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Modelling approaches to the stress wave propagation in a cracked specimen
Kruisová, Alena; Kopačka, Ján; Kober, Jan
2021 - anglický
One of the essential tasks of non-destructive testing is to detect a crack in a specimen. It is well known that a component with a crack exposed to a harmonic excitation of a given frequency\nhas a nonlinear response as a function of the excitation amplitude. The focus of this paper is the numerical modelling of this phenomenon using the finite element method with the consideration\nof the contact constraint at the crack interface. In addition to the nonlinear transient dynamic problem solved by explicit time integration, a more efficient procedure based on the harmonic\nbalance method is developed. The results of numerical simulations are also compared with experimentally obtained data.
Klíčová slova:
finite element method; contact; crack; harmonic balance method
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Modelling approaches to the stress wave propagation in a cracked specimen
One of the essential tasks of non-destructive testing is to detect a crack in a specimen. It is well known that a component with a crack exposed to a harmonic excitation of a given frequency\nhas a ...
Development of autonomous experimental setup to investigate directional distortional hardening under biaxial loading
Svárovský, Jiří; Parma, Slavomír; Štefan, Jan; Ciocanel, C.; Feigenbaum, H. P.; Klepač, Vilém; Marek, René; Plešek, Jiří
2021 - anglický
Plastic deformations alter the shape of the yield surface in the stress space. Models for predicting the shape of the yield surface according to the direction of loading are being developed. Experimental data are the key factor in development and validation of phenomenological models, such as the model of directional distortional hardening cited in this study. The objective of this paper is to present the experimental setup for investigation of the directional distortional hardening. A new autonomous method was developed using an axial-torsional testing machine and the Labivew 2017 graphical programming environment to monitor the yield surface in axial stress – shear stress space. A suitable yield condition in form of effective plastic strain was used for the determination of the yield points. Initial yield surface obtained by this method shows promising agreement with von Mises model of the yield surface. Several outstanding yield points were measured which disrupt the assumption of the yield surface convexity. Therefore, possible shortcomings caused by the methodology are being investigated.
Klíčová slova:
directional distortional hardening; yield surface; strain hardening; Labview
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Development of autonomous experimental setup to investigate directional distortional hardening under biaxial loading
Plastic deformations alter the shape of the yield surface in the stress space. Models for predicting the shape of the yield surface according to the direction of loading are being developed. ...
Recent improvements in CFD solver for fully coupled particle-laden flows
Šourek, M.; Isoz, Martin
2021 - anglický
While new methods combining the computational fluid dynamics (CFD) and the discrete element method (DEM) have been developed to simulate freely moving solid particles, they tend to be focused on simulations with spherical particles only. Here, we present a strongly coupled CFD-DEM solver capable of simulating movement of arbitrarily-shaped particles dispersed in a fluid. The particles are assumed to be large enough to affect the fluid flow and distributed densely enough to come into contact with both the boundaries of the computational domain and with each other. In this paper, we will focus on the recent improvements of our solver, specifically, in the areas of (i) inclusion of solid bodies into the computational domain, (ii) general CFD-DEM coupling algorithm, and (iii) code parallelization and practical usability.
Klíčová slova:
CFD; DEM; HFDIB-DEM; OpenFOAM
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Recent improvements in CFD solver for fully coupled particle-laden flows
While new methods combining the computational fluid dynamics (CFD) and the discrete element method (DEM) have been developed to simulate freely moving solid particles, they tend to be focused on ...
Numerical estimation of blade displacement due to air excitation
Mekhalfia, Mohammed Lamine; Procházka, Pavel; Tchawou Tchuisseu, Eder Batista; Hodboď, Robert; Maturkanič, Dušan
2021 - anglický
For the last few years, vibration measurement has taken an intense interest from research activities. For this reason, this article considers, besides vibration measurements, the impact of air forced excitation on blade motion, displacement and vibration through both simulation analysis and The Transformation of mathematical analysis that explain the interaction between fluid (Air) and the structure (Blade) into numerical setup along with FEM analysis through ANSYS Software. 3D Blade was created to meet the same characteristics of the real blade to enable real environment criteria for the simulation.
Klíčová slova:
displacement; Fluid structure interaction (FSI); air; blade
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Numerical estimation of blade displacement due to air excitation
For the last few years, vibration measurement has taken an intense interest from research activities. For this reason, this article considers, besides vibration measurements, the impact of air forced ...
Study of aeroacoustics noise of high-speed aircraft propellers and mitigation of the cause
Prasad, Chandra Shekhar
2021 - anglický
The project deals with the study of aeroacoustics noise generated by high-speed turboprop propellers and methods to minimize its causes. A reduced order flow solver with aeroacaustic noise capturing characteristics is developed for fast numerical analysis purpose. The acoustical performance will be also studied using flow visualization using article image velocimetry under rotation and acoustics noise will be measured by microphones for both conventional as well as unconventional propeller designs at diferent rotational speeds.
Klíčová slova:
aeroacoustics; aircraft propellers; tip-vortex interaction; low noise propeller; ROM-CFD/CAA
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Study of aeroacoustics noise of high-speed aircraft propellers and mitigation of the cause
The project deals with the study of aeroacoustics noise generated by high-speed turboprop propellers and methods to minimize its causes. A reduced order flow solver with aeroacaustic noise capturing ...
Dynamics of Machines and Mechanical Systems with Interactions, DYMAMESI 2021
Zolotarev, Igor; Pešek, Luděk; Kozień, M. S.
2021 - 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 2021
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, ...
The new HPC results of 3D FE modelling of dry-friction damping at tie-boss couplings of bladed wheel - 6nd resonant mode
Pešek, Luděk; Šnábl, Pavel; Bula, Vítězslav
2021 - anglický
The paper is a direct continuation of our study published in the last colloquium DYMAMESI. This paper deals with the new results of dry-friction damping calculation of the bladed wheel with tie-boss couplings vibrating at a higher resonant mode, i.e. mode with 6 nodal diameters (ND). The numerical solution of the wheel based on 3D finite element method with surface-to-surface dry friction contact model is applied. Due to dry friction contacts and non-linear solution, it leads to HPC computations and long computation times. Therefore, the earlier proposed computational strategy for damping evaluation where the resonant attenuation is computed directly from the defined resonant initial conditions given by the 6ND mode is used. Comparison of experimental and numerical results of dynamical behaviour of the bladed wheel yields a reasonable agreement for the studied vibration mode.
Klíčová slova:
bladed wheel; dry-friction contacts; damping; tie-boss couplings
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
The new HPC results of 3D FE modelling of dry-friction damping at tie-boss couplings of bladed wheel - 6nd resonant mode
The paper is a direct continuation of our study published in the last colloquium DYMAMESI. This paper deals with the new results of dry-friction damping calculation of the bladed wheel with tie-boss ...
Verification of our deformation member for measuring axial force under torsional dynamic load
Šulc, Petr; Pešek, Luděk; Štěpánek, Ivo; Šnábl, Pavel; Bula, Vítězslav
2021 - anglický
This paper deals with experimental testing of hard rubbers under torsional harmonic loading on an axial torsional servohydraulic testing machine Instron 8852. In evaluating these experiments, we focused on obtaining axial forces and elongation, which is a confirmation of the so-called Poynting effect under torsional loading. An important result from these experiments is a comparison of axial forces from this device with the results from our designed and assembled torsion device with a deformation member for measuring axial forces, which brings us some verification of this device.
Klíčová slova:
axial force; torsion dynamic load; hard rubber; Poynting effect
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Verification of our deformation member for measuring axial force under torsional dynamic load
This paper deals with experimental testing of hard rubbers under torsional harmonic loading on an axial torsional servohydraulic testing machine Instron 8852. In evaluating these experiments, we ...
Numerical simulation of dynamic loading of a test blade in forced torsional vibration
Šidlof, P.; Vomáčko, V.; Lepičovský, Jan; Šimurda, David; Štěpán, M.; Luxa, Martin
2021 - anglický
Within a new project focused on blade flutter research, building on previous experience with the NASA Transonic Flutter Cascade facility, static blade cascade and airfoil flutter experiments realized in cooperation between the Institute of Thermomechanics and Technical University of Liberec, a new test facility is under development for the investigation of high subsonic and transonic flow in a blade cascade under forced torsional oscillation. Apart from aerodynamic loading of the blades, the oscillating blade will be exposed to significant structural stresses due to the highfrequency torsional vibration. In order to avoid structural integrity issues from high-cycle fatigue, a numerical simulation of the stress and displacement of the blade was realized. Regions where equivalent stress reaches maximum values were identified, and elastic deformations were computed. The limits in oscillation amplitude and frequency for the safe operation of the experimental setup were discussed.
Klíčová slova:
blade flutter; structural analysis; torsional vibration
Plné texty jsou dostupné na jednotlivých ústavech Akademie věd ČR.
Numerical simulation of dynamic loading of a test blade in forced torsional vibration
Within a new project focused on blade flutter research, building on previous experience with the NASA Transonic Flutter Cascade facility, static blade cascade and airfoil flutter experiments realized ...
Comparison of Transonic Flows Through Two Tip-Section Turbine Blade Cascades with Different Flat Profiles
Musil, Josef; Příhoda, Jaromír; Fürst, J.; Luxa, Martin; Šimurda, David
2021 - anglický
The contribution deals with numerical simulations of 2D compressible flow through two variants of the tip-section turbine blade cascade with a flat profile for the subsonic inlet. Simulations were realised by means of the OpenFOAM code using the γ-Reθ bypass transition model completed by the two-equation SST turbulence model. Predictions were focused particularly on the impact of the shock-wave/boundary-layer interaction on the flow structure in the inter-blade channel. Beside the effect of the inlet angle on the flow around the leading edge was studied. Numerical results were compared with optical and pressure experimental data.
Klíčová slova:
supersonic tip-section blade cascade; CFD; transition modelling
Dokument je dostupný na externích webových stránkách.
Comparison of Transonic Flows Through Two Tip-Section Turbine Blade Cascades with Different Flat Profiles
The contribution deals with numerical simulations of 2D compressible flow through two variants of the tip-section turbine blade cascade with a flat profile for the subsonic inlet. Simulations were ...
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