No (14409)
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14409
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Computational and experimental assessment of natural frequencies in a bladed disk system
Mekhalfia, Mohammed Lamine; Procházka, Pavel; Maturkanič, Dušan; Voronova, Evgeniya; Hodboď, Robert
2024 - English
This paper examines the modal characteristics of a bladed disk in rotating machinery systems using a combination of analytical and experimental modal analysis methods. The analysis involves measuring natural frequencies and mode shapes under different operational conditions. A comparative analysis is conducted to assess modal properties obtained from both analytical and experimental approaches, while also considering the influence of rotation speed. Additionally, Finite Element Method (FEM) outputs are used to accurately position the strain gauge. Integrating these techniques provides a comprehensive understanding of the bladed disk's behaviour under varying rotational speeds, enhancing result accuracy and facilitating thorough investigation within rotating machinery systems.
Keywords:
natural frequencies; FEM; LDV; strain gauge
Available at various institutes of the ASCR
Computational and experimental assessment of natural frequencies in a bladed disk system
This paper examines the modal characteristics of a bladed disk in rotating machinery systems using a combination of analytical and experimental modal analysis methods. The analysis involves measuring ...
Numerické optimalizační metody
Lukšan, Ladislav
2024 - Czech
Tato zpráva popisuje teoretické i praktické vlastnosti numerických metod pro nepodmíněnou optimalizaci. Studují se metody pro obecné i speciální optimalizační úlohy, mezi které patří minimalizace součtu čtverců, součtu absolutních hodnot, maximní hodnoty a dalších nehladkých funkcí. Kromě metod pro standardní úlohy středních rozměrů jsou studovány i metody pro rozsáhlé řídké a strukturované úlohy. Velká pozornost je věnována soustavám nelineárních rovnic.\n
Keywords:
Numerická optimalizace; nelineární aproximace; systémy nelineárních rovnic; algoritmy
Available on request at various institutes of the ASCR
Numerické optimalizační metody
Tato zpráva popisuje teoretické i praktické vlastnosti numerických metod pro nepodmíněnou optimalizaci. Studují se metody pro obecné i speciální optimalizační úlohy, mezi které patří minimalizace ...
MINOR PHASES IN TIN-RICH HISTORICAL MATERIALS
Michalcová, A.; Msallamová, Š.; Fink, D.; Friák, Martin
2024 - English
The historical organ pipes used to be manufactured from tin and tin-lead alloys. The tin-rich organ pipes usually contained copper as alloying elements, which make them similar to modern lead free soldering materials. The historical organ pipe materials can be used as model materials for natural ageing of soldering materials. Tin pest is a term for modification from white tin to grey tin, which leads to degradation of tin or tin-rich alloys. The influence of individual alloying elements has not been reliably described, yet. Not only on the concentration of the alloying element, but also the distribution may play the important role. In dependence on heat-treatment, the Cu can be in the Sn matrix present in these forms: i) as large intermetallic particles after casting (Cu6Sn5), ii) as solid solution after homogenization annealing and iii) as fine precipitates after ageing. The microstructure of the real historical organ-pipes material was studied and it was proven that contradictionary to the equilibrium phase diagram the Cu enriched was observed.
Keywords:
Metallurgy; tin; copper; tin pest; tem
Available at various institutes of the ASCR
MINOR PHASES IN TIN-RICH HISTORICAL MATERIALS
The historical organ pipes used to be manufactured from tin and tin-lead alloys. The tin-rich organ pipes usually contained copper as alloying elements, which make them similar to modern lead free ...
Studijní zkoušky pevnosti malty v omítce severního průčelí st. zámku Litomyšl
Drdácký, Miloš; Urushadze, Shota; Vála, Ondřej
2024 - Czech
Available at various institutes of the ASCR
Studijní zkoušky pevnosti malty v omítce severního průčelí st. zámku Litomyšl
Assessment of the condition and measuring of properties of the truss and 1st floor ceiling timber structures in the state-owned castle Hrádek u Nechanic, National Cultural Heritage registration no.: 18278/6-619
Kloiber, Michal; Drdácký, Miloš
2024 - Czech
The survey described in this report contains the assessment of physical and mechanical properties of selected beams within timber structures of the truss and 1st floor ceiling in the state-owned castle called Hrádek u Nechanic (Fig. 1.1). The report has been elaborated based on an order placed by Projekční ateliér pro dokumentaci, průzkum a obnovu historických staveb, spol. s.r.o., headquartered Nerudova 1139, 544 01 Dvůr Králové nad Labem. The order included the demand to assess the condition of selected timber elements by Resistograph, and mainly to measure the mechanical properties that can contribute to static assessment and a design of non-intrusive renewal of the unique structures of both the truss and the ceiling. Průzkum popisovaný v této zprávě obsahuje vyhodnocení fyzikálních a mechanických vlastností vybraných nosných trámů dřevěné konstrukce krovu a stropu 1. patra státního zámku Hrádek u Nechanic (obr. 1.1). Podnětem k sepsání zprávy byla objednávka od Projekčního ateliéru pro dokumentaci, průzkum a obnovu historických staveb, spol. s.r.o., se sídlem Nerudova 1139, 544 01 Dvůr Králové nad Labem. Objednávka obsahovala požadavek na posouzení stavu vybraných dřevěných prvků pomocí přístroje Resistograph a především měření mechanických vlastností, které mohou přispět ke statickému posouzení a návrhu šetrné obnovy unikátní konstrukce krovu a stropu.
Keywords:
timber structures; truss; ceiling; state-owned castle; timber mechanical properties
Available at various institutes of the ASCR
Assessment of the condition and measuring of properties of the truss and 1st floor ceiling timber structures in the state-owned castle Hrádek u Nechanic, National Cultural Heritage registration no.: 18278/6-619
The survey described in this report contains the assessment of physical and mechanical properties of selected beams within timber structures of the truss and 1st floor ceiling in the state-owned ...
Flow simulations approach for flocculation tanks
Idžakovičová, Kristýna; Bílek, V.; Haidl, J.; Isoz, Martin; Pivokonský, M.
2024 - English
Flocculation in water treatment facilities plays a key role in the separation of colloidal inorganic and organic substances. Its optimization leads to a significant increase in its efficiency and savings of operational costs. However, it is currently based on trial-and-error experimental approaches. In this contribution, we focus on flow modeling in stirred flocculation tanks that would, after coupling with a calibrated model of particle aggregation, enable simulationbased flocculation optimization. Despite the abundance of literature on stirred tank modeling, there is no universal agreement on the methodology used to describe turbulence nor on the approach to the computational mesh creation. Consequently, there is no unified methodology for simulations and their validation. To address this, we present a best-practice methodology for economical, yet reliable flow simulations in the said device. This methodology includes the choice of the turbulence model, the approach to the design of a high quality mesh suitable for arbitrary geometries, and results evaluation. It is developed based on an extensive literature review, a multitude of flow simulations using several meshes of progressively higher quality and resolution, and various strategies to converge to steady-state flow conditions. The simulation quality indicators used here involve comparison with the experimental data on fluid velocity, stirrer power output, and flow rate through the impeller zone. Additionally, the resulting flow simulation models are compared using tracer transport simulations, hinting at their potential for coupling with particle aggregation models.
Keywords:
flocculation tank; stirring; MRF; CFD; OpenFOAM
Available at various institutes of the ASCR
Flow simulations approach for flocculation tanks
Flocculation in water treatment facilities plays a key role in the separation of colloidal inorganic and organic substances. Its optimization leads to a significant increase in its efficiency and ...
Monitoring chemismu srážkových vod na území NPČS. Závěrečná zpráva za rok 2023-2024
Navrátil, Tomáš; Dobešová, Irena; Rohovec, Jan
2024 - Czech
Keywords:
deposition; bulk precipitation; acidificants; main elements; throughfall
Available at various institutes of the ASCR
Monitoring chemismu srážkových vod na území NPČS. Závěrečná zpráva za rok 2023-2024
Vrt DO 599. Paleomagnetický a magnetomineralogický výzkum. Závěrečná zpráva
Kdýr, Šimon; Pruner, Petr; Uçar, Hakan; Elbra, Tiiu
2024 - Czech
Keywords:
palaeomagnetism; rock-magnetism; greigite
Available at various institutes of the ASCR
Vrt DO 599. Paleomagnetický a magnetomineralogický výzkum. Závěrečná zpráva
The use of thermography in surveys of monuments
Valach, Jaroslav; Eisler, Marek
2024 - Czech
Thermography expands the portfolio of methods that can be used to study the properties of objects in the surrounding world. As recently as a decade ago, the technology was frowned upon for potential military applications controlled, which limited competition in the offer of products and manufacturers and led to high prices of devices based on these principles. It was only thanks to the release of this control that it happened to expand production and make simplified products available to mass use, so get it today for example, a customer can purchase a smartphone with an additional thermographic module for only with a small price increase. Together with the availability of equipment, we observe an increase in the application of thermography in many areas, including surveys of buildings and monuments. Termografie rozšiřuje portfolia metod, jimiž lze studovat vlastnosti objektů okolního světa. Ještě před deseti lety byla tato technologie kvůli potenciálním vojenským aplikacím úzkostlivě kontrolována, což omezovalo konkurenci v nabídce výrobků a výrobců a vedlo k vysokým cenám zařízení založených na těchto principech. Teprve díky uvolnění této kontroly došlo k rozmachu výroby a zpřístupnění zjednodušených výrobků masovému využití, takže si dnes může zákazník například pořídit chytrý telefon s doplňkovým termografickým modulem jen s malým navýšením ceny. Spolu s dostupností zařízení pozorujeme nárůst uplatnění termografie v mnoha oblastech, včetně průzkumů staveb a památek.
Keywords:
thermography; survey of historical structures
Available at various institutes of the ASCR
The use of thermography in surveys of monuments
Thermography expands the portfolio of methods that can be used to study the properties of objects in the surrounding world. As recently as a decade ago, the technology was frowned upon for potential ...
Microstructure modifications of Al-Si-coated press-hardened steel 22MnB5 by laser welding
Šebestová, Hana; Horník, Petr; Mika, Filip; Mikmeková, Šárka; Ambrož, Ondřej; Mrňa, Libor
2024 - English
Weld microstructure depends on the characteristics of welded materials and parameters of welding technology, especially on the heat input that determines the peak temperature and the cooling rate. When the coated sheets are welded, the effect of the chemical composition of the coating must be also considered even though its thickness is only a few tens of microns. During 22MnB5+AlSi laser welding experiments, the ferrite-stabilizing elements of coating modified the weld metal microstructure. Ferrite appeared in a quenched weld metal. The rapid cooling rate accompanying welding with a focused beam limited the homogenization of the weld metal which resulted in the formation of ferritic bands in the regions rich in Si and especially in Al. On the other hand, a high level of homogenization was reached when welding with the defocused beam. The ferritic islands uniformly distributed in the weld metal were formed at 0.4 wt% and 1.6 wt% of Si and Al, respectively. The doubled heat input reduced the Al content to 0.7 wt% insufficient for the ferrite formation at still relatively high cooling rates. Predicting the distribution of ferrite in the weld metal is challenging due to its dependence on various factors, such as cooling rate and the volume of dissolved coating, which may vary with any modifications made to the welding parameters.
Keywords:
laser welding; high-strength steel; microstructure; heat input; ferrite stabilization
Available at various institutes of the ASCR
Microstructure modifications of Al-Si-coated press-hardened steel 22MnB5 by laser welding
Weld microstructure depends on the characteristics of welded materials and parameters of welding technology, especially on the heat input that determines the peak temperature and the cooling rate. ...
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