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Basic biomechanical characterization of polyurethane based artificial cancellous structures
Šleichrt, Jan ; Kytýř, Daniel ; Pithartová, Kateřina ; Senck, S. ; Fürst, D. ; Schrempf, A.
The main goal of this study is to validate elementary mechanical parameters of a newly designed open-cell foam. The purpouse for investigating artificial material is to approach the properties of the human bone in the case of its adequate replacement. Investigated material can be also used as an artificial bone to train surgical procedures and to improve the skills of the surgeons. Four sets of the foam with different chemical composition were subjected to an uniaxial quasi-static loading to describe basic mechanical behaviour of these samples. Based on these experiments, the stress-strain diagrams were created as a comparative tool including calculation of the effective Young’s modulus. The acquired knowledges will be used as input parameters of a follow-up study aimed at describing the morphology of presented structures and their response to mechanical experiments. A distortion effect of porosity on the results is not considered in this study.
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Využití optických metod pro určování deformací těles
Kováříková, Sabina ; Šebek, František (oponent) ; Návrat, Tomáš (vedoucí práce)
Bakalářská práce je zaměřena na využití metody digitální korelace obrazu při určování deformací těles. Obsahuje teoretické poznatky o dané metodě, ale také realizaci měření na vybraných tělesech. Cílem práce je srovnat hodnoty získané experimentálně metodou DIC s výpočty provedenými v programu Ansys Workbench. Součástí práce je seznámení s dalšími optickými metodami, využívanými k určování deformací těles a také rešerše softwarů, které je možné použít ke zpracování dat založených na metodě DIC.
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Mechanical analysis of scarf joint fastened using cylindrical wooden dowel
Tippner, J. ; Milch, J. ; Kunecký, Jiří ; Kloiber, Michal ; Brabec, M. ; Sebera, V.
Traditional all-wooden woodworking joints play an important role in the behaviour of timber structures. These joints are also widely used when historically valuable constructions are being reconstructed and the connections are usually the masterpieces that testify to the high carpentry skills and knowledges of the overall mechanical behaviour. Within historical timber structures traditional carpentry joints were used while wooden dowel fixed mutual position of elements. Main aim of this study was to contribute to knowledge base about prediction and analysis of the mechanical performance of frequently used scarf joints made from spruce wood fastened using oak dowels. The objectives were to determine the joints' slip moduli and load-carrying capacity by means of theoretical and experimental approaches, in next to assess the mechanical behaviour of dowels through experimental investigation, and finally to perform a strain analysis of dowels. For these purposes, the optical technique employing three-dimensional full-field digital image correlation was used. The experiments were done on the full-scale specimens meeting the requirements of European standards (EN 383 and EN 26891), which were made from Norway spruce (Picea abies L. Karst.) and English oak (Quercus robur L.). The mechanical load consisted in tensile parallel and perpendicular to grain direction within the main components. The results of this study showed good correlation between theoretical approach based on based on Beam on Elastic Foundation theory and European yield model theory and experimental observations.
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Deformation characteristics of chopped fibre composites subjected to quasi-static tensile loading
Šleichrt, J. ; Adorna, M. ; Neühauserová, M. ; Fenclová, N. ; Petráňová, Veronika
This work presents deformation behaviour of cost effective chopped fiber composites. Use of chopped fibre is advantageous for manufacturing however complex shape parts production technology could be challenging. Batches of samples with different fibres composition were subjected to uni-axial tensile loading to obtain overall materials properties and inspection of proper manufacturing based on local deformation inhomogeneities. Both crossbeam displacement and optical strain measurement were used for elastic characteristics evaluation. Deformation response was derived from full-field optical strain measurements based on digital image correlation method. Relatively large variation of mechanical properties testing of samples was found.
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Porovnání deformací stanovených metodou konečných prvků a optickým měřícím zařízením
Zajíček, Vít ; Hlavoň, Pavel (oponent) ; Vlk, Miloš (vedoucí práce)
Tato diplomová práce se zabývá srovnáním numerické simulace a optického měření deformací na turbínové skříni společnosti Honeywell. Numerický výpočet je proveden metodou konečných prvků a simuluje přechodové teplotní zatížení na měřeném tělese. Výsledkem je deformačně napjatostní stav tělesa způsobený teplotními gradienty. K verifikaci simulace je použita experimentální digitální korelační metoda VIC-3D. V práci jsou také uvedeny teoretické základy digitálních korelačních metod a tepelné analýzy.
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Experimental comparison of shear properties of FRP measured by ASTM methods
Ponížil, Tomáš ; Mališ, Michal (oponent) ; Urík, Tomáš (vedoucí práce)
Accurate shear stress-strain constitutive properties assessment of composite materials is essential for understanding the anisotropic material behaviour. Many test methods for assessment of the shear properties were developed. Because obtaining pure shear state in composites is difficult, it is provided only by few test methods. Use of digital image correlation as instrument for full field strain assessment to obtain constitutive shear properties from simple short beam shear test method is verified in this thesis. Results of this method are further compared to V-notched beam (Iosipescu) shear test.
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Mechanical properties of 3D auxetic structures produced by additive manufacturing
Jiroušek, O. ; Koudelka_ml., Petr ; Fíla, Tomáš
Three distinct auxetic structures were produced by direct 3D printing based on parametric CAD models. Mechanical properties of the structures were established by static compression tests where strain fields on the surface of the specimens was measured by non-contact optical method. Parametric finite element (FE) model of each structure was then subjected to a virtual compression test and mechanical properties obtained from the FE simulations were compared to the experimentally assessed values. After verification, the parametric FE models were used to establish relationships between various design parameters (porosity, rod thickness, internal angles, etc.) and overall mechanical properties (particularly stiffness).
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Determination of drift distortion in SEM micrographs acquired at different magnifications and acquisition times
Petráňová, Veronika ; Koudelka_ml., Petr ; Valach, Jaroslav
In the experimental mechanics wide variety of optical methods including measurement of deformation at reduced length scales using combination of computer vision and scanning electron microscopy (SEM) have been recently applied. One of suitable methods for in-plane measurement of displacements and deformations in the micrographs obtained by SEM is the 2D digital image correlation. In contrast to images obtained in visible spectrum by classical optical devices temporally-varying distortions known as drift distortion are present in the SEM micrographs. These distortions are caused by positional errors of electron beam during scanning process. Magnitude of this effect decreases with higher conductivity of the sample and is also influenced by magnification and scanning time. For this purpose measurement of distortion was performed on a series of micrographs of conductive samples acquired at different magnifications and acquisition times. Surface of each sample was covered with liquid silver to ensure adequate contrast pattern necessary for determination of distortion’s magnitude and distortion magnitudes were assessed.
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Investigation of deformation behaviour of aluminium foam under high-strain rate loading and comparison with conventional energy absorbing material
Zlámal, P. ; Fíla, Tomáš ; Jiroušek, O. ; Králík, V.
The aim of this study is proper description of stress-strain behaviour of the metal foam structure Alporas under high-strain rate loading. Stress-strain response of Alporas specimens is measured during an impact test using a drop tower experiment. Strain of the specimens is evaluated by two independent approaches: i) double numerical integration of acceleration data and ii) digital image correlation technique. Thus, experimental setup is equipped with triaxial accelerometer and high speed camera. Resulting stress-strain curves are compared with behaviour of polystyrene material samples (polystyrene material is commonly used as a shock absorber) obtained from the same testing procedure and with stress-strain function determined from Alporas quasi-static compression testing.
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