MATERIALS ENGINEERING, Vol. 20, 2013, No. 1
published on February 2013

CONTENTS and ABSTRACTS

EDITORIAL Full text (PDF 77 kB) - Available online 29 January 2013
Dear readers, Dear friends.
You hold in your hands the first issue of the jubilee volume of the scientific journal Materials Engineering – Materiálové inžinierstvo (MEMI). The scientific journal published by the Faculty of Mechanical Engineering of the University of Žilina celebrates 20 years of its existence. The first issue of the journal appeared in 1994 with the aim to publish new papers on metallic and non-metallic construction materials, operations and technologies providing higher resistance to the limit state. One of the journal´s objectives was to publish the results for the general and professional public, to provide a forum for experienced scientists and to present the results of young researchers. The journal has been developing during the twenty years of existence. It has been adapting to the development both in its research area and publishing technology. Scope, contents, design, editorial board and editors have been changing. Since 2008 the journal has been published in English to enhance the international impact of the journal. Since 2011 the electronic submission and publication system has been working.
One of the MEMI founders and its first editor-in-chief was dr.h.c. prof. Ing. Anton Puškár, DrSc. in 1994-1999. Prof. Ing. Otakar Bokůvka, PhD. continued in 2000-2010 and now, assoc. prof. Ing. Branislav Hadzima, PhD. is the editor-in-chief. Figuratively speaking, the journal Materials Engineering – Materiálové inžinierstvo relived the years of infancy, successfully coped with the years of pubescence and has grown up to a young man with clear aims and ambitions – to perform not only scientific and informative tasks, but also the tasks concerning communication between institutions and people within and outside Europe.
The scientific journal Materials Engineering – Materiálové inžinierstvo is a recognized periodical (published quarterly). On the occasion of its anniversary, I would like to thank to all who contributed to its existence and impact in technical field of scientific knowledge over many years. A big thank you to the readers, authors and reviewers who create the journal. It is possible to celebrate the journal´s anniversary mainly thanks to you.
I wish the scientific journal Materials Engineering – Materiálové inžinierstvo viability, competent and creative authors, many readers and last but not least, enthusiastic editorial board for the years ahead.

Otakar Bokůvka
Chairman of Editorial Board of MEMI journal




Żórawski, W., Bokůvka, O. (pp. 2-11)
PROPERTIES OF PLASMA AND HVOF SPRAYED COATINGS Full text (PDF 1140 kB) - Available online 13 November 2012
The article compares the properties of plasma and HVOF thermally sprayed coatings obtained by blending the NiCrBSi and Fe2O3 powders. The deposition was performed by means of the Plancer PN-120 and the Diamond Jet guns for plasma spraying and HVOF spraying respectively. The SEM (EDS) method was employed to study the microstructure of the produced coatings. Although the blended powders differ in particle size, shape, and distribution, it is possible to obtain composite coatings with an NiCrBSi matrix containing iron oxides. Except for a different microstructure, plasma and HVOF coatings have a different phase composition, which was examined using the Bruker D-8 Advance diffractometer. Studies of the coatings wear and scuffing resistance showed that an optimal content of Fe2O3 is about 26 % for plasma sprayed coatings and 22.5 % for HVOF deposited coatings.





Brezinová, J., Guzanová, A., Balog, P. (pp. 12-21)
QUALITY OF WELD CLADS APPLIED BY SAW METHOD IN ADHESIVE WEAR CONDITIONS Full text (PDF 1339 kB) - Available online 19 November 2012
This contribution deals with the analysis of the renovation layer quality of continuous casting steel rolls, developed through the submerged arc surfacing method (SAW). The continuous casting roll was analysed via the degradation phenomena which act during the operation. Four kinds of filler materials were used for the renovation of the worn roll. Surfacing was carried out as a three-layer in order to eliminate the need for intermediate layer formation. The quality of weld deposits was evaluated in terms of the structure, hardness and wear resistance of weld deposits at 23°C and 400 °C using pin-on-disc wear test. The best properties showed newly developed filler material W8-WLDC8 from the point of view of the hardness, together with wear resistance of the deposited layers in room and elevated temperatures.





Žmindák, M., Riecky, D., Dudinský, M. (pp. 22-31)
FINITE ELEMENT IMPLEMENTATION OF DELAMINATION IN COMPOSITE PLATES Full text (PDF 827 kB) - Available online 10 December 2012
Modelling of composite structures by finite element (FE) codes to effectively model certain critical failure modes such as delamination is limited. Previous efforts to model delamination and debonding failure modes using FE codes have typically relied on ad hoc failure criteria and quasi-static fracture data. Improvements to these modelling procedures can be made by using an approach based on fracture mechanics. A study of modelling delamination using the finite element code ANSYS was conducted. This investigation demonstrates the modelling of composites through improved delamination modelling. Further developments to this approach may be improved.





Weltsch, Z., Hlinka, J. (pp. 32-39)
THE EFFECT OF REFLOW ON WETTABILITY OF Sn 96.5 Ag 3 Cu 0.5 SOLDER Full text (PDF 422 kB) - Available online 18 December 2012
Surface conditions on Printed Circuit Board (PCB) final finishes have an important impact on the wetting behavior with lead-free solder. The improvement of the wettability in liquid Sn 96.5 Ag 3 Cu 0.5 Solder alloy on PCB substrate was measured with a sessile drop method at 523 K temperature. Wetting properties were determined in normal atmospheric air and inert atmosphere. The wetting angles increasing with the number of reflows both atmosphere. The effect of the atmosphere has a huge importance of the oxidation which manifests itself of the measured wetting angles. One of the most important factors affecting the wetting properties is the amount of oxygen in the soldering atmosphere. Using the inert atmosphere is crucial in case of Pb-free solders, particularly after reflows.





Chandel, V.S., Manohar, S., Srivastava, A. K., Manohar, R. (pp. 40-44)
AN APPARATUS OF INCREASED PRECISION FOR THE MEASUREMENT OF ELECTRO-OPTICAL PARAMETERS OF LIQUID CRYSTALS Full text (PDF 368 kB) - Available online 28 December 2012
The ferroelectric liquid crystals (FLCs) are demanding high attention now a day, because of their potential applications in many electro-optical devices, particularly in displays. The suitable applications of FLCs in devices are decided by their electro-optical properties like tilt angle, birefringence and spontaneous polarization. In this paper we are presenting a new apparatus for highly accurate measurement of electro-optical parameters of FLCs. The accuracy of the apparatus is the best among the currently available equipments in the market. The accuracy and performance of the apparatus has been confirmed by performing the experiments on standard ferroelectric liquid crystals.





Mahbub, R., Hossain, Md. S., Islam, Md. F. (pp. 45-54)
STRUCTURAL CHARACTERISTICS & DIELECTRIC PROPERTIES OF TANTALUM OXIDE DOPED BARIUM TITANATE BASED MATERIALS Full text (PDF 697 kB) - Available online 5 January 2013
In this research, the causal relationship between the dielectric properties and the structural characteristics of 0.5 & 1.0 mole % Ta2O5 doped BaTiO3 based ceramic materials were investigated under different sintering conditions. Dielectric properties and microstructure of BaTio3 ceramics were significantly influenced by the addition of a small amount of Ta2O5. Dielectric properties were investigated by measuring the dielectric constant (k) as a function of temperature and frequency. Percent theoretical density (%TD) above 90 % was achieved for 0.5 and 1.0 mole %Ta2O5 doped BaTiO3. It was observed that the grain size decreased markedly above a doping concentration of 0.5 mole % Ta2O5. Although fine grain size down to 200 - 300 nm was attained, grain sizes in the range of 1-1.8µm showed the most alluring properties. The fine-grain quality and high density of the Ta2O5 doped BaTiO3 ceramic resulted in tenfold increase of dielectric constant. Stable value of dielectric constant as high as 13000 - 14000 was found in the temperature range of 55 to 80 °C, for 1.0 mole % Ta2O5 doped samples with corresponding shift of Curie point to ~82 °C. Experiments divulged that incorporation of a proper content of Ta2O5 in BaTiO3 could control the grain growth, shift the Curie temperature and hence significantly improve the dielectric property of the BaTiO3 ceramics.





© University of Žilina, Faculty of Mechanical Engineering, ISSN 1335-0803