Partner: Stanislav Kúdela Jr

Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)

Recent publications
1.Żołek N., Ranachowski Z., Ranachowski P., Jóźwiak-Niedźwiedzka D., Kúdela Jr S., Dvorak T., Statistical assessment of the microstructure of barite aggregate from different deposits using x-ray microtomography and optical microscopy, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.1515/amm-2017-0104, Vol.62, No.2, pp.697-702, 2017
Abstract:

Two different barite ore (barium sulfate BaSO4) specimens from different localizations were tested and described in this paper. Analysis of the microstructure was performed on polished sections, and on thin sections using X-ray microtomography (micro-CT), and optical microscopy (MO). Microtomography allowed obtaining three-dimensional images of the barite aggregate specimens. In the tomograms, the spatial distribution of the other polluting phases, empty space as well as cracks, pores, and voids – that exceeded ten micrometers of diameter-were possible to visualize. Also, the micro-CT allowed distinguishing between minerals of different density, like SiO2 and BaSO4. Images obtained and analyzed on thin sections with various methods using the optical microscopy in transmitted light delivered additional information on the aggregate microstructure, i.e. allow for estimation of the different kinds of inclusions (like the different density of the minerals) in the investigated specimens. Above methods, which were used in the tests, completed each another in order to supply a set of information on inclusions’ distribution and to present the important differences of the barite aggregate specimens microstructure.

Keywords:

barite ore, barite aggregate, microstructure, optical microscopy, thin sections analysis, X-ray tomography

Affiliations:
Żołek N.-IPPT PAN
Ranachowski Z.-IPPT PAN
Ranachowski P.-IPPT PAN
Jóźwiak-Niedźwiedzka D.-IPPT PAN
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)
2.Kúdela Jr S., Švec P., Bajana O., Orovčík L., Ranachowski P., Ranachowski Z., Saffil alumina fibers reinforced dual-phase Mg-Li and Mg-Li-Zn alloys, KOVOVE MATERIALY-METALLIC MATERIALS, ISSN: 0023-432X, DOI: 10.4149/km_2017_3_195, Vol.55, pp.195-203, 2017
Abstract:

The gas pressure infiltration technique was used to prepare Saffil alumina fibers reinforced Mg-Li and Mg-Li-Zn matrix composites with a dual-phase matrix structure. There was investigated the effect of variable Li content (6.2–10.3 wt.% Li) and Zn alloying (∼ 1.5 wt.% Zn) on the proof stress Rp0.2 of prepared composites. Rp0.2 values increased monotonously with rising fraction of Saffil fibers (5, 10 and 15 vol.%) reaching the maximum of about 250 MPa for Mg-Li matrix composites. Rp0.2 values of Mg-Li-Zn matrix composites were lower. Strengthening effect of Saffil fibers was promoted by the displacement redox reaction with Mg-Li and Mg-Li-Zn melts in which only Li significantly participated. Zn alloying retarded the displacement redox reaction. Too extensive reaction, however, resulted in the fiber damage and the drop in composite strength.

Keywords:

Mg-Li alloys, Saffil fibers, metal matrix composites, short-fiber strengthening, reactive wetting, displacement reactions

Affiliations:
Kúdela Jr S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Švec P.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Bajana O.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Orovčík L.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Ranachowski P.-IPPT PAN
Ranachowski Z.-IPPT PAN
3.Schabowicz K., Ranachowski Z., Jóźwiak-Niedźwiedzka D., Radzik Ł., Kúdela Jr S., Dvorak T., Application of X-ray microtomography to quality assessment of fibre cement boards, CONSTRUCTION AND BUILDING MATERIALS, ISSN: 0950-0618, DOI: 10.1016/j.conbuildmat.2016.02.035, Vol.110, pp.182-188, 2016
Abstract:

In this paper a method of X-ray microtomography (micro-CT) was employed for a direct insight into a microstructure of fibre cement boards of different quality. Four specimens were subjects of examination. Two parameters were determined to characterize the level of compaction of fibres in concrete matrix: mean-square displacement of migrating virtual particles after 500,000 of time steps and a diffusive tortuosity. The results of the investigation had revealed that fibre cement boards differing in density produce different images after processing with micro-CT method. The effect of microstructure tightening due to saturation using dying agent was also detectable.

Keywords:

Fibre cement boards, Delamination of fibres, Computational modelling, X-ray microtomography

Affiliations:
Schabowicz K.-other affiliation
Ranachowski Z.-IPPT PAN
Jóźwiak-Niedźwiedzka D.-IPPT PAN
Radzik Ł.-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)
4.Ranachowski P., Ranachowski Z., Jaroszewski M., Wieczorek K., Kúdela Jr S., Mechanoacoustic Research Method of Degradation Processes in Electroceramics Materials, IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION, ISSN: 1070-9878, DOI: 10.1109/TDEI.2015.005568, Vol.23, No.3, pp.1251-1259, 2016
Abstract:

The paper presents the concept of mechanoacoustic testing of degradation processes of ceramic materials, which is applied to diagnose high voltage insulators in operation. The method depends on the application of slowly increasing compressive loading acting on the sample, with simultaneous recording of acoustic emission (AE) descriptors. The process of loading is continued to the destruction or stopped at different stresses, and the samples are subjected to microscopic examination. Microscopic analysis of the samples enables determining the effects of stress action. The results were compared with the images of similar materials obtained from the insulators after different periods of operation. On this basis, there were distinguished consecutive stages of ageing of electrotechnical porcelain materials and corresponding effects of their structure degradation. Using slowly increasing quasi-static compressive loading in a relatively short-term mechanoacoustic test makes it possible to get results similar to those of long lasting degradation effects in operated electroinsulating objects. Using this method there is possible to describe the factors which affect short and long-term mechanical strength of the tested materials. There is also possible assessment of the validity and application of the theories explaining the strength of porcelains. There was presented research of the influence of the mullite phase on the short- and long-term mechanical strength of electrotechnical porcelain of different types.

Keywords:

Degradation, Stress, Insulators, Porcelain, Aging, Microscopy

Affiliations:
Ranachowski P.-IPPT PAN
Ranachowski Z.-IPPT PAN
Jaroszewski M.-other affiliation
Wieczorek K.-other affiliation
Kúdela Jr S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
5.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)
6.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)
7.Kúdela Jr S., Švec P., Bajana O., Orovčík L., Ranachowski P., Ranachowski Z., Strengthening in dual-phase structured Mg-Li-Zn alloys, KOVOVE MATERIALY-METALLIC MATERIALS, ISSN: 0023-432X, DOI: 10.4149/km_2016_6_483, Vol.54, pp.483-489, 2016
Abstract:

Proof stress Rp0.2 of dual-phase α + β structured Mg-Li and Mg-Li-Zn alloys has been inspected in terms of the strengthening contributions of α- and β-phases. The alloys studied with a variable fraction of α- and β-phases have been subjected to compression straining tests, microhardness measurements and structural analysis by EDX and XRD. Alloying with 1.5 wt.% Zn results in the hardening of both α- and β-phases which however exhibit different hardening responses due to different Zn enrichment. The rule of the mixture has been used to interpret Rp0.2 values by taking into account the fraction of α- and β-phases and their strength level represented by their microhardness. Compression stress-strain curves indicate that work hardening of alloys studied depends considerably on the fraction of α-phase and is higher for Zn-containing alloys.

Keywords:

Mg-Li, Mg-Li-Zn, dual-phase alloy, solution hardening, ageing, work hardening

Affiliations:
Kúdela Jr S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Švec P.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Bajana O.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Orovčík L.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Ranachowski P.-IPPT PAN
Ranachowski Z.-IPPT PAN
8.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)
9.Ranachowski Z., Jóźwiak-Niedźwiedzka D., Ranachowski P., Dąbrowski M., Kúdela Jr S., Dvorak T., The determination of diffusive tortuosity in concrete specimens using X-ray microtomography, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.1515/amm-2015-0140, Vol.60, No.2, pp.1115-1119, 2015
Abstract:

The paper presents a method of pore connectivity analysis applied to specimens of cement based composites differing in water to cement ratio. The method employed X-ray microtomography (micro-CT). Microtomography supplied digitized three-dimensional radiographs of small concrete specimens. The data derived from the radiographs were applied as an input into the application based on the algorithm called ‘random walk simulation’. As the result a parameter called diffusive tortuosity was established and compared with estimated porosity of examined specimens.

Artykuł prezentuje metodę wyznaczania parametru charakteryzującego intensywność połączeń mikroporów w zastosowaniu do próbek kompozytów z matrycą cementową, różniących się stosunkiem wodnocementowym. Metoda bazuje na wynikach badań z zastosowaniem mikrotomografii rentgenowskiej. Analizowano zdigitizowane zestawy danych, opisujące trójwymiarową reprezentację mikrostruktury niewielkich próbek wykonanych z betonu. Przygotowane w ten sposób skany mikrostruktury zastosowano jako dane wejściowe wprowadzone do oprogramowania wykorzystujacego algorytm ‘przypadkowo migrujących cząstek wirtualnych’. W ten sposób wyznaczono parametr mikrostruktury znany jako krętość dyfuzyjna. Parametr ten porównano z porowatością obserwowaną wyznaczoną dla zbadanych próbek przy wykorzystaniu analizy jasności voxeli w analizowanych próbkach.

Keywords:

X-ray tomography, concrete microstructure, diffusive tortuosity

Affiliations:
Ranachowski Z.-IPPT PAN
Jóźwiak-Niedźwiedzka D.-IPPT PAN
Ranachowski P.-IPPT PAN
Dąbrowski M.-IPPT PAN
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)
10.Ranachowski Z., Jóźwiak-Niedźwiedzka D., Ranachowski P., Rejmund F., Dąbrowski M., Kúdela Jr S., Dvorak T., Application of X-ray microtomography and optical microscopy to determine the microstructure of concrete penetrated by carbon dioxide, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.2478/amm-2014-0245, Vol.59, No.4, pp.1451-1457, 2014
Abstract:

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.

Keywords:

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

Affiliations:
Ranachowski Z.-IPPT PAN
Jóźwiak-Niedźwiedzka D.-IPPT PAN
Ranachowski P.-IPPT PAN
Rejmund F.-IPPT PAN
Dąbrowski M.-IPPT PAN
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)
11.Kúdela Jr S., Iždinský K., Oswald S., Ranachowski P., Ranachowski Z., Kúdela S., Decomposition of silica binder during infiltration of Saffil fiber preform with Mg and Mg-Li melts, KOVOVE MATERIALY-METALLIC MATERIALS, ISSN: 0023-432X, Vol.52, No.4, pp.183-188, 2014
Abstract:

Mg and Mg-Li matrix composites were prepared by the melt infiltration of fibrous preform consisting of Saffil alumina fibers and the silica binder. During this process there has occurred decomposition of silica binder and/or surface silica film by displacement redox reactions and the reaction products were characterized using SEM, TEM, SAED, FTIR and XPS techniques. The only reaction products found in Mg infiltrated Saffil preform were MgO and Mg2Si. In Mg-Li melt infiltrated Saffil preform there was found besides MgO and Mg 2 Si also the non- crystalline phase that appears to be the lithium silicate xLi2O ySiO2. Binary lithium silicides and ternary magnesium-lithium silicides were not detected

Keywords:

Mg-Li composites, Saffil fibers, silica binder, melt infiltration, XPS, FTI

Affiliations:
Kúdela Jr S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Iždinský K.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Oswald S.-Institute for Complex Materials (DE)
Ranachowski P.-IPPT PAN
Ranachowski Z.-IPPT PAN
Kúdela S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
12.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)
13.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)
14.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
15.Pieczyska E.A., Tobushi H., Takeda K., Stróż D., Ranachowski Z., Kulasiński K., Kúdela Jr S., Luckner J., Martensite transformation bands studied in TiNi shape memory alloy by infrared and acoustic emission techniques, KOVOVE MATERIALY-METALLIC MATERIALS, ISSN: 0023-432X, Vol.50, pp.309-318, 2012
Abstract:

TiNi shape memory alloy (SMA) specimens have been subjected to tension carried out at various strain rates. The goal was to investigate a nucleation and development of the stressinduced martensitic transformation by infrared (IR) and acoustic emission (AE) techniques. Therefore, both the infrared radiation and acoustic emission data were recorded using a fast infrared camera and acoustic emission set-up, respectively. It has been shown that the initial, macroscopically homogeneous transformation initiates in the elastic stage of the deformation even before the stress-strain curve knee and formation of the localized transformation bands. It has also been found that the homogeneous transformation occurs at similar stress level for all strain rates applied, while the localized martensitic transformation depends on the strain rate. Nucleation and development of the localized transformation bands, detected by the infrared camera, were confirmed by acoustic emission technique. The differences between the IR and AE activities were recorded during the TiNi SMA loading and unloading process, manifesting different dynamics of the stress-induced martensitic forward and reverse transformation.

Keywords:

shape memory alloy, TiNi, superelasticity, martensitic transformation, tension test, acoustic emission

Affiliations:
Pieczyska E.A.-IPPT PAN
Tobushi H.-Aichi Institute of Technology (JP)
Takeda K.-Aichi Institute of Technology (JP)
Stróż D.-other affiliation
Ranachowski Z.-IPPT PAN
Kulasiński K.-IPPT PAN
Kúdela Jr S.-Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Luckner J.-IPPT PAN
16.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)
17.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
18.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
19.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
20.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
21.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

Conference papers
1.Ranachowski Z., Jóźwiak-Niedźwiedzka D., Ranachowski P., Dąbrowski M., Kúdela Jr S., Dvorak T., Analysis of pore distribution and connectivity in concrete using X-ray microtomography, BMC-11, 11th International Symposium on Brittle Matrix Composites, 2015-09-28/09-30, Warsaw (PL), pp.203-212, 2015
Abstract:

In the paper a method of X-ray microtomography (micro-CT) was employed for a direct insight into a microstructure of concrete with a practical resolution of approx. 10 micrometers3. Two sets of specimens were subjects of examination. The spatial concentration of air pores was investigated in three concretes differing in the amount of the supplement of high calcium fly ash (HCFA). The parameter of pore connectivity called diffusive tortuosity was determined in three other concretes made of the same ingredients but differing in water to cement ratio. The quantitative results obtained with application of described procedures are applicable in material characterization.

Keywords:

X-ray microtomography, concrete, microstructure

Affiliations:
Ranachowski Z.-IPPT PAN
Jóźwiak-Niedźwiedzka D.-IPPT PAN
Ranachowski P.-IPPT PAN
Dąbrowski M.-IPPT PAN
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)
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

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)