National Repository of Grey Literature 62 records found  1 - 10nextend  jump to record: Search took 0.01 seconds. 
Contribution to modelling of bladed model disk with dry-friction contacts in tie-bosses
Pešek, Luděk ; Šnábl, Pavel ; Šulc, Petr ; Půst, Ladislav ; Bula, Vítězslav
The experimental set-up for studying dynamical behavior of the bladed wheel with pre-stressed dry-friction contacts in tie-bosses was built. The numerical solution of the turbine bladed wheel with tiebosses based on 3D finite element method with surface to surface dry friction contact model is proposed. Comparison of experimental and preliminary numerical results of dynamical behavior and damping estimation of our bladed wheel design yielded a reasonable agreement. Limitation of the non-linear solution due to dry friction contacts is HPC computations and long computation times. The contribution will deal with the achieved results.\n
The Effect of Blade Overlap on Aeroelastic Coupling
Procházka, Pavel P. ; Uruba, Václav ; Pešek, Luděk ; Bula, Vítězslav
This experimental study was established to clarify an aeroelastic coupling in the case of rotational periodic bodies. The blade grid was placed behind the outlet of the blow-down wind tunnel. Three of five blades were constructed to allow vertical position changing by the effect of three shakers. Particle Image Velocimetry was used to measure mean-phase velocity and dynamical parameters of the flow. The effect\nof blade enlargement will be introduced as well as the difference between forward and backward wave propagation.
Testing of HPD model of dissipated energy of hard rubbers at torsional finite Deformations and temperatures
Šulc, Petr ; Pešek, Luděk ; Bula, Vítězslav ; Šnábl, Pavel
This paper deals with the temperature dependence of hard rubber behavior on torsional harmonic loading. This behavior was described by dissipated and deformation energy of the rubber. This knowledge was used to test the validity of the hyperelastic proportional damping (HPD) in dependence on temperature and finite deformations. From the experiments, the dissipated energy was obtained from the hysteresis loop in one period of harmonic load, depending on the temperature for the given frequency. The deformation energy was determined from the shear stress analysis on the surface of the cylinder considering hyperelasticity. The constants of these models were obtained by optimizing the stress-strain curve from the shear analysis on the cylinder surface. With this optimization, the Yeoh hyperelastic model was chosen.
Vibrational tests and dynamic analysis of friction effect at railway wheel damped by damping ring
Pešek, Luděk ; Půst, Ladislav ; Bula, Vítězslav ; Šnábl, Pavel ; Boháč, T. ; Tašek, H. ; Běhálek, V.
Pro návrh tlumícího třecího kroužku s proměnnou křivostí s optimálním rozložením kontaktních tlaků v drážce, jež je cílem projektu DELTA, proběhla v dynamické laboratoři Bonatrans a.s. ve dnech 11. až 16. června 2019 experimentální modální analýza s jedním (SIMO) a dvěma (MIMO) budiči s těmito cíli: a) vytvořit metodiku zkoušky pro vyhodnocení třecího účinku tlumícího kroužku na tlumení vibrací kola; b) pomocí změn naměřených dynamických amplitudo-frekvenčních a fázově-frekvenčních charakteristik na amplitudu buzení popsat projevy nelineárního chování třecí vazby kruhového tlumícího kroužku v drážce kola pro různé vlastní tvary kmitání. Popis navržené metodiky a analýza naměřených výsledků z hlediska účinku třecích vazeb kruhového drátu jsou obsahem této zprávy. \n\n
Experimental and computer modelling study of glottal closing velocity during phonation
Horáček, Jaromír ; Radolf, Vojtěch ; Bula, Vítězslav ; Šidlof, P. ; Geneid, A. ; Laukkanen, A. M.
This preliminary study shows that the impact stress between the colliding vocal folds during phonation should not be evaluated from the maximum velocity of the glottal closing because the velocity of the closing diminishes just before the glottal closure. This phenomenon, which can be caused by a pressure cushion effect in the fast narrowing glottal gap, is demonstrated with measurements from high speed camera images recorded from human and on a physical laboratory model for vowel [u:] phonation and on a three-mass computer model employing a Hertz model of impact force. For a more detailed future study of this phenomenon a faster camera has to be used. \n
Experimental analysis of bladed wheel modelwith tie-boss couplings – steady and rotational states
Pešek, Luděk ; Bula, Vítězslav ; Šnábl, Pavel ; Cibulka, Jan
Experimental modal analysis of the proposed model of bladed wheel with tie-boss couplings was performed for validation of the numerical FE model. The pre-stresses in contacts were set and evaluated indirectly by the magnetic torque sensor. Then dynamical tests of bladed wheel under revolutions were performed. Theelectromagnetic synchronized pulses were used for excitation of forced vibration of the wheel. The Campbell diagram of the wheel with prestressed contacts was created from the measurement under revolutions. From the attenuation of resonant vibration of the wheel the dampingwas evaluated.
The Experimental Study of Aeroelastic Coupling of the Moveable Blade Grid with the Flow Field at Reynolds Number up to 150 000
Procházka, Pavel P. ; Uruba, Václav ; Pešek, Luděk ; Bula, Vítězslav
This experimental study was conducted to help clarify an aeroelastic coupling in the case of rotational periodic bodies. The blade grid was placed behind the outlet of the blow-down wind tunnel. Three of five blades were constructed to allow vertical position changing by the action of three shakers. Particle Image Velocimetry was used to study the flow field statistical and dynamical parameter. The parameters, whose presence indicates the aeroelastic coupling, are searched.
EXPERIMENTAL ANALYSIS OF BLADED WHEEL MODEL WITH TIE-BOSS COUPLINGS – STEADY AND ROTATIONAL STATES
Pešek, Luděk ; Bula, Vítězslav ; Šnábl, Pavel ; Cibulka, Jan
Experimental modal analysis of the proposed model of bladed wheel with tie-boss couplings was performed for validation of thenumerical FE model. The pre-stresses in contacts were set and evaluated indirectly by the magnetic torque sensor. Then dynamical tests of bladed wheel under revolutions were performed. The\nelectromagnetic synchronized pulses were used for excitation of forced vibration of the wheel. The Campbell diagram of the wheel with prestressedcontacts was created from the measurement under revolutions. From the attenuation of resonant vibration of the wheel the dampingwas evaluated.
The experimental study of aeroelastic coupling of the moveable blade grid with the flow field at Reynolds number up to 150 000
Procházka, Pavel ; Uruba, Václav ; Pešek, Luděk ; Bula, Vítězslav
This experimental study was conducted to help clarify an aeroelastic coupling in the case of rotational periodic bodies. The blade grid was placed behind the outlet of the blow-down wind tunnel. Three of five blades were constructed to allow vertical position changing by the action of three shakers. Particle Image Velocimetry was used to study the flow field statistical and dynamical parameter. The parameters, whose presence indicates the aeroelastic coupling, are searched.
Deformation energy of Yeoh hyperelastic model and constant hyperelastic proportional damping
Šulc, Petr ; Pešek, Luděk ; Bula, Vítězslav ; Košina, Jan ; Cibulka, Jan
The paper deals with a proposal of the dissipated energy of hard rubbers as a function of the deformation energy expressed by the Yeoh hyperelastic model. Then the deformation energy may be dependent only on the first invariant of deformation. Based on the experiment, a “hyperelastic proportional damping” (HPD) is proposed for hard rubbers under finite strains. It is analogical to the model of proportional damping in the elastic theory, i.e. the dissipated energy is proportional to the deformation energy multiplied by the frequency of dynamic harmonic loading. The Yeoh model is chosen since the deformation function is dependent only on the first strain invariant for a description of the simple shear of a surface cylinder. The constants are used to an enumeration of the deformation energy of the Yeoh model for the specific cases of tested rubbers. The coefficients of hyperelastic proportional damping are evaluated on the basis of experimental results,too.

National Repository of Grey Literature : 62 records found   1 - 10nextend  jump to record:
Interested in being notified about new results for this query?
Subscribe to the RSS feed.