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Impact of chemical corrosion on mechanical characteristics of wood
Frankl, Jiří ; Kloiber, Michal ; Drdácký, Miloš ; Kučerová, I.
The contribution is dedicated to the problem of chemical corrosion of surface layers of wood in buildings, caused by reaction of chemical substances contained in formerly used chemical anti-fire agents, applied by spraying or coating on wooden construction elements. Findings discovered during survey of buildings and laboratory methods (mechanical tests) of testing of impact of damage on mechanical characteristics of wood and wooden construction elements are presented in the poster.
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The changes in compression strength of wood along and across grain caused by an impact of damage to wood by wood-damaging fungi
Frankl, Jiří
The contribution is dedicated to monitoring the effect of time of impact of wood-damaging fungi on mechanical characteristics of spruce wood. Results of mechanical tests are presented in the article - compression strength along grain and compression strength across grain in tangential direction. The tests were carried out on standard samples 20x20x30 mm. The testing samples were exposed, in ideal growth conditions for variable times (5-60 days), to impact of wood-damaging fungi. Serpula lacrymans (wood-damaging fungi with brown, dry-decay) and Trametes versicolor (wood-damaging fungi with white, corrosive decay) were selected for the test.
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Je logaritmická časová derivace jednoduše Zarembova-Jaumannova derivace?
Fiala, Zdeněk
The paper raises a question whether the logarithmic time derivative, expressed in specific coordinate system, is the Zaremba-Jaumann time derivative, and if not why. In fact, it has been already proved that the Z-J derivative represents the geometrically consistent linearization of tensor fields along deformation process in terms of the covariant derivative in the space of right Cauchy-Green deformation tensors C.
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Výzkum fázově spouštěných vírů v impaktním proudění
Tesař, Václav ; Něnička, Václav
Impinging jets can transfer the highest achievable thermal flux into (or out from) solid bodies. The transport is significantly influenced by complex and so far not fully understood vortical structures that develop due to hydrodynamic instability. This contribution describes experiments with visualisation of impinging air jets in which periodic formation of vortices was triggered by azimuthal travelling waves generated in nozzle exit - and was phase-synchronised with the camera. Visualisation was by laser light scattered from water mist particles added to the supplied air. The instability structures were identified in the images by using their coherence.
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EXTRACTING INFORMATION ABOUT COHERENCE IN JET FLOWS
Tesař, Václav ; Něnička, Václav ; Šonský, Jiří
Several alternative approaches to processing jet flow visualization images were recently introduced by the authors. Common feature is processing a sequence of 2D images to detect presence and evaluate development dynamics of 3D vortical structures, which are recognised as regions that differ from the uncorrelated turbulent background in the processed pictures by their high negative values of correlation coefficient.
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Zjišťování mikrostrukturálních vlastností acetabula lidské pánve pomocí mikro-CT
Kytýř, Daniel ; Jiroušek, Ondřej ; Vavřík, Daniel
The paper deals with microstructure investigation of trabecular bone in acetabular region. Trabecular bone microstructure is the main factor of the bone quality and mechanical propertites at macroscopic level. Data from high resolution micro Computed Tomography can be used to reconstruct the complex geometry of the trabecular bone inner structure and interface between bone and implant. The data are usable as for micro-FE modeling as well as for experimental loading tests evaluation.
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TRAVELLING WAVES IN ROTATIONAL MACHINES
Půst, Ladislav ; Pešek, Luděk
This paper is concerned with vibrations of stationary or rotating disk as a simplified model of real bladed turbine disk. Two types of disks are investigated: perfect rotational disk with the same dynamic properties in all radial directions and imperfect disk having different dynamic properties in two independent modes of vibration. Presented study is first part of theoretical analysis intended as a background for evaluation method used in experimental research of vibrations of bladed disk in real rotational machines or their models.
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Porovnání numerické simulace tlaku na povrchu třepetajícího se profilu s experimentem v aerodynamickém tunelu
Horáček, Jaromír ; Sváček, Petr ; Vlček, Václav ; Feistauer, M.
The paper compares original experimental results with numerical solution of a 2D aeroelastic problem. The incompressible turbulent flow over a freely vibrating airfoil, with two degrees of freedom for rotation and translation with large vibration amplitudes, is described by the Reynolds averaged Navier Stokes (RANS) equations written in Arbitrary Lagrangian-Eulerian (ALE) form. The Spalart-Allmaras turbulence model is used and the flow is solved by the stabilized FEM. The numerical results are compared with the optical measurements of flow field araund a fluttering doublecircular arc (DCA) 18% profile elastcally supported in a subsonic wind tunnel. The interferometry method was used for airflow visualization in different phases of the profile motion. The numerical resulults for the pressure on the profile surface are in good agreement with the measurement.
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