the fast one ‒ to the shaft rotation speed, with the unbalanced mass attached to it. A dual-frequency mode occurs in a wide range of change in the parameters and it is possible to alter its basic characteristics by changing the mass of balls and the unbalanced mass, the angular velocity of shaft rotation. It has been established experimentally that the balls get stuck at a frequency that is approximately 1 % lower than the resonance frequency of platform oscillations. Assuming the platform executes the dual frequency oscillations, we employed the software package for statistical analysis Statistica to select coefficients for the respective law. It was found that: – the process for determining the magnitudes of coefficients is steady (robust); coefficients almost do no change when altering the time interval for measuring the law of a platform motion; – the amplitude of accelerations due to the low oscillations is directly proportional to the total mass of the balls and the square of the frequency at which balls get stuck; – the amplitude of rapid oscillations is directly proportional to the unbalanced mass at the auto-balancer's casing and to the square of angular velocity of shaft rotation. The discrepancy between the law of motion, obtained experimentally, and the law, obtained using the methods of statistical analysis, is less than 3 %. The results obtained add relevance to both the analytical studies into dynamics of the examined vibratory machine and to the creation of the prototype a vibratory machine.

Energy harvesting from quasi-static deformations via bilaterally constrained strips

Piezoelectric energy harvesting from ambient vibrations is well studied, but harvesting from quasi-static responses is not yet fully explored. The lack of attention is because quasi-static actions are much slower than the resonance frequency of piezoelectric oscillators to achieve optimal outputs; however, they can be a common mechanical energy resource: from large civil structure deformations to biomechanical motions. The recent advances in bio-micro-electro-mechanical systems and wireless sensor technologies are motivating the study of piezoelectric energy harvesting from quasi-static conditions for low-power budget devices. This article presents a new approach of using quasi-static deformations to generate electrical power through an axially compressed bilaterally constrained strip with an attached piezoelectric layer. A theoretical model was developed to predict the strain distribution of the strip’s buckled configuration for calculating the electrical energy generation. Results from an experimental investigation and finite element simulations are in good agreement with the theoretical study. Test results from a prototyped device showed that a peak output power of 1.33 μW/cm2 was generated, which can adequately provide power supply for low-power budget devices. And a parametric study was also conducted to provide design guidance on selecting the dimensions of a device based on the external embedding structure.

COMPUTER MODELING AND ANALYSIS OF VIBRATIONS IN ANNULAR CONCENTRATOR OF ULTRASONIC SYSTEM

The paper provides substantiation on application of elastic annular concentrators of ultrasonic systems which allows to increase an intensity of tool vibrations. It has been shown that elastic elements are used as resonators and tools in a number of ultrasonic technological systems. However an application of the elastic elements as concentrators of ultrasonic vibrations has been insufficiently studied and requires research and development of recommendations for usage. For this purpose theoretical studies have been carried out and they have helped to perform modal and harmonic analysis of several variants for a computer model of a ring with outer diameter D = 50 mm. Models of rings with various hole sizes from 20 to 40 mm have been analyzed while changing hole axis position relative to ring axis. The paper shows modes of ring flexural vibrations which can be either flat or three-dimensional depending on frequency of forced oscillations. It has been pointed out that an increase in a ring internal diameter is accompanied by higher amplitude of bending oscillations in the thinnest ring section. The same effect is achieved by increasing eccentricity of a hole axis. The paper contains recommendations for determination of rational geometric parameters which allows to increase an oscillation amplitude gain ratio and it is determined as ratio of ring section thickness. It has been established that decrease in section thickness is accompanied by higher number of frequencies for ring resonance oscillations. So, if a concentric ring and a ring with small hole diameter have only one resonance frequency, then thin-walled rings with a variable cross-section have not less than three natural resonance frequencies of oscillations that makes it possible to increase a range of vibration frequencies and technological capabilities of the ultrasonic system. It has been also found that an intensity in fluctuations of the ultrasonic system is increased even more if at the same time a cross-section of a ring with variable stiffness is decreased as along thickness so across the width.

Vibration Mode and Influence Analysis of Rotary Shaft for 200kW Tubular Pump

The pump rotary shaft’s vibration will influence pump unit’s work situation. The rotary shaft of 2200kW tubular pump is proceeded 3D FEM’s modeling analysis in this paper. Some benefit results are obtained by researching the vibration mode, resonance oscillation frequency and deformation. It will help design and apply the tubular pump, own the practical value.

Interaction acoustic waves with a layered structure containing layer of bubbly liquid

The results of a theoretical study of the effect of a bubble layer on the propagation of acoustic waves through a thin three-layered barrier at various angles of incidence are presented. The barrier consists of a layer of gel with polydisperse air bubbles bounded by layers of polycarbonate. It is shown that the presence of polydisperse air bubbles in the gel layer significantly changes the transmission and reflection of the acoustic signal when it interacts with such an obstacle for frequencies close to the resonant frequency of natural oscillations of the bubbles. The frequency range is identified where the angle of incidence has little effect on the reflection and transmission coefficients of acoustic waves.

Attenuation of the Acoustic Signal Propagating Through a Bubbly Liquid Layer

The acoustic signal dynamics in a five-layer medium containing two liquid layers with polydisperse gas bubbles has been investigated. Calculations have been made for the interaction between the pulse perturbation of smallamplitude pressure and a multilayer sample containing two layers of industrial gel with polydisperse air bubbles. It has been shown that a small content of bubbles (about 0.1 vol. %) in a thin gel layer decreases tenfold or more the amplitude of acoustic waves with frequencies close to the resonance frequency of natural oscillations of bubbles. There are frequency ranges thereby where the influence of the bubbly layer is insignificant.

Stationary bound-state massive scalar field configurations supported by spherically symmetric compact reflecting stars

It has recently been demonstrated that asymptotically flat neutral reflecting stars are characterized by an intriguing no-hair property. In particular, it has been proved that these horizonless compact objects cannot support spatially regular static matter configurations made of scalar (spin-0) fields, vector (spin-1) fields and tensor (spin-2) fields. In the present paper we shall explicitly prove that spherically symmetric compact reflecting stars can support stationary (rather than static) bound-state massive scalar fields in their exterior spacetime regions. To this end, we solve analytically the Klein–Gordon wave equation for a linearized scalar field of mass mu and proper frequency omega in the curved background of a spherically symmetric compact reflecting star of mass M and radius R_{text {s}}. It is proved that the regime of existence of these stationary composed star–field configurations is characterized by the simple inequalities 1-2M/R_{text {s}}<(omega /mu )^2<1. Interestingly, in the regime M/R_{text {s}}ll 1 of weakly self-gravitating stars we derive a remarkably compact analytical equation for the discrete spectrum {omega (M,R_{text {s}},mu )}^{n=infty }_{n=1} of resonant oscillation frequencies which characterize the stationary composed compact-reflecting-star–linearized-massive-scalar-field configurations. Finally, we verify the accuracy of the analytically derived resonance formula of the composed star–field configurations with direct numerical computations.