Partner: Andrzej Pawełek


Recent publications
1.Pawełek A., Ozgowicz W., Ranachowski Z., Kúdela S., Piątkowski A., Kúdela Jr S., Ranachowski P., Behaviour of Acoustic Emission in Deformation and Microcracking Processes of Mg Alloys Matrix Composites Subjected to Compression Tests, ARCHIVES OF CURRENT RESEARCH INTERNATIONAL, ISSN: 2454-7077, DOI: 10.9734/ACRI/2017/34598, Vol.8, No.2, pp.1-13, 2017
Abstract:

Research results on both mechanical and acoustic emission (AE) behavior of Mg-Li and Mg-Al alloys matrix composites (AMC) reinforced with ceramic δ-Al2O3 or carbon fibers subjected to the channel-die compression at room and elevated temperatures are presented in this paper. The AE measurements at room temperature showed that, the effect of anisotropy of the fibres distribution (random planar distribution) with respect to the compression axis appeared in the most investigated composites, whereas the AE activity at 140°C revealed a two- range character and the rate of AE events at 140°C was higher than at room temperature. These effects are discussed in terms of both the differences in thermal expansion between the fibres and the matrix as well as the weakening of the coherency between the fibres and the matrix leading to stronger debonding effects at 140°C than at room temperature. The spectral analysis of AE signals was performed with the Windowed Fourier Transform method, which served to plot the spectral density of AE signal as a function of frequency. The alominous and corundum ceramics types were also investigated in order to illustrate the enhanced AE, which was related to the different crack paths in the final stages of the sample degradation. The results were also discussed on the basis of SEM images, including the in-situ observations of microcracking as well as the dislocation strain mechanisms and microcracking ones during the channel-die compression of the Mg-Li-Al AMC.

Keywords:

composites, fibres microcracking, acoustic emission, strain mechanisms, dislocations

Affiliations:
Pawełek A.-other affiliation
Ozgowicz W.-other affiliation
Ranachowski Z.-IPPT PAN
Kúdela S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Piątkowski A.-Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
Kúdela Jr S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Ranachowski P.-IPPT PAN
2.Ozgowicz W., Grzegorczyk B., Pawełek A., Wajda W., Skuza W., Piątkowski A., Ranachowski Z., An analysis of the Portevin- Le Chatelier effect and cracking of CuSn6P alloy at elevated temperature of deformation applying the acoustic emission method, ENGINEERING FRACTURE MECHANICS, ISSN: 0013-7944, DOI: 10.1016/j.engfracmech.2016.04.036, Vol.167, pp.112-122, 2016
Abstract:

The paper concerns the application of the acoustic emission (AE) method for the determination of the mechanical properties of continuously cast industrial tin bronze CuSn6P, which reveals tendencies to unstable plastic flow connected particularly with the Portevin–Le Chatelier (PLC) effect. The relations between the jerky flow connected with the PLC effect, AE intensity and the evolution of a fracture of the investigated alloy subjected to the tensile and compression tests have been analyzed. It has been found that the intensity of the oscillation of stresses, observed on the curves σ–ε, coincides with the effect of the instability of plastic deformation PLC type and the recorded signals of the intensity of acoustic emissions. It has also been found that the increase of the tensile temperature in the investigated alloy involves changes in the mechanism of cracking from transcrystalline ductile to brittle intercrystalline, characteristic at the temperature of minimum plasticity (DMT).

Keywords:

Copper alloy, Portevin–Le Chatelier phenomenon, Fractography, Acoustic emission, Intercrystalline fracture

Affiliations:
Ozgowicz W.-other affiliation
Grzegorczyk B.-other affiliation
Pawełek A.-other affiliation
Wajda W.-other affiliation
Skuza W.-other affiliation
Piątkowski A.-Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
Ranachowski Z.-IPPT PAN
3.Pawełek A., Piątkowski A., Wajda W., Skuza W., Tarasek A., Ranachowski Z., Ranachowski P., Ozgowicz W., Kúdela Jr S., Kúdela S., Plastic instabilities induced by the Portevin - Le Châtelier effect and fracture character of deformed Mg-Li alloys investigated using the acoustic emission method, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.1515/amm-2016-0152, Vol.61, No.2, pp.897-904, 2016
Abstract:

The results of the investigation of both mechanical and acoustic emission (AE) behaviors of Mg4Li5Al and Mg4Li4Zn alloys subjected to compression and tensile tests at room temperature are compared with the test results obtained using the same alloys and loading scheme but at elevated temperatures. The main aim of the paper is to investigate, to determine and to explain the relation between plastic flow instabilities and the fracture characteristics. There are discussed the possible influence of the factors related with enhanced internal stresses such as: segregation of precipitates along grain boundaries, interaction of solute atoms with mobile dislocations (Cottrell atmospheres) as well as dislocation pile-ups which may lead to the microcracks formation due to the creation of very high stress concentration at grain boundaries. The results show that the plastic flow discontinuities are related to the Portevin-Le Châtelier phenomenon (PL effect) and they are correlated with the generation of characteristic AE pulse trains. The fractography of broken samples was analyzed on the basis of light (optical), TEM and SEM images.

Keywords:

lightweight alloys, Acoustic Emission, fracture, Portevin-Le Châtelier phenomenon, twinning, dislocations, shear bands

Affiliations:
Pawełek A.-other affiliation
Piątkowski A.-Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
Wajda W.-other affiliation
Skuza W.-other affiliation
Tarasek A.-other affiliation
Ranachowski Z.-IPPT PAN
Ranachowski P.-IPPT PAN
Ozgowicz W.-other affiliation
Kúdela Jr S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Kúdela S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
4.Ranachowski P., Ranachowski Z., Kúdela Jr S., Pawełek A., Piątkowski A., Study of factors determinant of siliceous electrical porcelain resistance to structural degradation, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.1515/amm-2016-0244, Vol.61, No.3, pp.1143-1150, 2016
Abstract:

The subject of this study was investigation of the factors that have a decisive influence on the resistance of siliceous porcelain to degradation processes. There was tested material C 110 type, which is widely used for the production of low-voltage (LV) elements such as insulators and bushings. On the basis of mechanical-acoustic and microscopic research of small-sized samples, which were subjected to compression, there were distinguished successive stages of degradation of the material structure. In the authors’ opinion, they have a reference to the ageing process, taking place during many years of work under operating conditions. Thus, it was possible to assess the structural factors that determine the durability and reliability of LV electroinsulating elements. The results were related to electrical aluminous porcelains.

Keywords:

porcelain insulating materials, ageing processes, acoustic emission (AE), optical microscopy

Affiliations:
Ranachowski P.-IPPT PAN
Ranachowski Z.-IPPT PAN
Kúdela Jr S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Pawełek A.-other affiliation
Piątkowski A.-Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
5.Ozgowicz W., Grzegorczyk B., Pawełek A., Wajda W., Skuza W., Piątkowski A., Ranachowski Z., Relation between the plastic instability and fracture of tensile tested Cu-Sn alloys investigated with the application of acoustic emission technique, Frattura ed Integrità Strutturale, ISSN: 1971-8993, DOI: 10.3221/IGF-ESIS.35.02, Vol.35, pp.1-10, 2016
Abstract:

The work concerns the application of the acoustic emission (AE) method in testing the mechanical properties of continuously cast industrial tin bronze CuSn6P, which reveals tendencies to instable plastic flow connected particularly with the Portevin-Le Chatelier (PLC) effect. The relations between the jerky flow connected with the PLC effect, AE intensity and the evolution of a fracture of the investigated alloy subjected to the tensile test at a strain rate (?? ) of about 1.2·10-3s-1 in the range of temperatures (20÷400?C) has been analyzed. It has been found that the highest intensity of the oscillation of stresses, corresponding to the instability of plastic deformation PLC occurred at 200?C, whereas the maximum of the AE activity is at about 200÷250?C. The brittle intergranular fracture starts in the range of equicohersive temperature (TE) of about 200?C. Plastic deformation of the investigated alloy in the range of the temperature of minimum plasticity, amounting to about 400?C, results in intercrystalline fractures on the entire surface of the stretched samples.

Affiliations:
Ozgowicz W.-other affiliation
Grzegorczyk B.-other affiliation
Pawełek A.-other affiliation
Wajda W.-other affiliation
Skuza W.-other affiliation
Piątkowski A.-Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
Ranachowski Z.-IPPT PAN
6.Pawełek A., Piątkowski A., Wajda W., Skuza W., Tarasek A., Ozgowicz W., Grzegorczyk B., Ranachowski Z., Kúdela S., Kúdela Jr S., Mechanisms of plastic instability and fracture of compressed and tensile tested Mg-Li alloys investigated using the acoustic emission method, Frattura ed Integrità Strutturale, ISSN: 1971-8993, DOI: 10.3221/IGF-ESIS.35.03, Vol.35, pp.11-20, 2016
Abstract:

The results of the investigation of both mechanical and acoustic emission (AE) behaviors of Mg4Li5Al alloy subjected to compression and tensile tests at room temperature are compared with the test results obtained using the same alloy and loading scheme but at elevated temperatures. The main aim of the paper is to investigate, to determine and to explain the possible influence of factors related with enhanced internal stresses such as: segregation of precipitates along grain boundaries or solute atoms along dislocations (Cottrell atmospheres) or dislocation pile-ups at grain boundaries which create very high stress concentration leading to fracture. The results show that the plastic instabilities are related to the Portevin–Le Châtelier phenomenon (PL effect) and they are correlated with the generation of AE peaks. The fractography of breaking samples was analyzed on the basis of light (optical), TEM and SEM images.

Affiliations:
Pawełek A.-other affiliation
Piątkowski A.-Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
Wajda W.-other affiliation
Skuza W.-other affiliation
Tarasek A.-other affiliation
Ozgowicz W.-other affiliation
Grzegorczyk B.-other affiliation
Ranachowski Z.-IPPT PAN
Kúdela S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Kúdela Jr S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
7.Ozgowicz W., Grzegorczyk B., Pawełek A., Piątkowski A., Ranachowski Z., Influence of the strain rate on the plc effect and acoustic emission in single crystals of the CuZn30 alloy compressed at an elevated temperature, Materials and Technology, ISSN: 1580-2949, DOI: 10.17222/mit.2013.195, Vol.49, No.2, pp.197-202, 2015
Abstract:

The purpose of these investigations was to determine the effect of the strain rate on the phenomenon of a heterogeneous plastic deformation of the Portevin–Le Chatelier type while testing free compression of CuZn30 single crystals with a crystallographic orientation of [139] at 300°C. Moreover, the relations between the work-hardening curve s–e displaying the PLC effect and the characteristics of the signals of the acoustic emission generated in the uniaxial-compression test were determined. It was found that the process of plastic deformation of the tested single crystals in the analyzed range of the frequencies up to 35 kHz generates differentiated sources of acoustic-energy emission, mainly the impulsive emission generated by signal events, correlated with the oscillations of the stresses on the work-hardening curves s–e. The strain rate mainly causes the changes in the intensity of the oscillation typical for the PLC effect.

Keywords:

plastic strain, Portevin–Le Chatelier effect (PLC), single crystals, copper alloys, compression test, acoustic emission (AE)

Affiliations:
Ozgowicz W.-other affiliation
Grzegorczyk B.-other affiliation
Pawełek A.-other affiliation
Piątkowski A.-Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
Ranachowski Z.-IPPT PAN
8.Ozgowicz W., Grzegorczyk B., Pawełek A., Piątkowski A., Ranachowski Z., The Portevin – le Chatelier effect and acoustic emission of plastic deformation CuZn30 monocrystals, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.2478/amm-2014-0029, Vol.59, No.1, pp.183-188, 2014
Abstract:

The paper presents the investigation of the relation between the acoustic emission (AE) and instability of plastic deformation type Portevin-Le Chatelier (PLC) of single-phase brass CuZn30 monocrystals with crystallographical orientation [1¯3 9]. The monocrystals have been investigated applying the method of free compression at a constant strain rate and the temperature within the range from 200°C to 400°C, simultaneously recording PLC phenomenon by means of acoustic emission. During hot axial compression tests the correlation between work-hardening curves σ - ε, which display PLC effect and characteristic of acoustic emission signals has been found. Moreover, it was proved that in the range of the PLC effect, the acoustic signal is an impulse a character of cyclic repeatability, distinctly correlated qualitatively with the stress oscillations on the curves σ - ε. The analysis of the obtained results leads to the conclusion that in the tested monocrystals the effect PLC is probably controlled by complex processes similar to the phenomenon of dynamic strain ageing (DSA), which are described by diffusion models.

Keywords:

plastic strain, Portevin - Le Chatelier effect (PLC), monocrystals, copper alloys, compression test, acoustic emission (AE)

Affiliations:
Ozgowicz W.-other affiliation
Grzegorczyk B.-other affiliation
Pawełek A.-other affiliation
Piątkowski A.-Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
Ranachowski Z.-IPPT PAN
9.Ranachowski P., Rejmund F., Ranachowski Z., Pawełek A., Piątkowski A., Kúdela Jr S., Influence of microstructure on the properties of siliceous electrical porcelain, PRZEGLĄD ELEKTROTECHNICZNY, ISSN: 0033-2097, DOI: 10.12915/pe.2014.10.28, Vol.90, No.10, pp.110-113, 2014
Abstract:

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.

Keywords:

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

Affiliations:
Ranachowski P.-IPPT PAN
Rejmund F.-IPPT PAN
Ranachowski Z.-IPPT PAN
Pawełek A.-other affiliation
Piątkowski A.-Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
Kúdela Jr S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
10.Ranachowski Z., Pawełek A., Drzymała P., Bonarski J., Lewandowski M., Ozgowicz W., Light alloys for application as engine parts – comparison of properties of three materials, ZESZYTY NAUKOWE / AKADEMIA MORSKA W SZCZECINIE, ISSN: 1733-8670, Vol.39, No.111, pp.128-132, 2014
Abstract:

This paper discusses the mechanical properties, microstructure and crystallographic texture of light alloys made on the base of aluminium, magnesium and lithium. An acoustic emission (AE) technique was applied to detect the moment of twinning or slip activation during compression and channel – die tests to extend the comprehension on the nature of the plastic deformation processes occurring in the investigated alloy s

Keywords:

hcp metals, aluminium and magnesium alloys, plastic deformation, mechanical twinning, crystallographic texture, acoustic emission

Affiliations:
Ranachowski Z.-IPPT PAN
Pawełek A.-other affiliation
Drzymała P.-Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
Bonarski J.-Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
Lewandowski M.-IPPT PAN
Ozgowicz W.-other affiliation
11.Ranachowski P., Rejmund F., Ranachowski Z., Pawełek A., Piątkowski A., Kúdela Jr S., Evaluation of the mullite hypothesis in respect of electrotechnical porcelains, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.2478/amm-2013-0158, Vol.58, No.4, pp.1177-1181, 2013
Abstract:

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.

Keywords:

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

Affiliations:
Ranachowski P.-IPPT PAN
Rejmund F.-IPPT PAN
Ranachowski Z.-IPPT PAN
Pawełek A.-other affiliation
Piątkowski A.-Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
Kúdela Jr S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
12.Ranachowski Z., Pawełek A., Jasieński Z., Piątkowski A., Kúdela Jr S., Lewandowski M., Mazuruk P., Durability and wear of engine parts – new methods of testing of alloys and composites, ZESZYTY NAUKOWE / AKADEMIA MORSKA W SZCZECINIE, ISSN: 1733-8670, Vol.35, No.107, pp.125-131, 2013
Abstract:

The paper deals with the problems related to the diagnostics of selected parts of modern Diesel engines. The evolution of mechanical properties of four alloys of Mg-Li-Al system and four composites made on the base of the alloys mentioned above, caused by variation of its composition was presented. The Acoustic Emission (AE) method applied to monitoring of degradation of mechanical properties of the alloys and composites was described. Moreover, the results of the investigation of failures occurring in the injectors of Common Rail Diesel engines per formed with the application of AE method were also reported.

Keywords:

Diesel engines diagnostics, light alloys and composites, Common Rail fuel system, Acoustic Emission method

Affiliations:
Ranachowski Z.-IPPT PAN
Pawełek A.-other affiliation
Jasieński Z.-other affiliation
Piątkowski A.-Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
Kúdela Jr S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Lewandowski M.-IPPT PAN
Mazuruk P.-other affiliation
13.Ranachowski P., Rejmund F., Ranachowski Z., Pawełek A., Piątkowski A., Kúdela Jr S., Rola fazy mulitowej w podwyższeniu odporności elektroporcelan na procesy starzeniowe, PRZEGLĄD ELEKTROTECHNICZNY, ISSN: 0033-2097, Vol.88, No.11b, pp.162-165, 2012
Abstract:

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.

Keywords:

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

Affiliations:
Ranachowski P.-IPPT PAN
Rejmund F.-IPPT PAN
Ranachowski Z.-IPPT PAN
Pawełek A.-other affiliation
Piątkowski A.-Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
Kúdela Jr S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
14.Kúdela S., Pawełek A., Ranachowski Z., Piątkowski A., Kúdela Jr S., Ranachowski P., Effect of Al alloying on the Hall-Petch strengthening and AE in compressed Mg-Li-Al alloys before and after HPT processing, KOVOVE MATERIALY-METALLIC MATERIALS, ISSN: 0023-432X, DOI: 10.4149/km_2011_4_271, Vol.49, No.4, pp.271-277, 2011
Abstract:

The paper deals with the effect of Al content in two-phase Mg-10Li-xAl (x = 0, 1, 5) alloys on their straining behavior before and after severe plastic deformation by high pressure torsion. Both coarse-grained and ultrafine-grained alloys were compression strained in channel-die device with simultaneous acoustic emission monitoring. It has been observed that Hall-Petch strengthening in ultra-fine grained alloys superposes with the strengthening resulting from Al alloying (solution hardening, particulate strengthening). Superposition of these strengthening mechanisms becomes stronger with increase in Al content, presumably due to enhanced grain refining effect.

Keywords:

Mg-Li-Al alloys, grain refinement, high pressure torsion, acoustic emission, Hall-Petch strengthening

Affiliations:
Kúdela S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Pawełek A.-other affiliation
Ranachowski Z.-IPPT PAN
Piątkowski A.-Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
Kúdela Jr S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Ranachowski P.-IPPT PAN
15.Ranachowski P., Rejmund F., Ranachowski Z., Pawełek A., Piątkowski A., Mechanoacoustic and microscopic study of aluminous porcelain resistance to structural degradation, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.2478/v10172-011-0140-7, Vol.56, No.4, pp.1227-1233, 2011
Abstract:

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.

Keywords:

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

Affiliations:
Ranachowski P.-IPPT PAN
Rejmund F.-IPPT PAN
Ranachowski Z.-IPPT PAN
Pawełek A.-other affiliation
Piątkowski A.-Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
16.Ranachowski P., Rejmund F., Ranachowski Z., Pawełek A., Piątkowski A., Aluminous porcelain degradation study using mechanoacoustic and microscopic methods, ARCHIVES OF ELECTRICAL ENGINEERING, ISSN: 0004-0746, DOI: 10.2478/v10171-011-0011-x, Vol.60, No.2, pp.109-128, 2011
Abstract:

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.

Keywords:

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

Affiliations:
Ranachowski P.-IPPT PAN
Rejmund F.-IPPT PAN
Ranachowski Z.-IPPT PAN
Pawełek A.-other affiliation
Piątkowski A.-Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
17.Ranachowski P., Rejmund F., Ranachowski Z., Pawełek A., Piątkowski A., Foundations of mechanoacoustic method of material degradation research, PRZEGLĄD ELEKTROTECHNICZNY, ISSN: 0033-2097, Vol.R 86, No.5, pp.186-198, 2010
Abstract:

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.

Keywords:

acoustic emission (AE), material degradation, electrotechnical ceramics

Affiliations:
Ranachowski P.-IPPT PAN
Rejmund F.-IPPT PAN
Ranachowski Z.-IPPT PAN
Pawełek A.-other affiliation
Piątkowski A.-Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
18.Ranachowski P., Rejmund F., Ranachowski Z., Pawełek A., Piątkowski A., Experimental evaluation of resistance to degradation of modern C 120 type porcelain, PRZEGLĄD ELEKTROTECHNICZNY, ISSN: 0033-2097, Vol.86, No.11b, pp.126-129, 2010
19.Pawełek A., Kúdela S., Piątkowski A., Jasieński Z., Ranachowski Z., Kúdela Jr S., Mechanical and acoustic emission behavior in channel-die compressed Mg9Li alloys before and after treatment by HPT method, INŻYNIERIA MATERIAŁOWA, ISSN: 0208-6247, Vol.3, pp.579-581, 2010
20.Jasieński Z., Pawełek A., Piątkowski A., Ranachowski Z., Twinning and shear band formation in channel - die compressed silver single crystals identified by acoustic emission method, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, Vol.54, No.1, pp.29-33, 2009
21.Pawełek A., Kuśnierz J., Jasieński Z., Ranachowski Z., Bogucka J., Acoustic emission and the Portevin - Le Chatelier effect in tensile tested Al. alloys before and after processing by accumulative roll-bonding (ARB) technique, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, Vol.54, No.1, pp.83-88, 2009
22.Ranachowski P., Rejmund F., Ranachowski Z., Pawełek A., Piątkowski A., Kúdela Jr S., Materials degradation research on the basis of mechanoacoustic and microscopic methods, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, Vol.54, No.4, pp.824-832, 2009
23.Ranachowski P., Rejmund F., Ranachowski Z., Pawełek A., Piątkowski A., Comparison of acoustic emission and structure degradation in compressed porcelain and corundum materials, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, Vol.34, No.4, pp.705-722, 2009
24.Ranachowski P., Rejmund F., Pawełek A., Piątkowski A., Structure degradation, texture and acoustic emission in compressed corundum ceramics, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, Vol.53, No.3, pp.703-709, 2008
25.Ranachowski P., Rejmund F., Pawełek A., Piątkowski A., Mechanical-acoustic study of degradation processes of ceramic structure illustrated by corundum material, PRZEGLĄD ELEKTROTECHNICZNY, ISSN: 0033-2097, Vol.84, No.10, pp.252-255, 2008
26.Ranachowski P., Rejmund F., Ranachowski Z., Pawełek A., Piątkowski A., Research of degradation processes of insulator porcelain C 130 type, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, Vol.32, No.4S, pp.117-122, 2008
Abstract:

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.

Keywords:

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

Affiliations:
Ranachowski P.-IPPT PAN
Rejmund F.-IPPT PAN
Ranachowski Z.-IPPT PAN
Pawełek A.-other affiliation
Piątkowski A.-Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
27.Ranachowski Z., Ranachowski P., Rejmund F., Pawełek A., Piątkowski A., Jasieński Z., The study of influence of high pressure torsion process on acoustic emission activity of compressed Mg - Li alloys, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, Vol.32, No.4S, pp.123-128, 2008
28.Pawełek A., Ranachowski Z., Piątkowski A., Kúdela S., Jasieński Z., Kúdela Jr S., Acoustic emission and strain mechanisms during compression at elevated temperature of b phase containing Mg-Li-Al composites reinforced with ceramic fibres, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, Vol.52, No.1, pp.41-48, 2007
29.Ranachowski P., Rejmund F., Pawełek A., Piątkowski A., Mechanical- acoustic and structural investigations of degradation processes of aluminous insulator porcelain C 130 type, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, Vol.52, No.4, pp.551-564, 2007
30.Pawełek A., Piątkowski A., Kuśnierz J., Bogucka J., Jasieński Z., Ranachowski Z., Ranachowski P., Mizera J., Kúdela S., Kúdela Jr S., Acoustic emission in compressed Mg - Li and Al. alloys processed by ECAP, HPT and ARB methods, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, Vol.32, No.4, pp.88-94, 2007
31.Pawełek A., Kuśnierz J., Bogucka J., Jasieński Z., Ranachowski Z., Ranachowski P., Rejmund F., Dębowski T., Acoustic emission and the Portevin-Le Chatelier effect in tensile tested Al processed by ARB technique, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, Vol.32, No.4, pp.955-962, 2007
Abstract:

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

Keywords:

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

Affiliations:
Pawełek A.-other affiliation
Kuśnierz J.-other affiliation
Bogucka J.-other affiliation
Jasieński Z.-other affiliation
Ranachowski Z.-IPPT PAN
Ranachowski P.-IPPT PAN
Rejmund F.-IPPT PAN
Dębowski T.-IPPT PAN
32.Ranachowski P., Rejmund F., Pawełek A., Piątkowski A., Acoustic - mechanical and microscopic investigation of corundum material, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, Vol.32, No.4, pp.963-970, 2007
33.Ranachowski P., Rejmund F., Pawełek A., Piątkowski A., Study of degradation processes in corundum material using acoustic and microscopic methods, PRACE KOMISJI NAUK CERAMICZNYCH - POLSKI BIULETYN CERAMICZNY. CERAMIKA, ISSN: 0860-3340, Vol.101, pp.265-274, 2007
34.Pawełek A., Kuśnierz J., Ranachowski Z., Jasieński Z., Anisotropy of acoustic emission and-Portevin-Le Chatelier phenomena in polycrystalline aluminium alloys subjected to tensile tests, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, Vol.31, No.4, pp.75-81, 2006
35.Ranachowski P., Rejmund F., Pawełek A., Piątkowski A., Investigation of influence of defectiveness in aluminous porcelain structure on fracture process under compressive loading using Acoustic Emission Method, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, Vol.31, No.4, pp.83-90, 2006
36.Ranachowski Z., Piątkowski A., Pawełek A., Jasieński Z., Spectral analysis of acoustic emission signals generated by twinning and shear band formation in silver single crystals subjected to channel-die compression tests, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, Vol.31, No.4, pp.91-97, 2006
37.Ranachowski Z., Pawełek A., Piątkowski A., Wavelet analysis of acoustic emission signals from composites based on Mg8Li5Al and Mg12Li3Al alloys subjected to compression tests, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, Vol.30, pp.29-32, 2005
38.Ranachowski P., Rejmund F., Pawełek A., Piątkowski A., Badania tworzywa kordierytowego przy naprężeniach ściskających w różnych temperaturach oraz po szoku termicznym, PRACE KOMISJI NAUK CERAMICZNYCH - POLSKI BIULETYN CERAMICZNY. CERAMIKA, ISSN: 0860-3340, Vol.89, pp.101-115, 2005
39.Pawełek A., Malecki I., Emisja akustyczna a plastyczność kryształów, Prace IPPT - IFTR Reports, ISSN: 2299-3657, No.22, pp.1-63, 1993

Conference papers
1.Ozgowicz W., Grzegorczyk B., Pawełek A., Piątkowski A., Ranachowski Z., Acoustic Emission and the PLC Effect in Compressed CuZn Monocrystals, 58th Open Seminar on Acoustics joined with 2nd Polish-German Structured Conference on Acoustics, 2011-09-13/09-16, Jurata (PL), Vol.2, pp.159-168, 2011
2.Pawełek A., Kúdela S., Piątkowski A., Jasieński Z., Ranachowski Z., Kúdela Jr S., Ranachowski P., Microcracking of ceramic fibres and acoustic emission in channel-die compressed mg-Li-Al alloys matrix composites, ICSV17, 17th International Congress on Sound and Vibration, 2010-07-18/07-22, Cairo (EG), pp.47-1-8, 2010
Abstract:

The object of investigation was the behaviour of acoustic emission (AE) during channel-die compression of the Mg-Li-Al alloys matrix composites (AMC) reinforced with ceramic δ-Al2O3fibres at room and at elevated temperature. The results of AE measurements at room temperature showed that in the majority of the investigated compositions the effect of anisotropy of the fibres distribution (planar random distribution) appeared with respect to the compression axis, whereas the AE activity at 1400C revealed a two-range character and the level of the rate of AE events was higher than thatat room temperature. These effects are discussed in terms of both, the differences in thermal expansion as well as weakening of the coherency between the fibres and the matrix. The results of AE measurements served to plot the spectral characteristics of the registered AE signals, i.e. the spectral density of AE signal as a function of its frequency. The spectral analysis of AE signals generated during the micro-cracking process of ceramic fibres in channel-die compressed Mg-Li-Al AMC was performed with the Windowed Fourier Transform method. The results are also discussed on the basis of optical and scanning microstructure images including these in-situobservations of microcracking fibres as well as in the context of the dislocation strain mechanisms and microcracking ones during the channel-die compression of the Mg-Li-Al AMC.

Affiliations:
Pawełek A.-other affiliation
Kúdela S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Piątkowski A.-Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
Jasieński Z.-other affiliation
Ranachowski Z.-IPPT PAN
Kúdela Jr S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Ranachowski P.-IPPT PAN
3.Ranachowski P., Rejmund F., Ranachowski Z., Pawełek A., Piątkowski A., Mechanoacoustic study of ceramic electrotechnical material, 56th Open Seminar on Acoustics, 2009-09-15/09-18, Goniądz nad Biebrzą (PL), pp.99-104, 2009
4.Ranachowski P., Rejmund F., Ranachowski Z., Pawełek A., Piątkowski A., Mechanoacoustic study of ceramic electrotechnical material, 56th Open Seminar on Acoustics, 2009-09-15/09-18, Goniądz nad Biebrzą (PL), pp.99-104, 2009

Conference abstracts
1.Ranachowski Z., Jóźwiak-Niedźwiedzka D., Ranachowski P., Pawełek A., Kúdela Jr S., Dvorak T., The analysis of pore distribution and pore connectivity in concrete samples using x-ray microtomography, SolMech 2014, 39th Solid Mechanics Conference, 2014-09-01/09-05, Zakopane (PL), pp.199-200, 2014
Abstract:

The durability of concrete in outdoor structures is closely related to its resistance against the aggressive gaseous actions coming from the environment and including influence of oxygen, nitrogen, carbon dioxide. The pore system and its interconnectivity in the concrete matrix directly influence the possibility of penetration of various aggressive gaseous media into concrete structure. The X-ray microtomography (micro-CT) is a modern, non-invasive technique enabling for determination of existing pores in the microstructure of concrete matrix. In the paper the results of investigation of two different concretes by the application of micro-CT method to micro-cores are presented. The quantitative information on the parameters of the analysed microstructure can improve the methods of material characterization available up to now.

Keywords:

X-ray microtomography, concrete, microstructure

Affiliations:
Ranachowski Z.-IPPT PAN
Jóźwiak-Niedźwiedzka D.-IPPT PAN
Ranachowski P.-IPPT PAN
Pawełek A.-other affiliation
Kúdela Jr S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Dvorak T.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)