No (14409)
Number of found documents:
14409
Published from
to
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 ...
QUANTUM-MECHANICAL STUDY OF INTERNAL STRUCTURAL TRANSFORMATIONS IN Pb-SUPERSATURATED Pb-Sn ALLOYS
Friák, Martin; Čípek, Petr; Pavlů, J.; Roupcová, Pavla; Miháliková, Ivana; Msallamová, Š.; Michalcová, A.
2024 - English
Motivated by a decades-long controversy related to the crystal structure of Pb-supersaturated solid solutions of Pb in Sn, we have performed a quantum-mechanical study of these materials. Focusing on both body-centred-tetragonal beta-Sn and simple-hexagonal gamma-Sn structures, we have computed properties of two alloys with the chemical composition Pb5Sn11, i.e. 31.25 at. % Pb, which is close to the composition of the experimentally found alloy (30 at. % Pb). The 16-atom computational supercells were designed as multiples of the elemental beta- and gamma-Sn unit cells, where the Pb atoms were distributed according to the special quasi-random structure (SQS) concept. Full structural relaxations of both beta- and gamma-phase-based alloys resulted in very significant re-arrangements into structures which do not exhibit any apparent structural features typical for the original alloys, and are, therefore, difficult to classify. The formation energies of the beta- and gamma-phase-originating equilibrium phases are 50 meV/atom and 53 meV/atom, respectively. Therefore, they are not stable with respect to the decomposition into the elemental lead and tin. Moreover, our calculations of elastic constants of both phases revealed that they are close to mechanical instability. Our results indicate that the studied Pb-supersaturated Pb-Sn solid solutions may be prone to structural instability, transformations into different phases and decomposition. Our findings may contribute into the identification of the reason why the subsequent experimental studies did not reproduce the initial published data.
Keywords:
tin; crystal; Pb-Sn alloys; stability; supersaturation; quantum-mechanical calculations
Available at various institutes of the ASCR
QUANTUM-MECHANICAL STUDY OF INTERNAL STRUCTURAL TRANSFORMATIONS IN Pb-SUPERSATURATED Pb-Sn ALLOYS
Motivated by a decades-long controversy related to the crystal structure of Pb-supersaturated solid solutions of Pb in Sn, we have performed a quantum-mechanical study of these materials. Focusing on ...
IPC-IOPC 2024: Abstract book
Bek, Jiří; Votočková Frojdová, Jana
2024 - English
Keywords:
Palaeobotany; palynology; plants; spores
Available at various institutes of the ASCR
IPC-IOPC 2024: Abstract book
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 ...
EFFECT OF STEEL COMPOSITION ON ITS BEHAVIOUR IN THE LIQUID LEAD ENVIRONMENT
Pazderova, M.; Hojná, A.; Vít, J.; Hadraba, Hynek; Čižek, J.
2024 - English
Ferritic-martensitic Eurofer-97 and oxide dispersion strengthened (ODS) Eurofer steels are potential candidates for structural applications in advanced nuclear reactors. Influence of scandium, yttrium, and aluminum addition was studied at 600 degrees C using 10-6 wt.% oxygen concentration. Microstructure and corrosion behaviour was evaluated after 500 h and 1000 h of exposure to liquid lead. Microscopical investigation identified oxidation, solution- based attack, and Pb penetration into the material. Addition of scandium and aluminum changed the mechanism of corrosion attack. Eurofer-97 was partially protected by outer oxide and inner oxidation and Pb penetration was found. In contrast ODS-Eurofer steels after 1000 h of exposure showed mainly inner oxidation and SBA including Pb penetration into the steel. The inner oxidation consisted of Pb+Cr-O and Cr-O+Al-O layers mixture. Degradation of ODS steel was significantly lower than Eurofer-97. It seems that the inner oxidation layer beneath the surface did not prevent the Pb penetration but protected the surface from dissolution.
Keywords:
corrosion behavior; flowing lead; ods steels; pb; Ferritic-martensitic steel; ods; liquid Pb; oxidation; nuclear application
Available at various institutes of the ASCR
EFFECT OF STEEL COMPOSITION ON ITS BEHAVIOUR IN THE LIQUID LEAD ENVIRONMENT
Ferritic-martensitic Eurofer-97 and oxide dispersion strengthened (ODS) Eurofer steels are potential candidates for structural applications in advanced nuclear reactors. Influence of scandium, ...
QUANTUM-COMPUTING STUDY OF THE ELECTRONIC STRUCTURE OF CRYSTALS: THE CASE STUDY OF SI
Ďuriška, Michal; Miháliková, Ivana; Friák, Martin
2024 - English
Quantum computing is newly emerging information-processing technology which is foreseen to be exponentially faster than classical supercomputers. Current quantum processors are nevertheless very limited in their availability and performance and many important software tools for them do not exist yet. Therefore, various systems are studied by simulating the run of quantum computers. Building upon our previous experience with quantum computing of small molecular systems (see I. Mihalikova et al., Molecules 27 (2022) 597, and I. Mihalikova et al., Nanomaterials 2022, 12, 243), we have recently focused on computing electronic structure of periodic crystalline materials. Being inspired by the work of Cerasoli et al. (Phys. Chem. Chem. Phys., 2020, 22, 21816), we have used hybrid variational quantum eigensolver (VQE) algorithm, which combined classical and quantum information processing. Employing tight-binding type of crystal description, we present our results for crystalline diamond-structure silicon. In particular, we focus on the states along the lowest occupied band within the electronic structure of Si and compare the results with values obtained by classical means. While we demonstrate an excellence agreement between classical and quantum-computed results in most of our calculations, we further critically check the sensitivity of our results with respect to computational set-up in our quantum-computing study. A few results were obtained also using quantum processors provided by the IBM.
Keywords:
computation; Quantum computing; crystals; tight-binding method; quantum-mechanical calculations
Available at various institutes of the ASCR
QUANTUM-COMPUTING STUDY OF THE ELECTRONIC STRUCTURE OF CRYSTALS: THE CASE STUDY OF SI
Quantum computing is newly emerging information-processing technology which is foreseen to be exponentially faster than classical supercomputers. Current quantum processors are nevertheless very ...
Geological and geotechnical characterisation of the mining environment - URF Bukov II - Interim report III
Soejono, I.; Bukovská, Z.; Rukavičková, L.; Švagera, O.; Chabr, T.; Souček, Kamil; Vavro, Martin; Morávek, R.; Levý, O.; Sosna, K.; Kryl, J.; Řihošek, J.; Zelinková, T.; Dobeš, P.; Hanák, J.; Čermák, F.; Kašpar, R.; Mareček, L.; Nedvěd, J.; Vavro, Leona; Myška, O.; Janeček, Ivan
2024 - Czech
This report describes the work carried out in the third year of the public contract Geological and geotechnical characterisation of the rock environment – the Bukov URF II. The characterisation and descriptive works are directly related to the excavation of the premises for the future underground laboratory. These include in particular: geological and geotechnical documentation of the faces and walls of the workings, petrographic, mineralogical and structural geological documentation, hydrogeological characterisation of the environment, as well as determination of the physical and mechanical properties of the rock-mass in situ and in the laboratory, geophysical characterisation and monitoring of the seismic effects of blasting. The report also includes the newly developed rock mass\nclassification system and the results of its testing on the Bukov URF II site. The report includes also brief overview of the work planned for the following year of the project. Tato zpráva popisuje práce zhotovené v třetím roce řešení veřejné zakázky Geologická a geotechnická charakterizace horninového prostředí – PVP Bukov II. Charakterizační a popisné práce přímo navazují na ražbu prostor pro budoucí podzemní laboratoř a zahrnují zejména: geologické a geotechnické dokumentace čeleb a stěn díla, petrografickou, mineralogickou a strukturně geologickou dokumentaci, hydrogeologickou charakterizaci prostředí, dále stanovení fyzikálně-mechanických vlastností horninového masivu in situ a v laboratoři, geofyzikální charakterizaci, monitoring seismických účinků trhacích prací a charakterizaci EDZ. Zpráva také obsahuje nově navržený klasifikační systém horninových bloků a výsledky jeho testování na prostředí PVP Bukov II. Zpráva je doplněna stručným přehledem prací plánovaných pro následující rok řešení projektu.
Keywords:
Bukov URF; geological documentation; 3D model; petrography; geochemistry; petrophysical data; natural radioactivity; physico-mechanical and geotechnical properties; seismic tomography; excavation induced vibration measurement; rock mass classification system
Available on request at various institutes of the ASCR
Geological and geotechnical characterisation of the mining environment - URF Bukov II - Interim report III
This report describes the work carried out in the third year of the public contract Geological and geotechnical characterisation of the rock environment – the Bukov URF II. The characterisation and ...
Determination of in situ stress state at Bukov Bukov URF II - search of the stress state measurement methods and study of their use in the process of construction and operation of a deep geological repository.
Vavro, Martin; Waclawik, Petr; Souček, Kamil; Staš, Lubomír; Koníček, Petr; Jiránková, Eva; Schuchová, Kristýna; Kukutsch, Radovan; Kajzar, Vlastimil
2024 - Czech
The presented search summarizes main measurement methods and their corresponding technical instrumentation, which were used in the past to determine the stress state of the rock\nmass, both in the conditions of Bukov URF I or the Rožná mine respectively, and especially in the environment of selected foreign underground research laboratories. The key results obtained during these stress measurements are also compiled. The findings are then reflected in the proposed method of rock mass stress measurement and monitoring in various stages of the process of preparing and operating a deep geological repository (DGR) in the Czech Republic. From the conducted search of the crucial published studies and the results of in situ experiments, it follows that the most commonly used methods of stress measurement worldwide are mainly hydraulic fracturing of borehole walls (hydrofracturing) and the overcoring method. These two methods were also proposed as the most suitable for the stage of selecting the final site of the DGR in the Czech Republic. In the phase of construction the DGR, it was recommended to extend them by the method of inverse analysis of convergence measurements. For the purposes of measuring stress changes during the construction and operation of the DGR, monitoring using conical tensometric CCBM probes was recommended as the most suitable. Rešerše prezentuje hlavní metody měření a jim odpovídající technickou instrumentaci, které byly v minulosti použity pro stanovení napětí horninového masivu, a to jak v podmínkách PVP Bukov I, respektive dolu Rožná, tak zejména v prostředí vybraných zahraničních podzemních výzkumných laboratoří. Shrnuty jsou rovněž stěžejní výsledky, které byly při těchto měřeních získány. Zjištěné poznatky jsou pak reflektovány v návrhu způsobu měření a monitoringu napětí v různých fázích procesu přípravy a provozu hlubinného úložiště (HÚ) v ČR. Z provedené rešerše stěžejních publikovaných studií a výsledků in situ experimentů vyplývá, že celosvětově nejčastěji používanými způsoby napěťových měření jsou zejména hydraulické štěpení stěn vrtů (hydrofracturing) a metoda odlehčeného vrtného jádra (overcoring). Tyto dvě metody byly rovněž navrženy jako nejvhodnější pro fázi výběru finální lokality HÚ v ČR. Ve fázi budování HÚ bylo doporučeno jejich rozšíření o metodu inverzní analýzy konvergenčních měření. Pro účely měření změn napětí ve stádiu přípravy a provozu HÚ byl jako nejvhodnější doporučen monitoring pomocí tenzometrických CCBM sond.
Keywords:
high level radioactive waste; geological disposal; deep repository; long-term stability of the repository; Bukov URF; rock mass stress; hydrofracturing; overcoring method; tensometric conical probes; acoustic logging; optical logging; long-term stress monitoring; convergence measurement; numerical modelling
Available on request at various institutes of the ASCR
Determination of in situ stress state at Bukov Bukov URF II - search of the stress state measurement methods and study of their use in the process of construction and operation of a deep geological repository.
The presented search summarizes main measurement methods and their corresponding technical instrumentation, which were used in the past to determine the stress state of the rock\nmass, both in the ...
Book of Abstracts. 19th Youth symposium on experimental solid mechanics
Kytýř, Daniel; Zlámal, Petr; Pagliaro, A.; Doktor, T.
2024 - English
The YSESM symposium provides a forum for young researchers and engineers, PhD students and students dealing with subjects of experimental mechanics. The Symposium concentrates on current work in all areas of experimental research and its application in solid and fluid mechanics. The topic will particularly concern to: Conventional and advanced experimental methods in solid and fluid mechanics - Non-destructive testing and inspection - Measurements in material science - Computer assisted testing and simulation - Engineering design simulation - Hybrid methods, experimental techniques – Numerical simulation - Optical methods and image processing - Measurements in biomechanics - Sensor techniques for micro- and nano-applications - Measurement methods for forensic engineering
Keywords:
experimental mechanics; solid mechanics; fluid mechanics
Available at various institutes of the ASCR
Book of Abstracts. 19th Youth symposium on experimental solid mechanics
The YSESM symposium provides a forum for young researchers and engineers, PhD students and students dealing with subjects of experimental mechanics. The Symposium concentrates on current work in all ...
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 ...
NRGL provides central access to information on grey literature produced in the Czech Republic in the fields of science, research and education. You can find more information about grey literature and NRGL at service web
Send your suggestions and comments to nusl@techlib.cz
Provider
Other bases