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Contact pressure between head and helmet loaded by external forces
Micka, Michal ; Jírová, Jitka
The simple test of the bike helmet loaded by statical forces on the top of the head is simulated using program ANSYS. The standardized model for laboratory tests of helmets is used as the model of the head. The goal of the project is to obtain details about contact forces or stresses between the cranium and the helmets, which will be used for future development of safety helmets or by modelling of a hurt of the head at accident.
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Experimentální výzkum spolehlivosti těsnění kabelových prostupů v Pražském metru po povodních v létě 2002
Jíra, J. ; Jírová, Jitka ; Bouška, P. ; Vokáč, M.
Confluence of the rivers Berounka and Sázava and outflows from the Vltava dam cascade caused the flow in the lower part of the river Vltava in Prague. The Vltava culminated in Prague on 14 August with a flow of 5160 m3.s-1; this corresponds to a period of recurrence of 500 years. The extension of floods in the Vltava valley in Prague caused penetration of water into underground spaces of the Metro and water flooded 19 of 53 underground stations. Looseness of cable bushings through pressure interfaces and non-closure of some pressure interfaces were the most important cause of spreading of water in underground spaces. After the floods of August 2002 the accredited laboratory CTU in Prague, Klokner Institute designed a methodology of experiments and testing system and performed tests on reliability of cable bushings and on material properties of the U 5000. Results of experiments lead to the recommendation to replace all the existing cable bushing in Prague Metro
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Use of X-ray computed tomography for construction of FE models of bones
Jiroušek, Ondřej ; Jírová, Jitka ; Máca, J.
The article reports on procedures used for development of FE models of bones on basis of data obtained from series of computed tomography (CT) scans. These models include mechanical properties reflecting the bone inhomogeneity through apparent density which can be easily retrieved from the CT scans. Experimental procedures used for evaluation of mechanical properties of cancellous bone using small samples of cylindrical shape were designed in such a way, which allows for determination of the viscoelastic properties of cancellous bone. Both compressive and tensile specimens are tested while for the strain measurement an optical method utilizing CCD camera of high resolution is used. Relationship between the apparent density and mechanical properties of cancellous bone in a power-law form is proposed.
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Experimentální vyšetřování závislosti mezi mechanickými vlastnostmi spongiózní kosti a její relativní hustotou
Jiroušek, Ondřej ; Jírová, Jitka ; Jíra, J.
Finite element models of parts of human skeletal system are nowadays constructed on basis of data obtained from Computed Tomography or Magnetic Resonance images. Material properties of cancellous bone have been found to be strongly dependent on apparent density of the tissue. Experimental procedures used for evaluation of mechanical properties of cancellous bone using small samples of cylindrical shape will be described and relationship between the apparent density and Young's modulus of elasticity as well as ultimate strength are proposed. Compressive and tensile specimens are used while for the strains are measured using an optical method utilizing CCD camera of high resolution
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