Дифференциальный фон электрического сигнала, снимаемого с индукционной магнитной головки

2021 ◽  
pp. 51-61
Author(s):  
В.В. Павлюченко ◽  
Е.С. Дорошевич
Keyword(s):  
Inhomogeneous Magnetic Field ◽  
Measuring System ◽  
Local Source ◽  
Electric Signal ◽  
Natural Oscillations ◽  
Electric Voltage ◽  
Frequency Spectra ◽  
Useful Signal ◽  
Sufficient Magnitude ◽  
Local Defects

Experimental dependences U(t) of the electric voltage taken from an induction magnetic head (MH) moving relative to a magnetic carrier (MH) are presented. The backgrounds of the edges of the MN, local defects of the MN, the background of the inhomogeneous magnetic field of the local source, the backgrounds of defects and structural inhomogeneities of the object, the etheric electromagnetic background, the background of the quality of the surface of the object and surface microscopic inhomogeneities of the material have been identified and investigated. The resonant backgrounds of self-excitation of the measuring system on the signals of the edges of the MN, defects of the MN, instrument and network pickups and interference, object defects, and etheric electromagnetic fields are revealed and investigated. Resonance peaks are the result of self-excitation of the measuring system, which includes the MG, and arise on the trailing edges of any signals of sufficient magnitude, the duration of the trailing edge of which is about a quarter of the period of natural oscillations of the measuring system. The amplitude and frequency spectra of the background signals of object defects, MI and noise and the analytical expressions describing them are determined. The results of the extraction of the useful signal from the complete signal recorded on the MN are shown. Investigations of the differential background of an electric signal allow, together with the previously developed methods of hysteresis interference, to control the properties of objects in an automatic mode with program control, which significantly increases the sensitivity and accuracy of control. To achieve this goal, it is recommended to set the parameters of the measurement system at the threshold of the onset of natural free oscillations in it.

Elastic characteristics of isolated segments of human aortas under dynamic conditions

1959 ◽  
Vol 14 (1) ◽  
pp. 55-59 ◽  
Author(s):  
Freeman W. Cope
Keyword(s):  
Hysteresis Loop ◽  
Thoracic Aorta ◽  
Measuring Equipment ◽  
Time Lag ◽  
Measuring System ◽  
Time Lags ◽  
Descending Thoracic Aorta ◽  
System A ◽  
Sufficient Magnitude ◽  
Elastic Characteristics

When isolated segments of human descending thoracic aorta were caused to change their volume rapidly and continuously in sinusoidal fashion with pulse pressures and pulse rates maintained in the physiological range, the resulting pressure-volume curves showed slight but consistent increases in stiffness, compared to pressure-volume curves obtained on the same specimens when inflated stepwise. There was introduced into the pressure measuring system a time lag of sufficient magnitude to eliminate the hysteresis loop. The extent of hysteresis in the aorta was not determined because time lags in the aorta could not be distinguished from time lags in the measuring equipment. Submitted on September 10, 1958

INVESTIGATION OF THE SPECIFICITY OF ULTRASONIC TESTING OF CAST IRON WITH GLOBULAR GRAPHITE USING LONGITUDINAL ELASTIC WAVES

2020 ◽  
pp. 6-25 ◽  
Author(s):  
V. N. Danilov ◽  
L. V. Voronkova
Keyword(s):  
Cast Iron ◽  
Ultrasonic Testing ◽  
Rayleigh Scattering ◽  
Frequency Spectra ◽  
Longitudinal Waves ◽  
Globular Graphite ◽  
Useful Signal ◽  
Two Samples ◽  
Standard Normal ◽  
Experimental Values

On the basis of the previously developed model for estimating the attenuation coefficient of elastic longitudinal waves in cast iron due to their Rayleigh scattering on graphite inclusions, the influence of such attenuation for cast iron with globular graphite on the characteristics of signals with frequency spectra of different widths depending on the nominal pulse frequencies, cast iron models and the distance traveled by the ultrasonic wave is studied. Computer modeling acoustic channel for environment – cast iron with globular graphite for standard normal probes of two types for studying influence of such environment on characteristics real transmitting and registered signals at the ultrasonic testing. Comparison of results of calculations of spectrums and pulses of registered bottom signals with their experimental values for two samples of cast iron with globular graphite has shown an opportunity of use of the applied settlement model for description of the actual physical phenomena quite adequate for practice. Influence of attenuation of longitudinal waves in cast iron with globular graphite on the directivity characteristic of their radiation is shown on model of cast iron and duration of a pulse. The estimation of the relation of levels of a registered signal and structural noise for various reflectors and characteristics of controllable cast iron has shown performance of recommendations by I. N. Ermolov on reliable detection of a useful signal on a background of noise for thickness, before established experimentally. Features of DGS-diagrams for cast iron with globular graphite, caused by higher, than in steel, attenuation of longitudinal waves and a little smaller speeds of their distribution are marked.

An Investigation of Rolling Element Vibrations Caused by Local Defects

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
H. Arslan ◽  
N. Aktürk
Keyword(s):  
Equations Of Motion ◽  
Angular Contact Ball Bearing ◽  
Frequency Spectra ◽  
Rolling Element ◽  
Rolling Elements ◽  
Computer Simulation Program ◽  
Localized Defects ◽  
Spring System ◽  
Mass Spring ◽  
Local Defects

In this paper, a shaft-bearing model is developed in order to investigate the rolling element vibrations for an angular contact ball bearing with and without defects. The shaft-bearing assembly is considered as a mass-spring system. The system shows a nonlinear characteristic under dynamic conditions. The equations of motion in radial and axial directions were obtained for shaft and rolling elements, and they were solved simultaneously with a computer simulation program. Additionally, the effect of localized defects on running surfaces (i.e., inner ring, outer ring, and ball) on the vibration of the balls is investigated. Vibration of rolling elements in the radial direction is analyzed in time and frequency domains. Characteristic defect frequencies and their components can be seen in the frequency spectra of rolling element vibrations. Comparison of the obtained results with similar studies available in literature showed reasonable qualitative agreement.

An Experimental Approach in Defect Detection of a Single Row Ball Bearing Using Noise Generation Signal

2019 ◽  
Author(s):  
Aref Afsharfard ◽  
Seyed Hamid Reza Sanei
Keyword(s):  
Ball Bearing ◽  
Experimental Testing ◽  
Local Defect ◽  
Noise Generation ◽  
Frequency Spectra ◽  
Single Row ◽  
Outer Race ◽  
Bearing Defects ◽  
Cost Efficient ◽  
Local Defects

Abstract Bearings are critical mechanical components that are used in rotary machinery. Timely detection of defects in such components can prevent catastrophic failure. Noise is generated during the rotation of bearings even without the presence of defects due to finite number of rotating elements to carry the load. Such noise is associated with the change in effective stiffness during rotation, however, a sharp spike is observed in the noise level with presence of local defects. This study uses the noise generation aspect of roller bearings to identify local defect in a single row ball bearing with outer race stationary under radial load. Experimental testing is conducted on two identical bearings. The defective bearing is selected from a diesel engine subjected to 20 years of service. Dissecting the defective bearing revealed pitting and spalling of the inner race and balls, the most two common bearing defects. Both time and frequency analysis of sound pressure generated by the bearings were performed. The results show that there is a clear distinction in the time and frequency spectra between healthy and defective bearings. Findings of this study revealed that using a simple cost efficient in-house experimental setup, local defects can be readily detected.

DETECTION OF INTEGRITY DEFECTS IN ALUMINUM SPECIMENS BY THE MAGNETIC PULSE METHOD

2019 ◽  
Vol 85 (4) ◽  
pp. 28-32
Author(s):  
Vladimir V. Pavlyuchenko ◽  
Elena S. Doroshevich
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Pulse Method ◽  
Magnetic Pulse ◽  
Magnetic Field Direction ◽  
Magnetic Carrier ◽  
Electric Voltage ◽  
Useful Signal ◽  
Measurement Plane ◽  
Aluminum Plates

Experimental time dependences of the electric voltage U(t), taken from the induction magnetic head when scanning it with a magnetic carrier with magnetic field records of artificial defects of the integrity (slits) with a width of (1.0 - 10.0) x 10-5  m in aluminum plates from 1.5 x 10-6 to 2.0 x 10-3 m are presented. On the magnetic carrier the magnetic fields of the defects that occur when aluminum plates are exposed to a pulse of magnetic field of plane inductor (action time of about 1.0 x 10-4 sec). Dependences of U(t) for different depths of bedding of the defects and thickness of the layer of the material above them in the specified ranges of influences are obtained. In this case, distributions of instantaneous magnetic fields are recorded on the surface area of objects of the order of 1.0 x 10-3 m2 with a resolution in the measurement plane of 1.0 x 10-8 m2. The novelty of the method consists in determination of the amplitude of the main pulse of the field and build up time, the shape of the leading and trailing edges, as well as the amplitude, build up time, the number and polarity of the outliers of magnetic field, direction of the applied field, operations of smoothing, calculation, separation of the useful signal and operations of recognition of the defect information recorded on the magnetic medium with analysis of the dependences U(t). The developed method for controlling objects from electrically conductive materials makes it possible to increase several times the accuracy and speed of the control of the integrity defects in diamagnetic and paramagnetic metals.

scholarly journals Using POD method in experiments with convection flow on the cube benchmark

2019 ◽  
Vol 213 ◽  
pp. 02071
Author(s):  
Daniil Sergeev ◽  
Alexander Kandaurov
Keyword(s):  
Low Cost ◽  
Velocity Fields ◽  
Measuring System ◽  
Convection Flow ◽  
Vertical Temperature Gradient ◽  
Vertical Temperature ◽  
Continuous Laser ◽  
Frequency Spectra ◽  
Ansys Cfx ◽  
Good Agreement

Investigations of the flow structure on the benchmark “cube” under conditions of natural convection caused by a vertical temperature gradient are performed using a low cost PIV-measuring system with continuous laser. The obtained velocity fields were processed with POD method to obtain typical structures (modes) in the flow. It is shown that the steady flow can be described by combination of the first three modes. It is demonstrated that only starting with the third mode there is a significant change in the spectra of the amplitude coefficients of the modes, the peak shifts to the region of higher frequencies. Thus accounting for this mode is essential for describing turbulent processes in the system and verification of numerical calculations. Comparison with the results of the LES simulation performed using the Ansys CFX package (taking into account the results of processing the experimental data by the POD method) demonstrated good agreement both in the structure of the modes and in their frequency spectra.

STUDY OF PULSE MODE OF PIEZOELECTRIC TRANSDUCER FOR ECHOSCOPE

2019 ◽  
pp. 50-57
Author(s):  
V. S. Konovalova ◽  
R. S. Konovalov ◽  
S. I. Konovalov
Keyword(s):  
Piezoelectric Transducer ◽  
Soft Tissues ◽  
Active Element ◽  
Pulse Mode ◽  
Piezoelectric Transducers ◽  
Electric Signal ◽  
Stationary Mode ◽  
Piezoceramic Plate ◽  
Electric Voltage ◽  
Broadband Pulse

The piezoelectric transducer of the echoscope intended for research of soft tissues of the person is considered. The active element of the transducer is a damped piezoceramic plate. As an exciting electric signal, an electric voltage pulse with a different number of half‑cycles at the natural frequency of the plate is selected. The pulse mode of the radiator operation is investigated. The amplitudes and durations of the probing acoustic signal are estimated depending on the duration of the exciting pulse. The dynamics of changes in the durations and amplitudes of the radiated acoustic pulses is studied. For various degrees of damping of the plate, the number of half‑cycles contained in the exciting signal, from which the emitter operates in a stationary mode, is determined. The obtained results can be used in the field of design and development of technology for manufacturing of broadband pulse piezoelectric transducers of ultrasonic medical echoscopes.

Alleviation of pain and depression by specific neural transplants: Fine structural correlates

1992 ◽  
Vol 50 (2) ◽  
pp. 1066-1067
Author(s):  
George D. Pappas ◽  
Jacqueline Sagen
Keyword(s):  
Opioid Peptides ◽  
Chromaffin Cells ◽  
Pain Sensitivity ◽  
Opioid Peptide ◽  
Local Source ◽  
Pain Models ◽  
Neural Transplants ◽  
Adrenergic Antagonists ◽  
Csf Levels ◽  
Donor Source

We have been interested in the use of neural transplants mainly as a local source of neuroactive substances, rather than as a replacement for damaged neural circuities. In particular, we have been exploring the possibilities of reducing pain by transplants of opioid peptide producing cells, and reducing depression by transplants of monoamine-producing cells. For the past several years, work in our laboratory has demonstrated in both acute and chronic pain models that transplantation of adrenal medullary tissue or isolated chromaffin cells into CNS pain modulatory regions can reduce pain sensitivity in rodents. Chromaffin cells were chosen as donor source since they produce high levels of both opioid peptides and catecholamines, substances which independently, and probably synergistically, reduce pain sensitivity when injected locally into the spinal cord. The analgesia produced by these transplants most likely results from the release of both opioid peptides and catecholamines, since it can be blocked or attenuated by opiate or adrenergic antagonists, respectively. Furthermore, CSF levels of met-enkephalin and catecholamines are increased by the transplants.

Nuclear magnetic resonance microscopy

1989 ◽  
Vol 47 ◽  
pp. 828-829
Author(s):  
Paul C. Lauterbur
Keyword(s):  
Magnetic Field ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Magnetic Fields ◽  
Signal To Noise ◽  
Field Gradients ◽  
Useful Signal ◽  
Magnetic Field Gradients ◽  
Observation Times ◽  
Nuclear Magnetic

Nuclear magnetic resonance imaging can reach microscopic resolution, as was noted many years ago, but the first serious attempt to explore the limits of the possibilities was made by Hedges. Resolution is ultimately limited under most circumstances by the signal-to-noise ratio, which is greater for small radio receiver coils, high magnetic fields and long observation times. The strongest signals in biological applications are obtained from water protons; for the usual magnetic fields used in NMR experiments (2-14 tesla), receiver coils of one to several millimeters in diameter, and observation times of a number of minutes, the volume resolution will be limited to a few hundred or thousand cubic micrometers. The proportions of voxels may be freely chosen within wide limits by varying the details of the imaging procedure. For isotropic resolution, therefore, objects of the order of (10μm) may be distinguished.Because the spatial coordinates are encoded by magnetic field gradients, the NMR resonance frequency differences, which determine the potential spatial resolution, may be made very large. As noted above, however, the corresponding volumes may become too small to give useful signal-to-noise ratios. In the presence of magnetic field gradients there will also be a loss of signal strength and resolution because molecular diffusion causes the coherence of the NMR signal to decay more rapidly than it otherwise would. This phenomenon is especially important in microscopic imaging.

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