Электромагнитные методы контроля изменений напряженно-деформированного состояния диэлектрических материалов

2021 ◽  
pp. 44-53
Author(s):  
А.А. Беспалько ◽  
Д.Д. Данн ◽  
М.В. Петров ◽  
Е.К. Помишин ◽  
Г.Е. Уцын ◽  
...  
Keyword(s):  
Strain State ◽  
Experimental Studies ◽  
Electromagnetic Emission ◽  
Acoustic Excitation ◽  
Acoustic Sounding ◽  
Rock Samples ◽  
Electromagnetic Responses ◽  
Electromagnetic Signals ◽  
Complex Methods ◽  
Sample Axis

Mechanical-electrical and acoustic-electrical complex methods of testing cracking while changing the stress-strain state in dielectrics are discussed on the example of rock samples. The paper discusses the results of numerical and experimental studies of changes in the electromagnetic responses parameters under the pulse deterministic acoustic excitation of rock samples with different composition and texture. Also the results of mathematical calculations of the stress concentration on cracks located along the sample axis are presented, perpendicular to which deterministic acoustic pulses were introduced. The experimental studies results of sample electromagnetic emission with containing calcite and magnetite under uniaxial compression to fracture are shown. Regularities in the electromagnetic signals amplitudes changes during acoustic sounding in the process of «stepwise» uniaxial loading by compression to destruction are given.

scholarly journals The results of experimental studies of VLF–ULF electromagnetic emission by rock samples due to mechanical action

2013 ◽  
Vol 1 (6) ◽  
pp. 7821-7842
Author(s):  
A. A. Panfilov
Keyword(s):  
Laboratory Experiments ◽  
Experimental Studies ◽  
Electromagnetic Emission ◽  
Mechanical Action ◽  
Frequency Range ◽  
Impact Action ◽  
Rock Samples ◽  
Electric Component ◽  
Electromagnetic Signals ◽  
The Impact

Abstract. The paper presents the results of laboratory experiments on electromagnetic emission excitation (electric component of electromagnetic field) by rock samples due to different forms of mechanical stress applications. It was shown that samples generate electric impulses with different spectra when the impact action, gradual loading or dynamic friction is applied. It was ascertained that level and spectral compositions of signals, generated by rock samples, change with increasing quantity of hits. It was found that strong electromagnetic signals, generated while rock samples were fracturing, were accompanied by repetitive weak, but perceptible variations of the electric field intensity in short frequency range.

scholarly journals The results of experimental studies of VLF–ULF electromagnetic emission by rock samples due to mechanical action

2014 ◽  
Vol 14 (6) ◽  
pp. 1383-1389 ◽  
Author(s):  
A. A. Panfilov
Keyword(s):  
Laboratory Experiments ◽  
Experimental Studies ◽  
Electromagnetic Emission ◽  
Mechanical Action ◽  
Impact Action ◽  
Rock Samples ◽  
Electric Component ◽  
Electromagnetic Emissions ◽  
Electromagnetic Signals ◽  
The Impact

Abstract. The paper presents the results of laboratory experiments on electromagnetic emissions excitation (the electric component of electromagnetic fields) by rock samples due to different forms of mechanical stress applications. It was shown that samples generate electric impulses with different spectra when the impact action, gradual loading or dynamic friction is applied. It was ascertained that level and spectral compositions of signals, generated by rock samples, change with an increasing number of hits. It was found that strong electromagnetic signals, generated while rock samples were fracturing, were accompanied by repetitive weak but perceptible variations in the electric field intensity in short frequency ranges.

scholarly journals Comparative analysis of acoustic and electromagnetic emissions of rocks

2021 ◽  
Vol 929 (1) ◽  
pp. 012013
Author(s):  
V N Klyuchkin ◽  
V A Novikov ◽  
V I Okunev ◽  
V A Zeigarnik
Keyword(s):  
Comparative Analysis ◽  
Uniaxial Compression ◽  
High Stress ◽  
Electromagnetic Emission ◽  
Rock Failure ◽  
Dynamic Rupture ◽  
Block Model ◽  
Rock Samples ◽  
Electromagnetic Emissions ◽  
Electromagnetic Signals

Abstract Comparative analysis of acoustic and electromagnetic emissions recorded during the intact rock samples deformation and dynamic rupture of simulated crustal fault is presented. Specialized machines for uniaxial compression and shear tests of rock samples with identical data acquisition systems for both test cases were employed. Increase of acoustic emission was observed accompanied by significant rise of intensity and amplitude of electromagnetic signals at high stress of the rock samples under the uniaxial compression or dynamic failure in the spring-block model. Such correlation is consistent with the previous conclusions that an increase of electromagnetic emission may be considered as a rock failure precursor. Any specific characteristics of the detected electromagnetic signals to be used for prediction of impending rock failure or the earthquake fault rupture were not found. The similarity of electromagnetic signals and their spectra obtained at the press equipment and the spring-block model suggests that in both cases, the signals observed are generated by the crack formations and shear. The electromagnetic emission appeared only in dry samples. The samples saturated by water with the salinity of over 0.1% demonstrated no electromagnetic emission.

Changes in the Parameters of the Electromagnetic Response of Model Dielectric Samples with Air Cavity Defects under External Deterministic Acoustic Impact

2021 ◽  
Vol 101 (1) ◽  
pp. 12-17
Author(s):  
D.D. Dann ◽  
◽  
M.V. Petrov ◽  
P.I. Fedotov ◽  
E.A. Sheveleva ◽  
...  
Keyword(s):  
Experimental Studies ◽  
Dielectric Materials ◽  
Electromagnetic Response ◽  
Average Weight ◽  
Acoustic Excitation ◽  
Ball Impact ◽  
Electromagnetic Signals ◽  
Air Cavities ◽  
The Impact

The paper discusses the possibility of testing the air inclusions saturation in cement-sand samples using the acoustic-electrical transformations phenomenon in heterogeneous dielectric materials. An experiment technique is presented including contact external acoustic excitation and contactless registration of the electromagnetic response to such an impact. Methods of samples deterministic acoustic excitation by a ball impact and the experimental determination of the impact energy are described. The model samples size and composition are described, including air cavities in a polyethylene sheath. The experimental studies geometry is shown, indicating the direction of the samples acoustic excitation and the location of the electromagnetic receiving plates. It is shown that the defect-free samples and with air cavities, have different amplitude and frequency of the electromagnetic signals spectral components. The samples with air cavities have the average weight of the EMS spectrum changes towards lower frequencies. This frequency shift effectively reflects the concentration of air cavities defects in a cement-sand samples and this effect can be used when testing concrete products for the presence of air inclusions, and, accordingly, will allow determining the frost resistance of products.

Analyzing Deformation and Fracture of Dielectrics by Integral Characteristics of their Electromagnetic Emission

2016 ◽  
Vol 683 ◽  
pp. 36-43 ◽  
Author(s):  
Ludmila Yavorovich ◽  
Anatoly Bespal’ko ◽  
Pavel Fedotov ◽  
Aleksey Popelyaev
Keyword(s):  
Strain State ◽  
Electromagnetic Emission ◽  
High Strength ◽  
Dielectric Materials ◽  
Stress Strain ◽  
Rock Samples ◽  
Stress Strain State ◽  
Local Strength ◽  
Deformation And Fracture ◽  
Integral Characteristics

Revealing of fracture harbingers of dielectric materials, that are under mechanical stress, is an important practical and scientific problem. Local stresses, produced by mechanical impact, can exceed the local strength, and a stress-strain state changes. As the result of such impacts, microcracks appear and lead to fracture. During change of stress-strain state, mechanoelectric transformations occur, that generate electromagnetic emission. So we aimed to observe regularities in electromagnetic emission characteristics. Rock samples, collected from Tashtagol ore-mine of Kemerovo region of Russia, were used as dielectric materials for the research. For analysis of rock samples deformation and fracture, integral characteristics of time series of electromagnetic emission were used. Observed, that low-strength samples accumulate and relax elastic energy stepwise unlike to high-strength samples, that accumulate energy linearizely. Differences in dispersion characteristics of samples differing with strength are observed. The research showed usability of suggested algorithms.

scholarly journals Investigation of the structure of cement conglomerates

2021 ◽  
Vol 266 ◽  
pp. 03005
Author(s):  
D. N. Shabanov ◽  
E. Trambitsky ◽  
E. Borovkova
Keyword(s):  
Strain State ◽  
Residual Life ◽  
Experimental Studies ◽  
Cement Stone ◽  
Virtual Model ◽  
Structural Studies ◽  
Acoustic Sensors ◽  
Cement Pastes ◽  
The Moment ◽  
Physical And Chemical

This article describes the structural studies of a cement conglomerate, its evolution from the moment of formation to the loss of operational properties. Physical and chemical phenomena and interactions of various elements of cement stone are considered. The study of its rheology includes creating a virtual model and monitoring the formation of the structure of cement pastes by acoustic emission (AE). The results of combined experimental studies to determine the residual life of cement stone samples using AE and tensometry methods are presented. The authors created a complex for monitoring the stress-strain state of artificial conglomerates, which includes both internal and acoustic sensors.

scholarly journals Numerical simulation of the stress-strain state of complex-reinforced elements

2019 ◽  
Vol 13 (2) ◽  
pp. 110-115
Author(s):  
Olena Krantovska ◽  
Mykola Petrov ◽  
Liubov Ksonshkevych ◽  
Matija Orešković ◽  
Sergii Synii ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Strain State ◽  
Theoretical Calculations ◽  
Experimental Studies ◽  
Theoretical Studies ◽  
Stress Strain ◽  
Narrow Strip ◽  
Stress Strain State ◽  
Graphical Environment ◽  
Experimental And Theoretical Studies

The article describes a developed technique of a numerical simulation of the stress-strain state of complex-reinforced elements, which allows you to create models of double-span continuous. The performed experimental and theoretical studies allowed us to carry out the testing of the developed design model and to justify the reliability of the proposed numerical simulation methodology. The results of the experimental studies were compared with those of the theoretical studies. The theoretical calculus algorithm was developed by using the finite element method. Theoretical calculations were performed by using the mathematical-graphical environment software system LIRA-SOFT and the mathematical and computer program MATLAB. On the basis of the experimental research, the iso-fields of displacements and stresses in the materials of an eccentrically compressed beam with a small bend of the slab were constructed, which collapse behind the inclined narrow strip of concrete and displacements and stresses in the materials of the eccentrically stretched beam, which is destroyed due to the yield of the upper mounting armature.

Flow Field and Vibration Behavior of Straight Transonic Compressor Cascade due to External Acoustic Excitation

2013 ◽  
Author(s):  
Manlu Li ◽  
Anping Hou ◽  
Xiaodong Yang ◽  
Mingming Zhang ◽  
Peng Wang
Keyword(s):  
Flow Field ◽  
Excitation Frequency ◽  
Experimental Studies ◽  
Attack Angle ◽  
Mode Shapes ◽  
Acoustic Excitation ◽  
Fe Model ◽  
Compressor Cascade ◽  
Time Step ◽  
Vibration Behavior

A fluid-structure coupled approach is utilized to study the influence of external acoustic excitation on straight compressor cascade flow field and blade vibration behavior. Interaction between fluid and structure are dealt with in a coupled manner, based on the interface exchange of information between the aerodynamic and structural model. The computation fluid mesh is updated at every time step with an improved algebraic method. The flow field of cascade with/without external acoustic excitation is carried out using a 3D unsteady CFD model based on moving boundary way, as well as some experimental studies based on transonic wind tunnel. Then coupled with blade FE model, mode shapes, frequencies, vibration stress and the structural deformations of blade are identified. The performance of the cascade is obtained by computational and experimental ways, consistency of numerical and test results shows that the numerical model is suitable. The numerical results show that acoustic excitation has a greater impact on negative and designed attack angle in contrast to high positive attack angle. The cascade wake and blade surface pressure frequency characteristic are changed and the main frequency is almost the same as the acoustic excitation frequency. Compared results with no excitation, the vibration characteristics of the blade is changed, also the vibration behavior is sensitive to the excitation amplitude and frequency.

Study of Surface Layer Hardening after Treatment Complex Tool

2020 ◽  
Vol 303 ◽  
pp. 89-96
Author(s):  
K.S. Mitrofanova
Keyword(s):  
Plastic Deformation ◽  
Surface Layer ◽  
Strain State ◽  
Experimental Studies ◽  
Surface Plastic Deformation ◽  
Surface Plastic ◽  
Technological Inheritance ◽  
Multiple Loading ◽  
Surface Layer Hardening ◽  
Solidified Body

The results of experimental studies of the thin surface layer of samples made of steel 45 after treatment with surface plastic deformation (SPD) multiradius roller (MR-roller) are presented. On the basis of the apparatus of the mechanics of technological inheritance, taking into account the effect of the solidified body, a model of the process according to the scheme of multiple loading-unloading of metal, taking into account the phenomenology of the SPD process and the properties of the material, is created. Distributions of parameters of the stress-strain state in the deformation centre are obtained, the parameters of roughness and microhardness of the surface layer are investigated.

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