MATERIALS ENGINEERING, Vol. 19, 2012, No. 1
published on February 2012

CONTENTS and ABSTRACTS

Neslušan, M., Šípek, M., Mrázik, J. (pp. 1-11)
ANALYSIS OF CHIP FORMATION DURING HARD TURNING THROUGH ACOUSTIC EMISSION Full text (PDF 2152 kB) - Available online 18 November 2011
The paper deals with analysis of chip formation and related aspects of the chip formation during turning hardened steel 100Cr6. The paper draws a comparison of some aspects of the chip formation between turning annealed and hardened roll bearing steel. The results of the analysis show that there is the formation of a segmented chip in the case of hard turning. Frequency of segmentation is very high. A conventional piezoelectric dynamometer limits the frequency response to about 3.5 kHz. On the other hand, the frequency of process fluctuation may by obtained by using accelerometers or acoustic emission. This paper reports about the dynamic character of cutting process when hard turning and correlation among the calculated segmentation frequencies and the experimental analysis.



Trojanová, Z., Lukáč, P., Podrábský, T., Pešička, J. (pp. 12-17)
HIGH STRAIN RATE BEHAVIOUR OF AN AZ31 + 0.5 Ca MAGNESIUM ALLOY Full text (PDF 1170 kB) - Available online 27 November 2011
The paper reports behaviour of magnesium alloy AZ31 (nominal composition 3 % Al - 1 % Zn – balance Mg) with an addition of 0.5 wt. % Ca at high strain rates. Samples were prepared by the squeeze cast technology. Dynamic compression Hopkinson tests were performed at room temperature with impact velocities ranging from 11.2 to 21.9 m.s-1. A rapid increase of the flow stress and the strain rate sensitivity was observed at high strain rates. Transmission electron microscopy showed extremely high dislocation density and mechanical twins of two types. Adiabatic shear banding is discussed as the reason for the observed behaviour at high strain rates.



Navrátilová, L., Obrtlík, K., Kunz, L. (pp. 18-21)
CYCLIC PLASTIC BEHAVIOUR OF UFG COPPER UNDER CONTROLLED STRESS AND STRAIN LOADING Full text (PDF 663 kB) - Available online 29 November 2011
The influence of stress- and strain-controlled loading on microstructure and cyclic plastic behaviour of ultrafine-grained copper prepared by equal channel angular pressing was examined. The stability of microstructure is a characteristic feature for stress-controlled test whereas grain coarsening and development of bimodal structure was observed after plastic strain-controlled tests. An attempt to explain the observed behaviour was made.



Mintách, R., Nový, F., Bokůvka, O., Chalupová, M. (pp. 22-28)
IMPACT STRENGTH AND FAILURE ANALYSIS OF WELDED DAMASCUS STEEL Full text (PDF 2006 kB) - Available online 3 December 2011
The aim of this work was the experimental research of damascus steel from point of view of the structural analyze, impact strength and failure analyzes. The damascus steel was produced by method of forged welding from STN 41 4260 spring steel and STN 41 9312 tool steel. The damascus steel consisted of both 84 and 168 layers. The impact strength was experimentally determined for original steels and damascus steels after heat treatment in dependence on temperature in the range from -60 to 160 °C. It has been found that the impact strength of experimental steels decreased with decreasing temperature behind with correlated change of damage mode. In the case of experimental tests performed at high temperature ductile fracture was revealed and with decreasing temperature proportion of cleavage facets increased. Only the STN 41 9312 steel did not show considerable difference in values of the impact strength with changing temperature.



Štefánik, P., Kavecký, Š., Iždinský, K. (pp. 29-33)
DEPOSITION OF NICKEL ON CARBON FIBRES BY GALVANIC METHOD Full text (PDF 384 kB) - Available online 8 December 2011
The investigation of coating parameters in quasi-static coating of Ni layer on carbon fibre tow by galvanic method is presented. The tow of fibres was immersed in typical galvanic bath based on NiSO4, NiCl2, Na2SO4 and H3BO3 and current to carbon fibres was supplied by two leading metal rolls which are parts of continuous coating apparatus. The main parameters were current of 1 A, electrolyte temperature of 50 °C and the distance from power contacts to level of galvanic bath (8 or 13 cm). The amount and structure of deposited Ni layer at coating time 15 and 90 seconds of exposure in electrolyte and depth of immersion of tow into bath were discussed.



Martinkovič, M. (pp. 34-38)
UTILIZATION OF STEREOLOGY FOR QUANTITATIVE ANALYSIS OF PLASTIC DEFORMATION OF FORMING PIECES Full text (PDF 309 kB) - Available online 9 December 2011
Mechanical working leads to final properties of forming pieces, which are affected by conditions of production technology. Utilization of stereology leads to the detail analysis of three-dimensional plastic deformed material structure by different forming technologies, e.g. forging, extruding, upsetting, metal spinning, drawing etc. The microstructure of cold drawing wires was analyzed. Grain boundaries orientation was measured on the parallel section of wire with a different degree of deformation and direct axis plastic deformation was evaluated in bulk formed part. The strain of probes on their sections was obtained using stereology by measurement of degree of grain boundary orientation which was converted to deformation using model of conversion of grain boundary orientation degree to deformation.





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