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Photonic Devices with Siloxane Membranes

Author(s): Matej Goraus,Lubos Suslik,Dusan Pudis,Jana Ďurišová,Daniel Jandura,Jaroslav Kovac,Marek Tlaczala,Wojciech Dawidowski,Beata Sciana / Language(s): English Issue: 3/2017

Expansion of polymer nanotechnologies accelerated the polymer photonics. This technology brings novel interesting results with simple and cheap solutions. Promising candidates are siloxane materials as polydimethyl siloxane (PDMS) and polydimethyldiphenyl siloxane (PDMDPS) with unique mechanical and optical properties. In this paper we present laser lithography technologies in a combination with siloxane embossing for fabrication of different grating structures with periodical and quasiperiodical symmetry. We present the concept of siloxane based thin membranes with patterned surface as an effective diffraction element for modification of radiation pattern diagram of light emitting diodes (LEDs) and enhancement of angular detection properties of photodiodes. Also the combination of PDMDPS and PDMS was used for fabrication of a waveguide structure with surface relief Bragg grating. Optical properties of fabricated LEDs are investigated by near- and far-field measurements. Transmission properties of fabricated waveguide are investigated by optical spectrum analyzer.

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Analysis of Photoluminiscence in the NCSI-DMA System

Author(s): Stanislav Jurecka,Kentaro Imamura,Taketoshi Matsumoto,Hikaru Kobayashi / Language(s): English Issue: 3/2017

Silicon nanocrystalline particles (ncSi) were fabricated from the Si swarf using the beads milling method. Observed photoluminiscence spectra (PL) of the ncSi in hexane with the dimethylanthracene molecules (DMA) show photoluminescence peaks at energies of 2.55, 2.75, 2.92, and 3.09 eV. The shape of PL spectra corresponds to the vibronic structure of adsorbed DMA molecules. The PL intensity of the ncSi-DMA system increases by ~3000 times by adsorption of DMA on Si nanoparticles. The PL enhancement results from an increase in absorption probability of incident light by DMA caused by adsorption on the surface of ncSi. Theoretical model of the PL experiment was constructed and resulting model parameters were used in analysis of possible PL transitions and charge transfer processes.

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Acoustic Investigation of the Structure of Magneto-Rheological Fluid

Author(s): Jozef Kudelcik,Peter Bury,Stefan Hardon,Michal Sedlacik,Tomas Plachy / Language(s): English Issue: 3/2017

The acoustic spectroscopy is used to study properties and changes in structural arrangement in silicone oil based magneto-rheological fluids with carbonyl iron particles upon the effect of an external magnetic field. Attenuation spectra at three temperatures for various concentrations of magnetic particles are presented. The attenuation of acoustic waves was measured for a jump change of the magnetic field to 200 mT as a function of the temperature. The relaxation effects for the acoustic attenuation after switching off the magnetic field and its decrease to the similar value as for clean silicone oil were observed. The change of acoustic attenuation in magneto-rheological fluid versus angle between the wave vector of acoustic waves and direction of the applied magnetic field was measured, too. For the anisotropy measurement are characteristic two local maxima from which results chain orientation in direction of the magnetic field.

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Generation of Random Deviates for Relativistic Quantum-Statistical Distributions

Author(s): Boris Tomasik,Ivan Melo,Jakub Cimerman / Language(s): English Issue: 3/2017

We provide an algorithm for generation of momenta (or energies) of relativistic particles according to the relativistic Bose-Einstein or Fermi-Dirac distributions. The algorithm uses rejection method with effectively selected comparison function so that the acceptance rate of the generated values is always better than 0.9. It might find its use in Monte-Carlo generators of particles from reactions in high-energy physics.

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The Current LHC Limits for the TBESS Lagrangian

Author(s): Mikulas Gintner,Josef Juran / Language(s): English Issue: 3/2017

We investigate how the recent LHC measurements limit the parameters of the hypothetical vector resonance triplet. The vector resonances are assumed to represent bound states of hypothetical strongly-interacting new physics, a candidate of the extension of the Standard model.

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Electrochemical Characteristics of Austenitic Stainless Steel in Mixed Chloride - Molybdate Solutions

Author(s): Viera Zatkalikova,Lenka Markovicova,Anna Wrobel-Knysak / Language(s): English Issue: 2A/2017

The effect of molybdate addition to chloride solutions on resistance of AISI 316Ti stainless steel to pitting corrosion was studied. Potentiodynamic polarization tests were performed in 1 M and 0.1 M chloride acidified solutions with various additions of sodium molybdate at room temperature. The presented results compare the effect of molybdate anions on quality of passive film (expressed by the pitting potential) in both chloride solutions. The pitting potential increases with the increase of inhibitor concentration. The inhibitive effect of molybdate ions is stronger in chloride solution of lower aggressiveness (0.1M).

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Finite Element Modeling Piezoelectric Materials under Thermal Loads with Application for Quantum Dots

Author(s): Milan Zmindak,Pavol Novak,Peter Bishay / Language(s): English Issue: 2A/2017

Significant research has been done in the analysis of properties of quantum dots over the previous decade. A 3D finite element model is developed to analyze quantum dots (QD) under static thermal loads. The lattice mismatch between the quantum dot and the piezoelectric matrix is created by different thermal properties of materials at enhanced temperature of this electronic structure. The fully coupled thermo-piezoelectricity is applied to the analysis of the problem. Commercial FEM software ANSYS was used for analysis. Finite element numerical results are given for the dot with a cubic shape. Numerical results for the InAs/GaAs QD nanostructure show that the elastic and electric fields are strongly influenced by the differences between the material properties of the piezoelectric QD and matrix.

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Application of Memetic Algorithms in Multi-Criteria Structural Optimization

Author(s): Peter Pechac,Milan Saga,Peter Weiss,Tomasz Domański,Marcin Kubiak / Language(s): English Issue: 2A/2017

The goal of this paper is to present new innovative algorithms for discrete structural optimization of problems involving multi-criteria objective function, which contains stress, displacement and frequency constraints. The algorithm is tested on a shell finite element structure, whose optimization variables are geometrical parameters and shell thicknesses. Performance of memetic algorithm will be compared with genetic algorithm.

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Investigation of Stress Status in the Micro-Space of Surface and Subsurface Layer

Author(s): Andrej Czan,Michal Sajgalik,Lucia Zauskova,Robert Cep,Zdenka Rysava,Vitor Luiz Sordi / Language(s): English Issue: 2A/2017

One of main issues when evaluating or analysing quality and functional properties of work-piece is identification of status of residual stress. Every treatment or machining process generates residual stress in the surface and subsurface layers of the material structure. The residual stress has a large influence on the functional properties of the components. The article is focused on the method of triaxial measurement of residual stress after machining the surface of sample by high feed milling technology. Significance of triaxial measuring is the capability of measuring in different angles so it is possible to acquire stress tensor containing normal and shear stress components acting in the spot of measuring, using a Cartesian coordinate system.

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Molybdenum Sheet Metal Test Device

Author(s): Ronald Bastovansky,Michal Tropp,Michal Lukac,František Brumerčík / Language(s): English Issue: 2A/2017

The paper presents the construction of a device that allows processing the Baosteel/Sanchez experiment. The experiment simulates the brake ribs by deep drawing of the molybdenum sheet metal.

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Local Method of Approximate Particular Solutions for Two-Dimensional Unsteady Incompressible Flow

Author(s): Juraj Muzik,Ladislav Kais,Roman Bulko / Language(s): English Issue: 4/2016

A meshless local method of approximated particular solutions (LMAPS) is used to analyze incompressible fluid flow in a two dimensionalcavity. The method solves the incompressible Navier-Stokes equations in terms of theprimitive variables using the fractional step scheme. The basic equations are derived via interpolation using integrated multiquadrics radial basis functions. Lid-driven cavity benchmark case for various Reynolds numbers is presented in the article. The procedure produces stable solutions with results comparable to those in literature.

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Mathematical Modelling of Fibre Winding Process for Composite Frames

Author(s): Michal Petru,Jaroslav Mlynek,Tomas Martinec,Jozef Bronček / Language(s): English Issue: 4/2016

This article describes the authors´ own mathematical modelling designed for the production process of a new type of low-weight composite frame. The used real technology is based on the winding of carbon or glass filament rovings around a polyurethane core which is a frame with a circular cross section (this type of composites is used, for example, to reinforce the doors and windows of airplanes). The core is attached to the end-effector of the robot (robot-end-effector) and successively passes through the fibre-processing head during the winding process. Quality production depends primarily on the correct winding of fibres around the polyurethane core. It is especially needed to ensure the correct angles of the fibre winding around the polyurethane core and the homogeneity of individual winding layers. The numerical model described in Euclidean space E3 of the manufacturing process is used when the fibre-processing frame is passing through the fibre-processing head. We use the described mathematical model and matrix calculus to enumerate the trajectory of the robot-end-effector to determine the desired passage of the core through the fibre-processing head. The calculated sequence of "tool-centre-point" values of the robot allows us to define the desired trajectory of the robot-end-effector and, thereby, the passage of the frame through the fibre-processing head. The calculation of the trajectory was programmed in the Delphi development environment. A practical example is analysed in the article.

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Cutting Metal Sheet with a Punch with Internal Heating

Author(s): Jan Moravec / Language(s): English Issue: 3/2016

This paper describes issues related to the process of cutting with a punch with internal heating. The theoretical part explains the effects related to thermal expansion, conduction and transfer of heat in the body of punches. The experimental part refers to the design of a tool with an internally heated punch. Experimental results are summarised and the process is analysed in the discussion.

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Implementation of Memetic Algorithms into Structural Optimization

Author(s): Peter Pechac,Milan Saga,Ardeshir Guran,Leszek Radziszewski / Language(s): English Issue: 1A/2016

The paper presents an implementation of the memetic algorithm for discrete structural optimization. This algorithm is a combination of genetic algorithm and five local search methods. The proposed memetic algorithm is able to choose the right local search method based on performance which is evaluated in real time during optimization.

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Fractographic Analysis of Hardox Steels Research in the Field of High-Cycle Fatigue Regime

Author(s): Pawel Szataniak,Magdalena Mazur,Robert Ulewicz,Frantisek Novy / Language(s): English Issue: 1/2016

The article presents preliminary fatigue tests results of two high-strength steels used in structural elements of trailers, wagons, farm devices, etc. Paper presents an analysis of fatigue test results of high-strength steels in the range from 104 to 107 numbers of cycles of applied load with a frequency of 40 Hz. Wöhler curve shows the results of the fatigue properties of steels Hardox 400 and Hardox 450, which are used in the construction of vehicles. Fatigue fractures were subjected to fractographic analysis in order to determine the mechanism of fatigue crack propagation.

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Comparison of Experimental Results with Numerical Solution of Thermal Stress Analysis

Author(s): Zuzana Stankovicova,Vladimir Dekys,Leszek Radziszewski,Milan Uhricik,Milan Sapieta / Language(s): English Issue: 4/2015

This paper presents experimental measurement of the first stress invariant on the plate with hole at fatigue testing machine due to adiabatic elastic deformation. The theoretical part is concentrated on the theory of thermal stress analysis focusing on thermoelastic analysis. The experimental part is dedicated to the postprocessing of the measured data including analytical and numerical solutions for the plate with hole using finite element method (FEM).

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Extending of the Life of Active Parts of Cold-Moulding Tools

Author(s): Jan Moravec / Language(s): English Issue: 4/2015

Heat treatment of active components of cold-moulding tools is a necessary operation to guarantee their functionality. The tools made by this method lost required quality of durability and period of service and losses caused by their frequent exchange are high. One way we can stop it is by coating the active parts of pressing tools by thin, hard and abrasion resistant deposit that is suitable by definite method of the tool stress.

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FEM/BEM Techniques for Modelling of Local Fields in Contact Mechanics

Author(s): Milan Zmindak,Leszek Radziszewski,Zoran Pelagic,Milos Falat / Language(s): English Issue: 3/2015

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 elements (sub-domains) using superposition of a local Hertz type field and a smooth field modelled in a classical way using large FEM or BEM technique. A technique of obtaining the complex solution of the bodies in contact as a combination of the local contact field defined by the Boussinesq's solution and the smooth field modelled by multi-domain BEM is described and considered to be a basis for the modelling and design of contact problems containing large gradient displacements.

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Barkhausen Noise Emission in Milled Surfaces

Author(s): Miroslav Neslusan,Tomas Hrabovsky,Maria Cillikova,Anna Micietova / Language(s): English Issue: 3/2015

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.

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Influence of Vanadium and Chromium Addition on Morphology and Composition of Iron Based Phases in AlSi10MgMn Alloy

Author(s): Maria Zihalova,Dana Bolibruchova,Dalibor Vojtech / Language(s): English Issue: 3/2015

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 morphology and chemical composition is analysed by optical microscopy, SEM observations and EDX analysis.

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