Communications - Scientific Letters of the University of Zilina, 2015 (vol. 17), issue 3
Articles
Correlations for Heat Transport by Natural Convection of Cylindrical Surfaces Situated One above the Other
Milan Malcho, Jozef Jandacka, Tadeas Ochodek, Jan Kolonicny
Communications - Scientific Letters of the University of Zilina 2015, 17(3):4-11 | DOI: 10.26552/com.C.2015.3.4-11 
The paper presents a new criterion equation for calculating the Nusselt number for heat transport by natural convection from different numbers of cylindrical surfaces of heating sources. Horizontal cylindrical surfaces are situated one above the other and each of them is independently electrically heated by constant power output of Joule heating. Correlation relationships were derived on the basis of tens of measurements of heat outputs of the system of electrically heated horizontal cylindrical surfaces in a thermostatic chamber under defined conditions. The number of cylindrical surfaces, their distance and heat output to the horizontal cylinder...
Numerical Modeling of Ferrite Material Impact on the Effectiveness of Induction Heating Process
Andrej Gasparec, Milan Saga, Peter Pechac
Communications - Scientific Letters of the University of Zilina 2015, 17(3):12-17 | DOI: 10.26552/com.C.2015.3.12-17
The article deals with numerical simulation of induction heating process as a coupling of electromagnetism and heat transfer. The article presents how the surrounding materials used in the induction heating process influence the resulting temperature. The scope of the article is to show impact of ferrite material on the resulting temperature of induction heating process.
Factors Affecting Emission Concentrations in Small Heat Sources
Michal Holubcik, Radovan Nosek, Katarína Sulovcova, Roman Weber
Communications - Scientific Letters of the University of Zilina 2015, 17(3):18-24 | DOI: 10.26552/com.C.2015.3.18-24
Combustion of biomass fuel itself as a renewable energy source does not automatically ensure the best use of its energy content with low emission production. Biomass combustion with bad settings of combustion conditions can be ineffective and with a high production of emissions. The article discusses the impact of various aspects on the power and emission parameters of the heat source. The influence of the amount of combustion air, the temperature of combustion air, the relative humidity of combustion air, the fuel feeding and fuel moisture on thermal power and emission production in automatic boiler for combustion of wood pellets were specifically...
Influence of Mechanical Anisotropy in Low Carbon Microalloyed Steel
Jozef Broncek, Peter Jankejech, Peter Fabian, Norbert Radek
Communications - Scientific Letters of the University of Zilina 2015, 17(3):25-30 | DOI: 10.26552/com.C.2015.3.25-30
The energy industry is one of the most discussed topics in modern days. Among the critical areas belongs the production and sale of energy, including fuel extraction, manufacturing, refining and distribution. As today's society consumes large amounts of fuel, the energy industry is affecting the infrastructure and maintenance of all civilizations across the globe. Transportation of oil and natural gas through a pipeline system proves to be most efficient and safe. Most pipelines are made from steel. The quality and properties of steel used in this field are determined by the environmental safety requirements and industry regulations. The majority of...
Computational Modelling of the Rail Vehicle Multibody System Including Flexible Bodies
Jan Dizo, Miroslav Blatnicky, Blanka Skocilasova
Communications - Scientific Letters of the University of Zilina 2015, 17(3):31-36 | DOI: 10.26552/com.C.2015.3.31-36
Tools for computer simulations are widely used in the field of a rail vehicle design. These means of virtual reality allow to perform static analyses of rail vehicle parts and dynamic analyses of a rail vehicle multibody system. For static analyses the finite element methods are most commonly used while the multibody system analyses are used for analyses of the rail vehicle dynamics. This paper deals with an implementation of flexible bodies into the rail vehicle multibody system. The implementation of flexible bodies into the rail vehicle multibody system extends the using of simulations, especially for an assessment of an influence of flexible bodies...
FEM/BEM Techniques for Modelling of Local Fields in Contact Mechanics
Milan Zmindak, Leszek Radziszewski, Zoran Pelagic, Milos Falat
Communications - Scientific Letters of the University of Zilina 2015, 17(3):37-46 | DOI: 10.26552/com.C.2015.3.37-46
This contribution contains description of modelling technique of contact problems of bodies with curved surfaces when assumption of infinitesimal displacements can be considered to give sufficient accuracy for both displacement and stress analysis. This assumption considers that the local configuration of the bodies in contact will not be influenced during the deformation process and only dimensions and shape of the contact surfaces and contact pressures will change by the load conditions. Such assumptions enable to reduce the contact problem considerably, if the local contact displacement and stress fields are modelled as local fields inside large...
Epicyclic Gear Train Synthesis
Frantisek Brumercik, Maria Tomasikova, Aleksander Nieoczym
Communications - Scientific Letters of the University of Zilina 2015, 17(3):47-50 | DOI: 10.26552/com.C.2015.3.47-50
The synthesis of an epicyclic gear train is a difficult task that can be solved by different methods with significantly various computational time demands. This article describes effective approach to the two-linked epicyclic gear train synthesis. The method described in this article is based on the fundamental gear ratio calculation for each possible combination of gearbox external elements connected to the internal planetary structure.
Simulation Modeling of Barrel Bore Wear under Dynamic Pressure Load
Milan Zmindak, Zoran Pelagic, Martin Nagel, Lukas Smetanka, Zuzana Stankovicova
Communications - Scientific Letters of the University of Zilina 2015, 17(3):51-56 | DOI: 10.26552/com.C.2015.3.51-56
Wear is one of the major forms of material deterioration, often limiting both the life and the performance of the industrial components and requiring frequent replacement of the components. Wear is a very complex process and occurs by combination of several factors, such as the type of lubrication, loading speed, temperature materials, surface finishing and hardness. To simulate wear as a whole is very difficult, in many cases even not possible. The simulation by using the finite element method (FEM) is becoming increasingly popular and accessible. The FEM can also be used by solving mechanical wear, where it is critical to know the right way and method...
Barkhausen Noise Emission in Milled Surfaces
Miroslav Neslusan, Tomas Hrabovsky, Maria Cillikova, Anna Micietova
Communications - Scientific Letters of the University of Zilina 2015, 17(3):57-61 | DOI: 10.26552/com.C.2015.3.57-61
This paper deals with the non-destructive evaluation of surface made of roll bearing steel 100Cr6 after milling cycles via Barkhausen noise technique. The paper discusses magnetic anisotropy linked with the structure transformations with regard to variable flank wear of cutting tool. Effective value of Barkhausen noise (BN), Peak Position and Full Width at Half Maximum (FWHM) derived from the raw BN signals are compared with metallographic observations and residual stress profiles. Surface integrity is also expressed in term of surface roughness due to comparable BN sensitive layer and the height of surface roughness profile.
Fatigue Resistance of C30 Structural Steel
Libor Trsko, Otakar Bokuvka, Peter Palcek, Frantisek Novy, Katarina Mikova
Communications - Scientific Letters of the University of Zilina 2015, 17(3):62-66 | DOI: 10.26552/com.C.2015.3.62-66
In this paper the authors present and discuss results of both fatigue life tests and fatigue crack growth rate tests performed for C30 steel which is used for railway axle manufacturing. The obtained results demonstrate the differences in fatigue strength and fatigue crack growth resistance in two different parts of one railway axle which are subjected to different levels of plastic deformation, namely the axle bolster body and axle body.
How to Supply Assembly Liines
Pavel Kopecek, Milan Pinte
Communications - Scientific Letters of the University of Zilina 2015, 17(3):67-71 | DOI: 10.26552/com.C.2015.3.67-71
Great efforts are currently dedicated to cost engineering in industry. The lean production approach is a good way to lower production costs. Material flows and treatment should be planned and controlled neither too early nor too late, because early production leads to an increase of stocks of materials and late production to a backlog of orders. This task is especially important in serial production, e.g. in the automotive industry. A buffer stock could be connected with assembly lines in many ways, such as handcarts, fork lift trucks or special cableways. A modern method of material supply in an assembly workshop is the usage of tow trains consisting...
Production Layout Planning Using Genetic Algorithms
Martin Krajcovic, Viktor Hancinsky
Communications - Scientific Letters of the University of Zilina 2015, 17(3):72-77 | DOI: 10.26552/com.C.2015.3.72-77
Globalisation of entrepreneurship has not only opened world markets but also global competition. The fundamental criteria for decisions on allocation of manufacturing capacities are currently not only costs (manufacturing, logistics, etc.), but mainly quality (of products, processes and services), flexibility (types of products, capacity, space, time) and a company´s innovative capability. Therefore the enterprise's facility layout needs to be more flexible to adapt to the rapidly changing environment. The need for flexibility of layout planning puts higher requirements for utilisation of layout and location problem solving methods. Classical methods,...
Acquiring Knowledge Needed for Pull Production System Design through Data Mining Methods
Peter Bubenik, Filip Horak, Viktor Hancinsky
Communications - Scientific Letters of the University of Zilina 2015, 17(3):78-82 | DOI: 10.26552/com.C.2015.3.78-82
Article deals with defining relationships for setting the optimal number of kanban cards in individual circuits of pull production systems, in order to minimize work in progress, while maximizing the number of completed orders in the observed time interval. To achieve this objective, data mining methods were used.
Oscillators Near Hopf Bifurcation
Helena Samajova, Tongxing Li
Communications - Scientific Letters of the University of Zilina 2015, 17(3):83-87 | DOI: 10.26552/com.C.2015.3.83-87
In this paper the differential transformation method (DTM) is employed to solve a system of linear differential equations derived for energy optimal control theory and nonlinear differential equations and their systems for oscillators near Hopf bifurcation. They are given by differential equations in a complex plane. Different types of forced terms are considered. The approximate solutions are given in the form of series with required accuracy. Some numerical examples are provided.
Mechanical Differential Mathematical Model
Frantisek Brumercik, Michal Lukac, Aleksander Nieoczym
Communications - Scientific Letters of the University of Zilina 2015, 17(3):88-91 | DOI: 10.26552/com.C.2015.3.88-91
The simulation of a road vehicle requires also the model of a mechanical differential. This article describes one of the possibilities how to build a mechanical differential model by the selected vehicle model structure.
Influence of Vanadium and Chromium Addition on Morphology and Composition of Iron Based Phases in AlSi10MgMn Alloy
Maria Zihalova, Dana Bolibruchova, Dalibor Vojtech
Communications - Scientific Letters of the University of Zilina 2015, 17(3):92-97 | DOI: 10.26552/com.C.2015.3.92-97
Application of secondary Al-Si alloys is mostly influenced by amount of impurities. Detrimental effect of iron, as the most harmful impurity, refers mainly to morphology of iron intermetallic phases. Morphology of iron phases can be influenced by several methods from which the most common is addition of some elements. In primary alloys manganese is commonly used, but its influence is not such favourable in high iron levels because of so-called sludge phase formation. Higher iron content thus requires other alloying elements which can be vanadium, chromium or others. In this article, vanadium and mutual vanadium and chromium influence on iron phase...
Identification of Lack of Fusion and Penetration in Circumferential Fillet Weld by Phased Array Ultrasonic Method in Gas Industry
Radoslav Konar, Milos Mician, Jozef Mesko, Michal Sventek
Communications - Scientific Letters of the University of Zilina 2015, 17(3):98-102 | DOI: 10.26552/com.C.2015.3.98-102
The article deals with non-destructive ultrasonic identification of lack of fusion and penetration in circumferential fillet welds in gas industry by using Phased Array method. These types of welds are used mainly for repairs of gas pipelines during operation. The main aim of this paper is to compare results of measurements of the weld with and without defect. Phased Array testing procedures for circumferential fillet welds methods are also described in this article.
Research of Physiological Factors Affecting Pilot Performance in Flight Simulation Training Device
Andrej Novak, Maria Mrazova
Communications - Scientific Letters of the University of Zilina 2015, 17(3):103-107 | DOI: 10.26552/com.C.2015.3.103-107
Physiological factors can easily affect a pilot performance and jeopardise the safety of the flight. Therefore, the research is based on the observation of student pilots' decision making and flying abilities during different flight conditions predetermined for the flight in simulation training device. The use of flight simulation training device is helpful as it is possible to vary flight parameters and consequently observe the pilot's reactions to different situations. The combination of pilot error statistics and subjective questionnaire enable to determine the influence of external conditions on the pilot's psychological state and subsequent performance...
On the Optimal Pin Set Generation
Karol Grondzak, Juraj Branicky
Communications - Scientific Letters of the University of Zilina 2015, 17(3):108-112 | DOI: 10.26552/com.C.2015.3.108-112
Security of the information is one of the recent topics, attracting attention of security professionals as well as common people. With deep penetration of electronic devices into our everyday life the challenge to protect our privacy is increasing. Simple mechanism for authentication is shared secret in the form of password. In this paper we describe a method for generating a set of passwords in the form of Personal Identification Number (PIN), which can be used to provide an authentication mechanism for simple electronic devices with limited input possibilities.
The Impact of Selected Factors of Utility Motor Vehicles Operation Conditions on the Economy Driving
Lukas Holesa, Karol Hrudkay
Communications - Scientific Letters of the University of Zilina 2015, 17(3):113-118 | DOI: 10.26552/com.C.2015.3.113-118
Article analyzes the specific conditions of operating commercial vehicles and deals with their influence on the operation economy of a selected vehicle category. The article results are the empirically determined factors of the selected conditions that have the strongest (greatest) influence on variability of the average fuel consumption of selected vehicles. These factors are also supported by appropriate calculations. The next part of the article is creating a regression model through which it is possible to measure the impact of the factor changes on an observed variable.
Dominant Air Pollution Source Determination in the Vicinity of Coking Plant Based on Statistical Data Analysis
Jan Bitta, Irena Pavlikova, Ondrej Zavila, Pavel Platos, Jose Maria Caridad y Ocerin
Communications - Scientific Letters of the University of Zilina 2015, 17(3):119-123 | DOI: 10.26552/com.C.2015.3.119-123
The goal of the article is to present the statistical analysis based determination of the dominant air pollution sources in one of the Ostrava pollution monitoring stations. Statistical analyses were based on correlation analysis and quantile-based time pattern analysis. These analyses were able to prove that benzene and toluene pollution is dominantly caused by the same pollution sources. The time pattern analysis then proved the dominance of a nearby cokery. Time pattern analyses also proved traffic to be the dominant source of NO2 pollution and PM10 pollution to be the mix of traffic, heating and industrial sources.