No (20981)
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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 ...
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. ...
Influence of ball material on the resulting fatigue life of thermal sprayed HVOF coatings in dynamic impact testing
Duliškovič, J.; Daniel, Josef; Houdková, Š.
2024 - English
Dynamic impact wear, i.e. contact between two components in the presence of high cyclic local loads, is a challenging failure mode that occurs in many mechanical applications. Many previous studies have confirmed that dynamic impact testing is suitable for evaluating the contact fatigue of thermal sprayed coatings. However, the effect of the test parameters on the resulting lifetime is unclear. The aim of this study describes the effect of the ball material used in the dynamic impact test on the resulting fatigue life of the HVOF thermal sprayed coating. Three test balls made of WC/Co alloy, Si3N4 silicon nitride and 440 C steel were chosen for this study. Dynamic impaction testing was carried out on the Cr3C2-NiCr coating, which was sprayed by HVOF on a 1.2376 high-speed steel substrate. The impact lifetime was described by the number of critical impacts, i.e. the number of impacts before coating fatigue occurs. Furthermore, the depth and volume of impact craters were measured. Using scanning electron microscopy (SEM), the surface of the impacts as well as the microstructure of the coating on the cross-section in the region of the impacts were observed. Furthermore, the mechanism of crack propagation in the coating and the microstructure of the indentor were investigated.
Keywords:
dynamic impact test; HVOF; Cr3C2-NiCr; fatigue
Available at various institutes of the ASCR
Influence of ball material on the resulting fatigue life of thermal sprayed HVOF coatings in dynamic impact testing
Dynamic impact wear, i.e. contact between two components in the presence of high cyclic local loads, is a challenging failure mode that occurs in many mechanical applications. Many previous studies ...
Functional Tungsten-based thin films and their characterization
Košelová, Zuzana; Horáková, L.; Sobola, Dinara; Burda, Daniel; Knápek, Alexandr; Fohlerová, Z.
2024 - English
Anodizing is a technique by which thin oxide layers can be formed on a surface. Thin oxide layers have been found to be useful in a variety of applications, including emitters of electrons. Tungsten is still a common choice for cold field emitters in commercial microscopy applications. Its suitable quality can be further improved by thin film deposition. Not only the emission characteristic can be improved, but also the emitter operating time can be extended. Tungsten oxide is known for its excellent resistance to corrosion and chemical attack due to its stable crystal structure and strong chemical bonds between tungsten and oxygen atoms. Many techniques with different advantages and disadvantages have been used for this purpose. Anodization was chosen for this work because of the controllable uniform coverage of the material and its easy availability without the need for expensive complex equipment. The anodizing process involves applying an electrical potential to tungsten while it is immersed in an electrolyte solution. This creates a thin layer of tungsten oxide on the surface of the metal. The thickness and properties of the resulting oxide layer can be controlled by adjusting the anodization conditions, such as the electrolyte solution, voltage, and the duration of the process. In this work, H3PO4 was used as the electrolyte to test whether these tungsten oxide layers would be useful for electron emitters, for use in electron guns and other devices that require high-quality electron emitters. The properties were evaluated using appropriate techniques. In general, anodization of tungsten to form thin layers of tungsten oxide layers is a promising technique for producing high quality electron emitters.
Keywords:
cold-field emission; thin layer deposition; tungsten oxide; resonance enhanced tunneling; anodization
Available at various institutes of the ASCR
Functional Tungsten-based thin films and their characterization
Anodizing is a technique by which thin oxide layers can be formed on a surface. Thin oxide layers have been found to be useful in a variety of applications, including emitters of electrons. Tungsten ...
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 ...
Palingenesis - the restoration of everything? (Matthew 19,28)
Dus, Jan A
2024 - Czech
In Matthew’s version of Jesus’ promise (Matthew 19:28–30), in contrast to Mark and Luke, there is no explicit mention of the present time, the restitution of all that the followers of Jesus left behind is thus pushed forward to the future, in which they will take over the reigns with the Son of Man. The promise features the rare term “palingenesis”, whose precise temporal and factual determination cannot be deduced from the sentence itself. While in Mt 19:28 palingenesis is, according to the prevailing interpretation, a synonym for the future restoration of the universe, in Tit 3:5 (the only other occurrence in the NT) the same word refers to the rebirth of some people that took place in the past (at baptism). Even non-biblical literature does not provide a clear precedent - palingenesis tends to be set both in the past and in the future, it concerns both the world and individuals or groups (Israel). – The syntax and punctuation of the Greek sentence show that both interpretations are equally possible: palingenesis can be related either (A) to the following verbal form “sitting (the Son of Man on the throne)”, i.e. to the future, or (B) to the preceding verbal form “following (disciples behind Jesus)”, i.e. into the past, in addition, there is a third, open option (C). In the 16th-century Greek, Latin, and Czech versions, all possibilities are represented: Erasmus punctuates the Vulgate differently (B), Beza first respects the Vulgate (A), but in his Annotations he considers the second solution (B), in the fourth and fifth editions he finally leaves the matter open (C), two Czech translations from the first half of the 16th century (Náměšť 1533, Melantrich 1556/57) hesitate in the dilemma between the Vulgate and Erasmus (C), most Brethren translations starting with Blahoslav (1564) deviate from the Vulgate (B), only the Six-Volume Kralice Bible from 1593/94 (“Kralická Šestidílka”) hesitates (C), in “Kralická Šestidílka” and in the Kralice New Testament from 1601 the Brethren pay equal attention to both interpretations in a rather extensive note, which, for its balance, is a nice proof of intellectual openness and tolerance. Like Beza, the Brethren add a new aspect to interpretation (B): palingenesis can mean the renewal of the whole world thanks to the Gospel and the first coming of the Messiah. – Considering the dynamic development in the 16th century, it is surprising that all ten tracked Czech translations from around the 20th century agree on only one variant (A). Option (B) seems to be in danger of unfair oblivion. Therefore, in conclusion, we allow ourselves to propose a new, somewhat looser translation or paraphrase of verse Mt 19:28 in the spirit of Kralice: “Amen, I say to you, it was you who followed me when I came to renew the world with the gospel, and when the Son of Man sits on the throne of his glory, it will be you again who will sit on twelve thrones and judge the twelve tribes of Israel.” V Matoušově verzi Ježíšova zaslíbení (Mt 19,28–30) oproti Markovi a Lukášovi chybí výslovná zmínka o přítomnosti: restituce všeho, co Ježíšovi následovníci opustili, se tak posouvá až do budoucnosti, ve které se chopí vlády spolu se Synem člověka. V zaslíbení figuruje raritní pojem „palingeneze“, jehož bližší časové a věcné určení nelze ze samotného souvětí odvodit. Zatímco v Mt 19,28 je palingeneze podle převažujícího výkladu synonymem pro budoucí obnovu veškerenstva, v Tt 3,5 (jediný další výskyt v NZ) odkazuje totéž slovo na znovuzrození některých lidí, ke kterému došlo v minulosti (při křtu). Ani nebiblická literatura nepřináší jednoznačný precedens – palingeneze bývá zasazována jak do minulosti, tak i do budoucnosti, týká se jak světa, tak i jednotlivců či skupin (Izraele). – Syntax a interpunkce řeckého souvětí ukazují, že oba výklady jsou rovnocenné: palingenezi lze vztáhnout buď (A) k následujícímu výrazu pro „usednutí (Syna člověka na trůn)“, tedy do budoucnosti, anebo (B) k předchozímu výrazu pro „následování (učedníků za Ježíšem)“, tedy do minulosti, kromě toho existuje (C) výklad otevřený. V řeckých, latinských a českých verzích ze 16. století jsou zastoupeny všechny možnosti: Erasmus interpunkčně opravuje Vulgátu (B), Beza nejprve respektuje Vulgátu (A), v anotacích však zvažuje druhé řešení (B), ve čtvrtém a pátém vydání nakonec nechává věc otevřenou (C), v dilematu mezi Vulgátou a Erasmem váhají i dva české překlady z první poloviny 16. stol. (náměšťský 1533, melantrišský 1556/57) (C), většina bratrských překladů počínaje Blahoslavem (1564) se odchyluje od Vulgáty (B), jen kralická Šestidílka (1593/94) váhá (C), v Šestidílce i v kralickém Novém zákoně z r. 1601 Bratří věnují oběma výkladům rovnocennou pozornost v poměrně rozsáhlé poznámce, která je pro svou vyváženost pěkným dokladem intelektuální otevřenosti a tolerance, podobně jako Beza připojují k výkladu (B) nový aspekt: palingeneze může znamenat obnovení celého světa díky evangeliu a prvnímu příchodu Mesiáše. – Vzhledem k dynamickému vývoji v 16. století je překvapivé, že všech deset sledovaných českých překladů z období kolem 20. století se shoduje jen na jedné variantě (A). Zdá se, že variantě (B) hrozí nespravedlivé zapomenutí. Proto si na závěr dovolujeme navrhnout nový, poněkud volnější překlad či parafrázi verše Mt 19,28 v kralickém duchu: „Amen, pravím vám, vy jste šli za mnou, když jsem přišel obnovit svět evangeliem, a až Syn člověka usedne na trůn své slávy, budete to zase vy, kdo usednete na dvanáct trůnů a budete soudit dvanáct kmenů Izraele.“
Keywords:
palingenesis; Gospel of Matthew; Kralice Bible; Erasmus of Rotterdam; Theodore Beza; Vulgate; Czech Bible translations
Available at various institutes of the ASCR
Palingenesis - the restoration of everything? (Matthew 19,28)
In Matthew’s version of Jesus’ promise (Matthew 19:28–30), in contrast to Mark and Luke, there is no explicit mention of the present time, the restitution of all that the followers of Jesus left ...
Czech Travels to Richard Wagner
Fránek, Michal; Kopecký, J.
2024 - Czech
The study explores the phenomenon of Czech travels to famous German composer Richard Wagner and to the places associated with his cult (Munich, Bayreuth, Zurich, etc.). It focuses on the Wagnerian journeys – accomplished and not – of Czech composers (Bedřich Smetana, Antonín Dvořák, Zdeněk Fibich, Josef Bohuslav Foerster), performers (Ema Destinnová, Karel Burian, etc.), music critics (Otakar Hostinský, V. V. Zelený), painters (Jaroslav Čermák) and writers (Julius Zeyer, Jaroslav Maria, Teréza Nováková), tracing their different motivations. Studie zkoumá fenomén českých cest za slavným německým skladatelem Richardem Wagnerem a do míst spojených s jeho kultem (Mnichov, Bayreuth, Curych atd.). Zaměřuje se na wagnerovské cesty – uskutečněné i neuskutečněné – českých skladatelů (Bedřich Smetana, Antonín Dvořák, Zdeněk Fibich, Josef Bohuslav Foerster), interpretů (Ema Destinnová, Karel Burian aj.), hudebních kritiků (Otakar Hostinský, V. V. Zelený), malířů (Jaroslav Čermák) a spisovatelů (Julius Zeyer, Jaroslav Maria, Teréza Nováková), přičemž sleduje jejich různé motivace.
Keywords:
Richard Wagner; travelling to artists
Available at various institutes of the ASCR
Czech Travels to Richard Wagner
The study explores the phenomenon of Czech travels to famous German composer Richard Wagner and to the places associated with his cult (Munich, Bayreuth, Zurich, etc.). It focuses on the Wagnerian ...
Verification of the dynamic properties of a new model turbine wheel with free blades
Voronova, Evgeniya; Procházka, Pavel; Maturkanič, Dušan; Mekhalfia, Mohammed Lamine; Hodboď, Robert
2024 - English
The paper describes a new experimental model of turbine wheel with free blades. Verification tests were carried out using a Doppler laser vibrometer, with a focus on the equipment parameters under various conditions. The measurements were performed in the Laboratory of Rotational Laser Vibrometry originated at the Institute of Thermomechanics AS CR, v.v.i.
Keywords:
natural frequencies; vibration; blade; laser; turbine
Available at various institutes of the ASCR
Verification of the dynamic properties of a new model turbine wheel with free blades
The paper describes a new experimental model of turbine wheel with free blades. Verification tests were carried out using a Doppler laser vibrometer, with a focus on the equipment parameters under ...
Modification of cooling system for laboratory measurement of rotor blade vibration
Maturkanič, Dušan; Procházka, Pavel; Hodboď, Robert; Voronova, Evgeniya; Mekhalfia, Mohammed Lamine
2024 - English
Last year, the replacement of the turbine wheel model was completed in the Laboratory of Rotational Laser Vibrometry of the Institute of Thermomechanics AS CR, v.v.i. Based on previous experience and the expected higher operating load planned for the new wheel, the cooling system was modified at the same time. The paper describes the main effort in this direction and the results that clarify the previous damage of the measuring device.
Keywords:
blade; vibration; cooling system; measurement; laboratory
Available at various institutes of the ASCR
Modification of cooling system for laboratory measurement of rotor blade vibration
Last year, the replacement of the turbine wheel model was completed in the Laboratory of Rotational Laser Vibrometry of the Institute of Thermomechanics AS CR, v.v.i. Based on previous experience and ...
PROPERTIES OF NANOCRYSTALLINE FE-NI PARTICLES PREPARED BY THERMAL REDUCTION OF OXALATE PRECURSORS
Švábenská, Eva; Roupcová, Pavla; Havlíček, Lubomír; Schneeweiss, Oldřich
2024 - English
Recent technological advancements require development of cost-effective and high-performance magnets \nwhich ideally do not contain rare earth metals or noble metals. The promising candidates are Fe-Ni-based \nalloys, in particular, the Fe50Ni50 L10 phase (tetrataenite), which has a great perspective for producing hard \nmagnetic materials. Our study explores a promising method for preparing nanoparticles of Fe-Ni alloy from an \niron-nickel oxalate precursor. The coprecipitation method was employed to prepare oxalate precursors, \nfollowed by controlled thermal decomposition in a reducing hydrogen atmosphere. The morphology and \nproperties of the resulting particles were analysed using scanning electron microscopy (SEM) coupled with \nenergy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Mössbauer spectroscopy (MS), and \nmagnetic measurements.\nThe SEM analysis revealed that the particles have approximately cube-shaped unit cell morphology with a\nsize in a range of 1 - 2 μm. Upon annealing, the samples contain multiple phases with varying Fe-Ni content.\nMagnetic measurements confirmed the formation of magnetically suitable Fe-Ni phases in the samples after \nannealing. Mössbauer spectroscopy emerged as a highly effective method for characterizing individual phases \nof the Fe-Ni system.
Keywords:
Magnetic materials; thermal decomposition; Mössbauer spectroscopy
Available at various institutes of the ASCR
PROPERTIES OF NANOCRYSTALLINE FE-NI PARTICLES PREPARED BY THERMAL REDUCTION OF OXALATE PRECURSORS
Recent technological advancements require development of cost-effective and high-performance magnets \nwhich ideally do not contain rare earth metals or noble metals. The promising candidates are ...
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