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Thermal aspects of friction in joint replacements
Němeček, R. ; Pražák, Josef
Thermal effects during friction of femoral (vitalium) and tibial (UHMWPE) components of the knee joint replacement with the physiological solution, HA, bovine serum lubrication depending on the load, frequence and damage of UHMWPE are studied. There is the possibility of monitoring the state of joint replacements in vivo.
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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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Kontakt válcových ploch pokrytých tenkými pružnými nestlačitelnými vrstvami
Hlaváček, Miroslav
The paper deals with a frictionless contact problem of two parallel rigid cylindrical surfaces, one encased in the other, coated with thin elastic transversely isotropic and incompressible layers. A simplifying approximation for the displacement in the coating enables the problem to be formulated using stress and strain averaged through the coating thickness. Analytical results are obtained for the contact width and contact stress distribution. The results are applied to the human ankle joint and generalized for articular cartilage with depth-dependent properties
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Vibratin of bridges under high speed trains
Frýba, Ladislav
The theoretical model explains the dynamic behaviour of railway bridges subjected to high speed trains. The method of integral transformations gives the deflections, stresses and vertical accelerations of the beam in a compact form. The numerical study presents a survey on the effect of several parameters.
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Experimentální výzkum odporu rotačně se pohybující kulové částice
Lukerchenko, Nikolay ; Kvurt, Y. ; Chára, Zdeněk ; Vlasák, Pavel
Saltatory solid particles conveyed by fluid impact a channel bed from time to time. As a result of the collision the particles receive angular velocity, which gradually decreases with time. For numerical simulation of saltation it is necessary to know values of the drag rotation coefficient. In this paper experimental results of the rotating spherical particles moving in water are described. The rubber spherical balls with density near that of water were used; each of them was speeded up in a special chute that ensured that the particle rotated in a given plane. Values of the drag coefficient of the rotating spherical particle were determined in a dependence on rotation particle Reynolds number
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