The results of studying the influence of parameters such as the force of pressing an eddy current probe (ECP) against the surface of a test object on the outcomes of eddy current testing of structural steel sheets are presented. Experimental values of the ECP added resistances obtained through multifrequency measurements were used to isolate the parameter being tested. Dependences of these resistances on the pressing force and the thickness of the steel sheet for a surface-mounted eddy current probe were identified. A method for processing eddy current measurement results is proposed, ensuring the suppression of interfering parameters and reliable isolation of the tested parameter.

The results of the study of the effect on the results of eddy current testing of the thickness of structural steel sheets of such a parameter as the force of pressing the eddy current sensor to the surface of the object of control are presented. To isolate the controlled parameter, experimental values of the introduced resistances of an eddy current converter obtained using multi-frequency measurements were used. The dependences of these resistances for the overhead eddy current transducer sensor on the clamping force and thickness of the steel sheet are revealed. A method for processing the results of eddy current measurements is proposed, which ensures the elimination of interfering parameters and reliable isolation of the controlled parameter.

In the paper, the acoustic emission of annealed and unannealed titanium alloys is investigated. Interrelationships between registered acoustic emission signals and deformation processes taking place inside the investigated materials are revealed. The observed peaks of acoustic emission signals for unannealed titanium alloys are related to the dislocation glide inside grains, the appearance of small twins and microcracks at the final stage of tension. Acoustic emission signals are found to be different for annealed titanium alloys. There are two distinct peaks of acoustic emission signals, and the first one is due to dislocation processes, while the second one is related of large twins. The frequency and energy features of acoustic emission signals are analyzed using the discrete wavelet transform approach. Calculated wavelet transform coefficients are treated then as new informative parameters processed further by the principal component analysis method. This approach allows the qualitative processing and analysis of differences between acoustic emission signals of annealed and unannealed titanium alloys. Obtained results can be used for acoustic emission testing of titanium alloys.

In this paper, the acoustic emission (AE) under static tension of Pb-Sn alloys is studied. It is revealed that the Kaiser effect is not observed under repeated loading of the material at component concentrations leading to the formation of a eutectic structure. The Principal Component Analysis (PCA) is utilized to extract and analyze the amplitude and frequency features of AE signals. Registered AE signals are divided into blocks to extract the informative parameters as feature vectors representing amplitude and frequency features of the registered AE signals. Processing results help clarify the influence of plastic deformation on the studied phenomenon. Obtained results can be used to analyze acoustic emission testing results of various materials under plastic deformation and study the deformation behavior of materials.

In this study, multi-frequency eddy current testing of carbon steel St3 specimens with dielectric coatings is conducted. Inhomogeneity of steel structure of the specimens with the same chemical composition plays a crucial part during the testing. Plotted experimental hodographs allow investigation of the combined influence of magnetic permeability, electrical conductivity, and thickness of the dielectric coating. The principal component analysis is used to improve testing parameter identification and differentiate the influencing factors. The applied analysis demonstrates non-overlapping clusters of points that represent the eddy current testing data of different steel specimens. The proposed approach can be used for the non-destructive eddy current testing of magnetic steel products with protective-strengthening coatings.

Non-destructive eddy current diagnostics of the structure, composition, physical and mechanical properties of ferromagnetic materials, as well as eddy current monitoring of the operational parameters of products manufactured from them, requires knowledge of the magnetic characteristics of these materials. In eddy current measurements, the results obtained are influenced by a significant number of factors — magnetic and electrical properties of materials, geometric characteristics of products, measurement conditions, design features of an eddy current sensor, etc. Also, the magnetic properties themselves have high structural sensitivity. Thus, identification of the diagnosed parameters puts great importance on the tasks to separate the influencing factors and isolate the contribution of the magnetic properties. This paper describes the measuring and computing system that allows automatic determination of the magnetic permeability of soft magnetic ferromagnetic materials at various values of the strength of the external magnetizing field. The system has been tested using soft magnetic ferrites samples. An experimental dependence of the magnetic permeability on the magnitude of the magnetic field for the initial section of the main magnetization curve is presented. The obtained initial magnetic permeability is compared with the data of independent indirect measurements. The proposed system provides an increase in the reliability and accuracy of the results of the experimental determination of magnetic characteristics and can be used for non-destructive diagnostics of products made of soft magnetic ferromagnetic materials.

Eddy current (EC) measurements, widely used for diagnostics of conductive materials, are highly dependent on physical properties and geometry of a sample as well as on a design of an EC-sensor. For a sensor of a given design, the conductivity and thickness of a sample as well as the gap between the sample and the sensor (lift-off) are the most influencing parameters. Estimation of these parameters, based on signals acquired from the sensor, is quite complicated in case when all three parameters are unknown and may vary. In this paper, we propose a machine learning based approach for solving this problem. The approach makes it possible to avoid time and resource-consuming computations and does not require experimental data for training of the prediction models. The approach was tested using independent sets of measurements from both simulated and real experimental data.

The effect of low temperature on the properties of moisture-saturated glass-fiber-reinforced plastic KAST-B was investigated by studying acoustic emission. During cooling of dried and moisture-saturated specimens with surface defects, the rms acoustic emission and the acoustic emission count rate remain within the background noise. It was determined for the first time that, if water is localized in a crack in the glass-fiber-reinforced plastic, then its cooling leads to an intense acoustic emission. It was assumed that this emission is caused by local damages of the polymer matrix because of the increase in the internal stresses as water turns to ice.

Atmospheric moisture is one of the main climatic factors for polymer composite materials and has the greatest impact on the surface layers of materials. In a cold climate and in seasonal and daily climatic thermal cycling at a transition below 0 °C, the accumulated water in the pores and capillaries of polymeric materials accelerates the appearance of microcracks, their coalescence and the formation of macrodamages in the bulk of the binder and at the boundary with the fibers. The paper presents the results of experiments to study the effect of low temperature on the properties of water-saturated fiberglass with a macrocrack by the method of acoustic emission. Comparative analysis of dried and water-saturated glass fiber laminate samples, containing 0.98% water, showed that for water-saturated samples, acoustic radiation is observed with a pulse amplitude that is more than two orders of magnitude higher than the background. This makes it possible to associate acoustic emission pulses with ice crystallization processes, an increase in internal stresses during the transition of water into ice at the crack tip, and multiple acts of microdamage to the binder generating acoustic pulses. The indicators of the emerging microdamages in the polymer matrix and at the interface between it and the filler are the mean square value of acoustic emission voltage.

The effects of temperature and moisture on the properties of polymer composite materials in cold climates have been considered. A review and analysis of changes in the mechanical properties of polymer composite materials under the influence of temperature and moisture are carried out with reference to foreign and Russian scientific literature. Examples are revealed that show that the deterioration of the mechanical parameters of polymeric composition materials after exposure at open stands in a moderately cold, cold, and extremely cold climate is comparable or even more significant than after staying in warm and humid regions. The mechanism of aging of polymeric composition materials in cold climates has been substantiated and the conditions under which their mechanical properties deteriorate more significantly than when exposed in dry and humid tropics and subtropics have been substantiated. Composites develop internal stresses, caused by unequal thermal expansion of reinforcement fibers and polymer matrices. The internal stresses cause an occurrence of micro-cracks, their coalescence, and the formation of macro-damages in the bulk of a binder or at the interface with fibers.

The influence of solar radiation as a factor of climatic impact on polymer composite materials has not been studied enough. Under the influence of the ultraviolet component of solar radiation, even in cold climates, the surface of materials undergoes destruction and micro-cracking. This destruction is enhanced by capillary condensation of moisture, which at low climatic temperatures increases internal stresses, leading to the formation of microcracks, because of which the strength of polymer composite materials decreases. An algorithm for modelling of polymer composite material aging in cold climates and for identification of significant environmental factors is proposed. Expansion and systematization of experimental data on properties of polymer composite materials exposed to various climatic conditions, including in a cold climate, are anticipated to develop application of extrapolation methods.

Abstract The purpose of this work is to study the effect of rapid thermal annealing (RTA) with halogen lamps on the structural and phase characteristics of lead zirconate-titanate (PZT) films. The PZT thin films with a thickness of 1.0 ± 0.1 μm were deposited by high-frequency reactive plasma sputtering in an oxygen atmosphere on oxidized silicon and silicon substrates with orientation (100). After deposition, the PZT films subjected to RTA at temperatures of 500 °C, 600 °C and 700 °C at a rate of 60 °C/s. The structural-phase composition of PZT films was determined with X-ray diffraction analysis. Studies of heterostructures with scanning electron microscopy methods have shown that increase in the temperature of the RTA leads to a qualitative change in the structural-phase state of the PZT film as compared to its initial state. This makes it possible effectively using of RTA in the formation of PZT films with specified parameters.

This paper investigates acoustic emission of annealed and unannealed Ti alloys under static tension. Unannealed Ti alloys have three distinctive AE peaks related to different stages of strain hardening. There is a significant difference in AE signal form and two peaks for annealed Ti alloys. Discrete wavelet transform is used to analyze the measured acoustic emission peaks quantitatively. Calculated informative parameters of acoustic emission allow establishing the relation between acoustic emission and mechanisms of plastic strain and rupture under loading of Ti alloy. Obtained results can be used to analyze acoustic emission testing results of Ti alloys.

Multifrequency eddy current measurements of the thickness of non-magnetic metallic materials with dielectric coatings have been carried out. Based on the principal component analysis, the influence of competing factors such as electrical conductivity, thickness of the metal substrate and thickness of the dielectric layer is separated. Using the projection method on latent structures, eddy current measurements have determined the numerical values of the thicknesses of aluminum and copper plates and dielectric coatings.

On the example of aluminum alloy AMg5 м plastic deformation and fracture under static loading was investigated.For the material being loaded, a stage of linear hardening, two stages of parabolic hardening and a fracture stage were identified.A change in the form of acoustic emission signals was established with a change in the region of strain hardening.The plastic yielding in the first region was accompanied by the formation of an acoustic emission peak, which was replaced in the next stage by high-amplitude oscillations.Further, for the region of discontinuous yielding, bursts of signals of different amplitude were observed, reflecting the dynamics of the formation of localized deformation bands.The change in the acoustic emission signals reflected the evolution of the deformation hardening processes.To describe the effect of the stagedness of deformation processes on the parameters of acoustic emission, the initial acoustic-emission signal was divided into separate time blocks.To each of these blocks, a discrete wavelet transform was applied.It characterized the time dependence of the waveform on the specific section of the strain hardening curve corresponding for each block.The obtained wavelet decomposition coefficients were processed using principal component analysis.They were plotted on the plane of the first principal components.The points of the multidimensional space corresponded to different regions were divided into partially overlapping clusters.The results of the work showed that the wavelet decomposition coefficients of acoustic emission signal could be used for diagnostics of the stages of strain hardening in aluminum alloys.

In this paper, a study on the application of acoustic emission for monitoring of deformation behavior of lead under static tension has been conducted. It is found out that characteristics of acoustic emission signals change significantly along with the changes of strain-hardening stages. It corresponds to changes of dominant physical mechanisms of deformation under loading. Acoustic emission characteristics and their dependence on the strainhardening stages are analyzed with the principal component analysis. The registered signals are split into small blocks where each block corresponds to the respectful part of the loading curve. A set of informative parameters related to energy and frequency characteristics of the registered signals describes the acoustic emission for each block. The performed processing provides the relation between the acoustic emission and the strain-hardening stages. The obtained results can be used in the acoustic emission study of stages of plastic deformation processes in materials and be helpful for identification of their deformation behavior.

Using the example of nonmagnetic metallic materials, the projection methods of multidimensional analysis of multifrequency eddy-current testing measurement data presented for processing are considered. Based on the principal components method, the effects of electrical conductivity and sensor–material-surface gap on the results of testing have been separated. Using regression on principal components, the numerical values of the electrical conductivity and gap for manganese, copper, bronze, aluminum, and an aluminum alloy have been obtained. The results make it possible to extend the possibilities of nondestructive eddy-current evaluation of materials.

The article deals with the problem of speaker identification, which uses short phrases in noisy environment. The speaker identification in harsh conditions (short phrases, noisy environment) is an actual task, since it is in harsh conditions that the possibilities of the methods used in identification are manifested. Short phrases are characterized by a minimum content of informative elements (phonemes). Usually the duration of short phrases varies hundreds of milliseconds up to several seconds, which leads to certain difficulties in identifying a person by voice. As a method of extracting voice attributes, it is proposed to use the Morlet wavelet transforms. The speakers identification results obtained on basis of the k-nearest neighbors method are presented. Identification results were obtained on the basis of voice records from the database “Acoustic speech signals for the identity system by voice data.” Noisy conditions were formed by additive overlap of different noise levels on voice records. The most important types of noise in real conditions were used white noise, speech-like noise and street noise. The approach proposed is recommended to be used in identification systems with access control of information security.

An automation of eddy current measurements can increase accuracy and reliability of eddy current diagnostics. The automation by using virtual instruments provides greater adaptability of eddy current measurements to changing conditions and control modes, and increases the speed and performance of control operations. In this paper, we present a computer-measuring complex for multi-frequency eddy current diagnostics that includes virtual instruments developed in LabView's graphical programming environment. Recorded digital signals are processed, and hodographs of the "controlled object – eddy current sensor" in a given frequency range are calculated with the help of these virtual devices. Experimental hodographs are produced for copper plate testing samples of various thicknesses with applied dielectric layer. The influence of material and dielectric layer thicknesses on the shape and arrangement of hodograph lines is described and analyzed. Distinguishability of various competing factors affecting the results of eddy current diagnostics is investigated.DOI 10.14258/izvasu(2017)4-03

Рассмотрены возможности многочастотных вихретоковых измерений для проведения неразрушающего контроля геометрических характеристик металлических материалов. С целью расширения таких возможностей экспериментальные годографы для образцов, представлявших собой медные пластины различной толщины с нанесенными диэлектрическими покрытиями, были подвергнуты обработке с помощью проекционных методов многомерного анализа данных. Применение метода главных компонент обеспечило достаточно надежное разделение влияющих на контролируемые параметр конкурирующих факторов — толщин металлической пластины и диэлектрического слоя. Использование метода регрессии на главные компоненты дало возможность построить математические модели, позволившие по экспериментальным годографам с достаточно высокой точностью определить по результатам одного измерения толщину диэлектрического покрытия и в случае относительно тонких образцов толщину металлического листа. Полученные результаты расширяют возможности вихретокового контроля металлических материалов и могут быть применены при неразрушающей диагностике изготовленных из них изделий и конструкций. Ключевые слова: метод вихревых токов, контроль материалов, многомерный анализ данных, метод главных компонент. In the paper, the potentials of multi-frequency eddy current measurements for non-destructive testing of geometric characteristics of metallic materials are considered. To enhance such potentials, experimental hodographs for copper plate testing samples of various thicknesses with applied dielectric layer are processed by projection methods of multidimensional data analysis. Application of principal component analysis ensures a sufficiently reliable separation of competing factors that affect the controlled parameter-the thicknesses of a metal plate and a dielectric layer. Principal components regression allows for the development of mathematical models for highly accurate evaluation of dielectric layer thickness and thickness of a metal plate for relatively thin samples. Obtained results significantly enhance the potentials of eddy current testing of metallic materials and can be used for nondestructive diagnostics of products and structures made of them.