MATERIALS ENGINEERING, Vol. 16, 2009, No. 1
published on February 2009

CONTENTS and ABSTRACTS

Iždinská, Z., Kolenič, F. (pp. 1-8)
THE INFLUENCE OF POSTHEAT TREATMENT ON FERRITE REDISTRIBUTION IN DUPLEX STEELS ELECTRON BEAM WELDS Full text (PDF 1181 kB)
The duplex stainless steel is two-phase steel with the structure composed of austenite and ferrite with optimum austenite/ferrite proportion 50%. At present, classical arc processes for welding duplex steels are generally regarded as acceptable. On the other hand electron and laser beam welding is up to now considered less suitable for welding duplex steels. The submitted work presents the results of testing various thermal conditions at welding duplex stainless steel with electron beam. It was shown, that application of suitable postheat made possible to reduce the ferrite content in weld metal.

Faktorová, D. (pp. 9-13)
ENHANCEMENT OF DEFECTS IN METAL SAMPLE CHARACTERISTICS EVALUATION BY USING MICROWAVE METHODS Full text (PDF 176 kB)
In the paper main consideration is paid to investigation of inhomogenities in metal sample from the standpoint of their impedance properties and reflected signal amplitude. Such application include inspecting modern materials such as composites, detecting and characterizing surface and volume flaws, and evaluating the compressive strength of cement structures.The paper deals with measurement of reflex coefficient in dependence on crack depth on metal samples on microwave frequencies from the X – band. Evaluations are made by means of quantities used in microwave technique.

Kotelko, M., Lipa, S., Mania, R.J. (pp. 14-19)
DYNAMIC CRUSHING TESTS OF THIN-WALLED MEMBERS UNDER COMPRESSION Full text (PDF 1046 kB)
The paper deals with the experimental investigation into crushing collapse behaviour of two types of thin-walled structural members: tubular multi-member element subject to lateral crushing load and top hat-section column under axial compression. Especially designed experimental stand, in which a dynamical crushing load is realized by means of hydraulic system, is presented. Experimental, dynamical load-deformation curves are compared with those obtained from FE simulations and obtained from quasi-static tests. Conclusions concerning an agreement between results of numerical simulations and results of static and dynamic tests are derived.

Vezér, S.T., Major, Z. (pp. 20-25)
RUNNING CONDITION FRETTING MAPS OF POLYMER MATERIALS Full text (PDF 1675 kB)
Due to the industrial demand, the determination of the wear behaviour of polymeric materials is an important research task. Rubbers and elastomers are used widely in contacts, where wear is the dominant failure mechanisms. Furthermore, only the material properties under large displacements were investigated in the majority of existing studies. Depending on the input physical parameters of the tribological systems small oscillations are also observed on the measured signals (due to stick-slip like effect) in the contact zone of the elastomers. To describe the failure behaviour under this special condition, a novel fretting fatigue test system was developed and built on a electro-dynamical shaker in this study. The contact area were defined with some additional test, like 2D full field strain analysis, compression and creep tests. Based on the methodology developed and applied for steels and polymer composites, Running Condition Fretting Maps for two elastomer grades (HNBR and TPU) were determined.

Brezinová, J., Guzanová, A. (pp. 26-33)
THE WEAR OF INJECTION MOULD FUNCTIONAL PARTS IN CONTACT WITH POLYMER COMPOSITES Full text (PDF 7691 kB)
The paper deals with the evaluation of material wear of injection moulds made of aluminium alloy Alumec 89 and copper alloy Moldmax HH in friction couples with plastomer materials with various filler contents. The friction relations in injection moulding were simulated in an adhesion dry wear test using an Amsler machine, with an area contact of the friction couple materials. The wear intensity was evaluated by determination of friction coefficient and relative wearing by the mass loss. Surface morphology changes of evaluated alloys after wear and the thermal conditions in particular friction couples were analysed simultaneously.

Švec, P., Brusilová, A., Kozánková, J. (pp. 34-40)
EFFECT OF MICROSTRUCTURE AND MECHANICAL PROPERTIES ON WEAR RESISTANCE OF SILICON NITRIDE CERAMICS Full text (PDF 1820 kB)
The wear of Si3N4 ceramics with high-resistant abrasive material during friction applications was analyzed. Effects of the hot pressing parameters on the microstructures and properties of ceramic samples were evaluated. Negative influence of grain growth with increasing of the ?-Si3N4 phase ratio on wear resistance of tested materials was proved. The volume loss of separate ceramic materials during the wear tests depended mainly inversely proportional on the hardness of ceramics. Both microcutting and microcracking mechanisms took part during the wear of Si3N4 ceramics.


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