Ján Kmec

Microhardness of the Coatings Created by Anodic Oxidation of Aluminum

Microhardness is a basic controlled quality parameter according to functional coatings, which is linked with a number of physico-chemical properties, such as coating strength, abrasion resistance, resistance to deformation, life. Life of the coating from a diagnostic point of view is influenced by chemical, physical, technological and material conditions of the process of creating film. The paper deals with analysis of the microhardness coating created by anodic oxidation of aluminum with a direct link to the chemical and physical factors controlled by the Design of Experiments methodology at constant anode current density 2 A.dm-2.

Statistical Analysis of the Factors Effect on the Zinc Coating Thickness

In order to improve the corrosion resistance of the material EN 355 the thickness of the zinc coating, deposited during the acid zinc plating process at a constant current density 1 A·dm-2, was monitored. The thickness of deposited coating has been investigated as the relationship of physical and chemical factors acting during the galvanic zinc plating, i.e. the electrolyte temperature, electrolyte composition (the amount of zinc, the amount of chloride and boric acid in the electrolyte), the plating time and the size of the voltage. Based on the mathematical-statistical analysis of the obtained data the suitable predicting model was developed for determining the thickness of deposited zinc coating reflecting the technological conditions of the acid zinc plating process.

The Influence of Sodium Chloride on the Resulting AAO Film Thickness

The contribution examines the effects of the electrolyte chemical composition on the resulting AAO layer thickness, which is one of the main indicators of corrosion protection of aluminium parts and which also favourably affects mechanical properties of component surfaces. For comparison purposes, there were selected the electrolytes comprising sulphuric acid, oxalic acid, boric acid and sodium chloride. Anodizing time for all specimens was 210.00 minutes. At the same time, equal electrolyte temperature 22.00°C ± 13.64% as well as equal magnitude of the applied voltage 12.00 V ± 4.17% were determined for all specimens. The results obtained lead to the assumption that it is possible to replace conventional electrolytes by those that are more environmentally friendly, reduce the costs of their disposal and allow obtaining oxide layers of the same thickness. The admixture of sodium chloride plays here the crucial role and its effect on the thickness of the formed oxide layer has not been published yet in any study.

Usage of Neural Network to Predict Aluminium Oxide Layer Thickness

This paper shows an influence of chemical composition of used electrolyte, such as amount of sulphuric acid in electrolyte, amount of aluminium cations in electrolyte and amount of oxalic acid in electrolyte, and operating parameters of process of anodic oxidation of aluminium such as the temperature of electrolyte, anodizing time, and voltage applied during anodizing process. The paper shows the influence of those parameters on the resulting thickness of aluminium oxide layer. The impact of these variables is shown by using central composite design of experiment for six factors (amount of sulphuric acid, amount of oxalic acid, amount of aluminium cations, electrolyte temperature, anodizing time, and applied voltage) and by usage of the cubic neural unit with Levenberg-Marquardt algorithm during the results evaluation. The paper also deals with current densities of 1 A·dm−2 and 3 A·dm−2 for creating aluminium oxide layer.

Experimental Study and Modeling of the Zinc Coating Thickness

The effects of six factors, affecting during the acid zinc plating process as its technological conditions, on the thickness of the resulting zinc coating has been examined. In order to control the quality of the resulting zinc coating deposited on the surface alloy EN 355 at a constant current density of 5 [Adm-2], the mathematical model predicting the thickness of deposited coating was developed using Design of Experiments (DoE) method. The obtained mathematical model describes the resulting deposited layer of zinc coating in dependence on the factor-level changes and combinations with the reliability of 58.75%.

Effect of the Electrolyte Temperature and the Current Density on a Layer Microhardness Generated by the Anodic Aluminium Oxidation

The paper investigates the influence of the chemical composition and temperature of electrolyte, the oxidation time, voltage, and the current density on Vickers microhardness of aluminium oxide layers, at the same time. The layers were generated in the electrolytes with different concentrations of sulphuric and oxalic acids and surface current densities 1 A·dm−2, 3 A·dm−2, and 5 A·dm−2. The electrolyte temperature varied from −1.78°C to 45.78°C. The results have showed that while increasing the electrolyte temperature at the current density of 1 A·dm−2, the increase in the layer microhardness values is approximately by 66%. While simultaneously increasing the molar concentration of H2SO4 in the electrolyte, the growth rate of the microhardness value decreases. At the current density of 3 A·dm−2, by increasing the electrolyte temperature, a reduction in the microhardness of the generated layer occurs with the anodic oxidation time less than 25 min. The electrolyte temperature is not significant with the changing values of the layer microhardness at voltages less than 10.5 V.

Mathematical Modelling and Optimization of Technological Process Using Design of Experiments Methodology

The paper deals with statistical methods application to the evaluation of the relationships between the investigation range of input factors and response in longitudinal turning process. Our research was aimed at creation of the model of real situations of cutting conditions effects on the machined surface morphology applying longitudinal turning of steel C45 with specific values. Design of experiments (DoE) have increasingly had a wider application when creation mathematical and statistical models of technological processes. So the main part of the paper is to demonstrate the procedure of statistical processing of experimentally obtained data in order to create a prediction model and compare it with the theoretical calculation formulas.

Analysis of SCN5A Gene Variants in East Slovak Patients with Cardiomyopathy

Mutations in ion channels genes are potential cause of cardiomyopathy. The SCN5A gene (sodium channel, voltage gated, type V alpha subunit gene; 3p21) belongs to the family of cardiac sodium channel genes. Mutations in SCN5A gene lead to decreased Na+ current and ion unbalance. The SCN5A gene mutations are found in approximately 2% of patients with dilated cardiomyopathy (DCM), and they may be potential phenotype modifiers in hypertrophic cardiomyopathy (HCM). The role of SCN5A gene mutations in cardiomyopathy is not fully elucidated.

Monitoring of influence of significant parameters during anodizing of aluminium

The paper deals with the possibilities of control the technological process of aluminium anodic oxidation using the Design of Experiments (DoE) and the higher order neural unit to monitor the influence of the significant parameters on the resulting AAO (anodic aluminium oxide) film thickness. It also compares the relationship between individual inputs factors and their mutual interactions on the AAO thickness at monitored current density of 1.00 A·dm-2 and 6.00 A·dm-2. The developed predicted model describes the influence of input factors on the final AAO thickness by cubic function and its reliability is 99.37 % at current density of 1 A·dm-2 and 99.47% at current density of 6 A·dm-2. The electrolyte temperature and the size of an applied voltage had the most important influence.

Influence of Processing Parameters Production of Sandwich Composite Structures Designed Especially for the Construction of Machine Tool Parts

All components of a huge machine tool need to work together perfectly to ensure not only a quality finished product, but operator safety. One of those many components is the material of support panels and moving parts in the machine construction. Mechanical structure of the machine, in most cases does not reach the technical level of regulatory techniques or electric drives and potential increase in dynamics, speed or accuracy of the machines remain unused. Used classic construction materials, steel or light alloy then zoom in to limit their physical capabilities. Designers have machine tools or robots are forced to solve the formidable task in the form of reducing the weight of the moving parts while maintaining or even increasing stiffness with respect to the thermal stability or damping. Laminates are for construction of production machines, robots and manipulators of crucial importance. One big advantage is the high rigidity while maintaining low specific weight. The presented paper is focused on the investigation of composite sandwich construction produced by prepreg technology, which is the suitable production choose for construction of machine tools parts. First of all, the production of sandwich structures with cork core, honeycomb core and foam cores are compared and described. In terms of the production process it is a method very friendly to the environment, since there are no leaks styrene vapours into the air. Since it is important from the perspective of a manufacturer of transport or machine industry manufactured from environmentally friendly materials, so naturally from materials that are from the perspective of safety of passengers (operators of machine tools or robots) at a high level, when any accident was lowest possible hazard due to fire (burn materials used) and terms of the strength of composite materials. This is one of the major scientific articles and to find the most ideal surveyed composite sandwich materials that would be the greatest possible extent fulfils the required properties. In the experimental part of the article are compared and investigated the mechanical characteristics of composite sandwich structures with regard to varying number of layers of predimpregnated skin materials due to the different types of core materials suitable for use in the machine industry. In addition, these characteristics are an important part of the article research because described the influence number of layers to values of the bending stiffness those composite structures.