No (3138)
Yes (81)
Number of found documents:
3219
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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: ...
Dynamics of a cantilever beam with piezoelectric sensor: Finite element modeling
Cimrman, Robert; Kolman, Radek; Musil, Ladislav; Kotek, Vojtěch; Kylar, Jaromír
2023 - English
An elastodynamical model of a cantilever beam coupled with a piezoelectric sensor is introduced and its discretization using the finite element method is presented. The mathematical model includes additional terms that enforce the floating potential boundary condition for keeping a constant charge on an electrode of the sensor. The behaviour of the model is illustrated using a numerical example corresponding to an experimental setup, where vibrations of the beam and the potential on the sensor are measured.
Keywords:
finite element method; piezo-electricity; floating potential; dynamic simulation
Fulltext is available at external website.
Dynamics of a cantilever beam with piezoelectric sensor: Finite element modeling
An elastodynamical model of a cantilever beam coupled with a piezoelectric sensor is introduced and its discretization using the finite element method is presented. The mathematical model includes ...
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 ...
Dynamics of a cantilever beam with piezoelectric sensor: Parameter identification
Cimrman, Robert; Kolman, Radek; Musil, Ladislav; Kotek, Vojtěch; Kylar, Jaromír
2023 - English
The piezoelectric materials are electroactive materials often applied for real-time sensing or structural health monitoring, both important research topics in dynamics. Mathematical models of such structures have to allow also for the external electrical circuits and contain several material parameters that need to be identified from experiments. We present a model of a simple experiment involving dynamics of a cantilever beam with an attached piezoelectric sensor excited by a suddenly removed weight. The external circuit can be taken into account as having either a finite or infinite resistance. We also outline the parameter identification procedure based on automatic differentiation and present the experimental and numerical results.
Keywords:
finite element method; piezo-electricity; floating potential; dynamic simulation; parameter identification
Fulltext is available at external website.
Dynamics of a cantilever beam with piezoelectric sensor: Parameter identification
The piezoelectric materials are electroactive materials often applied for real-time sensing or structural health monitoring, both important research topics in dynamics. Mathematical models of such ...
Modální analýza pryží odpruženého kola Stadler se dvěma variantami listových tlumičů
Šnábl, Pavel; Pešek, Luděk; Bula, Vítězslav
2023 - Czech
Cílem těchto modálních analýz bylo identifikovat vlastní frekvence a tlumení pryžo-odpruženého kola a porovnat jak obě varianty tlumičů mezi sebou sebou, tak s dřívějším měřením gumo-odpruženého kola typu Stadler bez tlumičů. Experimentální modální analýza probíhala v laboratoři ÚT s použitím jednobodového buzení (SIMO) na pryžo-odpruženém kole. Z této dynamické analýzy byly získány vlastní frekvence a tvary kmitání kola v pásmu do 6,4 kHz. Následně byly provedeny i detailnější analýzy v úzkém frekvenčním pásmu zaměřené na chování tlumičů se smykovým elementem v důležitých rezonancích pro vznik valivého a kvílivého hluku. The aim of this work was an experimental modal analysis of the Stadler tram wheel for two shock absorber variants: a) standard leaf shocks, b) leaf shear shocks. In the report the measurement methodology is described and the results of the modal analysis are tabulated. The results of the modal behaviour of each damper variant give an assessment of their effectiveness in suppressing significant resonances and the corresponding mode shapes. Standard leaf dampers designed as an open steel-rubber sandwich contributed most to the damping enhancement for the R3 shape, followed by R2. Newly developed leaf shear dampers provided a significant increase in damping for the R2 shape compared to standard dampers.
Keywords:
rail-way wheel; vibration dampers; modal analysis
Available at various institutes of the ASCR
Modální analýza pryží odpruženého kola Stadler se dvěma variantami listových tlumičů
Cílem těchto modálních analýz bylo identifikovat vlastní frekvence a tlumení pryžo-odpruženého kola a porovnat jak obě varianty tlumičů mezi sebou sebou, tak s dřívějším měřením gumo-odpruženého kola ...
Development of autonomous experimental system to analyse yield surfaces distortion due to multiaxial ratcheting
Svárovský, Jiří; Parma, Slavomír; Štefan, Jan; Ciocanel, C.; Feigenbaum, H. P.; Marek, René; Klepač, Vilém; Plešek, Jiří
2023 - English
Multiaxial ratcheting is a failure mode of structures characterized by the accumulation of plastic strain due to cyclic loading. Despite several models having been developed to predict multiaxial ratcheting, they often fail when validated with experimental data collected under a wide array of loading conditions. In this study, an experimental setup was developed and an autonomous testing procedure was used to experimentally analyze the evolution of the yield surface shape due to cyclic biaxial loading. Thin-walled tubular test specimens were made of 304L steel with a diameter of 40mm and underwent axial-torsional testing using the Instron 8852 system. The total axial strain was increased from 0 to 1% while the total shear strain underwent 5 cycles with the strain amplitude of 0.5% and the mean strain of 0.5%. Three yield surfaces were measured after the straining sequence was completed. Results showed strong directional distortional hardening and good agreement between the flow vectors and the normals to the yield surface, lending support to the associative flow rule.
Keywords:
yield surface distortion; strain hardening; multiaxial ratcheting; flow rule
Fulltext is available at external website.
Development of autonomous experimental system to analyse yield surfaces distortion due to multiaxial ratcheting
Multiaxial ratcheting is a failure mode of structures characterized by the accumulation of plastic strain due to cyclic loading. Despite several models having been developed to predict multiaxial ...
Vyjádření ke zprávě ÚJV DITI 2301/1308 – Analýzy dopadu zvýšení výkonu na hodnocení radiačního bobtnání, radiačního tečení a IASCC VČR
Štefan, Jan; Gabriel, Dušan
2023 - Czech
Tato technická zpráva byla vypracována pro Státní úřad pro jadernou bezpečnost v rámci expertní podpory v oblasti hodnocení pevnosti a životnosti. Zpráva byla zpracována jako posudek k technické zprávě: ÚJV DITI 2301/1308: Analýzy dopadu zvýšení výkonu na hodnocení radiačního bobtnání, radiačního tečení a IASCC VČR, vypracované pracovníky oddělení Hodnocení pevnosti a životnosti ÚJV Řež, a. s. Účelem zprávy T575/23 bylo podat SÚJB nezávislé vyjádření k výrokům autorů zprávy ÚJV. V souladu s požadavkem SÚJB byl při zpracování posudku kladen důraz zejména na materiálové aspekty dané problematiky. Posuzovatel zaujal k předložené zprávě ÚJV souhlasné stanovisko s jedinou významnější námitkou vůči jednomu aspektu problematiky radiačního bobtnání a s několika minoritními připomínkami vesměs formální povahy. This technical report has been elaborated for the State Office for Nuclear Safety (SÚJB) in the framework of expert support in the field of strength and durability assessment. The report was elaborated as a review on the technical report: ÚJV DITI 2301/1308: Analýzy dopadu zvýšení výkonu na hodnocení radiačního bobtnání, radiačního tečení a IASCC VČR elaborated by the staff of the Strength and lifetime evaluation department of ÚJV Řež, a. s. The purpose of the report T575/23 was to provide the SÚJB with an independent review of the statements made by the authors of the ÚJV report. In accordance with the requirement of SÚJB, the emphasis was placed on the material aspects of the issue. The reviewer expressed a favourable attitude towards the submitted UJV report with only one major objection to one aspect of the issue of radiation swelling and a few minor comments of a mostly formal nature.
Keywords:
nuclear energy; material engineering; safety assessment
Available at various institutes of the ASCR
Vyjádření ke zprávě ÚJV DITI 2301/1308 – Analýzy dopadu zvýšení výkonu na hodnocení radiačního bobtnání, radiačního tečení a IASCC VČR
Tato technická zpráva byla vypracována pro Státní úřad pro jadernou bezpečnost v rámci expertní podpory v oblasti hodnocení pevnosti a životnosti. Zpráva byla zpracována jako posudek k technické ...
Předběžné výsledky měření na HVAC jednotce pro H2-Bus s chladivy R454C a R513A
Blahut, Aleš; Kordík, Jozef; Šulc, V.; Vinš, Václav
2023 - Czech
Technická zpráva shrnuje předběžné vyhodnocení experimentálních zkoušek chladící jednotky a tepelného čerpadla (HVAC) pro vodíkový autobus s chladivy R454C a R513A. V klimakomoře Elektrotechnického zkušebního ústavu, s. p. v Praze Troji byla v říjnu 2023 podrobně testována zkušební HVAC jednotka v režimech klimatizace a tepelného čerpadla při teplotách okolí od -25 °C do +45 °C. Ve zprávě jsou analyzovány základní výkonové parametry HVAC jednotky zahrnující topný a chladící výkon na kondenzátoru, resp. výparníku, topné a chladící faktory okruhu a izoentropickou účinnost kompresoru.
Available at various institutes of the ASCR
Předběžné výsledky měření na HVAC jednotce pro H2-Bus s chladivy R454C a R513A
Technická zpráva shrnuje předběžné vyhodnocení experimentálních zkoušek chladící jednotky a tepelného čerpadla (HVAC) pro vodíkový autobus s chladivy R454C a R513A. V klimakomoře Elektrotechnického ...
Experimental and numerical investigation of the frequency-modal properties of the switch box
Zolotarev, Igor; Pešek, Luděk; Bula, Vítězslav; Šnábl, Pavel; Gabriel, Dušan; Mračko, Michal; Masák, Jan
2023 - English
The research is linked to increase of seismic resistivity of data board switch boxes. Therefore we deal with numerical modelling of the box for finding the hot spots and designing appropriate modifications. This paper deals with numerical and experimental frequency-modal properties of the switch box and mutual comparison for numerical model validation.
Keywords:
modal analysis; natural frequencies; eigen-modes of vibration
Available at various institutes of the ASCR
Experimental and numerical investigation of the frequency-modal properties of the switch box
The research is linked to increase of seismic resistivity of data board switch boxes. Therefore we deal with numerical modelling of the box for finding the hot spots and designing appropriate ...
Calibrated finite volume method-based simulation framework for laser shock peening
Isoz, Martin; Gruber, Pavel; Schmidt, Jaroslav; Kubíčková, Lucie; Štefan, Jan; Kaufman, Jan; Brajer, Jan; Gabriel, Dušan
2023 - English
Modern and highly competitive industry seeks components with high strength and fatigue resistance. Both of these properties may be improved by peening of the component surface and the standard peening processes, such as the shot peening, are widely used in both automotive and aerospace industries. The laser shock\npeening (LSP), i.e. hardening of the material surface by a laser-induced shock wave, is a modern alternative to the standard peening. Concurrently, the industrial applications of LSP are promoted by recently emerged affordable high power-density lasers. However, the nascent LSP applications are still mostly a trial-and-error\nprocesses based on an extensive experimental testing. Consequently, we focused on a highly application-driven development of a framework for LSP modeling, and the internal workings and results of which are the focus of the present contribution.
Keywords:
laser shock peening; modeling; finite volume method; OpenFOAM
Fulltext is available at external website.
Calibrated finite volume method-based simulation framework for laser shock peening
Modern and highly competitive industry seeks components with high strength and fatigue resistance. Both of these properties may be improved by peening of the component surface and the standard peening ...
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