Papers by Author: Zora Jančíková

Abstract: This paper aims to study the cooling of a solid body. An analytical analysis of a solid body cooling in different regimes is presented, such as a simple first order exponential model, a modified exponential model, a generalized exponential model and the so-called regular temperature regime. The analysis also includes the influence of the dynamically changing relaxation time and we also present the solution of the nonlinear heat equation.

Abstract: In this paper, we present some distinguished methods of the digital thermograms software treatment which allows the visualization of hidden defects in glass fabric laminates, which are not usually visible in standard raw thermograms. The results of the software treatment are tested on artificial defects in glass laminate plates.

Abstract: Measuring of thermal distribution in certain material was done in Matlab. Obtained data are processed and displayed in fully 3D environment (virtual reality) using X3D. Paper deals with data processing and conversion from Matlab into X3D. Further development of visualization is discussed too – visualization of thermal gradient, Integration of measured a visualized data into real object or technological process visualization. The aim of this topic is to present information about discontinuities in solid materials.

Abstract: The paper deals with modeling and simulation of methane flow through the porous environment using the CFD (Computational Fluid Dynamics) software Fluent. We compare three situations, which can occur in areas, where mining activities were closed few years ago, in this article. First case is modeling of methane flow through the rocks. Second event is situation where the thin water layer is situated at the surface. The last one is occurrence of groundwater. The article responds to the need for knowledge of natural processes in the given area and it follows our previous papers [1], [2]. Software Gambit was used for creating a geometric model of the working area, for modeling the flow of gas it was used CFD software, Fluent from ANSYS, Inc..

Abstract: Contribution of the work consists in creation of a mathematical model (algorithm) for prediction of technological parameters of the two-high rolling stand DUO 210 Sva and Q110 at change of the absolute reduction Δh, for example for a deep-drawing steel and of the brand KOHAL grade 697 and low carbon steel, as well as generally speaking for any rolled material. It is possible to identify and predict on the basis of this algorithm an instant state of surface topography in respect to variable technological conditions. On this basis it is then possible to calculate and plot individual main technological parameters.

Abstract: The presented work is devoted to the investigation of the influence of single wall carbon nanotubes (SWCNT) on the thermal and mechanical properties of rubber blends. The materials under investigation were rubber blends filled by carbon black (CB-labelled as standard or S) or a mixture of CB with single wall carbon nanotubes (0.6 wt.% of SWCNT). The thermal parameters of the rubber samples were measured on the basis of an exponential model of a cooling body (developed in a lumped capacity model). From the measured cooling curve of the sample after its deformation, the specific heat capacity c_p [J/kg/, thermal diffusivity α [m²/ and thermal conductivity k [W/m/K] were measured. The increase of α and k was observed for rubber blends filled with a mixture of CB and SWCNT. The complex thermo mechanical analyzer (CTMA) was used for determination of thermal and mechanical parameters. The static Youngs modulus shows an immense increase after SWCNT addition. The dynamic Youngs modulus also shows an increase after SWCNT introduction. A simultaneous tgδ decrease caused by SWCNT presence is observed in this case.

Abstract: The paper deals with the electrical and mechanical properties of rubber blends filled by single wall carbon nanotubes (SWCNT-0,6 weight %). We have investigated the alternating current resistivity (ACR), real and imaginary part of dielectric constant,and loss factor .The addition of (SWCNT) to a rubber blend decreases ACR and increases constants ,and loss factor .

Abstract: The paper is devoted to the study of thermal, as well as mechanical properties of polyurethane samples (PU) filled by carbon black (CB), graphite (G) and MWCNT(CNT). Thermal conductivity k(W.m^-1.K^-1), specific heat capacity c_p(J.kg^-1.K^-1) and thermal diffusivity a(mm².s^-1) were measured by the impulse method. An increase of all the above mentioned thermal parameters after addition of fillers under investigation was observed. The dc electrical conductivity drastically increases from PUPU+CBPU+GPU+CNT.

Abstract: The contribution deals with the use of artificial neural networks for prediction of corrosion loss of structural carbon steel. Nowadays there is certain chance to predict a corrosion loss of materials by artificial intelligence methods, especially by neural networks. A model of neural network for prediction of corrosion loss of structural carbon steel based on the input environmental parameters affecting the corrosion of metals in the atmospheric environment (temperature, relative humidity, air pollution by sulphur dioxide and the exposition time) was created. The model enables to predict corrosion loss of steel with a sufficiently small error.

Abstract: Three samples of 10GN2MFA steel were thermally treated at quenching temperatures equal to 900°C, 1000°C and 1100°C, and temperature of the tempering was 670°C. Thermo-physical properties of the steel were modelled by lumped capacity model. The sample was mechanically stressed under yield strength and then the cooling curve of stressed material on air was measured. The heat transfer through grips was taken into account. Thermo-physical properties were obtained by parametric fitting of time-temperature data obtained from cooling curve. Both thermal diffusivity and thermal conductivity increase with the quenching temperature. Specific heat capacity of steel samples after thermal treatment does not change significantly. All the measured thermo-physical parameters were in good agreement with the table values for low carbon Ni steels.