No (7621)
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7621
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A short study on self-balancing of vertical rotors mounted in passive contactless bearings
Zapoměl, Jaroslav; Kozánek, Jan
2023 - English
Energy losses and wear of the support elements of high-speed rotors can be reduced by mounting the rotors in stable passive contactless bearings, the operation of which is based on magnetic levitation. The goal of the conducted research was to investigate applicability of selfbalancing device added to vertical rotors supported by bearings showing low stiffness and damping, which is a specific property of passive magnetic bearings. This paper deals with applicability and efficiency of self-balancing devices added to vertical rotors supported by bearings having very low stiffness and damping, which corresponds to the properties of magnetic frictionless bearings.
Keywords:
self-balancing of rotors; passive contactless bearings; the influence of external damping
Available at various institutes of the ASCR
A short study on self-balancing of vertical rotors mounted in passive contactless bearings
Energy losses and wear of the support elements of high-speed rotors can be reduced by mounting the rotors in stable passive contactless bearings, the operation of which is based on magnetic ...
Dynamic tensile experiments of hard rubber on instron test machine under finite deformations
Šulc, Petr; Pešek, Luděk; Bula, Vítězslav; Šnábl, Pavel
2023 - English
This paper deals with the first experimental tests of hard rubbers under tensile harmonic loading on the axial-torsional servohydraulic Instron 8852 test machine. The objective of these experiments on cylindrical rubber specimens on this machine is to obtain stress-strain curves of rubber specimens, first considering uniaxial finite longitudinal strains for a single load cycle. Next, the hysteresis loops and their skeleton curves are compared for two selected strain measures as a function of their conjugate stress. It is shown how to obtain the dependence between elongation in the axial direction and constriction in the radial direction, which is used to determine the Cauchy stress in this configuration.
Keywords:
uniaxial harmonic loading; finite deformation; second Piola-Kirchhoff stress; hysteresis loop; Green-Lagrange strain tensor
Available at various institutes of the ASCR
Dynamic tensile experiments of hard rubber on instron test machine under finite deformations
This paper deals with the first experimental tests of hard rubbers under tensile harmonic loading on the axial-torsional servohydraulic Instron 8852 test machine. The objective of these experiments on ...
Identification of quasiperiodic processes in the vicinity of the resonance
Fischer, Cyril; Náprstek, Jiří
2023 - English
In nonlinear dynamical systems, strong quasiperiodic beating effects appear due to combination of self-excited and forced vibration. The presence of symmetric or asymmetric beatings indicates an exchange of energy between individual degrees of freedom of the model or by multiple close dominant frequencies. This effect is illustrated by the case of the van der Pol equation in the vicinity of resonance. The approximate analysis of these nonlinear effects uses the harmonic balance method and the multiple scale method.
Keywords:
dynamical systems; quasiperiodic response; van der Pol equation
Available at various institutes of the ASCR
Identification of quasiperiodic processes in the vicinity of the resonance
In nonlinear dynamical systems, strong quasiperiodic beating effects appear due to combination of self-excited and forced vibration. The presence of symmetric or asymmetric beatings indicates an ...
Laboratory X-ray imaging in material sciences
Koudelka_ml., Petr; Kytýř, Daniel; Jiroušek, O.
2023 - English
In recent decades, X-ray imaging and computed (micro)tomography (XCT) in particular have become common tools for volumetric inspection, visualization, and analysis of internal structure in materials from various fields [1]. In this lecture, we will explore various applications of laboratory X-ray imaging chains utilizing the combination of tomographical imaging with mechanical, thermal, or chemical loading of the irradiated sample in a so-called time-resolved imaging allowing for unprecedented insight into different phenomena driving fundamental processes encountered in various fields of material science. We will show that failure processes in engineering or geological materials [2] can be thoroughly studied by synergy of information from radiographical imaging and other methods including acoustic emission detection and optical measurements via high-speed visible-spectrum and thermal-imaging cameras, where the radiography provides important spatial information regarding deformation processes evolving within the tested samples that could not be obtained otherwise. The state-of-the-art the laboratory based imaging chains for investigation of dynamic response of materials under loading will be also discussed including high speed X-ray radiography utilizing a powerful X-ray source during high velocity impact as an approach suitable for inspection of an impacted sample. As an alternative to both conventional high-power sources and accelerator facilities, capabilities of a flash X-ray system developed primarily for in-situ ballistics research providing very short bursts of an extremely powerful intermittent X-ray radiation with a typical duration of dozens of nanoseconds will be shown.
Keywords:
X-ray imaging; material characterization; mechanical properties
Available at various institutes of the ASCR
Laboratory X-ray imaging in material sciences
In recent decades, X-ray imaging and computed (micro)tomography (XCT) in particular have become common tools for volumetric inspection, visualization, and analysis of internal structure in materials ...
Aerodynamic Measurements on Subsonic Compressor Blade Cascades KR-D-7 and KR-D-8
Šimurda, David; Hála, Jindřich; Luxa, Martin; Radnic, Tomáš
2023 - English
This report contains results and evaluation of aerodynamic measurements conducted on two variant subsonic compressor blade cascades with MCA profile (KR-D-7) and DCA profile (KR-D-8) at transonic flow regimes.
Keywords:
compressor blade cascade; experiment; transonic flow; subsonic flow; MCA profile; DCA profile
Available at various institutes of the ASCR
Aerodynamic Measurements on Subsonic Compressor Blade Cascades KR-D-7 and KR-D-8
This report contains results and evaluation of aerodynamic measurements conducted on two variant subsonic compressor blade cascades with MCA profile (KR-D-7) and DCA profile (KR-D-8) at transonic flow ...
Aerodynamic Measurements on Transonic Compressor Blade Cascades KR-D-9 and KR-D-10
Šimurda, David; Hála, Jindřich; Luxa, Martin
2023 - English
This report contains results and evaluation of aerodynamic measurements conducted on two variant transonic compressor blade cascades with MCA profile (KR-D-10) and DCA profile (KR-D-9) at transonic flow regimes.
Keywords:
compressor blade cascade; experiment; transonic flow; MCA profile; DCA profile
Available at various institutes of the ASCR
Aerodynamic Measurements on Transonic Compressor Blade Cascades KR-D-9 and KR-D-10
This report contains results and evaluation of aerodynamic measurements conducted on two variant transonic compressor blade cascades with MCA profile (KR-D-10) and DCA profile (KR-D-9) at transonic ...
Jánovce. Paleomagnetic research. Report
Elbra, Tiiu; Kdýr, Šimon; Uçar, Hakan; Pruner, Petr; Schnabl, Petr
2023 - English
Keywords:
Jánovce archeological site; Paleomagnetism; Rock magnetism
Available at various institutes of the ASCR
Jánovce. Paleomagnetic research. Report
Enhanced growth rate of diamond films at low temperature in focused microwave plasma system
Babčenko, Oleg; Bydžovská, Irena; Fait, Jan; Shagieva, Ekaterina; Ondič, Lukáš; Kromka, Alexander
2023 - English
The low temperature (< 500 °C) diamond film deposition on fused silica in two different focused microwave plasma systems, i.e. a multimode clamshell cavity (MCC) and a rotational ellipsoid cavity (REC) reactor, was investigated. During the experiments, the methane to hydrogen ratio, in the hydrogen-rich process gas mixture, varied from 1 % to 15 % for MCC and from 1 % to 9 % for REC. The grown films were analyzed by scanning electron microscopy and Raman shift measurements. The outcomes of the study and enhanced diamond growth at low temperatures is advantageous for overcoating of fused silica as well as thermally sensitive substrates, e.g. optical elements, photonic crystals, sensors, etc.
Keywords:
well-faceted diamonds; low temperature deposition; high growth rate; low non-diamond content; focused plasma
Available at various institutes of the ASCR
Enhanced growth rate of diamond films at low temperature in focused microwave plasma system
The low temperature (...
Self-balancing of vertical disc rotors supported by contactless bearings
Zapoměl, Jaroslav; Kozánek, Jan; Košina, Jan
2023 - English
Article discusses the self-balancing of the vertical disc rotors supported by contactless bearings on principle of diamagnetic levitation. There are three possibilities of contactless supports: permanent magnet levitation with the help of bismuth, graphite and pyrolitic graphite.
Keywords:
self balancing; vertical disc rotors; contactless bearings
Available at various institutes of the ASCR
Self-balancing of vertical disc rotors supported by contactless bearings
Article discusses the self-balancing of the vertical disc rotors supported by contactless bearings on principle of diamagnetic levitation. There are three possibilities of contactless supports: ...
Topical Problems of Fluid Mechanics 2023
Šimurda, David; Bodnár, T.
2023 - English
Proceedings contain collection of papers presented during the conference Topical Problems of Fluid Mechanics 2023. Majority of papers is concerned with numerical simulations covering wide range of applications in fluid mechanics.\n
Keywords:
experimental fluid mechanics; mathematical modelling; CFD; turbulence; stratified fluid; multiphase flow; vortex structures; supersonic flow
Available at various institutes of the ASCR
Topical Problems of Fluid Mechanics 2023
Proceedings contain collection of papers presented during the conference Topical Problems of Fluid Mechanics 2023. Majority of papers is concerned with numerical simulations covering wide range of ...
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