Electromagnetic Vibrator Research Articles

An electromagnetic vibrator fixed on a screen initiates gas breakdown in the subcritical field of a microwave beam

Results of experimental investigation of the electric breakdown of air in a quasi-optical microwave beam with a deep subcritical field level are presented. The breakdown was initiated by a linear or Γ-shaped electromagnetic (EM) vibrator fixed on a screen. It is established that a vibrator positioned above the screen at a distance shorter than quarter-wavelength of the EM field can induce the electric breakdown of air at high pressures and relatively low field level. Using a Γ-shaped EM vibrator, it is possible to preset the spatial region of breakdown.

Commutation technique in the supply of electromagnetic actuators

This study presents some specific problems concerning the DC–AC commutation of the power converters used in frequency controlled electromagnetic actuators. Starting from the initial conditions imposed for a low-cost simple inverter used for driving an electromagnetic vibrator, two commutation possibilities are analysed (unmodulated voltages and simple modulated voltages). The harmonic analysis performed in this study, permitted the analytic determination of the load current distortion coefficient against the control angle in the case of simple modulated voltage. The energetic performances (the real power and the power factor) of the system were evaluated through the power factor, determined analytically as a function of the operating frequency and the control angle α. The influence of the control angle on the current distortion factor has been highlighted experimentally using a programmable source, which allowed the synthesis of different waveforms at different frequencies. The novelty of this study consists in the analysis of the influence of the control variable angle α on energy parameters of electromagnetic vibrators, which allows a lower distortion factor and an appropriate power factor, both at a lower cost and lower commutation losses compared with pulse width modulation converters. Section 1 presents the technologies using commutation techniques analysed in Sections 2 and 3; Section 4 represents an analysis of the energetic performances, whereas in Section 5 experimental results for a vibro-compaction equipment are presented.

A Reference Infrasound Source with Low Distortion Based on Laser Pistonphone Technology

For safety protection from infrasound and its metrology, a reference infrasound source was developed on the basis of the laser pistonphone technique. The electromagnetic vibrator was made based on the technology of air bearings and a displacement feedback system. The air bearings reduce the damping of the vibrator, and the displacement feedback system could effectively control the distortion of the pistonphone. Through the displacement of the piston measured by a laser interferometer, the sound pressure could be calculated. In the meantime, the sound pressure was measured by a LS1P microphone with the reciprocity calibration results. The test results show that the difference between the measured pressure and the calculated one is no more than 0.01 dB from 5 to 20 Hz and the total distortion of the sound pressure at 124.0 dB is less than 0.7 % from 1 to 20 Hz.

Induced field of an electromagnetic vibrator above a conducting screen placed in a microwave beam

The induced field of a cylindrical electromagnetic vibrator with spherically rounded ends is calculated. The vibrator is above a flat screen placed in a linearly polarized quasi-optical microwave beam. The plane of the screen is perpendicular to the Poynting vector of the radiation. The axis of the vibrator is aligned with the vector of the exciting field electrical component. In calculation, the length of the vibrator and the vibrator-screen distance were varied, while its diameter and the initial field were kept constant. It is found that the induced field of the vibrator with a length close to the half-wavelength of the field is maximal at the ends of the vibrator and the field strength resonantly depends on the length of the vibrator. The shortening of the “half-wavelength” vibrator that provides a maximal induced field is determined. The result of numerical simulation is to an extent intriguing. It is revealed that the induced field of a resonance half-wavelength vibrator rises considerably when the vibrator-screen distance becomes shorter than the quarter-wavelength of the field. The Q factor of an equivalent electromagnetic oscillating circuit characterizing the vibrator also grows, and the induced field more and more concentrates between the screen and the surface of the vibrator’s ends facing the screen. Full-scale experiments qualitatively support theoretical predictions. The results allow researchers to considerably extend the application area of vibrators as initiators of breakdown in high-pressure gases to ignite microwave discharges in quasi-optical beams with a low initial field.

IMPROVEMENT IN MICRO HARDNESS OF M.S. (C-40) BY UTILIZING VIBRATORY TECHNIQUE IN ORDINARY BALL BURNISHING PROCESS

Surface characteristic of material plays vital role in performance of a component such as load bearing capacity, fatigue strength, resistance to corrosion, friction, wear, etc. Some of parameters which influence the above performance characteristics are geometric features of the surface, its hardness, and degree of cold work and nature of residual stress induced. Burnishing forms an important member in the family of these post machining processes. The deforming action of the ball which governs the micro hardness is strongly governed by the trajectory movement of tool. The trajectory movement of tool can be adjusted in proper range by selecting proper combinations of speed, feed, vibration frequency and amplitude. Addition in vibratory technique, the investigation of electromagnetic vibrator using in ordinary ball burnishing process perform reliable and effective surface enhancement. The plastic deformation on the part surface can easily achieved by applying considerably lower pressure as compared to other conventional techniques. With the use of vibratory technique on lathe machine, further improvement is possible in micro hardness of work piece.

The Working Principle of Multi-Layer Electromagnetic Screens and the Dynamics Analysis

Introducing the structures of Multi-layer electromagnetic screens and elaborating the working principle of Multi-layer electromagnetic screens, we have carried on the computation to the related parameter in the foundation of dynamics analysis. The designing adopts the vibration modes and principles of the transmission, takes electro-magnetic vibrator as vibration source, encourages to drive four vibration shafts through the vibration transmission system at the same time, and eventually the materials are passed then sifted out the screen mesh. The products have small space occupation, the high vibration intensity, large capacity, easy to operate, stable performance, high efficiency, low power consumption, small dynamic and self cleaning sieves, etc.

RESEARCH ON TRANSFERING THE DYNAMIC PROCESS BY THE SPRING

The article describes the particulars of transferring the dynamic process applying the spring and explains the possibilities of diagnostics for support bearings insulated from the external body using resilient elements. The carried out research has revealed methodology for investigation and suggested a suitable research stand. The input signal of impulse type was submitted to the system to observe free oscillations in the stand. Also, the system was stimulated employing an electromagnetic vibrator to research the transfer function of the spring. Finally, using output and input signals at the ends of the spring, the transfer function was derived.

영상처리식 온라인 품위판정을 위한 현미의 정렬공급장치

An automatic echelon feeder of brown rice was presented for quality inspection system using color image processing. A echelon feeder was developed with vibratory feeder and cylindrical indent singulator having oblique light. The vibratory feeder consisted of a hopper, electromagnetic vibrator and multichannel grooves and supply the grain sample to the singulator. The feeding performance such as feed rate, blocking frequency of the channel was dependent on the size of groove and vibration pattern. A cylindrical indent singulator consisted of a rotating cylinder, prisms and a tungsten-halogen light source. It delivered grain kernels under the camera in a echelon form and illuminate the kernels with oblique ray and ambient light. The size of the indents installed on the surface of the rotating cylinder was determined by the dimensions of the paddy and a small triangular prism was placed in each indent to apply <TEX>$ 20^{\circ}$</TEX> oblique light to the grain kernel.

Electrical discharge excited by the deeply undercritical field of a microwave beam in a high-speed jet of air and air-propane mixture

An electrical gas discharge initiated by a tubular linear electromagnetic vibrator is studied. The discharge is excited by the deeply undercritical linearly polarized field of a quasi-optical microwave beam. Experiments are conducted at a flow velocity of several hundreds of meters per second. The discharge region is photographed, and the stagnation temperature of the flow in the wake of the discharge is measured. It is shown that a deeply undercritical microwave discharge may arise in air even at such high flow velocities. Moreover, it is found that the discharge ignites and stabilizes the discharge region in a “lean” air-propane mixture. In such an experimental design, propane completely burns out when the flow velocity is smaller than some threshold value. When the flow velocity is high and the Mach number of the flow approaches unity, throttling effects and “thermal blocking” of the jet are observed.

Deeply undercritical microwave discharge excited by the field of a quasi-optical electromagnetic beam in a supersonic air jet

Electric discharge in a supersonic air jet is studied. It is ignited in a linearly polarized quasi-optical microwave electromagnetic beam the initial field intensity of which is much lower than the breakdown level. Electric breakdown is initiated by a tubular electromagnetic vibrator, one end of which has spikes and is covered by a quartz tube. Atmospheric air enters into a low-pressure working chamber through the inner channel of the vibrator. As a result, an immersed supersonic air jet forms in the chamber at the outlet from the quartz tube. A microwave discharge ignited in this jet is “attached” to aft spikes of the vibrator. The energy deposit into the discharge plasma and the effective area of energy interaction between the discharge and excited microwave field are estimated from the temperature and stagnation pressure distributions in the wake of the discharge.

Investigation of the Vibrational Mode of a Long Bone – The Ulna

An excised and dried ulna was vibrated at its balance pnoint about 42% (0.1m) along the length from the olecranon process, using an electromagnetic vibrator. The vibration was carried out in the anterior-posterior plane. The bone response to the mechanical vibration was picked up at equal intervals (0.02m) along the length of the bone in the plane of the vibration, using an accelerometer attached to the bone. From the response curve of the bone, the resonant frequencies at the various pick- up positions were identified. Analysis of the data shows that when the responses were picked up using the accelerometer at 0.02m proximal, and 0.1m distal, to the point of vibration, the excised ulna vibrated in the fundamental mode like a fixed-fixed beam at resonant frequencies of 340 Hz and 355Hz respectively. For resonant frequencies greater than 650 Hz, the ulna vibrates like a fixed-free beam and at modes greater than the fundamental. It is suggested from this study that the vibration of the long bone in the fundamental mode lends itself to detailed analysis in the use of resonant frequency method in the assessment of the bone quality.

Device for the generation of or monitoring of vibrations

The present invention relates to an electromagnetic vibrator of variable reluctance type, according to a new principle which provides higher efficiency, smaller dimension, and higher reliability compared to known technology. This has been obtained by that the magnetic signal flux generated by the coil is closed through a bobbin body and one or more yokes, and wherein the bobbin body and the yokes are made of laminated metal sheets having good magnetic properties.

Microwave breakdown of air initiated by a short electromagnetic vibrator

The electrical breakdown of air (under a pressure from several tens of Torr to several hundreds of Torr) is initiated in a linearly polarized quasi-optical microwave beam using a rounded-end cylindrical metallic electromagnetic vibrator placed parallel to the electric component of the microwave field. The vibrator is much shorter than the wavelength of the field. The field strength at the top of the vibrator as a function of its length is determined. An empiric expression relating the field strength at the top with the vibrator length-to-diameter ratio is found for the vibrator length range studied. The practicability of locally measuring the field in a quasioptical microwave beam is substantiated. The idea is to determine the maximal air pressure at which electrical breakdown of air initiated by a short vibrator placed at a given point of the beam takes place.

Propane–Air Mixture Combustion Assisted by MW Discharge in a Speedy Airflow

In this paper, results are presented from an experimental investigation of propane-air combustion in a stationary microwave (MW) discharge at different conditions. In these experiments, a deeply undercritical discharge is initiated in the base of an electromagnetic vibrator, which is immersed in cold supersonic airflow. Two schemes for mixing propane with air are considered. In the first scheme, a propane-air mixture is delivered through the vibrator and is ignited at the outlet from the vibrator. In the second scheme, propane delivered through the vibrator mixes with air captured by an inlet hole in the vibrator nose prior to being also ignited by the MW discharge at the base of the vibrator. Propane combustion with efficiency of approximately 60% was demonstrated at a mixture velocity up to 200 m/s in the combustion region. The heat release reaches approximately 1 kW at a propane mass flow rate of 2middot10-2 g/s and discharge power of approximately 200 W

Libration Controller of Electromagnetic Vehicle Vibrator

Electromagnetic Vehicle Vibrator is a non-explosive seismic source, for high resolution detection of underground information, which is used for mineral resources reconnaissance and detecting special target underground abroadly. The work principle comes from Chirp radar technique, the main task is sending Chirp signal with strict controlled parameter to underground. The Chirp signal produced by Electromagnetic Vehicle Vibrator is sent to underground by power amplification and vibrator drived electromagnetism. So the quality of signal influences the whole performance index of seismic explosive system. This thesis discusses hardware and sorfware of Electromagnetic Vehicle Vibrator.

Ultrasonic characterization of granites obtained from industrial quarries of Extremadura (Spain)

The industry of ornamental rocks, such as granites, represents one of the most important industrial activities in the region of Extremadura, SW Spain. A detailed knowledge of the intrinsic properties of this natural stone and its environmental evolution is a required goal in order to fully characterize its quality. In this work, two independent NDT acoustic techniques have been used to measure the acoustic velocity of longitudinal waves in different prismatic granitic-samples of industrial quarries. A low-frequency transceiver set-up, based on a high-voltage BPV Steinkamp instrument and two 50 kHz probes, has been used to measure pulse travel times by ultrasonic through-transmission testing. In complementary fashion, an Erudite MK3 test equipment with an electromagnetic vibrator and two piezoelectric sensors has also been employed to measure ultrasonic velocity by means of a resonance-based method, using the same types of granite varieties. In addition, a comprehensive set of physical/mechanical properties have also been analyzed, according to Spanish regulations in force, by means of alternative methods including destructive techniques such as strength, porosity, absorption, etc. A large number of samples, representing the most important varieties of granites from quarries of Extremadura, have been analyzed using the above-mentioned procedures. Some results obtained by destructive techniques have been correlated with those found using ultrasonic techniques. Our experimental setting allowed a complementary characterization of granite samples and a thorough validation of the different techniques employed, thus providing the industry of ornamental rocks with a non-destructive tool that will facilitate a more detailed insight on the properties of the rocks under study.

Design and Application of an Electromagnetic Vibrator Seismic Source

Vibrational seismic sources frequently provide a higher-frequency seismic wavelet (and therefore better resolution) than other sources, and can provide a superior signal-to-noise ratio in many settings. However, they are often prohibitively expensive for lower-budget shallow surveys. In order to address this problem, I designed and built a simple but effective vibrator source for about one thousand dollars. The ‘‘EMvibe’’ is an inexpensive electromagnetic vibrator that can be built with easy-to-machine parts and off-the-shelf electronics. It can repeatably produce pulse and frequency-sweep signals in the range of [Formula: see text], and provides sufficient energy for recording at offsets up to [Formula: see text]. Analysis of frequency spectra show that the EMvibe provides a broader frequency range than the sledgehammer at offsets up to [Formula: see text] in data collected at a site with soft sediments in the upper several meters. The EMvibe offers a high-resolution alternative to the sledgehammer for shallow surveys. It is well-suited to teaching applications, and to surveys requiring a precisely-repeatable source signature.

Nonlinear analysis on the coupling process of electromagnetic vibrator and earth

The linear model based on the hydraulic pressure vibrator has been no longer adaptable to the electromagnetic vibrator. In order to realize the effective transmission of the limited energy from the vibrator to the ground, it is important to study the coupling model of the electromagnetic vibrator and the earth. In this paper, a nonlinear restore term was introduced to the coupling model because of the existence of a large amount of harmonics in the vibrator baseplate. The nonlinear vibration analysis was applied to the model by the multiscale method. In the course of energy transmission from the vibrator to the ground, ultraharmonic resonance was used to explain the generation of harmonics. An improved scheme was advanced to select the cross correlation reference signal in the vibrator seismic exploration. Good application results were obtained in field experiments.

Granular gas in weightlessness: The limit case of very low densities of non interacting spheres

Experiments on non interacting balls in a vibrated box are reported. In a first experiment with an electromagnetic vibrator on earth or in board of Airbus A300 of CNES, the 1-ball dynamics exhibit little transverse motion and an intermittent quasi periodic motion along the direction parallel to the vibration. This behaviour proves a significant reduction of the phase space dimension of this billiard-like system from 11- d to 3- d or 1- d. It is caused by dissipation, which generates non ergodic dynamics. This experiment exemplifies the coupling between translation and rotation degrees of freedom during the collisions with the walls, due to solid friction at contacts. This eliminates ball rotation and freezes transverse velocity fluctuations. This trend is confirmed by 3d simulations with JJ Moreau discrete element code. A two-ball experiment performed under zero-g conditions in the Maxus 5 flight confirms the trend; the quasi-periodicity is found much greater, which is probably due to an improvement of experimental conditions. The two balls are not in perfect synchronisation showing the effect of small random noise; but the particles has never collided. This is then the normal dynamics of a gas of non-interacting dilute spherical grains in a vibrated container.

Effect of axial vibration on free surface flows in cylindrical liquid

The influence of axial vibration on free surface flows in an open cylindrical container was studied by optical in situ observation method under isothermal conditions. This ground-based experiment was performed on an electromagnetic vibrator with oscillatory frequency of 100Hz. Water–glycerol mixture was chosen as the model liquid. Results showed that small amplitude (<100μm) could generate a new type of steady streaming flows on a free surface, which were mainly driven by the combination of propagating surface wave and Stokes layer effect. The steady flow manifested various patterns according to the vibration amplitude level. Higher amplitude made steady flow periodical or turbulent, which could be characterized by the critical vibrational dimensionless Reynolds number (Nre)c. The calculated value of (Nre)c was of the magnitude of 10−2−10−1. In addition, surface streaming velocities were measured by the particle scattering technique. It was found that the velocity increased parabolically with vibration amplitude and decreased with viscosity for a fixed flow pattern.