Národní úložiště šedé literatury Nalezeno 2 záznamů.  Hledání trvalo 0.00 vteřin. 
Stress relaxation in partially pyrolysed SiOC materials
Halasová, Martina ; Chlup, Zdeněk ; Černý, Martin ; Strachota, Adam ; Dlouhý, Ivo
This paper focuses on the difficulty with Vickers hardness evaluation of SiOC materials. To evaluate it, diagonals of an indent are crucial. Due to stress relaxation in experimental material it was not possible to evaluate it in the whole range of experimental temperatures. As experimental materials were used two types of commercialy available polysiloxane resins, pyrolysed in range from 400 to 1000°C.
Determination of mechanical properties of light alloys and composites by means of Small Punch Testing
Bártková, Denisa ; Langer, J. ; Dymáček, Petr ; Válka, L.
Nowadays, in many testing areas a volume of experimental material is limited (laboratory-scaled volume, semidestructive approach). Therefore many testing techniques on miniature samples were devised. Principle of Small Punch Test (SPT) method is a penetration of small puncher through thin disc placed on a ring until the disc bursts. In dependence on loading mode it can provide information comparable to uniaxial tensile tests (UTT) and/or conventional constant load creep tests. However clarification of relations between SPT and conventional methods is difficult and empirical formulas are non-universal. The aim of this study is to i) evaluate mechanical properties of aluminium and magnesium alloys and its composites by means of SPT, ii) compare SPT results with UTT, iii) validate correlation formulas from literature, iv) propose more advanced approach to define correlation between UTT and SPT. Measurement were carried out at constant deflection rate (SPT-CDR) in two different laboratoires. Results from both laboratories were compared to evaluate the reproducibility of the method. Better results agreement was reached for the ultimate strength measurements. Yield strength results exhibited greater variance. An influence of pre-deformation of the sample on yield strength and deflection at maximum force was also identified. We can conclude, that for quantitative estimation of strength parameters we can use correlation formulas based on materials with similar composition and fracture behaviour.

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