Acta Polytechnica. 2015, vol. 55, no. 5http://hdl.handle.net/10467/666112021-06-18T13:04:58Z2021-06-18T13:04:58ZANALYSIS OF MECHANICAL PROPERTIES OF HYDROTHERMALLY CURED HIGH STRENGTH CEMENT MATRIX FOR TEXTILE REINFORCED CONCRETEHolčapek , OndřejVogel , FilipKonvalinka , Petrhttp://hdl.handle.net/10467/672242017-02-09T10:01:51Z2015-01-01T00:00:00ZANALYSIS OF MECHANICAL PROPERTIES OF HYDROTHERMALLY CURED HIGH STRENGTH CEMENT MATRIX FOR TEXTILE REINFORCED CONCRETE
Holčapek , Ondřej; Vogel , Filip; Konvalinka , Petr
The main objective of this article is to describe the influence of hydrothermal curing conditions in an autoclave device (different pressure and temperature), which took place at various ages of a fresh mixture (cement matrix – CM, and fibre-reinforced cement matrix – FRCM), on textile reinforced concrete production. The positive influence of autoclaving has been evaluated through the results of physical and mechanical testing – compressive strength, flexural strength, bulk density and dynamic modulus of elasticity, which have been measured on specimens with the following dimensions: 40×40×160mm3. In addition, it has been found that increasing the pressure and temperature resulted in higher values of measured characteristics. The results indicate that the most suitable surrounding conditions are 0.6MPa, and 165 °C at the age of 21 hours; the final compressive strength of cement matrix is 134.3MPa and its flexural strength is 25.9MPa (standard cured samples achieve 114.6MPa and 15.7MPa). Hydrothermal curing is even more effective for cement matrix reinforced by steel fibres (for example, the compressive strength can reach 177.5MPa, while laboratory-cured samples achieve a compressive strength of 108.5MPa).
2015-01-01T00:00:00ZA COMPACTING PROCESS OF THE EN AW 6060 ALLOYDragošek , LukášKociško , RóbertKováčová , AndreaBidulsky , RobertŠkrobian , Milanhttp://hdl.handle.net/10467/672232017-02-09T10:01:48Z2015-01-01T00:00:00ZA COMPACTING PROCESS OF THE EN AW 6060 ALLOY
Dragošek , Lukáš; Kociško , Róbert; Kováčová , Andrea; Bidulsky , Robert; Škrobian , Milan
This study reports on an investigation of factors affect the process of compacting Al chips which are used to direct scrap processing through the forward extrusion method. EN AW 6060 chips of different geometry and types were mainly used as the experimental material. The chips were compacted in a die with a vertical channel (10.3mm in diameter). To provide a range of processing conditions, three different weights were selected and compacting was performed under five, different compacting pressures. The movement of the chips within the die during compacting was analysed through numerical simulations using Deform 2D software. Study of the compacting process optimal parameters for increasing the density and enhancing the density distribution were defined. The results from our study clearly show that optimal conditions are obtained when the proportion of D/h is 1/1.1. Moreover, it was recognized that in the process of small chips compacting, there was obtained lower density than in the case of large chips.
2015-01-01T00:00:00ZUNSTEADY FLOW OF THIXOTROPIC COLLAGEN SUBSTANCE IN PIPESŽitný , RudolfLandfeld , AlešSkočilas , JanŠtancl , JaromírFlegl , VlastimilHouška , Milanhttp://hdl.handle.net/10467/672222017-02-09T10:01:39Z2015-01-01T00:00:00ZUNSTEADY FLOW OF THIXOTROPIC COLLAGEN SUBSTANCE IN PIPES
Žitný , Rudolf; Landfeld , Aleš; Skočilas , Jan; Štancl , Jaromír; Flegl , Vlastimil; Houška , Milan
Unsteady flow of thixotropic liquid in pipes is solved by 1D and 2D numerical methods using the same constitutive equation — the only difference is in the radial diffusion of the structural parameter. Comparison shows that the neglected diffusion of structural parameter implicates a much stronger effect of thixotropy. The models are applied for analysis of the observed hysteresis of hydraulic characteristic of collagen.
2015-01-01T00:00:00ZCFD ANALYSIS OF THE SPACER GRIDS AND MIXING VANES EFFECT ON THE FLOW IN THE CHOSEN PART OF THE TVSAT FUEL ASSEMBLYJuklíček , JakubŽelezný , Václavhttp://hdl.handle.net/10467/672212017-02-09T10:01:36Z2015-01-01T00:00:00ZCFD ANALYSIS OF THE SPACER GRIDS AND MIXING VANES EFFECT ON THE FLOW IN THE CHOSEN PART OF THE TVSAT FUEL ASSEMBLY
Juklíček , Jakub; Železný , Václav
CFD is a promising and widely spread tool for a flow simulation in nuclear reactor fuel assemblies. One of the limiting factors is the complicated geometry of a spacer grid. It leads to the computational mesh with high number of cells and with possibility of decreasing quality. Therefore an approach to simulate the flow as precisely as possible and simultaneously in a reasonable computational expense has to be chosen. The goal of the following CFD analysis is to obtain the detailed velocity field in a precise geometry of a chosen part of the TVSA-T fuel assembly. This kind of simulation provides data for comparison that can be applied in many situations, for instance, for comparison with simulations when a porous media boundary condition is applied as a replacement of the spacer grid.TVSA-T fuel assembly is equipped with combined spacer grids. Combined spacer grid has two functions - support of the fuel pins as a part of assembly skeleton and mixing vanes which ensures coolant mixing. The support part is geometrically very complicated and it is impossible to prepare a good quality computational mesh there. It is also difficult to create a mesh in the support part and the mixing part joint area because of inaccurate connection between these two parts.A representative part of the TVSA-T fuel assembly with a combined spacer grid segment was chosen to perform the CFD simulation. Some inevitable geometry simplifications of the spacer grid geometry were performed. These simplifications were as insignificant as possible to preserve the flow character and to make it possible to prepare a quality mesh at the same time.Steady state CFD simulation was performed with k-ε realizable turbulence model. Heat transfer was not simulated and only velocity field was investigated. Detailed flow characterization which was obtained from this calculation shown, that mixing vanes already affect the flow in the support part of the grid thanks to suction effect. Vortex structures disappear approximately 50 mm behind the mixing vanes but the basic spiral character of the flow is preserved in the whole area between two following spacer grids.
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