Search

Start Over Creator Pešek, Luděk

2. Contribution to application of ‘parametric anti-resonance‘ for autoparametric systems

Creator:
Pešek, Luděk and Tondl, Aleš
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
autoparametric systems, parametric anti-resonance, and equilibrium stabilization
Language:
English
Description:
This paper deals with the phenomenon of the parametric anti-resonance of autoparametric systems. It is shown that parametric anti-resonance (additional parametric excitation fulfilling special conditions) can be used not only to suppress self-excited or externally excited vibrations but can also be used to stabilize the equilibrium position ot the autoparametric system. and Obsahuje seznam literatury
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

3. Development of vibrodiagnostic system of tram wheel for damage analysis

Creator:
Pešek, Luděk, Vaněk, František, Balda, Miroslav, Procházka, Pavel, Vaněk, Petr, Cibulka, Jan, and Bula, Vítězslav
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
vibration, deformation, damage, and railway wheels
Language:
English
Description:
The vibrodiagnostic system VDS-UT2 was developed for the investigation of a tram wheel operational vibration and deformation. The system consists of measuring, acquisition and processing tools for monitoring of tram wheels and their operational parameters, e.g. static and dynamic deformation, displacement, velocity, acceleration and temperature. The measuring on a rotating wheel is realized both by telemetric and by top-timing system. Measured data can be remote-observed via Internet connection with the control PC. The acquisition system by Starmans Electronics s.r.o. provides continuous analog and digital data logging. The control PC processes digital logical signals and evaluates time intervals representing circumferential turning angles between disk and rim.. In the contribution, the diagnostic system is described and the measured data including damage analysis are presented. and Obsahuje seznam literatury
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

4. Excitation of blade vibration under rotation by synchronous electromagnet

Creator:
Pešek, Luděk, Vaněk, František, Bula, Vítězslav, and Cibulka, Jan
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
blade, vibration, excitation, and electromagnet
Language:
English
Description:
This paper presents the procedure for designing electromagnetic bladed wheel excitation. This procedure comes from phase-synchronization of multiple electromagnets distributed around the wheel with a movement of the blade to obtain its resonant vibration. This procedure can be used with merit for dynamic tests of inter-blade couplings. The verification was performed on the tested wheel using two-point electromagnetic excitation of blades under rotation. and Obsahuje seznam literatury
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

5. New test approach and evaluation of dynamic and thermal parameters of elastomers

Creator:
Pešek, Luděk, Vaněk, František, Procházka, Pavel, Bula, Vítězslav, and Cibulka, Jan
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
rubber, dynamic, tests, identification, fatigue, and thermo-mechanics
Language:
English
Description:
The new test approach for evaluation of thermo-visco-elastic parameters of elastomers is designed, realized and discussed herein. The main attention is devoted to a kinematically excited rubber beam specimen under transient resonant sweep excitation. Mechanical material characteristics, i.e. Young modulus and loss angle, are identified from analytical formulas of frequency function based on measured dynamic loading and response signals. Heat material constants were estimated indirectly by numerical thermo-mechanical FE model and matching numerical and experimental results. The 'sweep' regime tests serve for estimation of thermal and mechanical dependences. Long-term fatigue tests with cyclic resonant loading enable analysis of material degradation, such as hardening and permanent deformations. and Obsahuje seznam literatury
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

6. Non-proportional nonlinear damping in experimental bladed disk

Creator:
Půst, Ladislav and Pešek, Luděk
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
bladed disk vibrations, dry friction damping, imperfection, non-proportionality, and response curves
Language:
English
Description:
Paper is concerned with the flexural vibrations of imperfect bladed circular disk by analytical and numerical solutions. Dsk imperfection results from additional two groups of damping heads fixed on opposite ends of one diameter, which introduces point imperfections in mass, stiffness and nonlinear damping and non-proportional distribution of damping properties. The aim of this study is to investigate influence of friction damping among added bladed heads on decrease of resonance amplitudes. Examples based on application of equivalent linearized damping show the properties of such dampers. and Obsahuje seznam literatury
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

7. Testing of dynamics of blade wheel with double periodicity

Creator:
Pešek, Luděk, Vaněk, František, Půst, Ladislav, Bula, Vítězslav, and Cibulka, Jan
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
dynamics, bladed wheel, rotation, and mistuning
Language:
English
Description:
The dynamics of the mistuned model of the tests bladed disc with double perodicity was experimentally investigated. The mistuning arised due to the implemantation of two bunches of blades with damping heads fixed on opposite ends of the diameter. The dry friction effect in the heads was treated. The scale for measurement of the electromagnetic force acting on the disc was designed. It enables to analyse the real electromagnetic excitation of the disc under rotation and evaluation of the FRF characteristics from measured blade responses under rotation. The identified eigenfrequencies and damping constan ts served as indicators for assessment of stiffening and damping effects of the friction couplings in the heads. and Obsahuje seznam literatury
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

8. Various types of dry friction characteristics for vibration damping

Creator:
Půst, Ladislav, Pešek, Luděk, and Radolfová, Alena
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
dry friction, stick-slip motion, modified Coulomb law, equivalent linearization, equivalent stiffness, and equivalent damping coefficient
Language:
English
Description:
Paper deals with derivation of mathematical relationships of dry friction force versus relative velocity in friction contact of two bodies. It is focused on such main types of dry friction characteristics, which frequently occur in dynamic mechanical systems. New models of modified Coulomb friction law and spring - friction elements are determined. For easy application in computing programs used in technical practice and based on linear equations, the equivalent linear stiffness and damping expressions are formulated and analysed in detail. and Obsahuje seznam literatury
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

9. Vibrations of turbine blades bundles model with rubber damping elements

Creator:
Půst, Ladislav and Pešek, Luděk
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
mathematical model, bundle of five blades, rubber damping elements, and eigenmodes
Language:
English
Description:
A detailed analysis of dynamical properties of five-blade-bundle mathematical model was carried out with the aim to investigate how the damping elements made of rubber inserted into slots between blades heads influence the response curves at different distribution of exciting harmonic forces. Viscous-elastic linear Voigt-Kelvin model was used for modeling the rheological properties of damping elements. Constant values of stiffness and damping parameters were supposed at analysis. The orthogonality of excitation forces distribution to the other eigenmodes of blades bundle is applied at insulated selected resonance. and Obsahuje seznam literatury
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public