Analysis of two methods used for ascertaining stability of dynamical systems was carried out on a mathematical model of experimental stand of aerodynamic bearings. It was proofed that method of direct eigenvalue calculation gives practically the same results, which are obtained from the solution of equations of motion by means of integral Runge Kutta procedure. and Obsahuje seznam literatury
Dynamic properties of two similar, parallel, one-sided clamped beams connected by a damping element on their free ends are analytically and numerically investigated. A harmonic motion excites the end of one of these beams. The main attention is given to the ascertaining of response curves deflection shapes of beams and their stresses in roots at different orientations and levels of damping force. and Obsahuje seznam literatury
Electromechanical system with one degree of freedom in mechanical oscillating part and with other degree in rotation a electrical subsystems is investigated by means of numerical solution of derived equations in dimensionless form. The most important nonlinearities are impacts of the main body on the stiff but deformable stop. Other nonlinear effects are introduced into system by the force transformation from unbalance exciter with limited power into the oscillating subsystem and also by nonlinear magnetic flux in the driving electromotor. Presented numerical simulation was focused on the study of the influence of exciting unbalance level on the time histories of oscillations and on phase trajectories. The various responses were shown and discussed in examples. and Obsahuje seznam literatury
This contribution supplements the series of work oriented on active reduction of unacceptable vibrations by means of parametric excitation fulfilling certain conditions. Paper deals with the suppression of undesirable vibration using special parametric excitation fulfilling certain conditions. It is shown that this phenomenon can be used not ony for suppressing the self-excited vibrations or parametric resonances arising outside the region of main resonances in the vicinity of eigenfrequencies as are subharmonic resonances. and Obsahuje seznam literatury
This article presents an overview on series of Conferences and Colloquia on Dynamic of Machines organized in the first place by the Institute of Thermomechanics of Academy of Sciences of Czech Republic. This overview includes scientific meetings from the first Conference held in Liblice Castle in 1958 up to the last Colloquium in 2009. It is an extended paper presented in 2007 and accompanied by the exhibition of Proceedings organized in the frame of Colloquium 'Dynamics of Machines' 2007. and Obsahuje seznam literatury
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
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
A new application of the parametric anti-resonance is discussed. This phenomenon can be used not only for suppressing self-excited vibration or to reduce the externally excited vibration but also to suppressing self-excited vibration or to reduce the externally excited vibration but also to suppress the parametric resonance when certain conditions are met. Another aim is to stimulate further investigations and the practical applications. and Obsahuje seznam literatury
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
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