Instytut Podstawowych Problemów Techniki

Streszczenie:

In the paper two advanced methods for testing cement based composites are described and compared. These are X-ray microtomography and optical microscopy. Microtomography supplies three-dimensional images of small concrete specimens. In the tomograms all cracks, pores and other voids and inclusions, that exceed a few micrometers, are shown. Such visualisation can become a valuable tool for analysis of the basic material properties. Images obtained on thin sections and analysed with various methods on optical microscopes supply additional information on material microstructure that cannot be obtained in tomograms. For example it is relatively easy to determine zone penetrated by CO2 ingress. These two methods, presented on examples of tests, complete each another in order to supply a set of information on composition and defects of tested composite materials.

Słowa kluczowe:

cement matrix composites, concrete deterioration, X-ray tomography, microscopic analysis, concrete microstructure

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Streszczenie:

The paper presents the microscopic and mechanoacoustic study of degradation processes of the porcelain material C 110 type. Small-sized samples, derived from the low voltage insulator, were subjected to a slow, quasi-static compression, with simultaneous recording of acoustic emission descriptors. There were distinguished consecutive stages of the material degradation. Obtained results were compared with the images of the microstructure of low-voltage insulator materials after many years of operation. On this basis, there were distinguished the factors determinant of the short-term strength of porcelain and its resistance to ageing processes under operating conditions.

Słowa kluczowe:

electrical porcelain, microscopic analysis, acoustic emission, degradation of the porcelain

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Streszczenie:

The paper presents the evaluation of the mullite hypothesis explaining the strength of porcelains. There was researched the influence of the mullite phase on the short- and long-term mechanical strength of electrotechnical porcelain of different types (C 110, C 112, C 120 and C 130). The total mullite phase content, the size and distribution of precipitates and dispersed single crystals in the glassy matrix were considered. Mechanoacoustic and microscopic techniques as well as ultrasonic testing were used during the investigation. The role of the mullite phase in the increase of strength and resistance to aging processes of electrical porcelain of various types was described. Mullite hypothesis is valid in reference to siliceous (C 110), cristobalite (C 112) and aluminous C 120 type materials of a typical raw components content and phase composition. In the case of modern strengthened C 120 and C 130 type aluminous materials advantageous are only dispersed fine mullite needles. The precipitates of mullite phase, especially of bigger size, are undesirable.

Słowa kluczowe:

electrotechnical porcelain, porcelain degradation, acoustic emission (AE), microscopic analysis

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Streszczenie:

Ignacy Malecki was born on November 18, 1912, at the family estate of Pokiewnia near Vilnius. After Poland regained its independence in 1918, the town was at the border of the Second Republic of Poland and Central Lithuania. The church and village were located in the Polish area, while the family estate on the Lithuanian side. It took some time before those parts could be reunited.
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Streszczenie:

W pracy przedstawiono badania wpływu fazy mulitowej na krótko- i długotrwałą wytrzymałość mechaniczną elektroporcelan rodzaju C 110, C 112, C 120 oraz C 130. Rozpatrywana była sumaryczna zawartość fazy mulitowej, wielkość i rozłożenie jej wydzieleń oraz niezaglomeryzowanych kryształów w osnowie szklistej. W badaniach wykorzystano metodę mechanoakustyczną, techniki mikroskopowe (MO i SEM) oraz metodę ultradźwiękową. Przedstawiono rolę fazy mulitowej w podwyższeniu odporności na procesy starzeniowe porcelany elektrotechnicznej różnego rodzaju.

Słowa kluczowe:

porcelana elektrotechniczna, degradacja tworzyw porcelanowych, emisja akustyczna, badania mikroskopowe

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Streszczenie:

The paper presents mechanoacoustic and microscopic testing of degradation processes of modern C 120 electrotechnical porcelain of domestic medium voltage line insulator. Samples of small dimensions, cut off from the rod of insulator, were subjected to compressive loading, with recording of acoustic emission descriptors. Microscopic analysis enabled determining the advancement of degradation effects. Three stages of the structure degradation were distinguished. The effectiveness of dispersive and fibrous reinforcement of modern aluminous porcelain C 120 type has been described. Structural strengthening by corundum grains and mullite needle shaped crystals improves mechanical parameters and distinguishes this material from typical aluminosilicate ceramics. The presented results enable drawing up the conclusions concerning the resistance of investigated material to the ageing degradation process development during long term operation.

Słowa kluczowe:

aluminous porcelain, structural degradation, acoustic emission (AE), microscopic analysis

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Streszczenie:

This experimental paper comprises the results of acoustic emission (AE), microscopic and ultrasonic measurements of samples subjected to slowly increasing compressive stress. On the basis of conducted measurements the successive stages of the material structural degradation have been recognized. The objects of study were samples made of C 120 aluminous porcelain. The investigated material has found at present the application in the fabrication of technical elements like overhead power line insulators. In the case of such objects, not only high mechanical strength, but especially elevated durability as well as operational reliability are required. The expected „life time” of net insulators during exploitation is about 40 years. The analysis of obtained mechanoacoustic dependences pointed out a complex mechanism of degradation of the material. Microscopic investigation of samples, which were stressed to different levels of load, enabled to specify the development of gradual growth of microcracks and successive crushing out of elements of the structure. These processes appear to be similar to the ageing processes occurring in the material during long period of exploitation under a working load. Three stages of the structure degradation were distinguished. The preliminary and subcritical ones show low or moderate intensity of AE signals and considerable variety for the particular samples. The critical stage directly precedes the destructtion of samples. Its range is relatively narrow and reveals the AE activity of high energy. The effectiveness of dispersive and fibrous reinforcement of modern aluminous porcelain C 120 type has been described. Structural strengthening by corundum grains and mullite needle shaped crystals improves mechanical parameters and distinguishes this material from typical aluminosilicate ceramics. The presented results enable drawing up the conclusions concerning the resistance of investigated material to the ageing degradation process development during long term operation.

Słowa kluczowe:

aluminous porcelain, ceramic insulators, insulator testing, acoustic emission, microscopic analysis, structural degradation

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Streszczenie:

The paper presents a nondestructive ultrasonic method of investigating long-rod insulators used on overhead power lines and in substations. A correlation between the degree of degradation of porcelain C 120 and the ultrasonic wave propagation and attenuation parameters was established. The ultrasonic method was used to analyze the quality of groups of line and post insulators after many years of service. Also a new mechanoacoustic method of investigating the stages in the degradation of insulator porcelain was applied. As a result of the investigations carried out on samples of porcelain C 130 the successive stages in the degradation of ceramic insulators during their service life were determined.

Słowa kluczowe:

Ceramic insulators, insulator testing, acoustic measurements, ultrasonic applications, acoustic emission

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Streszczenie:

The paper presents the concept of mechanoacoustic testing of degradation processes of ceramic electrotechnical materials. Samples of small dimensions were subjected to slowly increasing compressive loading with simultaneous recording of acoustic emission descriptors. The process was continued to the destruction or it was stopped at various stages of degradation of the material structure. Microscopic analysis of samples enabled determining the effects of stress action.

Słowa kluczowe:

acoustic emission (AE), material degradation, electrotechnical ceramics

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Streszczenie:

This paper presents the results of acoustic emission (AE) measurements of samples under compressive stress. Additional research, concerning structure and parameters of the material, was performed using microscopic and ultrasonic methods. The object of the investigation were samples of porcelain material C 130 type of domestic long-rod insulator LP 75/31W. This kind of aluminous porcelain demonstrates high mechanical and electrical strength as well as resistance to aging degradation processes. It finds wide application in modern electrotechnical engineering. The aim of this study was to recognize stages of degradation processes of the porcelain structure. The present work constitutes a continuation of the study concerning the influence of technological faults, existing in porcelain material structure, on long-term mechanical strength. These results were presented at the OSA Conference in 2006. The analysis of mechanical-acoustic characteristics pointed out diversified strength and complicated mechanism of the material degradation. The effectiveness of the dispersive and fibrous reinforcement of aluminous porcelain C 130 type was ascertained. It was stated during the microscopic investigation that the structure of the material is different from that in the case of typical aluminosilicate ceramic materials. The main reason for this effect is due to densely dispersed corundum and mullite fine crystals in glassy matrix.

Słowa kluczowe:

porcelain material C 130 type, acoustic emission, compressive strength, structural degradation

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The paper presents the investigations of the relation between the acoustic emission (AE) and the Porte vin-Le Chatelier (PL) phenomena occurring in tensile tested two kinds of aluminium alloys: not-predeformed and predeformed earlier using the technique of accumulative rolling banding (ARB). There have been found essential correlations between AE and PL effects in ARB not-predeformed alloys. The tensile tests for ARB predeformed alloys were performed on a series of samples of various degree of work hardening and it has been observed that the correlations between the AE and PL effects are not so pronounced as in the case of ARB not-predeformed alloys. The results of AE measurements obtained using a new software allowed additionally to carry out the spectral analysis of AE signals and, in consequence, to determine the acoustic maps (acoustograms) and the spectral characteristics which are very useful in the discussion of the relations between the non-homogeneous strain mechanisms of the PL effect and the mechanisms of AE events generation. The results are discussed in the context of the existing dislocation models of the PL effect and the theoretical concepts of AE sources

Słowa kluczowe:

acoustic emission (AE), Portevin-Le Chatelier (PL) effect, tensile test, dislocations, strain mechanism, nanocrystalline and/or ultra fine-grained structure, accumulative rollbonding (ARB)

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Streszczenie:

The paper presents the results of acoustic wave velocity investigation in metallic Ag/Fe nanolayers deposited on GaAs substrate. Measurements of velocity were performed using femtosecond technique. Ag/Fe samples were characterized by different thickness of bilayers. On the basis of experimental results of velocities, effective elastic constants c11 were evaluated. In the range of bilayers thickness above 80 Å the c11 values are in accordance with those calculated from the elastic constants of bulk materials (Rytov model). For lower values of bilayer thickness elastic constants exhibit large decrease. Grimsditch’s model was applied to interpret changes of elastic constants dependence for low bilayer thickness. This model contains an additional interlayer treated as the parameter. Comparison the values of theoretical elastic constants obtained by applying of Grimsditch model with those calculated from experiment shows qualitative accordance in the range of small bilayer thickness.

Słowa kluczowe:

metallic nanolayers, effective elastic constants nanolayers

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Paper presents the results of study of picosecond acoustic signals generated by femtosecond laser pump pulse in Au/V multilayers. Au/V nanostructures with a period of 36-205Å located on MgO substrate were studied. The dependence of measured changes of the laser light reflectivity from nanostructure surface on different delays of probe beam was examined. Peak frequencies obtained by FFT analysis were interpreted as frequencies of acoustical localized modes. The obtained values of these localized modes are in agreement with numerical results. In the same sample localized modes were excited simultaneously in the first and second frequency forbidden gaps.

Słowa kluczowe:

picosecond acoustics, metallic nanolayers, FFT analysis

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Streszczenie:

In this work a structure of a ultrasonic chemical sensor with organic monomolecular layer as well as introductory measurement with the help of a set-up constructed in IFTR PAS are presented. Chemical composition of this layer is an equimolar mixture of 5-[[1,3-dioxo-3- [4-(1-oxooctadecyl) phenyl] propyl] amino] – 1,3 – benzenedicarboxylic acid (DA) and cetylamine (CA). The thickness of this layer is equal to dimension of one molecule. The sensor layer was deposited on one channel of the bi-channel sensor delay line (made from lithium niobiate) by means of the Langmuir–Blodgett method. The chemical sensitivity of this sensor to some mixtures of air with vapor of volatile organic compounds has been investigated

Słowa kluczowe:

ultrasonic chemical sensor, Langmuir–Blodgett layers, air-organic vapor mixtures, volatile organic compounds

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Ultrasonic, microscopic and acoustic emission (AE) methods were applied to investigate the microstructure of composite rods, used as a carrying element of the medium voltage insulators. Such features of material structure as homogeneity level and the appearance of defects were discussed. The research was aimed at determining the influence of the technology of epoxy-glass fabrication on quality parameters of the insulator rods. The results of acoustic testing were compared with the effects of microscopic investigation.

Słowa kluczowe:

composite insulator, epoxy-glass material, nondestructive ultrasonic measurements, acoustic emission

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Streszczenie:

Formulae describing the effective elastic moduli of a porous ceramic medium are derived using Eshelby's solution and Maxwell's approximation. The ceramic medium is considered as an infinite matrix, which has uniform elastic properties and encloses non-spherical pores. A numerical evaluation of the velocity of an ultrasonic wave in the ceramic, as function of the porosity and pore shape, is presented. The theoretical results were combined with those obtained experimentally for different firing temperatures of the ceramic.

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In the presented work the new method of the analysis of particle distribution in the emulsion according to the sizes with the increased resolution by means of the scattering of light is considered. A significant increase in the possibilities of the proposed method is achieved due to the additional introduction into the emulsion of physically powerful ultrasonic flow and make use of the frequency-phase method of detection. Fundamental special features of procedure and some technical questions are discussed.

Słowa kluczowe:

light scattering, ultrasonic field, Doppler effect, emulsion, distribution of particles, frequency-phase detector

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Streszczenie:

This work presents analysis of localized acoustic modes using theory given by B. Djafari-Rouchani et al. and Rytov model of elastic waves propagation in periodical medium. Localized modes were considered for Au/V nanostructures. Experimentally Au/V nanostructures on MgO substrate with period 120-240 angstrom were studied. Changes of light reflectivity coefficient of these nanostructures caused by femtosecond laser beam excitation were measured. Analysis of experimental results of reflectivity dependence on delay time of probe beam was made over the range up to 150 ps. The dependences of localized modes frequency on thickness of nanostructure bilayers were obtained. Measured frequencies of localized modes remain in agreement to the theoretical values.

Słowa kluczowe:

metallic nanolayers, picosecond acoustics, localized modes, Rytov model

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