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Search Results: 1 - 10 of 554679 matches for " Fraňa K. "
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Lorentz forces caused by rotating magnetic field
Horáková K.,Fraňa K.
EPJ Web of Conferences , 2013, DOI: 10.1051/epjconf/20134501039
Abstract: Leading topic of this article is description of Lorentz forces in the container with cuboid shape. Inside of the container is an electrically conductive melt. Lorentz forces are caused by rotating magnetic field. Lorentz forces were calculated by analytic formula. This formula was derived for cylindrical container. Using this formula for cuboid container was assumed. Results were compared with Lorentz forces from CFD computing program NS-FEM3D. Areas of differences were recognized and displayed.
Modelling the concentration and dimensional changes in the structural constituents of vermicular graphite cast iron on cooling within the range of solidus-eutectoid temperature
W. Kapturkiewicz,A. A. BurbeIko,E. Fra
Archives of Foundry Engineering , 2008,
Abstract: A mathcmaricaI modcl md a simulation prognm havc bccn dcvclopd lo trace changcs in thc stnlcturc of W-C alloy on ctwliag hp111 ihcsolidus tcmpcraturc to thc !cmpcmtwrc of cutccloid tmsformation. A simplitid schematic rcprcscntatinn OF thc proccss can hc rcrcrml to thccast iron with vcrmicular gnphirc. Thc numerical cxprirncnts using the ncwly dcvcl~pcd program havc proved a significant crfcct of thccooling conditions and stmcturc rcfincmcnt dcgm (~hcdi mensions of austenitc) on thc concentration ficld in nustcnilc and. conscr~ucntlyo. nthc dimensional changes of gmphitc within thc cxamincd cooling range. Thc dcvclopcd mcrhds of rnodclling rhc proccss of transrormntioncnablc including thc proccdurc into a cornplcx softwm o p t i n g in a system reproducing in rcal mnnncr the cxt ing configun~ion. whilc thcohtaincd rcsuIts indicate an imponant cffcct of thcrrnophysicaI parameters md hcat transfcr proccss on final aliay an~cturc
Mathematical and numerical model of directional solidification including initial and terminal transients of the process
W. Kapturkiewicz,A. A. Burbelko,E. Fra
Archives of Foundry Engineering , 2008,
Abstract: The, developed in this study, simple model and numerical solution of diffusion growth of the solid phase under the conditions of directional solidification allow for the effect of constituent diffusion in both liquid and solid phase and assume the process run in which (like in reality) the preset parameter is the velocity of sample (pulling velocity) at a preset temperature gradient. The solid/liquid interface velocity is not the process parameter (like it is in numerous other solutions proposed so far) but a function of this process. The effect of convection outside the diffusion layer has been included in mass balance under the assumption that in the zone of convection the mixing is complete. The above assumptions enabled solving the kinetics of growth of the solid phase (along with the diffusion field in solid and liquid phase) under the conditions of diffusion well reflecting the process run starting with the initial transient state, going through the steady state period in central part of the casting, and ending in a terminal transient state. In the numerical solution obtained by the finite difference method with variable grid dimensions, the error of the mass control balance over the whole process range was 1 - 2 %.
La iniciativa comunitaria leader en el marco teórico de la política agraria
María del Mar Pérez Fra
Revista Galega de Economía , 2004,
Abstract: La iniciativa comunitaria LEADER es un programa público dise ado desde una perspectiva de actuación local que tiene en el medio rural su ámbito de intervención y en la consecución del desarrollo integral de estas áreas su objetivo declarado. Esta iniciativa surge en un momento de cambio de paradigma, en el que las políticas tradicionales de apoyo al desa-rrollo de corte sectorial pasan a ser sustituidas por otras formas de intervención en el espacio. El objetivo de este trabajo es 1) Realizar una revisión crítica de los conceptos relacionados con la cuestión del desarrollo de áreas rurales con el fin de clarificar el contexto teórico en el que se inserta la iniciativa LEADER y situarla en el marco de las políticas europeias; 2) Aportar elemen-tos de discusión sobre la aplicabilidad de su enfoque de tal modo que constituyan una base a partir de la cual se pueda testar la influencia real que tuvo en las áreas de aplicación.
Fabrication of in situ composite layer on cast steel
E. Fra,E. Olejnik,A. Janas,A. Kolbus
Archives of Foundry Engineering , 2010,
Abstract: The study describes the technology of fabrication of composite layers in cast steel reinforced with titanium carbides. In the process under discussion, the reinforcing TiC phase is formed in situ from the substrates deposited on mould cavity, where the said substrates under the effect of heat supplied by molten metal poured into mould (1823K) undergo a synthesis in the SHS reaction. An outcome of this process is the formation, within the casting surface, of a layer from 550 to 1200μm thick. Carbides produced in this synthesis have the size from 0,5 to 20μm and a non-typical spheroidal shape. The hardness of the produced layer examined in function of the distance from the casting surface is from 700 to 1134 HV, and is determined by volume fraction of the reinforcing TiC phase. To better document the type of microstructure obtained in the produced material, metallographic and structural examinations were carried out using the method of scanning electron microscopy (SEM), X-ray microanalysis (EDS/EDX), and phase analysis (XRD). To check the mechanical properties of the examined material, hardness was measured by the Vickers test.
The morphology of TiC carbides produced in surface layers of carbon steel castings
E. Fra,E. Olejnik,A. Janas,A. Kolbus
Archives of Foundry Engineering , 2010,
Abstract: The study presents the results of investigations of the process of in situ fabrication of TiC carbides in a surface layer of carbon steelcasting. Carbides were produced by SHS reaction taking place between the substrates deposited on mould surface and cast molten alloy.The thickness of the obtained layer was up to 700 μm, and the size of carbides was comprised in a range of 1-10μm. During alloy solidification in mould, a thermal analysis was carried out; its results were used in evaluation of the morphology of the obtained titanium carbides. It has been found that, at the moment of reaction, the temperature of the reaction layer and the temperature of the central part of casting differed by 93 K. This difference has changed the morphology of the obtained carbides. In the region of reaction layer, where the temperature amounted to 1955 K, the crystals assumed an oval and coagulated shape, while at the layer-casting interface, TiC carbides in the form of cuboids were formed.
Concurrent growth of two phases in 2D space
A.A. Burbelko,W. Kapturkiewicz,E. Fra
Archives of Foundry Engineering , 2008,
Abstract: The kinetics of phase transformations has been studied within the framework of the Kolmogorov-Johnson-Mehl-Avrami (KJMA) theory. This theory accurately describes only the parallel growth of anisotropic products with identical convex shape. The identical growth velocity distribution at an interface is the indispensable condition for the above restriction. The proposed earlier extension of KJMA theory (statistical theory of the screened growth) enlarges the scope of its application and eliminates the above limitation. The results of the application of this extension were compared with the results obtained during modelling of the concurrent growth of the two types of circular particles on a plane, where the said particles were characterised by different growth rates and modelling was carried out by the method of cellular automata (CA).
Multiphysics and multiscale modelling of ductile cast iron solidification
D. Gurgul,A. Burbelko,E. Fra,E. Guzik
Archives of Foundry Engineering , 2010,
Abstract: The presented model of ductile cast iron solidification is a typical sample of multiphysics and multiscale engineering system. This model takes into consideration the different time and spatial scales of accounted phenomenon of microstructure formation: heat diffusion, components mass diffusion in the liquid and solid phases, thermodynamic of phase transformation under the condition of inhomogeneous chemical composition of growing and vanishing phases, phase interface kinetics and grains nucleation.The results of two-dimensional modelling of the microstructure formation in the ductile cast iron (so called - Ductile Iron - DI) are pre-sented. The cellular automaton model (CA) was used for the simulation. Six states of CA cells were adopted to three phases above men-tioned (liquid, austenite and graphite) and to three two-phase interfaces. For the modelling of concentration and temperature fields the numerical solution was used. The parabolic nonlinear differential equa-tions with a source term were solved by using the finite difference method and explicit scheme. The overlapping lattices with the same spatial step were used for the concentration field modelling and for the CA. The time scale of the temperature field for this lattice is about 104 times shorter. Due to above reasons the another lattice was used with a multiple spatial step and the same time step.
E. Fra,A. Janas,E. Olejnik,M. Kawalec
Archives of Foundry Engineering , 2010,
Abstract: The study presents the results of microstructural examinations of the Ni-Al-C alloy forming a natural Ni3Al/C composite, in which the precipitates of graphite are acting as a lubricating, slip phase. Different forms of graphite were described, starting with the fibrous shapes and ending in spheroidal forms, identical with the spheroidal graphite present in cast iron. The morphologies of graphite precipitates in the Ni3Al phase were compared to similar precipitates observed in ferrous alloys with high carbon content.
Cellular automata modeling of cooperative eutectic growth
A. Burbelko,D. Gurgul,E. Fra,E. Olejnik
Archives of Foundry Engineering , 2010,
Abstract: The model and results of the 2D simulation of the cooperative growth of two phases in the lamellar eutectic are presented. The pro-posed model takes into account heat transfer, components diffusion and nonstationary concentration distribution in the liquid and solid phases, non-equlibrium nature of the phase transformation and kinetics of the growth, influence of the surface energy and interface curva-ture on the conditions of the thermodynamic equilibrium. For the determination of the phase interface shape the Cellular Automata tech-nique (CA) was used. For the calculation of temperature and concentration distribution the numerical solution of the Fourier equation was used. The partial differential equations were solved by Finite Differences Method (FDM). The spatial position and cell sizes of CA lattice and FDM mesh are equal.Proposed model can predict the steady state growth with a constant interlamellar spacing in the regular plate eutectic, as well as some transient processes that bring to the changes of that parameters. Obtained simulation data show the solid-liquid interface changes result in the termination of lamella and enlargement of interlamellar spacing. Another simulation results illustrate a pocket formation in the center of one phase that forestalls nucleation (or intergrowth) of the new lamellae of another phase. The data of the solidification study of the transparent material (CBr4 – 8,4% C2Cl6) obtained in the thin layer demonstrate the qualita-tive agreement of the simulation.
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