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 - English 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. Keywords: SHPB; basalt; compressive loading; dynamic loading Available at various institutes of the ASCR 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 - English 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. Keywords: finite element method; direct time integration; asynchronous integration; domain decomposition; localized lagrange multipliers Available at various institutes of the ASCR 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

Comparison of finite element simulation of tungsten nanoindentation with Berkovich and conical indenter
Fiala, L.; Ballo, I.; Kovář, J.; Fuis, Vladimír
2023 - English 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. Keywords: nanoindentation; FEM; Berkovich indenter; conical indenter; tungsten Available at various institutes of the ASCR 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

Optical and Pneumatic Measurements on TR-U-11 Cascade
Luxa, Martin; Hála, Jindřich; Šimurda, David
2023 - English 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. Keywords: transonic flow; rotor turbine blade; tip section Available at various institutes of the ASCR 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

Ambiguity in Stochastic Optimization Problems with Nonlinear Dependence on a Probability Measure via Wasserstein Metric
Kaňková, Vlasta
2023 - English Many economic and financial applications lead to deterministic optimization problems depending on a probability measure. It happens very often (in applications) that these problems have to be solved on the data base. Point estimates of an optimal value and estimates of an optimal solutionset can be obtained by this approach. A consistency, a rate of convergence and normal properties, of these estimates, have been discussed (many times) not only under assumptions of independent data corresponding to the distributions with light tails, but also for weak dependent data and the distributions with heavy tails. However, it is also possible to estimate (on the data base) a confidence intervals and bounds for the optimal value and the optimal solutions. To analyze this approach we focus on a special case of static problems depending nonlineary on the probability measure. Stability results based on the Wasserstein metric and the Valander approach will be employed for the above mentioned analysis. Keywords: Stochastic optimization problems; static problems; empirical measure; point estimates; interval estimates; nonlinear dependence Fulltext is available at external website. Ambiguity in Stochastic Optimization Problems with Nonlinear Dependence on a Probability Measure via Wasserstein Metric

Many economic and financial applications lead to deterministic optimization problems depending on a probability measure. It happens very often (in applications) that these problems have to be solved ...

Kaňková, Vlasta
Ústav teorie informace a automatizace, 2023

Improving computational efficiency of contact solution in fully resolved CFD-DEM simulations with arbitrarily-shaped solids
Studeník, Ondřej; Kotouč Šourek, M.; Isoz, Martin
2023 - English 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. Keywords: CFD; DEM; virtual mesh Fulltext is available at external website. 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 ...

Studeník, Ondřej; Kotouč Šourek, M.; Isoz, Martin
Ústav termomechaniky, 2023

A new blade cascade for flutter studies
Šnábl, Pavel; Pešek, Luděk; Procházka, Pavel P.; Skála, V.
2023 - English 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. Keywords: blade cascade; stability; travelling wave mode; aerodynamic influence coefficient Available at various institutes of the ASCR 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 ...

Šnábl, Pavel; Pešek, Luděk; Procházka, Pavel P.; Skála, V.
Ústav termomechaniky, 2023

Kráľova Lehota. Paleomagnetic research. Report
Elbra, Tiiu; Schnabl, Petr; Aidona, E.; Kdýr, Šimon; Uçar, Hakan; Pruner, Petr; Benediková, L.
2023 - English Keywords: Archeological artefact; paleomagnetic dating; rock magnetism Available at various institutes of the ASCR Kráľova Lehota. Paleomagnetic research. Report

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

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 - English 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. Keywords: integrity of reactor pressure vessel; severe accident; ASTEC; creep; FEM Fulltext is available at external website. 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 ...

Gabriel, Dušan; Gál, P.; Kotouč, M.; Dymáček, Petr; Masák, Jan; Kopačka, Ján
Ústav termomechaniky, 2023

Reduced modelling of aeroelastic instability in a turbine blade cascade
Pešek, Luděk; Šnábl, Pavel; Prasad, Chandra Shekhar
2023 - English 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. Keywords: flutter; blade cascade; self-excitation; Van der Pol Available at various institutes of the ASCR 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