MATERIALS ENGINEERING, Vol. 19 (2012), No. 2

CONTENTS and ABSTRACTS

Tillová, E., Chalupová, M. (pp. 39-46)
SOLUTION TREATMENT EFFECT ON MICROSTRUCTURE AND MECHANICAL PROPERTIES OF AUTOMOTIVE CAST ALLOY Full text (PDF 663 kB) - Available online 06 February 2012
The contribution describes influence of the heat treatment (solution treatment at temperature 545°C and 565°C with different holding time 2, 4, 8, 16 and 32 hours; than water quenching at 40°C and natural aging at room temperature during 24 hours) on mechanical properties (tensile strength and Brinell hardness) and microstructure of the secondary AlSi12Cu1Fe automotive cast alloy. Mechanical properties were measured in line with EN ISO. A combination of different analytical techniques (light microscopy, scanning electron microscopy (SEM)) were therefore been used for study of microstructure. Solution treatment led to changes in microstructure includes the spheroidization and coarsening of eutectic silicon. The dissolution of precipitates and the precipitation of finer hardening phase further increase the hardness and tensile strength of the alloy. Optimal solution treatment (545°C/4 hours) most improves mechanical properties and there mechanical properties are comparable with mechanical properties of primary AlSi12Cu1Fe alloy. Solution treatment at 565 °C caused testing samples distortion, local melting process and is not applicable for this secondary alloy with 12.5 % Si.



Štefániková, M., Moravčík, R., Kocúrová, K. (pp. 47-51)
THE ANALYSIS OF CAUSES OF LORRY PISTON COMBUSTION ENGINE DAMAGE Full text (PDF 896 kB) - Available online 17 February 2012
The article deals with analysis of causes of lorry piston combustion engine damage. For docummentation and analysis of causes was used macroscopical, microscopical and scanning electron microscopy. The analysis showed that the reason of fatal damage resides in production process of lorry combustion pistons which proved in implication of fatigue damage and subsequent burnout in two piston place.



Liščić, B., Filetin, T. (pp. 52-63)
MEASUREMENT OF QUENCHING INTENSITY, CALCULATION OF HEAT TRANSFER COEFFICIENT AND GLOBAL DATABASE OF LIQUID QUENCHANTS Full text (PDF 883 kB) - Available online 26 February 2012
This paper explains the need for a database of cooling intensities for liquid quenchants, in order to predict the quench hardness, microstructure, stresses and distortion, when real engineering components of complex geometry are quenched. The existing laboratory procedures for cooling intensity evaluation, using small test specimens, and Lumped-Heat-Capacity Method for calculation of heat transfer coefficient, are presented. Temperature Gradient Method for heat transfer calculation in workshop conditions, when using the Liscic/Petrofer probe, has been elaborated. Critical heat flux densities and their relation to the initial heat flux density, is explained. Specific facilities for testing quenching intensity in workshop conditions, are shown.
The two phase project of the International Federation for Heat Treatment and Surface Engineering (IFHTSE), as recently approved, is mentioned.




Jurči, P., Krum, S. (pp. 64-70)
MEASUREMENT OF QUENCHING SELF-LUBRICATING THIN FILMS FOR TOOL STEELS Full text (PDF 791 kB) - Available online 5 March 2012
Specimens made from Vanadis 6 cold work tool steel were machined, ground, heat processed by standard regime and finally mirror polished. After that, they were layered with CrAgN. The Ag-content in the layers was chosen to 3 wt% and 15 wt% respectively. Microstructural analysis revealed that the addition of 3 wt%Ag did not influence the growth manner of the films but the addition of 15 wt%Ag has made considerable changes in the film growth. The layer with 3 wt%Ag had excellent adhesion on the steel substrate. On the other hand, the addition of 15%Ag had strongly negative impact on the coating adhesion. Similar effect of different Ag addition has been established also to both the hardness and the Young modulus of the films, also. Both films have superior tribological properties against hard material (alumina) as well as against soft counterpart (CuSn6 as-cast bronze).



Molnár, G., Molnár, L.M., Bojtár, I. (pp. 71-81)
PREPARING A COMPREHENSIVE ANALYSIS OF THE MECHANICAL CLASSIFICATION OF STRUCTURAL GLASS Full text (PDF 2356 kB) - Available online 10 March 2012
Present study deals with the mesostructure analysis of the structural glass. The subject is about to prepare a comprehensive mechanical analysis, aimed on the understanding of the multiscale mechanical behaviour of soda-lime-silica glass used as an architectural element.
After a brief description of the micro and mesostructure of glass we will explain our goals in this analysis.
We have divided the glass plate – from a mesoscopic aspect – into three major regions. The first region is the external surface, which is the largest area of a plate. The effect of the surface imperfections is negligible due to a grinded edge finishing, so we considered the second region as the edge. The third region contains the inhomogeneities in the glass material itself. To describe the mesostructure we have done atomic force microscopy (AFM) and micro computed tomography (µCT) scans. We used the AFM to image the surface and the edge and µCT to collect geometrical information from the inhomogeneities.
The aim of the overall analysis is to develop a new certification procedure to qualify the structural glass in a mechanical a way.




Kocúrová, K., Hazlinger, M., Štefániková, M. (pp. 82-87)
MICROSTRUCTURE AND FRACTOGRAPHIC ANALYSIS OF DAMAGE REASONS OF COGWHEEL Full text (PDF 1377 kB) - Available online 16 April 2012
The article provides an analysis of the damaged cogwheel, which was used as the drive wheel (pinion) in the steering gear box of the construction machine. The degradation of the cogwheel arose during the warranty period, after seven months of using of the construction machine. The experimental analysis revealed that the cause of the degradation of the cogwheel was due to high mechanical stress in the operating conditions of construction machine.







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