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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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Vztah mezi materiálovými vlastnosti spongiózní kosti a její relativní hustotou stanovený pomocí malých vzorků a optické metody
Jiroušek, Ondřej
Experimental procedures utilizing an optical identification method used for evaluation of mechanical properties of cancellous bone using small samples of cylindrical shape are described in the paper. To measure very small strains of the cancellous bone, high-resolution CCD-camera and algorithm making use of sub-pixel determination of the centre-of-gravity of the markers are used. The experimental procedures serve for consequent evaluation of the relationship between apparent density and Young\'s modulus of elasticity and ultimate strength of the cancellous bone
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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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Časově závislé mechanické vlastnosti jedné epoxidové komposice
Minster, Jiří ; Hristova, Ju.
The paper presents results of experimental investigation of time-dependent mechanical characteristics of a homogeneous isotropic epoxy composition used either as a construction material or a s the matrix of a particulate or fibre composite. The experimental programme involved short- medium- and long-term creep and relaxation investigations of samples loaded by quasi-static pressure.The Young modulus, relaxation modulus and viscoelastic compliance were defined within active pressure and also delayed recovery. The results can serve to assess influences of some important mechanical and non-mechanical loads (mechanical loading, temperature, physical aging, climate effects)
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