Řada strojní. 2013, roč. 59 / Mechanical Series. 2013, vol. 59

Permanent URI for this collectionhttp://hdl.handle.net/10084/111978

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Now showing 1 - 20 out of 45 results

Online system identification method using modified regularized exponential forgetting
(Vysoká škola báňská - Technická univerzita Ostrava, 2013) Vachálek, Ján; Bartko, Michal
The paper deals with the use of regularized exponential forgetting (REF) in the process of online system identification. The deployment of this type of forgetting strategy is advantageous for very long runs with small changes in the identified input parameters (in the range of 100 000 steps). In these cases, the classical methods of forgetting, such as an exponential (EF) or directional forgetting (DF) lack the required quality and reach the limit of numerical stability of the calculations of system parameters, which may lead to the early termination of system identification procedure. To avoid this undesirable effect and maintain sufficient primary information about the identified system, a modified REF method is used that employs alternative covariance matrix (ACM) formulation to store the primary information of the identified system (REFACM) and prevents the numerical destabilization of the identification process. The quality of the modified REFACM forgetting method —along with its validation and comparison with REZ to verify its properties—is performed using standard tests.
The influence of the basic parameters of the numerical model on the contact pressure in dynamic tasks
(Vysoká škola báňská - Technická univerzita Ostrava, 2013) Semenova, Irina; Horyl, Petr
The paper is devoted to quasi-static and low-velocity impact simulation using finite element modelling. The paper describes the effects of contact models, contact parameters, integration method, and the velocity of impact on contact stresses values. Pure Penalty, Lagrange Multiplier, and Augmented Lagrange Multiplier with various friction factors were used as contact algorithms. The influence of Newmark’s integration method and the central difference time integration method on the resultant stresses is discussed.
Comparison of analysis methods of data from thermographic measurements of Al 2024 fatigue limit for R=0.1
(Vysoká škola báňská - Technická univerzita Ostrava, 2013) Seitl, Stanislav; Klusák, Jan; Fernandez, Pelayo; Fernández-Canteli, Alfonso
The traditional methods for fatigue characterization of metallic materials are expensive and extremely time consuming. In order to overcome these shortcomings, the Thermographic Method (TM), based on thermographic analysis, is applied to estimate the fatigue limit of Al 2024. The temperature increase due to localized microplasticity is considered as the fatigue damage indicator. An experimental program is carried out to assess the fatigue limit both as resulting from the S–N field and, directly, from thermographic measurement. For the latter, three different methods are applied for the estimation of the AL 2024 fatigue limit and the out-coming results discussed. The values of fatigue limit predicted from the thermographic method according to the three methods are in good agreement to that derived from the traditional S-N procedure.
Measuring hysteresis loop and optimization of the stator tooth width in the permanent magnet synchronous machine
(Vysoká škola báňská - Technická univerzita Ostrava, 2013) Novák, Zdeněk; Novák, Martin; Chyský, Jan
The first part of this paper deals with the measuring of hysteresis loop of the toroidal shape core. LabVIEW software is used to automate this process. The results are compared with the data from the manufacturer and used in the FEMM software for setting parameters of the stator core of Permanent magnet synchronous motor (PMSM). Then, in the second part of this paper, the Lua scripting engine in FEMM software is used to optimize stator tooth width. Program code is written in the Matlab environment and after starting the run process, Matlab uses inter-process communication via ActiveX to connect with FEMM. In this process program tries several options for the stator tooth width. Based on the results, user can evaluate all the data about the overall progress and choose the optimal stator tooth width.
About central difference method applied for the beams on elastic foundation
(Vysoká škola báňská - Technická univerzita Ostrava, 2013) Nikodým, Marek; Frydrýšek, Karel
This article is focused on the widely spread theory of straight and curved beams rested on elastic (Winkler's) foundation. For solution of these problems of mechanics, the Finite Difference Method (i.e. Central Difference Method) can be applied. The basic information about finite differences and their application are explained. This article also mentioned a new research in nonlinear behaviour of elastic foundation. Practical examples (i.e. beams with constant or variable stiffness of foundation or nonlinear foundation) are explained and solved (Matlab software).
Recognition of gestures using artifical neural network
(Vysoká škola báňská - Technická univerzita Ostrava, 2013) More, Marcel; Líška, Ondrej
Sensors for motion measurements are now becoming more widespread. Thanks to their parameters and affordability they are already used not only in the professional sector, but also in devices intended for daily use or entertainment. One of their applications is in control of devices by gestures. Systems that can determine type of gesture from measured motion have many uses. Some are for example in medical practice, but they are still more often used in devices such as cell phones, where they serve as a non-standard form of input. Today there are already several approaches for solving this problem, but building sufficiently reliable system is still a challenging task. In our project we are developing solution based on artificial neural network. In difference to other solutions, this one doesn’t require building model for each measuring system and thus it can be used in combination with various sensors just with minimal changes in his structure.
Piecewise-linear neural network - possible training algorithms efficiency comparison
(Vysoká škola báňská - Technická univerzita Ostrava, 2013) Mariška, Martin; Doležel, Petr
In this article, a benchmark of algorithms for training of piecewise-linear artificial neural networks is introduced. At first, motivation of this article is described for a special topology of the neural network is used. This topology can be advantageously used in system control design, but it is difficult problem to train it. In this article, there is described a set of possible training algorithms, these algorithms are tested and evaluated. Benchmarking data are based on real problems.
Simulation model of the weaving machine "CAMEL” and selection of the sufficient driving motor
(Vysoká škola báňská - Technická univerzita Ostrava, 2013) Marek, Ondřej; Bílkovský, Aleš; Jirásko, Petr
The paper deals with the mathematical model of the waving machine CAMEL. This machine consists of many moving parts (rotational and translational movements), belts, flexible elements and therefore it is very complex. CAMEL uses servomotors working in electronic cam regime. It means that the actual angular velocity of the rotor is not constant and therefore it is really important to reduce the moment of inertia of rotating elements. The inertia of the rotor of the drive is very important too. Existing simulation model can help to choose the optimal drive of the machine. It also allows selecting the best displacement laws for different speeds (rpm) in order to decrease the effective torque which is proportional to the heating of the servomotor.
Williams expansion terms and their importance for accurate stress field description in specimens with a crack
(Vysoká škola báňská - Technická univerzita Ostrava, 2013) Malíková, Lucie; Veselý, Václav
The paper deals with an analysis of the stress and displacement fields in various cracked speci-mens (loaded in mode I as well as in mode II). The main goal is to determine an accurate appro-ximation of the near-crack-tip fields which can be subsequently used e.g. in the case of quasi-brittle materials for estimation of the extent of a nonlinear zone at the crack tip in general, the fracture pro-cess zone in particular. Values of coefficients of the so-called higher-order terms of the power expan-sion by which the fields can be expressed are determined via regression from results of numerical si-mulations. The analysis is conducted using 2D numerical models and ANSYS FE computational system is employed. Various aspects regarding the description of the stress/displacement fields by means of the Williams expansion are discussed; especially the convergence of the coefficients of the first several terms of the series expansion, their absolute values and importance for an accurate stress approximation.
Selection of near optimal laser cutting parameters in CO2 laser cutting by the Taguchi method
(Vysoká škola báňská - Technická univerzita Ostrava, 2013) Madić, Miloš; Radovanović, Miroslav; Gostimirović, Marin
Identification of laser cutting conditions that are insensitive to parameter variations and noise is of great importance. This paper demonstrates the application of Taguchi method for optimization of surface roughness in CO2 laser cutting of stainless steel. The laser cutting experiment was planned and conducted according to the Taguchi’s experimental design using the L27 orthogonal array. Four laser cutting parameters such as laser power, cutting speed, assist gas pressure, and focus position were considered in the experiment. Using the analysis of means and analysis of variance, the significant laser cutting parameters were identified, and subsequently the optimal combination of laser cutting parameter levels was determined. The results showed that the cutting speed is the most significant parameter affecting the surface roughness whereas the influence of the assist gas pressure can be neglected. It was observed, however, that interaction effects have predominant influence over the main effects on the surface roughness.
Numerical calculation of overpressure and underpressure of reservoir Z2
(Vysoká škola báňská - Technická univerzita Ostrava, 2013) Klučka, Richard; Pečenka, Luboš; Przeczková, Jana; Frydrýšek, Karel
Reservoir of oil-based liquid stored in iron-concrete foundation is solved using the finite element method. Foundation stiffness is in the calculation included variantly. Load cases are based on operating conditions.
The exercise device of the lower limbs
(Vysoká škola báňská - Technická univerzita Ostrava, 2013) Jureczko, Paweł; Gąsiorek, Damian; Bachorz, Michal; Juszyński, Łukasz
In the article Authors are showing the endurance test of the prototype multifunctional device for contraction exercises of joints and strengthening muscles. The endurance test was conducted with finite element method in the Ansys Workbench program and permitted the durability of material checking, whether the structural figure of the device is safe from the side for patients.
Analysis of parametric optimization of field-oriented control of 3-phase induction motor with using evolutionary algorithm
(Vysoká škola báňská - Technická univerzita Ostrava, 2013) Hudy, Wiktor
In this paper, the impact of regulators set and their types for the characteristic of rotational speed of induction motor was researched.. The evolutionary algorithm was used as optimization tool. Results were verified with using MATLAB/Simulink.
Finite element model of the strain gauge For determining uniaxial tension
(Vysoká škola báňská - Technická univerzita Ostrava, 2013) Goga, Vladimír
Strain gauge is device used to measure the mechanical strains of solid bodies. Deformation of the strain gauge element causes changes its electrical resistance. This resistance change, usually measured using a Wheatstone bridge, is related to the strain by the quantity known as the gauge factor. When the stains are known, it is possible to determined state of stress at a point of measured body using generalized Hooke`s law and Mohr`s circle. Finite element analysis of strain gauge measurement using ANSYS software is subject of this article.
Simulation of welding of thin-walled pipe
(Vysoká škola báňská - Technická univerzita Ostrava, 2013) Gebauer, Marek; Szweda, Jan
The presented paper deals with the residual stress after a welding operation performed by using the TIG method. It was necessary to determine whether or not tension plays a major role in the distortion of the geometry of a thin-walled pipe, or in other words, whether the drawing dimension of the ovality exceeds the specified tolerance. The result of this simulation will help to determine whether or not designers will have to find another technological solution to complete parts. The assembly consists of three parts: the weld bead, thin-walled pipe, and hoop, which are connected by welds as a final product.
Application of selected multi-axial fatigue criteria are using fifth-dimensional space on the results of fatigue experiments
(Vysoká škola báňská - Technická univerzita Ostrava, 2013) Fojtík, František
The paper describes the experimental results obtained for the combined loading of the specimens in the region of high-cycle fatigue. The specimens were manufactured from common structural steel 11523.1. There has been realized a set of proportional and non-proportional experiments in the area of high-cycle fatigue for basic methods of loading, namely: tension/compression, bending and torsion and its mutual combinations. By selected experiments, the specimens were additionally loaded by constant inner/outer pressure and axial prestress for a various loading levels. Experiments were realized on testing machines, situated at author´s workplace. The experimental results were undergone to application of selected and known criteria of fatigue strength and subsequently carried out its modification according to the results. For gaining necessary input values for criteria of fatigue strength, there was a need to realize a FEM simulation of test specimens.
Modelling of cavitation of wash-out water, ammonia water, ammonia water with increased content ammonia and hydrogen sulphide, tar condensate
(Vysoká škola báňská - Technická univerzita Ostrava, 2013) Dobeš, Josef; Kozubková, Milada
The aim is to design and implement a procedure of numerical modelling of cavitation of working mixtures: wash-out water, ammonia water, ammonia water with an increased content of hydrogen sulphide and ammonia, tar condensate. The numeric modelling is designed in the program Ansys Fluent using Schnerr-Sauer cavitation model. The issue of these liquids modelling can be solved by the cavitation simulation of water admixtures. Working fluids contain the following main ingredients: water, ammonia, carbon dioxide and hydrogen sulphide. Subsequently, a comparison of the amount of water vapor (reference liquid) and given fluid vapor is executed. The Schnerr-Sauer model is chosen because of good results in previous simulations for water cavitation. As a geometry is selected Laval nozzle. Modelled liquid mixtures are used in the petrochemical industry, as a filling for fluid circuits where cavitation may occur and therefore the research is needed.
Project of economically profitable technological process of production of rotor and stator plates of inductive position sensor by blanking and roll bending
(Vysoká škola báňská - Technická univerzita Ostrava, 2013) Čada, Radek; Zlámalík, Jan
Paper concerns innovation of production of rotor and stator plates of inductive position sensors which are used at automatization of production processes. Authors analyse possibility of efficiency improvement of production of these devices in joint-stock company TES VSETÍN and suggest concrete solving of new production technology. Composition of production line for blanking and roll bending of rotor and stator plates of inductive position sensor from individual technological devices was suggested: decoiler, straightening device, actuating belt feeder, pneumatic shears with inclined tools, belt conveyer and four cylinders bending rolls. Construction of production line was projected in order to its operation can be secured by one production workman, which controls and chooses operation of CNC programme, takes separate roll bended rotor and stator plates of inductive position sensor from bending rolls and according to required technological procedure he composes them to rotor and stator complexes. Construction of production line was projected so that it is possible to move it by crane without necessity to dismantle and subsequently to put together and adjust the line.
Comparative finite element method analysis of spiroid worm gear drives having arched profile and having linear profile in axial section
(Vysoká škola báňská - Technická univerzita Ostrava, 2013) Bodzás, Sándor; Dudás, Illés
With the knowledge of the advantageous characteristics of the cylindrical worm gear drives having arched profile in axial section and the conical worm gear drives having linear profile in axial section, a new geometric type conical worm gear drive has been designed and then manufactured, that is the conical worm gear drive having arched profile in axial section. Beside similar charging and marginal conditions in case of the same geometric spiroid worm gear drives having arched profile and having linear profile in axial section we have done comparative finite element method analysis for awarding of the strains, deformations and stresses of this gear drives.
Finite element analysis of membrane of automotive key
(Vysoká škola báňská - Technická univerzita Ostrava, 2013) Bartecký, Matěj
The subject of this paper is solving process of pressing button of automotive key in environment of software ANSYS. Physical model include hyper elastic material, nonlinear spring and prescribed boundary condition of structural analysis. The main aims of this work were to get actuating forces of automotive key as well as to get stress and strain level of rubber membrane.

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