|
|
Concepts of reducing the forces transmitted between the rigid rotor and its frame based on magnetorheological damping devices
Zapoměl, Jaroslav ; Ferfecki, Petr ; Kozánek, Jan
A usual technological solution how to reduce forces transmitted between the rotor and its stationary part is to apply a flexible suspension with damping devices placed between the rotor and its casing. Optimum performance of the constraint damping elements can be achieved if their damping effect is controllable. As the control depends only on speed of the rotor rotation that does not vary rapidly the semiactive devices based on utilization of the magnetorheological phenomenon can be used for this purpose. Then the damping force is controlled by the change of electric current generating magnetic flux passing through the layer of the magnetorheological lubricant. Three concepts of their arrangement were studied: magnetorheological dampers with only one layer of the magnetorheological liquid and dampers with two separated layers formed by the normal oil and magnetorheological lubricants in the serial and parallel arrangements.
|
|
|
Dynamics of machines 2013
Pešek, Luděk
The aim of the Colloquium was to facilitate the exchange of up to date information and knowledge among specialists in solid mechanics. The main attention was focused on: continuum dynamics, impact and non-linear phenomena, crack propagation, constitutive models, dynamics of linear and non-linear systems, identification, chaos, vibrations, interaction of mechanical systems and fluids, modern computational mechanics and experiments.
|
|
| |
|
| |
|
|
Research of pressure pulsations and vibrations at the turbine 1000 MW
Procházka, Pavel ; Vaněk, František ; Sadílek, J. ; Hodboď, Robert
Experimental research of pressure pulsation with simultaneous measurements of stator and blade vibrations in the L – 1 stage was conducted at the turbine 1000 MW of the nuclear power plant Temelín in 2012. The aim of this work was to find out links and possible sources of increased vibrations of the blades of the 3rd rotor stage during the turbine start-up. The applied methods and used appliances are described in the paper. Observed phenomena are analyzed with focus on the causes of blade vibrations.
|
|
|
Parametric "anti-resonance" for two-mass reverse pendulum system
Tondl, A. ; Pešek, Luděk
This contribution deals with further utilization of the parametric anti-resonance phenomenon based on additional parametric excitation fulfilling special conditions having the damping effect. The anti-resonance be used not only for suppressing self-excited vibrations or parametric resonance or decreasing externally excited resonance vibration of the equilibrium position of the not directly excited sub-system of the autoparametric system when the vibrations of the mentioned sub-system is not desired, e.g. rotating machine with vertical shift or the box with sensitive apparatuses situated on the vibrating floor.
|
|
|
Vibration damping by dry friction with microslips
Půst, Ladislav ; Pešek, Luděk
An experimental set for measurement of dry friction characteristics at vibration relative motion has been developed and used for evaluation of time histories of friction forces at motion with given amplitudes, frequencies and loading normal forces. The dry friction coefficient and contact tangential stiffness of elastic micro-deformation were ascertained by means of new evaluation method with particular orientation to the very small amplitudes of relative motions in contact surfaces, when the friction coefficient goes to the zero and the corresponding hysteretic curve degenerates into a oblique line. All displacements are then elastic micro-deformations without any friction.
|
|
|
Combined linear and non-linear time heteronymous damping in internal dynamics of non-linear parametric systems
Hortel, Milan ; Škuderová, Alena
In the process of the design of high speed planetary gear systems with minimum dimensions and masses are not sufficiently in advance known many of the functional dependencies of parameters such as constant or time heteronomous damping in gear mesh of kinematic pairs, etc. Therefore, it is necessary due to the safety and reliability of these systems that the basic research in this field dealt with this problem deeper both qualitatively and quantitatively, analytically and numerically. The values and functional dependencies, for example of damping parameters of solved systems, are often only estimated. Effects of variations in the size of the estimated parameters from their true values is solved in a wider variation expected ranges, including the impact on the internal dynamics of these systems. In this study are analyzed bifurcation resonance characteristics of relative motion in the gear mesh of system with combined linear and non-linear - quadratic time heteronymous damping on the model of one branch of power flow of pseudoplanetary weakly and strongly non-linear system with six degrees of freedom.
|
|
|
Analytic model of a ball rolling on a spherical surface under harmonic kinematic excitation
Náprstek, Jiří ; Fischer, Cyril
The set of a heavy metallic ball which is rolling freely inside a semi-spherical dish with larger diameter, being fixed to structure, is frequently used as tuned mass damper of vibration. Ratio of both diameters, mass of the rolling ball, quality of contact surfaces and other parameters should correspond with characteristics of the structure. The ball damper is modeled as a non-holonomic system. Hamiltonian functional including an adequate form of the Rayleigh function is formulated in moving coordinates using Euler angles and completed by ancillary constraints via Lagrangian multipliers. Subsequently Lagrangian differential system is carried out. Together with rolling conditions the governing system of seven equations is formulated. Later Lagrangian multipliers character is analyzed and redundant motion components are eliminated. First integrals are derived and main energy balances evaluated together with their physical interpretation.
|
guest ::
