Amplitude Of Mechanical Vibrations Research Articles

Control of Vibratory Feeder Device Mechanical Frequency Using the Modification of the Sinusoidal Supply Voltage Signal

In the industrial and sales processes, dosing systems of various constructions, whose operation is based on mechanical vibrations (vibratory feeders), are very often used. These systems face many problems, such as resonant frequency, flow instability of dosed product, instability of mechanical vibration amplitude, etc., because most of them are based on controlling the frequency of the electrical signal of the supply voltage. All these factors negatively affect the durability and reliability of the vibratory feeder systems. During this research, an automatic control system for vibratory feeder was created, whose control process is based on the modification of the sinusoidal signal (partially changing the signal area). In addition, such a way of controlling the vibratory feeder is not discussed in the literature. As the research conducted in this paper has shown, while using sinusoidal signal modification it was possible to achieve a stable flow rate of bulk production (the flow rate varied from 0 to 100 g/s when the frequency of mechanical vibrations changed from 1 to 50 Hz) and a stable amplitude of mechanical oscillations was achieved and equal to 1.5 mm. The control system is based on the microcontroller PIC24FV32KA302 for which the special software was developed. The thyristor BTA16 used for voltage modification of the sinusoidal signal made it possible to ensure the reliable control of the sinusoidal voltage modification process.

Effect of mechanical vibration on heat and mass transfer performance of pool boiling process in porous media: a literature review

Pool boiling in porous media has been applied in various thermal management systems by using latent heat and increasing the heat transfer area and thermal conduction path to improve the heat transfer performance. In mechanical equipment, vibration is an inevitable problem due to reasons such as engine operation and high-speed relative motion between transmission system components, which causes the system components to be affected by vibration forces or vibration accelerations. This study focuses on a review of published articles about the effects of mechanical vibration on the characteristics of boiling process in porous media by two aspects: heat transfer performance and bubble dynamics. Heat transfer coefficient (HTC) and critical heat flux are two main parameters used to measure the boiling heat transfer characteristics of porous media. For bubble dynamics investigations, properties such as migration, fragment, coalescence, departure diameter and frequency are the focus of research attention. Different mechanical vibration parameters, i.e., direction, frequency, and amplitude, will have different effects on the above characteristics. It is worth mentioning that the greatest influence occurs under resonance conditions, and this has been verified through experimental and simulation calculations. This review highlights the importance of considering mechanical vibrations in the design and optimization of porous media systems for efficient heat transfer applications. Further research is warranted to explore the detailed mechanisms and optimize the vibration parameters for enhanced heat transfer performance in thermal management systems using porous media.

Electricity Generation by Wind Using Resonance and Piezoelectric Effect

Faraday's law of Electromagnetic Induction is the working principle behind A.C.-D.C. generators, which contributes a major part of the generated electricity utilized today. However, the Photoelectric Effect used in Solar cells is also a useful source of renewable energy produced from the sun. In this research work, we have tried to generate electricity from the concept of Resonance and Piezoelectric Effect. To achieve the goal, we have used a thin strip of stretch-resistant material which naturally has the property of resisting the applied stretching force. The length of this stretch-resistant material will be set up so that the incoming airflow will make the thin strip vibrate at its resonant frequency. This will create high-amplitude mechanical vibrations on the thin strip. Now, these vibrations will be passed to the piezoelectric material. Piezoelectric materials have the property to exhibit the piezoelectric effect, which will convert the high amplitude mechanical vibrations passed by thin strips to the piezoelectric material into electrical discharge and hence, we generated electricity from wind using Piezoelectric Effect & Resonance. Due to less moving parts in our setup, it is theoretically more efficient in high wind conditions where a windmill usually fails to work. The only moving part is the thin strip which moves in a flapping motion hence, the generator is named a flapping generator. Even though the generated electricity is in a lesser amount, we can create an array of some such setups to increase the output electricity (as we do in solar energy generation) as per our requirement.

Multipoint monitoring of amplitude, frequency, and phase of vibrations using concatenated modal interferometers

Concatenated modal interferometers-based multipoint monitoring system for detection of amplitude, frequency, and phase of mechanical vibrations is proposed and demonstrated. The sensor probes are fabricated using identical photonic crystal fiber (PCF) sections and integrated along a single fiber channel to act as a compact and efficient sensing system. Each identical probe acts as a modal interferometer to generate a stable interference spectrum over the source spectrum. In the presence of an external dynamic field about each probe, the probes respond independently, producing a resultant signal superposition of each interferometer response signal. By analyzing the resultant signals using computational techniques, the vibration parameters applied to each interferometer are realized. The sensing system has an operation range of 1 Hz-1 kHz with a sensitivity of 51.5 pm/V. Such a sensing system would find wide applications at industrial, infrastructural, and medical fronts for monitoring various dynamic physical phenomena.

Microstructure and mechanical properties of AZ91D magnesium alloy by expendable pattern shell casting with different mechanical vibration amplitudes and pouring temperatures

To refine the microstructure and improve the mechanical properties of AZ91D alloy by expendable pattern shell casting (EPSC), the mechanical vibration method was applied in the solidification process of the alloy. The effects of amplitude and pouring temperature on microstructure and mechanical properties of AZ91D magnesium alloy were studied. The results indicated that the mechanical vibration remarkably improved the sizes, morphologies and distributions of the primary α-Mg phase and β-Mg17Al12 phase, and the densification and tensile properties of the AZ91D alloy. With an increase in amplitude, the microstructures were gradually refined, resulting in a continuous increase in mechanical properties of the AZ91D alloy. While, with the increase of pouring temperature, the microstructures were continuously coarsened, leading to an obvious decrease of the mechanical properties. The tensile strength and yield strength of the AZ91D alloy with a vibration amplitude of 1.0 mm and a pouring temperature of 730 °C were 60% and 38% higher than those of the alloy without vibration, respectively.

Piezoelectric energy enhancement strategy for active fuzzy harvester with time-varying and intermittent switching

This study aims to increase the amount of electrical energy harvested from a piezoelectric vibration energy harvester under unloaded and high-load resistance conditions. Although increased piezoelectric charge due to the synchronized switch harvesting on inductor (SSHI) strategy damps mechanical vibrations, the mechanical vibration amplitude of a mechanical element in a harvester is assumed to be constant for most discussions regarding the active harvester with SSHI strategy. However, this assumption is not valid under excessive switching actions, in which case the performance of the harvester deteriorates. This problem is known as the vibration suppression effect. To address this problem, in this study, two switching strategies for the charge inversion circuit—namely, switching considering vibration suppression-threshold (SCVS-t) and adaptive SCVS-t (ASCVS-t)—are proposed through intermittent switching actions. During the harvesting process, intermittent switching using these strategies is performed based on the output voltage threshold, thus maintaining high mechanical vibration amplitude and excellent harvesting performance by avoiding excess switching. The ASCVS-t adopts a tuning algorithm for the time-varying threshold and can achieve appropriate intermittent switching and effective harvesting under various vibration conditions without pre-tuning. Experimental comparisons with conventional strategies confirm that the proposed strategies achieve 2.9 times and 2.0 times greater harvested energy storages than a standard harvester and conventional switching strategy, respectively.

A Combination of a Vibrational Electromagnetic Energy Harvester and a Giant Magnetoimpedance (GMI) Sensor.

An energy harvesting device combined with a giant magnetoimpedance (GMI) sensor is presented to analyze low frequency vibrating systems. An electromagnetic harvester based on magnetic levitation is proposed for the electric power generation. The device is composed of two fixed permanent magnets at both ends of a cylindrical frame, a levitating magnet acting as inertial mass and a pick-up coil to collect the induced electromotive force. At the resonance frequency (10 Hz) a maximum electrical power of 1.4 mW at 0.5 g is generated. Moreover, an amorphous wire was employed as sensor nucleus for the design of a linear accelerometer prototype. The sensor is based on the GMI effect where the impedance changes occur as a consequence of the variations of the effective magnetic field due to an oscillating magnetic element. As a result of the magnet’s periodic motion, an amplitude modulated signal (AM) was obtained, its amplitude being proportional to mechanical vibration amplitude (or acceleration). The sensor’s response was examined for a simple ferrite magnet under vibration and compared with that obtained for the vibrational energy harvester. As a result of the small amplitudes of vibration, a linear sensor response was obtained that could be employed in the design of low cost and simple accelerometers.

Experimental set-up and the associated model for squeal analysis

Brake squeal is commonly defined at frequency upper than 1000 Hz and occurs if the system has a very high amplitude mechanical vibration with sound pressure level above 120 dB. Many studies are devoted to this problem and many of recent ones show that contact conditions and friction material behavior have a major influence on squeal occurrence. To investigate this aspect, an experimental set-up has been developed in this study. It is based on a simplified system in order to focus on the influence of the material in the one hand and surface conditions in the other hand. In this paper, the design of the pin-on-disc is described and an analytical model is also presented in order to understand the dynamic behavior of the system. Macroscopic aspects are investigated by varying the pin geometry. The results show clearly the influence of the variation of the contact length size on squeal occurrence. Comparison with the model shows good agreement and exhibit the necessity of considering an improved model of the friction material behavior. This study also gives information on the comprehension of squeal mechanisms.

Determination of Natural Frequencies of Pipes Using White Noise for Magnetostrictive Longitudinal Guided-Wave Nondestructive Testing

Magnetostrictive guided waves are widely used in nondestructive testing and structural health monitoring of pipes to ensure their integrity. These guided waves are mechanical waves, and if the natural frequencies of the pipe are used as excitation frequencies, the mechanical vibration amplitude can be enhanced, which will then improve the amplitude of the guided waves. Comparison of the various methods to determine the natural frequencies of pipes shows that the white noise signals remain relatively smooth in both time and frequency domains. White noise has a wide bandwidth and uniform energy distribution. It does not require high energy within a short time period, so it is easy to generate. In this article, white noise is used to determine the natural frequencies of pipes. Comparison of the white noise spectra produced by analog and digital circuits shows that the energy spectrum of white noise produced by the analog circuit is high and uniform, so the analog circuit is used as the white noise source and this noise is loaded onto a magnetostrictive sensor. The detected signal spectrum is then analyzed and the frequencies with high power density spectra are determined to be the natural frequencies. The natural frequencies of the pipeline detected using white noise are compared with the results of modal analysis. Simulation results and experimental results demonstrate that the use of white noise allows the natural frequencies of pipes to be determined quickly and accurately. These natural frequencies can be used in magnetostrictive guided-wave nondestructive testing.

Performance evaluation of a reinforced concrete building strengthened respectively by the infill wall, active and passive tuned mass damper under seismic load

One of the most commonly used control methods is a tuned mass damper (TMD), which is often employed to mitigate the amplitude of mechanical vibrations. To get a more effective response reduction of the structure, it is essential that the dynamics of the structure are modeled as accurately as possible. In this study, the seismic response of a reinforced concrete (RC) six-story building was analyzed with the combinations of masonry infill-wall, a passive and an active tuned mass damper (ATMD). The infill walls were placed along all frames without any space between column-wall and beam-wall connection. The TMD has no external source of energy, while the ATMD has an external energy source generated by the actuator which is driven by a linear quadratic regulator (LQR) controller. The dynamic response of the building was evaluated using the data from a real earthquake excitation of El Centro in 1940. The results highlight the inclusion of masonry infill wall in the seismic analysis is very important and has a substantial effect on the fundamental frequency and seismic characteristic of the structure. It also has a significant impact on the reduction of the inter-story drift and the seismic energy performance of the building.

Heat Transfer Performance of a Gasketed Plate Heat Exchanger using Nanofluid and Subject to Vibration as a Combined Augmentation Techniques

In the present study, an experimental investigation for heat transfer performance of γAl2O3-water nanofluid through a gasketed plate heat exchanger (GPHE) subjected to a low amplitude mechanical vibration was studied. γAl2O3-water nanofluid with four different volume fractions have been prepared and used as the hot working fluid. Corrugated plate heat exchanger (PHE) with six stainless steel plates; creating three cold municipal water channels and two hot nanofluid channels in counter flow pattern. GPHE is subjected to vibration by means of a grinding motor. Vibration frequencies is varied from 13.33 to 46.67 cps and vibrational dimensionless amplitude (A/De) is varied from 9.14x10-3 to 52.66x10-3. The experiments have been conducted in the Reynolds number ranging from 730 to 3400. The results revealed that as vibrational dimensionless amplitude (A/De) and nanofluid volume fractions increases the net heat transfer coefficient enhancement ratio increases. The net heat transfer coefficient increases as mechanical vibration amplitude decreases. The maximum net heat transfer coefficient enhancement ratio is 64%, which is achieved at 0.51 % volume fraction and oscillation Reynolds number of 211.34, which was occur just after the resonance condition. Moreover, a new empirical correlation is proposed to predict the GPHE Nusselt number Finally, pressure drop is measured and found that it is increased as nanofluid volume fraction increased.

Broadside Coupled Split Ring Resonator as a Sensitive Tunable Sensor for Efficient Detection of Mechanical Vibrations

This paper explores the possibility of the precise determination of mechanical vibrations using metamaterial split ring resonator (SRR) structure. The amplitude of the interacting electromagnetic wave in the range of GHz frequency is directly varied in accordance with the amplitude of mechanical vibration, using a Broadside Coupled SRR (BCSRR) acting as a vibration sensor. Dependence of the spacing between the two rings on the resonance frequency of the BCSRR is used for the detection of vibration and it is achieved by allowing the spacing to change in accordance with the amplitude of mechanical vibration. For the effective sensing of mechanical vibration, the electromagnetic wave frequency is chosen at the center of the linear portion of the rising or the falling slope of the resonant curve of the BCSRR. By properly choosing the parameters of the BCSRR along with the effective tuning of the operating frequency, it is possible to detect even very weak vibrations. The chances of various distortions in the detected vibration waveform in connection with selection of the operating frequency and intensity of vibrations are also analyzed. The qualitative formulation of the detection process along with its experimental verification is presented. This novel method may find applications in the detection of mechanical vibrations caused by various man made and natural sources and may find manifold possibilities in the field of communication and instrumentation.

Magnetic field and vibration effects on the onset of thermal convection in a grade fluid permeated anisotropic porous module

A study of thermo–vibrational convective instability in an infinitely extended flat anisotropic porous module, permeated by a second-grade fluid and heated from below is investigated depending on an externally imposed magnetic field. The Floquet hypothesis is applied to govern the onset condition within the background of linear stability theory by means of normal mode assumption. The present investigation is focused on the small amplitude mechanical vibration and the results are found by means of Mathieu’s functions and its stability charts. Special emphasis is given to examine the effects on anisotropies in permeability and thermal diffusivity of the porous module along the transverse direction. The emerging instabilities by means of the synchronous and subharmonic modes and the exact changeover point among them are examined for the different governing parameters. It is revealed that the externally imposed magnetic force has a stabilizing impact and hence a drop in flow moments.

Effect of stochastic resonance on proprioception and kinesthesia in anterior cruciate ligament reconstructed patients

Low amplitude mechanical noise vibration has been shown to improve somatosensory acuity in various clinical groups with comparable deficiencies through a phenomenon known as Stochastic Resonance (SR). This technology showed promising outcomes in improving somatosensory acuity in other clinical patients (e.g., Parkinson’s disease and osteoarthritis). Some degree of chronic somatosensory deficiency in the knee has been reported following anterior cruciate ligament (ACL) reconstruction surgery. In this study, the effect of the SR phenomenon on improving knee somatosensory acuity (proprioception and kinesthesia) in female ACL reconstructed (ACLR) participants (n = 19) was tested at three months post-surgery, and the results were compared to healthy controls (n = 28). Proprioception was quantified by the measure of joint position sense (JPS) and kinesthesia with the threshold to detection of passive movement (TDPM).The results based on the statistical analysis demonstrated an overall difference between the somatosensory acuity in the ACLR limb compared to healthy controls (p = 0.007). A larger TDPM was observed in the ACLR limb compared to the healthy controls (p = 0.002). However, the JPS between the ACLR and healthy limbs were not statistically significantly different (p = 0.365). SR significantly improved JPS (p = 0.006) while the effect was more pronounced in the ACLR cohort. The effect on the TDPM did not reach statistical significance (p = 0.681) in either group.In conclusion, deficient kinesthesia in the ACLR limb was observed at three months post-surgery. Also, the positive effects of SR on somatosensory acuity in the ACL reconstructed group warrant further investigation into the use of this phenomenon to improve proprioception in ACLR and healthy groups.

Mössbauer Method for Measuring Subangstrom Displacements of Thin Films

The first results of Mossbauer spectroscopy measurements of the distribution of the amplitude of mechanical vibrations of a 25-μm-thick stainless steel foil along its surface are presented. The gamma radiation of 57Co with a wavelength of 86 pm has been used for the measurements. Sample vibrations along the direction of gamma radiation propagation have been induced using a polymer piezoelectric transducer. At moderate applied voltages, the measured oscillation amplitude does not exceed 50 pm. The measurement accuracy of the vibration-amplitude distribution along the foil surface is 3–6 pm. This method is proposed to create standards of mechanical displacements that can be used to calibrate tunneling microscopes.

Effect of mechanical vibration on microstructure and properties of cast AZ91D alloy

Abstract The effects of mechanical vibration frequency and amplitude on solidification filling, microstructure and mechanical properties of cast AZ91D alloy were studied. The results show that when the mechanical vibration frequency of 100 Hz and the mechanical amplitude of 1.0 mm, the solidification filling capacity of AZ91D alloy is the best; the length, width and aspect ratio of the β-Mg17Al12 in AZ91D alloy decrease first and then increase with the increase of mechanical vibration frequency, and gradually decrease with the increase of mechanical amplitude, the minimum value was obtained when the mechanical vibration frequency of 100 Hz and the mechanical amplitude of 1.0 mm. At this time, the tensile strength and yield strength of cast AZ91D alloy are 143.4 MPa and 121.6 MPa, respectively, which are the suitable mechanical vibration parameters for cast AZ91D alloy.

Monitoring of the condition of turning machine bearing housing through vibrations

Mechanical vibration is a phenomenon that occurs very often in the process of metal cutting. It is one of many factors that have a significant impact on the quality of machining and thus prevent a rise in productivity. These vibrations are undesirable not only because they cause noise and dynamic stresses, which result in fatigue and failure of the machine, but also energy loss or performance reduction. An experimental analysis of mechanical vibrations in the machining process is important because vibrations may cause spindle damage, machine tool wear or workpiece wear and may be left with poor surface finish. Therefore, this material is devoted to the study of the impact of input cutting parameters—spindle speed and depth of cut on the formation and size of mechanical vibrations on lathe bearing housings. The measured experimental values of the acceleration amplitude of mechanical vibrations on bearing housings were compared with theoretical values.

Design of piezoelectric piston-like piezoelectric transducers based on a phononic crystal

ABSTRACTMany clinical surveys have evaluated the use of ultrasound in physiotherapy treatments, the question of its effectiveness still being under discussion possibly because of the randomized energy density applied, which depends on the acoustic pressure beam of the transducers. In this work, a phononic crystal made of holes in solid materials is the basis for the design of a transducer with a piston-like vibration pattern where the radial modes are stopped, thus favoring the thickness vibration and resulting in a better mechanical vibration amplitude and acoustic efficiency. Finite element simulations have been made of the standard transducer and the proposed design; then demonstrator devices have been manufactured and tested so experimental results could be compared to the calculated ones. The transducers with this phononic structure show an efficient piston-like emission. The electrical impedance, the emitting surface vibration pattern and the acoustic diffraction field have been calculated and experimentally measured.

The Use of Phononic Crystals to Design Piezoelectric Power Transducers.

It was recently proposed that the lateral resonances around the working resonance band of ultrasonic piezoelectric sandwich transducers can be stopped by a periodic array of circular holes drilled along the main propagation direction (a phononic crystal). In this work, the performance of different transducer designs made with this procedure is tested using laser vibrometry, electric impedance tests and finite element models (FEM). It is shown that in terms of mechanical vibration amplitude and acoustic efficiency, the best design for physiotherapy applications is when both, the piezoceramic and an aluminum capsule are phononic structures. The procedure described here can be applied to the design of power ultrasonic devices, physiotherapy transducers and other external medical power ultrasound applications where piston-like vibration in a narrow band is required.

Piezomodulation of Connection Conductance TlInTe<sub>2</sub>

This paper discusses the development method of strain sensors based on acicular single crystal compound TlInTe2 is grown by Bridgman-Stockbarger technique. Creating mechanically reliable ohmic contacts on said obtained single crystals was carried out directly by spot welding wires corresponding to the ends of the capacitor discharge heated in a stream of inert gas from the single crystal TlInTe2. This method of creating contacts proved effective and reliable. Sensors made by this manner stuck to the calibrated beams of steel thickness of 1 mm, a length of 30 mm and a corresponding optimal regime got sensors with a maximum piezo-sensitivity. It was found that if enshrined at one end of a thin steel sheet with glued crystals TlInTe2 initiate periodic mechanical vibrations to the same frequency, occurs conductivity modulation. The effect of piezo-modulation conductance depending on the degree of deformation, illumination in interval of deformation and lux illumination in room temperature were studied. The study showed that the more mechanical deformation and illumination are, the more modulation amplitude is. We studied the modulation of the conductivity of crystals during mechanical deformation values of 8, 14, 19, 23 and 27 × 10-5and illuminance 1000, 2750, 4750 and 6500 suites. Investigations the level piezo-signal depending on the amplitude of mechanical vibrations at frequency of 85 Hz, it is found that with increasing magnitude of the mechanical deformation of 7 × 10-5 and 26 × 10-5 amplitude increases six times. It is shown that the piezoresistive effect is clearly manifested in dynamic mode. Additional conductivity occurs during mechanical deformation. When the illuminated samples piezoconductivity magnitude increases linearly.