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Modification of cooling system for laboratory measurement of rotor blade vibration
Maturkanič, Dušan; Procházka, Pavel; Hodboď, Robert; Voronova, Evgeniya; Mekhalfia, Mohammed Lamine
2024 - anglický
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.
Klíčová slova:
blade; vibration; cooling system; measurement; laboratory
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
DYNAMICS OF MACHINES AND MECHANICAL SYSTEMS WITH INTERACTIONS : PROCEEDINGS DYMAMESI 2024
Zolotarev, Igor; Pešek, Luděk; Kozień, M. S.
2024 - anglický
The aim of the DYMAMESI is to facilitate the exchange of up to date information and knowledge among specialists in structural and multibody dynamics, in coupled interacting systems as aero-elasticity, hydro-elasticity, biomechanics, systems with feedbacks and mechatronics. In 2023 will be hosted by Cracow University of Technology, Institute of Applied Mechanics, Section of Dynamics of Systems.
Klíčová slova:
dynamics; vibrations of mechanical systems; vibrodiagnostics; energy transformations
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
DYNAMICS OF MACHINES AND MECHANICAL SYSTEMS WITH INTERACTIONS : PROCEEDINGS DYMAMESI 2024
The aim of the DYMAMESI is to facilitate the exchange of up to date information and knowledge among specialists in structural and multibody dynamics, in coupled interacting systems as aero-elasticity, ...
Stochastic version of the arc-length method
Náprstek, Jiří; Fischer, Cyril
2024 - anglický
The solution of a nonlinear algebraic system using the incremental method, based on pre-defined loading steps, fails in the vicinity of local extrema as well as around bifurcation points. The solution involved the derivation of the so-called ’Arc-Length’ method. Its essence lies in not incrementing the system parameter or any of the independent variables but rather the length of the response curve. The stochastic variant of this method allows for working with a system where system parameters include random imperfections. This contribution presents a variant that tracks the first two stochastic moments. Even in this simple case, interesting phenomena can be observed, such as the disappearance of the energy barrier against equilibrium jump due to random imperfections in the system.
Klíčová slova:
random imperfection; stochastic arc-length method; continuation; numerical method
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Stochastic version of the arc-length method
The solution of a nonlinear algebraic system using the incremental method, based on pre-defined loading steps, fails in the vicinity of local extrema as well as around bifurcation points. The solution ...
Acoustic emission methods in steel bridge degradation identification and monitoring
Šorm, Filip
2024 - anglický
Acoustic emission methods proved to be an effective diagnostic tool in many industrial sectors. The potential of this method in the field of steel bridge diagnostics is explored in this article. The goal is to find the most effective use of this method.
Klíčová slova:
steel bridges; diagnostics; acoustic emission
Plné texty jsou dostupné v digitálním repozitáři Akademie Věd.
Acoustic emission methods in steel bridge degradation identification and monitoring
Acoustic emission methods proved to be an effective diagnostic tool in many industrial sectors. The potential of this method in the field of steel bridge diagnostics is explored in this article. The ...
ENHANCING WELD JOINT INTEGRITY IN S460 HIGH-STRENGTH STEEL PLATES: AN EXPERIMENTAL APPROACH
Al Khazali, Mohammad Sami; Malíková, Lucie; Křivý, V.; Seitl, Stanislav
2024 - anglický
Exploring S460 steel, this research assesses weld toe microstructure and fatigue. It finds that welding affects \nhardness of welded area and fatigue life. These insights are crucial for structural engineering, optimizing welding \npractices for longevity. \nTests confirm increased weld toe hardness correlates with fatigue resistance. This informs design strategies, \nensuring bridge safety under cyclic loads. The study advances understanding of HSS behaviour, influencing future \nwelding techniques.
Klíčová slova:
High-strength steel; weld's toe; cruciform joints; S460; fatigue behaviour
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
ENHANCING WELD JOINT INTEGRITY IN S460 HIGH-STRENGTH STEEL PLATES: AN EXPERIMENTAL APPROACH
Exploring S460 steel, this research assesses weld toe microstructure and fatigue. It finds that welding affects \nhardness of welded area and fatigue life. These insights are crucial for structural ...
PROPERTIES OF NANOCRYSTALLINE FE-NI PARTICLES PREPARED BY THERMAL REDUCTION OF OXALATE PRECURSORS
Švábenská, Eva; Roupcová, Pavla; Havlíček, Lubomír; Schneeweiss, Oldřich
2024 - anglický
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.
Klíčová slova:
Magnetic materials; thermal decomposition; Mössbauer spectroscopy
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
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 ...
Some modifications of the limited-memory variable metric optimization methods
Vlček, Jan; Lukšan, Ladislav
2023 - anglický
Several modifications of the limited-memory variable metric (or quasi-Newton) line search methods for large scale unconstrained optimization are investigated. First the block version of the symmetric rank-one (SR1) update formula is derived in a similar way as for the block BFGS update in Vlˇcek and Lukˇsan (Numerical Algorithms 2019). The block SR1 formula is then modified to obtain an update which can reduce the required number of arithmetic operations per iteration. Since it usually violates the corresponding secant conditions, this update is combined with the shifting investigated in Vlˇcek and Lukˇsan (J. Comput. Appl. Math. 2006). Moreover, a new efficient way how to realize the limited-memory shifted BFGS method is proposed. For a class of methods based on the generalized shifted economy BFGS update, global convergence is established. A numerical comparison with the standard L-BFGS and BNS methods is given.
Klíčová slova:
unconstrained minimization; variable metric methods; limited-memory methods; variationally derived methods; arithmetic operations reduction; global convergence
Plné texty jsou dostupné v digitálním repozitáři NUŠL
Some modifications of the limited-memory variable metric optimization methods
Several modifications of the limited-memory variable metric (or quasi-Newton) line search methods for large scale unconstrained optimization are investigated. First the block version of the symmetric ...
GA 19-07635S: Outputs and Results
Rehák, Branislav
2023 - anglický
This manuscript aims to deliver a survey of results obtained during the solution of the project No. GA19-07635S of the Czech Science Foundation. The timespan dedicated to the work on this project was 1.3.2019 - 30.6.2022. The main area dealt with were\nnonlinear multi-agent systems and their synchronization, further, attention was paid to some auxiliary results in the area of nonlinear observers. This Report briefly introduces the Project, provides a summary of the results obtained and also sketches an outline how these results will be applied and extended in future.
Klíčová slova:
multi-agent systems; nonlinear multi-agent systems; synchronization
Dokument je dostupný na externích webových stránkách.
GA 19-07635S: Outputs and Results
This manuscript aims to deliver a survey of results obtained during the solution of the project No. GA19-07635S of the Czech Science Foundation. The timespan dedicated to the work on this project was ...
Improving computational efficiency of contact solution in fully resolved CFD-DEM simulations with arbitrarily-shaped solids
Studeník, Ondřej; Kotouč Šourek, M.; Isoz, Martin
2023 - anglický
The abundance of industrial processes containing both solid and liquid phases generate demand for fully resolved models allowing for detailed analysis and optimization of these processes. An established approach providing such models is based using a variant of an immersed boundary method to couple the computational fluid dynamics (CFD) and discrete element method (DEM). In the talk, we will present our custom and monolithic implementation of a fully-resolved CFDDEM solver and concentrate on the intricacies of solving contact between two arbitrarily-shaped solids. We shall propose an efficient contact treatment based on the concept of a virtual mesh, which provides the mesh resolution required by DEM through dividing the space around the contact point in a finite volume fashion without any changes to the CFD mesh itself. A substantial part of the talk will devoted to the parallelization of the contact solution, especially in the context of the domain decomposition method imposed by the CFD solver.
Klíčová slova:
CFD; DEM; virtual mesh
Dokument je dostupný na externích webových stránkách.
Improving computational efficiency of contact solution in fully resolved CFD-DEM simulations with arbitrarily-shaped solids
The abundance of industrial processes containing both solid and liquid phases generate demand for fully resolved models allowing for detailed analysis and optimization of these processes. An ...
Ceramic protection of anti-corrosion layers of 3-glycidyloxypropyl-triethoxysilane on steel
Pokorný, P.; Prodanović, N.; Janata, Marek; Brožek, Vlastimil
2023 - anglický
There are various variations on the problem of steel reinforcement bond strength in concrete. Along with geometrical considerations, corrosion performance of steels with varying chemical compositions in interaction with variable chemical compositions of concrete are crucial. One approach is to cover steel surfaces with organosilane compounds, which increases the reinforcement resistance to corrosion in both acidic and alkaline conditions but, on the other hand, may weaken the reinforcement bond strength on concrete. The issue is resolved by intentionally forming a thin-walled, highly adhering corundum layer that is highly porous and impregnated with 3-glycidyloxypropyltriethoxysilane. This procedure also includes testing the adhesion properties between the ceramic and the metal and the cement prior to conducting a corrosion test in a chloride environment.
Klíčová slova:
steel; concrete; ceramics
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Ceramic protection of anti-corrosion layers of 3-glycidyloxypropyl-triethoxysilane on steel
There are various variations on the problem of steel reinforcement bond strength in concrete. Along with geometrical considerations, corrosion performance of steels with varying chemical compositions ...
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