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Stress and Deformation of the Filter Press
Fuis, Vladimír; Kašuba, D.
2020 - anglický
The paper presents the stress and deformation analyses of the new design of the filter press made by Envites spol. s r. o. The analyses are solved in system ANSYS and there are nonlinear - due to the modelling by the contact elements and due to the material nonlinearities.
Klíčová slova:
filter press; envites; finite element method; large deformation
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Stress and Deformation of the Filter Press
The paper presents the stress and deformation analyses of the new design of the filter press made by Envites spol. s r. o. The analyses are solved in system ANSYS and there are nonlinear - due to the ...
An experimental investigation of yield surfaces anisotropies
Štefan, Jan; Parma, Slavomír; Marek, René; Plešek, Jiří; Feigenbaum, H. P.; Ciocanel, C.
2020 - anglický
This contribution is dedicated to a rigorous experimental procedure for evaluation of yield surfaces of common metallic materials. This yield surface tracing procedure employs thin-walled tubular specimens to identify individual yield points of the material under arbitrary combinations of axial load and torque. A yield point is identified on the basis of a prescribed threshold for the effective plastic strain that is being continuously and fully automatically evaluated throughout the test. The experimental results generated with this tracing method are promising, leading to shapes of the yield surfaces conform with the von Mises criterion. The proposed methodology can effectively capture the YS shape.
Klíčová slova:
experimental mechanics; yield surface; directional distortional hardening; metallic materials
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
An experimental investigation of yield surfaces anisotropies
This contribution is dedicated to a rigorous experimental procedure for evaluation of yield surfaces of common metallic materials. This yield surface tracing procedure employs thin-walled tubular ...
Influencing the Indentation Curves by the Bluntness of the Berkovich Indenter at the Fem Modelling
Kovář, J.; Fuis, Vladimír; Tomaštík, Jan
2020 - anglický
The influence of the Berkovich indenter bluntness on the indentation curves at nanoindentation test of fused silica is determined by the FEM (finite element method) in this paper. The Berkovich indenter, which is mostly used for the nanoindentation test, was assumed for calculations. The indenter is always blunted in real tests. The bluntness of the indenter has an influence on the results of the nanoindentation test. The combination of the nanoindentation test and the FE modelling can be used for the calculation of the parameters of fused silica plasticity and estimation of the bluntness of the indenter. In this paper, the FEM was used for calculating of the indentation curves. Two cases of bluntness were assumed. The curves for ideally sharp or blunted indenter were determined. The results of these calculations showed that the indentation curves are dependent on the bluntness of the Berkovich indenter. The greatest relative influence of the nanoindentation curves by the bluntness is in the area of small values of the indenter displacement. The impact of assuming blunted indenter to calculated parameters of plasticity was assessed. It is often difficult to measure the bluntness of the indenter but it has an influence on the results of the nanoindentation test and should be included into calculations to make it more precise.
Klíčová slova:
Berkovich indenter; bluntness; finite element method; nanoindentation
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Influencing the Indentation Curves by the Bluntness of the Berkovich Indenter at the Fem Modelling
The influence of the Berkovich indenter bluntness on the indentation curves at nanoindentation test of fused silica is determined by the FEM (finite element method) in this paper. The Berkovich ...
Influence of contact region size between damping wire andand metal ring on overall damping
Šnábl, Pavel; Pešek, Luděk; Bula, Vítězslav; Cibulka, Jan
2020 - anglický
Damping wire curved to circular shape is inserted into a groove of slightly smaller diameter in damped steel ring. Deformation of circular-shaped wire causes uneven distribution of pressure in the groove and evenno contact between the wire and the groove in some regions. Experimentaimed for nding those regions was performed and the results are shown.Axial pre-stress of the wire was then applied and it was proven that it helps to reduce the regions with no contact. Dynamic test were made to see how larger contact region achieved by axial pre-stress inuences overall damping of damped steel ring.
Klíčová slova:
damping wire; vibration reduction; dynamic test
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Influence of contact region size between damping wire andand metal ring on overall damping
Damping wire curved to circular shape is inserted into a groove of slightly smaller diameter in damped steel ring. Deformation of circular-shaped wire causes uneven distribution of pressure in the ...
There are linear dynamical systems with Multiple Eigenvectors?
Kozánek, Jan; Zapoměl, Jaroslav
2020 - anglický
The steady-state response of non-damped linear and discrete dynamical systems on harmonic excitation can be expressed as the linear combination of independent eigenvectors. For special damped dynamical systems, there are some case, where the same eigenvector corresponds to the different eigenvalues.
Klíčová slova:
non-damped and damped dynamical systems; classical eigenvalue problem; non-linear eigenvalue problem; eigenvectors
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
There are linear dynamical systems with Multiple Eigenvectors?
The steady-state response of non-damped linear and discrete dynamical systems on harmonic excitation can be expressed as the linear combination of independent eigenvectors. For special damped ...
Dynamic and heat transfer analysis of a container with measuring instruments for space probes
Zolotarev, Igor; Bula, Vítězslav; Šnábl, Pavel; Gabriel, Dušan; Dobiáš, Jiří; Masák, Jan; Snížek, Jan; Souček, Jan
2020 - anglický
Rocket boosters and spacecraft are subject to intense acoustic environments during launch, which induce high levels of vibration in structural elements and equipment. In addition, elastic structural interactions with propulsion systems and flight control systems can produce low-frequency, high-deflection flight instabilities. Natural vibration of the container with measuring equipment were studied by numerical and experimental methods in the laboratory of Institute termomechanics CAS. Heat transfer analysis inside the container was made by FEM with respect to the conditions during start of the rocket and work in space.\n
Klíčová slova:
vibrations; modal analysis; natural frequencies; FEM thermal analysis; finite element model; radiative heat transfer
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Dynamic and heat transfer analysis of a container with measuring instruments for space probes
Rocket boosters and spacecraft are subject to intense acoustic environments during launch, which induce high levels of vibration in structural elements and equipment. In addition, elastic structural ...
The Effect of Angle of Attack on a Blade Cascade with Overlap
Procházka, Pavel P.; Uruba, Václav; Pešek, Luděk
2020 - anglický
This experimental study was carried out to study an aeroelastic coupling in the case of a blade cascade with overlap exposed to tunnel freestream of different angle of attack (AoA). Three of five blades were constructed to allow vertical position changing by the effect of three shakers. Particle Image Velocimetry was used to measure averaged velocity and dynamical parameters of the flow. Mainly, the effect of AoA will be discussed as well as the influence of blade enlargement and Re number. The influence of potential endplates will be indicated.
Klíčová slova:
blade cascade; time-resolved PIV; FFT; leakage
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
The Effect of Angle of Attack on a Blade Cascade with Overlap
This experimental study was carried out to study an aeroelastic coupling in the case of a blade cascade with overlap exposed to tunnel freestream of different angle of attack (AoA). Three of five ...
Creep behaviour of 316L stainless steel prepared by 3D printing
Dymáček, Petr; Kloc, Luboš; Gabriel, Dušan; Masák, Jan; Pagáč, M.; Halama, R.
2020 - anglický
The 3D printed 316L stainless steel produced by selective laser melting (SLM) was subjected to short term creep testing at 700 °C. Two directions of printing: i) horizontal and ii) vertical, were selected to test the creep performance of the steel. Comparison with the open literature data shows very good short-term creep properties of 3D printed steel that are superior to conventional steel. Both studied directions of printing show similar results so the steel can be considered from creep point of view as isotropic. The solution annealing prior to the creep testing slightly, but not substantially, lowers the creep performance of the steel.
Klíčová slova:
3D print; selective laser melting; 316L Stainless steel; creep
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Creep behaviour of 316L stainless steel prepared by 3D printing
The 3D printed 316L stainless steel produced by selective laser melting (SLM) was subjected to short term creep testing at 700 °C. Two directions of printing: i) horizontal and ii) vertical, were ...
A hybrid boundary element based aeroelastic model for flexible wing.
Prasad, Chandra Shekhar; Pešek, Luděk
2020 - anglický
The paper describes development of medium delity aeroelastic numerical model for fast aeroelastic analysis of the flexible aeronautical structures e.g. wings, rotor blades etc. The numerical model is developed particularly for the incompressible low subsonic flow regime application. For the flow field modeling boundary element based hybrid panel method flow solver with viscous-inviscid coupling strategy have been successfully developed and implemented here.The unsteady flow field is modeled using hybrid/modi ed panel method where, integral boundary layer theory (vis-cous part), surface panel method (potential flow inviscid part) and vortex particle method (separated shear layer modeling) are coupled together. The proposed model can simulate both attached and separated flow fields. The estimated aerodynamic lift coefficients and the pressure coefficient are compared with experimental results for static and dynamic stall flow conditions. Furthermore, the results from new aeroelastic model will be compared with classical CFD-CSD based aeroelastic models for efficiency and accuracy check. The proposed methodology for the aeroelastic analysis of long exible aeronautical structure will provide researchers and engineers a fast, cost effective and efficient tool for aeroelastic analysis for different design at preliminary design stage where large numbers of design iteration are required within short time frame.
Klíčová slova:
aeroelsticity; panel method; vortex particle method; boundary layer method; reduce order model; flutter
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
A hybrid boundary element based aeroelastic model for flexible wing.
The paper describes development of medium delity aeroelastic numerical model for fast aeroelastic analysis of the flexible aeronautical structures e.g. wings, rotor blades etc. The numerical model is ...
Aeroacoustic simulation of human phonation with the wale sub-grid scale model
Šidlof, Petr; Lasota, M.
2020 - anglický
The paper reports on an aeroacoustic model of voice generation in human larynx, based on Large Eddy Simulation with the Wall-Adapting Local Eddy-Viscosity (WALE) sub-grid scale (SGS) model. The simulation uses a three-step hybrid approach, with an incompressible finite volume CFD computation providing the filtered velocity and pressure, evaluation of the aeroacoustic sources, and simulation of the sound propagation by finite element discretization of the Acoustic Perturbation Equations. The WALE SGS model is used to overcome the limitation of the classical Smagorinski SGS model, which overpredicts the SGS viscosity in regions of high shear, especially within the boundary layer in the glottal constriction. Results of the 3D CFD simulation, location of the aeroacoustic sources and the spectra of the radiated sound for two vowels are presented.
Klíčová slova:
large eddy simulation; turbulence modelling; voice generation; aeroacoustics
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Aeroacoustic simulation of human phonation with the wale sub-grid scale model
The paper reports on an aeroacoustic model of voice generation in human larynx, based on Large Eddy Simulation with the Wall-Adapting Local Eddy-Viscosity (WALE) sub-grid scale (SGS) model. The ...
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