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Reduced modelling of aeroelastic instability in a turbine blade cascade
Pešek, Luděk; Šnábl, Pavel; Prasad, Chandra Shekhar
2023 - anglický
The contribution deals with the first results on flutter instability of the linear cascade triggered by impulse excitation. Together with experimental results, numerical results obtained by reduced modelling of the cascade using van der Pol model of self-excitation are presented and discussed.
Klíčová slova:
flutter; blade cascade; self-excitation; Van der Pol
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Reduced modelling of aeroelastic instability in a turbine blade cascade
The contribution deals with the first results on flutter instability of the linear cascade triggered by impulse excitation. Together with experimental results, numerical results obtained by reduced ...
Implementation of a plasticity model with advanced kinematic hardening rule for additively manufactured materials
Marek, René; Parma, Slavomír; Gabriel, Dušan; Džugan, J.
2023 - anglický
This technical report summarizes particularly the modeling part of the project DP 04_01_NPO “Emission-free technologies for local energy sources replacement” including development of models to describe multi-material 3D printed structures. The work is done in cooperation between COMTES FHT, a.s., the Institute of Thermomechanics of the Czech Academy of Sciences, v.v.i. and PROINNO, a.s. The goal of the project is the development of material models describing the behavior of multi-material components deposited by the direct deposition method (DED) under multiaxial cyclic loading.\nIn the report, a plasticity model suitable for materials prepared by the additive manufacturing method is compiled and used. The model uses Hill's plasticity condition, an advanced multi-component kinematic hardening rule, and an isotropic hardening rule. The associated flow rule is chosen and the implementation assumes the theory of small deformations. All constitutive relationships are presented and discussed for the selected model, and the model is thus fully and unambiguously formulated. The model is analytically integrated for a special case of loading and a special choice of parameters of the plasticity condition, namely transverse isotropy. A discretization scheme for numerical integration and procedures for FE implementation of the model are presented. For the FE implementation, a formulation in the displacement field is assumed, specifically the FE solver Abaqus and the implementation of the model using the UMAT interface are targeted. Several examples of the model's response to monotonic, uniaxial and biaxial cyclic loading trajectories are presented. \n Tato zpráva shrnuje postup prací na dílčím projektu DP 04_01_NPO “Emission-free technologies for local energy sources replacement” zahrnující vývoj modelů pro popis chování multi-materiálových 3D tištěných struktur řešený v konsorciu COMTES FHT, a.s., Ústav termomechaniky AV ČR, v.v.i. a PROINNO, a.s. Cílem projektu je vývoj materiálových modelů popisujících chování multi-materiálových komponent deponovaných metodou přímé depozice (DED) pří víceosém cyklickém zatěžování. \nVe zprávě je sestaven a použit model plasticity vhodný pro materiály připravené metodou aditivní výroby. Model využívá Hillovu podmínku plasticity, pokročilý vícesložkový model kinematického zpevnění a model isotropního zpevnění. Je zvolen asociovaný zákon tečení a implementace předpokládá teorii malých deformací. Pro zvolený model jsou uvedeny a diskutovány všechny konstitutivní vztahy a model je tak plně a jednoznačně formulován. Model je analyticky integrován pro speciální případ zatěžování a speciální volbu parametrů podmínky plasticity, konkrétně příčnou isotropii. Je prezentováno diskretizační schema pro numerickou integraci a procedury pro MKP implementaci modelu. U MKP implementace se předpokládá formulace v poli posunutí, konkrétně je pak cíleno na MKP řešič Abaqus a implementaci modelu pomocí rozhraní UMAT. Je prezentováno několik příkladů odezvy modelu na monotónní, jednoosé a víceosé cycklické zatěžovací trajektorie.\n
Klíčová slova:
plasticity; anisotropy; additive manufacturing
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Implementation of a plasticity model with advanced kinematic hardening rule for additively manufactured materials
This technical report summarizes particularly the modeling part of the project DP 04_01_NPO “Emission-free technologies for local energy sources replacement” including development of models to ...
Annular Impinging Jets and an Active Control of Hysteretic Effects
Devani, Yogendrasasidhar; Antošová, Zuzana; Trávníček, Zdeněk
2023 - anglický
An annular impinging air jet with and without flow control was studied experimentally using measurements of the wall pressure and flow velocity by the Pitot probe. To investigate flow control swirling effects, eight synthetic jets were generated from the nozzle center body. The experiments cover Reynolds numbers 4000–10,000 (evaluated from the outer exit diameter of the annular nozzle). For Re<9000, the bistability and hysteresis were identified and two different flow field patterns (A, B) were found under the same boundary conditions. For higher Re>9000, the hysteresis were not found.
Klíčová slova:
annular jet; impinging jet; hysteresis
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Annular Impinging Jets and an Active Control of Hysteretic Effects
An annular impinging air jet with and without flow control was studied experimentally using measurements of the wall pressure and flow velocity by the Pitot probe. To investigate flow control swirling ...
Stereolithography for manufacturing of advanced porous solids
Drechslerová, V.; Neuhäuserová, M.; Falta, J.; Šleichrt, J.; Kytýř, Daniel
2023 - anglický
The aim of this paper is focused on benefits of stereolithography (SLA) technology for the fabrication of the lightweight lattice structures with potential for load-bearing function and high absorption of impact energy. SLA is an additive manufacturing technology employing the principle of liquid resins curing moderated by radiation of a wavelength from ultra-violet band where resulting material parameters are tunable by setting of the curing process. The batches of samples manufactured using three different resins were subjected to quasi-static uni-axial tensile and compression tests. Acquired data were processed to derive deformation behaviour expressed as stress-strain diagrams and fundamental material properties. Based on the knowledge obtained from the mechanical tests, the setup of the fabrication parameters, the most suitable resin for manufacturing of the lattice structures and the overall suitability of SLA technology for the fabrication of advanced porous materials, were determined.
Klíčová slova:
stereolithography; advanced porous materials; quasi-static testing; resin; mechanical characteristics
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Stereolithography for manufacturing of advanced porous solids
The aim of this paper is focused on benefits of stereolithography (SLA) technology for the fabrication of the lightweight lattice structures with potential for load-bearing function and high ...
Caves in Bohemia et Moravia Subterranea by Mauritius Vogt (1669–1730)
Rychnová, L.; Vokurka, Michal
2023 - anglický
The Manuscript Bohemia et Moravia Subterranea (1729) by Mauritius Vogt reflects the subterranean landscapes and underground spaces based on Athanasius Kircher’s theories. The paper analyses the application of Kirchers’s terminology to the natural phenomena from Bohemia and Moravia. Further, we focused on how Vogt worked with his sources – how far he relied on literature, correspondence, or personal experience.
Klíčová slova:
Mauritius Vogt; caves; subterranean; underground; early modern period
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Caves in Bohemia et Moravia Subterranea by Mauritius Vogt (1669–1730)
The Manuscript Bohemia et Moravia Subterranea (1729) by Mauritius Vogt reflects the subterranean landscapes and underground spaces based on Athanasius Kircher’s theories. The paper analyses the ...
Statistical Approach for BTT probes distribution
Mekhalfia, Mohammed Lamine; Procházka, Pavel; Šmíd, R.; Tchawou Tchuisseu, Eder Batista
2023 - anglický
Blade tip timing (BTT) system is a non-invasive method used for measuring the blade tip timing of rotating machinery. The BTT system typically consists of sensor probes, signal conditioning system, and data acquisition unit. The sensor probes are placed in proximity to the rotating blade tips, Sensors measure the time at which each blade passes by the probe. By measuring the blade tip timing, the BTT system can detect changes in the blade tip vibration, which is an important for the health monitoring and performance optimization of rotating machinery [1]. To ensure accurate measurement of blade tip timing, the probe arrangement is crucial. The placement of the probe relative to the blade tips can affect the measurement accuracy, and thus, several arrangement algorithms have been developed to optimize the placement of the probes. Instead of considering the condition number, a statistical algorithms is followed to optimize the placement of probes for accurate measurement of blade tip timing in turbo-machinery. The statistical approach will be employed to determine the optimal locations for probes, with the aim of reducing errors in the measurement of blade tip timing. \n
Klíčová slova:
blade tip timing principle; RMSE; blade´s dynamics
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Statistical Approach for BTT probes distribution
Blade tip timing (BTT) system is a non-invasive method used for measuring the blade tip timing of rotating machinery. The BTT system typically consists of sensor probes, signal conditioning system, ...
The design of Bayesian diagnostic expert system Querix and it’s engineering application
Věchet, Stanislav; Krejsa, Jiří; Chen, K.-S.
2023 - anglický
Expert systems have gained attention over the last two decades as they bring the possibility of using expert knowledge in various control systems. However, it has lost attraction in favor of artificial neural networks in recent years, which is mostly influenced by the availability of data to train neural network models and the availability of various frameworks to achieve fast time-to-market applications for given solutions.
Klíčová slova:
expert system; decision making; advanced diagnostic; autonomous navigation; RPA
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
The design of Bayesian diagnostic expert system Querix and it’s engineering application
Expert systems have gained attention over the last two decades as they bring the possibility of using expert knowledge in various control systems. However, it has lost attraction in favor of ...
Optimization of the outflow regime in Římov reservoir from the point of view of water supply
Mercado, Ma. Cristina Paule; Hejzlar, Josef; Jarošík, Jiří; Porcal, Petr
2023 - anglický
The best management strategy for the Římov reservoir: (a) discharge from a depth of 3–5 m during the stratified season, (b) without support for SHP and with high reservoir filling, (c) reducing the phosphorus loading of the reservoir as much as possible. The impacts of climate change on water quality are significant, as inflow DOC and P concentrations here increase with temperature and flow variability. The effects of climate change can be mitigated by targeted management of the reservoir, but the quality of water inflow will still deteriorate further.
Klíčová slova:
water; dissolved organic matter; reservoir
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Optimization of the outflow regime in Římov reservoir from the point of view of water supply
The best management strategy for the Římov reservoir: (a) discharge from a depth of 3–5 m during the stratified season, (b) without support for SHP and with high reservoir filling, (c) reducing the ...
Effect of spin coating on electrical properties of MXene films deposited from non-aqueous solvents
Gutsul, O.; Szabó, Ondrej; Pfeifer, R.; Sasitharan, K.; Jackivová, Rajisa; Slobodyan, V.; Kromka, Alexander; Rezek, B.
2023 - anglický
We investigated the effect of spin coating parameters on the electrical properties of Ti3C2 MXene thin films deposited from non-aqueous suspensions in N,N-dimethyl formamide (DMF) and N-methyl-2-pyrrolidone (NMP) on gold interdigitated electrodes (IDE). The electrical properties of DMF-MXenes and NMP-MXenes films are characterized by impedance spectroscopy (4 Hz - 8 MHz at 1 V) using gold IDE with 25 µm gap. The electrical conductivity of MXene films decreases with increasing spin coating speed from 300 to 900 rpm. The series resistance (Rs) and double layer capacitance remain similar (Cdl). In all cases, MXenes deposited from DMF have five orders of magnitude higher electrical conductivity (lower Rct) than MXene films deposited from NMP. It is correlated with the thin film morphology obtained by scanning electron microscopy (SEM). These findings can be useful for possible application of MXenes as charge transport layers in hybrid photovoltaic devices.
Klíčová slova:
MXene; thin films; impedance spectroscopy; electrical conductivity; spin coating
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Effect of spin coating on electrical properties of MXene films deposited from non-aqueous solvents
We investigated the effect of spin coating parameters on the electrical properties of Ti3C2 MXene thin films deposited from non-aqueous suspensions in N,N-dimethyl formamide (DMF) and ...
Novel embedding resins for 3D-SEM II
Šlouf, Miroslav; Pavlova, Ewa; Strachota, Beata; Strachota, Adam; Nebesářová, Jana; Týč, Jiří; Krzyžánek, Vladislav; Skoupý, Radim
2023 - anglický
Research report for Thermo Fisher Scientific s. r. o., based on common project awarded by TA CR (program: National center of competence, TN01000008).
Klíčová slova:
novel embedding resins; 3D-SEM microscopy; higher e-beam resistance
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Novel embedding resins for 3D-SEM II
Research report for Thermo Fisher Scientific s. r. o., based on common project awarded by TA CR (program: National center of competence, TN01000008).
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