Pavel Koštial

The Chosen Aspects of Materials and Construction Influence on the Tire Safety

Security of the road transport depends on the quality of basic and applied research concerning materials and internal construction of tires. The design shapes and material properties characterized by low hysteretic losses as well as a construction have an influence on the driving comfort, adhesion, wear resistance and fatigue resistance. Thick fibre reinforced composites are used extensively in rubber products such as tires and conveyer belts. Generally, the reinforced parts of rubber products on a sub macroscopic level are highly heterogeneous and anisotropic because they are composed of rubber compounds, and textile and steel cords. Rubber compounds consist of natural or synthetic rubber, carbon black, curing agents, cure accelerators, plasticizers, protective agents and other ingredients.

On Experimental Thermal Analysis of Solid Materials

Abstract The paper is devoted to the presentation of a method for measurement of thermal conductivity k, specific heat capacity cp, and thermal diffusivity applying the lumped capacitance model (LCM) as a special case of Newton’s model of cooling. At the specific experimental conditions resulting from the theoretical analysis of the used model, we present a 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. 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.

Weibull distribution application on temperature dependence of polyurethane storage modulus

Abstract In this paper, a stiffness–temperature model based on Weibull statistics was applied to quantitatively describe changes in the storage modulus of thermoplastic polyurethane over a wide range of temperature. The variation of the storage modulus with temperature was obtained from dynamic mechanical analysis tests across transition temperatures. Both the physical and statistical parameters of the applied model were estimated in the process of parametric fitting of the model to the storage modulus versus a temperature curve by using a trust region algorithm for a robust nonlinear least squares method. Good agreement between the modeled and experimental data has been found over the entire investigated temperature range, including all observed relaxation transitions.

Emission Distribution and Regulation of Local Heat Source

Pollutants can be classified according to their chemical composition, harmfulness, hazardousness, risk rate and toxicity. The most monitored pollutants are particulate matter (PM), carbon monoxide (CO), nitrogen oxide (NOx), sulfur dioxide (SO2), organic substances which are in the form of gaseous phase in waste gases expressed as total organic carbon, dibenzodioxins and dibenzofurans [1-3]. Other pollutants are divided into several groups and subgroups, such as substances with carcinogenic effects (asbestos, Co, Cd, Be, Ni, As, Cr, dioxins, etc.), solid inorganic contaminants (He, Se, animony, and others) and inorganic pollutants in the form of gases (HCl, HF, ammonia, etc.), organic gases and vapours (phenol, toluene, acetone and many others) and gases causing the greenhouse effect (CO2, methane, N2O, hydrofluorocarbons, etc.). The term particulate matter, or suspended matter refers to the emissions of a wide range of wind drift solids and liquid particles of material in size from several nanometres up to 0.5 mm, which stay in the air for some time. This is a major component of atmospheric pollution, which contributes to harmful effects not only on human health but also on intensity of materials degradation. Into the atmosphere, where we can meet them, regardless of particle size and chemical composition, in the form of a complex heterogeneous mixture, they are released from burning fossil fuels and also from burning biomass-based fuels, while domestic heating accounts for about 16% of the total production of particulate matter [4,5,6]. This percentage represents a degree of imperfect combustion of fuels used in local heating. Emissions from incomplete combustion are undesirable from the point of view of human health as well as from the economic point of view, because this leads to the degradation of materials. Nevertheless, since fuel combustion is necessary for the society, emissions are still produced. This paper presents an automated method of perfect combustion control in local heating in order to minimize emissions being produced.

Surface Quality Control of Materials Being Cut by Laser with Respect to Corrosion Resistance

In the field of laser cutting, the research area is oriented mainly to understanding of the mechanism of removal, as well as to the combination of factors entering the process. This process of disintegration of materials presents a problem of analytical approximation, elaboration, and description [1 - . Compared with previous approach to a solution, we have chosen our own way and we focus on mechanical respectively stress-strain parameters of the material being cut and the mechanical balance system: material properties tool properties deformation properties. We shall present here the basic forms of prediction equations for calculating the roughness of cutting walls, as well as other equations which were derived by modifying the basic equations for different application purposes, especially to calculate the optimum traverse speed vpopt, optimal laser performance Wlasopt and technologically important ratio INDvpwopt = vpopt/Wlasopt. These contain easily available input variables for substitution. The basic forms, including the modified forms are aimed at predicting the quality of cut with its depth limits. The paper presents the method of optimization of the ratio between the traverse speed vpand laser power Wlas which minimizes the final surface roughness after cutting with a direct impact on corrosion resistance of materials.

Artificial Neural Networks Prediction of Rubber Mechanical Properties in Aged and Nonaged State

Artificial neural networks (ANN) have been used for characterization of rubber blend mixtures ageing and for prediction of mechanical properties according to chemical composition. Strength Rm and modulus M100 have been evaluated. The ANN application was tested by statistical function RMSE (root mean square error) and R2 (coefficient of determination) which value for all predictions was higher than 0.93.

A New Approach to Surface Tension According to the Surface Topographical Features in Laser Cutting Technology

Laser - cut quality is mainly characterized by a degree of accuracy in shape, size and also by surface layer conditions after cutting associated with surface roughness. An experimental determination of surface tension (or tensor components) of clean metal surfaces is very difficult and there is no direct method for its measurement. Attention was paid to numerical derivation of surface tensions according to the surface topographical features in laser cutting technology. The surface tensions and temperature dependencies of several metallic materials have been determined and confirmed by data obtained from the literature. It was found to be in very good agreement between our results and data from different sources in the literature.

Modifications of Pyrolysis Boilers to Reduce Harmful Flue Gas Emissions

In addition to emission level reduction, combustion process optimization by modifications of pyrolysis boilers is aimed at fuel cost decrease. Knowledge of fuel composition and fuel combustion properties is important to the optimum and economical combustion process. The levels of emissions caused by the process can be reduced by several designs and operational modifications. This paper deals with modifications of combustion equipment in order to reduce harmful flue gas emissions in a boiler MA 23. The hot water boiler MA 23 belongs to gasification boilers for dry lump wood combustion; it is intended primarily for the heating of family houses, cottages, small office buildings and other small buildings and has the maximum required heat output of 23 kW. The boiler was tested in several modes, based on the requirements of the standard EN 303-5 dealing with emission limits. A basic requirement was the implementation of technical measures described in the paper and a proposal of method of regulation of flue gas volumetric flow rate and of installation in order to keep emission levels below the required limit.

Artificial Neural Network Modelling of Glass Laminate Sample Shape Influence on the ESPI Modes

The present work is devoted to the applications of artificial neural networks (ANN) for material design prediction. We have investigated the dependence of the generated mode frequency as a function of a sample thickness and a sample shape of glass laminate samples by electronic speckle interferometry (ESPI). The obtained experimental results for differently shaped (thickness, canting and rounding) glass laminate samples are compared with those of ANN. The coincidence of both experimental and simulated results is very good.

The Influence of Rubber Blend Aging and Sample Homogeneity on Heat Transport Phenomena

This paper is devoted to the study of thermal transport phenomena changes caused by natural aging of rubber blends. Thermal conductivity, diffusivity and heat capacity of rubber blends were measured and compared for the same samples before and after half of a year. Samples were stored at room temperature and daily light. In the frame of our investigations there has been observed the decrease of the thermal diffusivity as well as the thermal conductivity in the interval approximately 40-50 %. The changes of specific heat capacity after sample aging were negligible. The explanation of such behaviour we can see in the sample structure degradation caused by the environmental influence.