Comparison of finite element simulation of tungsten nanoindentation with Berkovich and conical indenter
Fiala, L.; Ballo, I.; Kovář, J.; Fuis, Vladimír
2023 - anglický Finite Element Method (FEM) was used to study the difference between using Berkovich and conical indenters in nanoindentation test of tungsten specimen. The study was aimed to determine the\nmodulus of elasticity of a tested specimen and how it changes with different indenter. The FEM analysis also revealed that the modulus of elasticity was sensitive to the dimensions of both specimen and the indenter for which were made several numerical calculations with different dimensions. Klíčová slova: nanoindentation; FEM; Berkovich indenter; conical indenter; tungsten Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR. Comparison of finite element simulation of tungsten nanoindentation with Berkovich and conical indenter

Finite Element Method (FEM) was used to study the difference between using Berkovich and conical indenters in nanoindentation test of tungsten specimen. The study was aimed to determine the\nmodulus ...

Fiala, L.; Ballo, I.; Kovář, J.; Fuis, Vladimír
Ústav termomechaniky, 2023

Mechanical properties of basalt: a study on compressive loading at different strain rates using SHPB
Falta, J.; Krčmářová, N.; Fíla, T.; Vavro, Martin; Vavro, Leona
2023 - anglický This article focuses on the mechanical properties of basalt in compressive loading at different strain-rates. The study employs advanced instrumentation for the evaluation of the results in dynamic conditions, while standard uni-axial loading device is used for evaluation in quasi-static conditions. Basalt specimens were subjected to four different loading-rates from 200–600 s−1 on which the stress-strain dependence was evaluated together with DIC analysis of crack initiation and disintegration process. Understanding the mechanical properties of basalt can provide insights for engineers and designers in creating structures that are durable and able to withstand different loading conditions. The findings of this study can have implications for a wide range of industries, including aerospace, automotive, and construction, among others. Klíčová slova: SHPB; basalt; compressive loading; dynamic loading Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR. Mechanical properties of basalt: a study on compressive loading at different strain rates using SHPB

This article focuses on the mechanical properties of basalt in compressive loading at different strain-rates. The study employs advanced instrumentation for the evaluation of the results in dynamic ...

Falta, J.; Krčmářová, N.; Fíla, T.; Vavro, Martin; Vavro, Leona
Ústav geoniky, 2023

Asynchronous time integration while achieving zero interface energy
Dvořák, Radim; Kolman, Radek; Falta, J.; Neühauserová, M.
2023 - anglický This contribution deals with an asynchronous direct time integration of the finite-element model. The proposed method is applied to the phenomenon of wave propagation through an elastic linear continuum. The numerical model is partitioned into individual subdomains using the domain decomposition method by means of localized Lagrange multipliers. For each subdomain, different time discretizations are used. No restrictions for relation between subdomain’s time steps are imposed. The coupling of the subdomains is forced by an acceleration continuity condition. Additionally, we use the a posteriori technique to also provide the displacement and velocity continuity at the interfaces, and hence we obtain exact continuity of all three kinematic fields. The proposed method is experimentally validated using the modified SHPB (split Hopkinson pressure bar) setup. Klíčová slova: finite element method; direct time integration; asynchronous integration; domain decomposition; localized lagrange multipliers Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR. Asynchronous time integration while achieving zero interface energy

This contribution deals with an asynchronous direct time integration of the finite-element model. The proposed method is applied to the phenomenon of wave propagation through an elastic linear ...

Dvořák, Radim; Kolman, Radek; Falta, J.; Neühauserová, M.
Ústav termomechaniky, 2023

Optical and Pneumatic Measurements on TR-U-11 Cascade
Luxa, Martin; Hála, Jindřich; Šimurda, David
2023 - anglický The report contains results and evaluation of conducted optical (interferometry and schlieren technique) and pneumatic measurements on the first variant of the new tip section, intended for turbine rotor blade. Klíčová slova: transonic flow; rotor turbine blade; tip section Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR. Optical and Pneumatic Measurements on TR-U-11 Cascade

The report contains results and evaluation of conducted optical (interferometry and schlieren technique) and pneumatic measurements on the first variant of the new tip section, intended for turbine ...

Luxa, Martin; Hála, Jindřich; Šimurda, David
Ústav termomechaniky, 2023

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 ...

Věchet, Stanislav; Krejsa, Jiří; Chen, K.-S.
Ústav termomechaniky, 2023

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 ...

Mercado, Ma. Cristina Paule; Hejzlar, Josef; Jarošík, Jiří; Porcal, Petr
Biologické centrum, 2023

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, ...

Mekhalfia, Mohammed Lamine; Procházka, Pavel; Šmíd, R.; Tchawou Tchuisseu, Eder Batista
Ústav termomechaniky, 2023

Kráľova Lehota. Paleomagnetic research. Report
Elbra, Tiiu; Schnabl, Petr; Aidona, E.; Kdýr, Šimon; Uçar, Hakan; Pruner, Petr; Benediková, L.
2023 - anglický Klíčová slova: Archeological artefact; paleomagnetic dating; rock magnetism Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR. Kráľova Lehota. Paleomagnetic research. Report

Elbra, Tiiu; Schnabl, Petr; Aidona, E.; Kdýr, Šimon; Uçar, Hakan; Pruner, Petr; Benediková, L.
Geologický ústav, 2023

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 ...

Pešek, Luděk; Šnábl, Pavel; Prasad, Chandra Shekhar
Ústav termomechaniky, 2023

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 ...

Marek, René; Parma, Slavomír; Gabriel, Dušan; Džugan, J.
Ústav termomechaniky, 2023