Pavol Koštial

The Study of Electrical Transport in Rubber Blends Filled by Single Wall Carbon Nanotubes

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 .

Advanced Fillers Enhancing Thermal and Mechanical Properties of Rubber Blends

In the paper we present measurements of transport physical parameters such as thermal conductivity, diffusivity and specific heat capacity and dc electrical conductivity as well as the mechanical values E*, tg δ for rubber compounds filled by different ratio of silica - carbon black fillers. From presented results it is possible to see that proper filler concentration (rubber blend - silica - carbon black) rising all thermal parameters as well as mechanical properties represented by complex Young’s modulus and so, maintains the good mechanical parameters of the blend and finally it also lowers the electrical resistance. All trends are favourable for the improvement of useful rubber blends properties.

Artificial Neural Networks Application in Modal Analysis of Tires

Abstract The paper deals with the application of artificial neural networks (ANN) to tires’ own frequency (OF) prediction depending on a tire construction. Experimental data of OF were obtained by electronic speckle pattern interferometry (ESPI). A very good conformity of both experimental and predicted data sets is presented here. The presented ANN method applied to ESPI experimental data can effectively help designers to optimize dimensions of tires from the point of view of their noise.

A New Procedure for the Determination of the Main Technology Parameters of Rolling Mills

Nowadays, approximately 90–95 % of metals are processed by cold rolling. There has been a substantial increase in demand for utility properties as well as for reducing production costs. These objectives cannot be achieved without a high degree of automation, control and monitoring throughout the manufacturing process. These qualitative changes require rather deep and comprehensive theoretical and metallurgical–technological knowledge of operators in the field of design, research and production of rolled steel sheets, which is needed for further development in rolling steel. A continuous quality control of material and surface during the rolling process is a part of these tasks and is associated with providing the full automation of rolling mills. Starting from theoretical foundations, we have developed a new procedure for the determination of main technology parameters of a rolling mill. The main difference between our proposal and current methods of calculation is as follows. Our proposal is based on the knowledge of deformation properties of materials and continuous processes of stress-deformation state and on the knowledge of reductions in different stages of rolling. Current procedures are on the contrary based on static calculations using the geometry of the system—working roll and instantaneous sheet metal thickness in a gap between the rollers. In doing so, the calculations almost ignore the real stress—deformation properties of rolled metal sheets, optimal transmission rate of deformation in the material at the given speeds of rollers and the given main rolling force. We are concerned with the optimum balanced system: main rolling force—rolling speeds, or transmission rate of deformation in the material. This procedure allows us to achieve a significant increase in operational performance as well as in rolling process quality.

Comparative Measurements of the Thermal Properties of Solid Materials on a New Device and Using a New Non-Stationary Method

The aim of the publication is the comparative measurements of changes in temperature of the significant material coefficient - thermal conductivity for newly developed construction materials (lightweight concrete). The aim is met by using a newly proposed method and a newly developed device by the approximation modelling of the temperature dependence of the thermal conductivity coefficient of the new composites and also the interpretation of measurement results in the context of optimally desired characteristics of thermal insulation concrete. Construction materials for residential buildings should have good thermal insulation properties, i.e. relatively low coefficients of thermal conductivity. With regard to the relatively most important property of concrete – strength, however, the reduction in thermal conductivity of concrete is limited. Thermal conductivity of concrete can be reduced very effectively by increasing its porosity; on the other hand, by increasing the porosity, the strength of concrete is significantly reduced. The publication, therefore, compares the results of temperature dependences of thermal conductivity for three newly designed concretes, namely in the context of their compressive strength.

Lumped Capacitance Model in Thermal Analysis of Solid Materials

The paper is devoted to the presentation of a method for measurement of thermal conductivity k, specific heat capacity cp and thermal diffusivity α applying the lumped capacitance model (LCM) as a special case of Newtons model of cooling. At the specific experimental conditions resulting from the theoretical analysis of the used model, we present relatively very precise method for experimental determination of all three above mentioned thermal parameters for materials with different thermal transport properties. The input experimental data provide a cooling curve of the tested material obtained in special experimental arrangement. The evaluation of experimental data is realized by software the fundamental features of which are presented here. The statistical analysis of experimental data was performed (99% confidence interval P99).

An innovative method of generating current and thermoelectric equipment for its realization

The paper assesses an innovative thermoelectric device used to generate a current by the conversion of thermal energy into electrical energy. The device has been created and verified. Until now, the efficiency of conventional thermoelectric batteries is for technical practice not sufficiently appreciated, because it does not exceed 3 %. A necessary condition needed for the implementation of the Seebeck thermoelectric effect is a sufficient and stable source of heat that provides an optimum temperature difference, but there are two other sufficient conditions for a significant increase in efficiency of thermoelectric batteries. These are concerned with the development of new materials for thermoelectric batteries and with the development of new construction of thermoelectric batteries.

Application of Artificial Neural Networks in Chosen Glass Laminates Properties Prediction

The article deals with applications of the artificial neural networks at the evaluation of chosen material’s properties (sample thickness, sample shape) measured by electronic speckle pattern interferometry. We have investigated the dependence of the generated mode frequency as a function of sample thickness as well as the sample shape of glass laminate samples. Obtained experimental results for differently shaped glass laminate samples are compared with those of artificial neural networks and finite element method simulation. The coincidence of both experimental and simulated results is very good.

Recycling Polyurethane Foam and its Use as Filler in Renovation Mortar with Thermal Insulating Effect

Renovation mortars with thermal insulating effect are characterized by thermal conductivity λ, within the range from 0.060 to 0.200 W·m−2·K−1. To achieve such low values of thermal conductivity coefficient of composite mortar, it is essential that the structure of this composite contains a sufficient percentage of pores filled with air and has a low volume weight. Lightweight fillers, mostly crushed or crumbled polystyrene, expanded clays, expanded obsidian or volcanic glasses, for example perlite or vermiculite, are used to achieve this effect. The article presents the results of the basic research, where polyurethane foam at the end of its life cycle, in the form of crushed polyurethane with a maximum grain size of 4 mm, is used as new filler for renovation mortars with thermal insulating effect. It describes the current methods of recycling polyurethane foam, the physical and mechanical properties of experimental mixtures of renovation mortar with thermal insulating effect and the method of its application to masonry. This is a new way of utilization of polyurethane foam at the end of its life cycle in the segment of renovation mortars with thermal insulating effect.

Modal Analysis – Measurements versus FEM and Artificial Neural Networks Simulation

The article deals with the experimental modal analysis of glass laminates plates with different shape and these results are compared with those obtained by applications of the artificial neural networks (ANN) and finite element method (FEM) simulation. We have investigated the dependence of the generated mode frequency as a function of sample thickness as well as the sample shape (rounding) of glass laminate samples. The coincidence of both experimental and simulated results is very good.