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The influence of specimen geometry on plasticity induced crack closure
Náhlík, Luboš ; Hutař, Pavel
The paper investigates the effect of in-plane constraint on plasticity induced crack closure under conditions of small scale yielding. The growth of a sharp straight crack in middle tension specimen (MT) and compact tension (CT) specimen, under constant amplitude of cyclic loading, was analyzed with help of finite element method. The material constitutive behavior was represented by a purely kinematic hardening law. Obtained results are discussed from point of view of the influence of T-stress on plasticity induced crack closure. Significant difference between opening values for CT and MT specimens was found under conditions of plane strain.
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Numerical analysis of a surface crack in protective layers
Šestáková, Lucie ; Majer, Zdeněk ; Náhlík, Luboš ; Knésl, Zdeněk
Two elastic plane strain problems relevant to the cracking of protective layers bonded to dissimilar semi-infinite substrate materials are solved. In the first case a crack initiated at the free surface of the layer and propagating within the film is considered and the influence of its original orientation on cracking mode of the layer is studied. The second problem is that of the crack in the layer oriented perpendicularly to the layer/substrate interface and its influence on a debonding of the layer/substrate system is analysed. In both cases the influence of elastic mismatch of both components on the crack behaviour is discussed. The results provide the details making it possible to solve practical problems connected with damage of bodies with protective layers.
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Účinek smykového namáhání, hrubozrnných částic a aditiv snižujících tření na tokové chování hustých popílkových suspenzí
Vlasák, Pavel ; Chára, Zdeněk ; Konfršt, Jiří
The dense fluidic ash-water mixtures are time dependent non-Newtonian slurry, their shearing results in the significant decrease of the pressure drops in the laminar region, also laminar/turbulent transition region was reached for lower flow velocity. Presence of bottom ash or chemical agent affects favourably the flow behaviour of dense fluidic fly ash-water mixtures. The paper is focussed on the experimental study of the effect of concentration, time and intensity of shearing and particle size distribution on the hydraulic gradient vs. the average velocity relationship in the laminar, transitional and turbulent regimes. The re-circulation pipe loop with smooth stainless steel pipes of the inner diameters D = 26.8 and 36 mm was used for measuring the ash-water mixtures flow parameters.
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2D numerický model dna kanálu utvářeného náhodně rozdělenými kulovitými částicemi
Kharlamov, Alexander
The paper deals with the saltation mode of bed load transport. The saltation process modelling consists of two parts – deterministic motion of the particle in fluid and stochastic process of its collision with bed, which is the stochastic part of a Monte-Carlo simulation. The channel bed is formed by spherical particles of non-uniform size, the distribution of the particles radiuses and the particle height is of Gaussian type. The numerical method of a bed forming and determination of collision coordinates and a collision angle is proposed.
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Výpočet funkcí parametrů saltačního procesu
Piatsevich, Siarhei ; Lukerchenko, Nikolay ; Chára, Zdeněk ; Vlasák, Pavel
The results of the 3D simulation of the solid spherical particles saltation in an open channel with rough bed are presented. The dependences of mean saltation length, mean saltation height, mean saltation velocity and mean deviation of angle of particle trajectories with respect to the downstream direction were studied and determined as the functions of the saltation process parameters, such as the flow shear velocity and the particle diameter.
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Modelování klasické námrazy na profilu křídla
Horák, V. ; Hoření, Bohumír
The paper presents the rime ice accretion prediction code. Model includes the calculation of a velocity distribution, droplet motion equations and detetrmination of a water mass flux impacting on the wing airfoil surface. Changing the airfoil shape is illustrated in compare of experimental results.
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Effect of ultrasound pulsations on suspension sedimentation
Suchánková, A. ; Kysela, Bohuš ; Chára, Zdeněk ; Ditl, P.
The paper presents results of a gravity settling of a model suspension. Experiments have been carried out for two configurations. The first experiment involved natural gravity settling; in the second case the ultrasound pulsations were introduced. Ultrasound field was provided by 20 kHz horn acting through a wall of settling vessel. Three kaolin suspensions of volume concentrations 3.8; 7.6; 11.4 % were used. It has been found that there is no significant influence of ultrasound pulsations on suspension settling.
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Zkušenosti se zaváděním výuky Solidworksu
Maxa, J. ; Neděla, Vilém
The world trend TPV tends complex solutions of the system from the from of a sketch to manufacture. In order to be prepared for this trend, the Universities are required to react to it. There is a system of courses described in the article which in forms the students about this methodology.
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