Communications - Scientific Letters of the University of Zilina, 2009 (vol. 11), issue 2
Articles
Stress Sensitivity Analysis of the Beam and Shell Finite Elements
Milan Saga, Milan Vasko
Communications - Scientific Letters of the University of Zilina 2009, 11(2):5-12 | DOI: 10.26552/com.C.2009.2.5-12 
The stress sensitivity analysis in conjunction with finite elements method represents an important tool for the influence analysis of the structural parameters. This analysis plays a significant role in the decision process of the formulation of the structural optimizing or probability analysis. The goal of the paper is to present theoretic and numerical aspects of the beam and shell element stress sensitivity analysis with the respect to the cross section parameters (cross section area, thickness, etc.). The whole computational procedure was inbuilt into Matlab's software module MATFEM.
Particles Interactions in Composites Reinforced by Fibre and Spherical Inclusions
Milan Zmindak, Pavol Novak
Communications - Scientific Letters of the University of Zilina 2009, 11(2):13-18 | DOI: 10.26552/com.C.2009.2.13-18
In our contribution we will show a new Method of Continuous Source Functions (MCSF) to modelling of such problems like composites reinforced by finite length fibres with a large aspect ratio and composites reinforced by spherical inclusions. The source functions (forces and dipoles) are continuously distributed along the fibre axis (i. e. outside of the domain, which is the domain of the matrix) and their intensities are modelled by 1D quadratic elements along the axis in order to satisfy continuity conditions between the matrix and fibre. The spherical inclusions are modelled by a triple dipole located in the centre of the particle and the intensities...
Solution of Mechanical Systems with Uncertainty Parameters Using IFEA
Milan Vasko, Milan Saga
Communications - Scientific Letters of the University of Zilina 2009, 11(2):19-27 | DOI: 10.26552/com.C.2009.2.19-27
The paper presents a non-traditional computational approach for structural analysis with uncertainties in material, geometry and load parameters. Uncertainties are introduced as bounded possible values - intervals. The main goal is to propose algorithms for interval computations on FEM models suggested by authors. An application of the chosen approaches is presented - the first one, a simple combination of only inf-values or only sup-values; the second one presents full combination of all inf-sup values; the third one uses the optimisation process as a tool for finding out a inf-sup solution and last one is Monte Carlo technique as a comparison tool.
Gaseous Emissions of a Combined Cogeneration Unit
Emil Toporcer, Vladimir Hlavna, A. Kovalcik
Communications - Scientific Letters of the University of Zilina 2009, 11(2):28-32 | DOI: 10.26552/com.C.2009.2.28-32
Problem of harmful gaseous emissions is solved in the paper in two ways. Firstly it is the design of amathematical model of flow and combustion in a combustion chamber of an engine, which is a component of a combined cogeneration unit with a proposal of solutions enabling the decrease in amount of harmful gaseous emissions. Secondly it is the verification of the solutions through the computation by means of mathematical models considering these solutions.
Hydromechanical Automatic Transmission
Lubos Kucera, Michal Lukac, Ladislav Jurak, Frantisek Brumercik
Communications - Scientific Letters of the University of Zilina 2009, 11(2):33-35 | DOI: 10.26552/com.C.2009.2.33-35
This contribution describes some tests of hydromechanical infinitely variable transmission (IVT) on a test stand. Further, there is described a truck with installed IVT and tests of this IVT at real conditions. There is also shown a control system of the IVT.
Stray Currents on Direct - Current Railways in Slovenia
Bojan Cene
Communications - Scientific Letters of the University of Zilina 2009, 11(2):36-40 | DOI: 10.26552/com.C.2009.2.36-40
DC stray currents are currents which do not flow through designed conductors but along the path of least resistance. These currents are very harmful to various metallic structures and lead to corrosion in the long term. The most significant sources of DC stray currents in Slovenia can be found in electrified railways using the direct current system of 3000 V. Not all the return current can flow back to the rectifier substation through the rails but a high percentage of this current is dispersed in the earth, depending on conductive arteries. In some cases, these stray currents even cross a very winding railway line. The Slovenian Railways have electrified...
Railway Wheel and Rail Roughness Analysis
Tomas Lack, Juraj Gerlici
Communications - Scientific Letters of the University of Zilina 2009, 11(2):41-48 | DOI: 10.26552/com.C.2009.2.41-48
The paper deals with the railway wheel unroundness (out-of-round) analysis and with the rail head roughness analysis. Roughness of the running surfaces is the predominant source of noise of rail bound transport systems today. Reliable measurements of the roughness of rails and wheels are crucial for noise reduction purposes. In the past, the main purpose of measurements was the understanding of corrugation growth and rolling noise generation. Meanwhile, quantitative descriptions have gained considerable importance.
Iterative Method for Railway Wheel Profile Design
Juraj Gerlici, Tomas Lack
Communications - Scientific Letters of the University of Zilina 2009, 11(2):49-56 | DOI: 10.26552/com.C.2009.2.49-56
The presented article deals with the methods for the railway wheel profile development on the base of the intended shape of wheelset/track contact geometric characteristics. The article deals with two methods. In short the profiles creation method through arcs radii profile variation is mentioned. The main emphasis is directed to the "Iterative method for a railway wheel profile design". This method is explained in a more detailed way in the article. The base for the creation of new profiles with the help of the first method is an interactive attitude based on the modification of the original shape which is defined by section of a railway wheel profile,...
Construction of a Bearing Testing Apparatus to Assess Lifetime of Large-Scale Bearings
Slavomir Hrcek, Vaclav Kraus, Robert Kohar, Stefan Medvecky, Pavol Lehocky
Communications - Scientific Letters of the University of Zilina 2009, 11(2):57-64 | DOI: 10.26552/com.C.2009.2.57-64
This article discusses steps towards the design, construction and production of a device used for lifetime assessment of large-scale bearings. The machine is reviewed as a mechatronic entity, comprised of three parts - mechanical, electro technical and hydraulic. The mechanical part was designed with the help of modern CAD/CAE/PDM design systems along with device parts modeling and strength analysis of highly stressed device parts. The electrotechnical part consists of a driving unit - containing the frequency transducer and an asynchronous motor; the PLC-driven operating part together with a touchscreen interface and a monitoring part which includes...
Dynamic Analysis of a 4-Axles Railway Vehicle Model
Zuzana Ondrova
Communications - Scientific Letters of the University of Zilina 2009, 11(2):65-69 | DOI: 10.26552/com.C.2009.2.65-69
The paper deals with using dynamic simulations in fields of construction, production and operating of railway vehicles. It contained process of dynamics solution of choices referent vehicle by the help special solution software - MSC ADAMS. The creating of virtually model included creating model for railway vehicle and the model of track which is assigned for motion of railway vehicle. In the end of paper there are summary of obtained data from dynamic analysis which give us integrated view of railway vehicle behavior by the run on given track.
Some Extralingual Variables of L2 Phonic Competence
Zdena Kralova, Eva Skorvagova, Juraj Ruttkay
Communications - Scientific Letters of the University of Zilina 2009, 11(2):70-75 | DOI: 10.26552/com.C.2009.2.70-75
The study assessed the relation between the overall degree of perceived foreign accent in non-natives' English speech and some extralingual factors. These variables include musical ability, phonic mimicry ability and type of personality. Five native speakers of English were asked to auditorily evaluate the samples of free English speech produced by each of 79 non-native talkers using the equal-appearing interval scale. The 5-point scale was used to rate each of the variables for each non-native speaker and the interclass correlation coefficients were calculated to identify the most important predictors of L2 pronunciation quality. The findings reported...