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Dynamics of Machines and Mechanical Systems with Interactions, DYMAMESI 2023
Zolotarev, Igor; Pešek, Luděk; Kozień, M. S.
2023 - 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. The colloquium DYMAMESI 2021 is cofunded by the Strategy AV21 initiative of the Czech Academy of Sciences of the Czech Republic, and in 2021 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, DYMAMESI 2023
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, ...
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 ...
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 ...
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 ...
A new blade cascade for flutter studies
Šnábl, Pavel; Pešek, Luděk; Procházka, Pavel P.; Skála, V.
2023 - anglický
In this paper, a new blade cascade, developed in the Institute of Thermomechanics, is presented. The geometry of the cascade was modified so now the stall flutter can occur. It has some major construction improvements over the original cascade which now allow more precise and reliable measurements. The stability of the new blade cascade with five NACA 0010 profiles with rotational degree of freedom is assessed by Travelling Wave Mode approach and Aerodynamic Influence Coefficient approach.
Klíčová slova:
blade cascade; stability; travelling wave mode; aerodynamic influence coefficient
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
A new blade cascade for flutter studies
In this paper, a new blade cascade, developed in the Institute of Thermomechanics, is presented. The geometry of the cascade was modified so now the stall flutter can occur. It has some major ...
Thermal and creep analysis of VVER-1000 reactor pressure vessel at high temperatures caused by fuel melting during severe accident
Gabriel, Dušan; Gál, P.; Kotouč, M.; Dymáček, Petr; Masák, Jan; Kopačka, Ján
2023 - anglický
Thermal and creep analysis of the VVER-1000 reactor pressure vessel (RPV) was performed at high temperatures caused by fuel melting during severe accident. First, the integral code ASTEC was applied simulating severe accident evolution since an initiating event up to a hypothetical radioactive release into the environment. The ASTEC outputs including the remaining RPV wall thickness, the heat flux achieved and the temperature profile in the ablated vessel wall served as boundary conditions for the consequent assessment of RPV integrity carried out with the aid of finite element method (FEM). The FEM analysis was performed including the creep behaviour of RPV material using a complex creep probabilistic exponential model with damage. The objective of the analysis was to computationally assess emergency condition and, on this basis, to propose a general methodology for evaluating the integrity of RPV at high temperatures due to fuel melting during severe accident.
Klíčová slova:
integrity of reactor pressure vessel; severe accident; ASTEC; creep; FEM
Dokument je dostupný na externích webových stránkách.
Thermal and creep analysis of VVER-1000 reactor pressure vessel at high temperatures caused by fuel melting during severe accident
Thermal and creep analysis of the VVER-1000 reactor pressure vessel (RPV) was performed at high temperatures caused by fuel melting during severe accident. First, the integral code ASTEC was applied ...
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 ...
Simulation of heterogeneously-catalyzed non-isothermal reactive flow in industrial packed beds
Hlavatý, Tomáš; Isoz, Martin; Khýr, M.
2023 - anglický
Packed bed reactors are the most frequently used devices to perform heterogeneously catalyzed reactions on industrial scales. An industrial real-life heterogeneous catalysis is complex process that combines fully three-dimensional mass, momentum and energy transport on several scales. In the present work, we leverage our previously developed CFD solver for non-isothermal heterogeneously catalyzed reactive flow based on the finite volume method and couple it with our\nin-house DEM-based method for preparation of random packed beds. The resulting framework is verified in the simplified cases against available analytical solutions and correlations and is used to study an industrially-relevant case of ethylene oxychlorination performed in a tubular packed bed comprising CuCl2-coated catalyst carrying particles. In particular, we compare properties of three different industrially used catalyst carrying particles: Raschig rings, Reformax, and Wagon wheels
Klíčová slova:
CFD; OpenFOAM; non-isothermal flow
Plné texty jsou dostupné v digitálním repozitáři NUŠL
Simulation of heterogeneously-catalyzed non-isothermal reactive flow in industrial packed beds
Packed bed reactors are the most frequently used devices to perform heterogeneously catalyzed reactions on industrial scales. An industrial real-life heterogeneous catalysis is complex process that ...
Numerical implementation of incremental minimization principle for materials with multiple rate-independent dissipative mechanisms
Frost, Miroslav; Moskovka, Alexej; Sedlák, Petr; Valdman, Jan
2023 - anglický
The incremental energy minimization approach is a compact variational formulation of the evolutionary boundary value problem for constitutive models of materials with a rate-independent response. Although it can be easily applied to many conventional models, its main advantages arise when applied to models with multiple strongly coupled dissipation mechanisms, where the direct construction of the coupled yield conditions and flow rules may be challenging. However, this usually requires a more complex numerical treatment of the resulting sequence of time-incremental boundary value problems resolved via the finite element method. This contribution presents, compares and discusses two genuine minimization approaches - the staggered solution procedure relying on alternating minimization and the monolithic approach employing global minimization - for an advanced constitutive model of shape memory alloys.
Klíčová slova:
variational approach; constitutive modeling; numerical implementation
Dokument je dostupný na externích webových stránkách.
Numerical implementation of incremental minimization principle for materials with multiple rate-independent dissipative mechanisms
The incremental energy minimization approach is a compact variational formulation of the evolutionary boundary value problem for constitutive models of materials with a rate-independent response. ...
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 ...
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