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Influence of Heterogeneity of Microstructure on Creep Behaviour of SPD Metals
Král, Petr ; Dvořák, Jiří ; Kvapilová, Marie ; Svoboda, Milan ; Sklenička, Václav
The methods of severe plastic deformation enable a production of bulk metals with the submicrometer or even nanometer grain size. Experiments were conducted to determine an effect of equal-channel angular pressing (ECAP) on the creep behavior of pure metal. The ECAP deformation was performed at room temperature by route Bc. Constant load creep tests in tension were conducted at 373 K under different stresses. The values of the stress exponent n of the minimum creep rate for ultrafine-grained material were determined. Microstructure of samples was characterized by scanning electron microscope equipped with the electron backscatter diffraction unit. Heterogeneity of microstructure was evaluated by coefficient of variation CVa. It was found that the fracture behavior in UFG materials is influenced by GBS, formation of mesoscopic shear bands and cavitation.
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Kalibrace konstitutivního modelu trabekulární kosti na základě nanoindentace
Zlámal, Petr ; Jiroušek, Ondřej ; Němeček, J.
The paper deals with investigation of a trabecular bone behaviour during nanoindentation test. Behavior of trabecular bone is investigated using real nanoindentation and finite element simulation. Two different plasticity criteria for material model of trabeculae are tested, namely von Mises and Drucker-Prager. Von Mises criterium is extended bilinear isotropic hardening. Constants needed for numerical material model are obtained from fitting procedure of a experimetal load-displacement curve.
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Studium mechanických vlastností supertvrdých nanostrukturních vrstev
Buršíková, V. ; Jašek, O. ; Frgala, Z. ; Karásková, M. ; Zajíčková, L. ; Buršík, Jiří ; Bláhová, O. ; Grančič, B. ; Mikula, M. ; Klapetek, P.
Study of Mechanical Properties of Superhard Nanostructured Thin Films.
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Měření tvrdosti nehomogenních plazmových nástřiků
Čtvrtlík, Radim ; Stranyánek, Martin ; Boháč, Petr ; Jastrabík, Lubomír ; Hrabovský, Milan ; Ctibor, Pavel
Paper deals with testing of mechanical properties of plasma sprayed coatings TiO2 by Depth Sensing Indentation performed on measuring system NanoTest 600™. The NT600™ is a modular measuring instrument with unique design, which applies the loading force in horizontal direction. The platform can measure and evaluate hardness, elastic modulus, adhesion, wear, fracture and also dynamic properties. In the last years the new plasma spraying technology of ceramic and ceramic-metal materials has became as very convenient technique in many industrial and reconstruction processes. The investigated samples of plasma sprayed coatings were prepared in Institute of Plasma Physics of the Academy of Sciences of the Czech Republic. The goal of this paper is to contribute to deepening the knowledge in local distribution of mechanical properties in plasma sprayed coatings, especially of hardness and elastic modulus.
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Instrumentovaný indentační test v nano- a mikroměřítku
Buršíková, V. ; Buršík, Jiří ; Bláhová, O. ; Dušek, J. ; Navrátil, V.
Several materials were chosen to span a wide range of hardness and structure,including pure copper,nickel,titanium,cadmium,zinc and silver.Nanoindentation hardness and microhardness values in wide interval of loads,measured by DSI method and classical Vickers microhardness method were compared in view of indentation Size Effect.
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Nanoindentation and theoretical strength in metals and intermetallics
Šob, Mojmír ; Legut, Dominik ; Friák, Martin ; Fiala, J. ; Vitek, V. ; Hafner, J.
The present contribution gives an account of applications of quantum-mechanical (first-principles) electronic structure calculations to the problem of theoretical strength in metals and intermetallics. First, we briefly describe the way of simulating the tensile test and the electronic structure calculational method. Then we discuss the theoretical strength values in a number of elemental metals and intermetallics and compare them with available experimental data, both from measurements on whiskers and from nanoindentation experiments.
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