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Properties of bulk nanostructured Al-based alloy at cyclic loading
Chlupová, Alice ; Chlup, Zdeněk
Al-based alloy having a nominal chemical composition of Al93Fe3Cr2Ti2 (at.%) is highly promising structural material due to advantageous weight-strength ratio and in comparison with commercially used Al alloys also good thermal stability because of presence of reinforcing icosahedral quaiscrystals in the structure. In the present work the mechanical properties and especially fatigue behaviour of this type of nanoquazicrystalline material obtained in bulk form are described. For cyclic loading the cylindrical specimens were machined from two types of extrudates with different powder particle size (PPS). Fatigue properties were studied using servohydraulic MTS machine and cyclic loading was performed at constant stress amplitude with positive mean stress. Measured stress-strain data were evaluated and fatigue life in form of S-N curves was obtained. Fracture surface of broken testpieces was observed, fractographic analysis was performed and fracture mechanism was evaluated.
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Hodnocení mechanických vlastností částicových polymerních kompozitů pomocí měření mikrotvrdosti
Minster, Jiří ; Berka, L. ; Hristova, J.
The applicability of Vickers microhardness measurements for mechanical assessment of heterogeneous polymer composites (filled polymer composites and polymer concretes) is discussed. Two types of composites based on epoxy and polyester matrices were investigated and two types of finely dispersed fillers were used with the 20% volumetric concentration of the individual fillers. The reinforcing effect of the hard filler and changes in the microhardness (i.e. in the yield strengths and moduli) in the neighbourhood of filler micrograins have been substantiated.
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Impact of the orientation and width of wood rings on the spreading of ultrasound in the wood structure
Kloiber, Michal ; Kotlínová, M.
The subject of the paper is the relationship between ultrasound wave velocity in wood, tree rings orientation and width, and wood mechanical properties (MOE in our case). For measuring, the Arborsonic Decay Detector has been chosen. Sound velocity decreased from radial to tangential direction of measurement. In groups with radial (3) and diagonal (2) position of tree ring, increasing of tree ring width has increased sound velocity. In group with tangential tree ring position no significant influence of tree ring width has been found.
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